THE ECOLOGICAL IMPACT
OF LAND CLEANUP
AND RESTORATION
REPRINTED - JULY 1993
OFFICE OF RADIATION AND INDOOR AIR
US ENVIRONMENTAL PROTECTION AGENCY
WASHINGTON, DC 20460
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PREFACE
This document was first published in 1978 as EPA Technical
Report 520/3-78-006. It presents the results of work carried out
by the General Electric Company, Tempo Division, under contract
with the Environmental Protection Agency.
The material was developed in support of proposed guidance on
Dose Limits for Persons Exposed to Transuranium Elements in the
General Environment and is intended to provide information useful
for planning of localized remedial actions and for preparation of
Environmental Impact Statements where required. Although written
primarily from the viewpoint of radiation protection, the scope of
the document is sufficiently broad to have widespread applicability
to many other situation where cleanup of residual environmental
contamination may be required.
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ABSTRACT
The basic types of cleanup procedures for removing or deactivating
spilled contamination involve moving people and animals from the affected area
scraping or grading the contaminated soil into windrows, plowing the contamina-
tion under, or digging up the contamination and hauling it away. This report
describes and evaluates these various land-type cleanup effects in terms of
impact of the technique on the environment. The cleanup procedures are listed
in the following table with brief definitions of proposed cleanup actions
Conclusions about the effects of cleanup on the soil, vegetation, and animals
in an area are summarized in the composite effects shown in the following
table as a composite ranking for all the areas studied. The rankings are
numbered from 0 through 5 for each cleanup treatment. Interpretations of
these rankings are as follows:
0 - No measurable change is produced in the ecosystem.
1 - The preferred cleanup because adverse environmental
effects upon recovery and side effects of treatment
are minimal,
2 - A conditionally acceptable treatment because of sig-
nificant impact by the treatment and/or the equipment
upon the area.
3 - Acceptable as a "last resort" cleanup to remove
exceptionally hazardous material while incurring
maximum acceptable impact.
4 - Causes unacceptable damage but can be used as an
interim cleanup if the injury is erased during the
final treatment.
5 - Not applicable to the land type for which it is proposed.
The rankings considered the environmental insult generated during the
cleanup, the physical possibility of restoring the area to its original pro-
ductive state, side effects caused by the equipment needed to perform the
cleanup, the impact upon the environment adjacent to the cleaned up area, and
the social acceptance of the cleanup work. Not all treatments were expected
to be evaluated with all land types; these exceptions are indicated in the
table as being outside the scope of this effort.
The primary criterion for the evaluation of cleanup effects was the suit-
ability of the denuded surface as a medium for plant growth. Establishment of
a vegetative cover before serious wind and water erosion despoiled the site was
considered first and, if revegetation was probable, the time to recover the
initial pre-cleanup productivity was considered next. This is the context in
which the rankings were defined.
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-------
CONTENTS
Abstract
Figures
Tables
Acknowledgments "
INTRODUCTION
Statement of the Problem
Purpose of the Report
Scope of the Report
Literature Base
Study Approach
Impact Evaluation
Use of the Report
Conclusions
PART I - NATURAL ECOSYSTEMS
CHAPTER 1-DESERT
1.1 Overview
1.1.1 Desert Climate
1.1.2
1.1.3
1.1.4
1.2
1.3
1.4
Soils
Topographic Factors
Vegetation
1.1.4.1 Great Basin Desert
Mojave Desert
Sonoran Desert
Chihuahuan Desert
Desert Grassland
1.1.4.2
1.1.4.3
1.1.4.4
1.1.4,5
1.1.5 Desert Succession
Natural Perturbations
1.2.1 Natural Processes
1.2.2 Fire
1.2.3 Climate
Man-Made Perturbations
1.3.1 Fencing
Overgrazing
Mechanical Disturbance
Atomic Test Target Areas
Restoration
Effects of Cleanup Procedures on Deserts
(Treatment 1-1) Chemical Stabilizers
(Treatment 1-2) Clear Cutting Vegetation
(Treatment 1-3) Stumping and Grubbing
(Treatment 1-4) Scraping and Grading
1.3.2
1.3.3
1.3.4
1.3.5
111
xviii
xxi
xxiv
1
1
1
2
5
5
6
7
9
1-1
1-1
1-2
1-4
1-7
1-8
1-8
1-10
1-10
1-11
1-11
1-12
1-13
1-13
1-14
1-17
1-18
1-18
1-19
1-20
1-23
1-26
1-26
1-27
1-30
1-32
1-33
-------
CONTENTS (continued)
(Treatment 1-5)
(Treatment 1-6)
(Treatment 1-7)
(Treatment 1-8)
(Treatment 2-1)
(Treatment 2-2)
(Treatment 2-3)
(Treatment 2-4)
(Treatment 2-5)
(Treatment 2-6)
(Treatment 2-7)
(Treatment 2-8)
1.5
1.6
1.7
1.8
(Treatment 3-1)
' (Treatment 3-2)
(Treatment 3-3)
(Treatment 4-1)
'(Treatment 4-2)
(Treatment 5-0)
(Treatment 6-1)
(Treatment 6-2)
(Treatment 7-0)
Recovery Following Cleanup
1.5.1 Unassisted Succession
1.5.2 Cleanup Recovery Categories
Quantitative Assessment of Cleanup
1.6.1 Impact Assessment
1.6.2 Recovery Assessment
Conclusions
Desert References
Shallow Plowing
Deep Plowing
Soil Cover Less than 25 cm
Soil Cover 25 to 100 cm
Remove Plow Layer
Remove Shallow Root Zone
Scrape and Grade, Mechanically
Stabilize
Remove Plow Layer, Mechanically
Stabilize
Remove Shallow Root Zone, Mechanically
Stabilize
Scrape and Grade,,Chemically
Stabilize
Remove Plow Layer, Chemically
Stabilize
Remove Shallow Root Zone, Chemically
Stabilize
Barriers to Exclude People
Exclude Large Animals
Exclude Large and Small Animals
Asphalt Hard Surface Stabilization
Concrete Hard Surface Stabilization
Application of Sewage Sludge
High Pressure Washing
Flooding
Soil Amendments Added
Impacts
CHAPTER 2-PRAIRIE
2.1 Overview
2.1.1 Tall grass Prairie
2.1.2 Mixedgrass Prairie
2.1.3 Shortgrass Prairie
2.1.4 Other Grasslands
2.2 Natural Perturbations
2.2.1 Drought
2.2.2 Flooding
2.2.3 Fossorial Animals
2.3 Man-Made Perturbations
2.3.1 Close Cropping and Grazing
2.3.2 Compaction
2.3.3 Plowing
1-37
1-37
1-37
1-39
1-39
1-39
1-39
1-40
1-40
1-40
1-41
1-41
1-41
1-41
1-42
1-43
1-44
1-44
1-44
1-44
1-44
1-46
1-46
1-52
1-52
1-53
1-55
1-58
1-60
2-1
2-1
2-1
2-2
2-3
2-3
2-4
2-4
2-5
2-5
2-6
2-6
2-7
2-7
vi
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CONTENTS (continued)
2.4
2.3.4 Natural Succession
2.3.5 Range Improvement
2.3.5.1 Mulches
2.3.5.2 Seeding
2.3.5.3 Shrub Removal
2.3.5.4 Moisture Trapping
Effects of Cleanup Procedures on Prairie
(Treatment 0-1) Natural Rehabilitation
(Treatment 1-1)
(Treatment 1-2)
(Treatment 1-3)
Chemical Stabilization
Clear Cutting Vegetation
Stumping and Grubbing
_ ., Scraping and Grading
(Treatment 1-5) Shallow Plowing
(Treatment 1-6) Deep Plowing
(Treatment 1-4)
(Treatment 1-7)
(Treatment 1-8)
(Treatment 2-1)
(Treatment 2-2)
(Treatment 2-3)
(Treatment 2-4)
(Treatment 2-5)
(Treatment 2-6)
(Treatment 2-7)
(Treatment 2-8)
Soil Cover Less than 25 cm
Soil Cover 25 to 100 cm
Remove Plow Layer
Remove Shallow Root Zone
Remove Scraping and Grading,
Mechanically Stabilize
Remove Plow Layer, Mechanically
Stabilize
Remove Shallow Root Zone, Mechanically
Stabilize
Remove Scraping and Grading,
Chemically Stabilize
Remove Plow Layer, Chemically
Stabilize
Remove Shallow Root Zone, Chemically
Stabilize
Barriers to Exclude People
Exclude Large Animals
Exclude Large and Small Animals
Asphalt Hard Surface Stabilization
Concrete Hard Surface Stabilization,
(Treatment 3-1)
(Treatment 3-2)
(Treatment 3-3)
(Treatment 4-1)
(Treatment 4-2)
2.5 Recovery After Cleanup
2.5.1 Irreversible Changes
2.5.2 Rates of Recovery Following Cleanup
2.5.2.1 First Year Following Cleanup
2.5.2.2 Fifth Year Following Cleanup
2.5.2.3 Tenth Year Following Cleanup
2.5.2.4 Climax
2.6 Quantitative Assessment of Cleanup Impacts
2.6.1 Impact Assessment
2.6.2 Recovery Assessment
2.7 Conclusions
2.8 Prairie References
2-7
2-9
2-9
2-9
2-10
2-10
2-10
2-11
2-11
2-12
2-12
2-13
2-13
2-14
2-14
2-14
2-14
2-15
2-15
2-17
2-17
2-17
2-18
2-18
2-18
2-18
2-19
2-19
2-20
2-21
2-21
2-21
2-22
2-26
2-27
2-28
2-30
2-30
2-31
2-34
2-35
vn
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CONTENTS (continued)
CHAPTER 3-DECIDUOUS FOREST
3.1 Overview
3.1.1 Mixed Mesophytic Forest
3.1.2 Oak-Hickory Forests
3.1.3 Appalachian Oak-Chestnut Forest
3.1.4 Oak-Hickory-Pine Forest
3.1.5 Southern Mixed Forest
3.1.6 Beech-Maple Forest
3.1.7 Maple-Basswood Forest
3.1.8 Hemlock-Hardwood Forest
3.1.9 Theoretical Considerations
3.2 Natural Perturbations
3.2.1 Fire
3.2.2 Primary Successions
3.3 Man-Made Perturbations
3.3.1 Surface Mining
3.3.2 Post-Agricultural Successions
3.3.2.1 Southeastern States
3.3.2.2 Northeastern States
3.3.2.3 Central States
3.4 Cleanup Procedures, Effects on Ecosystems
(Treatment 0-1) Natural Rehabilitation
(Treatment 1-1)
(Treatment 1-2)
(Treatment 1-3)
(Treatment 1-4)
(Treatment 1-5)
(Treatment 1-6)
(Treatment 1-7)
(Treatment 1-8)
(Treatment 2-1)
(Treatment 2-2)
(Treatment 2-3)
(Treatment 2-4)
(Treatment 2-5)
(Treatment 2-6)
(Treatment 2-7)
(Treatment 2-8)
(Treatment 3-1)
(Treatment 3-2)
(Treatment 3-3)
(Treatment 4-1)
(Treatment 4-2)
Chemical Stabilization
Clear Cutting Vegetation
Stumping and Grubbing
Scraping and Grading
Shallow Plowing
Deep Plowing
Soil Cover Less than 25 cm
Soil Cover 25 to 100 cm
Remove Plow Layer
Remove Shallow Root Zone
Remove Scraping and Grading,
Mechanically Stabilize
Remove Plow Layer, Mechanically
Stabilize
Remove Shallow Root Zone, Mechanically
Stabilize
Remove Scraping and Grading,
Chemically Stabilize
Remove Plow Layer, Chemically
Stabilize
Remove Shallow Root Zone, Chemically
Stabilize
Barriers to Exclude People
Exclude Large Animals
Exclude Large and Small Aninals
Asphalt Hard Surface Stabilization
Concrete Hard Surface Stabilization
3-1
3-2
3-2
3-2
3-2
3-3
3-3
3-3
3-4
3-4
3-7
3-7
3-9
3-9
3-9
3-12
3-12
3-14
3-15
3-17
3-17
3-17
3-17
3-18
3-19
3-19
3-19
3-20
3-20
3-21
3-22
3-22
3-23
3-23
3-24
3-24
3-24
3-25
3-25
3-25
3-26
3-26
viii
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CONTENTS (continued)
(Treatment 5-0) Application of Sewage Sludge
(Treatment 6-1) High Pressure Washing (<3 mm)
(Treatment 6-2) Flooding to 30 cm"
(Treatment 7-0) Soil Amendments Added
3,5 Recovery Following Cleanup
3.5.1 Irreversible Changes
3.5.2 Rates of Recovery
3.5.3 Succession Stages Following Cleanup
3.5.3.1 First Year
3.5.3.2 Fifth Year
3.5.3.3 Tenth Year
3.5.3.4 Fiftieth Year
3.5.3.5 100 Years After Cleanup
3.5.3.6 Climax
3.6 Quantitative Assessment of Cleanup Impacts
3.6.1 Impact Assessment
3.6.2 Recovery Assessment
3.7 Conclusions
3.8 Deciduous Forest References
CHAPTER 4-CONIFEROUS FORESTS
4.1 Overview
4.1.1 Boreal Formation
4.1.2 Rocky Mountain Forest Complex
4.1.2.1 Subalpine Spruce-Fir Climax
4.1.2.2 Douglas Fir Climax
4.1.2.3 Ponderosa Pine Climax
4.1.2.4 Pi fion-Juniper Climax
4.1.3 Sierra Nevada Forest Complex
4.1.3.1 Western Slope
4.1.3,2 Eastern Slope
4.1.4 Pacific Conifer Forest
4.1.5 Coniferous Forests Occurring as Sub and Postclimaxes
Natural Perturbations
4.2.1 Fire
4.2.1.1 Unassisted Recovery Sequence
4.2.1.2 Assisted Recovery Sequence
4.2.2 Other Natural Perturbations
Man-Made Perturbations
4.3.1 Clearcutting
4.3.2 Strip Mining
4.3.3 Controlled Burning
Effects of Cleanup Procedures on Coniferous Forests
(Treatment 0-1) Natural Rehabilitation
Chemical Stabilization
Clearcutting Vegetation
Stumping and Grubbing
Scraping and Grading
Shallow Plowing
Deep Plowing
4.2
4.3
4.4
(Treatment 1-1)
(Treatment 1-2)
(Treatment 1-3)
(Treatment 1-4)
(Treatment 1-5)
(Treatment 1-6)
3-26
3-27
3-27
3-27
3-27
3-27
3-27
3-30
3-30
3-31
3-31
3-34
3-34
3-35
3-35
3-36
3-38
3-39
3-41
4-1
4-1
4-4
4-5
4-8
4-8
4-9
4-10
4-11
4-11
4-12
4-13
4-14
4-16
4-16
4-16
4-17
4-19
4-19
4-20
4-20
4-21
4-22
4-22
4-23
4-23
4-28
4-29
4-29
4-30
ix
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CONTENTS (continued)
(Treatment 1-7)
(Treatment 1-8)
(Treatment 2-1)
(Treatment 2-2)
(Treatment 2-3)
(Treatment 2-4)
(Treatment 2-5)
(Treatment 2-6)
(Treatment 2-7)
(Treatment 2-8)
Soil Cover Less than 25 cm
Soil Cover 25 to 100 cm
Remove Plow Layer
Remove Shallow Root Zone
Remove Scraping and Grading,
Mechanically Stabilize
Remove Plow Layer, Mechanically
Stabilize
Remove Shallow Root Zone, Mechanically
Stabilize
Remove Scraping and Grading,
Chemically Stabilize
Remove Plow Layer, Chemically
Stabilize
Remove Shallow Root Zone, Chemically
Stabilize
Barriers to Exclude People
Exclude Large Animals
Exclude Large and Small Animals
Asphalt Hard Surface Stabilization
Concrete Hard Surface Stabilization
Application of Sewage Sludge
(Treatment 3-1)
(Treatment 3-2)
(Treatment 3-3)
(Treatment 4-1)
(Treatment 4-2)
(Treatment 5-0)
4.5 Recovery After Cleanup
4.5.1 Irreversible Changes
4.5.2 Rates of Recovery
4.5.2.1 First Year
4.5.2.2 Fifth Year
4.5.2.3 Fiftieth Year
4.5.2.4 100 Years After Treatment
4.6 Quantitative Assessment of Cleanup Impacts
4.7 Conclusions
4.8 Coniferous Forest References
CHAPTER 5-AEOLIAN MOUNTAIN PEAKS
5.1 Overview
5.1.1 The High Mountain Peak Environment
5.1.2 The Aeolian Life Zone
5.1.2.1 The Nival Phase of the Aeolian Zone
5.1.2.2 The Aquatic Phase of the Aeolian Zone
5.1.2.3 The Terrestrial Phase of the Aeolian Zone
Natural Perturbations
5.2.1 Erosion and Mudflow Phenomena
5.2.2 Avalanches
5.2.3 Landslides
5.2.4 Overgrazing
5.2.5 Recovery
5.2
5.3
5.4
Man-Made Perturbations
5.3.1 Regrading and Replanting
5.3.2 Alternative Techniques
Effects of Cleanup Procedures on Aeolian Mountain Peaks
4-30
4-31
4-32
4-32
4-32
4-34
4-34
4-34
4-34
4-34
4-34
4-34
4-36
4-36
4-36
4-37
4-38
4-38
4-39
4-45
4-48
4-49
4-50
4-52
4-55
4-58
5-1
5-1
5-1
5-5
5-6
5-7
5-7
5-13
5-14
5-15
5-17
5-17
5-17
5-18
5-18
5-19
5-20
-------
CONTENTS (continued)
5.5
5.4.1 Proposed Treatment Techniques
(Treatment 0-1) Natural Rehabilitation
Chemical Stabilization
Clear Cutting Vegetation ("Removal")
Stumping and Grubbing
Scraping and Grading
Shallow Plowing
Deep Plowing
Soil Cover Less than 25 cm
Soil Cover 25 to 100 cm
Remove Plow Layer
Remove Shallow Root Zone
Remove by Scraping and Grading,
Mechanically Stabilize
Remove Plow Layer, Mechanically
Stabilize
Remove Shallow Root Zone, Mechanically
Stabilize
Remove by Scraping and Grading,
Chemically Stabilize
Remove Plow Layer, Chemically
Stabilize
Remove Shallow Root Zone, Chemically
Stabilize
Barriers to Exclude People
Exclude Large Animals
Exclude Large and Small Animals
Asphalt Hard Surface Stabilization
Concrete Hard Surface Stabilization
Application of Sewage Sludge
High Pressure Washing (<3 mm)
Flooding to 30 cm
Soil Amendments Added
5.4.2 Alternative Treatment Techniques
(Treatment 8-1) Snowfences and Wind Barriers
Watershed Control Devices Constructed
Snow and Ice Additives
Removal of Contaminated Snow and Ice
^ - - /
(Treatment 1-1)
(Treatment 1-2)
(Treatment 1-3)
(Treatment 1-4)
(Treatment 1-5)
(Treatment 1-6)
(Treatment 1-7)
(Treatment 1-8)
(Treatment 2-1)
(Treatment 2-2)
(Treatment 2-3)
(Treatment 2-4)
(Treatment 2-5)
(Treatment 2-6)
(Treatment 2-7)
(Treatment 2-8)
i
(Treatment 3-1)
(Treatment 3-2)
(Treatment 3-3)
(Treatment 4-1)
(Treatment 4-2)
(Treatment 5-0)
(Treatment 6-1)
(Treatment 6-2)
(Treatment 7-0)
(Treatment 8-2)
(Treatment 8-3)
(Treatment 8-4)
Recovery After Cleanup
,5.1 Irreversible Changes
5.5.2 Rates of Recovery
5.5.3 Successional Stages
5.5.3.1 First Year
5.5.3.2 Fifth Year
5.5.3.3 Tenth Year
5.6 Quantitative Assessment of Cleanup Impacts
5.7 Conclusions
5.8 Aeolian Mountain Peak References
5-20
5-22
5-22
5-22
5-22
5-22
5-23
5-23
5-23
5-24
5-24
5-24
5-24
5-24
5-25
5-25
5-25
5-25
5-25
5-26
5-26
5-26
5-26
5-26
5-26
5-27
5-27
5-27
5-27
5-27
5-28
5-28
5-29
5-29
5-29
5-30
5-30
5-30
5-30
5-31
5-34
5-36
XI
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CONTENTS (continued)
CHAPTER
6.1
6-TUNDRA
Overview
6.2
6.3
6.4
6.1.4
6.1.5
Geographical Distribution
Environment
Vegetation
6.1.3.1 Arctic Tundra
6.1.3.2 Alpine Tundra
Animal Life
Soils
Natural Perturbations
6.2.1 Fire
6.2.2 Drought
6.2.3 Grazing
Man-Made Perturbations
Effects of Cleanup Procedures on Tundra
(Treatment 0-1) Natural Rehabilitation
(Treatment 1-1)
(Treatment 1-2)
(Treatment 1-3)
(Treatment 1-4)
(Treatment 1-5)
(Treatment 1-6)
(Treatment 1-7)
(Treatment 1-8)
(Treatment 2-1)
(Treatment 2-2)
(Treatment 2-3)
(Treatment 2-4)
(Treatment 2-5)
(Treatment 2-6)
(Treatment 2-7)
(Treatment 2-8)
6.5
(Treatment 3-1)
(Treatment 3-2)
(Treatment 3-3)
(Treatment 4-1)
(Treatment 4-2)
(Treatment 5-0)
(Treatment 6-1)
(Treatment 6-2)
(Treatment 7-0)
Recovery After Cleanup
6.5.1 Irreversible Changes
Chemical Stabilization
Clearcutting Vegetation
Stumping and Grubbing
Scraping and Grading
Shallow Plowing
Deep Plowing
Soil Cover Less than 25 cm
Soil Cover to 25 to 100
Remove Plow Layer
Remove Shallow Root Zone
Remove Scraping and Grading,
Mechanically Stabilize
Remove Plow Layer, Mechanically
Stabilize
Remove Shallow Root Zone, Mechanically
Stabilize
Remove Scraping and Grading,
Chemically Stabilize
Remove Plow Layer, Chemically
Stabilize
Remove Shallow Root Zone, Chemically
Stabilize
Barriers to Exclude People
Exclude Large Animals
Exclude Large and Small Animals
Asphalt Hard Surface Stabilization
Concrete Hard Surface Stabilization
Application of Sewage Sludge
High Pressure Washing
Flooding to 30 cm
Soil Amendments Added
6-1
6-1
6-2
6-2
6-3
6-4
6-10
6-11
6-11
6-16
6-16
6-17
6-17
6-17
6-19
6-20
6-20
6-21
6-21
6-22
6-23
6-23
6-23
6-23
6-23
6-23
6-24
.6-2*
6-24
6-24
6-24
6-24
6-24
6-24
6-25
6-25
6-25
6-25
6-25
6-26
6-26
6-26
6-26
xii
-------
CONTENTS (continued)
6.6
6.7
6.8
CHAPTER
7.1
7.2
7.3
7.4
6.5.2 Rates of Recovery
6.5.3 Succession Stages Following Cleanup
6.5.3.1 First Year
6.5.3.2 Fifth Year
6.5.3.3 Tenth Year
6.5.3.4 Climax
Quantitative Assessment of Cleanup Impacts
Conclusions
Tundra References
7-COASTAL INTER-TIDAL MARSHES
Overview
7.1.1 Occurrence of Coastal Marshes
7.1.2 Related Land Types
Natural Perturbations
Man-Made Perturbations
7.3.1 Impact on Baseline Ecosystem Components
7.3.2 Unassisted Recovery Sequence
Effects of Cleanup Procedures on Coastal Marshes
(Treatment 1-1) Chemical Stabilization
(Treatment 1-2) Clear Cutting Vegetation
(Treatment 1-3) Stumping and Grubbing
(Treatment 1-4) "
(Treatment 1-5)
(Treatment 1-6)
(Treatment 1-7)
(Treatment 1-8)
(Treatment 2-1)
(Treatment 2-2)
(Treatment 2-3)
(Treatment 2-4)
(Treatment 2-5)
(Treatment 2-6)
(Treatment 2-7)
(Treatment 2-8)
(Treatment 3-1)
(Treatment 3-2)
(Treatment 3-3)
(Treatment 4-1)
(Treatment 4-2)
(Treatment 5-0)
(Treatment 6-1)
Scraping and Grading
Shallow Plowing
Deep Plowing
Soil Cover Less than 25 cm
Soil Cover 25 to 100 cm
Remove Plow Layer
Remove Shallow Root Zone
Remove by Scraping and Grading,
Mechanically Stabilize
Remove Plow Layer, Mechanically
Stabilize
Remove Shallow Root Zone, Mechanically
Stabilize
Remove by Scraping and Grading,
Chemically Stabilize
Remove Plow Layer, Chemically
Stabilize
Remove Shallow Root Zone, Chemically
Stabilize
Barriers to Eixclude People
Barriers to Exclude Large Animals
Barriers to Exclude Large and
Small Animals
Asphalt .Hard Surface Stabilization
Concrete Hard Surface Stabilization
Application of Sewage Sludge
High Pressure Washing (<3 mm)
6-26
6-28
6-28
6-28
6-28
6-29
6-29
6-29
6-31
7-1
7-1
7-5
7-5
7-6
7-7
7-7
7-8
7-15
7-16
7-16
7-16
7-19
7-19
7-20
7-20
7-20
7-21
7-21
7-21
7-22
7-22
7-22
7-22
7-22
7-22
7-23
7-23
7-25
7-25
7-25
7r26
xiii
-------
CONTENTS (continued)
(Treatment 6-2) Flooding to 30 cm
(Treatment 7-0) Soil Amendments Added
7.5 Recovery After Cleanup
7.6 Quantitative Assessment of Cleanup Impacts
7.7 Conclusions
7.8 Coastal Inter-Tidal Marsh References
PART II - MANAGED ECOSYSTEMS
CHAPTER 8-AGRICULTURE
8.1 Overview
8.2 Natural Perturbations
8.3 Man-Made Perturbations
8.3.1 Runoff and Fertilization
8.3.2 Soil Compaction
8.3.3 Compaction and Runoff
8.3.4 Infiltration and Crops
8.4 Effects of Cleanup Procedures on Agriculture
(Treatment 0-1)
(Treatment 1-1)
(Treatment 1-2)
(Treatment 1-3)
(Treatment 1-4)
(Treatment 1-5)
(Treatment 1-6)
(Treatment 1-7)
(Treatment 1-8)
(Treatment 2-1)
(Treatment 2-2)
(Treatment 2-3)
(Treatment 2-4)
(Treatment 2-5)
(Treatment 2-6)
(Treatment 2-7)
(Treatment 2-8)
(Treatment 3-1)
(Treatment 3-2)
(Treatment 3-3)
(Treatment 4-1)
(Treatment 4-2)
(Treatment 5-0)
(Treatment 6-1)
Natural Rehabilitation
Chemical Stabilization
Clearcutting Vegetation
Stumping and Grubbing
Scraping and Grading
Shallow Plowing
Deep Plowing
Soil Cover Less than 25 cm
Soil Cover 25 to 100 cm
Remove Plow Layer
Remove Shallow Root Zone
Remove Scraping and Grading,
Mechanically Stabilize
Remove Plow Layer, Mechanically
Stabi1i ze
Remove Shallow Root Zone, Mechanically
Stabilize
Remove Scraping and Grading,
Chemically Stabilize
Remove Plow Layer, Chemically
Stabilize
Remove Shallow Root Zone, Chemically
Stabilize
Barriers to Exclude People
Barriers to Exclude Large Animals
Barriers to Exclude Large and
Small Animals
Asphalt Hard Surface Stabilization
Concrete Hard Surface Stabilization
Application of Sewage Sludge
High Pressure Washing (<3 mm)
7-26
7-26
7-26
7-26
7-33
7-34
8-1
8-1
8-5
8-8
8-10
8-11
8-13
8-14
8-14
8-15
8-16
8-17
8-18
8-18
8-19
8-20
8-20
8-20
8-21
8-21
8-22
8-24
8-24
8-2*
8-25
8-25
8-25
8-25
8-26
8-26
8-27
8-27
8-28
xiv
-------
CONTENTS (continued)
8.5
8.6
8.7
8.8
(Treatment 6-2) Flooding to 30 cm
(Treatment 7-0) Soil Amendments Added
Recovery Following Cleanup
8.5.1 Irreversible Changes
8.5.2 Rates of Recovery
Quantitative Assessment of Cleanup Impacts
Conclusions
Agriculture References
CHAPTER 9-URBAN/SUBURBAN AREAS
9.1 Overview
9.2 Natura.l Perturbations
9.3 Man-Made Perturbations
9.4 Effects of Cleanup Procedures
Lawn, Plant and
(Treatment 0-1)
(Treatment 1-1)
(Treatment 1-2)
(Treatment 1-3)
(Treatment 1-4)
(Treatment 1-5)
(Treatment 1-6)
(Treatment 1-7)
(Treatment 1-8)
(Treatment 2-1)
(Treatment 2-2)
(Treatment 2-3)
(Treatment 2-4)
(Treatment 2-5)
(Treatment 2-6)
(Treatment 2-7)
(Treatment 2-8)
(Treatment 3-1)
(Treatment 3-2)
(Treatment 3-3)
(Treatment 4-1)
(Treatment 4-2)
(Treatment*5-0)
(Treatment 6-1)
(Treatment 6-2)
(Treatment 7-0)
on
cm
cm
__ _.. Urban/Suburban Areas
9.4.1 Lawn, Plant and Soil Area Treatments
Natural Rehabilitation
Chemical Stabilization
Clear Cutting Vegetation
Stumping and Grubbing
Scraping and Grading
Shallow Plowing
Deep Plowing
Soil Cover Less than 25
Soil Cover 25 cm to 100
Remove Plow Layer
Remove Shallow Root Zone
Remove Scraping and Grading,
Mechanically Stabilize
Remove Plow Layer, Mechanically
Stabilize
Remove Shallow Root Zone, Mechanically
Stabilize
Remove Scraping and Grading,
Chemically Stabilize
Remove Plow Layer, Chemically
Stabilize
Remove Shallow Root Zone, Chemically
Stabilize
Barriers to Exclude People
Exclude Large Animals
Exclude Large and Small Animals
Asphalt Hard Surface Stabilization
Concrete Hard Surface Stabilization
Application of Sewage Sludge
High Pressure Washing
Flooding to 30 cm
Soil Amendments Added
9.4.2 Impervious, Artificial Surface Treatments
(Treatment 8-1) Washing with High Pressure Water (>3 mm)
(Treatment 8-2) Vacuuming
8-28
8-28
8-29
8-29
8-29
8-30
8-37
8-38
9-1
9-1
9-4
9-4
9-5
9-8
9-8
9-8
9-8
9-8
9-9
9-9
9-9
9-9
9-9
9-11
9-11
9-11
9-11
9-12
9-12
9-12
9-12
9-12
9-12
9-12
9-12
9-13
9-13
9-13
9-13
9-13
9-13
9-14
9-15
xv
-------
CONTENTS (continued)
(Treatment 8-3) Sweeping
(Treatment 8-4) Mechanized Street Flushing
(Treatment 8-5) Surface Removal Techniques
(Treatment 8-6) Other Removal Methods
(Treatment 8-7) Containment
9.5 Recovery After Cleanup
9.6 Quantitative Assessment of Cleanup Impacts
9.7 Conclusions
9.8 Urban/Suburban Land Areas References
PART III - WILDLIFE
CHAPTER 10 -WILDLIFE
10.1 Overview
10.2 Effects on Birds
10.2.1 Short-Term Effects
10.2.2 Long-Term Effects
10.2.2.1 Deserts
10.2.2.2 Prairies
10
10
10.
2.2.3 Deciduous Forests
2.2.4 Coniferous Forests
10.2.2.5 Aeolian Mountain Peaks
10.2.2.6 Tundra Areas
10.2.2.7 Coastal Inter-Tidal Marshlands
.2.2.7
.2.3 Land Uses
10.2.3.1 Agricultural Areas
10.2.3.2 Suburban Areas
10.3 Effects on Mammals
10.3.1 Short-Term Effects
10.3.1.1 Large Carnivores
10.3.1.2 Medium-Sized Carnivores
,3.1.3 Small Carnivores
10.
10.
10,
10,
3.1.4 Large Herbivores
3.1.5 Small Herbivores
3.1.6 Large Omnivores
10.3.1.7 Small Omnivores
10.3.1.8 Insectivores
10.3.1.9 Flying Mammals
10.3.2 Long-Term Effects
10.3.2.1 Large Carnivores
10.3.2.2 Medium-Sized Carnivores
10.3.2.3 Small Carnivores
10.3.2.4 Large Herbivores
10.3.2.5 Small Herbivores
10.3.2.6 Large Omnivores
10.3.2.7 Small Omnivores
10.3.2.8 Insectivores
10.3.2.9 Flying Mammals
10.3.3 Land Types
10.3.3.1 Deserts
9-16
9-16
9-17
9-17
9-17
9-18
9-18
9-21
9-21
10-1
10-1
10-8
10-8
10-10
10-12
10-14
10-15
10-15
10-16
10-16
10-17
10-18
10-18
10-19
10-20
10-20
10-21
10-21
10-22
10-22
10-22
10-23
10-25
10-25
10-25
10-26
10-26
10-26
10-27
10-27
10-27
10-28
10-28
10-29
10-29
10-29
10-31
xvi
-------
CONTENTS (continued)
10.3.3.2 Prairies
10.3.3.3 Deciduous Forests
10.3.3.4 Coniferous Forests
10.3.3.5 Tundra Areas
10.3.3.6 Coastal Inter-Tidal Marshlands
10,3.4 Land Uses
10.3.4.1 Agricultural Areas
10.3.4.2 Suburban Areas
10.4 Conclusions
10.5 Wildlife References
PART IV - APPENDICES
APPENDIX A-STABILIZERS
A.I Introduction
A.2 Types of Stabilizers
A.2.1 Chemical
A.2.2 Mechanical
A.2.3 Physical
A.2.4 Chemical with Mechanical Characteristics
A.3 Stabilizer Groupings
A.4 Ratings of Stabilizer Groupings
A.4.1 Application
A.4.2 Durability
A.4.3 Vegetation Recovery
A.5 Land Types and Land Use Classes
A.6 Appendix A References
APPENDIX B-IMPACT ASSESSMENT
B.I Introduction
B.2 Derivation of Recovery Index from Successional Sere
B.3 Ranking of Disturbance from Cleanup Treatments
B.4 Recovery Index Number Assignment
B.5 Appendix B References
APPENDIX C-LAND TYPES
APPENDIX D-CLEANUP TREATMENTS
APPENDIX E-GLOSSARY
10-31
10-32
10-32
10-32
10-33
10-33
10-34
10-35
10-39
A-l
A-l
A-l
A-l
A-l
A-3
A-3
A-4
A-5
A-5
A-6
A-6
A-7
A-7
B-l
B-l
B-l
B-4
B-5
B-ll
C-l
D-l
E-l
xvi i
-------
FIGURES
Number Page
1-1 The North American Desert and its subdivisions. 1-9
1-2 Great Basin Desert roadway unused for 15 years. 1-22
1-3 Mojave Desert roadway unused for 17 years. 1-22
1-4 Great Basin Desert 11 years after blading and forming windrows. 1-24
1-5 Mojave Desert. An unintended water catchment basin in a
disturbed area. 1-24
1-6 Mojave Desert. Larrea growing in compacted area alongside
asphalt roadway. 1-25
1-7 Mojave Desert. The effect of increased moisture from roadside
cut on Larrea growth. 1-28
1-8 Great Basin Desert. A 2 ha rectangular plot 11 years after
blading. 1-34
1-9 Great Basin Desert 11 years after blading. 1-34
1-10 Great Basin Desert. Demarcation line between land bladed
11 years ago (right) and non-bladed land (left). 1-35
1-11 Great Basin Desert. Area in foreground and right was bladed
11 years prior to the photograph. 1-35
1-12 Great Basin Desert 17 years after application of water to
reduce dust followed by blading. 1-36
1-13 Great Basin Desert recovery 17 years after blading. 1-36
1-14 Great Basin Desert 17 years after plowing. 1-38
1-15 Great Basin Desert. Foreground first treated with hot,
rapid-cure road oil stabilizer, then scraped. 1-45
1-16 Soil 17 years after application of a hot rapid-cure road oil
stabilizer. 1-45
1-17 Sequence of ecologic recovery following cleanup. 1-47
1-18 Recovery sequence following shallow plowing and clearcutting
vegetation. 1-48
1-19 Sequence of ecologic recovery following cleanup. 1-49
1-20 Sequence of ecologic recovery following cleanup. 1-50
2-1 Natural recovery and recovery with reseeding of prairie. 2-23
xviii
-------
FIGURES (continued)
Number^
2-2
2-3
3-1
3-2
3-3
4-1
4-2
4-3
4-4
4-5
4-6
4-7
5-1
5-2
5-3
6-1
7-1
7-2
7-3
7-4
7-5
Time course of change after mowing (1-2) and stumping and
grubbing (1-3) of woody component of prairie.
Recovery of prairie following mechanical soil stabilization
and response to the erection of fencing.
Natural recovery (0-1) and generalized typical reclamation
of deciduous forest following cleanup.
Recovery of deciduous forest following clear cutting (1-2)
and stumping and grubbing (1-3).
Recovery of deciduous forest following hard surface
stabilization.
Natural forest vegetation of the United States.
Vegetation chart for the Santa Catalina Mountains, southeastern
Arizona.
Sequence of ecological recovery following cleanup.
Sequence of ecological recovery following cleanup.
Sequence of ecological recovery following cleanup.
Decrease in runoff following clearcutting coniferous forests.
Clearcutting the whole stand, with reproduction secured by
seed disseminated from seed trees located outside the cut
stand.
Alpine and aeolian regions of the world.
Alpine-aeolian zonation in the eastern Himalaya
Diurnal sun/shade temperature ranges in air and subsurface
soil at 15,500 feet.
A word model illustrating the sequence of events in the
recovery of damaged arctic tundra vegetation.
Diagram of the wetland classification hierarchy for the
estuarine ecological system to the order level.
A typical effects linkage shows the disturbance web and
environmental impacts of soil removal.
Recovery of coastal inter-tidal marsh following chemical
soil stabilization and application of shallow soil cover
Recovery of coastal inter-tidal marsh following vegetation
removal and shallow layer soil removal.
Response of coastal inter-tidal marsh to the erection of
fencing.
Page
2-24
2-25
3-28
3-32
3-33
4-3
4-7
4-42
4-43
4-44
4-46
4-48
5-3
5-4
5-9
6-27
7-4
7-11
7-27
7-28
7-29
xix
-------
Number
8-1
8-2
8-3
8-4
B-l
FIGURES (continued)
Indigenous vegetation zones of the conterminous United States.
Surface soil moisture-wind velocity soil loss factor as a
percent of soil loss at Garden City, Kansas.
Rainfall erosivity index, based on maximum 30-minute intensity,
from an average of annual maximums.
Idealized effective precipitation, vegetation, and sediment
yield on west to east transect.
Example of times for recovery from cleanup in coniferous
forest by natural and managed rehabilitation.
Page
8-3
8-6
8-7
8-8
B-3
xx
-------
TABLES
Number
1-1
2-1
3-1
3-2
4-1
4-2
4-3
4-4
4-5
4-6
4-7
5-1
5-2
6-1
6-2
6-3
6-4
7-1
7-2
7-3
Estimates of the years to recover productivity after application
of the 'various cleanup procedures.
Predicted recovery index in prairie for cleanup treatments.
Parameter trends during deciduous forest succession.
Predicted recovery index in deciduous forest for cleanup
treatments.
Measurements on forest clearings.
Average possible depth of compaction to 10 percent soil voids.
Major forest types of the United States.
Approximate age of representative coniferous forests where
number of trees per acre is reduced by suppression.
Height of dominants in a fully stocked stand at 100 years--
good to medium site fully stocked.
Approximate basal area (m2/ha) of representative conifer
speciesgood to medium site, fully stocked.
Recovery index in coniferous forest for various cleanup
treatments.
Movement of mountain detritus within measured mudflows as
examples of erosion.
Estimates of the years to reach recovery after various cleanup
treatments.
Comparison of arctic and alpine environments and vegetation.
Representative poorly drained tundra soil.
Representative well drained tundra soil.
Change in conditions caused by seismic lines and winter roads
with paired control plots in 1970.
Net primary production and plant biomass for major ecosystems
and for the earth's surface.
Effects of ditching a Delaware tidewater marsh on the aquatic
invertebrate populations.
Effects of denuding and/or soil removal on physical and
chemical characteristics of marshlands.
Page
1-54
2-32
3-5
3-37
4-25
4-33
4-40
4-49
4-51
4-51
4-54
5-16
5-33
6-12
6-14
6-15
6-18
7-2
7-9
7-13
xx i
-------
TABLES (continued)
Number
7-4 Effects of soil removal and placement of dredge spoil in
marshlands-
7-5 Predicted years to reestablish precleanup marshes.
8-1 Relationship between annual precipitation, species composition,
and moisture consumption, Rocky Mountains to Missouri transect
of prairie.
8-2 Effectiveness of ground cover in soil erosion loss at construc-
tion sites in deciduous forest zones.
8-3 Control systems and relative effectiveness.
8-4 Commercial crop species in managed ecosystems.
8-5 Rooting depths of agricultural crops in fertile, deep, well
drained soils.
8-6 Predicted recovery index of irrigated desert agriculture for
cleanup treatments.
8-7 Predicted recovery index of agricultural lands in grasslands
for cleanup treatments.
8-8 Predicted recovery index of agricultural lands in forests
for cleanup treatments.
9-1 Relative rating of environmental impact of treatments on a
scale of 0 (no impact) to 100 (greatest impact).
10-1 Examples of bird species impacted by maximum disturbance to
specified types and sizes of land areas.
10-2 Examples of small herbivorous mammals impacted by maximum
disturbance to specified types and sizes of land areas.
10-3 Examples of mammals other than small herbivores impacted by
maximum disturbances to specified types and sizes of land
areas.
10-4 Relative impacts of land cleanup treatments on wildlife
following maximum possible land disturbance.
10-5 Relative time for recovery of wildlife following maximum
disturbance to land and cleanup treatment.
A-l Ratings of individual stabilizers for use in different land
types.
A-2 Manufacturer and application information for soil stabilizers.
B-l Hypothetical forest sere.
B-2 Hypothetical grassland sere.
B-3 Evaluation of the effects of cleanup procedures.
Page
7-15
7-31
8-4
8-9
8-10
8-12
8-12
8-34
8-35
8-36
9-19
10-13
10-24
10-30
10-36
10-38
A-2
A-8
B-2
B-2
B-6
xxi i
-------
TABLES (continued)
Number
B-4
B-5
B-6
Years estimated for hypothetical ecosystem to reach climax
after the indicated cleanup.
Hypothetical coniferous sere as represented by the development
of a Spruce-hemlock forest on mineral soil exposed by glacial
retreat.
Recovery indexes for cleanup of hypothetical coniferous
forest.
Page
B-7
B-9
B-10
xxi i i
-------
ACKNOWLEDGMENTS
This report was written as a collaborative effort among the Chapter authors
and project participants. The principal authors are listed alphabetically, in
reverse order. They are:
Dr. John F. Thames University of Arizona, Tucson, Arizona
Richard H. Rowland - GE-TEMPO, Santa Barbara, California
Dr. James C. McBrayer - University of Michigan (now at Oak Ridge,
Tenn.)
Dr. Howard A. Hawthorne GETEMPO, Santa Barbara, California
James C. Johnson Moss § Johnson Associates, Springfield, Mo.
Kenneth E. Gould - GE -TEMPO, Santa Barbara, California
Dr. Lome G. Everett - GE-TEMPO, Santa Barbara, California
F. Stephen Dobson GETEMPO, Santa Barbara, California (now
at University of Michigan)
Project participants provided the support essential for acquiring reference
materials, supporting documents and ran down those elusive half-documented
citations so well remembered almost. These supporters included Dr. Tika Verma,
Gerald Harwood, Dr. Guenton Slawson, Rosalie Oren, Gregory Mohr, Susan Neighbors,
and Evelyn McDonald.
xxiv
-------
INTRODUCTION
STATEMENT OF THE PROBLEM
In the industrialized development and commerce of today's technological
society a variety of goods are transported by land, sea, and air. Among
these goods in transit at any particular instant are some which are toxic or
injurious to man coining into direct or indirect contact with them. Indirect
contact includes drinking contaminated groundwater, consumption of plants
that absorbed contamination from soil, and using dairy products or meat from
contaminated animals.
Contaminating accidents may also originate when industrial processes
malfunction. These include explosions at chemical process plants, inadvertent
releases by plant operators, and a variety of other dumps or leaks.
The frequency of contaminating accidents has increased yearly until they
have become an almost daily event. In most cases, the contaminant is spread
by natural forces and human traffic during evacuation of the residents. By
the time the contaminant is identified and the zone of contamination delineated,
the contaminant may have penetrated environmental materials and decontamina-
tion may be required. The methods of decontamination are numerous and varied.
PURPOSE OF THE REPORT
This report is concerned with the ecological impacts of specific cleanup
treatments on the land where they are carried out. The report provides
guidance to rational selection among the cleanup procedures likely to be sug-
gested by State, Federal or local government officials, industrial representa-
tives of the entity responsible for the contaminating accident, concerned
citizens' groups, or local environmental managers called in for their expertise.
The priorities of these groups are most likely to be divergent and emotionally
intense under the stress of immediate, local, present danger.
-------
This report is intended to present the best unbiased, neutral estimate
of how local environments will be changed by specific common cleanup treat-
ments, the relative magnitude of the changes they may cause, and their dura-
tion.
Local conditions have the greatest force in determining how interrelated
environmental actions occur. Therefore, the cleanup treatment to be used at a
given site must be decided upon with input from local geologists, foresters,
soil scientists, agronomists, botanists, dairymen, animal husbandmen, zoologists:
or other professionals intimately acquainted with the contaminated area.
SCOPE OF THE REPORT
This report provides two classes of generic data that may be helpful in
deciding what steps should be taken when contamination occurs.
A chapter is devoted to each of seven land types and two managed eco-
systems in the United States. Generic descriptions are given in Part I for
the seven land types and in Part II for the managed ecosystems of agricultural
lands and urban/suburban areas. The vegetation of the seven land types is
described in detail with brief descriptions of their climate and upper soil
profile. The history of ecosystem recovery from natural and man-made
catastrophes is reviewed as a guide to predicting how specific cleanup treat-
ments will affect vegetative recovery.
The second class of information is the generic data arising from descrip-
tions of the effects each of 24 specified cleanup treatments has upon the
soils and vegetation in the affected ecosystems. This information includes
a recovery scenario, quantitative assessment of cleanup impacts, and citing
the best and worst treatments for each land type.
The purpose of the descriptions is to provide a general framework for
coordinating information from which to predict both the short-term effects of
cleanup and resultant long-term changes. Different plants succeed in different
land types but all the plants lack a means of avoiding cleanup trauma. What-
ever cleanup treatment is used will rearrange some of the soils and damage
most of the plants in a heavily contaminated area. Land types and cleanup
-------
treatments were indicated by the EPA tp be the items of major interest, and
specific biota of lower level interest. Thus,.defining the ways in which the
soil-plant web subsequently develops over time after injury is the main thrust
in the quantitative assessments.
After several attempts to describe fauna.], displacement and recoloniza-
tion after cleanup in separate ecosystems it became obvious that excessive
redundancy lay along that approach, in that animal families are adaptable to
several ecosystems. To escape such redundancy, the major faunal groups are
described and predictions made of their response in each disturbed ecosystem,
and each managed land type, where they occur naturally. Part III presents
material on two divisions of animal wildlife, the birds and the mammals.
Animal families cross land types in the same context that cleanup treatments
cross land types in Parts I and II of the report. Evaluation of the ecologi-
cal impact of cleanup treatments was confined to mammals and birds. Ecological
impact is defined as the reaction of a population to disturbance of their
habitat by cleanup. The reactions considered were those large enough to be
measured quantitatively under field conditions. The population attributes
considered suitable for monitoring to define changes in the population were
size (in numbers of individuals) and/or alterations in the numbers of species
present in the area of concern. These attributes of populations were taken
as representative of habitat stability for evaluating cleanup effects.
The critical component in population recovery of wildlife is the restora-
tion of vegetative species suitable for the wildlife. The impact assessment
tables presented in the chapters are based upon best estimates for vegetative
recovery times, or productivity changes.
Almost any spot in the United States could be involved in a contaminant
spill from some source. The seven natural land types chosen represent most
of the United States. The land area of the United States, including Alaska
and Hawaii, totals approximately 10,900,000 km2 of which approximately 240,000
km2 are measured as inland waters. The area not covered by water (approximately
10,660 km2) can be measured as approximately 1,068,770,000 hectares, excluding
public lands, and can be subdivided into the land types shown below. The
-------
percentage breakdown of the seven natural ecosystems and the two managed eco-
systems follows (note that the land-use class of ecosystems overlaps the
natural ecosystems):
Chapter
1
2
3
4
5
6
7
8
9
Land Type
NATURAL ECOSYSTEMS
Desert
Prairie
Deciduous Forest
Coniferous forest
Mountain
Tundra
Coastal Inter- tidal
LAND-USE CLASSES
Agriculture
Urban/ suburban
Total land
surface
(percent)
0.4
49.8
28.9
7.4
8.7
4.4
0.3
45.4
7.7
hectares
4,168,000
532,567,000
309,302,000
78,875,000
93,090,000
47,133,000
3,634,000
485,328,000
82,509,000
The areas examined for cleanup range from a hectare (the size of a
country home) to approximately 4 sections of land, which is not large for a
typical dryland grain farm but is approximately the mean area of a county.
2 2
In metric terms, these areas are 0.01 km and 10 km , respectively. Inter-
2 2
mediate areas 0.10 km and 1.0 km are also addressed.
The time scales for which cleanup impacts are defined range froa short
term (a few years) to those times when the cleanup is no longer visible
(hundreds of years). An arbitrary cutoff point at 100 years was imposed in
determining whether a treatment was acceptable. If more than a century is
required for recovery, the treatment is considered unacceptable.
-------
LITERATURE BASE , .
More than 400 publications are cited in the report and approximately
3,500 others were retained for inspection and discarded. Personal contacts
with other professionals in the areas addressed were made freely. The pre-
ferred data base is included in this report.
STUDY APPROACH
The assembled study team was comprised of professional ecologists actively
engaged in field work in the land areas to which they were assigned for this
project. All were familiar with environmental impact assessment methodology
and the professional literature in their fields.
The ecologist constructs a mental model of the ecosystem climate, geology,
soils, vegetation, and animal forms and predicts the ecological impact of
cleanup operations. Published observations are reviewed to develop an outline
of the ecological boundaries of the ecosystem developed on the land type being
studied. When published literature was inadequate or absent, personal
experience was used to predict the impact of cleanup treatments on the eco-
system being described. The impact predictions; in Sections 4 and 5 of each
chapter represent a blend of the published data and personal experience. The
predicted onset of recovery appears in Section 6 of each chapter and presents
the quantitative assessment for the impact forecasts in Section 4.
Contamination cleanup has been postulated in this report to occur only
in land type tracts that support recognized and. developed ecosystems where
recovery following cleanup progresses along secondary succession, rather than
ecosystem development by primary succession (new substrate occupied, such as
earthquake uplift scarps).
In considering the sequence in which cleanup treatments should be addressed,
it became obvious that the intensity of environmental impact of a specified
cleanup treatment varied from land type.to land type; e.g., surface grading a
shallow soil layer on grassland was less disruptive than putting the same
depth and width through*a forest. Arbitrarily, a uniform sequence and presenta-
tion of cleanup treatments was maintained throughout the report for the sake
-------
of continuity. Those persons interested in following a specific treatment
through all land types are advantaged by this methodology, hopefully with
little disadvantage to those persons intent on examining ecologic impacts'
within particular land types.
Cleanup treatment impacts were ranked across all land types according to
the gross environmental disturbance they would generate. The disturbance was
translated into "median years-to-recover," presented in relative times to
recovery (recovery indexes), and tabulated in Section 6 of each chapter.
Details of these derivations are given in Appendix B. ^
The endpoint of recovery from cleanup for the prairie, deciduous forest,
and coniferous forest is ecological: the reestablishment (succession) of the
original species of plants and animals at the pre-contamination productivity
(biomass). Six of the chapters deal with ecosystems which do not have identi-
fiable succession and a different concept of endpoint is used in those chapters.
The four chapters of desert, mountain, tundra, and marshes use "years-to-recovery"
of their pre-contamination productivity (biomass) as the terminal point of
rehabilitation. In the managed ecosystems of Chapters 8 and 9, the recovery
endpoints are determined by economic productivity and public acceptance, since
physical recovery can be expedited via use of machinery. The concept of
ecological rehabilitation is inappropriate in these managed ecosystems because
they lack the attributes of succession.
IMPACT EVALUATION
The equipment projected to be used for cleanup was limited to that operated
by small .-contractors or to farm machinery. The technical evaluation steps, are
shown in Appendix B as a sequence of steps. Where data were sparse for an eco-
system, the author integrated his field experience with published data to
construct the tables prepared for individual chapters.
Idealized trend curves were developed for Section 5 in many ecosystem
chapters to illustrate the time course of recovery to full productivity for
some of the descriptive ecosystem parameters. The ordinates are without units
either because they have no dimensions (e.g., homeostasis) or they are broad
generalizations' over an array of heterogeneous sites. Representative types
-------
of cleanup treatments were selected for the illustrations to indicate the
variety of parameters common to particular ecosystems.
USE OF THE REPORT
The report is subdivided into 3 Parts and 5 Appendices. In Part I seven
natural ecosystems and some of their natural derivations are defined. Part II
presents managed ecosystems which are imposed on natural ecosystems and are no
longer bound by the initial native ecosystem balances. Part III deals with
avian and mammalian wildlife displaced by cleanup. Appendix A summarizes
judgments of stabilizer chemicals and their application to various .land types.
The methodology used to derive recovery indices for those ecosystems having
easily recognizable successions is presented in Appendix B. Appendices C,
D, and E, respectively, give definitions of the land types studied, cleanup
treatments considered, and a glossary of terms.
Each chapter in Parts I and II is divided into seven sections. The first
three sections give ecologic data sources used in evaluating the cleanup impacts,
In Sections 2 and 3 the ecological basis is given for the judgments utilized
in Sections 4, 5, 6, and 7.
Each cleanup treatment is defined in Appendix D and the impact of each is
defined in Section 4. Section 5 gives a brief scenario of how the ecosystem
is envisioned to change between cleanup and the time at which no further
changes are measurable within present detection instrument capabilities.
Quantitative assessments of the magnitude of cleanup impact are made, recovery
time predicted, and the effects of using the cleanup treatment on larger areas
evaluated. In Section 7, the cleanup treatments that are best suited to the
ecosystem are named, as are those which are inappropriate.
Agricultural uses of ecosystems modify the basic characteristics beyond
the capabilities of native forces to change them on a short-term basis. The
modified ecosystems are evaluated in Chapter 8 separately from their parent
ecosystems. Urban/suburban landscapes also bear few recognizable imprints of
their ecosystem origins and are described in Chapter 9 as a unit of managed
ecosystems.
-------
For nonecologists who desire an accurate but direct presentation of the
essence of ecology, the paperback book, "Communities and Ecosystems," by R. H.
Whittaker, is recommended. In general, the ecosystem is viewed as following
a definite sequence of recovery with time that is predictable, called succes-
sion. As the cleaned up ecosystem enters into natural recovery, the initial
small, short-lived invader species is gradually replaced by long-lived and
larger species which tend to exert more and more control over their surround-
ings. An example is the high-himidity understory of park-like dimensions
which has developed under beech-sugar maple in the deciduous forest zones.
The collective steps in recovery which follow one another are called the sere
and its use in this report is illustrated in Appendix B. Formal classical
ecologists will doubtless object to this abbreviated presentation on the grounds
that it is "applied ecology."
This report was written to summarize what is known and published in tech-
nical journals, books, and reports about how cleanup affects the environment.
Unfortunately, the published data fall far, far short of being continuous in
both time and in the consecutive details of recovery. References are cited
where information is derived from the literature; if no reference is cited,
the information is the author's own projection of the recovery after cleanup
is completed.
The ecosystems in Part I are described in terms of recovery from cleanup
without additional interference or assistance by man. The kinds of assistance
that are appropriate to perform on three of the ecosystems are collected into
the Agriculture chapter in Part II because these are the land types that produce
the commercial foods and fiber at the greatest rates.* The reclamation pro-
cesses that are appropriate after plowingirrigation, reseeding, transplant-
ing, fertilizing, contour tilling, and harvestingare widespread management
practices of agriculture. These are presented in Chapter 8 only to a limited
degree since this report deals with cleanup impactsnot with impact erasure.
Discussion of these management practices within ecosystem chapters has been
restricted to special cases that are unique to natural systems.
*These three land types are desert (Chapter 1), prairie (Chapter 2), and
deciduous forest (Chapter 3).
-------
CONCLUSIONS
Cursory inspection of the conclusions sections of the chapters shows
that generalization and condensation to produce a single conclusion for the
report is not effective. The most disruptive technique was concluded to be
paving over a compacted subgrade. However, estimates of the time for this to
be weathered and assimilated differ among ecosystems. The general conclusion
about ecosystems was that succession was relatively unchanged by a variety of
techniques that assisted in early and rapid revegetation. Mulches, stabilizers,
plowing, and fertilizers were very effective in reintroducing new growth but
the particular ecosystem controlled which species would succeed into climax.
Plantings of hardwoods in grasslands or coniferous ecosystems would have no
effect on the time to climax or eventual climax: species, although grasses are
most likely to provide early cover in any of the widespread ecosystems.
This report has addressed the impacts of particular cleanup techniques on
specified ecosystems but other areas of study remain. The effectiveness of
cleanup techniques in removing or stabilizing contamination needs to be addressed.
The greatest need is the Development of a methodology to quantify (into monetary
terms) the information collected on environmental impact.
-------
PART I
NATURAL ECOSYSTEMS
CHAPTER 1, DESERTS
CHAPTER 2, PRAIRIES
CHAPTER 3, DECIDUOUS FORESTS
CHAPTER 4, CONIFEROUS FORESTS
CHAPTER 5, AEOLIAN MOUNTAIN PEAKS
CHAPTERS, TUNDRAS
CHAPTER 7, COASTAL INTER-TIDAL MARSHES
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CHAPTER 1
DESERT
1.1 OVERVIEW
There is little accord among scientists as to what constitutes a desert.
It is generally agreed that sparse to absent vegetation due to little rainfall
is the distinguishing feature, but where some scientists limit the definition
of desert to areas receiving less than 50 mm of rainfall annually, others
include regions with 360 nun of annual rain, or even more. In addition, it is
recognized that the rainfall amount alone is riot the primary determinant of des-
ert type, but that seasonal moisture fluctuation, temperature, and edaphic fac-
tors are also important. For example, the polar regions are true deserts because
they lack vegetation and exhibit low levels of atmospheric water vapor. There
are also regions of the world which receive in excess of 300 mm of annual
precipitation but are dry, barren and relatively devoid of vegetation. Such
regions are termed edaphic deserts because the physical cause of aridity is
in the nature of the porous surface soil which allows moisture penetration
at a rate too rapid to permit plant sustenance regardless of the amount of
rain that may fall.
The focus in this discussion is on the desert of North America, specifi-
cally the desert of the United States. This desert is a large irregular belt
on the western side of the continent covering about 940,000 square kilometers
from mid-Idaho to Northern Mexico and roughly corresponding to the rain
shadowed intermontane region between the coast ranges and the Rocky Mountains.
It includes major parts of the states of Arizona, Nevada, Utah, and lesser
parts of California, Colorado, Idaho, New Mexico, Oregon, Texas, and Wyoming.
The physical geography and human utilization of the region exhibit great
internal variety, but its overall aridity associated with an excess of evapora-
tion over precipitation, high percentage of sunshine, great temperature extremes,
high diurnal air temperature, low atmospheric humidity, frequent winds and a
predominance of eroded landscapes give it an unquestioned unity. In general,
-------
the region is characterized by rainfalls less than 250 mm per year. In these
areas the environmental gradients are altitudinal gradients, where temperature
decreases and precipitation-increases with elevation. Desert communities occupy
the lowest, driest areas and juniper and pinon-juniper woodlands are on the
higher more mesic regions. The eastern and northern boundaries merge into
grassland prairie. An intermediate land type, the desert grassland, will also
be briefly discussed.
In this report, areas receiving 250 mm or less of rain per year will be
classed as desert. The peripheral desert grasslands receiving somewhat greater
annual moisture will be called arid areas. This is not an arbitrary classifica-
tion but rather one based on the requirement for unassisted revegetation.
Moisture is the dominant factor in vegetation growth and it is generally con-
ceded that once relatively large areas of vegetation have been destroyed, about
250 mm of rainfall per year is the minimum needed for revegetation without
, . . . 39,51,60
supplemental irrigation.
In the discussion below are considered the climatic, edaphic and topographic
features which explain a desert, and the vegetative factors which characterize
it. The goal of this summary is to form a basis for understanding the effects
produced by natural and anthropogenic fman-made) environmental perturbations.
1.1.1 Desert Climate
Geographers have attempted to classify desert types by climates, usually
in terms of precipitation and temperature and their seasonal variation. The
basis for the most widely used classification scheme is the Koppen system which
is based on distribution of vegetation. Vegetation is sensitive to tempera-
ture and precipitation and tends to reflect these variables in a general way.
Because aridity, the distinguishing feature of desert areas, is a measure of
dryness, an index based on water balance of an area would be superior to the
Koppen system for a climatic analysis. Meigs?9 building on the indices developed
by Thornthwate which were closely reflective of water balance considerations,
formulated a classification scheme which includes a more explicit, appreciation
of the role of evaporation, storage of moisture in the soil and the seasonal
variability of precipitation. The Meigs classification uses season of rain-
fall, maximum temperature of the hottest month and minimum temperature of the
coldest month to differentiate arid areas.
1-2
-------
Based on Meigs1 considerations of climate, the American Desert can be
divided into four regional districts.* The northernmost of these, the Great
Basin, has cool or cold winters, frequent snowfall and annual precipitation
ranging from 100 to 220 mm of which only about 40 percent falls in the summer
months. In the southern part are the hot deserts: the Mojave, with winter
rains; Sonoran, with summer and winter rains;; and Chihuahuan, with summer rains.
The Chichuahuan is somewhat isolated but the other three lie in a continuous
series.
In general,...the temperature of the North American desert increases toward
the south while total precipitation decreases. In any given latitude, precipi-
tation increases both east and west of about the 115° meridian. The frequency
and amount of precipitation vary directly as a function,of elevation with ele-
vation accounting for about 80 percent of the variance in rainfall statistics.
The southwest corner is the hottest, driest desert area.
A curve of precipitation amount plotted against time of year for desert
areas is characteristically bimodal, with peaks in the winter and summer. The
relative dominance of one peak or the other has profound influence on the ecol-
ogy of the areas. Orographic barriers are largely responsible for affecting
the seasonal distribution of rainfall in the cool Great Basin desert. This area
lies in the zone of westerly cyclonic storms but much of the moisture in these
storms is extracted by the western boundary mountains. These storms bring much
of the annual precipitation during the winter and early spring months. In the
hot deserts to the south, two major climatic influences cause different sea-
sonal patterns of rainfall. In the eastern part, the Chihuahuan and to a lesser
extent the eastern Sonoran, the major rain is during the summer. This summer
rain results from a seasonal shift in global weather patterns which cause moist
air from the Gulf of Mexico to be drawn over the area. Convective precipitation
originates in this moist air mass. The western extent of this effect is about
the Arizona-California border. To the west of this line, the Mojave receives
winter rain from frontal systems of the cyclonic storms from the west or north.
Only rarely does summer rain, usually from moist air from the Gulf of California,
fall in this area. ThevMojave ^is the driest of the areas, with some locations
reporting only 50 mm of rain a year. As a rule, the lower annual average rain-
falls are associated with higher variance from, the average. , .
*The nomenclature for the desert areas is based on work by Shreve.
1-3
-------
It is important to recognize that the frequency and intensity of rain are
37
important ecological variables. A summer rain totaling 150 mm in a given
locality might be the result of one or two rains during the season, perhaps with
a duration of two to three hours for each rain. Beatley has shown that in
Mojave desert ecosystems, heavy (>25 mm) rainfall triggers phenological events.
There is a predictable relationship between early winter heavy rain and successful
vegetative and reproductive growth of shrubs the next spring. Productivity of
desert plants is directly related to the distribution and numbers of desert
animals.7 However, in deserts, where small differences in the amount of moisture
are of great significance, the numerical relations among species are not con-
89
sistent from year to year or necessarily correlated with seed supply.
The climatic division of the American deserts into hot and cool temperature
regimes and into summer, winter and intermediate precipitation patterns is
reflected in the classification and existing distribution of desert vegetation,
but the recovery potential of an area will be an interaction between available
moisture and local soil conditions.
1.1.2 Soils
An ecosystem typically consists of a complex mosaic of overlapping patterns
that reflect, within the limitation of time and local materials, not only
present but past patterns of distribution of biota. A soil profile adjacent
to a Mesquite (Prosopis juliflora) or to a creosote bush (Larrea tridentata)
may differ markedly from a profile 2 meters away on barren ground. However,
the major soil type of almost all desert areas is similar. The basic charac-
teristics are coarse texture; an accumulation of carbonates within a few feet
of the surface contributing to the formation of a hardpan or a caliche layer;
and low organic matter content.
83 84 85
The United States Comprehensive Soil Classification System ' ' classi-
fies the soil order underlying almost all of the American deserts as Aridisols.
Soils of other orders, especially the Entisols, are also present but less
extensive in deserts. The Aridisols at the northern edge of the Great Basin
Desert are replaced by Mollisols.
Shantz70 has noted that regions defined as arid by geographers cover an
estimated 43 percent of the world's land area; however if defined on the basis
of climate, arid regions occupy only 36 percent of the earth's surface,
1-4
-------
35 percent if defined'on the basis of vegetation, but Aridisols cover only
about 25 percent of the surface. Thus, worldwide regions of soils classified
in the Aridisol order do not conform to all the parameters of either climatic
or vegetation zones.
The Aridisols, formed under low rainfall, are leached little and are there-
fore high in calcium, magnesium, and other soluble elements. Desert soils
seem particularly subject to the formation of impervious surface layerseither
by physical processes or through the surface development of algae and lichens
so that the effective drought is accentuated by excessive runoff. The Aridisols
are usually dry and are never moist as long as 90 consecutive days during a
period when temperature is suitable for plant growth. The low rainfall also
limits plant growth so that the soils are low in organic matter and have low
carbon/nitrogen ratios. The soils are young in profile development and show
little evidence of leached upper horizons. The combined A and B horizons
are frequently less than 30 cm thick. As a rule the A horizons are light
colored whereas B horizons are similar or slightly darker in color. The C
horizons are light-colored and usually calcareous. All horizons are neutral
or mildly alkaline.
Entisols are of such recent development that no horizons have formed. They
are most extensive on steep actively eroding; slopes or alluvial fans where the
rate of sedimentation is high.
Mollisols contain a thick A horizon high in humus and a base of calcium or
magnesium. In the northern Great Basin Desert they are formed under vegetation
consisting chiefly of grasses. The climatic regime is moist in winter and dry
more than 60 consecutive days in summer.
Much of the diversity in soil profiles reflects their origin. Coarser
fragments are found in soils developed nearer the base of mountains and hills,
and finer textures are found toward the middle valleys. Clay, if present, is
usually found in the B horizons in more level areas. Carbonate content of
soils is usually closely correlated with the origin of parent material, and is
highest in areas immediately adjacent to limestone mountain ranges. High
carbonate concentrations are almost always correlated with the presence of a
restrictive hardpan. Low carbonate soils are most often developed on alluvium
of mixed igneous and,sedimentary rocks.
1-5
-------
The particle size distribution of the soils also reflects formation of
alluvial deposits. Variation in texture is largely due to differences in
distributions of sand and silt particle size fractions. At low elevations
there is characteristically a low clay content, but increased clay concentra-
tions are found on alluvial sediments in closed drainage basins.
The climatic regime in which Aridisols form is characterized as one in
which precipitation is less than evapotranspiration during most of the year and
no water percolates through the soils. This has two important consequences.
First, horizons of soluble salts underlying calcium carbonate and gypsum are
normally found at the average depth of water penetration. This depth will be
important in relation to the consequences of a given depth of soil removal.
Second, since rainfall is seasonal, there will be periods when precipitation
is in excess of evapotranspiration and water will be stored in the soil to be
used in the spring or fall growing season. Thus, the time of year in which a
postulated cleanup takes place relative to the seasonal characteristics of
rain in that area is important for predicting ecosystem response.
There is ample evidence of accelerated soil-forming processes under desert
. 52 .
shrubs. The highest concentrations of organic carbon, organic nitrogen and
available phosphorus occur in the upper horizon under shrubs. Salts also
accumulate under shrubs, probably through litter decomposition from leaf fall,
54
although Odum noted that microbial decomposers would be limited by dryness.
(Odum speculated that rodent herbivores were important in this aspect of nutrient
cycling.) In the transition zone between the Mojave and Great Basin deserts,
the average carbon/nitrogen ratios have been determined to be about 10 while
in the A horizon under shrubs, values between 12 and 15 are common (the range
was 5-30). Only in the A horizon did organic carbon content exceed 1 percent.
These low C/N ratios could be due to low organic matter of desert soils, an
increase in nitrogen fixation, or a combination. Nitrogen fixing Azotobacters
are usually few or lacking on desert soils.4 Other differences in soils under
shrubs are noted: soil pH tends to be lower, conductivity of saturation extracts
higher, nitrates and chlorides accumulate more and exchangeable cations are
66
greater.
Algae and fungi grow in and on the soils contributing to fixation of
atmospheric nitrogen and to soil stabilization by forming crusts. These
1-6
-------
crusts attain a thickness of 2 to 3 millimeters and are sufficiently tough to
permit their removal from the soil surface, as a film. They may result in
considerable water runoff by sealing soil surfaces or they may result in
improved water-holding capacity. In addition to stabilizing the surface of
cohesionless soil, algae can add considerable quantities of nitrogen to the
soil through their nitrogen-fixing ability. Soil fungi may be necessary in
nutrient cycling. Symbiotic mycorrhizae, root fungi, associated with the white
bursage Ambrosia and the grass Hilaria rigidu are necessary for phosphorus
. 07
absorption in soils with low available phosphorus.
1.1.3 Topographic Factors
The effects of altitude on temperature and precipitation have been de-
termined in many desert localities. There is an average decrease of 1°F for
each 100 m rise in elevation but the rate varies with the season of year and
88
with local conditions. South slopes at a 90° angle to the sun receive 1.5
80
times as much heat as level areas. Shreve listed the principal features of
altitudinal climatic change as:
1. shortening the frostless season
2. lowering the daily curve of temperature throughout
the frostless season
3. increasing the intensity and duration of all critical
phases of low temperature during the frost season
4.
5.
6.
shortening the arid fore-summer, a critical period
increasing rainfall and thus soil moisture
decreasing evaporation.
4
Beatly showed the importance of local topography on vegetation distribu-
tion. Low temperatures resulting from downslope drainage of cold air into
closed basins coupled with differences in seasonal precipitation resulted in
anomalous vegetation mosaics at the transition between the Great Basin and
Mojave deserts.
A second effect of local topography is its relationship to rainfall. On
flat or gently sloping surfaces, rainfall leads to unconcentrated flow over
large areas, with thin and ^extensive sheets of moving water, known as sheetflow,
This results in the removal of a thin layer of soil from the entire surface.
Generally only the smaller soil particles are removed, to be deposited in low
.,1-7
-------
lying areas. Naturally rill and gully erosion occur also, and a distinctive
feature of desert areas is the erosional pattern.
1.1.4 Vegetation
The climatic divisions of the American desert of Meigs correspond very
78
well with the four regional deserts described by Shreve and shown in Figure 1-1.
In each of these regions further subdivisions into mosaics of vegetation types
are made by plant association communities which are distinguished by distinctive
combinations of dominant species. Desert perennial plants grow both singly
and more often in clumps, separated by bare areas of desert soil. Often a
clump of vegetation contains more than one species of plant; as many as 10
81
different species have been recorded from a single clump. The size and
spacing of the clumps are irregular. Some plants, such as creosote bush (Larrea
tridentata) thrive in several desert areas but other plants are restricted almost
exclusively to a particular desert region. These indicator plants are:
Great Basin Sagebrush (Artemisia tridentata)
Mojave Joshua Tree (Yucca brevifolia)
Sonoran Saguaro (Cereus giganteus)
Chihuahuan Agave (Agave lechuguilla)
1.1.4.1 Great Basin Desert-
Numerous mountain ranges are scattered over the Great Basin resulting in a
sharp vertical zonation of the plant life culminating in either a xeric or a
mesic forest cover on the range tops. The actual desert occupies the floors of
the detrital valleys.
The vegetation is a monotonous open shrubland with almost no cacti or large
plants. A distinctive feature of the vegetation is the predominance of com^
munities which are very simple in composition or have as much as 95 percent of
82
their stand made up of a single species. The commonest dominants are shad-
scale CAtriplex confertifolia), sagebrush (Artemisia tridentata), rabbitbrush
(Chrysothamnus spp.), blackbush (Coleogyne ramosissima), and winter fat
(Eurotia lanata). Open stands of greasewood (Sarcobatus vermiculatus) are
found on the saline flats. Indian rice grass [Oryzopsis hymenoides), indigo
bush (Dalea spp.), fourwing saltbush (Atriplex canescens) and a number of
1-8
-------
«
GREAT BASIN DESERT
(I 1 MOJAVE DESERT
SONORAN DESERT
CHIHUAHUAN DESERT
Figure 1-1. The North American Desert and Its subdivisions
(after Shreve/b).
1-9
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herbaceous plants and perennials are also found. Shrub coverage averages 24 -i
4
percent in the various associations, with a range of 15 to 37 percent.
The precipitation in several localities is higher than in any other part
of the American desert. It ranges from 100 to 270 nun. The winter temperatures
are low, and frequent snowfalls occur.
1.1.4.2 Mojave Desert
This is the smallest unit of the American desert and lies almost wholly in
California, with a small wedge extending into both southern Nevada and north-
western Arizona. Its elevated margins are delineated by the range of the Joshua
Tree (Yucca brevifolia). The bajadas are mostly dominated by creosote bush
(Larrea tridentata), but communities of four-wing saltbrush (Atriplex canescens)
and complexes of Grayia-Lycium, Lycium shockleyii and Ambrosia dumosa are
extensive. On the northern edge Coleogyne ramosissima and Grayia spinosa are
dominant. Shrub coverage averages about 16 percent ranging from 7 to 23 per-
cent. More spring ephemerals are found because of the mild, moist winters.
Annual precipitation decreases from 125 mm on the west to less than 50 mm
on the east, and occurs during the late winter.
1.1.4.3 Sonoran Desert
The subtropical Sonoran is the most varied of the American deserts and
exceeds the other three deserts in the number and variety of its life forms.
The desert lies between sea level and about 1,000 m. Above this upper limit
are isolated mountain masses that, due to orographic factors, can receive as
much as 700 mm of precipitation per year yet be located within a short distance
of Larrea plains.
More than half of the Sonoran Desert is dominated by plants with a stature
of less than 1.5m. Almost pure stands of Larrea, Ambrosia, Lyeium and Atriplex
are found. Larrea and Ambrosia dominate the lower portion of the desert but
they are joined by many shrub, tree, and succulent subdominants which become
more and more prominent toward higher elevations and greater rainfall. Often
two species, or sometimes three form the entire vegetation of an area. On
plains and bajadas below 300 m elevation the total perennial flora rarely
Q 9
exceeds 10 species. The most prominent cactus is the saguaro (Cereus giganteus)
Barrel cac'ti (Echihocactus spp.), hedgehog cacti (Echinocerrus spp.), and prickly
1-10,
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pears (Opuntia spp.) are common. Small legume trees such as palo verde (Cercidium
floridum) and C. microphyllum) and ironwood (Olneya tesota) are prominent.
Ephemerals are of two kinds, spring and summer flowering because of the bimodal
rainfall pattern characteristic of the Sonoran.
82
As Shreve notes, ;
"With the prevailing simplicity of composition, it follows that
the entrance or exit of a single species, or a great change in
the relative abundance of two or more species, may make a profound
change in the physiognomy of the vegetation."
t
Precipitation ranges from almost nothing to 300 mm on the eastern edge.
1.1.4.4 Chihuahuan Desert
The easternmost of the American Deserts is the Chihuanhuan Desert in the
United States covering part of New Mexico and Western Texas adjacent to the
Rio Grande. A large island of Chihuahuan Desert flora occurs along the San
Pedro Valley of Arizona, well away from the main body of the parent desert.78
The Chihuahuan is separated from the main part of the American desert and
makes no contact with other desert regions. To the north and east it grades
into semiarid prairiej while to the west the Continental Divide separates it
from the Sonoran Desert. Larrea, common to the Mojave, Sonoran and Chihuahuan,
is not continuous across the grassland that lies along the Continental Divide.
The prevailing plants are low shrubs, Larrea, Acacia, Prosopis or long leaf
succulents, Agave lechuguilla, and Hechtia. Several species of Yucca and in-
frequent cacti Opuntia are also found. Dominance is shared by shrubs, succulents
and semisucculents. The vegetation is most lush in the warm season, and there
are no winter and early spring ephemerals as in the other deserts.
Precipitation ranges from 70 to 500 mm, and about 80 percent falls between
the middle of June and the middle of September. Winter temperatures are low,
with occasional periods of 30 to 72 hours of freezing.
1.1.4.5 Desert Grassland
This arid biome is considered in this chapter because the southern section
forms a division between^the Sonoran and Chihuahuan deserts and because some
i
areas now classified as desert were once this grassland. (The northern and
98
western edges of the Great Basin Desert merges into the Palouse prairie of
1-11
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western Oregon and Washington. Recovery in this area is similar to that of the
72
short-grass prairie detailed in Chapter 2.) Shantz and Zon believed that
precipitation greater than 300 nun per year was required to establish and maintain
the Aristida-Bouteloua grassland.
The desert grassland has undergone significant changes in recent years.
In some locations grasses have been supplanted by shrubby vegetation, mesquite,
acacias and burroweed. Clements19 believed that much of what is now desert was
once grassland before overgrazing destroyed the grass, but more recent studies
emphasize the interaction of overgrazing with climatic change.
In the remaining Desert Grassland, annual precipitation ranges from 300 to
400 mm, with summer moisture slightly exceeding that of winter.
1.1.5 Desert Succession
A desert ecosystem is obviously not a static system, but usually tends to
approximate a dynamic equilibrium or to fluctuate around a stationary state.
An ecological climax is an example of that dynamic equilibrium and the process
by which the equilibrium is reached is termed succession. In order to understand
the effects of some environmental disruption, it is clearly important to distin-
guish equilibrium systems from those that have not yet even approximated steady
state. Equally important is to identify differences that may exist between
exceedingly slow changes, which are hardly distinguishable from the equilibrium
state, and changes that are more or less rapid. The rate of change is as funda-
mental for the concept of ecological succession and development as is the question
of whether the climax equilibrium actually exists.
The concepts of Climax and succession in desert areas will be reviewed in
the next sections of this chapter by identifying the empirical observations of
changes that have resulted from natural and man-caused environmental perturbations.
A caveat is required first however. It is not universally agreed that suc-
cession occurs in desert environments; if by succession it is meant that each of
a sequence of communities alters or modifies the physical environment to be
favorable for the next member in the sequence. Shantz considered succession
to be important as a basis for recognizing and understanding plant communities.
19 20 1
Other arid land investigators, notably Clements ' and Allred and E. Clements
stressed plant succession. However, the primary interest of these writers was
1-12
-------
-in arid lands, not deserts. Shreve cautioned about applying the succession
concept to deserts: ,- ..-.
In a consideration of the dynamic aspects of the vegetation of
the region in which the initial, sequential and final stages of
a succession are characterized by the same species, and often by
the same individuals, it is doubtful' whether'these conceptions,
formed in regions with a .very dissimilar vegetation, are of much
real utility. ,,' ' ' ' "
Muller was in general agreement and found no serai succession in recovery
of disturbed Chihuahuan Desert. Muller also noted that often the definition of
climax and the serai stages leading to it are made to narrow that very little
of the earth's surface may be said to be in climax condition.
Some features of recovery and succession after the proposed cleanup pro-
cedures are qualitatively similar to ecosystem recovery after natural, or man-
induced vegetation changes which have been documented for desert areas. These
features are presented in the next sections.
1.2 NATURAL PERTURBATIONS
1.2.1 Natural Processes
Succession on naturally disturbed desert habitats such as washes which
are periodically scoured by floods, actively eroded bedrock areas, or flood
; *. ' - gg :;._,...,
deposition on bajadas, has been studied little. Wells .noted that the charac-
teristic shrubs of these natural disturbed areas, Thamnosma, Hymenoclea, and
Salazaria, can be established in man-made disturbed areas and play a role ,
similar to that of pioneer successional plants of more humid areas.
Campbell has described natural vegetation succession in wind-formed hollows
(blowouts) between mesquite dunes as following five sequential stages. The
sequence only operates during a succession of favorable, i.e., wet, years. (The
major mesquite growth is in the spring when other perennials are practically
dormant.) The first stage is the Mat Stage. If moisture has accumulated in
the blowout, species with a prostrate habit such as Tribulus become established.
If moisture continues, either in the same or the following growing season a
Weed Stage begins, Ambrosia for example. This stage results in a gradual
decline in sand movement as the root systems develop. The third stage is the
lv-1'31
-------
Gutierrezia Stage, usually in the following growing season. At this point all
of the plants of preceding stages are found. Together they have a. generalized
drought-resistant root system. Wind and sand erosion is reduced and leveling
of the dunes along with sand deposition in the blowout area begins. If two
or three years of above-average moisture have occurred the Sporobolus Stage
of grasses begins. This is followed by a Bouteloua climax. Succession to the
fourth stage requires three to four years of ample rainfall. No estimate was
given of the time to climax.
Muller studied succession, or rather a cyclic phenomenon, in a Larrea-
Ambrosia association in the Chihuahuan Desert. In this area erosion removed
the climax association and all existing soil down to a clay hardpan. Muller
noted that succession, indeed plant growth, could not occur until the clay
weathered and until a few inches of sand and gravel were washed from adjoining
plains. The general sequence of recovery noted was shallow rooted grasses,
sparse shrubs tolerant of a slight soil covering over the clay, dense shrubs
as the soil deepened, sparse representations of Larrea, the climax association.
No time for this process was given. At the time of climax all the species of all
of the stages were present leading Muller to reject the idea of succession in
desert scrub.
1.2.2 Fire
Fire is known to influence desert plant distribution. Controversy exists
regarding the role of fire in maintaining desert grasslands, that is, the des-
ert grassland may be an artificial biome (a disclimax) initiated and maintained
by man. If this is true, artificial manipulation of deserts might result in
grassland. Numerous writers68'87 have hypothesized that grasslands are a product
of repeated fire set by primitive man. Humphrey40 among others9 has applied
this hypothesis to desert grasslands, largely on the historical evidence that
areas now desert were formerly grasslands, which through a combination of over-
grazing and fire suppression continued to desert climax. The theory says grass-
lands were maintained by frequent fires which prevented establishment of seeding
shrubs. Once the sequence of fire was broken, by overgrazing and fire suppres-
sion, seed bearing shrubs became established and a self-perpetuating, irreversible
vegetation change began.
1-14
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The incidence of fire in the past compared to the present is a critical
point. The controversy has been reviewed by Hastings and Turner35 who conclude
after examining travel journals of 22 early explorers that fires did not occur
frequently in the desert grassland in the pastalthough it is noted that fires
may have been locally important. They cite other factors which will be dis-
cussed later as cause of the decrease in size of desert grasslands.
There is an extensive literature of the effects of burning on desert vege-
tation. Although .these studies report intentional man-caused fire rather than
natural perturbations, they will be discussed here. The major thrust of these
studies was range improvement by using fire to remove undesirable brush and allow
grass and palatable forage species to grow. (This work shows implicit belief
in the fire theory of desert grasslands.)
The results appear to be contradictory. Humphrey41 found that burning prior
to the spring rains killed burroweed (Haplopappus spp.), partially controlled
mesquite and favored perennial grasses. Pickford57 in the Great Basin desert
found that burning destroyed sagebrush and allowed grasses to increase and a
more recent work indicates that forage species and grasses are increased
about 70 percent three years after burning. Reynolds obtained conflicting
results for a June burning of Great Basin vegetation. The density and produc-
tivity of the area were reduced and remained below control areas for three
growing seasons. The first year productivity was down 50 percent and the next
two years down 10 percent. The treatment did kill 90 percent of the burroweed,
half the cholla, and one-quarter of the prickly pear.
46
Longstreth and Patten have developed a model which postulates a number
of interacting factors that result in increased water and nitrate loss as
brush is converted into grassland. The loss of soil nitrate would result in
decreased productivity which agrees with Reynolds observations. It has been
noted that on heavily grazed ranges fire had little effect on the proportion
of grasses to forbs, but on lightly grazed ranges fire significantly reduced
grasses and increased forbs. This also might explain some of the conflicting
results noted of the effectiveness of brush burning on range improvements.
The effects of fire>are not permanent. The perennial vegetation of many
desert plants resprouts from the root crown of a pre-fire plant, then grows at
1-15
-------
the rate normal for the plant species. The time for complete recovery is
unknown; however 40 to 50 years, about 1/2 of the life span of desert plants, may
be a good estimate. ' Range reclamation experts recommend three to five-
year intervals between burnings to minimize undesirable species, but no indica-
tion is given of the amount of recovery to the pre-burn condition during this
time. Beatley measured vegetation parameters on adjacent burned and unburnsd
plots in Grayia-Coleogyne and Coleogyne associations in the Mojave-Great Basin
transition. The plots had been burned 13 and about 22 years prior to her study.
The burned areas were quite distinctive and easily seen in the vegetation mosaic.
The cover of herbaceous perennials in the burned area was only 20 percent that
of unburned plots; however, winter annuals increased by a factor of 2.5 and
grass (Bromus) was increased by a factor of 3 in the burned plots.
Pechanec recommended burning of sagebrush range in the late summer or early
fall after the seeds of perennial grasses had matured. The spring was recom-
mended by Semple as the best time to burn, for then the soil is damp and losses
of organic matter were not likely to be great. The principle appears to be
avoidance of detrimental effects on the perennial seed.
58 59
Piemeisel ' made detailed studies of the early stages of secondary
plant succession after fire in the Great Basin desert. He notes that the original
sagebrush dominated cover was exceedingly complex. The community was composed
of perennials with bulbs, tuberous roots, and rhizomes and perennials forming
mats, rosettes and tussocks. Most growth is made between October and July; the
time of autumn rains and the beginning of the next hot summer. Growth is inter-
rupted by winter cold and terminated by summer heat. The annuals grow in spring
and summer. The successional order is first Russian Thistle (Salsola spp.), then
mustards (Sophia parviflora or Norta altissima), then downy chess (Bromus
tectorum). These successional changes usually take place within five or six
years. Grazing by livestock or rodents may result in holding the vegetation
at one of these lower stages and retarding or preventing the reestablishment of
perennials.
1-16
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1.2.3 Climate
Long term climatic fluctuations which influence vegetation are well docu-
mented. For example, a synchronous change from juniper and pine woodland to
desert grassland occurred about 8000 years ago in the Mojave, Sonoran and
Chihuahuan deserts, probably associated with changes in global atmospheric circula-
tion patterns influenced by the melting of continental glaciers.92 Shorter term
and more recent fluctuations are more pertinent to predicting desert ecosystem
response to cleanup operations since rainfall, the major variable in climatic
change, is also the critical determinant of both desert vegetation community
type and speed of recovery.
Studies of tree rings have documented 25- to 60-year periods of moist cool
climates interspersed with dry warm climates in the southwestern deserts since
J f. O S3
the 15th century. ' These studies show climatic anomalies to be of non-
uniform geographic extent. For example, in the early to mid 1600's the Mojave
and large portions of the Great,Basin deserts experienced a climate warmer
and drier than usual while most of the Sonoran and eastern Great Basin were
normal, and the Chihuahuan was cooler and moister than usual.27
Recognition of the existence of these climatic fluctuations helps to inter-
pret apparent historical vegetation changes and their causes. A number of
authors have noted that the change from desert grassland to desert in the late
1800's coincided with a marked increase in man's use of grassland as cattle range,
and have speculated a cause and effect relationship between overgrazing and the
decrease in grass cover and increase in desert shrub vegetation.14'32 Hastings
and Turner documented the influence of climatic change on this massive shift
in regional vegetation and concluded that the new ecosystem was a response to
the unique combination of climatic and cultural stress. Climatic change reduced
soil moisture to a level below that required to establish new grass. Over-
grazing contributed to the imbalance between infiltration and runoff through
compaction of the soil and removal of existing grass.
1-17
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1.3 MAN-MADE PERTURBATIONS
1.3.1 Fencing
Studies of evidence of vegetation change resulting from the exclusion of
livestock from formerly heavily grazed land are abundant. Shreve recorded
77 81
changes in Sonoran vegetation 22 years after exclusion and again at 30 years.
He noted a general increase in plant population, that is, the number of species
remained rather constant over the years but the total number of plants increased.
The increase in the first 22 years was greatly exceeded in the next 8 years. No
Q
evidence of succession was found. Blydenstein followed Shreve's work at 50
years. He compared the original enclosures with nearby control sites. In both
the protected and unprotected sites the same species grew and in the same order
of abundance. The most notable change was an overall increase in density of
vegetation in the enclosed areas. Grasses and shrubs were beginning to replace
Larrea.
Gardner,30 reporting after 30 years of protection, found grass density about
twice as great in the enclosed area. A more recent study of only 10 years'
duration noted no vegetation change. The authors speculated that soil compac-
tion by grazing animals and/or erosion might account for the absence of effect.
Q *zr\
Other authors believe that it is soil erosion more than any other
feature that is responsible for the many instances of slow recovery following
livestock exclusion. When there has been little or no erosion and the original
plant species have not been entirely removed, protection from grazing may lead
to a rapid change in species composition and an increase in palatable (to cattle)
34
species.
To test the effect of rodents on range quality Brown established plots
that were grazed by cattle and rodents, by rodents only, and ungraded by both
cattle and rodents. He found that mesquite and Opuntia increased for all treat-
ments but the poisonous shrub burroweed (Haplopappus) decreased under total
exclusion. Morris53 found that excluding rodents increased the density of
native perennial grasses. A more recent study on 0.3 ha plots indicates that
seed-eating rodents and ants are in direct competition for the available food
supply. The exclusion of either .taxon results in an increase in numbers and
1-18
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bioraass of the other than results in a compensatory impact on plant population.
When both fauna populations are excluded a 2- to 5-fold increase in plant density
is noted.^
It has been speculated that the existence of a fence leads to increased
animal utilization along the fence line, resulting in soil compaction and vege-
tation removal, Hansen33 showed that cattle do not graze more closely and tram-
ple the vegetation near a fence than they did a hundred feet or more away.
Fences can act as protective as well as excluding landscape features. Elk
in Washington have been restricted to the Cascade Mountains in historic times.
However, they recently moved onto the ERDA Hanford research site which is fenced
and not subjected to livestock grazing.64
1.3.2 Overgrazing
The effects of cattle grazing on desert grasslands have been extensively
studied, but it is not always clear whether the observed effect, characteristically
an increase in density in unpalatable shrubs and a decrease in perennial grass,
were due directly to grazing or to associated factors, e.g., soil compaction by
the grazing animal. Most of the literature deals with the role of livestock in
promoting shrub invasion of grassland. Hastings and Turner35 have summarized
these studies and classified them to emphasize four ways in which domestic
grazing animals have been thought to contribute to the spread of woody plants.
The animals may act as disseminators of seeds, may reduce competition by
selectively removing one species which inhibits growth of another, might serve
as a fire suppression by removing the grass fuel from an area, or might reduce
the moisture content of the upper layer of the soil by compaction.
18
Christian and Slatyer have suggested a sequence of events which follows
overgrazing and leads to irreversible (within human memory) change in vegeta-
tion. First, a depletion of perennial grass occurs, followed by wind erosion
and a reduction of surface litter. The result is increased rainwater runoff,
decreased water penetration, and higher soil temperatures. All of these factors
create a more arid microclimate which inhibits re-establishment of the original
vegetation.
The effect of grazing on lands that are now desert is less well studied
than the effect on desert grasslands. Total primary productivity is low^in
1-19
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Over-
desert areas and the grazing pressure on the most palatable species is high.*
However, a characteristic of shrubs that persist in arid lands is adaptation ;to
stress.48 Rapid regrowth is a characteristic that enables shrubs to dominate
desert areas. A number of shrubs are known to increase primary productivity
and produce more new shoot growth when defoliated or closely cropped.
grazing can also lead to a change in species composition and introduction of
non-native species. Pechanec56 reported overgrazing of sagebrush (Artemisia
tridentata) in the Great Basin desert has led to the introduction of cheat-
grass (Bromus tectorum) at the expense of native perennial grasses. If more
species are removed than introduced, ecosystem stability will be lessened.
McKell48 has noted that the worth of any shrub species can only be deter-
mined by assessing its relation to the major ecosystem and the extent to which
user groups depend on it. Thus changes in species composition are not necessarily
detrimental but must be evaluated in relation to land use. For example, the salt
desert shrub community in the Great Basin desert moves toward dominance by black-
sage (Artemisia nova) when protected from grazing, while intense winter grazing
promotes an increase in shadscale (Atriplex confertifolia). This is not an
48
undesirable change for a rancher.
1.3.3 Mechanical Disturbance
The effects on vegetation of compaction of non-agricultural desert soils by
vehicles or animals, and by land alteration through blading or plowing, are
generally specified by empirical observation rather than experimental measure-
ment.
Almost any mechanical disturbance of the soil results in compaction since
no soil is free from susceptibility to compaction. The magnitude of the compac-
tion affects the rate of vegetation recovery. Compaction invariably results
in long lasting visible effects. Jeep and tank tracks from desert training
early in World War II are prominent in the Mojave, and Indian trails and wagon
*The definition of "most palatable" is obscure since relative shrub abundance
and local environment may modify animal preferences. The phenomenon of "scarcity
improves palatability" is well documented in range management.48
1-20
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45
or.
tracks of the last century can still be seen. Although compaction slows
recovery, natural processes eventually mitigate the effect. For example,
although the streets of 19th century mining towns are still clearly visible,
vegetation succession is occurring. '
The primary effects of compaction are a greatly reduced soil pore space and
increased bulk density which alter the relative amount of soil components present
in a given volume of soil. These processes lead to a decrease in water infiltra-
tion, a decrease in water storage capacity and restricted air movement. This
damage to soil structure severely impairs plant growth through decreased soil
moisture and by limiting root penetration. A reduction in pore space from 55
29
to 34 percent has been shown to eliminate all plant growth.
The secondary effects of compaction are changes in microclimate, since soil
bulk density and thermal capacity are increased while diffusivity is almost
unaffected. Soil temperature changes of -7°C have been recorded in compacted
vehicle tracks (vegetation removal increased temperature by almost the same
amount indicating a dynamic interaction between the effects of these processes)
Changes in microclimate can affect the germination of seeds.
99
Few data are available on recovery of compacted desert areas. Wells
showed possible succession in compacted areas. Gardner and Buffington
speculated that compaction, and subsequent erosion were major factors in inhibit-
ing regrowth in disturbed areas. Figures 1-2 and 1-3 show the persistence of
compacted areas in the Great Basin and Mojave deserts.
Recovery of plowed and furrowed desert land is somewhat better documented,
however. Rickard and Shields ' measured the early stages of recovery on 2.5 ha
plots denuded of vegetation by removing the surface 7-30 cm of soil with a bull-
dozer. After two years no shrubs had reappeared. Annuals were less abundant
than on adjacent undisturbed areas. This was probably related to the removal
of seeds with the surface dirt. Since annual growth is highly correlated with
rainfall and seeds can lay dormant until climatic conditions are optimum for
growth, the surface might contain the seeds from the previous three or four years'
production. Bunchgrass (Oryzopsis) was present only when the roots of the pre-
disturbance plant had not been completely removed. The authors concluded that
mechanical soil and plant removal were more deleterious than plant destruction
by atomic tests.
-------
Figure 1-2. Great Basin Desert roadway unused for
of compaction are evident. (Photo courtesy of UCLA.)
years. The effects
Figure 1-3.
Mojave Desert roadway unused for 17 years. (Photo
courtesy of UCLA. )
1-22
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Abandoned farm land in desert areas generally follows the pattern of
invasion by Russian Thistle (Salsola) during the first growing season, then
the replacement of Salsola by grass, beginning in the second growing season,
and.finally the gradual .reestablishmerit of the original brush vegetation.59
Gardner shows that thirty-years of protection were not.enough to. erase
the visible effects of plowing. Since soil is'known to be" compacted by improper
tillage, compactionris probably the'effect, noted. A disc harrow will compact
soil at shallow depths (7-10 mm) while heavy machinery and trucks will drastically
compact the upper 12-15 mm. Plowing often compacts soil at the plow depth.
Mechanical land alteration can also be beneficial to desert vegetation
'. - 11 "; - ' '' ' ' ' '
recovery. Brown and Everson; found that primary productivity on a ten year
old furrow in the Sonoran desert was two and one half times greater .than on the
intra-furrow areas. The furrow impedes runoff, increases infiltration and
reduces evaporation. Figure 1-4 shows this effect. These factors combine to
increase available soil moisture and increase localized plant growth. This
technique of land surface manipulation is used to assist the recovery of mine
spoil banks where different surface topographiesdeep chiseling, offset
listering, gouging and basin constructionare routinely used.90 It is also
employed to contour water catchment basins to assist agricultural production
in desert areas. Occasionally a catchment basin is inadvertently created.95
Figure 1-5 shows an unplanned catchment .basin and Andicates how-plant growth
is enhanced^by the slight extra water. Figure 1-6. indicates that the increased
water from roadway runoff can c'punt.eraet the effects of'compaction in desert
soils. ' ''.. ' ' . '.'.: '-'' " .' '.;
1.3.4 Atomic Test Target Areas
Atomic test and associated construction activities at the Nevada Test Site
have produced massive, and often-repeated, environmental perturbations, A
typical surface or low altitude atmospheric detonation would destroy, by blast
and thermal radiation, the vegetation in a circular area of 2-3 km2. An under-
2 ''-'.-'
ground detonation could cover ;3-4 km of desert with dirt ejected from the crater.
In addition, large areas would be cleared of vegetation or leveled to accommodate
diagnostic test equipment.
-------
Figure 1-4.
11 years .after blading and forming windrows.
fence at right encloses an area which has excluded grazing
s for 11 years. (Photo courtesy of UCLA.)
Great Basin Desert
The fe
animal
Figure 1-5.
Mojave Desert. An unintended water catchment basin in a dis-
turbed area. This basin concentrated the sparse moisture to
allow plants growing within it to become better established
than in the surrounding area. (Photo courtesy;of UCLA.)
1-24
-------
Figure 1-6. Mojave Desert. Larrea growing in compacted area alongside
asphalt roadway. Mojave species can reestablish themselves
on disturbed areas if sufficient moisture, such as runoff
from highway, is present. (Photo courtesy of UCLA.)
Three circular zones of damage have been identified around an atmospheric
test burst point. The first is an area about 1 km in diameter where all
surface vegetation has been eliminated by blast or fire. The inner 0.2 to 0.5
km portion has had the seed containing layer of soil removed by blast winds.
The second is an area extending about 1 km beyond the first zone where the
perennial brush is broken but grass survives relatively unharmed. Finally,
there is an area of shrub survival. This last area may respond to ionizing
radiation effects in the following growing season.62'63
The immediate injury is attributable to mechanical and thermal effects;74
however, recovery may be influenced by ionizing radiation. Radiation has, been
suggested as "stimulating" the growth of annuals,3 or conversely as causing
no observable effect.
The pattern of revegetation is well documented3'67'74'75'76 and the early
stages proceed faster than recovery on bladed areas.76 During the first year
the inner portion of the barren zone is sparsely populated by annuals, evidently
from seeds introduced naturally. In the outer portion of this'zone the ground
cover by annuals exceeds the total coyer ,of nearby undisturbed areas, possibly
1-25
-------
because of the lack of competition with perennials for the available moisture.
As the spring annuals die, the summer maturing Salsola dominates. Beyond the
perimeter of denudation recovery occurs through the crown sprouting of the
shrub species. In the second to fourth year the species composition of
annuals changes. Grasses begin to dominate and the area resembles the grass-
land scars of natural burn areas. Sal.tbrush (Atriplex canescens), a characteris-
tic species of roadsides, sandy washes and other disturbed areas, becomes
abundant. The short term changes in vegetation are analogous to the succession
qq 74 j
observed by Wells in a deserted townsite. After twenty years, summer and
winter annuals were found to be abundant, but there was virtually no recovery
of the original perennial shrubs. The few shrubs which persisted were
67
apparently crown sprouts.
Little work has been done to document the vegetation recovery on crater
ejecta. After nine years, Romney reported that Salsola and summer and winter
annuals were abundant except where the ejecta was "too thick," and speculated
that the soil moisture infiltration rate on the loose dirt was too great to
support vegetation.
1.3.5 Restoration
Attempts have been made to transplant seedlings and rooted cuttings of
shrubs to speed the process of revegetation. ' It was concluded that without
supplemental irrigation transplanting perennial vegetation was a futile effort.
Plant response and climatological behavior indicate that at least two and perhaps
three consecutive years of favorable soil moisture are necessary for sage
(Artemisia tridentata) seedling survival. In one experiment where additional
moisture was supplied to each transplanted plant, small animals destroyed all
unprotected plants within a few weeks. Construction of topographic features
which concentrate available natural moisture appears to be the most practical
method of speeding recovery.
1.4 EFFECTS OF CLEANUP PROCEDURES ON DESERTS
A number of cleanup techniques are available which vary in cost and efficiency.
This section will list some of these techniques in the order specified by the EPA
and will: (1) explain the technique; (2) discuss its effect on the local ecology;
(3) indicate the closest analogy to vegetation succession and recovery from some
natural or man-induced environmental perturbation; and (4) discuss the effect of
increasing treatment area.
1-26
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It is assumed that the methods used in construction industry and in farming
to protect the surrounding areas from harm, especially from erosion or the de-
position of eroded material, will be used. This will generally require the
construction of silt dams and diversions.
(1-1) Chemioal Stabilizers
The general purpose of chemical stabilizers is to bond the surface soil
particles together to form a protective layer and isolate the subsoil from erosion
due to wind or ,rain. The procedure often accompanies construction or road build-
ing activities'. Chemical stabilizers could be used to immobilize a contaminant
for a short (one to two years) period with a single application, for longer time
periods with periodic application, or they could be used in conjunction with
other cleanup techniques (e.g., scraping) to increase the effectiveness of the
technique by bonding the contaminant to easily removed clumps, or to'ameliorate
the erosion effects after the cleanup, especially on steeply sloping areas.
Vegetation is normally removed prior to treatment in construction activities;
however, most of the chemicals, especially the polymer emulsions or resins, could
be applied over vegetation if it was necessary to quickly immobilize the contamina-
tion.
Appendix A lists the chemical stabilizers preferred for desert areas. They
include oil and latex polymers, polyacylamides (PPA), polyvinyl alcohol resin
adhesives and other resins and polymers. These preferred treatments generally
have an effective life of less than one year. Other chemical agents such as salt,
sodium hydroxide, sodium carbonate, or iron chloride, also cause aggregation of
soil particles. The ecological effect of these deflocculants is dependent on the
soil ion exchange capacity and is highly area specific, thus will not be dis-
cussed here. Attempts to stabilize Pu contaminated soils at the Nevada Test Site
with deflocculants have been reported.95
The soil bonding produced by the chemical stabilizers will reduce moi-sture
infiltration and increase rain runoff. The chemical surface will also form a
mechanical barrier to seed germination. Some types of treatment will result in
absorption of solar energy and an increase in soil temperature. The increase may
be great enough to inhibit seed germination as the chemical surface begins to
degrade; however, this is unlikely since desert plants are tolerant to high surface
temperatures.
1-27
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The ecological effects result from changes in available soil moisture. Water
runoff from the impervious surface will increase vegetation growth on areas
immediately surrounding the treated area, much like vegetation growth is enhanced
next to desert roads (Figure 1-7). Care must be taken that this runoff does not
erode the soil from adjoining areas.
If vegetation is not removed prior to treatment, bunchgrass and perennial
growth will continue during the next growing season, either by normal branch
sprouting or, if the treatment kills the above-ground portion of the plant, by
root crown sprouting. Since moisture will be able to enter the soil at the
junction of the plant trunk and the earth, increased growth should occur since
much of the available moisture will be channeled to the shrub, and the treat-
ment will eliminate competition from nearby ephemerals while reducing soil
moisture evaporation. Ephemeral vegetation and annual grasses will not appear
until the surface begins to degrade. This might be the next growing season or
the year following, depending on the time of year of treatment application. In
.
Fiqure 1-7. Mojave Desert. The effect of increased moisture
roadside cut on Larrea growth. (Photo courtesy of UCLA.)
1-28
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time, about a year depending on the chemical selected, cracks will develop in
the surface. Moisture will concentrate in these cracks and allow .germination of
seeds resulting in localized vigorous growth which will accelerate the breakdown
of the surface. Moisture concentration at the cracks may have a deleterious effect,
If heavy rain occurs prior to the breakup of the crust and the establishment of
annuals, erosion can begin under the crack area. The probable results would
include faster breakup of the crust, gully erosion in the treatment area possibly
exposing hardpan and a change in the drainage pattern.
Although the effective duration of most chemical treatments is about a year,
clumps of stabilized soil, 5-20 cm in diameter will persist for longer periods
of time. Recovery of the area, compared to surrounding areas, depends on re-
covery of the ephemerals and grasses, which in turn is related to the breakdown
of the clumps of stabilized material. This should occur within three to five
years after treatment.
If the vegetation is removed prior to treatment, recovery of bunchgrass and
perennial shrubs will proceed from the underground portion of the perennial
vegetation as the surface degrades. The area will recover full biological
productivity within three to five years except where the soil has been compacted
by the brush removal or chemical application equipment. The treatment area will
be visible until the perennial vegetation achieves full statureabout twenty
to thirty years. The compaction effects of the heavy equipment will be visible
for a longer time. .
If the chemical layer is not toxic to animals it will not inhibit the
burrowing activities of rodents; moreover, the burrowing might bring to the
surface the material the chemicals were intended to bind. If the area is
relatively small, i.e., 1 ha, the rodents will probably not be displaced but
will forage for food outside the treatment zone. If the treated area is larger
than the animals' normal forage range, about 50 m for pocket mice to 100 m for
2 25
Kangaroo Rats, ' a migration to other areas can be expected. The effect
of this migration on the surrounding area would be difficult, if not impossible,
to measure. It is generally hypothesized that: desert rodent species diversity
is directly related to precipitation, through the relationship between precipita-
tion and primary production. It is doubtful whether the surrounding habitat
could support the additional population. The weaker members would die off.
As vegetation reappears in the treated areas, animals will return. Desert rodents
1-29
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of different species harvest different sizes of seeds and forage in different
microhabitats.12 Since there is little evidence of sequential desert vegeta-
tion succession, there should be no change in animal species diversity as the
treated area is recolonized. If vegetation is removed however, changes in rodent
diversity might be expected until the area is well along toward full recovery.
This point is discussed later,
Progressively greater care must be exercised for the larger treatment areas
to handle rain runoff. If the largest areas are treated on a routine basis over
a number of years, ground water recharge will be inhibited. The effects must
be estimated for each individual case.
(1-2) Clear Cutting Vegetation
Vegetative cover can intercept part of the deposit of an airborne contaminant,
and removing vegetation might remove a considerable portion of the contaminating
material while also inhibiting transfer and possible concentrations through food
, chains.
A number of methods are available for vegetation removal. Hand hoeing and
shovel cutting would be applicable for the smallest area, or for steep hillsides;
however, mechanical techniques would be required for larger areas. These mechanical
techniques include cabling and anchor chaining and are common in range improve-
31
ment programs.
In cabling, a 45 to 60 m long 3.75 cable is dragged between two tractors
traveling on parallel courses. The cable breaks off or uproots brush. Cabling
can be used where the brush breaks easily and is not willowy. The technique
results in little effect on perennial bunchgrass and usually leaves the
A soil horizon and humus at the base of the brush intact, an important considera-
tion for revegetation.
Anchor chaining consists of dragging a heavy (up to 50 kg per link) chain
through the vegetation to break or uproot plants. The general procedure is much
like cabling but the ground is more disturbed, the underbush humus is usually
scattered, and soil stabilizing algae clumps are broken. Chaining will clear
brush up to the size of small trees. The spacing of the parallel tractors,
and thus the spacing of the compacted areas, is dependent upon density of
1-30
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vegetation, weight and length of chain, size of tractor, bite of tractor tread,
and ground slope.
The effects of hand removal would be relatively benign. Most perennial
vegetation would resprout in the following growing season. The seeds of annual
vegetation would not be disturbed.
Soil compaction by the mechanical equipment would be the major deleterious
effect of mechanical removal. Broken perennials would resprout from underground
plant parts. The summer annual forb Russian Thistle (Salsola) would invade the
area, especially the chained area, the following summer since Salsola only
germinates where the soil surface has been scarified.94 Salsola roots cannot
penetrate compacted soil and would thus be restricted to areas between the
tractor paths. Winter annual grasses (Bromus) and the Salsola might delay re-
vegetation of the areas by native species by their effective use of available
soil moisture. Salsola can thrive at below normal desert rainfall levels;93
with normal rain annual grasses, followed by native ephemerals, would become
established. Recovery would be more rapid than if the seed containing layer of
soil were removed.
Erosion by wind would be a major problem until the annual vegetation or
algal mat was reestablished, .or until natural soil compaction by rainfall occurred
This problem is largely non-ecological however, since the main effect of eolian
erosion is .the removal of the A horizon of soil, which virtually does not exist
in desert soils. The major danger would be due. to winds spreading the con-
taminant beyond the treatment area. Dust from the area should produce no lasting
effects on the surrounding vegetation; however, 10 km2 denuded of vegetation
could produce a highly visible and undesirable dust cloud.
Vegetation removal is likely to affect microclimate. The low-level wind
speed profile will be changed due to changes in aerodynamic roughness.44 This
change will lead to increased evaporation, increased soil temperature and de-
creased humidity. These will affect both the revegetation of the treatment area
and the plant growth outside the area.23
Temporary food reduction would be the major effect on animals. This effect,
like chemical stabilization, will increase with increasing treatment area.
1-31
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(1-3) Stumping and Grubbing
This procedure would produce a drastic perturbation on the desert area,
and would probably only be used in conjunction with another cleanup technique if
it were desired to restrict the regrowth of perennial vegetation.
Desert plants have extensive root systems. The ratio of root to top of
plant varies from 0.5 to more than 4, and the majority of plants have a greater
biomass below ground than above. The structural roots systems range from
massive tap roots and secondary root systems to filamentous systems. The depth
of roots somewhat depends on the depth of hardpan or caliche deposits, but unless
these deposits are shallow most roots will extend to a depth of 1 m. Creosote
bush roots are known to extend 2m.
Roots can be removed by hand. However, mechanical methods would probably
be employed. A backhoe or crawler type tractor with a "hula dozer" blade can be
used to remove root systems.
The major ecological problems are again associated with soil compaction by
the equipment. However, the earth disturbed while removing the roots could
cover the annual-seed containing layer of soil and slow the initial stages of
natural recovery to two or five years. If caliche were brought to the surface,
it could form a pavement-like crust that might further restrict plant growth.
The treatment will destroy rodent burrows and probably result in immediate
death to a great portion of the local rodent population. Long term effects
will be related to the destruction of the food supply. Beatly has shown that
in Southern Nevada the dominance order of some heteromyids changes following
brush removal or ground clearing, i.e., replacement of Dipodomys microps by the
smaller D. merriami. She suggested an animal vulnerability to elimination by
predators of the larger species where there are few shrubs in the environment.
The environmental effects will scale with the size of the area: the greater
area disturbed, the greater the effect.
Areas of the Great Basin and Chihuahuan deserts which receive more than 250
mm of annual precipitation could be reseeded with grass to result in desert grass-
land; however, the prognosis for recovery within a human generation in other
desert areas is poor.
1-32
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(1-4) Sapopinff and Grading
The upper layer of soil to about 5 cm depth along with the contaminant would
be removed by road grader, land scraper, bulldozer or vacuum cleaner. This is a
drastic perturbation on the desert environment since it removes the small amount
of A horizon soil that exists under brush and also removes the seed containing
layer of soil. Wind and water erosion potential would be maximized and a further
deleterious effect would be soil compaction by the earthmoving equipment.
Under most circumstances the above ground portions of perennial vegetation
would be removed with the soil layer. However, it has been suggested that leaving
200-800 shrubs per ha would speed recovery by providing seed for natural re-seed-
ing. Desert perennial plant density normally ranges from 400 to 3000 plants
per ha. Thus, between one half and one quarter of the perennial shrubs would
remain if this suggestion is followed.
If both soil and plants are removed, some resprouting of shrubs could be
expected; however, the treatment would remove all traces of bunch grass. The
revegetation sequence of Salsola, annual grasses, native annuals, and the
gradual ^introduction of perennial species as outlined in Section III would
occur. Recovery would be slow. Animal recovery would be expected to follow
plant recovery.
If some shrubs are allowed to remain, the effect on the animals would not
be as drastic, since the brush would supply animal cover and food and provide
seed for continued revegetation. The humus under the plant could contain seeds
of ephemerals and would partially preserve the fertile shrub site in which
seedlings can become established.
In addition to the potential off-site problems that are associated with
erosion, some provision must be made either to remove or to store the contaminated
soil. This normally will require a tract of land in addition to the treatment
area.
Figures 1-8 through 1-13 show the recovery that might be expected eleven
and seventeen years after scraping a desert area.
1-33
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Figure 1-8.
Great Basin Desert. A 2 ha rectangular plot 11 years after
blading. Many grasses are present. The poisonous shrub
Halogeton can be seen in the lower part of the photograph.
(Photo courtesy of UCLA.)
Figure 1-9. Great Basin Desert 11 years after blading. (Photo courtesy
of UCLA.)
1-34
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Figure 1-10. Great Basin Desert. Demarcation line between land bladed
11 years ago (right) and non-bladed land (left). The bare
areas may relate to depth of blading. (Photo courtesy
of UCLA.)
Figure 1-11. Great Basin Desert. Area in foreground and right was
bladed 11 years prior to the photograph. (Photo
courtesy of UCLA.)
1-35
-------
Figure 1-12. Great Basin
reduce
Desert
to
of UCLA.)
years after application of water
dust followed by blading. (Photo courtesy
Figure 1-13. Great Basin Desert recovery 17 years after blading. The
cover in the foreground bladed area is about 25% of the
undisturbed area. It is unknown if the plant grew from
seeds or crown shoots. (Photo courtesy of UCLA.)
1-36
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(1-5) Sliallow Plowing
It is assumed this technique plows -the soil to a maximum depth of 10 cm
between the perennial shrubs. It disturbs both annuals and bunch grasses but
not most of the shrubs.
The ecological impact would be less than for surface scraping. The shrubs
would provide food and cover for animals and a seed reservoir for new growth.
Little humus would be lost and the seed-containing layers of soil would not be
removed. Scarification of the soil would enhance Sal sola growth for the first
two or three years. This growth would have little effect on germination of
annuals since Salsola is a summer germinating plant while other annual forbs
and grasses are spring and fall germinating. The potential for wind erosion
>
would be increased until ground cover by annuals is established. The potential
for water erosion could either be increased or decreased depending on the plowing
technique.
The visual effect, e.g., low furrows, would be visible for many years. There
would be little effect on animal food supply or population density.
(1-6) Deep Plowing
Plows capable of plowing as deep as 100 cm are available. This technique
would result in a complete destruction of the local ecosystem. Succession would
start from bare ground. The relatively thin soil under perennial, plant clumps
would be destroyed and most of the seed-containing soil would be turned under.
Animal life would be displaced or destroyed.
Larger areas would undergo initial stages of recovery more slowly than
smaller areas unless some form of revegetation were attempted.
Figure 1-14 shows the recovery to be expected from deep plowing.
(1-7) Soil Cover Less than 25 em
The purpose of this technique would be to bury and immobilize the contaminant.
It is a relatively drastic treatment. It would be difficult, if not impossible,
to accomplish without affecting the hydrological drainage system outside the
treatment area. As new drainage patterns are established and old ones abandoned,
the vegetation of individual areas would change, although the overall effect on
the region might remain unchanged.
1-37
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Figure 1-14.
Great Basin Desert 17 years after plowing. The area in the
foreground was plowed to a depth of about 30 cm. Cover on
plowed area is about 25% of that of the undisturbed area.
(Photo courtesy of UCLA.)
If the soil were placed without extensive compaction, some shrubs would
survive since a. few desert shrubs are evidently adapted to periodic silting by
erosional processes. Few data are available on the plants that could survive;
it is assumed those found in washes or arroyos such as Hymenoclea or Thamnosma
could withstand limited soil cover and grow. However, it is epxected that most
shrubs and all bunch grasses and annuals would be incapable of growth or germina-
tion.
Recovery would be essentially the same as starting from bare ground. Un-
less some type of seeding program were instituted, the growth of annuals on the
larger-sized treatment areas would not occur until winds deposited seed.
Compaction density of the fill will be an important variable for regulating
the time of the initial stages of recovery. If no compaction occurs the situa-
tion could approximate that around nuclear craters where the water infiltration
rate is so great that germination cannot occur. Alternatively, compacting to
a density greater than the original soil would also inhibit plant growth.
1-38
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(1-8) Soil Cover 25 to 100 cm :
This technique would result in the complete loss of the treatment area
ecosystem as well as off-site changes induced by changing surface drainage
patterns. Recovery of the treatment area would be from bare ground.
(2-1) Remove Plow Layer \
This cleanup procedure increases the severity of method 1-4, Surface Scrap-
ing and Grading, by removing slightly more soil. When the top 10 cm of soil are
removed all annual seed, humus, bunch grass and the meristematic tissue of
most shrubs would also be removed. A few shrubs would resprout from the roots,
but most would not. Recovery would essentially start with bare earth. In some
desert locations extensive deposits of caliche are found at plow depth. If
these are exposed the existing slow rate of recovery would be retarded.
(2-2 Remove Shallow Root Zone
This method would remove the top 40 cm of soil from the contaminated
area. This technique would remove both the A and B soil horizons and expose
the calcarous C horizon. The result would be complete destruction of the local
ecosystem. Recovery would begin from bare ground.
In any of the surface alteration procedures, i.e., scraping, grubbing,
plowing, or soil removal, loss of vegetation and the exposure of the soil to
winds and rain will lead to erosion problems. The magnitude of these problems
is discussed in Chapter 2, Prairies, and Chapter 8, Agriculture.
(2-3) Scrape and Grade* Mechanically Stabilize
This technique would use mechanical methods to provide stability to the
freshly scraped soil to retard or prevent soil erosion. The method would be
expected to lessen the impact due to erosional deposition on surrounding areas.
However, none of the possible mechanical stabilization processes would
appreciably speed natural^recovery, and some of the possible processes would
slow it.
Two categories of mechanical stabilization are considered here: compac-
tion and manufactured materials such as nettings, meshes, or plastic films.
1-39
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Soil can be mechanically compacted by bulldozer, rollers, or vibratory
processes to a density that rejects water. The degree of compaction is largely
a function of the amount of clay in the soil. The compacted soil can resist
wind and water erosion for decades. Eventually natural processes allow ephemerals
and grasses to become established. This vegetation helps loosen the soil so that
natural revegetation processes can occur. If the soil has a very high clay content,
as is the case for dry lake playas, revegetation might require centuries.
Although the surrounding area is protected from material eroded from the
treatment area, the increased water runoff during a rain, unless controlled,
would cause severe erosion problems on the adjacent land.
Manufactured material, like netting, placed over the scraped area would
provide protection against water erosion, and limited protection to winds.
The ecological effect would be substantially the same as if the mechanical
stabilization were not done.
Plastic film could also provide a protective layer. If exposed to air the
film would last 3 months to 2 years, depending on the composition of the film.
Films covered by earth could last much longer; however, winds could quickly
remove the cover. As the film degraded, normal restoration would occur.
(2-4) Remove Plow Layer, Mechanically Stabilize
A severe environmental disruption. The effect would be substantially the
same as described above, expect the compaction of the clay C horizon found in
many desert areas would form a long lasting barrier to recovery.
(2-5) Remove Shallow Root Zone, Mechanically Stabilize
A severe environmental disruption. The effect would be substantially the
same as described above.
(2-6) Scrape and Grade* Chemioally Stabilize
This composite method, like the mechanically stabilized methods described
above, would depend ,on soil removal to reduce contamination and a stabilizer to
both fix any remaining contaminant in place and to retard soil erosion. Any
cleanup procedure that removes soil results in loss of the local desert eco-
system. The chemical (and mechanical) stabilizers protect the surrounding
*Appendix A lists the stabilizers. It is assumed here that one of the preferred
stabilizers of Appendix A, as listed in Treatment 1-1 above, would be used.
1-40
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areas from losses due to erosion, but at the cost of slower recovery at the
treatment area.
The effects of scraping and grading were described in treatment 1-4 above.
The addition of a chemical stabilizer would retard the in-itial stages of re-
covery until the stabilized crust was degraded. Shallow scraping will leave some
perennial brush roots capable of resprouting, but forbs and grasses cannot
germinate until the surface develops cracks which allow wind borne seeds to be
deposited.
Since the stabilizer will prohibit water infiltration, provision must be
made for mitigating the effects of runoff on the surrounding areas.
(2-7) Remove Plow Layer, Chemically Stabilize
Soil removal is a drastic environmental perturbation,. The chemical
stabilizer would retard the initial stages of recovery one to two years.
(2-8) Remove Shallow Root Zone, Chemically Stabilize .--.
The ecological effects are substantially the same as described above.
(3-1) Barriers to Exclude People
This treatment would depend on isolating the contaminated area from human
contact. This will only be effective if the contaminant cannot enter the food
web leading to man. The most probable barrier would be chain link fencing six
to ten feet high. Such fencing can be expected to be useful for 25"to 30
years.
As long as provision is made for animal passage the barrier would have no
effect on local ecology. Some cultural, e.g., archaelogical, features would
also be protected by the barrier.
(3-2) Exclude Large Animals
Fences can be designed to inhibit animal movement. If cattle and large
game animals are excluded from the contaminated area, one direct link in man's
food web will be blocked.
Studies, described in preceding sections, have shown that cattle exclusion
does not result in changes in vegetation species composition (at least over the
1-41
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50-year measurement period), but that the number of individual plants, and thus
the total productivity of the fenced area, increases markedly. An increase in
primary productivity should lead to an increase in the number of small herbi-
vores .
A fence might produce deleterious effects on large animals in two ways.
First, it might exclude animals from natural water places. Second, it could
impede a natural migration path. Lack of a secondary watering place would prove
fatal. If other migration .routes were available they would probably be used.
(3-3) Exclude Lco^ge and Small Animals
This procedure would inhibit the transfer of the contaminant through the
food web. Barriers can be made to stop both the immigration and emigration of
animals. It is assumed that large grazing animals, e.g., cattle, burros,
antelope, deer, would be removed from the contaminated area. It would be possible
2
to exclude birds from the smallest treatment zone (0.01 km ) and it might be
worth the effort if a particular microenvironment, e.g., one containing an
endangered plant species, were to be preserved, but it would be impractical to
exclude birds from larger areas. The actual isolation of the food web leading
to man would require analysis of the local conditions and extent of man's use of
local birds.
It might also be possible to remove small animals from areas smaller than
about 1 km", but it is doubtful if attempts at either direct physical removal
or removal by poisoning from larger areas would be effective.
If small seed-eating animals are removed it is postulated that a compensa-
tory increase in seed eating insect populations will result in about the same
utilization of the local plant resource. J
The effect of inhibiting small animal movement, rather than removal, is
less clear and is undoubtedly related to the size of the area fenced. The inter-
action between plants, herbivores, and carnivores plays an important role in
the local ecology. Plants could exist in very small enclosed spaces. Herbi-
vores and carnivores require areas at least as large as their foraging range.
Only the largest area, 10 km , may be large enough to support a population of
carnivores in a closed system, based on ecologies existing on small isolated
1-42
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desert areas such as islands. It is not clear what the effect of smaller
fenced areas would be. One study, using the vole Microtus, found that 0.8 ha
fenced plots evidently destroyed the species' natural population control and
regulatory mechanism. The fenced population expanded until it was about three
times as large as control populations on adjacent sites. The result was
overgrazing and destruction of the habitat, followed by starvation induced
43
population decline. No evidence of this phenomenon was observed on 8 ha
plots in the Mojave desert ' although herbivore population densities within
the fenced ardas differed from adjacent control densities in non-uniform ways.
As long as the vegetation is not degraded or destroyed, recolonization of
the areas after removal of the fence would be relatively rapid. The abundance
of small mammals respond quickly to periods of good vegetation growth. They
have been reported to increase their densities at least five-fold within one
24 25
breeding season. French has shown that desert rodents in the Mojave Desert
disperse to great distances both as young animals and as adults during the non-
breeding season.
Continued maintenance of isolated animal populations could affect the gene
composition of the group. The smallest groups would be affected the most.
(4-1) Asphalt Hard Surface Stabilization
In this procedure asphalt or hot rapid cure road oil would be applied over
the contamination to immobilize it. The vegetation would be removed prior to
the asphalt treatment, but might remain for the road oil application.
The technique limits wind erosion; however, drainage and runoff of rain-
water to adjoining areas would be a problem.
In the asphalt treatment the ecology of the treatment area would be de-
stroyed. Some perennial plants would surviv;e the road oil, but the area would be
virtually useless to support annual vegetation or animals. It is expected that
vegetation at the edge of the area would exhibit enhanced growth due to addi-
tional available moisture.
The asphalt and. road oil treatments will affect local microclimate. De-
creased surface roughness will result in changes in the wind profile and will
decrease humidity. The local heat balance will be changed since an essentially
spongy surface of low heat conductivity will be turned into an impermeable
1-43
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layer with high capacity for absorbing and conducting heat. This will raise local
air temperatures. In calm weather conditions an inversion in the nocturnal
atmosphere can be created that will affect surface wind flow and temperatures
over a relatively large area. This "heat island" effect has been noted in
2 44
areas as small as 0.1 km . The lowered humidity and increased temperature
will deleteriously affect the small annuals and ephemerals more than the
perennials.
No recovery can begin until the surface begins to degrade. This should occur
in about three to five years for the road oil and five to ten years for asphalt.
(However, asphalt can be placed over a compacted base at a thickness which will
survive fifty years or more.)
As cracks develop in the surface both moisture and wind borne seeds will be
concentrated. The resulting growth will help break up the surface. As more
of the surface degrades, annuals, then perennial plants, will become established.
2
The largest area considered for this treatment, 0.1 km should not reduce infiltra-
tion and recharge to the extent that ground, water would be affected. However,
the water table under large paved desert areas, such as airports, has been shown
to move closer to the surface in response to reduced surface evaporation.
Figures 1-15 and 1-16 show recovery from road oil stabilization.
(4-2) Concrete Hard Surface Stabilization
This treatment is outside the scope of work.
(5-0) Application of Sewage Sludge
This treatment is outside the scope of work.
(6-1) High Pressure Washing
This treatment is outside the scope of work,
(6-2) Flooding
This treatment is outside the scope of work.
(7-0) Soil Amendments Added
This treatment is outside the scope of work.
1-44
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.' * -
I,-'5*-' i* '.
^^m^f^^Sy^i^£
Irt
Figure 1-15. Great Basin Desert. Foreground first treated with hot,
rapid-cure road oil s-tabili;:er, then scraped. Photo 17
years after disturbance. (Photo courtesy of UCLA.)
Figure 1-16. Soil 17 years after application of a hot rapid-cure road oil
stabilizer. The soil pieces vary from 1 to 5 cm thick.
Vegetation is growing in the area. (Photo courtesy of UCLA.)
1-45
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1.5 RECOVERY FOLLOWING CLEANUP
Earlier in this chapter it was noted that the concept of a single stable
climax vegetation in each desert type was not valid. A number of different
stable ecosystems may be possible depending largely on long term climatic
factors.35 Further, existing ecosystems are dynamic and changing with time*
Thus, recovery is best defined in terms relative to surrounding areas rather than
to some standard climax ecosystem, or to some measured pre-treatment condition.
It has also been shown that there are no irreversible changes; given enough
time the desert will adjust to any insult. Treatments which lead to massive
erosion and land form change will be permanently altered visibly although the
change will not affect the equilibrium ecosystem.
The endpoint for natural secondary succession and unassisted recovery follow-
ing application of one of the cleanup techniques can be specified in a number of
ways depending largely on the effort undertaken to measure the completeness of
recovery.
These endpoints include:
(1) No measured difference, other than normal variance based on measure-
ment technique and ecological variability, in selected ecosystem com-
ponents between the treatment area and adjoining undisturbed areas.
(2) No visible difference between treated and untreated areas apparent
to a desert ecologist, without benefit of field measurements.
(3) No visible difference to the layman.
In this chapter endpoint 3 is specified as defining recovery to climax condition.
Figures 1-17 through 1-20 give the recovery sequence for several of the cleanup
techniques between the end of cleanup and climax as defined by endpoint 3. See
Appendix B for applications.
1.5.1 Unassisted Succession
The vegetation stages leading to the defined recovery, based on information
presented in Sections 1.2 and 1.3 of this chapter are summarised below.*
*These stages may not be serai in that the vegetation which forms the pioneer
community is present at climaxindeed, the same plants may be present.
1-46
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CO
LU
o
u
01 NATURAL SUCCESSION3
1 1 CHEMICAt STABILIZATION
is
PERENNIAL
FORBS
ec
ui
Q
O
K
tc
i
o
ffl
i
ac
Y
PERENNIAL SHRUBS
PERENNIAL FORBS AND GRASS
Y
V
*o 1 10 100 200 to
°Also Scraping and Grading. Remove plow layer. Soil cover <25 cm
10
100200
Figure 1-17. Sequence of ecologic recovery following cleanup.
1-47
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1-5 SHALLOW PLOWING
1-2 CLEAR CUT VEGETATION
>£
°
/ i PERENNIALS
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Figure 1-18. Recovery sequence following shallow plowing
and clearcutting vegetation.
1-48
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1-3 STUMPING AND GRUBBING8
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Remove shallow root zone-Chemically stabilize '
Figure 1-19. Sequence of ecologic recovery following cleanup.
1-49
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2-3 to 2-5 SOIL REMOVAL. MECHANICAL STABILIZATION3 4-1.4-2 HARD SURFACE STABILIZATION
UJ
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PERENNIALS
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Figure 1-20. Sequence of ecologic recovery following cleanup.
1-50
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It is assumed that secondary succession begins with bare ground, which contains
no particular deleterious edaphic features such as surface clay hardpan or
caliche.
Bare ground, if scarified, is invaded by Russian Thistle (Salsola) the
first summer following cleanup. ' ' ' During the first year pioneer annuals
and grasses appear if adequate moisture is available, otherwise an additional year
or two may elapse. The timing of this initial annual colonization is'also de-
pendent on the size of the affected area. Areas larger than about 3 km will
require an additional year. The introduction of non-native annual grasses is
at the expense of native perennial grass. The result of this initial stage
in secondary succession is an annual grassland which can persist for decades,
or possibly hold at grassland stage by grazing and range management techniques.56
During this stage the density of grass and epheraerals on the treated area is two
to three times that on adjacent areas although the total productivity of the
area is lowered largely because older perennial shrubs produce the greatest
biomass. There may be a shift in the relative species composition of rodents,
which is restored as perennial shrubs reappear.
Starting in the second yearagain, assuming adequate moisturepioneer ,
shrubs characteristic, of disturbed sites, e.g., Atriplex, Thamnosma, Salazaria,
and Hymenoclea appear.
59,99
In the third year perennial shrubs which will make up the climax community
begin to sprout. Perennial vegetation requires a number of consecutive years
of above normal soil moisture and some relief from small animal grazing to become
established. Individual plants reach maturity in about 30 to 40 years. '
The area can be expected to have a perennial shrub density of about 20 percent
that of surrounding areas in 13 years and about 25 percent in 17 or 20 years. '
Complete recovery of the area should occur in about 80 years. '
Manipulation of the landscape to create pockets which trap moisture may be
used to speed the intermediate stages of succession, i.e., the early perennial
shrub stage. Enhancements of shrub density by factors of 2 within these
features have been noted but there is a corresponding lessening of density on
nearby plots due to restricted soil moisture so the net density for the area is
about the same. The landscape manipulation would speed the restoration of the
1-51
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original rodent species composition by providing earlier food and cover for the
displaced species.
1.5.2 Cleanup Recovery Categories
From the preceding summary of a hypothetical desert secondary succession
and the description of the cleanup techniques presented in Section 1.4, it is
clear that there are major divisions in impact among those cleanup techniques
that delay recovery, those that result in bare ground with no vestige of or-
ganic matter, and those where factors which relate to bare ground recovery are
ameliorated. In the first category it is important to note that eventually
the bare ground condition is approximated; therefore the time difference in
recovery amo.ng all the procedures that remove and stabilize the soil is actually
the time from the application of the treatment until the bare ground approxi-
mation is achieved. The consequences of this outlook are significant, for it
implies that once the seed containing layer of soil and the roots of perennial
plants are removed, the time to recovery is relatively independent of treatment
type. In the last category, recovery from a given cleanup procedure is di-
rectly related to the difference between the disruption produced by the cleanup
procedure and the bare ground state.
1.6 QUANTITATIVE ASSESSMENT OF CLEANUP IMPACTS
The rationale underlying assessment of the ecological impact of various
cleanup techniques is to be able to relate the cleanup procedure to the potential
hazard of a contaminant so that the environmental costs associated with the
cleanup can be weighed against the benefits of hazard reduction. Since these
cleanup techniques will have different levels of efficiency for different types
of contaminants, some measure of the impact of each procedure is necessary for
this evaluation to be made.
A number of measures are available to estimate the rate of ecological
recovery. They are usually in terms of changes in energy cycles, nutrient
cycles, food chains, density patterns in time and space, and various control
mechanisms. Unfortunately, the interrelationships among most of these in
desert ecosystems are Largely unknown.
1-52
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In this section, time of recovery to the climax desert community is taken
as a surrogate for ecological impact quantification. Implicit in this measure
is the assumption that recovery time integrates the effects of changing primary
productivity, species composition of both plants and animals and chemical and
energy cycling in the environment. Any other measure of the differential impacts
among the treatment types would scale about the same as time to recovery and
would produce the same ordering of impacts.
Unfortunately, the measure selected cannot be precise. First, deserts are
not homogeneous areas. Local eadphic and climatic factors interact with local
variations in plant and animal species to influence recovery rates. Second,
recovery is very sensitive to moisture, especially in the early stages of
pioneer vegetation growth. This means that the temporal distribution of rainfall,
as well as its magnitude, is an important variable. These climatic factors tend
to have a greater variance from the mean as the mean decreases. Third, the
magnitude of impact depends on the severity of the cleanup in any given situa-
tion, for example, shallow plowing was shown in Section 1.5 to be relatively benign.
If, however, the perennial vegetation is plowed (a circumstance which might be
dictated by local conditions) and if the plowing occurred at such a time that
the loosened seed containing surface soil were blown away by winds, recovery
would require 40 to 80 years rather than the 12 years estimated.
Table 1-1 lists the median time to complete recovery for each cleanup
procedure for various sized areas. There is no clear relationship between size
of area and impact listed in the literature; however, the impact is expected to
increase as the area increases. ;
1.6.1 Impact Assessment
For all size areas there is a relationship between severity of impact and
magnitude of surface disruption. Soil removal, no matter how slight, constitutes
a major perturbation to the ecosystem. Unfortunately, most procedures require
soil removal.
The real choices are: first, do nothing other than erect a barrier;
second, stabilize or turn under part of the contaminant; third, remove con-
taminated vegetation; fourth, remove contaminated soil. Choice 1,2, or 3
would allow time to evaluate expected effects in detail for a particular loca-
tion, but would be of limited usefulness against a hazardous contaminant that
1-53
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could enter man's food chain. The real decision may be between erecting, main-
taining, and monitoring a barrier until the contaminant is no longer hazardous,
or performing a cleanup procedure whose effects cannot be eradicated naturally
for 80 to 100 years and where ameliorative reclamation may be impossible. In
one respect this simplifies the cleanup decision since it implies that the only
variable which needs to be considered in desert environments is the efficiency
of the cleanup procedure.
In summary, cleanup techniques can be grouped into two major categories
of severity of/impact, each category being further subdivided into groups of
slightly differing degrees of impact. In the first category, that of less-
severe impact, the group of treatments having the least impact is the erec-
tion of barriers (3-1 through 3-3). The next lowest impact group includes
those procedures which are less extreme in the degree of bare ground state
produced. In this group are chemical stabilization (1-1), shallow plowing
(1-5), and clear cutting (1-2). In each of these treatments, the seed-con-
taining layer of soil is not removed, and perennial plants achieve relatively
rapid recovery. Ephemeral and annual grass growth is either enhanced or un-
affected.
In the second category, that of much greater impact, the first group
includes scraping and grading (1-4), soil cover less than 25 cm (1-7), and
plow layer removal (2-1), as these procedures result in a bare ground state.
Of very similar impact, though slightly greater, are stumping and grubbing (1-3),
shallow root zone removal (2-2), deep plowing (1-6), soil cover greater than 25
cm (1-8), and soil removal in combination with chemical stabilization (2-6
through 2-8). The last group, that with the most severe impact, includes the
treatments that combine soil removal with mechanical stabilization (2-3 through
2-5), and hard-surface stabilization (4-1 and 4-2), as the resulting soil compac-
tion would further delay forbs and grasses establishment and perennial vegeta-
tion germination.
1.6.2 Recovery Assessment
As discussed in Section 1.5, there are major divisions among cleanup tech-
niques with regard to time to recovery. In general, those treatments involving
less perturbation to the seed-containing layer of soil will result in shorter
recovery times than the treatments which effect the bare ground condition.
1-55
-------
Areas with barriers (3-1 to 3-3) will not experience succession in the .;
sense of the other cleanup technologies. The effects of barriers on vegetation
are somewhat dependent on the extent of pre-treatment overgrazing but are gen-
8 77 81
erally considered to be favorable by increasing the density of plants » '
and reducing animal-caused compaction.14'30 The longer an area is protected
77 81
from grazing pressure, the greater the total number of plants and biomass, »
However, exclusion of large animals might result in changed plant species compo-
sition leading to an'increase in poisonous species,10 and containment of rodent
populations might lead to massive density fluctuations and a reduction of vege-
tation biomass.43 For these treatments, the size of area would have little
effect; however rodent population fluctuation would not be expected for the
largest area.
Chemical stabilization (1-1), shallow plowing (1-5), and clear cutting
vegetation (1-2) can be considered a family of treatments with sequentially
increasing recovery time related to the amount of initial environmental disrup-
tion. In each treatment the seed-containing layer of soil is not removed, and
perennial plants (or their roots) remain to form the basis for relatively rapid
recovery. Chemical stabilization affects annual production for one or two grow-
ing seasons but should not otherwise alter recovery. Shallow plowing allows
most of the perennial shrubs to remain. Scarification of the surface will allow
Salsola to become established and reduce erosion, but once the soil is naturally
compacted to pre-treatment density and local erosion removes the plow furrows,
recovery will be complete. The slightly greater soil moisture found in the
plow furrows should enhance ephemeral and annual grass growth; however, even
this impact will be unmeasurable within 10 to 12 years. With both chemical
stabilization and shallow plowing, it is expected that the recovery time would
2
increase slightly as the area increases over 1 km .
Clear cutting vegetation allows perennial plants to resprout from existing
roots, thus time to total recovery is shortened and is equal to the time required
for a perennial shrub to reach mature stature about 40 years. The ephemerals
and grasses should not be affected by this procedure. Shrubs have been shown-.
to increase productivity when closely cropped. Hand cutting would not result
in the surface scarification necessary for Salsola germination. Chaining would
disturb some of the seed-containing soil layer and slow the early phases of
1-56
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recovery, but the slowest portion of recovery, regrowth of the perennial vege-
tation would not be affected and recovery within 40 years can be expected. The
size of area would have no effect on recovery time with this treatment.
The procedures of scraping and grading (1-4), removal of plow layer (2-1),
and soil cover less than 25 cm (1-7) result in an initial bare ground state and
exhibit the same successional pattern and timing as natural revegetation. Full
recovery is expected in about 80 years. The size of area is expected to have
a slight effect on recovery time as the area size increases beyond 1 km2.
Four of the techniques, stumping and grubbing (1-3), remove shallow root
zone (202), .deep plowing (1-6), and soil cover greater than 25 cm (1-8)
result in similar recovery patterns. Each treatment is capable of removing
or destroying all vegetation and both the A and B soil horizons, therefore total
recovery is retarded somewhat by the presumed existence of hardpan on the sur-
face. The hypothetical succession stages and their initiation are about the
same as for natural revegetation; however, at any given equal time plant density
would be slightly less for these treatments than for natural succession. It is
estimated that recovery would occur in approximately 85 years. The size of area
is expected to have a slight effect on recovery time as the area size increases
beyond 1 km .
Procedures which use stabilization in conjunction with soil removal (2-3
through 2-8) result in slightly longer recovery times than the preceding group,
but the recovery is not qualitatively different. The chemically-stabilized com-
bination treatments (2-6 through 2-8) result in a delay of the initial invasion
phase for a year or two, and climax should be achieved in 80 to 85 years. The
siz.e of area is expected to have a slight effect on recovery time as the area
size increases beyond 1 km . The mechanically-stabilized combination treat-
ments (2-3 through 2-5), exemplified by compaction, would delay the establish-
ment of the pioneer forbs and grasses for 2 to 10 years and would lengthen the
time until perennial vegetation germinated to about 15 years. About 90 to 95
years would be required for full recovery. It is expected that increasing area
size would increase the time of recovery. Hard-surface stabilization is an
extension of mechanical compaction; here, however, no pioneer species can becpme
established until the hard surface begins to degrade. From that point however,
recovery will occur in about 80 years.
1-57
-------
In summary, to a large extent, recovery time is relatively independent of
cleanup technique when the seed-containing soil layer and vegetation roots are
removed. The most drastic treatment adds only about 15 percent to the overall
time of recovery, compared to natural revegetation.
1.7 CONCLUSIONS
One important topic has not been explicitly addressed. That is, what is
the goal of restoration? The goal might be to restore the area to the pre-
disturbance ecological community. It might be to establish a similar, though
not exact, community, for example, a pure stand of creosote bush in place of
mixed perennial species. It might be to change the land use from desert to
desert grassland for grazing or even to agricultural land.
Two important factors dominate desert revegetation and ecological recovery
of disturbed areas. First, moisture is the critical determinant both of the
speed of recovery and the relative dominance of perennial shrubs or perennial
grasses. Recovery is usually impeded by the generally low infiltration rate
of desert soils so that much of the precipitation is lost as runoff. Second,
there is no serai succession; the perennial plants first established form
the stable climax community. A mature stable community is normally achieved in
about 80 years after a disturbance. Superimposed on these factors is evidence
that natural vegetation changes occur in response to long term climatic change,
and there is historic evidence that vegetation changes occurred at a time scale
that is comparable to that of unassisted revegetation. Successive dry years
reduce perennial grass cover, while a series of wet years has the opposite ef-
fect. A goal of returning a desert to a pre-cleanup condition may be impossible
if, during the restoration period, climatic conditions which existed prior to
the cleanup change. A new stable communuty may exist, but it might be different
from surrounding communities.
Of the treatments evaluated, several would require thoughtful considera-
tion prior to their use based on their deleterious effect on recovery of the
ecosystem. These are: hard-surface stabilization (4-1, 4-2), soil removal
followed by chemical stabilization (2-6 through 2-8), removal of the shallow
root zone (2-2), soil cover greater than 25 cm (1-8), deep plowing (1-6),
stumping and grubbing (1-3), removal of the plow layer (2-1), soil cover less
than 25 cm (1-7), and scraping and grading (1-4). As discussed in Section 1.6,
1-58
-------
the common factor in all of these treatments is the effecting of a bare ground
condition; once this happens, recovery time is greatly increased over the time
involved for treatments that do not create this condition.
Preferred treatments, therefore, in terms of ecosystem recovery, would be:
erection of barriers (3-1 through 3-3), chemical stabilization (1-1), shallow
plowing (1-5), and clear cutting vegetation (1-2). Unfortunately, for many
postulated materials requiring cleanup, the ecologically preferred treatment
may not be the most effective for hazard reduction.
1-59
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1-63
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Richard, W. H. and L. M. Shields, An Early Stage in the Plant Recoloniza-
tion of a Nuclear Target Area. Radiation Botany 3:41-43, 1963.
Romney, E. M., V. Q, Kale, A. Wallace, 0. R. Lunt, J., D. Childress, H. Kaaz,
G. V. Alexander, J. E. Kinnear, and T. L. Ackerman, Some Characteristics of
Soil and Perennial Vegetation in Northern Mojave Desert Areas of the Nevada
Test Site. USAEC Report UCLA 12-916, 1973.
, A. Wallace, J. D. Childress, Revegetation Problems Following
Nuclear Testing Activities at the Nevada Test Site. In (Nelson, D. J. ed.)
Radionuclides in Ecosystems, Proc. Third National Symposium on Radioecology.
USAEC Publication CONF. 710501 pp 015-1022, 1973.
Sauer, C. 0., The Agency of Man on the Earth. In Man's Role in Changing
the Face of the Earth, Chicago: University of Chicago Press, 1956.
Semple, A. T. Improving the World's Grasslands, FAO Agricultural Studies
No. 16, 1951.
Shantz, H. L., History and Problems of Arid Lands Development. In (G. F.
White, ed.) The Future of Arid Lands. Am. Assoc. Adv. Sci. 43, 1956.
Shantz, H. L., The Relation of Plant Ecology to Human Welfare, Ecoi. Monog.
10(3):311-342, 1940.
Shantz, H. L. and R. Zon, Natural Vegetation. U.S. Department of Agriculture,
Atlas of American Agriculture Part I Section E, 1924.
Shields, L. M., C. Mitchell and F. Druuet, Alga- and Lichen-Stabilized
Surface Crusts as Soil Nitrogen Sources. Am. J. of Botany 44:434-498, 1957.
, and P. V. Wells, Effects of Nuclear Testing on Desert Vegetation.
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and
, Recovery of Vegetation on Atomic Target Areas
at the Nevada Test Site. In (Schultz, V., and A. W. Klement, Jr., eds.)
Radioecology, Reinhold PubL. Company, N.Y., N.Y., pp 307-310, 1963.
, and W. H. Rickard, Vegetational Recovery on Atomic
Target Areas in Nevada. Ecology 44:697-705, 1963.
Shreve, F., Changes in Desert Vegetation.. Ecology 10:364-373, 1929.
, The Desert Vegetation of North America. Botanical Review 8(4):
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, Ecological Aspects of the Deserts of California. Ecology 6(2):
, The Vegetation of a Desert Mountain Range as Conditioned by
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_, and A. L. Hiclley, Thirty Years of Change in Desert Vegetation,
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, and I. L. Wiggins, Vegetation and Flora of the Sonoran Desert.
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Tenney, H.W., Variations of Atmospheric Temperature with Altitude in the
United States. Electrical Engineering 60(5):230-232, 1941.
Tevis, L. Jr., A Population of Desert Epheimerals Germinated by Less than
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, W. A. Rhoads, and E. F. Frolich, Germination Behavior of Salsola
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96.
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, and
_, Radioecology and Ecophysiology of Desert Plants
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, E. F. Frolich, and G. V. Alexander, Effect of Steam Sterilization
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1-66
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CHAPTER 2
PRAIRIE
2.1 OVERVIEW
Before overgrazing and cultivation of the 1870's broke the cover, the
native grasslands covered between 2.6 and 2.9 million square kilometers.of the
40
contiguous United States, or nearly one-third of the land surface. As a
general rule, grasslands occurred in areas having between 25 and 75 cm annual
.22
precipitation. Less precipitation usually resulted in desert and more
resulted in forest; exceptions occurred, however. Tallgrass prairie extended
as far east as Ohio (up to 100 cm mean annual precipitation), at least partially
the result of recurring fires, and grasses formed the understory of desert shrub
communities having as little as 18 cm precipitation per year.
Grassland communities, as the name implies, are dominated by grasses and
typically contain little woody vegetation. The grassland growth form is a
single, uniform layer of vegetation which does not provide for the variety of
48
niches found in more diverse communities, such as forests. Consequently,
the diversity of birds and insects, which can take advantage of vertical strati-
fication, is reduced. Grazing mammals predominate and range from large, running
herbivores, such as bison, to a considerable diversity of herbivorous and
granivorous rodents.
The term prairie is used in this report to mean midcontinent, perennial
grassland. Kiichler has identified approximately 15 grassland vegetation types
within this region. There is a general increase in cover from west to east
which roughly corresponds to rainfall distribution.
2.1.1 Tall grass Prairie
Tallgrass prairie consists of grasses 150 to 250 cm in height with roots
extending to depths of 180 cm or more. The dominant Andropogon-Panicum-
Sorghastrum association was continuous in the 18th century from Canada to
2-1
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Oklahoma with tallgrass islands in Wisconsin and east to Ohio, Kentucky and
Tennessee. The island prairies were undoubtedly successional stages, for fire
prevention in those areas invariably resulted in an increase in woody vegetation.
Because of its great agricultural value, little tallgrass prairie remains. One
remaining tract, described by Risser,31 will serve to illustrate a typical
association of climatic, soil, and biological characteristics. Mean annual
precipitation was 93 cm with 63 cm falling during the 205 day growing season.
Mean January temperature was 2.8°C and mean July temperature was 27.8°C. Soils
were Brunizems with the A horizon extending to 40 cm and the B horizon to over
100 cm. The list of common plants included the tallgrasses and forbs but did
not mention woody plants. The list of common animals was comprised primarily
of herbivorous rodents and insects.
2.1.2 Mixedqrass Prairie
The mixed or midgrass prairies are found to the west of the tallgrass
prairies in zones of generally lower precipitation. Midgrass prairies average
60 to 120 cm in height. They occur from Canada to northern Texas and the cli-
matic differences yield a variety of plant associations over the range. Mid-
grasses predominate but both shortgrasses and tallgrasses may be important
components. Lewis described midgrass prairie in western South Dakota. The
midgrasses Agropyron smithii and Stipa virdula predominated under relief from
grazing but there was an understory of shortgrasses, especially Bouteloua
gracilis and Buchloe dactyloides. Increased grazing pressure led to a reduc-
tion of midgrasses and the formation of shortgrass sod. Mean annual precipi-
tation was 38 cm of which 30 cm fell during a 126-day growing season. Ten
year (1958-1967) average temperatures were -1°C (January) and 24°C (July).
Annual potential evaporation was high, about 140 cm from a free standing water
surface.
39
In a mixed grass prairie in Kansas, tallgrasses (Andropogon gerardi,
Sorghastrum nutans), midgrasses (Andropogon scoparius), and shortgrasses
(Bouteloua curtipendula, B. gracilis, and B. hirsuta) all occurred in ungrazed
areas. Grazing increased the frequency of shortgrasses. Annual precipitation
was 58 cm with a 165-day growing season annually.
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2.1.3 Shortgrass Prairie
Shortgrass prairies average 15 to 45 cm in height and occur from Canada
to southeast New Mexico and west Texas. A northern shortgrass prairie described
by Jameson had Bouteloua gracilis and Buchloe dactyloides as dominant plant
species. Annual precipitation ranged from 25 to 38 cm with 80 percent occurring
during the summer. Mean January temperature was 4°C and mean July temperature
was 29°C. Soils (A + B horizons) ranged from 35 to 76 cm deep. Huddleston
described a shortgrass prairie near Amarillo, Texas. Bouteloua gracilis pre-
dominated with various other shortgrasses present. Prickly pear cactus (Opuntia
polycantha) was abundant with kochia (Kochia scoparia) occurring in disturbed
areas. Mean annual precipitation was 53 cm but pan evaporation was nearly
225 cm per year.
2.1.4 Other Grasslands
Outside of the midcontinent plains, major grasslands occurred in the in-
terior of California, as understory to conifers or as openings in the western
mountains, and as understory to arid-land shrubs in the interior northwest
and southwest.
Kiichler considered the native vegetation of the "California steppe" to
be perennial grasses of the genus Stipa. Today, these grasslands plus portions
45
of the surrounding, former oak woodlands are dominated by introduced annual
40
grasses, including Avena, Bromus, and Festuca. Climatic data for the California
Agricultural Experiment Station's Hopland Field Station indicate great varia-
bility from year to year. Mean annual precipitation for a ten-year period
was 94 cm, but the range was 63 to more than 150 cm. Summer droughts average
92 days in length and there are an average 70 days with frost each year.
Although the five unfavorable months divide the year into two separate growing
seasons, the dominance of annuals provides rapid response to community perturba-
tion.
The palouse prairie (shrub steppe) of the Columbia plateau is dominated
by Artemesia tridentata, a shrub, and Agropyron spicatum, a bunchgrass. The
area is characterized by hot, dry summers and cool, moist winters. ' Annual
precipitation is 25 cm or less. Desert grasslands are superficially similar,
2-3
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being associations of arid-land shrubs and grass understori.es. Desert grass-
1 9
land near Las Cruces, New Mexico is characterized by a black gramma climax
(Bouteloua eriopoda) with various combinations of desert shrubs, including
creosote bush (Larrea divaricata) and honey mesquite (Prosopis juliflora).
Mean annual precipitation is 23 cm with 55% coming between July 1 and
September 30. Characteristic of desert regions, however, is wide variation
9 1
and unpredictability of annual rains. Several successive dry years reduces
perennial grass cover while a series of wet years can have the opposite effect.
Pan evaporation is approximately 236 cm annually and mean maximum temperatures
range from 13°C in January to 36°C in June.
The vegetation of mountain grasslands varies with numerous factors, such
as latitude, altitude, slope and aspect. Van Dyne*^ estimated a total area of
2 .. 17
267,731 km from Kuchler's data, including that which occurs as understory
2O f\
to ponderosa pine. Site descriptions ' indicate annual precipitation in
the range of 33 cm and mean annual temperatures in the range of 7°C. Soils
(A + B horizons) may be fairly deep (60 to 110 cm) with the grasses being
rooted to the full depth. Agropyron and Festuca are the dominant grasses but
many other genera also are widespread.
Many of the proposed cleanup procedures are qualitatively similar to pro-
cesses, either natural or man-induced, which have gone on previously in grass-
lands. These have been divided into natural and man-made perturbations, those
activities which might be considered disruptive, and range improvement measures.
2.2 NATURAL PERTURBATIONS
2.2.1 Drought
The distribution of plant communities in the central United States in
general conforms to the distribution of rainfall. Any long-term changes in the
distributional pattern of rainfall would be expected to produce a general shift
in the distribution of plant communities. There is evidence that such shifts
did, in fact, occur in the past. A broad prairie "peninsula" extended into
Ohio during a warm, dry period following the last glaciation, but that prairie
was reduced to islands surrounded by forests by the time the first white settlers
reached the region. Drought of a lesser extent is characteristic of the prairies
2-4
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and, if of sufficient duration., affects the vegetational distribution.
Buffington and Herbel reported that in 1858 over 90 percent of the Jornada
Experimental Range in New Mexico was "good grass" while by 1963 less than 25
percent was. Located in a Bouteloua-Hilaria-Larrea association,17 a slight
shift in climate, with continued grazing, resulted in reduced grass cover and
1 2
an increase in desert shrubs.
The drought of 1934-1936 permitted the invasion of shortgrass and midgrass
species into the tallgrass prairie zone. Weaver and Bruner40 reported on an
Andropogon-Poa pasture which was converted to Sporobolus and Bouteloua. Only
8 years were needed for recovery, however, once the drought had ended.
2.2.2 Flooding
The effects of flooding are exactly opposite to those of drought. Periodic
floods, as well as ground water percolation, produced flood plain forests well
into the shortgrass prairies of Montana and Colorado.-17
34
Scifres and Mutz reported on an area of coastal rangeland in Texas which
undergoes periodic flooding. The native vegetation is mesquite-acacia savanna
in which the dominant grass is Setaria. Low-lying areas (lagunas) may become
inundated with fresh water for as long as 5 to 10 years as a result of tropical
storms. As the lagunas dry, a mesic sere is established which results in mid-
grass prairie, often dominated by spike dropseed (Sporobolus contractus).
Grazing capacity is doubled, relative to pre-flood stages, but long-term
grazing results in reversion to dominance by Setaria.
2.2.3 Fossorial Animals
Fossorial (burrowing) animals are characteristic of grasslands. They include
ants and termites, as well as the more conspicuous vertebrates. They all have
the net short term effect of setting back the development of both grassland
plant communities and soils. This is accomplished through both the direct
consumption of vegetation and the burial of vegetation with soil brought up
from depths of two or three meters or more.
2-5
-------
Abandoned prairie dog towns have been valuable in the study of local succes-
sional patterns (seres). Osborn and Allan' -reported on succession following
the decline of a prairie dog town in the Wichita Mountains of Oklahoma. As
the colony declined over a 9-year period, it progressively abandoned the outer
perimeters of the town until there remained an 8-step representation of the
local sere in more or less concentric rings. In the central, active portion of
the town, there remained barren soil with a few forbs. On that portion which had
been abandoned the previous year grew an annual species of threeawn (Aristida).
The next stage was also annual threeawn and the next a mixture of annual three-
awn and forbs, indicating that the local sere requires three or more years in
the annual grass stage. The next stage contained perennial grasses (Chloris,
Sporobolus) as well as threeawn. That was followed by a shortgrass stage domi-
nated by blue gramma (Bouteloua gracilis) and buffalo grass (Buchloe dactyloides).
Next came what the authors called a subclimax midgrass stage, characterized by
silver bluestem (Andropogon saccharoides) and sideoats gamma (Bouteloua curti-
pendula). The climax vegetation surrounding the abandoned prairie dog town was
a tallgrass prairie dominated by Panicum, Andropogon and Leptoloma species.
2.3 MAN-MADE PERTURBATIONS
2.3.1 Close Cropping and Grazing
The nonselective removal of grasses, such as by mowing, produces results
which differ considerably from selective removal through grazing. When species
composition and growing season biomass were studied in an Andropogon-Panicum-
Sorghastrum tallgrass prairie near Norman, Oklahoma, it was found that denuda-
tion (close cropping and removal of mulch) had no significant effect on species
composition when compared to the control. Net primary production (NPP, biomass
produced during a single growing season) was greater in the denuded plots than
in controls, however. Slightly different results were reported by Weaver and
Rowland for tallgrass prairie in Nebraska. They compared the prairie growing
on an abandoned dirt road with adjacent grazed or mowed fields. Again they
found that yields (NPP) were 25 percent to 50 percent less in the climax prairie
growing in the abandoned roadway than they were in the grazed or mowed fields.
However, they found a relative increase in the frequency of occurrence of
2-6
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Andropogon in the roadway. Since mowing is nonselective, they attributed the
increase in Andropogon to accumulation of natural mulch (see Section 2.3).
Grazing animals tend to select the plant species they consider to be most
palatable with the result being that intense grazing usually produces a shift
in species abundance. In mixed grass prairies, grazing can result in shortgrass
19 38
species replacing midgrass species, * and in a general decrease in canopy
46
height. In more arid regions, intense grazing pressure favors the establish-
ment of desert shrubs and can interfere with reclamation attempts.
13
2.3.2 Compaction
The short-term effects of compaction are all negative. The primary effect
is to increase bulk density of the soil (weight per unit volume) which decreases
infiltration of water, reduces water storage capacity, reduces aeration, inhibits
root penetration and restricts movement of soil animals. These effects are
most severe in moderately wet soils and in those with a higher clay, but they
a
can be significant in coarse-textured, arid-land soils as well.
The effects of compaction are not irreversible, however. Stipa-bunchgrass
stands may be found growing on the streets of a Nevada ghost town and climax
tallgrass prairie was reported to have been established 15 years after the
42
abandonment of a dirt road in Nebraska. Factors affecting the rate of recovery
from compaction include soil type, climate and presence or absence of surface
sealants.
2.3.3 Plowing
The effects of plowing are in many ways similar to the activity of prairie
dogs. Vegetation is killed and soil is turned over. The major difference lies
in the fact that deep, organic-poor soil is not deposited on the surface by
plowing. Most of our understanding of plant succession has come from the study
of abandoned agricultural land, most of which had been plowed for one or more
years.
2.3.4 Natural Succession
Succession in tallgrass prairie can be extremely rapid, especially if a
27
suitable seed source is readily available. Rice and Penfound reported an
2-7
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experiment carried out in an Andropogon-Sorghastrum^-Panicum prairie in Oklahoma.
In the first year after plowing, Ambrosia psilostachya (a ragweed) was the most
important dominant. By the second year, the dominants in the control had
replaced the ragweed. The authors concluded that "succession back to the
prairie stage was, therefore, extremely rapid under the conditions of the
experiment."
The fruits of grasses tend to be windborne and the fruits of pioneer species
tend to be carried further than those of climax species. Consequently, increasing
the size of the disturbance tends to lengthen the time required for succession.
28
Rice, et al., indicated that the fruits of triple awn (Aristida oligantha)
are carried great distances and triple awn is typically the first invader in
disturbed tallgrass prairie. Little bluestem (Andropogon scoparius) fruits
are windborne only about 2 meters and thus may take several generations to
reach the center of a large old field.
25
A typical tallgrass prairie succession was given by Perino and Risser.
Following abandonment of a cultivated field in Oklahoma, a weed stage is
established which persists for two or three years. This pioneer stage is charac-
terized by Ambrosia, Sorghum, Bromus tectorum, and Rumex. The weed stage is
followed by an annual grass stage lasting 9 to 13 years and is dominated by
Aristida oligantha, Aster sp., Ambrosia sp., and Andropogon saccharoides.
A perennial bunchgrass stage dominated by Andropogon scoparius follows and can
last 30 years or more. Tallgrass prairie climax becomes established after 40
to 50 years and consists of Andropogon gerardi, A. Scoparius, and Panicum virgatum.
The weed stage is characterized by a predominance of live vegetation (51%) which
declines to 26 percent at climax. Standing dead increases from 28 percent in the
weed stage to 32.5 percent in the bunchgrass stage and declines to 17 percent
in climax. Litter increases throughout the sere from 21 percent to 57 percent.
Areal cover declines from the weed stage to the annual grass stage but increases
through the rest of the sere.
2-8
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2.3.5 Range Improvement
2.3.5.1 Mulches--
Mulches increase soil moisture through increasing infiltration of precipi-
tation and reducing runoff and evaporation. Soil moistures and temperatures are
TO
stabilized and the conditions for germination of grass seeds are improved.
The effects of natural and synthetic mulcA^i are similar, but effectiveness may
1 42 -z
vary with the grass species, growth stage of the grasses, and local climate.
In desert grassland, an increase in soil moisture of 20 percent, due to mulch,
increased forage production by 50 percent. In climax tallgrass prairie, however,
naturally-occurring mulch was said to have reduced yields by 25 percent to 50
percent as compared to mowed or grazed fields where mulch did not accumulate.
In addition, application of mulch can reduce the frequency of less desirable
species, such as ragweed, by improving the conditions for emergence or growth
of the desired grass species.'
27,1
2.3.5.2 Seeding--
Seeding of desired grass species offers several advantages over dependence
on natural recovery. First, it is often possible to bypass succession and seed
directly to climax. Riegel, et al., seeded with climax species in west-central
Kansas and noted no differences in yields over a 17-year period when compared
to native grassland. In other cases, selective seeding can actually improve
the range quality. Rumsey reported forage yield increases of up to 300 per-
cent in 7-8 years in an Agropyron/Arternesia association. Seeding is not a simple
2
proposition, however. Bement, et al., were more successful with introduced
species than they were with native grammas, whereas Terwillinger and Jensen
had their greatest success with the grammas and other native species. Seeding
success or failure depends upon a number of factors, many of which are beyond
direct control. Terwillinger and Jensen found seeding in shortgrass prairie
to be successful only when the precipitation to evaporation ratio was 0.3 or
greater. Once the seed has germinated, sufficient ground cover must be achieved
before a periodic dry year to avoid wind erosion around the roots. In drier
areas,.e.g., desert grassland and shrub steppe, probability of seeding success
declines unless extraordinary measures are taken, such as water entrapment,
reduction of competition from woody vegetation, delay of grazing, mulching, and
rigid seeding standards.
2-9
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2.3.5.3 Shrub Removal-- ,
In 1858, over 90 percent of the Jornada Experimental Range in New Mexico
(Desert Grassland) was in good grassland range and by 1963 that figure had
declined to less than 25 percent. Climatic change may have been partly
responsible but grazing pressure on the grasses certainly gave a competitive
advantage to the shrubs. Range restoration included plowing to 9 inches
to kill the shrubs, seeding, and nft-i'sture trapping. In addition to range
restoration, new range has been created from shrubland by clearing of shrubs
50
and seeding with appropriate grasses.
2.3.5.4 Moisture Trapping--
Twenty-five centimeters annual precipitation is generally considered to be
the minimum required for successful revegetation of disturbed lands; less
9
requires intensive management including irrigation and fertilization. Re-
clamation and improvement of desert grasslands is further impeded by generally
low infiltration rates so that much of the precipitation received is lost as
runoff. Seeding success and production of herbage have been improved through
the construction of pits which trap runoff and allow a greater time for infiltra-
tion. In southern Arizona where annual rainfall averages 15 to 20 cm, moisture
penetration averaged twice as deep and herbage production was five times greater
when pits were employed as compared to adjacent flats. In a Utah salt desert,
Wein and West found that moisture entrapment was essential to survival of
crested wheatgrass (Agropyron cristatum) seedlings even if there had been suf-
ficient rainfall to produce germination without entrapment.
2.4 EFFECTS OF CLEANUP PROCEDURES ON PRAIRIE
This section describes the effects that imposition of certain contamina-
tion cleanup treatments produce on prairie ecosystems. Qualitative descrip-
tions of the effects caused by each cleanup treatment are related in this sec-
tion; the quantitative assessment of the impacts of cleanup on prairie ecosys-
tems is given in Section 2.6 with estimates of the relative times for a return
to the native ecosystem. Recovery time projections are based upon the presump-
tion that, if man were restrained from interfering, plant succession would go
2-10
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forward under the vegetative potential at the site and climate to recreate
a prairie. Reclamation procedures and other "management" of prairie sites
is discussed in Chapter 8.
Three groupings of the cleanup procedures can be seen in this section.
First is cleanup that provides temporary holding of a contaminant in place.
Second are procedures that remove the physical contaminant and stabilize the
site until renovation occurs, and third are alternatives to holding and
. removing the contaminant.
(0-1) Natural Rehabilitation
No significant impacts are expected to remain more than two or three years
after manual cleanup. Annual grasses will occupy the shoveled and scooped-out
excavations during the next growing season and that may be the entire sere.
No "area" effect is anticipated. The extrapolation is one of a succession of
"pock-marks."
(1-1) Chemioal Stabitization
When vegetative cover is removed, soils become subject to accelerated
erosion by both wind and water. The various 'stabilization practices may tend
to retard the initial stages of revegetation. Chemical stabilizers form a less
permeable surface layer which reduces infiltration of water and may also prove
to be a physical barrier to seed germination. Further, dark-colored emulsions
may increase soil temperatures above the range of tolerance for germinating
seeds. With time, however, cracks tend to develop in stabilized areas which
both allow seeds to germinate and channel runoff to seeds sprouting in the
cracks. As natural rainfall decreases, cracks in soil sealants can provide
micro-habitats which support relatively vigorous growth. In prairies, however,
sufficient moisture to permit revegetation is usually available and stabiliza-
tion techniques which retard revegetation must, be viewed as negative, long-term
impacts.
The properties of two groups of soil additives, 1) chemical stabilizers
and 2) chemical stabilizers with mechanical properties, are given in Appendix
A, Stabilizers. Eleven of the chemical stabilizers are rated "preferred" for
2-11
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prairie use, 10 of these require post-application site renovation for plant
regrowth; 7 of the 25 "preferred" chemical stabilizers with mechanical proper-
ties permit immediate natural regrowth of vegetation. All eight of the pre-
ferred stabilizers are rated to break down in a year or less after application.
(1-2) Clear Cutting Vegetation
Clear cutting of grasses (mowing) and removal is a common practice with
well-documented results (Section 2.3). Since the process is nonselective,
there are virtually no effects on species composition and, in the short term,
productivity is actually increased. On shrub-free grasslands, effects of
mowing and removal would probably not be discernible with a single growing
season. The presence of woody shrubs, however, increases the impact of clear
cutting. Woody plants have their meristematic (growth) tissues located at the
tips of branches as opposed to at ground level in grasses. Clear cutting thus
removes the primary growth tissues resulting in longer recovery times. Most
woody plants do have the ability to form stem tissue at the roots (root-sprouting)
so that clear cutting may have no profound effect on long-term community compo-
sition. A one-time clear-cut would allow woody plants to resprout using food
reserves stored in the roots but, as farmers well know, repeated cuttings
deplete stored reserves and eliminate the woody component.
(1-3) Stump-ing and Grubbing
"Stumping and grubbing" of grasses, that is, the removal of a major portion
of the root system, is not possible, owing to the diffuse nature of their root
systems. The procedure will prevent root sprouting of shrubs and will prolong
the period needed for complete recovery. Since reestablishment of shrubs would
then depend on reseeding, the size of the area treated would be proportional
to recovery rate. A secondary impact would be the effect of the treatment on
the area's attractiveness to wildlife. Grasses, generally, produce a single
vertical stratum which limits the number of niches available to bird species.
As shrubs and trees are added to grasslands, the number of strata increases
resulting in increases in bird species diversity. Removal of shrubs, trees,
or both could produce losses of bird species lasting decades or more and could
2-12
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possibly lead to the eradication of species already faced with limited habitat.
A detailed discussion is deferred to Chapter 10.
Positive results of shrub removal would include improvement of pasture
for cattle. Following the discussion above, it is apparent that improvements
would persist longer as size and severity of the treatment are increased.
Further, seeding success of shrubs would initially be reduced by the presence
of the grasses but, once established, shrubs are successful competitors of
grasses. The presence of cattle yields a favorable competitive balance to
shrubs since cattle will selectively remove grasses, when they are available.
(1-4) Sor aping and Grading
Surface scraping and grading of the upper 5 cm of grass roots and soil
could reasonably be expected to have only a moderate effect on grassland eco-
systems. In the prairies, ground irregularities would preserve the meristematic
(growth) tissues of a portion of the grass plants allowing relatively rapid
recovery. Soil compaction, if done with crawler tractors, could possibly have
a greater impact than the blading itself. In mountain grasslands, shrub steppe
and desert grasslands, blading would remove the woody component yielding a
significant change in community structure. Release from competition could
result in an increase in grass cover in arid zones with a corresponding
increase in animals utilizing grasses. The number of niches would be decreased,
however, with a resultant displacement of the birds and insects which require
vertical heterogeneity in a plant community. Taking the extreme examples,
2 2
0.01 km and 10 km of blading, the lesser disruption would produce effects
probably too slight to measure while the larger could have significant effects.
The significant effects could be both detrimental, such as long-term loss of
bird species, and beneficial, such as range improvement for domestic livestock.
(1-5) Shallow Plowing
Shallow plowing (<10 cm) will not penetrate the sod layer of most grasses
and would probably do no more than break off woody plants, allowing them to
resprout. It is not likely to be used as a clean-up procedure and if used is
not likely to have much impact.
2-13 '
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(1-6) Deep Plowing
Deep plowing (up to 40 cm) would result in complete removal of the eco-
system with succession starting from bare ground. This is the perturbation
that farming represents and is the best known event leading to secondary
succession (Section 2.3).
(1-7) Soil Cover Less Than 25 cm
A number of factors can affect the outcome of adding soil cover to the
community. With shallow coverage (<25 cm), quality of soil applied, actual
depth, and plant community would all affect impact level. The more shallow
the soil cover the less disturbance would occur, generally. In a mixed
plant community, woody vegetation would tend to be disturbed less than grasses.
In either case, grasses recover more quickly. The addition of porous topsoil
would have less detrimental effect than adding subsoil, since the roots might
still receive sufficient aeration.
(1-8) Soil Cover 25 to 100 am
There is probably no difference between adding 25 cm or less soil and up
2
to 100 cm. Even the smallest area to be covered, 0.01 km , would require 2500
m of soil for coverage to 25 cm. Expediency would undoubtedly result in
coverage with any soil available with the result that effectively all of the
vegetation would be killed. Thus, burial would result in a successional start-
ing point similar to scraping and grading (1-4), plowing (1-5, 1-6) or soil
removal (2-1, 2-2).
(2-1) Remove Plow Layer
Soil removal is a radical perturbation to an ecosystem. Removal of the
plow layer (^15 cm) would have an increasingly serious impact with decreasing
mean annual precipitation. In tallgrass prairie, the effect could be no more
serious than plowing, for the A soil horizon extends well below that depth
(Section 2.1). In shortgrass prairie, removal of the plowed layer could result
in virtual loss of the A and B soil horizons with long-term impairment of the
production capability of the soil.
2-14
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(2-2) Remove Shallow Root lone
Removal of the shallow root zone in tall- and midgrass prairies is
almost a contradiction of terms due to the depths to which grasses are rooted
(Section 2.1). Shallower soils, such as some shortgrass prairies, desert grass-
lands and mountain grasslands, could be removed down to C-horizon material if
30 cm of soil or more were removed. This would result in revegetation problems
analogous to deep cuts along roadways or spoil-bank reclamation. Comparable
removals in tallgrass prairie might shorten the projected cultural lifetime
(i.e., number of centuries which the land might be tilled successfully) but
the short-term (e.g., decades) effect might be indistinguishable from the effects
of plow-layer removal.
In either case, as with scraping and grading (1-4) and plowing (1-5, 1-6),
the complete removal of vegetation and exposure of soil would lead to predictable
erosional losses. Water erosion potential is obviously greater under the higher
precipitations and storm-intensities found in the more eastern grasslands. These
losses should not exceed normal agricultural losses on a scale of 0.01 to 0.1
2 22
km and, depending on locality, possibly over 1 km . At the 10 km scale,
however, significant increases in erosional losses may be anticipated, for it
would be hard to imagine landscape units of that magnitude which did not include
major drainages. Thus, complete removal of the soil or its retaining vegeta-
tion would effectively prohibit sedimentation from occurring prior to entry
into major drains.
Potential losses from wind erosion increase both with increases in the
size of the barren area arid with the reciprocal of the square root (l//r~) of
49
surface soil moisture. Again losses would be comparable to normal agricultural
losses when the area disturbed was similar in size to agricultural fields.
Plowed fields are typically broken up with trees planted for windbreaks, the
removal of which would increase soil losses exponentially since the sheltered
zone is calculated as ten times the height of the trees.
(2-3) Remove Scraping and Grading* Medhanioally Stabilize
Removing less than 5 cm of soil impacts prairie ecosystems less than
removing a shallow plow layer (2-1). The mulch layer would be taken, with
2-15
-------
a reduced impact on seed stores, soil tilth, and fertility, but wind erosion
effects could be approximately equal. Wind erosion on bared, prairie soil is
precipitation dependent. For prairie witn low precipitation (shortgrass) the
length of unobstructed wind run and soil particle aggregation at the exposed
surface become critical factors that determine the site wind erosion potential
in dry seasons of the year. In tallgrass prairie climates, soil losses by
wind erosion are normally minimal.
Stabilization is attempted to retard erosion, a desired result, but
carries with it a slowing of plant establishment, an undesired result. Mechanical
and chemical stabilization perform differently. Mechanical stabilization
compacts the soil while chemical stabilization binds soil particles together.
Either is accomplished by a number of methods or chemical agents, all with
qualitatively the same results relative to plant establishment and growth.
The properties of stabilizers are evaluated in Appendix A, Stabilizers.
Few mechanical stabilizers are rated "prefe-red" for prairie soils in
Appendix A, including deflocculants, clays, and membranes. Natural and
synthetic rubbers, polyethylene and vinyl membranes, paraffin wax, plus asphalt
emulsions exhaust that list, and only the asphalt emulsion permits regrowth
of plants the next season.
One popular method of mechanical stabilization depends on soil clay and
physical compaction to make an impervious surface. This may compress soil
sufficiently in making the physical barrier that it prevents subsequent seed
wetting and seedling emergence and revegetation. Soil moisture input through
the compacted layer is decreased by two conditions. Permeability to surface
water is seriously impaired by pore space reduction and a shortening of
infiltration opportunity occurs because of faster runoff from the smoothed
surfaces. Runoff can readily become 70% of annual precipitation. The
effects on revegetation, in principle, are similar among deflocculants, added
clays, and direct surface compaction. Heavily treated areas are toxic to
plants but are likely to be breached in a few months by resident small rodents.
The composite effects of surface soil compaction are intermittantly visible
in reduced vegetative growth for decades afterwards (Section III).
The use of meshes and mulches to reduce erosion are described in Sections 4.4
and 8.4 of Chapters 4 and 8.
2-16
-------
y Stabi lize
Revegetation potential at the cleanup site will be partially reduced
compared to plowing (1-5, 1-6), by loss of seed sources, mulch layer and
the upper fertile A-horizon. The significant revegetation impact is caused
from compaction by stabilization and its effect on water infiltration and
seed emergence. The smoothed surface allows rapid runoff with the possibility
of water concentration leading to piping and gully development on long over-
land runs. The high organic matter will make stabilization more difficult.
Physical retardation of seedling emergence limits early revegetation to shrub
crown sprouts. Gradually frost heaving, aided by localized punctures of the
surface by shrubs and small rodents, will be effective in opening the surface
to serious erosion; runoff water erosion in tallgrass and eastern midgrasses
and wind erosion at western mixed grass and shortgrass sites. This treatment
becomes a degraded version of 2-1. Chemical stabilization is preferable in
the eastern prairie.
(2-5) Remove Shallow Boot lone, Mechanically Stabilize
Treatment 2-2 has defined the ecological effects of removing 40 cm of
prairie soils and the mechanical effect of stabilizing was covered in Treat-
ments 2-3 and 2-4. This cleanup has severe side effects on shortgrass soil
profiles because most of the B horizon will be removed and with it much of the
fertility needed for revegetation. On these westside soils renovation is
required before succession toward grasses will begin. This is next to the
most severe treatment on prairie.
(2-6) Remove Scraping and Grading, Chemically Stabilize
This composite treatment appears similar to treatment 2-3 but is much
less drastic. In some respects it has an impact equivalent to windrowing of
the surface which might be done in 1-4. While there is a loss of surface
seed stores, the potential for erosion is reduced by chemical stabilization
while revegetation is started. Breakdown of chemical stabilizers occurs in
the next growing season if one of the preferred treatments from 1-1 is applied.
Revegetation should have produced a crop of annuals in the grasses and crown-
sprouting of shrubs should be well underway. Because these stabilizers are
limited to relatively small areas (Appendix A) natural seeding should suffice.
2-17
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(2-7) Remove Plow Layer*, Chemically Stabilize
The effects of removing 10 cm of surface sod present some problems to
cleanup crews. Using a turf-cutter would be the most likely procedure but
its decontamination effectiveness would be limited by micro-depressions and
contamination inside burrow tunnels. Plowing was described in Treatment 1-5
and those comments apply. The net effect of removing the plow layer to 10 cm
would be quite similar to Treatment 2-6 just described and hav&;, the same
impact on soil fertility. The impacts would be greater in shallow soils where
the plow layer is deeper than the A horizon. The prospects for revegetation
would be impaired to a minor degree.
(2-8) Remove Shallow Root Zone, Chemically Stabilize
This is a radical treatment because of the removal of the fertile, plant-
supporting medium on many sites and exposure of the C horizon in shortgrass
prairie. The application of chemical stabilizer to small areas as wind-erosion
protection can be tolerated but revegetation potential seems similar to 1-6,
starting from bare ground. Severe wind erosion should be expected in 2 or 3
years.
(3-1) Barriers to Exclude People
Fencing of a contaminated area to restrict movement of man and other
animals has been proposed as an alternative to decontamination, at least temporarily.
Generally speaking, barriers can prevent direct contamination but can be ineffec-
tive in preventing contamination by way of the food web.
(3-2 Exclude Large Animals)
Fences designed to exclude cattle and other large grazing mammals will
block one direct link in the food web leading to man. The release from grazing.
pressure will not necessarily be a desirable impact on the grassland ecosystem,
for the resulting increase in standing dead organic matter and mulch will have
a tendency to reduce primary production. Large exclusion areas would prove to
be an economic burden to the local population and possibly a detriment to
2-18
-------
migrating wildlifei Otherwise, the species diversity and stability of the
ecosystems would not be significantly affected and will not be treated
further.
(3-3) Exclude Large and Small Animals
The effect of barriers to exclude small mammals (rodents, etc.) will be
dependent, at least in part, on the size of the area fenced. Small areas, on
2
the order of 0.01 km , may prove to be too small to support viable populations.
The resultant release from rodent, as well as large mammal, grazing pressure
could possibly begin to affect the rate of return of nutrients to the soil and
overall community stability. Such a small area is not likely to be unique and,
if not, the loss cannot be considered to be significant. Large areas, on the
order of 10 km , would contain self-supporting populations of small mammals
and would be largely unaffected by barrier erection. Gene flow and genetic
plasticity could become affected, in time, but insufficient data exist to
evaluate this effect.
Neither birds nor insects can be effectively controlled by barriers. In
the case of upland game birds, such as ring-neck pheasants, feeding in the
contaminated area could lead to direct contamination of man. However, insects
are sufficiently small and far removed from the human food web, so unless the
contaminant is extremely mobile, contamination by way of insects is unlikely,
although some insect vectored contaminents might prove toxic to migratory birds.
(4-1) Asphalt Hard-Surface Stabil-Lzat-Lon
Decomposition of 3-inch-thick, unsupported hot mix asphalt requires more
than 10 years in the midgrass prairie on sandy soils when trampling by cattle
is prevented. In the meantime, reinvasion by stands of grasses is blocked
until the asphalt fractures or the surface cracks. The retardation of revegeta-
tion is absolute but if soil moisture conditions were right at .the time of
surfacing cold weather frost heaving can fracture the asphalt enough to allow
seed penetration, and germination and growth in the next season.
2-19
-------
Where shrubs intermingle with grasses the likelihood of puncture by root-
or crown-sprouts is high. Holes made by the sprouts and the new shrubs act as
collection points for debris, weed and grass seeds, and soil. Seeds germinating
in the drift piles speed breakup and weathering of the asphalt around the
punctures. Those local species that normally reproduce from seed should remain
at these breaks.
Soil compaction by the tank trucks and heavy trailers needed for asphalt
surfacing would be evident more than a century later as demonstrated by bison
wallows and trails. Hydrological impacts generated by the hard surface would
equal those described for Treatments 2-3, 2-4, and 2-5, but the site prepara-
tion impacts are greater than those treatments cause.
The gross effect of the asphalt hard surfacing is to delay for a decade or
more, beyond the delay caused by Treatment 2-5, the entry of the site into the
prairie sere. The treatment might be tolerated in shortgrass prairie as a
secure, temporary cover to minimize redistribution of contamination, the
certainty of breakup in a few years makes that use highly questionable. The
potential for gully creation in the relatively mesic tallgrass prairie precludes
use there anytime.
(4-2) Concrete Hard-Surface Stabilisation
Covering a site with concrete deals the ultimate impact among those cleanup
treatments proposed. All the disadvantages of asphalt surfacing plus the several
times greater durability of concrete chunks and blocks make later uses contingent
on removal of the concrete. This would be exceedingly expensive in either
transportation costs or onsite burial.
2-20
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2.5 RECOVERY AFTER CLEANUP
2.5.1 Irreversible Changes
No irreversible changes are anticipated with scraping and grading, plowing,
vegetation removal or flooding. Each falls within the range of analogous
perturbations (discussed in Sections 2.2 and 2.3 for which successional informa-
tion exists. Whether or not irreversible changes (i.e., failure to reestablish
a similar community within 25 years or more) would occur as the result of soil
removal or buri,ai would depend upon local conditions and the extent of per-
turbation. In most cases, no irreversible changes would be anticipated for
removal of the plow layer of soil or if suitable soil were used for burial.
In more extreme cases, such as on shallow mountain soils, in the most arid
margins of grassland distribution or where burial was with particularly low
quality material, extraordinary reclamation procedures might be required for
successful reestablishment of vegetation. These might include the land manage-
ment practices (Chapter 8) of water entrapment, irrigation or addition of soil
amendments. It should be noted, however, that reestablishment of vegetation
on a site does not imply lack of irreversible changes, nor does irreversible
change imply complete loss of a resource. The change may lower productivity
and prevent recovery of climax by establishing an entirely different flora than
the displaced grasses.
2.5.2 Rates of Recovery Following Cleanup
Rates of recovery are affected by several factors, including severity of
perturbation, proximity to seed source, local climate and soil conditions. In
general, recovery will be most rapid the less severe the perturbation, the
smaller the area involved and the greater the normal rainfall. In the dis-
cussion that follows, certain caveats are appropriate. Conclusions will be
drawn for major plant associations such as tallgrass prairie, which may cover
on the order of 10 km . The data supporting those conclusions are drawn from
studies which represent small samples from within the larger association and
typically do not begin to cover the range of possible seres. In a few instances,
appropriate seres simply have not been documented and it has been necessary to
extrapolate from the most similar situations that could be identified. It is,
2-21
-------
therefore, assumed .that this analysis will be useful in formulating policy
but that field-level decisions will require site-specific infoi-mation
Idealized trend curves were developed as guides to illustrate the time
course of recovery to full productivity for some of the prairie ecosystem
parameters. The o'rdinates are without, units either because they have no
dimensions (e.g., homostasis) or they are broad generalizations over the
array of heterogeneous prairie sites. Representative cleanup treatments were
selected for the illustrations. Assisted and unassisted recovery are shown in
Figure 2-1; recoveries of grasses and woody elements are illustrated in
Figure 2-2, and in Figure 2-3 the maximum contrasts in impact effects are shown.
2.5.2.1 First Year Following Cleanup--
With at least two cleanup procedures, mowing and fencing (clear cutting
and barriers), prairies should attain complete recovery within one year.
24
Penfound reported that denudation resulted in no significant change in
species composition and actually resulted in an increase in biomass. Since
"stumping and grubbing" are inappropriate for prairies, denudation would
consist only of mowing and removal of biomass. Complete recovery can, there-
fore, be assumed after one year. Size of area mowed would have no effect.
If a suitable seedbed remains after cleanup, prairies may be seeded
directly to climax?0 thus providing for near recovery the first year. This
would include scraping and grading, plowing, and most instances of soil re-
moval where some A horizon is left as a seed bed. The addition of nitrogen
fertilizer can aid establishment of perennial grasses especially if suffi-
q
cient moisture is present. Size of area is unimportant.
Assuming a suitable seedbed remains but with reliance on natural revegeta-
2 Q
tion, then the size of the area disturbed becomes important. Rice, et al.,*°
reported that the seeds of a climax species were windborne only about 2 m while
the seeds of an early invader were carried a great distance. Thus, assuming
seed sources completely surround the disturbed area and no differences exist
due to prevailing wind direction, in one year seeds of the climax species might
2
reach 7 percent of a 0.01 km circular plot (the configuration for maximum
potential invasion under the stated conditions). The area invaded declines to
2-22
-------
0-t NATURAL RECOVERY
RESEEDING
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figure 2-1. Natural recovery and recovery with reseeding
of prairie.
2-23
-------
12 CLEAR CUTTING
13 STUMPING & GRUBBING Of
WOODY COMPONENT
C/3
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5-10
YEARS
Figure 2-2. Time course of change after mowing (1-2) and stumping
and grubbing (1-3) of woody component of prairie.
2-24
-------
23
2-4 MECHANICAL SOIL STABILIZATION
2-5
3-1 BARRIERS (LARGE MAMMALS)
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cc
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YEARS
Figure 2-3. Recovery of prairie following mechanical soil stabili-
zation and response to the erection of fencing.
2-25
-------
2 "> 2
2 percent, 0.7 percent, and 0.2 percent for 0.1 km , 1 km , and 10 km circular
plots, respectively.
In areas not reached by seeds of the climax species, first-year invaders
are annual grasses and "weeds.
,,4
27 23
include Ambrosia psilostachya and Aristida sp.
In tallgrass prairie, first-year invaders
Russian thistle (Salsola
kali) is a first-year invader of mixed prairie. Launchbaugh reported first-
year basal area cover of 20 percent to 60 percent in Texas mixed prairie with
the annual grass Panicum texanum providing 36 percent of the cover. Other
annuals provided another 10 to 15 percent cover with the reminder due to non-
climax perennials. First-year invaders of shortgrass prairie include Salsola
kali, Amaranthus retroflexus, and Chenopodium album.
The annual weed stage persists for more than a year, typically. In an
Oklahoma old-field studied by Perino and Risser a weed stage comprised of
Ambrosia, Sorghum, Bromus, and Rumex persisted 2 to 3 years. Characteristic of
the weed stage is the relatively large proportion of community biomass con-
tained in the living vegetation component, 51 percent as compared to 26 percent
in the tallgrass prairie climax for the area.
To summarize first-year conditions in prairie natural successions, there
is little ground cover and that which is present is comprised of plants which
die at the end of the growing season.
If the cleanup procedure has left the surface with a less than suitable
seedbed, such as might be the case when soil is added to the surface, then it
is entirely possible that no significant, invasion will occur during the first
year. Stabilization would be required to prevent erosion and would result in
still further delays in vegetation establishment. Improvement of the seedbed,
such as addition of fertilizer and mulching if precipitation averages less
g
than about 7 cm can lead to seeding success. If the imported soil is of a
quality to encourage recovery, then it may also contain weed seeds which may
9
initially out-compete the local, desired species.
2.5.2.2 Fifth Year Following Cleanup--
41
Weaver and Bruner reported that 8 "normal" years, including 3 consecu-
tive "good" years restored a tallgrass climax which had been converted to
L-26
-------
midgrass by the drought of 1934-1936. It is assumed that 5 normal years follow-
ing a particularly wet year, would operate on a similar time scale.
Under the natural revegetation of circular plots, and assuming the 2
m
28
movement of climax species seeds suggested by Rice et al. " continues each
year, nearly one-third of a 0.01 km disturbed area would be in climax vege-
2 ' - .
tation. Only about 1 percent of a 10 km disturbed area would be in climax.
Areas too far from seed sources to contain climax species would, after
5 years, remain in an earlier successional stage. Osborn and Allan ^ identi-
fied 7 serai stages within a 9-year succession;on an abandoned prairie dog
town. The midpoint, after about 5 years, was characterized by a mixture
of annual grasses (Aristida sp.) and subclimax perennial grasses (Chloris and
Sporobolus). In another abandoned prairie dog town, subclimax perennial
grasses dominated after 7 years. Each area wa:; a tallgrass prairie climax.
After 5 years following plowing of midgrass prairie, it too was a
mixture of annual grasses (Aristida) and subclimax, perennial grasses
(Paspa1urn and Andropogon). Climax grasses had begun to appear but contributed
an insignificant amount of the total cover, only 0.2 percent. Total ground
cover (basal area) itself, was less than half that of the regional climax.
Thus, cleanup procedures which leave a suitable seedbed would most
likely remain in subclimax grassland following 5 years of natural succession.
Burial with soil could yield similar results if the quality of the soil added
is similar. Reliance on natural succession on poorer quality soil material
would probably result in slower rates of succession with annual grasses and
forbs possibly predominating after 5 years.
2.5.2.3 Tenth Year Following Cleanup--
For each of the cleanup procedures which leaves a plowed-fieldTlike
starting point, all prairies should be in subclimax grassland after 10 years.
Tallgrass prairie regions may still be dominated by midgrasses and mixed
grass or shortgrass prairies may be dominated by bunchgrasses. The 9^-year-old
successional stage in the abandoned prairie dog town was subclimax mid-
grasses, silver bluestem (Andropogon saccharoides) and sideoats gamma (Bouteloua
2-27
-------
curtipendula). Tallgrass prairie was the regional climax. A. saccharoides
still comprised 84 percent of cover after 14 years in Texas tallgrass prairie
I O
and 31 percent after 20 years. Western wheatgrass (Agropyron smithii),
needle-and-thread (Stipa comata) and feather bunchgrass (Stipa viridula)
47
dominated abandoned fields in western North Dakota within 10 years. The
authors stated that these midgrasses were characterized by low total density
but that they nevertheless produced a relatively high yield of good quality
forage and were valuable hay land.
Not all authors agree, however. Booth stated that annual grasses still
predominated after 10 years in southeastern Kansas and east-central Oklahoma.
Few differences between cleanup procedures would be discernible after 10
years of prairie succession. Prairie soils are sufficiently deep that scraping
and grading, deep or shallow plowing or removal of soil up to 30 cm would leave
a sufficient seedbed to produce comparable stands within a decade. If burial
had been with particularly low quality soil, and no other treatments had been
performed, then succession would lag sufficiently that prairies might remain
in the annual grass or grass/forb stage after a decade.
2.5.2.4 Climax--
Tallgrass prairie apparently can return to climax very quickly if the
disturbed area is small and climax species are nearby. Weaver and Rowland
reported that Andropogon-Sporobolus-Panicum prairie was established on a dirt
road only 15 years after abandonment. Perino and Risser reported a somewhat
longer .sere. They described a 4-stage sere starting with (1) a weed stage
(Ambrosia, Sorghum, Bromus, Rumex) lasting 2 to 3 years, (2) an annual grass
stage (Aristida oligantha, Andropogon saccaroides) lasting 9 to 13 years, and
(3) a perennial bunchgrass stage (Andropogon scoparius) lasting 30 years or
more. Equilibration or climax would not occur, therefore, for 40 to 50 years
following disturbance. Climax was Andropogon gerardi, A. scoparius and
Panicum virgatum.
Costello described succession in northeastern Colorado mixed grass
prairie as (1) an annual forb stage (Salsola kali, Amaranthus retroflexus, Cheno-
podium album) lasting 2 to 5 years, (2) a forb stage lasting 3 to 6 years,
(3) a short-lived perennial grass stage (Schedonnardus paniculatus, Hordeum
2-28
-------
jubatum, Sporobolus cryptandrus) lasting 4 to 10 years and (4) an Aristicla
stage (Ar ist ida 1ongi s e t a and A. purpurea) lasting 10 to 20 years. Transi-
tion to climax was estimated to take another 10 to 20 years. Thus, the sere
could be as short as 15 to as long as 60 years with drought cycles retarding
succession and wet years accelerating succession.
18
Launchbaugh described the sere-of the San Antonio Prairie in Texas.
Following cultivation, an annual grass stage was established the first year
with Panicum texanum being the dominant. Annuals gave 82 percent to 85 per-
cent of the cover and subclimax perennials gave the rest. No climax species
were present the first year and cover (basal area) was low 20 to 60 percent.
After 5 years, annuals (Aristida supp.) contributed only 46 percent of the
cover and subclimax perennials had increased to 47 percent (Paspalum and
Andropogon). Climax species were represented (0.2%) and basal area had in-
creased to 2.1 percent. After 14 years, annuals were only 7.2 percent of the
plants present and subclimax perennials (Andropogon saccharoides) had increased
to 84 percent. Climax species (Sporobolus and Stipa) had increased to 5 per-
cent and basal area had increased to 2.7 percent. After 20 years, annuals were
3.5 percent and subclimax perennials 31 percent. Climax species had increased
to 60 percent, most of which were Andropogon scoparius. Basal area was up
to 3.3 percent. No estimate of the additional time required to reach climax
was given. A climax community was described, however, and the climax species
(Andropogon and Bouteloua) were 94 percent of the vegetation and basal area
v;as up to 4.8 percent. Both annuals and subclimax perennials were represented
in the climax community, 1.3 percent and 1.1 percent respectively. Whitman,
47
et al., estimated 40 to 60 years or more were required for succession to
climax in North Dakota mixed grass prairie.
A shortgrass prairie in Colorado was still in the annual grass (Aristida)
35
stage 21 years after abandonment. Shantz estimated to reach climax in short-
grass (Bouteloua-Buchloe) prairie it would take 20 to 50 years following plowing.
2-29
-------
2.6 QUANTITATIVE ASSESSMENT OF CLEANUP IMPACTS
The boundless forests of the eastern U.S. are matched, in diversity by
the limitless span of grasslands reaching west up the Rockies from the eastern
forest's edge. On high western plains removal of 40 cm of soil (2-2) leaves
an alkaline, frequently saline excavation in North Dakota, with 300 to 500 mm
annual precipitation-for short and mixed grasses to revegetate the Colorado
plains on intermittantly exposed parent material (A through upper B, horizons
removed). On the excavated eastern prairie there may be no noticeable reduc-
tion in soil profile properties, plus 1800 mm of precipitation falls under
which tall grass revegetation will progress. Assessments of cleanup impacts
and subsequent time to recover productivity are reduced to generalities that
address this range of site diversity. Over their summer rain, wind, and
unshaded range, the grasses did maintain, with rare exceptions, an almost
permanently dry subsoil below the root zone. This land has been appropriated
throughout for agriculture. Recovery is treated in this chapter in the context
.of principles governing an unmanaged ecosystem; agriculture is examined in
Chapter 8.
2.6.1 Impact Assessment
Mowing prairies (1-2) has no long-term effect. The slight increase in
impact rating with increased area relates to reduced food availability to
herbivores and reduced cover for wildlife. Scraping and grading (1-3), and
shallow plowing (1-5) have limited impact when localized but represent an
extension of the trend mentioned for mowing. Deep plowing (1-6) requires
reinvasion of species from outside of the disturbed area, hence the greater
increase in impact level as area increases. Soil burial (1-7, 1-8) requires
plant reinvasion and also has greater impact as area increases. But since the
transported soil added is assumed to provide a seedbed inferior to the soil
covered up, impact is greater than for other treatments requiring reinvasion,
such as deep plowing. Soil removal (2-1, 2-2) requires reinvasion also and
since deep plowing may leave seeds to germinate, the removal of seeds with
the soil results in a greater impact. One intuitively feels that removal of
up to 40 cm of topsoil should be a greater impact than removal of 10 cm. In
deep prairie soils, however, it is not entirely clear that it is. Hence, there
is just a slight increase in impact level. Barriers to exclude people would have
2-30
-------
essentially no impact on prairies. Trees might invade the eastern prairie
remnants if man-made fires were excluded, but that is not considered a negative
impact. Exclusion of animals by barriers (3-2, 3-3) should have little long-
term impact, since the grasses to support grazers would remain. Animal popula-
tions are expected to quickly recover when permitted back in. Paving represents
the ultimate loss with the area paved being the only qualifier.
2.6.2 Recovery Assessment
Factors which affect the rate of recovery in prairies have been discussed
in Sections IV and V. Because of the interactions of those factors, quantifica-
tion of the time required for recovery (Table 2-1) cannot be precise. For
example, scraping and grading (1-4) of grassland may not result in death of
significant numbers of grass plants and recovery may be extremely rapid, two
or three years. However, the potential exists for all of the grass plants to be
killed with the subsequent recovery taking as long as recovery from plowing,
up to 60 years. Nor can a superficially more-destructive, cleanup procedure
be counted upon to require longer recovery times than a less destructive one;
hence, the overlapping ranges in time required to return to full productivity.
Impact is also expected to increase as area increases, but with the
exception of more rapid revegetation of smaller areas, no clear relationship
between area and time-to-climax is apparent. Succession on homogeneously
2
barren areas of up to 10 tar. has not been documented and extrapolation from
smaller areas is dangerous. The dividing point in time to recover seems to
2 2
be between areas smaller than 0.1 km and larger than 0.01 km where area
effects become discontinuous. The discontinuities come with disturbance of
tKe seedbed and the general east to west decline in annual precipitation. The
impacts increase and the time to recover climax increases along the east to
west precipitation gradient.
Recovery from toxic constituents in chemical stabilizers (1-1) used for
temporary "paste down" is expected in two or three years. Mowing (1-2) of
prairie leaves minimum impact and recovery would be expected within the next
growing season.
2-31
-------
o>
ca
o
O X
O) -r-
t. -a
o cu
(u n.
4-> O_
O
, s- -a o -*
V 4-> £ O
-_- U 4J
- o c 01 o
- -r- ig C Ol^H i
-f- C --- CM CM
I eg >r-
o > t-
r- > > CQ
(J (fl -F-
«T3 **- r
3
o
5
O « C\J
2-32
-------
In considering treatments 1-4- through 2-2. those procedures which left
conditions similar to post-agricultural seedbeds (1-4, 1-5, 1-6, 2-1) were
considered to have "typical" successions with the expected upper limit equivalent
for all treatments and the expected lower limit being varied according to per-
ceived potential for minimal impact. Those which were considered to yield impact
in excess of agriculture (1-7, 1-8, 2-2) were assigned potentially longer
recovery periods.
The various mechanical and chemical stabilizers used following cleanup
(2-3 through 2-8) may have significant impacts on early succession but are not
thought to be particularly significant in determining the ultimate length
of the sere. That is, the maximum time to recovery may result from more basic
factors such as soil erosion and minimums in precipitation cycles. The
initial effects of stabilization may become lost before climax vegetation is
established. This is not to recommend for or against stabilization. Stabiliza-
tion decisions should be made on a case-specific basis and based on local
range management, soil science, and road construction expertise and experience.
Treatments 3-1 and 3-2 are essentially "no action" options and, conse-
quently, have no recovery time. This does not imply that there will be no
effect on ecosystems, however (see Section 2.4).
Hard-surface stabilization (4-1, 4-2) represents the greatest potential
impact with the longest recovery times even on the smaller areas to 0.10 km .
Its use is not recommended, therefore, and it is classed as "prohibited" on
prairie.
In general, the smaller the area and the less radical the cleanup treat-
ment the quicker the recovery becomes. The variations in soils, climate, and
local mixtures of plant and animal species make the return to full productivity
a highly site-specific process.
2-33
-------
2.7 CONCLUSIONS
Among the several "preferred" cleanup treatments, in most instances, the
"no action" options (3-1, 3-2) are first choice. Their advantage is in allow-
ing time for careful consideration of possible courses of action with respect
to specific units of landscape that are contaminated. Presumably, it would
be possible to conduct field-plot trials to determine what combination of
alternatives would be the most desirable decontamination procedures. Whether
,the barriers should exclude only people or all animals cannot be completely
defined as a generality. As long as food chains leading to man are isolated
from the contamination, there should be no concern about non-game wildlife
crossing the barriers. Mowing (1-2) represents the second level of ecological
preference.
It is recognized that health and safety considerations may require immediate
and effective action. In such cases, preservation of a seedbed through plowing
(1-5, 1-6) is preferred, especially if the area can be reseeded instead of
relying on natural recovery. Full recovery with reseeding may require fewer
than five years as opposed to up to sixty to eighty years for bare ground
after soil removal.
Soil removal (2-1, 2-2) or deep soil cover (1-7, 1-8) should be considered
last-resort options, when followed by reclamation to reduce recovery times.
The choice between these latter options should be made by local professionals
in soils, range management, and highway construction.
The "prohibited" cleanup treatments in prairie are the variations of hard-
surface stabilization, with asphalt (4-1) or with concrete (4-2). The 30-year
delays caused by their natural breakup require that they be removed bodily
eventually and reclamation procedures instituted. Other contamination cleanup
methods are available which are only moderately damaging to this land type.
2-34
-------
2.8 PRAIRIE REFERENCES
1. Bement, R. E., D. F. Hervey, A. C. Everson, and L. 0. Hylton, Jr. Use
of Asphalt-Emulsion Mulches to Hasten Grass-Seedling Establishment.
Journal of Range Management, 14:102-109, 196.1.
2. Bement, R. E., R. D. Barmington, A. C. Everson, L. 0. Hylton, Jr., and
E. E. Remmanga. Seeding of Abandoned Croplands in the Central Great
Plains. Journal of Range Management, 18:53-58, 1965.
3. Beutner, E. L. and D. Anderson. The Effect of Surface Mulches on Water
Conservation and Forage Production in Some Semidesert Grassland Soils,
Amer. Soc. Agron. J. 35:393-400, 1943.
4. Booth, W. E. Revegetation of Abandoned Fields in Kansas and Oklahoma,
Amer. J. Bot. 28:415-422, 1941. '
5. Buffington, L. C. and C. H. Herbel. Vegetational Changes on a Semi-desert
Grassland Range from 1858 to 1963, Ecol. Monogr. 35:139-164, 1965.
6. Collins, D. Comprehensive Network Site Description, Bridger, US/IBP
Grassland Biome Tech Rep. No. 38, Colorado State University, Ft. .Collins,
1970, 10 pp. -.,-.:
7. Costello, D. F. Natural Revegetation of Abandoned Plowed Land in the Mixed
Prairie Association of Northeastern Colorado, Ecology 25:312-326, 1944.
8. Davidson, E. and M. Fox. Effects of Off-Road Motorcycle Activity on Mojave
Desert. Vegetation and Soil, Madrono 22:381-412, 1974.
9. Environmental Studies Board. Rehabilitation Potential of Western Coal Lands,
Cambridge, Mass., Ballinger, 1974, 198 pp.
10. Gleason, H. A. and A. Cronquist. The Natural Geography of Plants.
Columbia University Press, New York, 1964.
11. Heady, H. F. Comprehensive Network Site Description, HOPLAND, US/IBP
Grassland Biome Tech. Rep. No. 42, Colorado State University, Ft. Collins,
1970, 11 pp.
12. Herbel, C. H. and R. D. Pieper. Comprehensive Network Site Description,
JORNADA, US/IBP Grassland Biome Tech. Rep. No. 43, Colorado State University,
Ft. Collins, 1970, 21 pp.
2-35
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13. Herbel, C. H. , G. H. Abernathy, C. C. Yarbrough, and D, K. Gardner. Root-
plowing and Seeding Arid Rangelands in the Southwest, J. of Range Manage-
ment 26:193-197, 1973.
14. Huddleston, E. W. Comprehensive Network Site Description, PANTEX, US/IBP
Grassland Biome Tech. Rep. No. 45, Colorado State University, Ft. Collins,
1970, 12 pp.
15. Jameson, D. A. General Description of the Pawnee Site, US/IBP Grassland
Biome Tech Rep. No. 1, Colorado State University, Ft. Collins, 1969,
32 pp.
16. Koford, C. B. Prairie Dogs, White faces, and. Blue Grams. Wildlife Monogr.
3:1-78, 1958.
17. Kuchler, A. W. Potential Natural Vegetation of the Conterminous United
States, Amer. Geog. Soc., New York, Special Publ. No. 36, col. map,
95x149 cm, and manual to accompany the map, 1964, 116 pp.
18. Launchbaugh, J. L. Vegetational Changes in the San Antonio Prairie Asso-
ciated with Grazing, Retirement from Grazing, and Abandonment from Cultiva-
tion, Ecol. Monogr. 25:39-57, 1955.
19. Lewis, J. K. Comprehensive Network Site Description, COTTONWOOD, US/IBP
Grassland Biome Tech. Rep. No. 39, Colorado State University, Ft. Collins,
1970, 25 pp.
20. Morris, M. S. Comprehensive Network Site Description, BISON, US/IBP
Grassland Biome Tech. Rep. No. 37, Colorado State University, Ft. Collins,
1970, 23 pp.
21. Noy-Meir, I. Desert Ecosystems: Environment and Producers, Annual Rev.
Ecol. System 4:25-51, 1973.
22. Odum, E. P. Fundamentals of Ecology, Saunders, Philadelphia, 1971.
23. Osborn, B. and P. F. Allan. Vegetation of an Abandoned Prairie-Dog Town
in Tall Grass Prairie, Ecology 30:322-332.
24. Penfound, W. T. Effects of Denudation on the Productivity of Grassland,
Ecology 45: 838-845, 1964.
25. Perino, J. V. and P. G. Risser. Some Aspects of Structure and Function
in Oklahoma Old-Field Succession, B. Tor. Bot. C. 99:233- , 1972.
26. Reynolds, H. G. and F. E. Packer. Effects cf Trampling on Soil and Vege-
tation, U.S. Dept. Agr. Misc. Publ. 940:117-122, 1963.
27. Rice, E. L. and W. T. Penfound. Plant Succession and Yield of Living Plant
Material in a Plowed Prairie in Central Oklahoma, Ecology 35:174-180, 1954.
2-36
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28. Rice, E. L., W. T. Penfound, and L. M. Rohrbaugh. Seed Dispersal and
Mineral Nutrition in Succession in Abandoned Fields in Central Oklahoma,
Ecology 41: 224-228, 1960.
29. Rickard, W. H., and T. P. O'Farrell. Comprehensive Network Site Descrip-
tion, ALE, US/IBP Grassland Biome Tech. Rep. No. 36, Colorado State
University, Ft. Collins, 5 p. 1970.
30. Riegel, A., F. W. Albertson, G. W. Tomanek, and F. E. Kinsinger. Effects
of Grazing and Production on a Twenty Year Old Seeding, J. of Range Manage-
. ment 16:60-63, 1963.
31. Risser, P;. G. Comprehensive Network Site Description, OSAGE, US/IBP
Grassland' Biome Tech. Rep. No. 44, Colorado State University, Ft. Collins,
1970, 5 pp.
32. Roux, E. R. and M. Warren. Plant Succession on Abandoned Fields in Central
Oklahoma and in the Transvaal Highveld, Ecology 44:576-579, 1963.
33. Rumsey, W. B. Range Seedings versus Climax Vegetation on Three Sites in
Idaho, J. Range Management 24:447-450, 1971.
34. Scifres, C. J. and J. L. Mutz. Secondary Succession Following Extended
Inundation of Texas Coastal Rangeland, J. Range Management 28:279-282, 1975.
35. Shantz, H. L. Plant Succession on Abandoned Roads in Eastern Colorado,
J. Ecol. 5:19-42, 1971.
36. Slayback, R. D. and D. R. Cable. Larger Pits Aid Reseeding of Semi-desert
Rangeland, J. Range Management 23:333-335, 1970.
37. Terwillinger,- C., Jr. and J. E. Jensen. Analysis of Range Reseeding
Results, Springfield Land Utilization Project, Colorado Agr. Exp. Sta.,
Colorado State University, Ft. Collins, General Ser. Paper 666, 1957,
16 pp.
38. Tomanek, G. W. Dynamics of Mulch Layer in Grassland Ecosystems, p 225-240,
in R. L. Dix and R. G. Beidleman (ed.). The Grassland Ecosystem: A Pre-
liminary Synthesis, Range Sci. Dept. Sci. Ser. No. 2, Colorado State
University, Ft. Collins, 1969.
39. Tomanek, G. W. Comprehensive Network Site Description, HAYS, US/IBP
Grassland Biome Tech. Rep. No. 41, Colorado State University, Ft. Collins,
1970, 6 pp.
40. Van Dyne, G. M. (Principal Investigator). Analysis of Structure and Func-
tion of Grassland Ecosystems, Colorado State University, Ft. Collins,
2 vols., 1973, 622 pp.
2-37
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41. Weaver, J. E. and W. E. Bruner. A Seven-year Quantitative Study of Suc-
cession in a Grassland, Ecol. Monogr. 15:297-319, 1945.
42. Weaver, J. E., and N. W. Rowland. Effects of Excessive Natural Mulch on
Development, Yield, and Structure of Natural Grassland, Bot. Gaz. 114:
1-19, 1952.
43. Wein, R. W. and N. E. West. Seedling Survival on Erosion Control Treat-
ments in a Salt Desert Area, J. Range Management 24:352-357, 1971.
44. Wells, P. V. Succession in Desert Vegetation on Streets of a Nevada Ghost
Town, Science 134:670-671, 1961.
o
45. White, K. L. Old-Field Succession on Hastings Reservation, California,
Ecology 47:865-868, 1966.
46. Whiteman, W. C. Comprehensive Network Site Description, DICKINSON, US/IBP
Grassland Biome Tech. Rep. No. 40, Colorado State University, Ft. Collins,
1970, 15 pp.
47. Whiteman, W. C., H. T. Hanson, and G. Loder. Natural Revegetation of
Abandoned Fields in Western North Dakota, North Dakota Agr. Exp. Sta. Bull.
321, 1943, 18 pp.
48. Whittaker, R. H. Communities and Ecosystems, Macmillan, New York, 1975.
49. Woodruff, N. P. and F. H. Siddoway. "A Wind Erosion Equation, "Soil Sci.
Soc. mer. Proceedings 29:602-608, 1965.
50. Young, J. A. and R. A. Evans. Downy BromeIntruder in the Plant Success-
sion of Big Sagebrush Communities in the Great Basin, J. Range Management
26:410-415, 1973.
2-38
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CHAPTER 3
DECIDUOUS FOREST
3.1 OVERVIEW
Temperate deciduous forest is a vegetation type in which broad-leaved
trees, the dominant growth form, exhibit an annual cycle of shedding their
leaves and becoming dormant as day length decreases and developing new leaves
and becoming photosynthetically active as day length increases. Deciduous
forest is found in parts of some 33 states in the eastern half of the United
States, including the flood-plain forests which extend, finger-like, deeply
into the prairies. Deciduous forest is bordered by prairie on its western
edge, which extends from Canada to Texas. The border (ecotone) between decidu-
ous forest and prairie is typically savanna, grassland with scattered trees,
comprised of species contributed from each of the two major vegetations (e.g.
Andropogon-Quercus). Moisture limits the western extension of deciduous forest.
The northern boundary is with the Canadian boreal forest with a broad ecotone
of deciduous trees and conifers extending across the great lakes region into
England. The eastern and southern borders are effectively the Atlantic Ocean
and Gulf of Mexico, respectively.
Regionally, precipitation ranges from approximately 76 cm to 152 cm,
annually, and is evenly distributed throughout the year. Locally, such
factors as soil type, aspect, and topography may exert a greater influence on
a
forest type or distribution than gross precipitation.
The deciduous forest of the eastern United States is by no means homoge-
26 8
neous. Kuchler mapped 14 major forest associations, Braun recognized nine
A great deal of variability is contained within either system under native,
undisturbed conditions. Anthropogenic (man-made) changes in vegetation have
greatly increased the variability over native conditions.
3-1
-------
3.1.1 Mixed Mesophytlc Forest
Mixed mesophytic forest is the prevalent forest of the unglaciated
Appalachian Plateau Region of Pennsylvania, West Virginia, Ohio, Kentucky and
Tennessee. Diversity characterizes the mixed mesophytic forest, both in flora
and fauna. The floral dominance is shared by maple (Acer saccharum), buckeye
(Aesculus octandra), beech (Fagus grandifolia), yellow poplar (Lirodendron
tulipifera), white oak (Quercus alba), northern red oak (Q. rubra) and basswood
(Tilia heterophyla). Kuchler listed 26 other tree species as major compon-
ents.
3.1.2 Oak-Hickory Forests
A wide-spread forest type in the central United States, oak-hickory forest
occurs in the drier regions of the deciduous forest biome. Lying west of the
mixed mesophytic forests, it extends in a discontinuous distribution from Michi-
gan to Alabama in the east, to Oklahoma and Texas to the southwest and as
lowland forest into Nebraska and Iowa. Dominant trees are various oaks (Querus
alba, Q. rubra, Q. velutina) and hickories (Carya cordiformis, C. ovata) with
American elm (Ulmus americana), basswood (Tilia americana), black walnut (Juglans
nxgra) and white ash (Fraxinus americana) being important components.
3.1.3 Appalachian Oak-Chestnut Forest
Appalachian oak-chestnut forest includes the Ridge and Valley Province
and the Blue Ridge Province in the south and widens to include much of Ohio,
Pennsylvania and New Jersey, and the coastal plain north to southern Maine.
Since the loss of American chestnut (Castanea dentata) to an introduced fungal
disease, the dominants are white oak (Quercus alba) and northern red oak
(Q. rubra). Maples (Acer rubrum, A. saccharum) and hickories (Carya cordifor-
mis, C. glabra, C. tomentosa) are important, as are black birch (Betula lenta),
beech (Fagus grandifolia) and yellow poplar (Lidrodendron tulipifera).
3.1.4 Oak-Hickory-Pine Forest
Characteristic of the piedmont, this forest type extends west to Texas.
Dominants include various hickories (Carya spp.), shortleaf pine (Pinus echinata),
loblolly pine (Pinus taeda), white oak (Quercus alba) and post oak (Q. stellata).
"o~/l
A rich forest (Kuchler" listed 19 other components), the climatic climax is
3-2
-------
g
probably oak-hickory but much of the region has been dominated by second-growth
pine forests since pre-settlement times. The erodable, red and yellow clay
soils of the region are well-known.
3.1.5 Southern Mixed Forest
This forest type occupies the coastal plain from South Carolina to Louisiana
and into Texas. Much of the region is covered with pine, especially .loblolly
(Pinus taeda) which some authors have considered to be an edaphic (soil
derived) climax. Experimental data have shown, however, that the pines yield
to hardwoods when fire is excluded. Kuchler" listed the dominants as beech
(Fagus grandifolia), sweet gum (Liquidambar styraciflua), magnolia (Magnolia
grandiflora), slash pine (Pinus elliottii), loblolly pine (P. taeda), white oak
O
(Quercus alba) and laural oak (Q. laurifolia). Braun considered the forest
to be transitional to subtropical evergreen forest with northern species drop-
ping out in central Florida and being replaced with more southerly species.
3.1.6 Beech-Maple Forest
The beech-maple forest is found from Indiana to New York, including parts
of Michigan. Mature beech-maple forest presents almost a park-like appearance
with large trees forming a light-extinguishing canopy such that little under-
growth can survive. Beech (^ajjs^jrandjUroHa) and sugar maple (Acer saccharum)
are the dominants with Ohio buckeye (Aesculus glabra), shagbark hickory (Carya
ovata), white ash (Fraxinus americana), black walnut (juglans nigra), yellow
poplar (lirodendron tulipifera), wild black cherry (Prunus serotina), red oak
(Quercus rubra), basswood (Tilia americana), American elm (Ulmus americana),
and slippery elm (U. rubra) being locally important.
3.1.7 Maple-Basswood Forest
Maple-basswood is a limited forest type in northern Illinois, northeastern
Iowa, Wisconsin, and.Minnesota. Sugar maple (Acer saccharum) and basswood
(Tilia americana) are the dominants with northern red oak (Quercus rubra) usu-
ally being present. Other important species include box elder (Acer negundo),
bitternut hickory (Carya cordiformis), red ash (Fraxinus pennsylvanica), Hop-
hornbeam (Ostrya virginiana), bur oak (Quercus macrocarpa), American elm (Ulmus
americana) and slippery elm (U. rubra).
3-3
-------
3.1.8 Hemlock-Hardwood Forest
An ecotone and not a distinct forest type, the hemlock-hardwood forest
stretches from Wisconsin to Maine with islands at higher elevations of the
Appalachians south to Tennessee and North Carolina'. It merits consideration
on size alone. The dominant trees are beech (Fagus grandifolia), sugar maple
(Acer saccharum), yellow birch (Betula allegheniensis) and hemlock (Tsuga
canadensis).
The eight fore'st types described represent what is considered to be the
potential vegetation of significantly large portions of their regions. None
of them was ever homogeneous over their ranges and that is certainly true today.
The vegetation of a region has always been a dynamic concept with climate, fire,
14
and anthropogenic influences producing continuous change
Vegetational development on a particular site has varied with the influ-
ences producing change1 and as new perturbations occur, new developmental
sequences and end points may result . Nevertheless, ecosystem development,
either on new substrate (primary succession) or recovery following disturbance
(secondary succession), follows a course which is highly predictable in gener-
ality, if not in specific cases. The generalities offer a point of reference
and will be discussed first.
3.1.9 Theoretical Considerations
As a forest ecosystem developes, changes take place which convert a com-
munity comprised primarily of small, short-lived, opportunistic species having
little effect on their environment to a community comprised of organisms which
tend to be larger, long lived, and which often exert great control over their
. T C
own environment. Some of those trends were summarized by Odum from which
Table 3-1 is adapted.
A great deal of evidence has been accumulated which supports the generali-
zations in Table 3-1. That biomass accumulates is obvious to anyone who coin-
pares a forest with an abandoned field. Whittaker described a succession on
Long Island, New York (oak-hickory-pine in the system used here) in which
fj
biomass was approximately 1 kg/m in the earliest stages and increased to
between 30 and 40 kg/m2 in the mature forest. Biomass increased sigmoidally
(Figure 3-2) with the result that increasing metabolic demands reduced the
3-4
-------
Table 3-1. Parameter trends during deciduous forest
succession (adapted from Odum35).*
ECOSYSTEM ATTRIBUTE
Biomass
Gross production/respiration
Gross productl on/biomass
Net exosystem production
EARLY SUCCESSION
low
high
high
high
MATURE FOREST
high
low
low
low
(potential yield)
Food chains
Species diversity
Stratification
Size of dominants
Life cycles
Niche relations
Nutrient cycling
Detritus
Overall homeostasis
Stability
simple linear,
mainly grazing
low
little
small
short, simple
Broad, oppor-
tunistic
open
little,
unimportant
poorly developed
low
complex, inter-
connected, detritus-
based
high
much
large
long, complex
narrow, specialized
closed
important
we 11-developed
high
*Terms in this table that are not in Glossary should follow
definitions given by Odum.36
3-5
-------
46
energy available for incorporation into new biomass. Consequently, yield
declines with ecosystem development.
With development in forest ecosystems, an organic layer accumulates on
the forest floor. Prior to the accumulation of this detritus, animal food-
chains are limited to those organisms which can consume the living vegetation
(herbivores and their predators). As the detritus increases, a complex of
microflora and small cryptozoa (literally "hidden animals") begin to exploit
it as a resource base. In a beech forest in Denmark, Bornebusch found an
average of 4424 cryptozoa/m with a biomass of 37.8 g.
There is consensus that species diversity increases during succession
although mature ecosystems tend to be less diverse than younger, transitional
stages. Odum gave an example of a forest which attained maximum diversity
at an age of almost 160 years with diversity declining beyond that. Whittaker
gave as an example a forest which attained maximum diversity quickly, in about
8-10 years, and declined gradually as the ecosystem developed. It is accepted
that maximum diversity is attained during tha transition from one more-or-less
discrete successional stage to another when species belonging to each state
coexist in the same area. Consequently, in the example given by Odum maximum
diversity apparently occurred during the transition to a mature forest, the
usual case, and in the example given by Whittaker maximum diversity occurred
during the transition from the herb to shrub stages.
Stratification, layering in the forest, is a correlate of species diver-
sity. The generalized sequence of herb to shrub to tree dominance is, in
effect, the adding of layers which add species to the community. Bird species
reflect the effect of increasing stratification perhaps most clearly. Johnston
and Odum21 reported two breeding bird species in a three-year-old field having
a grass-forb dominance, 13 species for the local oak-hickory-pine climax. The
size of dominants and their life history complexity also are correlated with
increased diversity and stratification as succession proceeds to climax.
Bazzaz reported that Solanum carolinense, Ambrosia artemisiifolia, and
Digitaria sanguinales, all low-growing annuals (plants which complete their
life cycles in one season), were established in a cornfield before the first
winter after abandonment. Climax for the area was oak-hickory with Quercus
velutina being the major dominant.
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Early successional stages are said to have open nutrient cycles in
which the nutrient elements are primarily extrabiotic (outside of organisms
and their products). Mature stages are said to have closed cycles in which
detritus serves as a critical link between uptake and loss of nutrients from
vegetation. Vitousek and Reiners examined this hypothesis and found that
for elements which have atmospheric inputs to ecosystems, outputs from the
ecosystem in the form of stream discharges were low during the rapid growth of
early succession and increased with maturity to where element input and output
were approximately equal. Thus, it may be concluded that uptake in mature
forests is in equilibrium with release of elements from organic matter. Thus,
constancy characterizes mature ecosystems, and represents a measure of sta-
bility and homeostatic control.
Two categories of perturbations have occurred during the history of
deciduous forests which may yield insight into the impacts of spill cleanup.
Natural perturbations and anthropogenic (man-induced) perturbations are not
always distinct from each other, however. An example of where they overlap is
fire. Fires have occurred naturally throughout the history of deciduous
forests but, observing the changes that fire brought to deciduous forest
ecosystems or their utility as hunting tools, the American Indians would
12
deliberately set fires. Thus, inclusion of fire as a "natural" perturbation
is somewhat arbitrary.
3.2 NATURAL PERTURBATIONS
3.2.1 Fire
The role of fires in ecosystems has recently been summarized. Lightning
has been the primary source of naturally occurring fires although man has been
setting fires in North America for an estimated 20,000 years. The primary
difference between natural or lightning fires and set fires is the seasonality.
Electrical storms are essentially summertime phenomena, occurring when overall
combustibility is typically low. Set fires can occur at any time and thus are
potentially more destructive. It is probable that the grass fields of central
Kentucky described by Clark were maintained by frequent fires set by Indians.
Early succession following complete forest removal by fire in Finland
was qualitatively similar to succession following other massive perturbations.
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The pioneer invaders were reselected, annual species with windborne seeds,
such as dandelion (Taraxacum officinale) hawksweed (Hieracium spp.). a"d fire-
weed (Chamaenerion angustifolium). Other early invaders, such as raspberry
(Rubus idaeus), were carried by birds. An herb stage was evident after 3 years
and grasses were dominant by the sixth year.
Henry and Swan reconstructed a 300-year sere (successional sequence) in
New Hampshire from evidence contained in the soil and trees growing on the site.
From charcoal and partially burned wood found in soil and from the ages of the
oldest trees in the forest, they concluded that a massive fire had destroyed
the forest in about 1665. They were able to identify eastern white pine (Pinus
strobus), white oak (Quercus alba), hemlock (Tsuga canadensis), spruce (Picea
sp.), red maple (Acer rubrum), and aspen (Populus sp.) as components of the
~
destroyed forest, species found in the region today. Herbaceous or short-
lived early invaders left no records, but the ages of extant trees allowed
them to reconstruct the succession of tree species. White pine (Pinus strobus)
was the first tree invader, coming in between 1665 and 1687 and producing a
distinct pine forest stage. Hemlock (Tsuga canadensis) invaded between 1684
and 1780, paper birch (Betula papyrifera) in 1742, 1770 and 1795, red oak
CQuercus rubra) between 1790 and 1860 and beech (Fagus grandifolia) began
entering slowly in 1815. Thus, it took 150 years for the dominants of the new
climax forest to appear and possibly another 50 to 100 years for them to estab-
lish dominance. Consequently, in New Hampshire, it may take up to 250 years
for a mature forest to reestablish itself following a massive perturbation,
such as complete consumption by fire. Furthermore, minor perturbations,
such as wind-felling of trees during some 250 years, can open patches of forest
at different successional stages, and consequently different environmental con-
ditions, which permits the invasion of still further tree species which will
determine the ultimate composition of the forest. Therefore, specific predic-
tions cannot be made about the ultimate consequences of a particular gross
perturbation.
Other fires, which remove the understory of forests without seriously
injuring the dominant trees, have no correlate among the proposed clean-up
procedures and will not be treated.
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3.2.2 Primary Succession^
Primary successions occur where no ecosystem has previously existed, such
as on newly-created volcanic land. Land masses within the eastern deciduous
forest region have been remarkably stable for thousands of years and, conse-
quently, primary successions are poorly understood. Surface mining using over-
burden for reclamation, may produce a substrate which can lead to essentially
a primary succession. Costly mandatory rehabilitation bonds, for contouring
spoil banks to avoid instability and slope failure, exert economic pressure
for "natural recovery." Information on the probable years for primary succes-
sion, on surface-mine spoil banks, becomes vital to predict the years to com-
plete rehabilitation.
A case history of primary succession was developed by Morrison and
Yarranton ' for sand dunes. They have identified three stages in primary
succession. The first stage or colonizing stage lasts up to 1600 years and is
characterized by beachgrass (Ammophilia breviligulata), balsam poplar (Populus
balsamifera), willow (Salix glaucophylloides), and sand cherry (Prunus pumila).
The colonizing stage is followed by a transition stage lasting another 1300
years and characterized by scattered trees without canopy closure. The typical
species are hybrids of red and black oaks (Quercus rubra x velutina), fragrant
sumac (Rhus aromatica), choke cherry (Prunus virginiana), a sedge (Carex lan-
guinosa) and snowberry (Symphoricarpos racemosus). That is followed by a
persistent stage lasting at least 1900 years and comprised of white oak (Quercus
alba), New Jersey tea (Ceanothus americanus), black cherry (Prunus serotina)
and teaberry (Gaultheria procumbens).
The number of species apparently increases to a stability point approxi-
mately 2000 years after the dune is formed while frequency continues to increase
throughout the 4800 years, which is too long to wait.
3.3 MAN-MADE PERTURBATIONS
3.3.1 Surface Mining
Although not nearly as extensive as clearing for agriculture, surface
mining represents a massive perturbation which is both highly visible and
difficult to ameliorate. The mine spoil which typically finds its way to the
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surface is analogous to a new land surface and, consequently, natural succes-
sions on mine spoil somewhat resembles primary successions. Since no
4800-year-old mine spoils have been identified, there is no evidence that the
two are directly parallel. A further complication is the acidity problem
shared by the central and Appalachian coal fields. In these areas, iron disul-
fide is exposed to air, oxidizes and produces sulfuric acid. Spoil pH is often
too low to support plant life and the low pH tends to increase the solubility
of a number of metal ions which reach toxic levels. None of the proposed
cleanup procedures is likely to expose appreciable quantities of these acid-
forming disulfides. Once the pH of surface mine spoils is adjusted, the plant
substrate is possibly quite similar to the product of cleanups, particularly
on shallow soils. Therefore, examination of the revegetation history of mine
spoils may provide a model of the consequences of some cleanup procedures.
Surface mining in the eastern United States, especially in the rugged
topography of Appalachia, has created problems of water runoff, erosion, and
sedimentation which have led to extensive studies and actions directed toward
stabilizing spoil surfaces through soil amendments and revegetation. Conse-
quently, there exists at least some data both on natural revegetation and
reclamation. In general, low pH inhibits both reclamation and natural recovery.
If pH is not limiting, planting can greatly accelerate early recovery. One
study estimated that replanted spoil was as much as 10 years ahead of untreated
18
spoils after only 3 years.
Untreated spoil often does revegetate naturally, however. One of the
29
earliest reports of natural revegetation was by McDougall who reported on
revegetation of surface-mined bottomlands in Illinois. He concluded that
proximity to a seed source was an overriding factor in the invasion rate of
species. He described a sere which began with annual weeds, such as knotweeds
(Polygonum aviculare and P. persicaria) with occasionally barnyard grass
(Echinochloa crusgalli) and giant ragweed (Ambrosia trifida) in furrows. The
drier ridges contained sweet clover (Melilotus alba), aster (Aster ericodes),
sunflower (Helianthus hirsutus and H. decapetalus), ragweed (Ambrosia artemi-
siifolia), evening primrose (Oenothera biennis), black mustard (Brassica
nigra) and prickley lettuce (Lactuca scanola). Pioneer woody species included
willow (alix nigra) and cottonwood (Populus deltoides), if a seed source were
available. They were followed by seedlings of the forest-stage species:
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silver maple (Acer saccharinum), elm (Ulmus aroericana) and sycamore (Platanus
occidentalis). He stated that a 25-year-old strip mine was covered with "well-
established bottomland forest."
Croxton reported on revegetation of strip-mined lands in the same region
of Illinois and found evidence of the variability of results which have come
to characterize such areas. He attributed the rapid recovery of the site
studied earlier by McDougall to the deposition of river alluvium over the spoil
and the creation of unusually favorable conditions. The sere he reported was
essentially the same as that reported by McDougall, allowing for availability
of various weed seeds. He indicated that recovery within 25 years was unusually
rapid and that areas with pH below 4.5 failed to revegetate. He noted that the
old-field shrub stage of succession, which is characteristic of deciduous
forests, was poorly represented on mine spoil,,
A distinct shrub stage was reported on mine spoil in southern Indiana.
Beginning approximately 7 years after abandonment of the spoils, the stage
contained sumac (Rhus sp.), honeysuckle (Lonicera japonica), trumpet vine
(Campsis radicans) and poison ivy (Rhus radicans). Included in the.shrub
stage were saplings of cottonwood (Populus deltoides), river birch (Betula
nigra), persimmon (Diospyros virginiana), sycamore (Platanus occidentalis),
sassafras (Sassafras albidum), slippery elm (Ulmus rubra), black cherry
(Prunus serotina), flowering dogwood (Cornus florida) and shingle oak (Quercus
imbricaria). By 11 years after abandonment, a tree layer had developed and . ,
by 21 years pin oak (Quercus palustris) and persimmon were the dominant species.
The conclusions to be drawn from these studies of early succession on
strip-mine spoils are that natural revegetation can occur if soil conditions
permit and that the rate and pattern of recovery is highly variable. The
variability is primarily the result of the complexity of the plant growth
medium resulting from mining and the variability of the seed source in the
40
surrounding area.
Revegetation of strip mine spoil has emphasized establishment of ground
cover and the prevention of erosion. Species planted, such as sericea les-
pedeza, have been selected for their ability to quickly establish ground cover
with the expectation that they will eventually be replaced by natural inva-
sions of local species. For the most part, workers have been satisfied with
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achieving their primary objective. Long-term studies which seek to evaluate
the return of such disturbed lands to pre-mining ecosystems are virtually non-
existent, although "full-growth" of "high-grade" forests has been achieved
within 50 to 70 years.
3.3.2 Post-Agrlr iltural Successions
Secondary succession following the abandonment of agricultural land is
the best-known, example of ecosystem development in deciduous forests. Clearing
of unproductive land; changing markets, and loss of fertility has led to aban-
donment of land throughout the deciduous forest. That abandonment began almost
as soon as settlement began and continues into the present. Consequently,
virtually all aspects of succession have received at least some study. For
convenience, a regional approach will be taken.
3.3.2.1 Southeastern States
Succession on the Georgia piedmont has been studied by Nicholson and
Monk ' who identified 5 major stages. Their "early forb stage" occupied
the first 10 years following abandonment and was dominated by perennial grasses
(Andropogon scoparius, Aristida purpurascens, Eragrostis sp.) and forbs (Allium
vineale, Erigeron canadensis, Haplopappus devaricatus, Cassia nictitans, Heter-
otheca subaxillaris, Aster pilosus, Solidago sp., Lespedeza sp.). Chickasaw
plum fPrunus angustifolia) and brambles (Rubus spp.) formed a shrub layer along
with tree seedlings (Pinus taeda, P. echinata, Diospyros virginiana, Celtis
occidentalis, Rhus copallina) and vines (Lonicera japonica, Smilax bona-nox,
Wisteria sinensis, Campsis radicans). This is followed by what they called
a. "broomsedge stage" in which Andropogon scoparius increases its cover and
community richness declines. The broomsedge stage lasted from the tenth to
the twentieth year following abandoment. The old-field shrub stage replaced
the broomsedge stage and persisted up to approximately 30 years after aban-
donment. Loblolly pine (Pinus taeda) and sweet gum (Liquidambar styraciflua)
increase as shading, soil moisture and soil organic matter increase. Species
richness increases in all strata except the herb layer, which declines due to
shading and litter accumulation. The end of the stage is identified by canopy
closure (approximately 30 years) and the reduction of the herb stratum to about
percent of the open-field level.
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Canopy closure* signals the start of the pine stage in which loblolly
pine is the dominant. The stage lasts approximately 70 years (30 to 100 years
post-abandonment) and there is a slight decline in total above-ground biomass
for the first 60 years. Woody species increase in the understory as broad-
leaved deciduous species invade. Maximum richness occurs as the species from
early succession overlap with the tree species of the later climax and subcli-
max forests, around 70 years post-abandonment. Richness declines as hardwoods
replace the pines (100 to 125 years) to increase again around 150 years as new
hardwood species appear. The hardwood stage lasts from 100 years, post aban-
donment, to 200 years or more.
Johnston and Odum reported on breeding bird populations of the Georgia-
piedmont sere. They found that both density arid diversity increased with suc-
cession up to the pine stage where each declined sharply. Only one species,
the pine warbler (Dendroica pinus), used the pine overstory, but other species
came in as the hardwood understory developed. Approximately 12 species with
140 breeding pairs/40 ha (100 acres) were present before canopy closure and
this dropped to 10 and 17 at 20 years. The maximum attained was 20 species
and 240 breeding pairs/40 ha in the transition forest with 23 and 220 in the
deciduous forest stage. Only the cardinal (Ric.hmondena cardinalis) was present
in all stages with most bird species being stage-specific.
On the North Carolina piedmont, short-leaf pine (Pinus echinata) domin-
ates the pine stage with up to 7400 stems/ha (3000 stems/acre). The first
oaks (Quercus spp.) appear at about 20 years with the first hickories (Carya
spp.) only a few years later. The sequence during the first 3 years was given
by Keever. Crabgrass (Digitaria sanguinalis) is able to invade plowed fields
in the fall of the year of abandonment because of its drought resistance and
ability to germinate under cool soil temperatures. Horseweed (Leptilon cana-
dense) may germinate at about the same time but grows to maturity the follow-
ing summer. Horseweed and ragweed (Ambrosia elatior) dominate one-year-old
fields with germination of new horseweed seeds being inhibited by the decay
products of the parent plants. An aster (Aster pilosus) appears the first
year and becomes a dominant the second, along with ragweed and buttonweed
*See Glossary for definitions of terms.
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(Diodia teres). A few broomsedge (Andropogon virginicus) plants appear the
plants appear the first year but require 2 years to set seed. They become
dominants by the third year.
On the Virginia piedmont, Virginia pine (Pinus virginiana) dominates the
pine stage producing a closed canopy within 10 to 20 years. They mature within
19
50 to 70 years.
Further inland, the old-field stage in middle Tennessee is characterized
by elm (Ulmus americana) and hackberry (Celtis occidentalis) with an under-
story of broomsedge (Andropogon virginicus), goldenrod (Solidago altissima),
39
aster CAster pilosus) and panic-grass (Panicum sp.) . Sassafras (Sassafras
albidum) may be a component of old-fields and, because of allelopathy, may
persist in pure clones into the mature forest.
17
3.3.2.2 Northeastern States--
Long-term succession in New England has been described earlier.*' Bard'
described secondary succession on the New Jersey piedmont. The first-year
dominants were ragweed (Ambrosia artemesiifolia) and evening primrose (Oeno-
thera parviflora) with later dominants represented. They were replaced in the
second year by a goldenrod (Solidago nemoralis). S. nemoralis remained impor-
tant for 15 years when it was replaced by S.. juncea which persisted for another
45 years or more. By the fifth year, an aster (Aster ericoides) became the
dominant herb and remained important for another 20 or more years. Fifteen-
year-old fields were dominated by broomsedge (Andropogon scoparius with A.
virginicus) which remained important for another 45 years. Eastern red cedar
CJuniperus virginiana) is among the first woody invaders (2- to 3-year-old
fields) .-and is the major arborescent species for more than 60 years. Dominant
shrubs are brambles (Rubus flagellaris) which reach their peak 25 years after
abandonment and poison ivy (Rhus radicans) which is most abundant 60 years
after abandonment. The trees of the climax oak-hickory forest enter before
the red cedar is mature and are well established in the understory by the
sixtieth year after abandonment. Recent evidence indicates that allelopathy
is important to the early replacement of species. Aster pilosus, a second-
stage dominant, was shown to produce a chemical which inhibited germination
of first-stage dominants.
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There is a succession of animals which follows the plant succession
25
Kircher" showed that bird diversity increased with each serai stage and that
there was a gradual shift during succession from species which used the area
for feeding only to species which nested in the area. Pearson37 reported that
small mammals increased with early succession but declined as the forest be-
came established.
At least occasionally, the orderly replacement of species becomes delayed
when one or more species establishes a stable, persistent community prior to
the expression of climax. Examples include speckled alder (Alnus rugosa)
for 20 years or more, witch-hazel (Hamamelis. yirginiana) for 40 years, nanny-
berry (Viburnum lentago) for 45 years, and meadowsweet (Spiraea latifolia),
highbush blueberry (Vaccinium corymbosum), lowbush blueberry (V. angustifolium),
arrowwood (Viburnum recognitum), sweetfern (Comptonia peregrina) and common
juniper (Juniperus communis) for 47 years. Thus, the typical succession cannot
be expected in every instance. Nor is it possible to predict the frequency of
occurrence or duration of stable shrub stages.
3.3.2.3 Central States--
Early succession in southern Illinois was described by Bazzaz. Follow-
ing the harvest of corn in August, cover was provided by weeds already estab-
lished, including Solanum carolinense, Ambrosia artemisiifolia and Digitaria
sanguinalis. During the first growing season following abandonment, annuals
(plants which complete their life cycle in a single season) were the dominant
vegetation and included Alliumvineale, Digitaria sanguinalis, Geranium maculatum
and Aster pilosus. Sawbrier (Smilax glauca) was the first woody plant to be-
come established. Total ground cover was approximately 65 percent.
Perennials (plants which live for several years) were the dominant vege-
tation by the second year of abandonment. Erigeron annuus flowered in early
suBimer, when it v/as the conspicuous, dominant, and Aster pilosus was most con-
spicuous later in the summer. Ground cover attained approximately 115 percent.
By the third year, erosion had reduced ground cover to approximately 85
percent, but the species replacement pattern continued. Herbaceous vegetation
had begun to develop strata with goldenrod (Solidago nemoralis) dominating
the upper stratum and panic grass (Panicum dichotomum) and three-awn (Aristida
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dichotoma) codominant in the lower stratum. Old-field shrubs began invading,
including black raspberries (Rubus occidental is) and persimmon (Diospyros
virginiana).
Four-year-old fields had produced a stable herbaceous community, dominated
by broomsedge (Andropogon virginicus). The developing shrub layer contained
persimmon, sassafras (Sassafras albidum). elm [Ulmus alata), eastern red cedar
(Juniperus virginiana) and sumac (Rhus spp.). Cover (all strata summed) had
increased to 119 percent, with 8 percent being contributed by shrubs. Vegeta-
tion of 10- and 15-year-old fields remained similar in composition with the
shrubs growing to a cover value of approximately 16 percent. By the 25th year,
the older sassafrass and persimmons had produced a tree layer with the composi-
tion of the shrub and herb layers as before.
By 40 years after abandonment, the tree layer had reached a basal area of
about 15.6 and the shrub layer had increased to 21 percent. Broom sedge still dom-
inated the herb layer. Elm and sumac remained the dominants in the shrub layer
but a few seedlings of the climax oaks (Quercus imbricaria and Q. velutina) had
appeared. A total of 22 species occurred in the tree layer with sassafras and
persimmon remaining the dominants.
The rate of invasion of the climax oaks was considered to be dependent
on the proximity to mature forest,, since the seeds were dispersed by squirrels
which prefer the forest edge. Diversity increased throughout the succession
to a maximum in the forest stage4 but may be low when allelopathic species are
present. Environmental heterogeneity produces a variety of seres within a
given area.
42
The animals which occupy serai stages change with the vegetation. Sly
reported that deer mice (Pereomyscus maniculatus) occurred in the early, grass
stage of successions while the white-footed mouse (P. leucopus) occurred in
the later, forest stages. The two species overlapped during the old-field or
grass-shrub stages. Serai stage is not the only determinant of acceptability
to wildlife, however. Beckwith5 concluded that the size of a tract of other-
wise suitable vegetation would influence whether or not game animals would be
found there.
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3.4 CLEAN-UP PROCEDURES, EFFECTS ON ECOSYSTEMS
This section describes the effects that the proposed cleanup methods can
be predicted to have on deciduous forest ecosystems. The description is quali-
tative for each treatment's impact in the ecosystem. A quantitative assessment
of all the cleanup methods is deferred to Section 3.6, after the impact is
described and the likely time course of recovery is given (Section 3.5). The
cleanup treatments range in severity from a light spray, of "tacky" chemicals
over the vegetation and soils, to severe impacts caused by removing vegetation
and topsoil, mixing the subsoil with caustic chemicals and compacting the mix-
ture with cementing agents.
(0-1) Natural Rehabilitation
For manual cleanup of contamination, no significant impact on the prairie
is anticipated to be evident after 2 or 3 years.
(2-1) Chemical Stabilisation
Properties of the two general classes of chemical stabilizers are given
in Appendix A, Stabilizers. Twenty-seven are rated "preferred" for reducing
soil erosion under normal rainfall regimes in the deciduous forest. Six allow
seed to germinate in place but they break down in a year. Four of the six
chemical stabilizers are safe to handle without special equipment, in machine
or hand sprayers. Significant leaf fall from shrubs and trees is caused by
the four stabilizers but little damage to roots is expected.
The application of stabilizers that kill vegetation is acceptable when
vegetation to which they are applied must be removed in some of the cleanup
methods described in subsequent discussion (treatment 1-3). In general, the
pi ant -damaging stabilizers leave a more weather-resistant and erosion-inhibiting
coating over soil surfaces.
(1-2) Clear Cutting Vegetation
Clear cutting deciduous forest is used in forest management. Clear cutting
or block cutting permits reproduction from nearby forest trees, but public ac-
ceptance has been a major obstacle to the practice.
Clearcut forests revegetate in two ways. First, many species have the
ability to produce sprouts from the stumps and roots of the former trees.
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Since the remaining root network is essentially that of a mature tree, sprouts
typically show exceedingly rapid growth. A coppice forest, which clear-cutting
produces, can produce canopy closure in a decade or two. Since growth is from
the remains of the former forest, species composition is typically quite similar.
In addition to sprouts, the opening of a forest by clear cutting allows for
invasion of pioneer species and an abbreviated version of old-field succession.
The resultant, short-lived heterogeneity is attractive to game species. Those
pioneer species which grow rapidly enough and can survive canopy closure add
to the diversity of the resulting forest. Consequently, coppice forests may
differ in that respect from the original forest.
(1-3) Sturrping and Grubbing
Removal of stumps and roots blocks the formation of a coppice forest and
results in longer recovery times. A natural succession would be similar to
post-agricultural recovery and include the typical annual-perennial-shrub-tree
sequence of dominants. The rate at which these stages replace each other will
depend on what seeds were present in the soil prior to cleanup, the size of the
affected area and erosion. This treatment will differ from post-agricultural
land in that the seeds of species present when the treatment began can be ex-
pected to remain behind. The time-lag before the climax species appear as
seedlings would thus be reduced to about a year and the total ecosystem de-
velopment reduced accordingly. Thus, the up to 250 years required for reaching
climax following agriculture might be reduced to 100 years or less. Assuming
that the forest removed was not climax but an earlier successional stage, the
time required for recovery to that point would likewise be shortened, with
the exception of early shrub stages. Since woody shrubs appear very early in
succession, typically the first or second year, and require several years to
attain dominance, no shortening of that interval would be expected.
The size of the affected area influences the invasion rate from outside
the area. Small (i.e., 0.1 km ) areas have large perimeter to area ratios
compared to large areas (i.e., 10.0 km ). Since squirrels prefer forest
edge,3 acorns could be expected to be buried over the smaller areas more quickly
than the larger one with a proportional recovery of oaks.
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Uncontrolled erosion can act as a recurring perturbation which continually
sets back recovery in the cleaned-up area to an earlier stage, and can expand
the perturbation beyond the spill zone. Thus, presence of erosion will result
in longer recovery times and larger perturbations.
(1-4) Sprccping and Grading
In a forest, scraping and grading requires that stumps first be removed.
In addition to the effects of stumping and grubbing (1-3), scraping and grading
(1-4) would remove the surface organic matter that remained. That would result
in higher soil temperatures, decreased infiltration of water, increased runoff
and erosion and nutrient depletion. As a result, recovery times could reason-
ably be expected to be longer than with stumping and grubbing (1-3) alone, but
not as long as required for post-agricultural recovery since some seeds would
remain in the soil. The pattern of recovery would be expected to remain the
same with the size of the area affecting the rate as well. It has been found
in strip-mine reclamations that scraping and grading (1-4) delays recovery
relative to a rough surface, primarily because of a reduction in infiltration
and an increased risk of erosion.
(1-5) Shallow Plow-Crip
Shallow plowing (<10 cm) following stumping and grubbing would probably
have no observable effect on ecosystem recovery beyond that of vegetation re-
moval. The surface organic matter would be incorporated into the soil and
seeds redistributed, but the long-term effects would not likely be discerible.
The effect would be less than soil removal because the seeds and organic matter
would remain and because the resulting pattern of ridges and furrows would trap
water and decrease erosion.
(1-6) Deep Plowing
As recently as the early 20th century, farmers in the deciduous forest
zone cleared and planted "new ground." Trees were killed by girdling and then
felled and usually burned. The farmers then plowed their fields, although
cutting through the buried roots was punishing to both mule and man. They
plowed partly out of tradition and partly to keep down weeds, that is, to pre-
vent natural succession. Deep plowing as a cleanup procedure will do the same,
except being done only once the effect will be shorter-lived. Thus, deep plow-
ing on deep soils may delay early succession a year or two. Deep plowing on
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shallow, hill soils can be expected to have a longer-lasting effect, if it can
be accomplished at all. In either case, the effect will be less than grading
or soil removal, since the quality of the seed bed remaining should be superior
to that left by soil removal and the ridges and valleys will retain precipita-
tion. The succession should be no slower than post-agricultural successions
on similar soils.
(1-7) Soil Cover Less than 25 cm
The addition of,;'-uncontaminated soil to a forest floor has several potential
effects, not the least of which is the disruption of vegetation by the applica-
tion of the soil. One acre-furrow-slice (the soil of one acre to a depth of 6
inches) weighs 2,000,000 pounds or more. Therefore, covering 0.01 km with
25 cm of soil would require at least 3.7 x 106 kg (8.2 x 106 Ibs or 4 x 10
tons) of soil and up to 3.7 x 10 kg for 10.0 km . Such large masses of soil
require heavy earth-moving equipment which cannot be operated in a forest with-
out first removing or knocking down the trees. It must be assumed, therefore,
that any soil additions will be done after the forest is removed.
Twenty-five centimeters of soil or less would not cover the fallen boles
and stumps of mature deciduous trees, leaving the possibility that at least
some of the trees might resprout from unkilled tissues. The severity of the
impact then would lie somewhere between that of a clearcut forest, assuming
a greater kill rate, and surface alterations. Herbaceous material would be
buried below an effective recovery depth and the seeds present on the forest
floor would be too deep to germinate. Consequently, recovery would consist
of a combination of resprouting of the former trees and invasion of pioneer
species, including the seeds carried in the uncontaminated soil. As such, re-
covery rate would depend upon the area disturbed, which affects the invasion
rate of trees, the kinds and amounts of seeds contained in the imported soil,
the seed-bed quality represented by the imported soil and sprouting rate of
the fallen trees. All of these interact to produce a range of variables which
greatly diminishes predictability.
(1-8) Soil Cover 25 to 100 am
Covering with additional soil primarily magnifies the problems identified
in the previous section. As depth of added soil increases, the probability of
resprouting of fallen trees decreases. A full 100 cm of soil would cover most
3-20
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of the fallen boles, and many of the uprooted stumps. Resprouting cannot, be
completely ruled out as a recovery factor, however.
Since noncontaminated soil must be excavated elsewhere, it is safe to
assume that seed-bed quality will decline with the area and depth to be covered.
That is, constraints on disturbing noncontaminated areas will require the de-
contamination crews to dig deeper at the borrow site as volume demand goes up
rather than to increase the area disburbed. In most regions, that translates
as a lower quality seedbed. Thus, recovery time may be expected to be extended
as area treated and burial depth are increased. Quality of the seedbed would
be the primary factor affecting early recovery with the size of the area dis-
turbed affecting later rates of invasion by trees.
The level of impact would be expected to be greater than that of vegeta-
tion removal, surface alteration, plowing, and possibly soil removal. The one
ameliorating factor would be resprouting of fallen trees, if it were to occur.
The environmental costs of disturbance to the borrow sites must be factored
into any cost-benefit analysis of burial procedures. For;even the smallest area
23
considered (0.01 km ), 2500 m soil would be required for burial to 25 cm and
10,000 m soil would be required for burial to 100 cm. Because of the desire
to minimize the area affected, the impact on the borrow site would be greater
than that of any of the cleanup procedures considered, with the exception of
hard-surface stabilization.
(2-1) Remove Plow Layer '-...
The effects of removing the plow layer, approximately 15 cm (6 inches)
of soil, depend upon topography, soil type, and what other cleanup procedures
are done in conjunction. Deciduous trees, growing in forests, have roots in
contact with the surface organic layer. This is where the active exchange of
nutrients occurs. Assuming it is possible to remove the top 15 cm (6 inches)
of soil without first removing the trees, it is probable that no tree would
survive the cleanup. While the presence of standing, dead trees would not be
expected to interfere with recovery, they would also not expedite it, leaving
no justification for not removing them.
Assuming removal of the plow layer to follow stumping and grubbing, the
pattern or recovery would be that of, at best, a post-agricultural succession
or, at worst, a strip-mine spoil. All plants would have to invade from outside
3-21
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the area making the size of the affected area important. If the cleanup were
to occur on nearly level topography having well-developed soils, the remaining
seed bed could be of high quality. In steep terrain, however, forest soils
typically have a very thin (less than 15 cm) layer of topsoil which would be
removed entirely. The resulting seed bed would resemble mine spoil and eco-
system recovery could be expected to be accordingly slow. Subsequent chemical
and most types of mechanical subsoil stabilization have little added impact
but would minimize erosion in the short term recovery.
(2-2) Remove Shallow Root Zone
In deciduous forest, shallow root-zone can be interpreted to be a plow
layer or less. At any rate, soil removal is also seed removal and the early
colonizations must be from outside of the affected area. Increasing the depth
of soil removal lowers the probability of leaving a suitable seed bed and in-
creases the time necessary for recovery. Whereas canopy closures can occur
32 33
within 30 years in post-agricultural successions, ' such rapid recovery is
13
unusual following surface mining which is analogous to soil removal on shallow
soils. Use of chemical and mechanical stabilizers to prevent erosion would
mimic post-agricultural recovery.
(2-3) Remove Scraping and Grading, Mechanically Stabilize
As the sizes of stabilized areas increase more internal structures are
needed for overland water control. These include dikes, berms, drainage
ditches, shaped waterways and overfall structures on steeper-grade channels
which are all beyond the scope of this presentation.
The specific consequences of scraping and grading (1-4) were presented
earlier and apply to the pre-stabilized deciduous forest. Denuded areas-
depend on early reseeding by native plants. A smoothed and compacted surface
having reduced water permeability is the medium represented after erosion
control by stabilization.
Mechanical stabilization may involve compaction, meshes, mulches, defloc-
culants, and clays. The effects of mechanical soil compactors remain evident
for many years. Complete recovery will seldom occur by 100 years. Simple
ground cover by plant invaders will take up to five years and succession may
be delayed 25 or 100 years compared to simple clear-cutting. Heavily compacted
3-22
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areas are subject to repeated regressive cycles following erosive denuding of
large open areas. Infiltration can readily be reduced to an inch per hour or
less and offsite runoff is a serious problem at even one hectare of clearing
and surfacing.
Non-compacting stabilization by meshes and mulches is indicated for the
cleared, deciduous forest and is the method rated in Table 3-2 (see Section
3.6). This assumes that mesh is held down by pegs (non-metallic if mowed) on
steep slopes and anchored to prevent wind detaching or under-running sections.
Mulches are anchored by tractor disc or cleats in areas free of significant
water erosion.
Deflocculants and clays have characteristics that produce impacts inter-
mediate among soil compactors and the various mulches. They are subject to
frost heaving damage and are relatively short-lived since seeds can collect
and germinate in the breaks. Deflocculants depress the early growth of plants
by salt effects in germination and rooting compared to clays.
Significant damage by small rodents is probable in a few months for any
of the chemical and mechanical stabilizers used after soil removal.
(2-4) Remove PloD Layer, Mechanically Stabilize
The ecological impacts were described in scraping and grading (1-4) and
the effects of stabilizing the exposed soil mechanically were defined in
treatment 2-3. In general, natural recovery will be delayed compared to re-
moving 5 cm or less of soil, by removal of more seed sources and mechanical
stabilization will seriously retard revegetation compared to clear cutting.
(2-5) Remove Shallow Root Zone, MeahoLnicallij Stabilize
This treatment has effects almost identical to plow layer removal (2-1).
Soil fertility is reduced by deeper cuts and the potential for natural revege-
tation shifts to favor invaders instead of local pioneer species. The subsoils
will tend to be more erosive than surface layers due to reduced organic matter
and so require heavier applications of stabilizers. Higher clay content will
increase density under compaction and exacerbate water erosion. Non-compacting
stabilizers are much superior in this case.
3-23
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(2-6) Remove Scraping and Grading, Chemically Stabilise
The physical effects and the ecosystem impact of removal of scraping and
grading (2-6) were described under treatments 1-4 and 2-3. The effects of
chemical stabilizers are less durable than those of mechanically stabilized
soils and require prompt revegetation, usually by herbs 'and grasses in the
clearings made. Either class of stabilizer reduces surface erosion, increases
runoff, and has specific effects on water infiltration according to the spe-
cific stabilizer and its limits of use (Appendix A, Stabilizers).
Chemical stabilizers for soil stabilization control soil erosion while
seedlings become established then the "preferred" stabilizers break down.
Overland runoff is reduced by these compounds compared to soil compaction
treatments. Stabilization with chemicals will reduce erosion of the exposed
soil horizons and should allow early revegetation of native pioneer species.
(2-7) Remove Plow Layer, Chemically Stabilize
The effects of removal of the plow layer (2-1) are combined with those of
treatment 2-6. The deeper soil cut reduces the seeded zone to those hidden by
small animals and exposes the infertile subsoil as the plant growth medium.
It presents a hostile environment to transplants and invader species and a
lengthening of the time for recovery. Compared to the time required for re-
covery to climax the delay is probably negligible in the long term. Chemical
stabilizers would be the method of choice for revegetating the cleanup zone.
(2-8) Remove Shallow Root Zone, Chemically Stabilize
The effects of removing the surface soil to a depth of 40 cm increase the
problems of revegetating in the infertile soil over treatment 2-7 and eliminate
revegetation by local pioneer species. The limited potential for recovery
favors exotic invaders. Low organic matter increases runoff to a serious ero-
sion threat and heavy applications of chemical stabilizers are called for,
including those that are not acceptable after other cleanup (Appendix A,
Stabilizers). Chemical stabilizers of three to five year durability are
highly toxic and rehabilitation is required before revegetation will succeed.
This is one of the four deciduous forest cleanup treatments that require in-
tervention by reclaimers before it can start recovery towards the original
productivity. If not reclaimed the area will be lost to erosion processes.
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(3-1) Barriers to Exclude People
Natural ecosystems can be benefited by excluding humans from the area
without any impact on the plants, soils, and wildlife.
(S-2) Exclude Large Animals
Barriers which restrict large animals only will have a greater effect on
the animal populations themselves and not on ecosystem structure and function.
Large animals were once nearly exterminated from deciduous forests but several
species are now recovering. White-tailed deer (Odocoileus virginianus) feed
in old fields and have increased their numbers as agricultural land has been
2
abandoned. The fencing-off of small tracts (0.01 km ) would not represent a
2
significant proportion of available habitat, but the maximum tract (10.0 km )
could seriously limit the habitat of a local population. Even so, the effect
would be insignificant on a regional or state basis.
(3-5) Exclude Large and Small Animals
The erection of barriers to prohibit animal crossings affects only ground-
dwelling vertebrates without impacting soil and plants. Birds, insects and
squirrels are not likely to be restricted by any barrier which meets engineer-
ing and cost acceptability. Nor are small mammals and reptiles likely to be
successfully removed with the enclosure of the area. Thus, species composition
of an area would be virtually unaffected by the erection of barriers. Restrict-
ing movement of animals into or out of the area would restrict gene flow but
only the smallest area of concern would likely be impacted and then only if
the barrier remained intact for several decades. The effect on large mammals
is treated in the next paragraphs.
Black bear (Ursus americanus) are also recovering in the deciduous forest
region. Omnivorous animals which thrive on the absence of human contact are
showing the greatest recovery in back country forests of the eastern mountains.
One of the healthier populations exists in the Great Smokey Mountains National
2 2
Park, an area of 1865 km . The maximum area considered, 10.0 km , is only
0.5 percent of that area, which could not be construed to be significant.
Fringe populations might be impacted more heaivily, however.
The eastern cougar (Felis concolor cougar) is also recovering from former
population declines and is being sighted with increasing frequency. Home
3-25
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ranges are not well-known, but it appears certain that a viable population
requires areas many times larger than the largest cleanup area considered.
Thus, habitat reduction is not expected to be a factor. Potentially more im-
portant is the effect that closure might have on migratory routes. Large
predators must travel great distances hunting prey or risk depletion of their
food source. In the eastern United States, that usually means passing through
frequent narrow corridors between heavily populated areas. Closure of those
corridors could seriously restrict the home range of cougars and affect their
recovery. Impact on the species could be serious.
(4-1) Asphalt Hard-Surface Stabilisation
Paving a spill area with asphalt represents the most severe impact con-
sidered so far. Any plant invasion or animal utilization of the area would be
delayed until the asphalt begins to decompose, possibly a decade after treat-
ment. Establishment of a community would require fairly complete decomposi-
tion of the asphalt which would require further decades. The impact of an
asphalt surface over 0.01 km might be acceptable if the area originally was
of low value ecologically, but not if the area has the potential for produc-
tion of a rich community. It is not possible to consider acceptable a paving
2
cover of 0.1 km or more. Even the most disruptive of the high priority tech-
niques, soil removal or burial, would have significantly lower impact.
(4-2) Concrete Hard-Surface Stabilization
The effects of paving with concrete are qualitatively the same as with
asphalt and the primary evaluation is the same. Since concrete decomposes
more slowly than asphalt, the effects would be longer lived and thus less
acceptable than those of asphalt.
(5-0) Application of Sewage Sludge
Application of sewage sludge can replace organic matter and plant nutri-
ents lost in vegetation removal and help balance soil pH for better nutrient-
availability. ' ' The result is more rapid surface stabilization and
encouragement of plant growth. The amendment is not without problems, however.
Municipal sewage commonly contains heavy metals which can be toxic, particu-
larly to higher organisms. A potential exists for impacts on wildlife and
food-chains leading to man. Secondly, a potential exists for saturation of
3-26
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the soil cation exchange complex with excess ions leaching into streams. This
38
problem has been demonstrated for liquid effluent but could become a problem
with sludge, as well. On graded land sludge could reduce runoff and erosion
by increasing infiltration, which would speed recovery.
(6-1) High Pressure Washing (
-------
B
0-1 NATURAL RECOVERY
HERB i SHRUB I TREE STAGES
GENERALIZED TYPICAL RECLAMATION *
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processes are generalized and thus do not relate to a specific location. The
major disruptions include severe vegetation removal, surface alteration, soil
removal, plowing and soil fill. The time units are approximate with variability
resulting from local differences within treatments and between treatment differ-
ences. The ordinate (Y-axis) is without units either because it is dimension-
less (e.g., homeostasis) or site specific (e.g., primary productivity, species
diversity). See Appendix B for further use.
Species diversity increases from the bare-ground stage to some maximum
occurring during a transition from one major stage in succession to another.
In the example shown, the maximum occurs during transition from the herb stage
to the shrub stage, approximately 15 years after the sere begins. In other suc-
cessions, the maximum diversity might occur at the transition from the shrub
to tree stage (approximately 50 years) or as the climax forest replaces a sub-
climax forest (perhaps 150 years). Reclamations seed a mixture of plants,
particularly legumes such as sericea Iespede2:a and black locust. Seeding,
creates a diversity which may be greater than early serai stages but which,
through competition, do not yield to the waves of early invaders typical of
early successions. Thus, species diversity may remain low for a number of
years. The highly diverse old-field stage may be essentially bypassed with
the result that the maximum diversity obtained may be less than the maximum
attained by a natural sere. The end point is; the same, however,, and a climax.
forest resulting from a reclamation-based sere is presumed to be similar to
the climax resulting from a natural sere.
Cover increases gradually during natural successions, becoming more rapid
as trees replace the earlier stages. Mature forests with their distinct lavers
produce the greatest cover of the sere. Reclamations are similar except that
greater initial cover is possible by seeding, but cover may not increase until
trees are able to overcome the early cover species.
Primary productivity generally increases with community age, reaching its
maximum in the mature forest. The rate of change may not be constant, however,
but depend upon the rate of species replacement. Thus, if a persistent serai
stage is established, the primary production rate may be essentially constant
for several years. .
3-29
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In general, homeostasis increases with community development with the
climax forest representing the most stable state (generalized typical reclama-
tion curve). In some instances, shrub stages attain a high state of homeostasis
(natural recovery curve) and persist for several decades.
Erodability increases sharply with a perturbation but declines as vegeta-
tive cover protects the soil. During natural successions, erodability remains
higher in early stages than the later stages, although the most rapid decline
occurs during the first few years. The main point of reclamation is to quickly
reduce erosion. By seeding directly to a grass-shrub stage, the first several
years of succession are compressed into 2 or 3. Consequently, erodability
drops sharply as cover is established and declines in accordance with increased
cover thereafter.
3.5.3 Succession Stages Following Cleanup
3.5.3.1 First Year
During the first year following treatment, the clearcut forests would begin
to produce sprouts from the remaining stumps (Figure 3-2A). The spring flowering
herbs of the former forest should reappear as usual. The opening of the forest
would also permit the invasion of pioneer plant species from outside with rag-
weeds (Ambrosia spp.) and other annuals being among the first invaders. Peren-
nial grasses, such as broomsedge (Andropogon virginicus). and even woody plants
may also invade but typically do not become conspicuous. With the exception of
the sprouts, areas which have been stumped and grubbed (Figure 3-2B), scraped,
graded, plowed, or had soil added or removed should experience a similar first
year. Cover would remain low on all treatments but especially on those leaving
the poorest seedbed, such as removal of the shallow root zone or burial with
up to 100 cm soil. No plant invasion could be expected on soils with hard sur-
face stabilization.
Animal use of first year successions would be limited. Insect herbivores
could be expected and, consequently, avian insectivores. The low productivity
could not support a large consumer biomass, however. Cover on first year fields
is too low to support resident bird populations and the small mammals found
there are transients, as well. Large mammals would not find the area attrac-
tive.
3-30
-------
Areas around which barriers were erected should not be visibly different
after one year. Soils and plant cover have no visible impact following erec-
tion of barriers (Figure 3-3), or after flooding with a few cm of water.
On denuded areas receiving sewage sludge, first year germination success
and growth would be expected to exceed that of bare ground. The greater cover
would support a larger consumer biomass but no vertebrates would be expected
to become residents during the first year.
3.5.3.2 Fifth Year--
Five years following cleanup, most procedures should be represented by a
stable herbaceous community. In central Tennessee, similar aged fields were
dominated by broomsedge (Ahdropogon virginicus) and aster (Aster pilosus). In
southern Illinois, broomsedge was also dominant. Woody vegetation invades by
the fifth year and includes persimmon (Diospyros virginiana), sassafras (Sassa-
fras albidum), elm (Ulmus alata), eastern red cedar (Juniperus virginiana), and
sumac (Rhus spp.). Ground cover is high, about 119 percent in the Illinois
example, but the woody vegetation contributes only a small fraction of the cover.
Where disturbance was less than that represented by post-agricultural
successions, such as clear cutting, recovery would be more advanced. Root and
stump sprouting could produce a dense copse woodland in five years which might
prove to be attractive to deer and other forest-edge wildlife. Herbaceous
groundcover should remain dense because canopy closure would not be expected
to occur within five years. If the treatment had been to simply erect barriers,
no visible differences would be expected between treated and untreated areas.
Soil stabilization by compaction, binding agents, or flocculating agents
would probably no longer be distinguishable from non-stabilized cleanups which
left bare ground. Hard surface stabilizations would not be expected to have
broken down or decomposed in five years and, consequently, there would be no
recovery (Figure 3-3).
3.5.3.3 Tenth Year--
For the cleanups which left bare ground, the tenth year would be quite
similar to the fifth year, differing primarily in the growth of the woody
vegetation. More individuals of the same shrub species might also be expected.
The characteristic old-field/shrub stage is quite attractive to wildlife, how-
ever. The clear-cut forest might achieve canopy closure by the tenth year,
3-31
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1-2 CLEAR CUTTING
1-3 STUMPING AND GRUBBING
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Recovery of deciduous forest following
hard surface stabilization.
3-33
-------
if sprouting had been vigorous., and, if so, the herb stratum would be declining.
Hard surface stabilizations, particularly asphalt, could be starting to break
up with pioneer species starting to invade cracks. Reclaimed land should have
a mixture of trees, shrubs, and herbaceous vegetation which is attractive to
wildlife.
3.5.3.4 Fiftieth Year
In southern Illinois, the local sere lacks a pine-forest stage. Conse-
quently, 50 years of recovery would not likely produce a closed canopy. After
30 years, 22 species of trees were present but so was a perennial grass (Andro-
pogon virginicus) layer, which indicates a high light level at the herb stratum.
Seedlings of the climax oaks (Quercus imbricaria and Q. velutina) had begun to
appear, indicating that a mature forest was less than 100 years away.
In the southeastern states, a subclimax pine forest typically replaces
the shrub stage and can produce canopy closure within 30 years from the begin-
33
ning of succession. When canopy closure by conifers occurs, light to the
forest floor is greatly diminished and the herb layer is largely eliminated.
Consumers do not utilize pine forests to any great extent and, consequently,
species diversity tends to be low.
Stumping and grubbing, surface alterations, soil removals, plowing, stabi-
lizations, and soil fills should all be as described above. Clear-cut forests
would likely have produced a closed-canopy, deciduous forest and be more ad-
vanced than the bare-ground treatments. Hard surface stabilizations would not
be sufficiently decomposed to permit normal community development to progress
although individual plants might be doing well. Reclaimed land could be ex-
1 40
pected to be in closed-canopy forest but not in climax.
3.5.3.5 100 Years After Cleanup--
Extrapolating from conditions at 50 years, forests lacking a piae stage
should be approaching climax, although full growth and development would not
be expected. In forests with a pine stage, 100 years marks the transition
from pine to deciduous forest. In many seres, this is the point of maximum
diversity and productivity, both declining into the climax. This point may
contain the greatest density of breeding birds, if not the greatest diversity.
This peak in diversity, density, and biomass extends even to the populations
28
of decomposers in the forest floor.
3-34
-------
One-hundred-year-old reclamations are not known but it seems reasonable
to assume that the accelerated development during the first decade would no
longer be evident and reclamations would be similar to natural revegetations.
Neither are 100-year-old, abandoned pavements known. It is assumed that decay
of either asphalt or concrete would be fairly complete after a century and re-
vegetation would be proceeding. Vegetational composition and developmental
stage is not predictable, however, because of the spatial and temporal heter-
ogeneity which would result from the breakup pattern of the pavements. Where
diverse microsites occur on mine spoils, the revegetational patterns do not
9
conform to theoretical seres.
3.5.3.6 Climax--
In deciduous forest, climax is more often a theoretical concept than an
observable fact. Using the term loosely to mean forest dominated by a species
complex similar to the climatic potential, whether or not mature, climax forest
might be expected to occur 150 to 200 years following the disturbance. Assuming
that the forest disturbed was climax, the new climax may or may not be the same.
47
Woodwell has suggested that man-made (anthropogenic) influences are changing
the basic physical and chemical properties of the earth and may interfere with
ecosystem development as we have understood it. If so, it is understood that
these influences, such as acid precipitation, will retard rather than accelerate
ecosystem recovery.
Deciduous forest is an extremely diverse biome with numerous local seres
leading to a few climax types. In generality, natural successions from bare
ground go through a series of defined stages: annual weed, perennial herbs,
shrubs, trees. Often, one or more subclimax forest stages precede climax
forest. Occasionally, metastable subclimax communities apparently resist
invasion by trees, possibly through allelopathy. In other cases, periodic
perturbations, such as fire, lead to subclimax stages. All of these extend
the full recovery time of ecosystems.
3.6 QUANTITATIVE ASSESSMENT OF CLEANUP IMPACTS
Of the cleanup procedures specified, stumping and grubbing (1-3), scraping
and grading (1-4), soil removal (2-1 to 2-8), plowing (1-5, 1-6), and cover
with uncontaminated soil (1-7, 1-8) are similar in that the rate and pattern
of recovery will be similar. Differences which may be apparent during the
3-35
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first few years should no longer be apparent after a decade or so. Less
severe disturbances lead to more rapid recovei^y, more severe ones recover
more slowly.
Because of favorable moisture and temperature conditions, deciduous
forests are reclaimed relatively easily. The growth form of mature communities,
and their horaeostatic mechanisms, prevent revegetation of climax species, di-
rectly. Trees of the climax forest typically do not do well on freshly re-
claimed surfaces and the forest floor, which retains nutrients and retards
erosion, requires years to develop. Consequently, reclamations can only
shorten recovery time by about a decade, which represents only about 5 percent
of the time required to replace a "climax" forest. However, reclamation can
provide early vegetative cover over the entire area immediately which amelio-
rates erosive degradation in the cleanup area and gullying outside the spill
zone.
Early stages of natural successions are low in diversity and productivity.
Wildlife is not found on them. Reclamations attempt to seed directly to the
grass-shrub stage which can establish valuable wildlife habitat within 5 years.
Consequently, the benefits gained from reclamations go beyond simply reducing
erosion or slightly shortening the sere.
3.6.1 Impact Assessment
Cleanup procedures in deciduous forest are indexed (See Appendix B) in
Table 3-2 as impacts on ecosystems, with 0 equal to no impact and NA equal to
complete loss of the ecosystem. The index estimates include consideration
of the physical, biological and sociological impacts of the treatments on the
nearby vicinity of the cleanup area. There are several caveats which must be
observed. First, the numerical rankings are highly subjective. Secondly, as
explained below, most impact rankings for a given procedure in a given eco-
system increase as the area affected increases. It is also likely that the
confidence decreases as the area increases. Given enough.time, tens of years
to centuries depending on the treatment, recovery to a condition paralleling
that of surrounding untreated areas would occur due to natural recovery.
Thus the index values in Table 3-2 will tend toward 0 with time. Since the
relative impact assessment is time dependent, the time selected for comparison
was the first growing season after cleanup treatment.
3-36
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The rationale for a particular index value is discussed in Section 3.4
and summarized here. Intermediate impact rankings are explained in Appendix
B. Impact of clear cutting (1-2) on deciduous forest is related to the time
required for succession, hence the possibility of root sprouting lowers the
impact relative to stumping and grubbing (.1-4) Impacts obviously increase
with area. Scraping, burial, plowing and soil removal were all considered to
be impacts in addition to forest removal, for trees and shrubs would generally
have to be removed before the other procedures could be applied. Scraping and
grading (1-4) are not considered to be any more disruptive than stumping and
grubbing (1-3) since both preparation and the results are similar. Shallow
plowing (1-5), over a large area, would be a slightly greater impact since
herbaceous plants and seeds would be buried. Deep plowing (1-6), if possible,
on many forest soils would bring lower quality subsoil to the surface and re-
sult in a degraded seed bed. Removal of the top 10 cm (2-4) would remove local
seeds and require plant invasion from outside of the area. Hence, resulting
in a greater impact and an increasing impact with areal increase. Thinner
topsoils would also be removed. Removal of up to 40 cm would remove virtually
all forest topsoils and leave poor seed beds. Similar arguments apply to
burials. Barriers to exclude people (3-1) would have no impact while barriers
to exclude animals (3-2, 2-3) might have slight impact over large areas. The
impacts to animal populations themselves might be greater. Hard-surface sta-
bilization (4-1, 4-2) is effectively a complete, permanent loss.
3.6.2 Recovery assessment
Deciduous trees require decades to reach canopy height. Consequently,
any area where trees are removed will not be soon restored to its former state.
Furthermore, climax species have habitat requirements which differ significantly
from conditions prevailing on bare ground. Climax species are not early in-
vaders and often cannot even be planted on barren sites. Table 3-2 is based
on estimates of recovery times following various treatments and gives Recovery
Indices. The ranges' of time for expected recovery are quite large because
the factors which affect them (e.g., soil factors, precipitation cycles, etc.)
have potentially greater impact on recovery times than do the differences
between the impacts of various cleanup treatments. Consequently, while deep
plowing (1-6) has a greater perceived impact than shallow plowing (1-5), for
3-38
-------
example, the seres are sufficiently long and local variability is sufficiently
great that climax recovery times cannot be effectively differentiated.
Minimum time to recovery of climax appears to be around a century. That
is the time required to pass through the various serai stages and create micro-
climatic conditions favorable to climax species. The exception is where the
trees were clearcut but the forest was otherwise not disturbed (1-2). Sprout-
ing may result in more rapid recovery, but even that is limited by the growth
rate of the trees and the degree of invasion by non-climax species. Treatments
1-3, 1-4, 1-5, and 1-6 all require a full sere and the local variability is
probably greater than the differences between them. Shallow soil cover (1-7)
and shallow soil removal (2-1) may result in conditions similar to the above
(optimally) or could possibly be more severe perturbations. If unassisted,
natural revegetation is possible, time to climax should be similar to the above.
If not, reclamation may be indicated.
Reclamation might be necessary where depth of soil applied is great (1-8)
or the depth of soil removed is great (2-2), even if stabilizers are used (2-5,
2-8). If not reclaimed, decades could be added to the recovery times. With
reclamation, time to climax should be within the range of natural seres on
more favorable sites (1-3, 1-4, 1-5, 1-6). In general, stabilizers (2-3, 2-4,
2-5, 2-6, 2-7, 2-8) would be expected to greatly influence early succession
but their effects would not be expected to be discernible by the time climax
is approached.
Hard-surface stabilization (4-1, 4-2) would significantly retard the onset
of succession and lengthen the potential minimum time for recovery. It is not
clear if any effect would be discernible on a sere requiring 200 or more years.
Barriers '(3-1, 3-2, 3-3) do not disturb vegetation in the system and'have
no recovery time associated with them. Wildlife is discussed in Part III.
3.7 CONCLUSIONS
The preferred treatment is the "no action" option of erecting barriers
(3-1, 3-2, 3-3). The advantage is that it allows time for careful evaluation
3-39
-------
of what further steps might really be required. Particularly where large areas
might be contaminated, the effectiveness and impact of other treatments could
be evaluated experimentally.
Hard-surface stabilization offers no apparent benefits and should not be
considered.
As a generality, there are no significant advantages or disadvantages
obviously associated with any of the other treatments. The decision to actively
reclaim or not will be "influenced by the area disturbed and location. A small
2
(0.01 km ), isolated area might not need to be reclaimed while a similar area
having significant population exposure probably would need to be. Any 10.0 km
area disturbed would probably require reclamation of some kind. Beyond these
considerations, local experience with road and other construction will influ-
ence decisions on need for stabilizers and/or reclamation.
3-40
-------
3.8 DECIDUOUS FOREST REFERENCES
10.
11,
12.
13,
Anonymous. Reclamation of Strip Mined Land. In: J. W. Lewis (ed.),
Illinois Blue Book 1971-1972, State of Illinois, Springfield 1972
pp. 2-16.
Bard, G. E. Secondary Succession on the Piedmont of New Jersey. Ecol
Monogr. 22:195-215, 1952.
Bazzaz, F. A. Succession on Abandoned Fields in the Shawnee Hills,
Southern Illinois, Ecology 49:924-9.56, 1968.
Bazzaz, F. A. Plant Species Diversity in Old-Field Successional Eco-
systems in Southern Illinois, Ecology 56:485-488, 1975.
Beckwith, S. A. Ecological Succession on Abandoned Farm Lands and its
Relationship to Wildlife Management,, Ecol. Monogr. 24:349-376, 1954.
Billings, W. D. The Structure and Development of Old-Field Shortleaf
Pine Stands and Certain Associated Physical Properties of the Soil,
Ecol. Monogr. 8:437-499, 1938.
Bornebusch, C. H. The Fauna of Forest Soil, Forst. ForsVaes, Danm.
11:1-224, 1930.
Braun, E. L. Deciduous Forests of Eastern North America, Blakiston,
Philadelphia, 1950. 596 pp.
Brewer, R. and E. D. Triner. Vegetational Features of Some Strip-Mined
Land in Perry County, Illinois, Trans. Illinois Acad. Sci. 48:73-84,
1956.
Buckman, H. 0. and N. C. Brady. The Nature and Properties of Soils,
Macmillan, New York, 1969. 653 pp.
Byrnes, W. R. and J. H. Miller. Natural Revegetation and Cast Overburden
Properties of Surface-Mined Coal Lands in Southern Indiana. In:
Ecology and Reclamation of Devastated Land, Gordon and Breach Sci.
Publ., New York, 1973. pp. 285-305.
Clark, T. D. Kentucky, Land of Contrast. Harper and Row, New York,
1968. 304 pp.
Croxton, W. C. Revegetation of Illinois Coal Stripped Lands. Ecology 9-
155-175, 1928.
3-41
-------
14. Curtis, J. T. The Vegetation of Wisconsin. Univ. Wisconsin Press,
Madison, 1959. 657 pp. ;
15. Dickerson, J. A. and W. E. Sopper. The Effect of Irrigation with Munici-
pal Sewage Effluent and Sludge on Selected Trees, Grasses and Legumes
Planted in Bituminous Strip Mine Spoil. Penn. State University
Research Briefs 7:1-4, 1973.
16. Gant, R. E. and E. E. C. Clebsch. The Allelopathic Influences of
Sassafras albidum in Old-Field Succession in Tennessee. Ecology
56:604-615, 1975.
17. Henry, J. D. and J. M. A. Swan. Reconstructing Forest History from Live
and Dead Plant Material an Approach to the Study of Forest Succes-
sion in Southwest New Hampshire. Ecology 55:772-783, 1974.
18. Holland, R. F. Wildlife Benefits from Strip-Mine Reclamation. In: Ecology
and Reclamation of Devastated Land, Gordon and Breach Sci. Publ., New
York, 1973.
19. Hosner, J. F. and D. L. Graney. The Relative Growth of Three Forest
Tree Species on Soils Associated with Different Successional Stages
in Virginia. Adm. Midi. Nat. 84:418-427, 1970.
20. Jackson, J. R. and R. W. Willemsen. Allelopathy in the First Stages
of Secondary Succession on the Piedmont of New Jersey. Am. J. Bot.
63:1015-1023, 1976.
21. Johnston, D. W. and E. P. Odum. Breading Bird Populations in Relation
to Plant Succession on the Piedmont of Georgia. Ecology 37:50-62,
1956.
22. Keever, G. Causes of Succession on Old-Fields of the Piedmont, North
Carolina. Ecol. Monogr. 20:229-250, 1950.
23. Komarek, E. V. Effects of Fire on Temperate Forests and Related Eco-
systems: Southeastern United States. In: T. T. Kozlowski, and
C. E. Ahlgren (eds.), Fire and Ecosystems, Academic Press, 1974,
542 pp.
24. Kozlowski, T. T. and C. E. Ahlgren (eds.). Fire and Ecosystems, New
York, Academic Press, 1974. 542 pp.
25. Kricher, J. C. Summer Bird Species Diversity in Relation to Secondary
Succession on the New Jersey Piedmont. Am. Midi. Nat 89:121-137,
1973.
26. Kuchler, A. W. Potential Natural Vegetation of the Conterminous United
States. Amer. Geog. Soc., New York: Special Publ. No. 36, 1964.
27. Lejcher, T. R. and S. H. Kunkle. Restoration of Acid Spoil Banks with
Treated Sewage Sludge. In: Recycling Treated Municipal Wastewater
and Sludge Through Forest and Cropland. Penn. State University Press,
University Park, 1973.
3-42
-------
28. McBrayer, J. F., J. M. Ferris, L. J. Metz, C. S. Gist, B. W. Cornaby,
Y. Kitazawa, T. Kitazawa, J. G. Wern, G. W. Krantz, and H. Jensen.
Decomposer Invertebrate Populations in U.S. Forest Biomes. Peda-
biologia 17:89-96, 1977.
29. McDougall, W. B. Forests and Soils of. Vermillion County, Illinois, with' .
Special Reference to the "Striplands," Ecology 6:372-379, 1925.
30. Morrison, R. G. and G. A. Yarranton. Diversity, Richness, and Evenness, "
During a Primary Sand Dune Succession at Grand Bend, Ontario. Can.
J.'Bot. 51:2401-2411, 1973.
31. Morrison, R. G. and G. A. Yarranton. Vegetational Heterogeneity During
a Primary Sand Dune Succession. Can. J. Bot. 52:397-410, 1974.
32. Nicholson, S. A. and C. D. Monk. Plant Species Diversity in Old-Field
Succession on the Georgia Piedmont. Ecology 55: 1075-1085, 1974.
33. Nicholson, S. A., and C. D. Monk. Changes in Several Community Charac-
teristics Associated with Forest Formation in Secondary Succession.
Am. Midi. Nat. 93: 302-310, 1975.
34. Niering, W. A. and R. H. Goodwin. Creation of Relatively Stable Shrublands
with Herbicides: Arresting "Succession" on Rights-of-Way and Pasture-
land. Ecology 55:784-795, 1974. .
35. Odum, E. P. The Strategy of Ecosystem Development. Science 164:262-270,
1969.
36. Odum, E. P. Fundamentals of Ecology. Philadelphia, Saunders, 1971. 574 pp.
37. Pearson, P. G. Small Mammals and Old-Field Succession on the Piedmont of .
Mew Jersey. Ecology 40:249-255, 1959.
38. Perkins, M. A., C. R. Goldman, and R. L. Leonard. Residual Nutrient
Discharge in Streamwaters Influenced by Sewage Effluent Spraying.
Ecology 56:453-460, 1975.
39. Quarterman, E. Early Plant Succession on Abandoned Cropland in the
Central Basin of Tennessee. Ecology 38:300-309, 1957.
40. Riley, C. V. Ecosystem Development on Coal Surfaced-Mined Lands, 1918-75.
In: J. Cairns and E. E. Herricks (eds.) Recovery and Restoration of
Damaged Ecosystems. Univ. Press of Va., Charlottesville, 1977.
pp. 303-346.
41. Scanlon, D. H., C. Duggan, and S. D. Bean. Evaluation of Municipal
Compost for Strip Mine Reclamation. Compost. Sci. 14:4-8, 1973.
42. Sly, G. R. Small Mammal Succession on Strip-Mined Land in Vigo County,
Indiana. Am. Midi. Nat. 95:267, 1976.
43. Smith, R. M., E. H. Tyron, and E. H. Tyner. Soil Development on Mine
Spoil. Bull. 604, W. Va. Univ. Agr,. Expr. Stn., Mortantown, 1971.
3-43
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44. Viro, P. J. Effects of Forest Fire on Soil. In: T. T. Koslowski and
C. E. Ahlgren (eds.), Fire and Ecosystems, Academic Press, New York,
1974. pp. 7-45.
45. Vitousek, P. M. and W. A. Reiners. Ecosystem Succession and Nutrient
Retention: A Hypothesis. BioScience 25:376-381, 1975.
46. Whittaker, R. H. Communities and Ecosystems. New York, Macmillan,
1975. 385 pp.
47. Woodwell, G. M. Success, Succession, and Adam Smith. BioScience 24:
81-87, .1974.
3-44
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CHAPTER 4
CONIFEROUS FORESTS
4.1 OVERVIEW '
The coniferous forests of the United States occur in all sections of the
Nation except for the Great Plains. In the eastern portion of the country, the
distribution of conifers is considerably more continuous and less complex than
in the mountain and far western states. In the East, zonation tends to be pri-
marily a function of latitude, while in the West, altitude and slope aspect
become major factors. In the East, it is likely that cleanup procedures would
be limited to a single forest type, but in the West, one or more zones may be
involved if a spill occurs in a mountainous area. It is not possible to con-
sider the coniferous forests apart from mountainous regions, so both will be
discussed here, as will the interface between the coniferous and tundra zones.
The primary purpose of the first section of this Chapter is to provide a rela-
tively detailed overview of the major types of coniferous forest in the United
States with respect to their distribution and major species associations.
Costing has reviewed the climax vegetation types of North America and
notes that there is considerable variation among vegetation maps with regard
to detail due to disagreement on the interpretations of climax relationships.
Examples of such vegetation maps may be found ' 3>29. More recent maps have
been published by Little and Kuchler . Costing51 believes that studies of
local investigations of vegetation are necessary for a comprehensive understand-
ing of the bases for the differing interpretations found on vegetation maps.
This statement is no doubt also applicable to most descriptions of the distri-
bution of coniferous forest types, particularly those found in the more diverse
mountainous areas of the country. It is also important to note that forest
types change in many areas due to shifts in land use and in natural succession
processes, dating older maps. For example, the harvesting of Douglas fir has
resulted in the replacement of large stands of that tree by western hemlock and
various hardwoods with a resultant net increase of western hardwood forest types
4-1
-------
of nearly two million acres in the period of 1962-1970 . The concept of
vegetational climax formations and their associations permits classification
on a regional basis; it assumes an acceptance of monoclimax theory which im-
plies the existence of pre and postclimax communities. While this system is
dated, it has been widely used in various forms in the literature on North
American vegetation and it will provide a basis for the following description
of the coniferous forests of the United States.
The coniferous forest has been divided into four climax formations in
North America: Boreal, Subalpine, Montane, and Pacific Coastal. There are
also large areas of coniferous forest that are considered to be sub or post-
climax by this system. Costing51 has characterized the nature and distribu-
tion of these formations in some detail and the following descriptions are
largely adapted from his work. Another system of nomenclature refers by the
major species associations and/or their geographical location: northern conif-
erous forest (spruce fir); northwestern coniferous forest (cedar hemlock,
western larch western white pine, Pacific Douglas fir redwood); western pine
forest (ponderosa pine sugar pine, ponderosa Douglas fir, lodgepole pine);
northeastern pine forest (Jack, red and white pines); and southeastern pine
forest (longleaf, loblolly, and slash pines). (See Figure 4-1.)
The Boreal is the most continuous of the major forest formations with
respect to distribution. In the western United States, the various coniferous
formations appear in vegetation zones which occur as a function of altitude
and size of a mountain mass, the latter affecting the quantity of precipitation
which will occur on a given mountain range. At a given latitude, an isolated
mountain peak may not support stands of species having high moisture require-
ments that may be satisfied on a nearby mountain range of lower elevation but
greater mass. Due to the prevailing winds from the west, significant vegeta-
tion differences occur between the western and eastern slopes of the mountain
ranges. The character of the communities within a given zone also differs among
mountain ranges. The Rocky Mountain and Sierra Nevada forest complexes differ
significantly and are discussed separately here. The zonal climaxes occurring
within these complexes include: Tundra, Subalpine, Montane, and Foothill (not
discussed).
4-2
-------
LO
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c
o
a>
CD
4-3
-------
4.1.1 Boreal Formation
The Boreal formation, sometimes referred to as "taiga" in its northern
areas, forms a broad band across the North American continent, lying to the
south of the Tundra formation; it occurs as far south as the New England
states. The climate in the Boreal forest region is almost as severe as that
of the Tundra, being characterized by a cool, short growing season and moder-
ate precipitation that is heaviest near the East Coast (approximately 40 inches)
and lightest in the western region and the Alaskan interior (10 to 12 inches).
The topography characteristic of the Boreal formation is largely the result of
glaciation and abounds with lakes, bogs, and muskegs. Thin residual soils
overlay rock masses, or deep moraine and outwash occur along the southern boun-
dary of the formation.
The Boreal formation is characterized by climax growth of white spruce
(Picea glauca) and balsam fir (Abies balsamea); this climax is best developed
along the St. Lawrence River Valley. White spruce and balsam fir are found
scattered throughout the range and they are associated with paper birch (Betula
papyrifera) which may occur following fires in pure stands as a subclimax.
Black spruce (Picea mariana) is frequently dominant north and west of Lake Su-
perior, and it is frequently found associated with tamarac (Larix laricina) as
climax species along the northern and far western transitions in high rocky
areas. Further to the south, both species become associated with bogs. To
the west, paper birch and Jack pine (Pinus banksiaiia) occur as climax species,
and are subclimax nearer the center of the Boreal formation. Jack pine and
black spruce form a subclimax in the western part of the range and Jack pine
also occurs extensively in areas of sand plains and gravel soils.
The northern transition of the Boreal formation into the Tundra is irregu-
lar with the coniferous forest extending far into the Tundra region in sheltered
valleys while the Tundra is found on high ridges extending into the forested
26
area. Indications were found by Griggs , who studied the reasons underlying
the positioning of the Arctic timberline, which suggested that the timber line
in Alaska is advancing northward while it is retreating in portions of Canada.
The southern transition grades into grassland in the west and into deciduous
forest in the east. Also, in Alaska, the Boreal coniferous forest merges with
the northwestern coastal forest. The southern Boreal transition zone is marked
by pure stands of white pine (Pinus strobus) from New England to Minnesota and
4-4
-------
and red pine (Pinus resinosa.) in the Lake States; Jack pine also occurs in
less favorable sites in the Lake States area. In the eastern transition,
spruce and fir may mix with hardwoods or grow in alternating stands. In the
Rockies, Picea glauca is associated with Abies lasiocarpa. The northern con-
iferous forest extends southward on the higher Appalachian mountains as far
as the Great Smoky Mountains of North Carolina,, There, the growth form and
species associations are similar to those found throughout the Boreal forma-
tion, but red spruce (Picea rubens) tends to replace white spruce from New
Brunswick southward into New England. Further south, balsam fir is replaced
by Fraser fir (Abies fraseri). Therefore, the dominant species in the south-
ern Appalachians are the ecological equivalent'; of those found elsewhere in
the Boreal formation, but they may be distinguished taxonomically. As the
latitude decreases, the spruce-fir forest is limited to increasingly higher
elevations; this association may be found virtually anywhere in the northern
portions of the Boreal formation, but only above approximately 5,000 feet in
the Great Smoky Mountains. Spruce tends not to occur at the highest altitudes
in the southern range and, in its absence, fir becomes dominant
4.1.2 Rocky Mountain Forest Complex
The Rocky Mountain forest complex contains several distinguishable vege-
tation zones that extend as far north as Alberta and southward into northern
Mexico, terminating at the southern end of the Sierra Madre range; this zoaa-
tion extends westward to the eastern foothills of the Sierra Nevada range and
the eastern slopes of the Cascades, it also extends eastward into the Black
Hills. In addition to the major Rocky Mountain Ranges, the complex encompasses
the basin and range physiographic province with its numerous north-south ranges
separated by desert basins. The zones that occur are a discontinuous alpine
zone on the higher peaks, subalpine, montane arid woodland forest. These zones
are discontinuous in their distribution from rasige to range and the full com-
plement of zones is not necessarily present in each of the ranges. For exam-
ple, in the northern portion of the complex, the upper zones exist at lower
altitudes and the lower zones may not be present; each zone occurs at increas-
ing elevation as the latitude decreases. As previously discussed, there are
significant differences in zonation between north and south exposures and there
are marked differences in vegetation between the eastern and western slopes of
the individual ranges within the system and for the entire system as a whole.
4-5
-------
In mountain systems, narrow valleys tend to allow the dominants of a given
zone to extend downward into a lower zone while high dry ridges permit upward
finger-like projections of the dominants into continuous higher zones. Drain-
age of cold from higher elevations can significantly disrupt zonal distribu-
tion patterns.51 Whittaker and Niering83 have detailed the effects of alti-
tude and slope aspect upon vegetation in the Santa Catalina Mountains of
southern Arizona. (See Figure 4-2.) A review and synthesis of the factors
which produce and control the zonation of the vegetation in the Rocky Mountains
by Daubenmire may be of particular interest in the determination of the prob-
ability of reestablishing forest growth after implementation of cleanup procedures.
The zonal climaxes which occur within the Rocky Mountain coniferous forest
complex have been grouped by Costing as follows:
Alpine zone
Tundra climax
Subalpine zone
Engelmann spruce Alpine fir climax
Montain zone
Douglas fir climax
Ponderosa pine climax
Foothills (Woodland zone)
Pinon Juniper climax
OakMountain Mahogany climax
The vertical range of full development of each of the zones is approxi-
mately 2,000 feet, with the foothill zone narrowing and disappearing at the
higher latitudes and each of the other zones being found at progressively
lower altitudes. In the transitions between the zones, the species character-
istic of each zone become restricted to favorable habitats. Near the upper
boundary, these species will be more common on ridges and south-facing slopes
where less moisture and higher temperatures occur; whereas in the lower tran-.
sition, the species characteristic of a given zone will tend to occur in the
relatively cool, moist sites. Under these conditions, species of one zone
may extend into another zone. Precipitation tends to increase with altitude;
a linear increase of 4.94 per 1,000 feet of elevation was found between the
45 51
sagebrush and alpine zones on the Wasatch Plateau of Utah and Costing notes
that similar observations have been made elsewhere.
4-6
-------
3000-
2500-
2000
E^DAK^FQREST
.Mexican
pinon .
>AK "WOODLAND
?;:fj?.'i^
:Monzantta!l -"
ChThubhuo pine
Wolnof~- --' ~- -'~"
,. j-:.-;'"' cypress -f ;
- CANYON -
WOODLAND
--'-Arizona
OPEN OAK WOODLAND^*-, osewood
RoseHe .shrubs
DESERT-SCRUB^
lower Slopes
Open Slopes
NE N NW
1500
1000
Vegetation chart for the Santa Catalina Mountains, southeastern Ari-
zona. (The pattern above 9000 ft is for the nearby F'inaleno Mountains.) Four hun-
dred vegetation samples were plotted on the chart by their positions' in relation
to the elevation gradient, on the left, and the topographic moisture gradient, on
the bottom. Boundary lines were drawn to connect the mean positions at which
one community-type, as these had been defined in this study, gave way to another.
Dominant species are indicated in the parts of the pattern where they are most
important. [VVhittaker and Niering, 1965.]
Figure 4-2. Vegetation chart for the Santa Catalina Mountains, southeastern
Arizona (reproduced from Whittaker82).
4-7
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.4.1.2.1 Subalpine Spruce-Fir Climax
Engelmann spruce (Picea engelmannii) and alpine fir (Abies lasiocarpa)
are dominant in the subalpine zone. The spruce tends to be larger, more
abundant, and longer-lived than the fir. Variations in the dominant species
are found in different regions. For example, in Arizona and New Mexico,
Abies lasiocarpa var. arizonica is as important as A. lasiocarpa is in other
ranges, while mountain hemlock (Tsuga mertensiana) frequently occurs in Mon-
tana and northern Idaho; still further north, Picea glauca and A. lasiocarpa
may be associated as the transition with the northern conifer forest is ap-
proached. There is more variability among the subordinate species found in
the Rockies than among the dominants. In the subalpine climax zone, lodge-
pole pine (Pinus contorta var. Murrayana), aspen (Populus tremuloides), and
Douglas fir (Pseudotsuga menziesii) occur as climax stands following burns;
restoration of the original climax stand is quite slow. The same situation
may obtain following cleanup procedures. Lodgepole pine does not occur in
the southern Rockies, and in other areas, aspen frequently predominates over
the pine. Aspen has the ability to regenerate from sprouts and this may pro-
vide a significant advantage over the pine after a burn. This factor should
also be considered with respect to forest regeneration after cleanup.
The subalpine forest grades gently into alpine tundra in the transition
zone with a gradual lessening of the density of t^ree stands. Near the timber
line, dwarfing and distortion of the trees occur, producing a tree form re-
ferred to as "Kummholz." The timber line region is characterized by certain
tree species that are not adapted to conditions in the tundra zone and which
are unsuccessful competitors in the climax forest at lower elevations. How-
ever, these species do occur on dry and windy ridges. This is the niche oc-
cupied by the bristlecone pine (Pinus aristata) in the southern Rockies, limber
pine (P. flexilis) in the central Rockies, whitebark pine (P. albicaulis), and
alpine larch (Larix lyallii) in the northern Rockies, with the exception of
the far northern areas where lodgepole pine is found at the timber line.
4.1.2.2 Douglas Fir Climax --
The Douglas fir climax zone lies at altitudes just below the subalpine
spruce-fir zone. Douglas fir characteristically occurs in such density that
few subordinate species are present. There are north-south differences in
the Douglas fir forest. In the south, white fir (Abies concolor) and blue
4-8
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spruce (Picea pungens) are present, but they are restricted to relatively
small damp sites. In the north, the subclimax species present differ with
respect to the direction of the slope face and the relationship of the site
to the continental divide. Grand fir (Abies grandis) is found west of the
divide and characteristically occurs on the western slopes. East of the
divide Picea glauca, a representative of the northern conifer forest, exhib-
its codominance with Douglas fir, and is found southward through the montane
zone into the Black Hills.
On exposed ridges, open stands of pine which include species character-
istic of timber line are found both in the montane and subalpine zones. The
species found differ with the region: P. fliexelis var. reflexa is found in
the south; P. aristata occurs in northern Arizona, southern Utah and Colo-
rado; and P. flexilis occurs northward to the point where it is replaced by
P. albicaulis.
When stands of Douglas fir climax forest are burned, lodgepole pine or
aspen replace it, exhibiting the same relationships as discussed for the sub-
alpine zone.
4.1.2.3 Ponderosa Pine Climax --
Just below the altitude of the Douglas fir belt is the Ponderosa pine
CPinus ponderosa) zone. This species and its close relatives occur in rela-
tively open forest that becomes increasingly like savannah as the altitude
decreases. Due to the open structure of the growth, grasses form a ground
cover. The Ponderosa climax is separated from the Douglas fir by a rather
broad transition where both species coexist in a shared dominance relation-
ship. The term Ponderosa climax is something of a misnomer as that species
is truly dominant only in the northern Rockies west of the continental divide.
In other regions, Ponderosa is replaced by or found in association with closely
related varieties, having similar ecological characteristics such as P. pon-
derosa var. scopulorum on eastern slopes in the north; throughout the zone
southward, P. ponderosa var. arizonica, P. leiphylla var. chichuahana, and
P. contorta var. latifolia, all occur in the southern Rockies. Along streams
and drainage lines, narrow leak cottonwood (Populus augustifolia) will form
postclimax stands with P. acuminata and P. sargentii. Aspen (P. tremuloides)
and box elder (Acernegundo) may also occur in moist areas.
4-9
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Older Ponderosa trees are somewhat resistant to fire and are killed only
by severe burns. Pondersoa seedlings are destroyed and saplings tend to oc-
cur in the understory in groupings of even age, representing growth of several
consecutive fire-free years. Severe fires may result in stands of lodgepole
pine, while lumbering and overgrazing may result in dense growth of scrub
species found in the oak-mountain mahogany zone.
4.1.2.4 Pinon-Juniper Climax
The lowest of the Rocky Mountain coniferous zones is characterized by the
pinon-juniper climax. Typically, this is a zone of open vegetation with small
trees from 10 to 30 feet in height. This vegetation zone also occurs on many
of the low ranges in the Great Basin as the only zone present. The pinon-
juniper climax is typical of the intermountain region and forms a distinct
84
zone in the southern Rockies . The appearance and characteristics of the
vegetation within the pinon-juniper zone are relatively constant, although
it includes several species with restricted ranges and marked regional dif-
ferences with respect to taxonomic and sociologic considerations occur. Among
the junipers present in the zone are Juniperus scopulorum, J. osteosperma,
J. monosperma, J. occidentalis, J. deppeana (this list is not all-inclusive);
the pinons, or nut pines, are variously referred to as species or varieties
and include Pinus cembroides (P. edulis, P. monophylla, and P. quadrifolia).
This climax zone extends from northern Mexico along the western slope
of the Rockies to the Snake River in Idaho and into southern Alberta with the
pinon while the desert species of Juniper are replaced by J. occidentalis or
J. scopulorum. On the eastern slope of the Rockies, the zone extends as far
as Fort Collins, Colorado, at which point pinon disappears and J. scopulorum
continues northward through Wyoming, frequently associated with sagebrush.
In the northern Sierras, pinon-juniper is not present with Jeffrey pine (Pinus
Jeffreyi) grading directly into Artemisia and Pushia; it does exist on the low
eastern slopes of the southern Sierras but tends to occur in mixed growth with
other species. However, pinon-juniper does occur on every westernmost range
and mountain of the Great Basin, and frequently is separated from the Sierra
Nevada range by only a single valley.
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4.1.3 Sierra Nevada Forest Complex
The following discussion of the Sierra Nevada Forest Complex will in-
clude the southern Cascade Mountains and the Sierra Nevada which extend from
Oregon southward along the California-Nevada border, including the innermost
ranges of the coastal mountain system. The western slope of the Sierras is
gradual while the eastern slope is quite abrupt, dropping from peaks of more
than 14,000 feet to the floor of the Great Basin at an elevation of approxi-
mately 4,000 feet. Due to this slope difference, the western slope encom-
passes a much greater land area than does the eastern.
4.1.3.1. Western Slope
Due to the north-south axis of the Sierras, and the prevailing westerly
winds, the eastern slopes of the range are much drier than the western. At
the base of the western slopes, 10 to 15 inches of precipitation fall annually
with a long, unbroken summer dry season. As the altitude increases, the dry
season shortens, temperatures fall, and precipitation increases with a greater
proportion falling as snow. Approximately 80 to 85 percent of the precipita-
tion occurs in the winter, with 35 to 75 feet of snow falling in the subalpine
zone. The heaviest total precipitation is reported to occur between 5,000 and
7,000 feet41 where the mixed coniferous forest of the montane zone is found.
The subalpine zone coincides with that zone having the greatest snowfall,
and possibly this is the zone or greatest precipitation since snow gauges
which are exposed to high winds tend to give low readings; spring snow sur-
veys indicate a greater water content of the accumulated snow than can be ac-
counted for by reported precipitation36. This fact may have implications for
cleanup procedures.
Subalpine ZoneThe subalpine zone is usually found in a 1,000-foot ver-
tical range between 6,500 and 9,500 feet depending upon the latitude. Typ-
ically, this zone experiences cool, short growing seasons with wet winters
and dry summers.
The major climax species found in the subalpine zone in the Sierra Nevadas
is red fir (Abies magnifica), which comprises 80 to 90 percent of the forest
tree growth, occurring in dense stands. Other species are associated, but of
minor importance in the climax growth. Western white pine (Pinus monticola)
is usually present as a minor constituent. Lodgepole pine (Pinus contorta)
4-11
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is often present, at the edges of meadows, but in a successional role. Ir-
regular growth of mountain hemlock (Tsuga mertensiana) and white fir is
found in the zone, with the former tending to occur at the higher elevations
of the zone and the latter at lower elevations. Shrubs and herbs are found
throughout the zone and lichens occur on the trees.
Timber line is often found at lower elevations in the Sierras than in
the Rockies, ranging from 7,000 to 10,000 feet depending upon the latitude;
this is due to the more severe environmental conditions occurring in the
Sierras. Pinus albicaulis, P. flexilis, and P. balfouriana are character-
istic of timber line growth in the Sierras^0. Juniperus occidentalis is also
common at timber line on exposed, rocky slopes; it is also found on the west-
ern slopes at lower altitudes. Generally, red fir growth does not extend
to timber line, but instead grades into a relatively narrow band of Pinus
contorta - Tsuga mertensiana dominance. In this zone, P. contorta assumes
a climax role, although it is successional to Abies magnifica at lower alti-
tudes; hemlock also has climax characteristics at the upper limits of the
subalpine zone.
Montane ZoneThe montane zone occurs between 2,000 and 6,000 feet in
the Cascades, between 4,000 and 7,000 feet in the central Sierras, and be-
tween 5,000 and 8,000 feet or more in the south. Five or six principal
species have climax characteristics in this zone and tend to occur in any
combination at any altitude, although the upper and lower margins of the
zone are likely to have consistent vegetational differences. In the upper
part of the zone, white fir is usually the important dominant, where it is
sometimes found in pure stands; its numbers decrease at lower elevations.
Important species at lower elevations include sugar pine (P. lambertinana),
Jeffrey pine, Ponderosa pine, Douglas fir, and incense cedar which tends to
predominate on the most favorable sites. Douglas fir is more frequent in the
north; sugar pine and Jeffrey pine are more abundant at higher elevations,
the latter being the most drought-resistant of the major species of the zone.
4.1.3.2 Eastern Slope
The eastern slope of the Sierra Nevada range has the same vegetational
zones as those found on the western slopes. However, the abruptness of the
eastern slope and its drier climate result in less favorable conditions and
4-12
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some differences in the distribution of vegetation from that found on the
western side. The red fir forest is found in restricted areas such as the
Carson Range east of Lake Tahoe and in localized areas in the northern
Sierras. The subalpine zone is generally represented by patches of lodge-
pole pine and those species of pine found at timber line on the western side.
The montane zone extends to high altitudes with poorly developed vegetation.
In this zone, Jeffrey pine is the most important species and it occurs in
open stands which differ in appearance from those on the western slope.
Pinon-juniper forest is restricted to a few eastward-extending high spurs
of the range, although it is well developed on the next range to the east
of the Sierras .
4.1.4 Pacific Conifer Forest
The coniferous forests of the Pacific coastal region parallel the coast
from the timber line in Alaska southward to central California. Mountain
ranges of various altitudes are found within the range of this forest type.
The entire region from north to south is characterized by a mild climate
which is tempered by the presence of the Pacific Ocean. Subzero temperatures
are rare on the Alaskan coastline and from Oregon southward, frosts are rare.
Precipitation ranges from 30 to 150 inches and the humidity tends to remain
high. In the south, rainless summers tend to be compensated for by fog.
Snowfall increases with latitude where 50 to 60 feet may occur in some of
the higher mountain ranges in the north.
The character of the coastal forest is primarily montane throughout its
altitude range from 0 to 5,000 feet. In the northern portion of the Cascades
in the Washington-British Columbia border region, some subalpine forest oc-
curs, but it contains dominant species derived from the Rocky Mountains
(Abies lasiocarpa), the Sierra Nevadas (Tsuga mertensiana) and the coastal
forest (Abies amabilis and A. procera). Tundra exists on some of the higher
mountain peaks.
The best development of coastal forest species occurs in the general
vicinity of Puget Sound, with the most luxuriant vegetation occurring in the
rain forest of the Olympic Peninsula where the ranges of all of the major
species overlap and most of the trees attain their maximum size. The climax
4-13
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dominants are western hemlock (Tsuga heterophylla), western arborvitae
(Thuja plicata) and grand fir (Abies grandis). Douglas fir is the most
abundant and widespread species; it tends to be found in the drier sites.
It is intolerant of shade and becomes the major dominant after fires and
is therefore subclimactic in its relation to the forest.
North of Puget Sound, sitka spruce (Picea sitchensis) becomes increas-
ingly abundant and is a climax dominant along with Tsuga heterophylla and
T. mertensiana in the northern extension of the forest. In Alaska, where
the Boreal and Coastal forests interface with the tundra, P. sitchensis and
P. glauca occur at timber line. Southward from Puget Sound, Douglas fir
becomes increasingly important and Port Orford cedar (Chamaecyparis lawsoniana)
becomes an added climax species. Along the coast, redwood (Sequoia semper-
virens) replaces Sitka spruce. The redwoods are generally limited to the
fog belt and their range extends irregularly for a number of miles south of
Monterey, California. The species of the coastal forest extend eastward
along the Washington-British Columbia border, expanding to the north and to
the south on the western slop of the Rockies. Species found in this exten-
sion include Tsuga heterophylla, Thuja plicata, and Pseudotsuga mensiesii
and occupy a zonal position between the Douglas fir and spruce fir zones of
the Rockies. Western larch, white pine, and grand fir also occur in this
extension. Daubenmire noted that this extension follows a well developed
storm track and is frequented by winds which blow eastward from the coast
4.1.5 Coniferous Forests Occurring as
Sub and Postalimaxes
Extensive coniferous forests occur in the eastern portion of the Nation
as subclimaxes which are maintained by fires or swamps; in some regions these
forests are not considered to be climaxes. The coastal plain from New Jersey
to Florida and along the Gulf States into Texas is a relatively flat area at
low altitude. The soil is generally sandy and tends to have poor drainage
with many swamps. Raised areas are usually dry for a portion of the year.
Dry seasons are accompanied by low water tables and relatively frequent fires.
In New Jersey, pitch pine forests occur and loblolly and slash pine are found
in the states further south. These pine forests are generally open with
grass floors and are referred to as savannahs. Frequent grass fires permit
survival of the relatively fire-resistant conifers at the expense of oak and
4-14
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hickory, which would replace the conifers if the area were given prolonged
811?
protection from fire ' . Some consider these areas to be a "pyric climax."
Whatever terminology is used, the presence of frequent fires in such areas
must be considered in the reestablishment of the original growth that pre-
ceded cleanup procedures.
Coniferous forest may also be encountered within those regions generally
dominated by hardwoods. Also, an association of hemlock and hardwoods occurs
in the transition between the northern coniferous forest and the deciduous
forest. Hemlock (Tsuga canadensis) frequently occurs with beech and sugar
maple and less frequently with birch, white pine, and other hardwood species
from northwestern Minnesota through the Lake States into Nova Scotia. Many
pure stands of pines (P. strobus and P. resirtosa) have been destroyed by fire
and lumbering. White pine is found within the hardwood climax forests of the
region, but Costing believes that these long-lived trees should be consid-
ered as relicts, although they do reproduce in open areas in the hardwood for-
est. As such, their replacement following cleanup procedures may prove to be
difficult and might be considered to be optional, depending upon local circum-
stances. Tamarack, black spruce, and white cedar (Thuja occidentalis) occur
in postclimax stands and occupy bogs throughout the region. Aspen and pine ,
also occur in burned or logged out areas.
Pitch pine (P. regida), Virginia pine (P. viginiana) and shortleaf pine
(P. echinata) occur from southern New England to Georgia in that region fre-
quented by an association of oak and chestnut, with the latter two species
becoming locally abundant in the southern part of the range. In the south,
the occurrence tends to be limited to higher altitudes, but in the north, it
occurs at lower elevation and occurs as far east as Long Island. Virginia
pine, shortleaf pine and loblolly pine also occur on abandoned land throughout
the region of the oak-hickory association on the Piedmont Plateau and on the
coastal plain of the Atlantic and Gulf States. Virginia pine predominates
in the northern Piedmont with shortleaf and loblolly pine preceding climax
growth in the south, usually occurring in pure stands.
4-15
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4.2 NATURAL PERTURBATIONS
4.2.1 Fire
4.2.1.1 Unassisted Recovery Sequence --
Fossil records indicate that fire has probably always been a part of the
environment of forests on the surface of the earth. Most of.the species of
conifers have a number of fire-adapted regenerative qualities which range from
a need for mineral seed beds to a requirement for high temperatures to permit
the opening of serotinous cones. Thick bark, adventitious buds, and coppice
sprouting also enhance survival of fire. Most coniferous species are also
tolerant of exposure to sunlight and open space . It seems likely that many
of these fire-adaptive qualities will serve to assist the recovery of the
coniferous forest from cleanup procedures, if those procedures are signifi-
cantly more disruptive of the forest than would be a severe fire. However,
it is important to note that these characteristics are not universal among
coniferous trees.
On a study plot in the Sierra Nevada mountains, which was established
after a severe fire in 1960, it was found that natural revegetation (un-
assisted) by Jeffrey pine seedlings greatly exceeded that by fir seedlings**.
This situation was reversed in data obtained from ten unburned control plots
where establishment and growth of fir seedlings exceeded the pine seedlings.
The pine seedlings were found to have high survival rates and demonstrated
an exponential rate of growth. Some of the trees had attained heights of
250 cm at fourteen years of age (having germinated the summer of the burn).
It was also noted that pine seedling recruitment occurred at approximately
identical rates on burned and unburned plots.
The sequence of events following a severe forest fire will differ for
each particular forest and location within that forest. It is difficult to
generalize in this regard for all of the coniferous forests of North America.
At the site of the Donner Ridge test plots, the natural postfire reforestation
pattern appears to be: pine > pine + fir > fir. However, the stage of pure
fir forest is seldom reached in the region due to interference by fire, and
D
Bock et al. note that it is difficult for this fire-regulated successional
pattern to be reconciled in terms of classical ecological climax community
O Q
classifications . Bock et al. suggest that Jeffrey pine is particularly
adapted to the fire environment, since the observed sustained exponential
4-16
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growth pattern would not be expected in the irregular climatic conditions
that have obtained in recent years in that area.
Following a forest fire, the successional pattern is reset. Fungi and
other microorganisms invade the area , and the composition of wildlife popu-
lations is altered due to the drastic alterations in habitats produced by
the fire. Lyon and Stickney have examined the vegetal succession that fol-
lows large fires in the northern Rocky Mountains. They found that succession
in the forest is not an autogenic process in which initial serai plants modify
the site to their own exclusion and then subsequently permit the establishment
of interseral and eventually climax species. Instead, they note that succes-
sion is a sequential development of vegetation in which the more rapidly ma-
turing and often shade intolerant plants assume initial dominance and then in
turn are dominated by taller, slower growing, and often more shade tolerant
species. They obtained data from three large wildfire burns that indicated
that a high percentage of plant species on a site at the time of the fire
survive and reestablish themselves on the burned area. The majority of recog-
nizable survival adaptations are on-site plant parts and seeds or fruits, and
these provide the major source of early serai vegetation. They noted an ex-
ception to this rule in a few species that have both an on-site survival mech-
anism and airborne seeds. They found that all of the dominants of early suc-
cession will be established in the initial postfire growing season, whether
46
or not they are derived from on- or off-site sources. Lyon and Stickney
believe that reliable estimates of the likely composition of the early suc-
cessional forest can be derived from the composition of the prefire or the
first postfire year communities. Further predictions may be possible based
upon the survival strategies and dominance potentials of the various plant
species in the community which will indicate the probable structural config-
urations of the early successional period. ,
46
The findings of Lyon and Stickney suggest that in many areas, the
probable course of unassisted recovery from a cleanup operation in a conif-
erous forest might be predicted on the basis of local data on fire recovery.
4.2.1.2 Assisted Recovery Sequence --
Shearer has compared the effects of unassisted fire recovery with as-
sisted recovery in coniferous forests in the Rocky Mountains. He notes that
4-17
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historically coniferous forests of the northern Rockies have been returned
to early stages of succession by fire . This is largely a consequence of
heavy accumulations of litter and other flammable debris accumulated over
many years. Pioneer species such as western larch (Larix occidentalis) and
lodgepole pine (Pinus contorta) require an early successional stage, and
they rarely become established in the absence of a major disturbance of for-
est. Frequently, land managers utilize mechanical scarification on slopes
of less than 30 percent in order to enhance the formation of a seed bed.
Shearer describes experiments designed to obtain quantitative data con-
cerning the effects of varying intensities of burning on natural regeneration
in western larch/Douglas fir forest. It was found that early establishment
of coniferous forest regeneration following prescribed broadcast burning of
clearcuts was influenced by the interaction of several factors, the most im-
portant of which were (1) seed bed condition, (2) seed supply, and (3) en-
vironmental characteristics affecting seedling survival.
Shearer noted that even under the most extreme conditions of fire, the
soil temperature remained at 66°C at a depth of 29 mm while the surface temp-
erature was 260°C; therefore, the underground systems of the plants receive
relatively little damage, and most species were able to reestablish them-
selves by vegetative reproduction.
It was observed that most of the seeds that fell on the clearcuts came
from adjacent growth, although some were from unidentified sources, perhaps
miles distant. Most of the natural seeding occurred during periods of tur-
bulence associated with frontal weather systems. The actual distribution of
the seeds on the large clearcuts decreased rapidly with increased distance
from the edge of the adjacent timber stand surrounding the burn, but there
was a low, relatively constant concentration of seeds throughout the central
section of the burned area. Possibly a higher proportion of the total seed
in the central area was derived from unidentified distant sources, rather than
from the adjacent timber stand.
Germination of seeds was adequate on treated and untreated seedbeds,
but was greater on bare mineral soil (burned or scarified) than on scorched
or unburned duff. It was found that germination began sooner on clearcut test
beds possibly due to higher soil temperatures than obtained beneath residual
timber. It was also found that the establishment of seedlings could be increased
4-18
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by burning the residual duff on clearcuts. Burned clearcuts facing from
300 degrees to 90 degrees azimuth (west-northwest to east) regenerated well.
Clearcuts with the least amount of regrowth were judged to have poor seed
sources. Regeneration was reduced on less favorable aspects where high sur-
face temperatures and low soil water limited seedling establishment. Smaller
burned areas having three or four adjacent timber edges tended to have in-
creased regeneration due to a better seed supply and possibly better shading
from the adjacent forest.
Shearer also notes that successful regeneration was so strongly asso-
ciated with the type of habitat. Growth was particularly successful under
shade cast by either living or dead trees on burned seedbed. Growth was
sparse on poorly burned seedbeds and on hot open slopes with little or no
shade. In general, moist habitats regenerated well, while drier areas were
understocked. Large clearcuts received insufficient seed fall and the upper
soil was soon depleted of available water by heavy vegetative competition.
Shearer concluded that clearcutting coupled with prescribed broadcast
burning on north- and east-facing slopes usually leaves the cutover area re-
ceptive to natural regeneration if sufficient seed is present. On hot, dry,
and steep south- and west-facing slopes, shelterwood or very small clearcuts
(group selections) offer a better chance for regeneration by leaving a greater
seed source and better protection for th? site. Clearcuts without seedbed
preparation, regardless of the aspect, restock slowly.
4.2.2 Other Natural Perturbations
Other than fire, major natural perturbations to coniferous forests in-
clude earthquakes, land and snow slides and flooding. The severity of the
damage depends upon the intensity of the initial disturbance and the location
of the affected forest; prospects for recovery from these events are subject
to the same variables. In some instances, permanent alteration of the land-
scape will result with attendant changes in the biota of the area.
4.3 MAN-MADE PERTURBATIONS
Probably the most obvious of the man-made perturbations to the conifer-
ous forest of the United States are logging and land clearing for agricul-
tural purposes, construction, and mining. Only in the cases of logging and,
4-19
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recently, strip mining is reforestation contemplated after the clearing or
clearcutting of the land. Clearcutting for the purpose of harvesting usually
does not entail the processes of stumping, grubbing, and soil importation
that would probably occur in the case of a cleanup operation. Clearing for
agriculture is generally intended to be a permanent treatment. Therefore,
neither of these examples is strictly analogous to the sequence of events
that might be involved in the cleanup process. In some respects, the restora-
tion of a forest after a strip mining operation would resemble the cleanup
operation, but there is little historic precedence of sufficient age for this
to provide prognostic information.
4.3.1 Clearcutting
In addition to the loss of vegetation and disruption of animal habitats,
clearcutting has a number of additional effects. The ecological balance of
the forest flora and fauna is affected at all biological levels. For exam-
ple, the loss of habitats from the destruction of the trees may change the
bird population in the cle'arcut area, which in turn may affect the insect
population. The slash remaining after clearcutting will offer new habitats
for new species, and there may be increased damage to young trees in the
regenerating area from diseases and pests . Water quality in a forested
area is generally decreased after clearcutting due to increased sediment in
the water . Hibbert has reviewed the historical effects of forest treat-
ment on water yield. Generally, he found that removal of forest increases
water yield, but he notes that the results of individual treatments were
highly variable and were, for the most part, unpredictable. Hibbert also
found evidence that the increase in streamflow was proportional to the amount
of reduction of the forest. Surface runoff and streamflow were also shown to
be increased in the Hubbard Brook experiment. (See discussion by Horwitz .)
Soil erosion is greatly increased in clearcut mountainous areas. Disruption
of the soil and increased insolation alter the microbiological populations
after clearcutting. Soil nutrients are leached from the soil in clearcut
areas .
4.3.2 Strip Mining
Strip raining operations in forested areas represent a widespread source
of severe perturbation. Only in recent years have there been significant
4-20
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attempts at reclamation of mined areas, and the technology for doing so is
still in a developmental stage. May and Striffler have addressed the water-
shed aspects of stabilization and restoration of strip mined lands. They
found that erosion and sedimentation from disturbed watersheds are attribu-
table to three main sources: slides from sidecast overburden, haul roads,
and the mined area itself. Proper spoil placement to ensure bank stability
by drainage control will serve to minimize disturbance. Studies of replant-
ing of strip mined areas may be found in Boyce and Neebe and Sindelar,
64
Atkinson, Majarus and Proctor . Many of the efforts at replanting of strip
mined lands have not attempted to reproduce the original forest, but rather
to stabilize the land with rapidly growing (often imported) species.
4.3.3 Controlled Burning
Fire has been used as a tool in the forest for centuries.
In is com-
monly used now in forest management as a means of decreasing fire potential,
for removal of debris after logging operations, etc. Stark has studied the
effects of controlled burning of forest understory material upon soil nutri-
/ o
ent content. Steele has examined various aspects of smoke management from
such fires in relation to atmospheric conditions. A discussion of the envi-
20
ronmental aspects of prescribed burning may be found in Fillmore et al.
In the consideration of methods for reforestation after cleanup proce-
dures, assisting recovery through the planting of seedlings seems essential.
74
Tinus has noted that in order to survive, the species and seed source used
must be adapted to the particular site, the seedlings must be in the proper
physiological state to meet the new environment, and root contact with the
soil must be quickly established. When compared with outdoor grown bare root
seedlings, containerized seedlings can be more precisely controlled and will
not lose root contact with the soil in the planting process. It may also be
of interest to consider mychorrhizal inoculation of the soil in conjunction
with replanting, if the soil is imported and alien to the forest which is
destroyed in cleanup procedures. Mychorrhizal inoculation in afforestation
has been .reviewed by Milola
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4.4 EFFECTS OF CLEANUP PROCEDURES ON CONIFEROUS FORESTS
This section will discuss the effect on coniferous forest ecosystems of
a number of possible cleanup procedures.
(0-1) Natttral Rehab-Lli,ta.ti,on
The coniferous forest is not always pure but frequently occurs in mixed
stands with varying proportions of hardwood pioneers which become established
mostly on small bare patches, brush patches, or other non-grassy patches in
the disturbed area. An example of primary succession following complete de-
struction of a conifer forest is that of the six stages of a red spruce forest
on mineral soil . The successional stages are:
1. Moss meadow
2. Aster-fireweed meadow
3. Hair grass-sedge meadow
4. Wetlow-birch thicket
5. Aspen forest
6. Spruce forest.
In the north, gray and paper birch, pin and black cherry, and big tooth
and trembling aspen are the typical hardwood pioneers. In the south, sweet
gum, red maple, and many other hardwoods become established following clear-
cutting.
Along the east slope of the Rockies, severely disturbed areas, such as
those resulting from fires, tend to be colonized first with lichens, moss,
and fireweed. Lodgepole pine reseeds concurrently, either in pure pine stands
or in association with Englemann spruce in clearings at the upper edge of the
coniferous forest. However, cleared areas may be characterized by such harsh
climatic conditions near the ground that conifers cannot reseed in the area.
Many mountain meadows of the western American ranges may have originated in
this manner.
If natural rehabilitation is to be relied upon for the clearcut areas,
the major source of seed will be the surrounding forest. Areas with dimen-
sions greater than five tree heights (of the surrounding forest) will not
receive adequate coverage. If the treatment is carried out on a fire species
such as lodgepole pine or Jack pine, cones will not open and reseeding may
not occur.
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Although the site may' be replanted with coniferous species, hardwoods
may soon invade, and subsequent possibilities for variations in the pattern
of succession of various sites then become too numerous for generalizations.
(1-1) Chemical Stabilization
Appendix A lists the characteristics of 23 "chemical" and "chemical with
mechanical characteristics" stabilizers which are preferred for coniferous
forests. These soil sealers and stabilizers mainly include cementitipus cal-
cium compounds and mixtures, organic bituminous products, waterproofing agents,
and emulsified binders.
The use of emulsifiers is a temporary treatment for stabilizing a soil
until vegetation is established. Its effective life is not much beyond 2
years. It would only be useful on sloping areas. It could, to some extent
on most treated sites, enhance succession and the development of wildlife
habitat by retarding erosion until plants became established. It would not
adversely affect any site over and above the primary treatment.
Deflocculants such as salt, sodium hydroxide, and commercial materials
such as Calgon, when present on the soil exchange complex in sufficient quan-
tity can virtually render certain soils impervious to water. The degree to
which this can be accomplished depends upon soil texture, structure, and the
type and concentrations of ions already present in the soil. However, it is
assumed the soils of the treated areas would be appreciably affected by the
chemical treatment. Accordingly, infiltration would be reduced, and surface
runoff increased. Thus, less water would be available for vegetation that
might invade or be planted on the site. Erosion on-site and sedimentation
off-site would be increased as a result of both increased runoff and the de-
flocculated soil which would go into suspension more readily.
(1-2) Cteareutting Vegetation
Clearcutting of coniferous forest has been suggested as a possible tech-
nique for cleanup of spilled hazardous materials. Precedent for this proce-
dure and many associated problems may be found in the commercial harvesting
of Douglas fir in the Pacific Northwest, western white pine in northern Idaho,
Jack pine in the Lake States, loblolly pine in the south, and lodgepole pine
in the Rocky Mountains. Revegetation in these cases may be achieved through
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growth of previously established seedlings, natural seeding prior to cutting,
artificial seeding after cutting and plant programs. However, it is assumed
that in the case of clearcutting for purposes of spill cleanup, the clearcut
areas will be replanted or reseeded.
Technically, artificial rehabilitation is applicable to any kind of for-
est. It contrasts sharply with the seemingly closely related method of clear-
cutting combined with rehabilitation by natural means which has much greater
limitations and gives satisfactory results only under favorable conditions.
19
Some of the 'general effects of clearcutting can be summarized as
follows:
1. Clearcutting eliminates the danger of wind damage or
disease infection to residual trees in the cutover area,
but increases the risk of windthrow or heat damage to
trees bordering on the cutover area.
2. Clearcutting improves forage for game animals such as
deer, elk, and provides habitats for certain animals that
were not present before logging. However, streams may be
adversely affected by clearcutting with increased temper-
atures, debris jams, and sedimentation, all of which are
detrimental to fish populations. The procedure will also
reduce habitats of some of the smaller animals such as
woodpeckers, and tree squirrels.
3. Water yields during low-flow periods will be increased
by clearcutting; snow catch may also be increased. In
swampy areas, the water table may be elevated by the
procedure.
4. Clearcutting will permit the use of genetically improved
tree planting stock, but growing conditions will be also
enhanced for many unwanted brush species, which will com-
. pete with the young conifer seedlings.
5. Good growing conditions for shade-intolerant tree species
such as Douglas fir and noble fir will be created by clear-
cutting but seedlings will be exposed to injury from cli-
matic extremes.
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Effects of Clearcutting on Climate and HydrologySmall clearings within
forest stands can create extreme effects on the microclimate, and larger
clearings significantly affect hydrological factors. As an illustration of
these effects, Table 4-1 was taken from Geiger:25
I '
Table 4-1. Measurements on forest clearings.
Measurement item
Size index D:H*
Outgoing radiation
of open land)
Diameter D (meters)
0 12 22 24 38 47 87
(percent
Rain (percent of open land)
Temperature (excess
land midday July)
over open
0 0.46 0.85
0 11 31
87
0 0.7 2.0
0.93 1.47
33 52
105
2.0 5.2
1.82 3.36
66 87
- . 102
5.4 4.1
*D = diameter of the clearing, H = height of forest trees, and tree height
averages approximately 20 meters.
(a) Temperature: Temperature excesses (temperature increases over those
found in the forest surrounding the clearcut) increase with the size of cleared
openings in the forest up to a size index of about 1.8 because of solar heat-
ing. However, beyond this size temperature again decreases because of wind
action. It has been found that size indices less than 1.25 can provide com-
plete frost protection while frost damage will be considerable at indices of
1.50 or greater. In colder regions, air temperatures decrease linearly to
about 5°C below the temperature obtained in a closed stand as the diameter
of the clearing increases from 0 to 80 meters. Extrapolation of the data in
Table 4-1 indicates that the excesses would be minimal (except for the dif-
ferences in cooling by transpiration) in clearings 180 meters in diameter.
Soil temperatures within clearings will increase by 2°C to 3°C over
those temperatures found in soil beneath a closed stand. In colder climates,
spring snow thaws in clearings may occur as much as 4 weeks earlier than in
closed stands.
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Cb) Radiation: Incidented radiation will, or course, be greater in
clearings. Albedos will be higher in the clearings and net radiation in
clearings may vary between 70 and 90 percent of that in the forest stand.
Cc) Soil Moisture: In general, the forest bordering a clearing will
deplete soil moisture in the clearing to the extent of their root systems
during the summer, while soil moisture within the clearing beyond the forest
root zone will remain high throughout the year.76 Soil moisture within the
clearings in mixed conifer forests can be expected to be 5 to 40 percent
1. 31, 34, 57
above that of the surrounding forest.
Cd) Precipitation: Although small clearings will, because of wind
eddys, tend to increase in rainfall, their greatest effect is upon snow
catch. During periods of snowfall in small clearings, incoming snow at one
time or another comes from all directions. The ultimate pattern of snow
accumulation, however, will most strongly reflect the average velocity and
direction of air flow. The zone of maximum snow accumulation will generally
be near the center of the clearing.24'29 Snow catch in small clearings
within coniferous forests can be expected to be 20 to 40 percent higher than
that found within the forest.24'54 It should also be pointed out that the
total quantity of snow in the forest area will not be increased. Clearings
will have the effect of reducing snow catch downwind in the forest.
(el Runoff: Numerous experiments have demonstrated that clearing a
coniferous forest will increase runoff30 because of reduced transpiration
and interception. The amount of additional runoff will vary with the climate
of the area, the forest type, soils, slope and aspect. The increase will be
greatest during the first year or two after cutting. As the area is invaded
by herbaceous vegetation and broad leaf species or as planted stock develops,
the effects of clearcutting will decrease (see Section 4.5).
Erosion and sedimentation will not be greatly affected if the forest
floor is not severely disturbed by the clearcutting process.
Effects of Clearcutting upon Wildlife-The impacts of clearcutting upon
the existing and potential wildlife habitats wihtin coniferous forests may
be categorized as: direct alterations to the habitat including obvious damage
4-26
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to the structural and functional aspects of the area; and indirect altera-
tions and changes within the habitat and its surrounding area through inter-
ferences with the processes normally provided within the larger natural bio-
logical system of the forest. While the true quantitative and qualitative
impacts on wildlife generated by clearcutting in terms of ecological recov-
ery and stabilization are subject to debate, some generalizations may be made.
1. The structural alterations resulting from clearcutting
obviously influence the mature trees. In the moist cool
transcontinental coniferous forest biome between the
45th and 57th latitudes (north), the coniferous forests
modify and temper the environment such that the lesser
plant species and codominant species are dependent upon
them. The removal of the dominant species is equivalent
to forcing plant succession back to a more primitive state
near the pioneer or early second stage of succession.
2. Habitats are defined by the plant community both struc-
turally and functionally; direct utilization of the three-
dimensional space formerly occupied by the clearcut forest
for reproduction, food and shelter is no longer possible.
3. The ground plane, depending upon its condition after treat-
ment will redevelop a plant cover of some type. Erosion,
drying and heating, and general physical exposure will
make this a harsh environment for rapid development.
4. Plant succession will in most cases start anew unless the
area is planted. Migration of animal and plant species
from adjacent areas will participate in setting the char-
acter of redevelopment. If the image and statistical
character of this area is to be similar to its surround-
-'" ings, it must be supported by management activities that
recognize the needs of the area in terms of specific habi-
tat requirements. *
5. Reutilization of the area by the native mammal, bird, rep-
tile, and insect populations is a function of how well
and how fast the former habitat begins to simulate the
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the functions of the surrounding area for the support
of wildlife, and of the relative adaptability of those
species that are able to find niches within the treated
area.
The reestablishraent of plant stages represents a new-found supply of
food and shelter for the wildlife. Competition and simultaneous resource
use will prevent this space from developing immediately into its former
character.
To bring treated areas back to their former wildlife habitat requires
judicious replanting and management. How well and how much these practices
are employed will greatly influence the degree and amount of recovery.
(1-3) Stumping and Grubbing
The removal of stumps and roots creates depressions and scarifies the
treatment area. The net effect of this treatment would be modification of
the effects of simple clearcutting in several ways:
1. Surface runoff would either remain unchanged or possibly
be decreased. The additional water storage in depressions
created by the treatment would tend to offset the addi-
tional runoff that would be caused by antecedent soil
moisture.
2. The surface runoff would carry greater sediment loads
because of the additional scarification caused in the
cutting process.
3. The depressions and scars produced by the treatment would
occur at a slower rate after use of clearcutting as a
treatment procedure followed by stumping and grubbing,
than in the case of simple clearcutting for harvesting
due to the absence of roots and stumps for coppice
stumping.
5. Small mammal burrows would be destroyed and/or damaged.
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(1-4) Scraping and Grading- .....
Scraping of coniferous forest areas would require prior clearcuttlng
and removal of stumps from the treatment area. The litter layer and or-
ganic soil layers would be removed in the process of scraping. Accordingly,
infiltration rates would be greatly reduced,, surface runoff would increase,
and detention and retention storage of water would be reduced, resulting in
unchecked soil erosion. Further, the residual seed pool in the soil would
be greatly diminished and nutrient levels drastically lowered. Depletion
of populations of soil-building microfauna and flora would also take place.
Grading of coniferous forest would result in an amplification of all of
the effects of scraping treatment; erosion in particular would be increased
since smooth grading would eliminate detention and retention storage. The
grading equipment, would also tend to compact the soil, thereby increasing
runoff. Runoff efficiencies, even on slopes as low as 2 percent, might be
expected to exceed 60 to 70 percent.
(1-5) Shallow Plowing
This treatment would in ,most instances require some smoothing of the
site following stumping and grubbing. Over the long term, the effects of
shallow plowing would probably not differ greatly from simple clearcutting.
Over the short term, this treatment would be superior to stumping and grub-
bing. Essentially, on areas with soils stone-free enough for plowing, and
of adequate depth, the area would be tilled as an agricultural field. Sur-
face organic matter would be incorporated into the soil, and the soil loos-
ened, thus creating a good seed bed, and favorable conditions for root
development.
The infiltration potential would be increased by the loosened soil re-
sulting from shallow plowing and be enhanced by the creation of a uniform
depression storage for water. Assuming that the area will be quickly reveg-
etated, the potential for surface runoff and erosion would be minimized.
Such areas would not be unlike abandoned fields. The overall effects upon
infiltration created by the shallow plowing would be greater than those re-
sulting from simple clearcutting but not excessively so.
On steep shallow soils which are underlain by shallow bedrock the plow-
ing treatment could create a potential hazard for land slips and slides. By
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retaining water and with no vegetation to remove the excess water, the soil
could become saturated and slip. This would probably be true of soils with
low shearing indices, such as those developed from shale materials.
(1-6) Deep Plowing
It is assumed that this treatment would be accomplished either with rip-
pers, root plows or counter-disk plows, all of which can cultivate to a depth
of 12 to 18 inches. The deepest depth would be no greater than 24 inches,
unless specialized equipment were used. Generally, plowing will have simi-
lar effects to those produced by shallow plowing. The treatment would of
necessity be restricted to the deeper soils. Infiltration would be improved
over shallow plowing, and a greater kill of herbaceous species would be
achieved. The natural succession from coppice sprouting and residual seeds
in the soil would be delayed for longer periods than in the case of simple
clearcutting. The hazard of slips and slides would be increased in moun-
tainous areas. Small animal habitat, burrows, runs, etc., would be largely
destroyed.
Plow pans are common on old oil field soils. They hinder deep infil-
tration, increase interflow and impair root development. Fragipans and
hardpans on these often previously eroded soils are also at shallow depths.
Deep plowing would break the pans if present. In addition, for those soils
where nutrients have leached to lower levels, deep plowing would implement
turnover and mixing of the soil. Growth and development of invading species
or planted species would be enhanced.
.
' (1-7) Soil Cover less tfian 25 cm
Soil fill to even these shallow depths would require large quantities
of soil material and the use of heavy equipment for hauling and spreading.
The forest floor would be buried, effectively smothering much of the life
that it fosters and the biological/physical interactions that occur in and ..
near the surface of coniferous forest soils. Small animal populations would
suffer loss of habitat and the food supply found upon the forest floor.
Surface runoff will increase and subsequent erosion of the loose dress-
ing material would be severe. On steeply sloping land, off-site sedimenta-
tion rates would be high. The effects of the treatment would be comparable
4-30
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t A '"} "Z 1C
to the construction of logging roads ' * but more severe since larger
expanses of area would be involved, and there would be no provisions for
compaction and drainage as in the case of road construction.
The low growing plants of the forest floor would be buried and killed.
The roots of the taller, herbaceous plants would also be buried and the less
hardy of these should be expected to die due to lack of soil aeration.
Since the soil-covering material must be imported, it is likely that it
will not have come from a coniferous forest, and that it will probably be a
mixture of topsoil and subsoil, or be alluvial material and, as such, it is
likely that it will contain low levels of nutrients. In any event, the ma-
terial will be inferior to the native soil underneath. It will be loose and
could provide a good physical seed bed for germination and establishment.
The residual seed pool and nutrient level will be low. There is also the
possibility of importing plant and animal species with the material that would
compete with the natural species. The quality of the imported soil material
would be the primary factor affecting early recovery by natural means. If
the area is artificially rehabilitated, there should be no appreciable delay
beyond that induced by simple clearcutting, unless the covering material is
of very poor, quality.
(1-8) Soil Cover 25 to 100 am
The use of deep soil burial would as a treatment tend to magnify the
effects mentioned under shallow soil burial. In addition, nearly all of the
lower growing herbaceous species would be killed, and the root systems of
larger broad leaf species would be effectively buried and smothered. This
soil material would contain lower proportions of seeds and organic matter.
The potentials for erosion on-site and sedimentation off-site would be in-
creased because of the greater volume of loose material.
The destructive effect on small animal habitats would be complete. De-
velopment of herbaceous and broad leaf species would be delayed, particularly
on the larger treated areas; this would affect both large and small animals
for an extended period.
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(2-1) Remove Plow Layer
Logically, removal of the "plow layer" (uppermost 10 cm of soil) would
follow stumping and grubbing. In old forest soils this would remove humus
layers and most or all of the A horizon. Many coniferous stands, particularly
in the East and Midwest, are fire or old field subclimax forests. Loblolly,
shortleaf and slash pine exist in the South as the result of fire or previous
clearing and cultivation as do Jack pine in the Midwest and lodgepole pine in
the West. The forests of white pine in the Northeast and Virginia pine in
the Southeast are classic examples of old field subclimaxes which developed
on soils with only B or C horizons remaining. Removal of an additional six
inches would, except in soils with deep C horizons such as those found in
the eastern and southern coastal plains, essentially "sterilize" the areas
for long periods. This would be particularly true of coniferous forests
located on their characteristically shallow and/or rocky soils in areas of
steep terrain. Surface runoff and consequential erosion would be accelerated.
The reestablishment of the forest, either naturally or by planting, would be
impaired and in some cases impossible.
The effects of this treatment would be less drastic on deep soils. The
deeper layers of many coniferous forest soils have a higher nutrient content
than the surface material. If the forest is artificially rehabilitated on
these treated areas, production should not be greatly impaired.
(2-2) Remove Shallow Root Zone
It is assumed that the depth of this zone is somewhat greater than that
of the plow layer. Essentially, the effects of the removal of the described
plow layer above would be applicable to removal of the Shallow Root Zone.
Both treatments would not leave suitable seed beds for natural rehabilitation
and would delay natural succession.
(2-3) Remove Scraping and Grading, Meohanioally Stabilize
The effects of scraping and grading have been described in treatment 1-4
above. Mechanical treatment in addition to the scraping and grading is as-
sumed to involve compacting of the area with mechanical equipment (e.g.,
rollers, vibrators, rams, etc.). Thus, it would first be necessary to clear-
cut the trees, remove slash, stump and grub roots, and smooth the area.
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The smoothing treatments could involve grading, scraping, soil removal
and burial with imported soil. In any case, the degree of compaction will
be affected more by the nature of the soil material, the soil moisture con-
tent, and the compaction treatment than by the particular smoothing treat-.
nsent. Therefore, it is assumed that those areas to be mechanically treated
will essentially exhibit similar enviornmental effects and recovery rates,
regardless of the smoothing treatment used.
The average depths of compaction by various types of machines are given
in Table 4-2. The actual depth for a specific site will vary with soil char-
acteristics. Generally, at optimum moisture contents, compaction potential
will increase in the order: heavy clay, silty clay, sandy clay, sand, and
gravel-sand-clay.
Table 4-2. Average possible depth of compaction to
10 percent soil voids (from Armstrong4).
Equipment
Depth Compacted (in.)
2 3/4-ton smooth-wheel roller
8-ton smooth-wheel roller
2 1/2-ton vibrating roller
2-ton vibrating plate compactor
D-8 crawler tractor
Ram (portable)
5
6
5
12
6
6
Footed rollers, either sheeps foot or taper foot, comprise a special
class of compactor for cohesive soils. At least 64 passes are required to
completely cover a given area. Depth of compaction can reach 18 inches or
more.
The effects on microclimate of mechanical treatment will not differ
from those of clearcut areas. Wildlife should find little interest in the
treated areas since it will not support appreciable amounts of vegetation
for several years.
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(2-4) Eemove Plow Layer, Mechanically Stabilize
The effects of this treatment are essentially the same as those de-
scribed in treatment 2-3 above.
(2-5) Remove Shallow Root Zone., Mechanically Stabilize
The effects of this treatment are essentially the same as those de-
scribed in treatment 2-3 above.
(2-6) Remove Scraping and Grading, Chemically Stabilize
The result of the addition of a chemical stabilizer to stumped and
grubbed land which has been smoothed would depend on the type of chemical
treatment. Chemical emulsifiers will counteract the effects of scraping
and grading by stabilizing the soil bed until vegetation is established.
They could speed succession by retarding erosion until plants became es-
tablished. Chemical deflocculants will intensify the effects of the me-
chanical disturbance. They will reduce infiltration and increase surface
runoff. Less water will be available for vegetation that might invade the
site, thus succession will be retarded.
(2-7) Remove Plow Layer, Chemioally Stabilize
The effects of this treatment are essentially the same as those de-
scribed in treatment 2-6 above.
(2-8) Remove Shallow Root Zone, Chemically Stabilize
The effects of this treatment are essentially the same as those de-
scribed in treatment 2-6 above.
(3-1) Barriers to Exclude People
The exclusion of humans would have no negative effects on the natural
processes within the exclosure, and could be beneficial, especially in areas
of high population density.
(3-2) Exlude Large Animals
Barriers that exclude large browsers, grazers, and predators will affect
the succession within the exclosure. With the exclusion of browsing and
grazing animals, a greater density and diversity of herbaceous species will
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develop whether or not the coniferous forest cover is removed. If the trees
are removed, the early stages of succession will be extended and the develop-
ment of the climax forest will be prolonged.
The presence of more herbaceous plant species results in making avail-
able more energy to the small herbivores. In addition, herbivore population
should increase due to the absence of some of their predators. Small preda-
tors not limited by the exclosure (slumber weasel, etc.) will increase due to
the additional food supply and absence of competitive predators.
The elimination of the soil compaction produced by the larger mammals
may favor the rehabilitation of the forest floor and the reestablishment of
its ecological processes.
The large biota mammal habitat would be minimally influenced by small
2
exclosures. Large exclosures (10 km ) in areas of limited forest could have
serious negative impacts upon the local area. Home ranges of the larger ani-
mals (deer, elk, bear, cougar, etc.) are invariably larger than the largest
treated areas proposed. In the densely populated forest areas of the eastern
United States, and to a lesser extent in the more sparsely populated western
states, large exclosures could interfere with animal movement.
Barriers that exclude large browsers, grazers, and large predators will
ultimately influence the dynamics of succession within the exclosure. An
immediate reduction in browsing and grazing will favor the development of
plant species subject to these processes. These plant species, which usually
include the grasses, forbes, shrubs and palatable tree seedlings, will exper-
ience a measurable increase in growth, an increased density and therefore
higher measurable productivity (accumulated biomass). These (r-strategy)*
plant species tend to dominate the earlier stages of plant succession when
moisture, available nutrients and light quality are favorable.. Their removal
favors those less palatable tree species (k-strategy) typical of later succes-
sional stages. Therefore browsing and grazing can foreshorten plant succession
and create conditions which favor faster rates of development toward climax.
''Using the terminology of growth equations where r is the intrinsic rate of
increase, and k is the upper asymptote or equilibrium population size, r
selection predominates in early colonization with k-selection prevailing
as more and more species and individuals attempt to colonize.50
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If trees are removed, the early stages of succession will be extended, ulti-
mately prolonging the development of a climax forest.
(3-2) Exclude Large and Small Animals
This treatment would benefit birds and tree-dwelling animals because of
the resultant additional availability of protection and food. The effects on
the density and diversity of herbaceous vegetation within the enclosure and
the subsequent effects on microclimate, soil compaction and succession would
be amplified over those resulting from the exclusion of large animals.
It is also expected that any small animals trapped within the exclosure
would benefit, particularly if a source of water were available. Gene flow
would be restricted, but this effect would not be significant unless the ex-
closure remained effective for many reproductive cycles.
(4-1) Asphalt Hard Surface Stabilization
Paving a contaminated area represents a severe impact. Asphalt may be
laid either between the trees or after trees have been removed and the site
smoothed. Asphalt laid between the trees will result in the gradual (1 to 3
years) death of the trees in the treated area. Coniferous trees have rela-
tively shallow roots and depend on the infiltration of surface water for
moisture and nutrients. Paving the surface will block infiltration, and
runoff efficiency will be 90 to 98 percent of the rainfall. Plant or animal
invasion of the area would be delayed until the asphalt begins to decompose.
The existence of decaying trees on the site would speed the process of as-
phalt breakup by mechanically disturbing the surface as the trees fell.
(4-2) Conerete Hard Surfaee Stabilization
The effects of this treatment are very severe and are essentially the
same as described in treatment 4-1 above. Infiltration of surface water
would be stopped. Runoff would be virtually 100 percent of rainfall leading
to extensive off-site erosion. Establishment of a community would require
complete breakup of the concrete, a process that would required decades to
centuries.
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1,
2,
3.
(5-0) Application of Sewage Sludge
Sewage Sludge Application Without ClearcuttingThe effects upon conif-
erous forests and their associated wildlife of applying sewage sludge to the
forest soils are dependent upon the characteristics of individual wastewaters.
Chemical contaminants in wastewater may be classified as either inorganic
(heavy metals) or organic including PCBs, pesticides and other synthetic ma-
terials. Pathogenic biological pollutants include a wide variety of bacter-
ial, protozoan, parasitic helminth and viral forms. Wastewater treatment
processes can provide significant reductions in the levels of these contami-
nants, but conventional treatment processes are not adequate to remove certain
chemical and biological pollutants.
In general, based upon studies in Douglas fir stands17'55'69 the appli-
cation of sewage sludge may be predicted to have the following effects:
An increase in the rate of forest floor decomposition
An increase in the rate of tree and ground cover growth
A possible initial decrease in surface water infiltration
in the short run due to .the presence of fine sediment in
the sludge, but a net long-term effect of increased infil-
tration due to enhanced ground cover growth
A decrease in anaerobiosis in the upper soil profile
An increase in coliform bacteria which will move through
the soil profile with the soil solution
6. An increase in the flow of nitrates through the soil sys-
tem accompanied by the stripping of cations from the soil
complex
7. An increase in carbon dioxide production resulting from
organic decomposition processes in the soil
8. An increase in cationic losses due to increased mobile
anion pools
9. An increase in heavy metals in soils and animal tissues
(see also Peterson et al. )
10. An increase in microbial aerosols, depending upon the
method of application of the sewage sludge.
4-37
4,
5,
-------
Phosphorus may also increase, particularly in those soils having high
exchange capacities; however, it is most likely that such accumulation will
27 78
occur primarily in the upper soil layers. ' Soluble salts of soil ex-
tracts, notably chlorides, sulfates and calcium, will also be increased.'
In general, animal viruses have not been detected following sewage sludge
. . . 43,69
application.
32
Accumulation of heavy metals in plants grown on sludge-amended soil has
been found to be greater than that found in plants grown on untreated soil,
although toxic levels have not been detected. Similarly, dangerous levels
of heavy metals in the tissues of birds and small herbivorous mammals sampled
3 18 21
in sludge-amended areas have not been detected. ' '
It may also be expected that populations of larger browsing mammals
would increase due to the availability of additional forage. The effects
of sewage sludge application upon invertebrates will vary from species to
species. Earthworms and other invertebrates will probably tend to increase
due to the higher nutrient levels provided by the applied effluent. If the
area is heavily irrigated, the diversity and numbers of most soil microar-
thropods will decrease. Song birds may increase because of greater food
availability.
Sewage Sludge Application Combined With ClearcuttingThe combined ef-
fects of clearcutting and sewage sludge application on soils will be similar
to those produced by sludge treatment alone. In addition, the growth of
ground cover, particularly that of broad leaf species will increase. Ac-
cordingly, the return to a coniferous forest will be delayed or possibly
prevented entirely unless the area is artificially rehabilitated. The ef-
fects on wildlife will be essentially those discussed in the clearcutting
treatment 1-2 above, but with the additional enhancement of food supply.
4.5 RECOVERY AFTER CLEANUP
4.5.1 Irreversible Changes
Over the very long run (thousands of years) the consequences of all of
the treatments discussed here are theoretically reversible, assuming that no
major climatic changes occur and that the requisite sequence of events and
conditions obtain for the successional reestablishment of the original
4-38
-------
coniferous forest. Over a period of a hundred years or less, hard surface
stabilization, particularly in the case of concrete treatment, may be con-
sidered as virtually irreversible. Other treatments such as removal of the
plow layer, if done on a shallow soil on a steep hillside, might also be ir-
reversible if no supplemental remedial treatments are applied.
4.5.2 Rates of Recovery
The perturbations discussed in this chapter on cleanup procedures do not
have a great deal of precedence. The only common analogous situations are
clearcutting, fire, surface mining, and abandoned fields. Even under these
situations natural successions will not necessarily lead to the same sub-
climax or climax coniferous forest that existed prior to the disturbance.
For example, Douglas fir in the west seldom reestablishes itself naturally
following clearcutting. Longleaf pine, an important species in the south,
does not always reseed itself on burned areas,, Loblolly pine, an old field
species, may not become reestablished on adjacent old fields that are first
invaded by hardwood species and then protected from fire.
If it is desirable to have the treated area return to its former pro-
ductivity as soon as possible, then artificial planting is the restorative
method of choice. Seedlings of nearly all of the important conifer species
are grown in State or Federal nurseries. The largest treatment area consid-
ered, 10 km , would require only about 250,000 seedlings, well within the
production capabilities of any large nursery. In northwestern Mississippi,
a planting schedule of 50,000,000 loblolly pines annually was maintained for
many years.
Table 4-3 summarizes the successional associations of some major conif-
erous forest types. Recovery sequences over future time are shown graphically
to demonstrate the duration of treatment effects, assuming no retrogression
occurs. The endpoint for the curves in Figures 4-3 through 4-5 is restoration
of productivity to the extent that a layman would view it as similar to the
productivity of undisturbed areas. Representative cleanup treatments were
illustrated in the figures and the application of that information in evalu-
ation of the impact of cleanup on coniferous forest is demonstrated in some
detail in Appendix B.
4-39
-------
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4-41
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0-1 NATURAL REHABILITATION
HERB I SHRUB I TREE STAGES
ARTIFICIAL REHABILITATION*
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Figure 4-3. Sequence of ecological recovery following cleanup.
4-42
-------
2-1 REMOVAL OF PLOW LAYER
1-8 DEEP SOIL BURIAL
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Figure 4-4. Sequence of ecological recovery following cleanup.
4-43
-------
3-2 LARGE ANIMAL BARRIERS
4-0 HARD SURFACE STABILIZATION
i UJ
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Figure 4-5. Sequence of ecological recovery following cleanup.
4-44
-------
4.5.2.1 First Year
During the first year after a clearcut treatment, the remains of the
understory hardwoods would sprout, and the released herbaceous plants and
grasses would develop rapidly. Pioneer plants, primarily annuals, would
begin to invade the area, and conifer seedlings present on the area would
develop.
Natural reseeding from the trees bordering the clearcutting could pos-
sibly occur if the treatment was performed during a seed year. Otherwise
the area would have to wait, and during this time the competitive understory
will have had an opportunity for greater development. If the particular
conifer species does not reestablish well (e.g., Douglas fir) or is unable
to compete with understory hardwoods (e.g., Virginia pine) it is possible
that the stand will retrogress to brush or hardwoods.
If the area were replanted, the original stand density could, for most
conifers, be reestablished in the first year, and complete crown cover could
be obtained in 5 to 20 years depending upon the species.
The use of the area by animals, mainly transient herbivores, during
the first year would tend to increase because of the development of additional
ground cover. This would continue to a peak use at the beginning of crown
closure of the conifers.
Areas which have been stumped and grubbed and subsequently graded,
scraped, plowed, or had topsoil removed, or areas which have been dressed
with imported soil material will show less development than the clearcut
treatment. Grading, scraping, and topsoil removal will produce the poorest
conditions for rehabilitation and the areas will be vegetated primarily with
pioneer species during the first year. Stumping and grubbing and plowing
treatments will produce good seed bed and moisture conditions and will not
be greatly inferior to the clearcut treatment.
Runoff will be increased the first year on the clearcut areas (Figure
4-6). Runoff rates will be highest for topsoil removal, scraping. and grad-
ing treatments and will carry higher sediment loads from erosion. Runoff
may also be higher from areas stumped and grubbed, plowed or covered with
4-45
-------
20
15
c
a»
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CC
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o
cc
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u.
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3
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111
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cc
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2 4 6
YEARS AFTER CLEARCUT
Figure 4-6. Decrease in runoff following clearcutting coniferous forests
(after Swane and Mines72).
imported soil material, depending upon depression storage and infiltration
characteristics, but it will carry heavier sediment loads than expected from
the simple clearcut treatment.
The effects of chemical and mechanical stabilizers combined with other
treatments would be greatest for the soil removal, soil burial and scraped
treatments, and least for the stumping and grubbing and simple clearcut treat-
ment. Recovery of the area would be delayed until leaching occurred and soil
structure could re-form. Treatments which left the most organic matter would
recover more rapidly, but succession on the site should be expected to be
delayed at least 5 years by the treatment.
With the exception of the chemical emulsions, the application of stabi-
lizers will require: (1) breaking up and tilth forming; (2) application and
mixing in of the stabilizer; (3) application of water to, or its part removed
from, the soil to achieve moisture control; and (4) compaction. Thus, the
treated area must first be clearcut, stumped and grubbed, slash removed,
4-46
-------
smoothed and plowed. The stabilizing treatment would show effects far in
excess of those between the additional treatments of topsoil removal and
burial with imported soil. It is therefore assumed that all treatments (e.g.,
stumping and grubbing, grading, smoothing, burial, soil removal and plowing)
will have very similar effects and responses after stabilization.
Generally, the effects on wildlife succession and hydrology will be
greater than those of simple mechanical stabilization. Succession and wild-
life habitat will be retarded for at least an additional 5 to 10 years, and
runoff efficiency will increase to above 70 percent. However, erosion and
sedimentation will be considerably less than for the mechanical treatments,
but structures to handle the excess runoff will have to be installed to mini-
mize offsite damage from runoff.
Complete recovery of a site subjected to a combined treatment, in some
cases, may take centuries. Soil with high proportions of montmorillonite clay
and soil in areas subject to heavy frosts will loosen within a few years. Soils
in the sub-humid areas where rainfall is high and plant invasion occurs at
higher rates may require up to 5 years for the establishment of a complete
ground cover of pioneer species. It is assumed that the area would not be
suitable for planting. Thus, depending upon location, soil characteristics
and degree of compaction, succession will be delayed over that which might
occur on the simple clearcut area by 25 to 100 years. Of course, heavily
compacted areas would be very prone to retrogression.
This tendency would be amplified by the increased surface runoff and
erosion that would result from treatment. A compacted area, even if compacted
by a sheeps foot roller, and devoid of vegetation and depression storage, will
present little friction to flowing water. Infiltration, particularly in soils
with clay and silt components, will be reduced at least to 1 inch per hour or
less. It is expected that runoff efficiency will be on the order of 70 per-
cent or more.
The damage from offsite runoff, even from areas of 1 hectare, could be
considerable and would require the construction of diversions, lined channels,
or dams for water storage and desilting.
4-47
-------
4.5.2.2 Fifth Year
Three years after treatment, assuming successful rehabilitation of the
conifer, if erosion has not been severe and if the site is of good to medium
quality, the forest growing conifer species (e.g., loblolly, short leaf,
slash, etc.) will have attained heights of 20 to 60 inches. The slower
growing species, such as Douglas fir, will have reached 15 to 20 inches.
At ten years, heights of the faster growing species will be on the order of
20 to 30 feet, and those of the slower species will have attained heights of
28 71
4 to 5 feet. ' In the moist temperate zones, crowns will have started to
close and stratification will have begun. In colder regions, there will still
be heavy competition between hardwood brush and coniferous species.
If natural rehabilitation (0-1) were relied upon and had been success-
ful the density of the new reproduction might appear as shown in Figure 4-7,
to dense near the seed source and sparse or absent at greater distances.
The plowed areas will probably exhibit the best reproduction followed
in order by stumping and grubbing (1-3), simple clearcut (1-2), soil burial
(1-7), scraping and grading (1-4), and soil removal (2-1 through 2-8). In
stands with associated hardwoods, the effects of sludge treatment may be
evident in a greater development of hardwood competition.
YOUNG TIMBER
YOUNG TIMBER
CLEARCUT AREA . .
TIMBER OF
SEED-BEARING AGE
Figure 4-7.
TIMBER OF SEED-BEARING AGE
\
WIND AT TIME
OF SEED FALL
Clearcutting the whole stand, with reproduction
secured by seed disseminated from seed trees lo-
cated outside the cut stand. The density of the
reproduction 5 years after the cutting is indi-
cated by the dots (from
4-48
-------
The effects of forest removal on surface runoff will have diminished
as indicated in Figure 4-4. Runoff from the concrete and asphalt areas will
noi. be appreciably diminished since these materials will not have deteriorated
greatly.
In those forests with associated hardwoods, the crown cover of hardwoods
within clearcut areas will have developed in some stands to the point of clo-
sure and will provide cover and food for wildlife. Use of the area will be
enhanced by the border created by the clearing.
Within the exclosure, competition of hardwood and herbaceous species may
have delayed conifer growth.
4.5.2.3 Fiftieth Year --
On clearcut areas (1-2) with or without supplemental treatment (e.g.,
stumping and grubbing, plowing, etc.) which were successfully restocked,
either naturally or artificially, complete crown cover will have been ob-
tained and the herbaceous and hardwood understory will have been suppressed.
Stratification of the forest into dominants, codominants, intermediates, and
suppressed trees will have developed. The number of trees per unit area,
except in the boreal forests, where such processes occur at slower rates,
will have decreased due to suppression by larger trees as indicated for rep-
resentative tree age in conifer forests in Table 4-4.
Table 4-4. Approximate age of representative coniferous
forests where number of trees per acre is re-
duced by suppression.
Eastern Forests
White - red Jack pine
Lobloily-short!eaf pine
Spruce-fir
Western Forests
Douglas fir
Ponderosa pine
Hemlock-sitka spruce
Approximate age (years)
20 to 30
20 to 25
30 to 40
30 to 40
20 to 30
110 to 120
4-49
-------
The effects of the clearing treatments on wildlife, runoff and erosion
will not be evident. The wildlife habitat will have been essentially stabi-
lized to that of the surrounding forest. It is possible, but not likely, that
the exclosures could remain 100 percent effective, even if maintained, over
this long a period.
Asphalt treated surfaces C4-1), if not maintained, will appear as do
abandoned World War II air strips today, heavily cracked and buckled and
invaded by grasses and pioneer species. The concrete treated areas (4-2)
will, of course, be weathered but still intact except for plant invasions in
cracks or expansion joints. Offsite scouring and gullying by concentrated
runoff from the areas will still be active, assuming that any structures in-
stalled to prevent this have not been maintained. The areas treated by
sludge C5-0) will show no significant effects of treatment by this point
in time.
It is not possible to make general predictions for those sites that may
have retrogressed as a result of the treatment applied. The effects could
range from exposure of bedrock to the development of a permanent meadow, de-
pending upon the particular site and treatment.
4.5.2.4 100 Years After Treatment --
In all cases except the boreal forest, assuming that artificial rehabi-
litation or successful natural rehabilitation of clearcut areas has occurred,
the new coniferous forest will be approaching maturity. The forests .of the
southeast will have passed the point of commercial maturity. The dominant
trees will have attained heights equivalent to the representative data in
Table 4-5. Basal area development will be on the order of data presented
in Table 4-6.
On areas treated by scraping, grading, topsoil removal and burial, a
maximum depth of litter will have accumulated on the forest floor. An F
horizon will have begun to develop, but otherwise the rest of the soil pro-
file will show no appreciable development. The soils of the other treatments
will show no significant change.
Wildlife habitat 100 years after treatment will not be discernible from
the surrounding habitat, assuming that no additional perturbations have occurred
4-50
-------
Table 4-5. Height of dominants in a fully stocked stand at
100 years - good to medium site fully stocked.
Height (feet)
Eastern Forests
White - red Jack pine
Loblolly-shortleaf pine
Spruce-fir
Western Forest
Douglas fir
Ponderosa pine
Hemlock-sitka spruce
80 to 100
80 to 90
50 to 60
120 to 140
90 to 100
40 to 120
Table 4-6. Approximate basal area (m2/ha) of representative conifer species -
good to medium site, fully stocked (after Forbes22).
Eastern Forests
Age
(yrs)
20
30
40
50
60
70
80
90
100
110
120
130
140
150
Eastern
Loblolly Slash white
pine pine pine
29 32
35 36 41
37 37 48
38.5 37.5 53
39.5 38 55.5
57.5
59
60.5
61
61.5
62
Red
spruce
29.5
44
38.5
49
53.5
57
58.5
59.5
Jack
pine
29
32
33
33
32.5
31.7
29
Western Forests
Ponderosa
pine
19
35
45
48.5
49
49
49
49
49
Douglas
fir
21
32
40.5
47
52
56
59.5
62.5
65
67
69
71
73
74.5
Sitka spruce
and
western
hemlock
25.5
43
50.5
56.5
62
66
69
72
74
76
77.5
78.5
80
81
4-51
-------
to either the naturally rehabilitated or treated forest areas. However, it
is unlikely that the exclosures will have been maintained for this long a
period. Thus, evidence of the exclosures and their effects would not be
apparent.
There is no precedent for predicting the effects on succession of the
concrete and asphalt treatments. It is reasonable that natural succession
will have been delayed for at least 50 years by the asphalt treatment and
more than 100 years for the concrete treatment. Even after such a long
period, the spatial: patterns of the process would be controlled by the
breakup pattern of the covering.
The succession processes on the clearcut treatments will be approach-
ing maturity. In areas where hardwoods are the climax species, broad leaves
will begin to dominate. For other climaxes (Ponderosa pine in Arizona, for
example) the area will support a pure (unmixed) mature stand. However, the
surrounding stand will have become over-mature and have begun to retrogress.
4.6 QUANTITATIVE ASSESSMENT OF CLEANUP IMPACTS
The relative severity of the different cleanup treatments on various
environmental parameters 'is shown in Figures 4-3 and 4-5 and Appendix B,
Table B-3. It is apparent that the most severe cleanup techniques are hard
surface stabilization (4-0) and soil removal (2-1 through 2-8), while the
least severe treatments are exclusion by barrier (3-1 and 3-2) and applica-
tion of sludge (5-0). This reflects the unfortunate fact that there is an
inverse relationship between a treatment's effectiveness in contaminant de-
mobilization and its destructive environmental impact.
Lawrence has described the hypothetical development of a spruce-
hemlock forest following glacial retreat. He estimated that climax could
be reached within 130 to 200 years, at a median of 170 years. Other authors
agree that the duration of sere from bare mineral soil to climax coniferous
forest is about 200 years. Using this generalization, and noting the dura-
tion of successional periods in the development of mature forest given by
Lawrence, a series of index numbers from zero to nine (not measurable to
irreversible) can be imposed on the set of successional periods. These index
numbers can then be applied to the cleanup treatments performed over different
4-52
-------
areas, the index numbers representing the approximate point in the sere to
which the cleanup treatment retrogresses the climax forest. The result serves
as an indication of the relative severity of the treatments. Table 4-7
presents this analysis for different sizes of disturbed areas and the details
are given in Appendix B.
As expected from consideration of Table 4-7, the most severe treatments
over all areas are mechanical soil stabilization after soil removal (2-3 to
2-5) and hard surface stabilization (4-0). In consideration of treatments
2-3 through 2-5, it must be realized that erosion of the land after scraping
and compaction is a very important factor in the indicated severity of these
treatments. With treatment 2-3, the removal of only the upper five centi-
meters of soil will assure that some roots remain, from which vegetation
will emerge to check erosion during the first season after treatment. How-
ever, as deeper soil layers are removed through treatments 2-4 and 2-5, lit-
tle or no rhizomal material will remain to sprout erosion-inhibiting vegeta-
tion. Because of the compaction of the soil, seeds blown in from surrounding
areas will not find germination sites until rills and gullies have started
to form, particularly on sites with greater slope. In almost all conceivable
situations, human intervention, in the form of gully control and artificial
seeding and planting, will be required to ensure recovery of the coniferous
association within half a millenium.
Hard surface stabilization, treatment 4-0, also represents serious de-
structive impact to the coniferous forest. Asphalt will decompose at rates
determined by climate, slope aspect, asphalt composition, and vigor of me-
chanical pavement destruction by vegetation and frost. However, concrete,
due to its inorganic nature and resultant resistance to decomposition, will
have consistently higher durability than asphalt in various biomes. If the
earth is compacted or any exotic subgrade is used below the concrete, vege-
tative recovery will be further inhibited to the point where human interven-
tion will be required to ensure recovery of the coniferous association. Small
areas of high-level contamination may be served best through this treatment,
since it is the most effective and provides the greatest public safety.
However, for areas larger than Q.I km2, this treatment can be considered
unacceptable.
4-53
-------
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4-54
-------
Other treatments have serious impacts when applied over large areas.
Removal of the plow layer (treatment 2-1) or shallow root zone (treatment
2-2) has serious effects over the larger areas. First, because the best
s.oil is removed by the treatment, new topsoil must be formed before most
species can return. Second, the effects of erosion will be much more severe
over the large areas than over the small areas. That is, over areas of from
10 to 100 km2 erosion will proceed almost as rapidly as soil formation and
2
vegetation recovery, while over areas of 0.01 to 1 km vegetative recovery
will occur much faster than erosion. This Is because the turbulent currents
which produce accelerated water erosion and the high surface wind velocities
which produce accelerated wind erosion rarely occur over small areas, while
they are common over large, barren tracts. An exception would be the case
of a small area of high slope, where water erosion would be quite severe.
Finally, chemical soil stabilization (treatment 1-1) and soil cover
(treatments 1-7 and 1-8) would have serious impacts at the scale of 100 km2.
In the case of chemical stabilization this is because, over such a large
area, erosion would probably overwhelm the stabilization effect of the com-
pound, thus pushing vegetative recovery to or beyond the maximum natural
recovery span. The importance of erosion over larger areas is also the
reason why soil cover is considered a drastic treatment at the scale of
100 km2. Natural reseedir.g and sprouting from stumps and rhizomes simply
will not occur fast enough at this areal scaile to counter the destructive
impacts of erosion and mass wasting. The vulnerability to erosion from these
treatments also makes them undesirable for contaminant demobilization; it
makes little sense to use a treatment which is ineffective and causes great
environmental damage.
Three treatments are benign, or perhaps beneficial, to coniferous for-
est: barriers (treatments 3-1 and 3-2) and application of sewage sludge
(treatment 5-0). Sludge application may be effective in demobilizing a con-
taminant, and therefore is a preferred treatment, especially in sensitive
areas where low-level contamination has occurred; however, the possibility
of contaminant entry into the food chain must be evaluated prior to its use.
The next group of relatively benign treatments includes clearcutting
(treatment 1-2), stumping and grubbing (treatment 1-3), and shallow and deep
4-55
-------
plowing (treatments 1-5 and 1-6). Deep plowing and stumping and grubbing have
greater impact at the scale of 100 km2 for the same reason as chemical stabil-
ization, namely that colonizing vegetation is usually overwhelmed by erosion
in the first few seasons after treatment. Surface scraping and grading (treat-
ment 1-4) has greater impact at the 10- and 100-km2 scales than over smaller
areas because the treatment accelerates erosion while, through topsoil removal,
intrinsically decreasing the rate of revegetation.
Finally, the group of treatments which involve chemical stabilization and
soil removal, treatments 2-6 and 2-8, have serious, though not drastic, impacts
on coniferous forest associations. Quantitatively and qualitatively, their
short-terra effects and effectiveness are identical to their counterparts
(treatments 2-3 through 2-5) which involve mechanical, rather than chemical,
stabilization. The difference is that most chemical stabilizers do not com-
pact the soil to produce an environment hostile to seedling growth, but they
do effectively retard erosion while vegetation establishes itself. By the
time the stabilizer breaks down, in one to five growing seasons, vegetation
will be firmly established and will continue to retard erosion as the chemical
stabilizers decompose. This is true, in most cases, even over large areas,
although more durable stabilizers should be chosen to give plants more than
one season to become established over large areas.
4.7 CONCLUSIONS
The treatments which will have the least, and approximately equal, effect
will be exclusion by barrier (treatment 3-1 and 3-2) and sewage sludge appli-
cation (treatment 5-0). These treatments may have a beneficial effect on the
development and perpetuation of the climax association. Among the treatments
which require the removal of the forest, recovery would be most rapid with
clearcutting (treatment 1-2) and shallow plowing (treatment 1-5), with stump-
ing and grubbing (treatment 1-3) and deep plowing (treatment 1-6) having
slightly longer recovery periods only at the 100-km2 scale.
All of these treatments would be acceptable. In cases other than low-
level contamination, restriction by barriers should be used only in remote
areas, because barriers provide no significant, immediate demobilization to
a contaminant.
4-56
-------
Treatments involving mechanical compaction (treatments 2-3 through 2-5)
and paving (treatment 4-0) would have severe impacts over all areas. These
treatments should be prohibited at all scales greater than 1 km2, and should
be used over smaller areas only in the case of contamination severe enough
to prohibit the use of less damaging., thoxigh highly effective, techniques
such as those involving chemical stabilization (treatments 1-1, 2-6, 2-7, and
2-8). Soil cover (treatments 1-7 and 1-8) should be used only for contami-
nants which would naturally degrade before natural erosion removes the soil
cover. The exact determination of the proper treatment must be made consid-
ering the quantity and quality of released contamination, as well as the
proximity of the site to human populations and activities.
4-57
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4.8 CONIFEROUS FOREST REFERENCES
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8. Bock, J. H., C. E. Bock, and V. E. Hawthorne. Further Studies of
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9. Bormann, Frank, Likens, Fisher, and Pierce. Nutrient Loss Accelerated
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10. Boyce, S. J., and D. J. Neebe. Trees for Planting on Strip Mined Land
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33 pp.
11. Campbell, T. E., and W. F. Mann, Jr. Regenerating Loblolly Pine by
Direct Seeding, Natural Seeding, and Planting. U. S. Department
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12. Chapman, H. H. Is the Longleaf Type a Climax? Ecology 13:328-34, 1932.
13. Cluff, B. Engineering Aspects of Water Harvesting Research. Univ. of
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14. Copeland, 0. L. Forest Service Research in Erosion Control. Vol. 12(1)
75-79 (reprint"), 1969.
4-58
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15. Daubenmire, R. F. Vegetational Zonation in the Rocky Mountains.
Botanical Review 9:325-93, 1943,,
16. Dindal, D. L. Effects of Municipal Wastewater Irrigation on Community
Ecology of Soil Invertebrates. Symposium on Municipal Wastewater
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State University, School of Forest Resources, Philadelphia, Penn.,
.1977.
17. Edmonds, R. L. Microbiological Characteristics of Dewatered Sludge
Following Application to Forest Soils and Clearcut Areas. Symposium
on Municipal Wastewater and Sludge Recycling on Forest Land and Dis-
turbed land. Penn. State University, School of Forest Resources,
Philadelphia, Penn., 1977.
18. Ellertson, R., and G. R. Geoffrey. On Uplake of Redwinged Blackbirds
Nesting on Sludge-Treated Soils. Symposium on Municipal Waste-
water and Sludge Recycling on Forest Land and Disturbed Land, Penn.
State University, School of Forest Resources, Philadelphia, Penn.,
1977.
19. EPA. Processes, Procedures and Methods to Control Pollution Resulting
from Silvicultural Activities. EPA 430/9.73-010 Office of Air and
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20. Fillmore, W. J., D. I. Aldrich, J. S. Barrows, R. B. Perry, and B. F.
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In: Proc. Tall Timbers Fire Ecology Conference 14:627-44, 1974.
21. Fitzgerald, R. Recovery and Utilization of Strip-Mined Land by Appli-
cation of Anaerobically Digested Sludge and Livestock Grazing.
Symposium on Municipal Wastewater and Sludge Recycling on Forest
Land and Disturbed Land, Penn. State University, School of Forest
Resources, Philadelphia, Penn., 1977.
22. Forbes, R. D. (editor). Forestry Handbook. Ronald Press Co., New York,
1961.
23. Fredrickson, R. L. Sedimentation After Logging Road Construction in a
Small Western Oregon Watershed. USDA Misc. Publ. 970, No. 8, 1965.
24. Gary, H. L. Snow Accumulation and Snowmelt as Influenced by a Small
Clearing in a Lodgepole Pine Forest. Water Resources Research 10(2):
348-353, 1974.
25. Geiger, R. The Climate Near the Ground. Oxford University Press,
1961. pp. 611. .
26. Griggs, R. F. The Edge of the Forest in Alaska and the Reasons for its
Position. Ecology, 15:80-96, 1934.
4-59
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26, Harris, A. R. Physical and Chemical Changes in Forested Michigan Sand
Soils with Effluent and Sludge Fertilization. Symposium on Munici-
pal Wastewater and Sludge Recycling on Forest Land and Disturbed
Land. Penn. State University, School of Forest Resources, Phila-
delphia, Penn., 1977.
28. Harris, A. S. Clearcutting Reforestation and Stand Development. Journal
of Forestry 6(330), 1974.
29, Haupt, H. J. Relation of Wind Exposure and Forest Cutting to Changes
in Snow Accumulation. In: International Symposia on the Role of
Snow and Ice in Hydrology, Banff, Alberta, 1972.
30. Hibbert, R. Forest Treatment Effects on Water Yield. In: International
Symposium on Forest Hydrology. (Sopper and Lull, ed.) Pergamon
Piess, New York, 1967. pp. 813.
31. Hoover, M. D. Effect of Removal of Forest Vegetation Upon Water Yields.
American Geophysical Union, Transactions 25 969-975, 1944.
32. Hornbeck, J. W., M. T. Katerba, and R. S. Pierce. Effects of Sludge
Application in a Northern Hardwood Forest on Soil Water Chemistry
and California Population. Symposium on Municipal Wastewater and
Sludge Recycling on Forest Land and Disturbed Land. Penn. State
University, School of Forest Resources, Philadelphia, Penn., 1977.
33. Horwitz, E. C. J. .Clearcutting: A View from the Top. Washington, D.C.:
Acropolis Books Ltd., 1974.
34. Johnston, R. S. Soil Water Depletion by Lodgepole Pine on Glacial Till,
U.S. Forest Service, Intermountain Forest and Range Experiment Sta-
tion, Ogden, Utah, Research Note INT-199, 1975. 8 pp.
35. Kidd, :*. J., Jr. Soil Erosion Control Structures on Skid Trails. USFS
Research Paper INT-1, 1963. 8 pp.
36. Kittredge, J. Forests and Water Aspects Which Have Received Little
Attention. J. For., 34:417-19, 1936.
37. Komarek, E. V., Sr. Fire Ecology Review. Proc. Annual Tall Timbers
Fire Ecology Conf. 14:201-16, 1974.
38. Kuchler, A. W. Potential Natural Vegetation of the Coterminous United
States. American Geographical Society Special Publication No. 36.
New York: American Geographical Society, 1964. 144 pp.
39. Larsen, J'. A. Fires and Forest Succession in the Bitterroot Mountains
of Northern Idaho. Ecology 10:67-76, 1929.
40. Lawrence, D. R. The Glaciers and Vegetation in Southeastern Alaska.
American Scientist, Summer, 1958. pp. 89-122.
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41. Lee, C. H. Total Evaporation for Sierra Nevada Watersheds by the
Method of Precipitation and Runoff Differences. Trans. Araer.
Geophys. Union, Pt. I. (Cited from Costing, 1956), 1941, pp.50-66.
42. Little, L., Jr. Atlas of United States Trees: Volume 1. Conifers and
Important Hardwoods. U. S. Dept. of Agriculture. Misc. Publica-
tions No. 1146 (undated).
43. Lui-Hing, C., and S. J. Sedita. Viral and Bacterial Levels Resulting
from the Land Application of Digested Sludge. Symposium on Munici-
pal Wastewater and Sludge Recycling on Forest Land and Disturbed
Land, Penn. State University, School of Forest Resources, Philadel-
phia, Penn., 1977.
44. Lull, H. W. Soil Compaction on Forest and Range Land. U.S. Forest
Service, USDA Misc. Pub. #768, 1959.
45. Lull, H. W., and L. Ellison. Precipitation in Relation to Altitude in
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.Symposium on Municipal Wastewater and Sludge Recycling on Forest
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of Woody Plant Species on Sludge-Treated Spoils in the Palzo Mine.
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4-64
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CHAPTER 5
AEOLIAN MOUNTAIN PEAKS
5.1 OVERVIEW ,'
The discussion in this chapter will largely be restricted to high mountain
regions and peaks that lie above the tundra life zone, but much of the material
may be applicable to desert mountains of much lower elevation arid the barren'
peaks and outcroppings of forested mountain ranges. Generally, the environ-
ments to be considered herein consist of steep slopes and barren rock; depend-
ing upon the altitude and latitude, ice and snow and harsh meteorological
conditions may be present, unmitigated by the protection of vegetative cover.
Depending upon geographic location, tundra, desert and various forest life
zones surround the mountain peaks at lower elevations, frequently in close
proximity. Because of the fact that the surrounding life zones are a priori
"downstream," it is likely that cleanup operations may ultimately involve more
than the primary site of a spill, if such is a mountain peak. If containment
or stabilization of a spill on a mountain top is not effected by the cleanup
procedures implemented, the discussions in the reports for other life zones
will become applicable at lower elevations. It should also be noted at the
outset of this discussion that probably few, if any, of the cleanup procedures
covered in this series of reports will be either effective or logistically
possible on many mountain peaks due to the severity of the physiographic and
meteorological components of the environment.
5.1.1 The High Mountain Peak Environment
The vegetational zonation found in mountain ranges varies largely with
the latitude, altitude, slope aspect, mass of the mountain range, prevailing
wind patterns and the location of the range with respect to land and oceanic
masses. These factors are discussed in some detail in the coniferous forest
chapter.
5-1
-------
Life zones in the uppermost mountain regions of the world have been
described by Whittaker as arctic-alpine desert and semidesert. The semi-
desert occurs in arid regions above the timberline. In temperate zones, sparse
communities of low shrubs and/or cushion plants may occur. In the arctic, the
semiarid areas are generally considered to be part of the tundra zone, but with
respect to physiognomy, plant adaptations, soil characteristics and sparseness
of animal life, they are desert-like. Arctic-alpine deserts tend to have very
low plant cover, dominated by snow, ice or rock which may support growth of
bacteria, algae and lichens. Vascular plants may occur in irregularly scattered
pockets having less extreme microclimates. These deserts occur in Greenland,
Antarctica, and above timberline on high mountains all over the world. Alpine
deserts occur in the lower alpine zone in arid mountain ranges. At lower
latitudes, permanent ice and snow are not necessarily present, and the presence
and nature of vegetation will vary with the amount of moisture present.
TO
Swan notes that the alpine regions of the world are delimited by timber-
lines extending from latitudes 72°N to 56°S with a maximum altitudinal extension
to approximately 14,000 ft. Figure 5-1 depicts the worldwide distribution of
timberlines and the arctic and aeolian zones. The upper edge of the alpine
zone is usually defined as the upper limit of the range of vascular plants.
Here too occurs an upward transition from autotrophic to heterotrophic life
forms. The characteristics of this boundary identify three basic types of alpine
regions: high-latitude, low-latitude and a depressed equatorial alpine region.
In the low latitude alpine environment, vascular plants are found above 20,000
ft. (6,100 M) and a long growing season is typical.
4
Above the alpine zone lies the aeolian zone which Swan has divided into
terrestrial, nival and aquatic phases. In the aeolian zone, autotrophic algae,
lichens, mosses and a variety of heterotrophic animals and plants occur, but
vascular plants are entirely absent except in isolated instances where micro-
habitats exist which provide more favorable circumstances. The aeolian zone
extends in altitude to include the summit area of Mount Everest where bacteria,
fungi and yeasts are found. Figure 5-2 illustrates alpine-aeolian zonation in
the eastern Himalaya.
5-2
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LIMIT OF VASCULAR PLANTS
HIQICST MAXIMUM TIMBERLINE
UWEST MAXIMUM TIMBERLINE
ISOTHERM OF 21'f. OVER OCEAN
" AMERICA, S. AMERICA, ANTARCTICA
JU«OPE. ». ASIA, AFRICA
ASIA, AUSTRALIA
N. PACIFIC, JULT MEAN
t, PACIFIC, JANUARY MEAN
(CALCULATED FROM SEA LEVEL
LAKE RATE: 1*F.-J20 n.
Figure 5-1. Alpine and aeolian regions of the world
(from Swan38).
5-3
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3PtCT«8iU5 ."r
R (IOOOSOMII M
Romuc
BtTjm UTILIS
Figure 5-2. Alpine-aeolian zonation in the eastern
Himalaya (from Swan38).
5-4
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Most of the work on high-mountain ecology has been done in Europe and in
North America; a considerable amount of work hass also been done in the Soviet
38
Union. Swan notes that unifying concepts need to be developed in order to
link the ecological characteristics of the widely spread treeless mountain zones
throughout the world that are commonly lumped under the category of "alpine."
For example, in the eastern Himalaya, the life found above the level of the
highest vascular plants forms a distinct category.
5.1.2 The Aeolian Life Zone
In the aeolian zone, nutrients are supplied by the atmosphere (carried in
by wind). Swan has distinguished between the aeolian and alpine regions by
contrasting the sources of nutrition: alpine biota are dependent upon local
autotrophic flowering plants, whereas aeolian organisms are basically supplied
by air-transported nutrients that are rarely of local origin. Hutchinson19 con-
siders the aeolian region to be roughly equivalent to the hyperallobiosphere
or that portion of the eubiosphere at high altitudes where heterotrophic
organisms are dominant.
The aeolian and alpine regions may be defined geographically as well as
nutritionally and include some portions of the high alpine zone and the nival
zone described by European researchers. 3 Swan38 believes that the aeolian
region is most easily recognized where established or semipermanent organisms
exist in the absence of flowering plants. Vascular plants may be absent at
lower altitudes in particular localities or seasons, and when the ground is
covered with snow and organisms dependent upon snow and wide-blown nutrients,
the distinction may become blurred. Swan37 suggests that the picture may be
simplified if the aeolian region is arbitrarily defined as being near or above
the upper limits of flowering plants.
Nutritional patterns in the aeolian zone are still not completely under-
stood. Animals are sometimes found at altitudes far above the highest vascular
plants; in such instances, wind-blown nutrition is ascribed. Also, insects and
crustaceans occur in temporary glacial pools, and it may be inferred that those
organic nutrients present are probably of atmospheric origin, falling on old
snow fields and eventually being released from melting ice. Arthropods and
birds that feed upon wind-blown insects are obviously aeolian, but they may be
5-5
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transient visitors to the zone. In many, perhaps most', instances the type and
quality of nutrients involved in the support of aeolian life and the degree
to which animals and plants are dependent upon atmospheric nutrition are un-
known. Gregory has reviewed various organic particles carried by the atmo-
sphere such as pollen, bacteria, fungi and insects. Luty and Hoshaw have
38
examined airborne dissemination of green algae. Swan has reviewed the ecology
of the three phases of the aeolian zone (nival, aquatic and terrestrial); a
brief adaptation thereof follows.
5.1.2.1 The Nival Phase of the Aeolian Zone--
Descending air over snow fields may have the effect of concentrating
particles suspended in the atmosphere; hence, analysis of snow fields may pro-
vide an exaggerated impression of the distribution of airborne debris. Wind-
blown particles tend to blow on and off of most surfaces, but remain upon snow.
Osburn studied the phenomenon of the accumulation of radioactive fallout
contamination of snow; he found that the particles concentrate in a snow patch
as it melts, presumably as a function of adsorption of the particles to surfaces
within the snow. Interestingly, radioactive debris was held to a large extent
within a shrinking snow patch and was released in reduced quantities in the melt
water. He also noted that radioactive particles tend to concentrate in soil
depi-essions beneath melting snow. These observations may be of potential signifi-
cance in the design of alternative cleanup procedures for implementation in the
high mountain environment.
Autotrophic green and bluegreen algae may be considered to be of an aeolian
nature in the high mountain environment in that nitrogen and other nutrients must
be derived from the atmosphere. Bettler has suggested the existence of a food
chain consisting of pollen > bacteria > algae > annelids for the green snow worm
Mesenchytraeus solieugus that occurs on a British Columbian glacier. These
aeolian annelids are found in the mountains of the northwestern United States,
Western Canada and Alaska.
There has been some work suggesting the possibility of organic precipitates
and proteinoid materials of oceanic origin being deposited upon high mountains,
? Q
but Swan believes that further study is necessary on this topic. Accumulations
of dead insects are occasionally found at high elevations, and'these are
scavenged by certain species of birds. As previously mentioned, Osburn found
5-6
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that radioactive particles concentrate.in soil depressions beneath melting
snow; it is also possible that this is true for organic materials.
5.1.2.2 The Aquatic Phase of the Aeolian Zone--
The organisms that inhabit the pools and torrents of the aquatic phase
of the aeolian zone are considered to be aeolian by virtue of the fact that
the organic materials upon which they subsist are assumed to be originally of
atmospheric derivation. Torrential fauna include turbellarians, crustaceans,
hydracarinids, and various insects that inhabit areas primarily or solely near
the sources of torrents or those whose primary nutritional source is closely
linked with organic materials released from snow or ice. Large populations of
fairy shrimp (Branchinecia sp.) are found in temporary glacial pools at altitudes
up to 19,000 ft. in the eastern Himalaya. Examination of their intestinal
contents has revealed mostly fine granular glacial dust mixed with traces of an
unidentifiable organic material; algae have not been found. That algae are found
in more permanent ponds suggests the existence of nutrients derived from auto-
trophic plants, but if, in fact, the primary algae are green algae, the presence
of nitrogenous material derived from the organic debris of snow may be inferred.
Swan believes that many lakes classified as alpine are,- in fact, aeolian.
5.1.2.3 The Terrestrial Phase of the Aeolian Zone--
The organic and other particulate matter that is deposited upon high
altitude snow and ice surfaces also deposits and collects upon snowless areas,.
the particles being trapped within cracks and crevices where air turbulence is
reduced and the particulate contents of the air can fall out. Such accumula-
tions of the terrestrial phase are frequently obvious and largely account for
collected dust under rocks on mountainsides. Rock slopes free of snow harbor
more scattered and thicker accumulations of debris than snow-covered slopes;
such concentrations serve to sustain aeolian organisms. It is likely that such
sites will also trap spilled materials that are not blown off rocky mountain
top surfaces.
Terrestrial aeolian animals are frequently found at lower altitudes on rock-
covered glaciers. Various spiders, mites, and insects have been found in this
environment in the Himalaya. Mites, collembolans and flies live in the absence
of plants on the snow free slopes on the sides of glaciers; their nutrition is
aeolian in nature. Salticid spiders (Europhrys sp.) have been found at 22,000
5-7
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ft. (6700 m) in the Himalaya and are presumed to feed upon collembola, anthomyid
flies and possibly wind-blown insects. An example of this aeolian food source
may be seen on the peak of Citlaltepetl (Pico de Orizaba) in Mexico where July
winds are from the east with a sweeping uplift of air from the tropical valleys
of Vera Cruz onto the mountain peak; many insects are transported to the peak
by these winds. The lizard Sceloporus microlepidotus Wiegmann is relatively
abundant on rocky slopes above timberline and is found at 15,800 ft. of
elevation (700 ft. above the highest flowering plants). The lizard colonies
are visited by ravens (Corvus corax sinuatus Wagler) and sparrow hawks (Falco
sparverius sparverius Linn.). Salamanders (Pseudoeurycea gadovii) were collected
at 15,000 ft. and rattlesnakes (Crotalus triseriatus) at 14,850 ft. Swan
suggests that all of these organisms exist, at least partially upon the aeolian
food chain. Lizards have also been found at extreme elevations in Peru and
10
Nepal.
The upper limit of the terrestrial phase of the aeolian region is uncertain.
Swan38 notes that sun/shade temperature differentials of 43°C (78°F) are found be-
tween shade and sun near the ground at altitudes of 15,500 ft. He suggests that
it is at least plausible for such differentials to exist at higher altitudes,
perhaps even near the summit of Mount Everest, in micro habitats sheltered from
high wind velocities. Assuming a lapse rate of approximately 3°F per thousand
foot increase in elevation, minimum shade temperatures near the summit of
Mount Everest would approximate -9°F (-23°C), and maximum shade temperatures
would approach 20°F (-7°C). Based upon data from free-air temperatures and
comparative temperatures between snowless valleys and snow-covered slopes,
Swan38 suggests that actual shade temperatures near the summit of Mount Everest
are somewhat colder, but even if shade temperatures approximate -30°F (-33°C),
it is conceivable that on calm days, surface sun temperatures may approach
50°F (10°C). The fact that icicles exist where snow overlies dark vertical
rocks at extreme altitudes indicates the occurrence of above freezing tempera-
tures. Figure 5-3 indicates the sun/shade temperature ranges occurring at
15,500 ft. of elevation for soil and air in a valley in eastern Nepal.
Swan38 lists a number of bacteria, fungi and yeasts that were collected
by the 1963 American Mount Everest expedition. He suggests that periodic equable
temperatures and water are available at high altitudes; the fact that the
organisms obtained on Mount Everest represent soil microflora rather than a
5-8
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18
miscellany of air-borne organisms supports the thesis that living organisms
do exist and grow on very high mountains..
Lichens are widespread in the alpine zone and are often found at higher
altitudes than are local vascular plants, but they are relatively scarce in
extremely arid environments or on surfaces recently uncovered by permanent
snow. In eastern Nepal, certain vascular plants that can obtain water from the
soil exist at higher elevations than do the noticeable lichens. That lichens
can grow upon glass and smooth rock surfaces without leaving any trace of etch-
ing is suggestive of their aeolian nutritional status. Lichens are known to be
31 38
sensitive to smog and to concentrate radioactive fallout. '
Although lichens are scarce -at the high elevations of the aeolian mountain
zone, they do constitute the most visible of the plant life forms in this zone;
therefore, it is of interest to consider their ecology in greater detail. Hale"1
states that lichens occur in virtually every pioneer terrestrial habitat from
antarctic and arctic to tropical areas. Their ability to adapt to xeric en-
vironments permits them to dominate in certain habitats that are devoid of
other plant life forms. Generally, lichens have a high light requirement and
they are succeeded by bryophytes and higher plants where they are shaded and other
conditions permit such successional growth. However, in habitats where condi-
tions are relatively stable as in the Arctic and Antarctic, in deserts, and rock
outcrops, lichen communities can persist for centuries. Hale notes that various
lichens tend to be specific for certain rock types. Mattick states that lichens
14
have been found as high as 6200 m (20,341 ft.). Gams has reported lichens at
7000 m (22,965 ft.) on K-2 in Karakonm. Kappen states that lichens are often
the predominant form of vegetation in mountains of northern regions such as
Scandanavia, but many species demonstrate reduced vitality above 5200 m (17,000
ft.)-
38
Swan ascribes the scarcity of lichens at high elevations to lack of surface
water from snowmelt, or possibly to snowblast. Below 5750 m (18,864 ft.), sub-
surface liquid water from snowmelt permits the development of small "oases" of
8
vascular plants in the scree. Here (in what is, strictly speaking in view of
our working definition of the aeolian zone, an upward extension of tundra),
lichens are found entangled with small herbaceous plants. The relative aridity
of the area confines the vascular plants to portions of scree slopes with under-
Q
ground meltwater sources, or to rock-base niches. Lichens, lacking a vascular
5-10
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system and roots, are unable to utilize subsurface water, and therefore are limited
20
by the degree of aridity of the particular mountain environment.
TO
Swan has noted that studies of barren areas of the world, notably those of
the antarctic, give little consideration to airborne nutrition. Llano has
discussed the contribution of wind-blown guano to populations of collembola and
mites found within a few hundred miles of the South Pole.
In order to provide a basis for estimation of time to recovery from a clean-
up operation, it is of interest to briefly consider the nature of lichen growth.
2
Armstrong has reviewed studies on the growth rates of lichens. Lichen colonies
do not have a steady growth rate; initial growth is slow, until a diameter of
approximately 1-1.5 cm is reached at which time the rate increases and becomes
nearly linear until a diameter of 12 cm is attained and then the rate slows, be-
coming non-linear. Studies under more ideal growth conditions than those obtain-
ing in the aeolian mountain peak environment indicate thallus (plant body) dia-
meter growth rates (in the rapid linear growth phase) ranging from 1.5 to 3.0 mm
per year for the lichen Parmelia gfabratula. A study of maximum thallus dia-
meter versus thallus age indicates that nearly 25 years are required for the
lichen to attain, a diameter of one centimeter, then (at an increased rate of
2
growth) a diameter of 7 cm may be reached after fifty years. Armstrong suggests
that there is considerable variation in the growth rate on an individual plant
18
and that the rate is quite sensitive to environmental factors. Hale notes
that while lichens with diameters of 30-40 cm have been reported in the Arctic
and are reputed to be several thousand years old, only direct and continuous
observation can establish the true age of a lichen thallus. Hale lists growth
rates for several species; one is reported to have an annual radial growth
rate of 25 mm and another ranges from 11 to 90 mm. Growth rates for a given
species increase with the temperature of the local climate. Hale believes that
the average life span of a given lichen thallus may range from 20 to 40 years,
depending upon species and conditions. In the foliose lichen Parmelia con-
spersa, growth slows after a thallus diameter of 9-10 cm is reached, following
which the center decays and is overgrown by crustose lichens. These crustose
lichens also overgrow freshly exposed rock surfaces where the centers of the
thalli have fallen away. Hale is of the opinion that such "recycling" of a
lichen community can continue until the micro-environment is so altered that
5-11
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other plant forms succeed the lichens. Since the last glaciation of North
America and Europe some 10,000 years ago, such recycling of lichen communities
may have occurred hundreds or thousands of times.
There are several methods of measuring and expressing lichen growth rates,
none or which are entirely satisfactory. Armstrong suggests that when the
problems of such measurements are solved, the science of lichen ecology will be
able to progress rapidly. If the diameter and radial growth rate can be accurately
determined, it "becomes possible to estimate the age of a colony, but, according
to Armstrong, there are currently several problems with such determinations.
This "state of the art" probably partially explains the absence of growth data
on lichens in the aeolian mountain zone.
Bailey states that there have been few studies in which the germination and
development of lichen propagules (bodies containing the algal and/or fungal
spores which are disseminated by wind, water, animals, etc.), on substrates
conducive to lichen growth. Lichens are structures composed of both fungi and
algae in a symbiotic relationship. They produce propagules containing either
or both symbiotics, but only the latter type can reproduce the lichen structure.
Propagules are dispersed by wind and Bailey cites studies indicating that the
propagule content of the wind is proportional to the regional abundance of lichens.
9
Bond found that glacial ice in Colorado contains arctic-alpine lichen spores
that are presumably aeolian in derivation. Once a spore has been deposited on
a suitable substrate, it must germinate and then attach itself to the substrate
by the formation of a "holdfast." Thallus fragments of preexisting plants can
also become established on a new site by the formation of a holdfast. Different
species of lichens vary in the types of spores that are formed.
Bailey notes that little is known of the nature of colonization of newly
exposed surfaces, partially due to the relative scarcity of such areas. It was
found that the island of Krakatau was colonized some 3 years after the volcanic
eruption, which removed all plant cover, by blue-green algae; lichens followed
at a later stage. Studies on Surtsey, a volcanic island which appeared off the
southwest coast of Iceland in 1963, indicated the presence of three species of
lichens by 1970 and 11 species by 1973. Four of the species were widespread
and evenly distributed over the island. Aeolian transport is ascribed to these
botanic colonists. The lichens first became established in and around holes in
the lava, suggesting that surface texture was important in providing a "foothold"
for the holdfasts of the plants.
5-12
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Based upon the foregoing discussions, it would appear that lichens are
able to colonize a new area within a 10 year period of the first exposure of
the substrate surface, but development of the plants is a slow process, requir-
ing 50 years to attain a diameter of 7 cm and perhaps 80 to 100 years to "mature"
to a diameter of 12 cm. These estimates are based upon the results of studies
in more temperate environments than that which obtains in the aeolian mountain
peak zone; here, conditions are more severe, and the time to recovery may be
markedly increased.
The time required for recolonization of a treated area will depend upon the
extent and nature of the treatment, and the abundance of lichens surrounding the
treatment area. If viable fragments of lichen thalli survive treatment which
includes the removal of the lichens, the rate of recolonization may be relatively
rapid and independent of the size of the treatment area. If no viable thalli
fragments or propagules survive a treatment, colonization will have to come from
outside, and will probably be slower for a large treatment area than for a
small area. It should be emphasized that this brief review only skimmed the
surface of lichen biology and ecology, and that many important aspects of their
developmental patterns were not discussed. Further, no data were found for-
environmental conditions comparable to the aeolian mountain zone.
Swan suggests that the reestablishment of life forms in areas uncovered
by permanent snow may require considerable time and that aeolian forms are
successional to alpine flora and fauna in environments capable of supporting
alpine life forms.
5.2 NATURAL PERTURBATIONS
Only aeolian life, as discussed earlier in this chapter, will be considered
here. There is little precedence for intentional perturbation of high mountain
peaks and relatively little literature concerning either natural or intentional
perturbations. Also, in the discussions of other life zones, steep slopes per
se were considered only incidentally.
The lack of vegetation and the steep slopes characteristic of high mountain
peaks make them particularly vulnerable to the erosive forces of earthquakes,
wind, water, ice and associated debris. Meltwa.ters and rainfall wash soil away,
leaving rills behind. The steepness and shape of a slope strongly influence
the velocity and destructive force of water runoff. High mountains tend to have
5-13
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steep slopes with an average gradient of 25° or more. The gradient is a func-
tion of various factors, including the type of rock present, the age of the
mountains, their tectonics, climate, etc. Soil destruction also is a function
of the shape of the slope, the relative positions of sections with different
gradients and the nature of the soil formation; for example, podzolic soils,
formerly under forest, are particularly vulnerable to erosion.1 Animal grazing
activities also serve to erode mountain slopes as well as enhance conditions
for water and wind erosion.
The hydrographic networks of mountainous regions are complicated systems
composed of rivers and streams of various sizes, gullies and ravine type
gorges, all of which usually terminate in larger mountain rivers. Al'benskii
and Nikitin have discussed these systems with respect to various aspects of
mountain system erosion. They note that the conditions of headwaters of rivers
serve to determine the role of rainfall in feeding the rivers. In high mountains,
the role of rainfall is negligible; snow is the major source of runoff. Ground-
water provides approximately one third to one half of the water of mountain
rivers. Rivers originating from glaciers and. snowfields have fairly regular
rates of flow, whereas those originating below the snowline frequently run dry
in the summer. Where forestation is light or absent, the rate of runoff in-
creases rapidly and the rate of decrease is only slightly less; heavily forested
areas usually do not have sharp runoff peaks. "
5.2.1 Erosion and Mudflow Phenomena
Al'benskii and Nikitin observe that the greatest force of linear erosion
in mountains is exerted by small rivers and streams, and temporary torrents,
particularly in periods subject to strong showers and/or intensive snowmelt.
Such torrents are known as mudflows (or mud-stone flows) and are loaded with
silt, sand, debris, stones and other solid material. The character of the
flow is influenced by the degree of solid material loading; if there is little
solid material present (a fluid or turbulent mudflow), the flow resembles a
freshet, but if the water is heavily loaded (a cohesive or structural mudflow)',
the movement of the flow may be greatly slowed.
Cohesive mudflows have a high specific gravity and tremendous destructive
force derived from flow pressure and shocks from stones carried by the flow.
Such flows tend to congeal, forming a wave-like elevation when their movement
stops. Fluid flows tend to be contained within the action section of the
5-14
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stream bed, depositing and, to some extent, sorting their solid contents, Mud-
flows may also be classified according to their origin, e.g., fed by slope
erosion and weathering products, fed from linear sources, etc. In arid mountains,
the drainage areas of mudflows may contain great reserves of solid material and
strong showers may produce highly destructive mudflows.
Mudflows may reach volumes exceeding those of freshets by a factor of 30
or more. Table 5-1 provides data from mudflows in the Soviet Union. Mudflows
have been known to carry rocks of 100 cubic meter volume for considerable dis-
tances. Mudflows are characterized by episodic activity, being common in some
regions and irregular in others. Mudflow velocities vary from 3-7 m per second
and tend to proceed in waves of varying height and frequency. Waves are caused
by obstructions in the path of flow. Erosion by mudflow is a widespread phe-
nomenon on mountains, but flows are rare in densely forested areas. Owens
has studied the morphology of alpine mudflows.
Should an uncontained or unstabilized spill be washed from the primary site,
the inclusion of radioactive material in a mudflow is a possibility.
5.2.2 Snow Avalanches
. 1
Al'benskii and Nikitin note that snow avalanches are most frequent in
high mountains, but they do occur occasionally on medium and low ranges. Ava-
lanches tend to form where large masses of snow accumulate on steep slopes or
along ravines. Three types of avalanches may be distinguished on the basis of
their formation: surface, bottom and jumping. Surface avalanches are actually
snowslides coming off an entire surface of a steep slope; they are common on
smooth grassy slopes and are more frequent on slopes facing the sun. Bottom or
trough avalanches form in ravines and hollows and slide in the shape of a talus
fan. Jumping avalanches differ in that they'form in ravines or other surfaces
terminating in high escarpments from which the sliding snow "jumps." Avalanches
are capable of producing severe destruction, averaging 50-60,000 tons in weight
and slides of 1.5 to 2 million cubic meters have been observed. Avalanches
tend to flow from slopes of 30° gradient or more, although some have been ob-
served on slopes of 15-18°. Generally, avalanches do not form in densely
forested stands. Schaerer discusses the effects of terrain and vegetation
upon avalanche sites. An excellent reference to the physics, ecololy and
management research of avalanches may be found in Perla and Martinelli.
5-15
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5.2.3 Landslides
29 .......
O'Loughlin has studied factors affecting the incidence of landslides.
He found that a combination of steep slopes, heavy seasonal rainfall and an
impermeable till substratum predisposes a site to catastrophic failure. The
occurrence of springs at the heads of landslide scars suggests the importance
of groundwater in the release of materials for slides.
Dingwall has found that erosive overland flow of debris and,fine sedi-
ments from bare debris surfaces is greatest during summer months. This process
is limited: to those months when the debris is snowfree and unfrozen; to those
surfaces unprotected by vegetation and coarse debris; and to finer fractions of
the debris.
5.2.4 Overgrazing
Overgrazing is a cause of soil destruction on mountain slopes; while there
is no forage in the aeolian zone, the topic is included here as a perturbation
affecting high mountain slopes. Animal grazing trails criscross in increasing
density with time, resulting in vegetation removal and soil destruction.
Continued use of the trails inhibits regrowth of vegetation. Where the trails
merge, sheet erosion can reach proportions of as much as 100 cubic meters of
soil per hectare per year.
5.2,5 Recovery
Recovery, either unassisted or assisted, from perturbations in the mountain-
top environment does not have the same meaning as in the sense of the discussions
covering other life zones. In cases where perturbations such as rock, mud,
snow, or ice slides erode barren mountain peaks or slopes, devoid of higher
forms of vegetation, the term "recovery" seems to have little meaning. In lower
life zones, recovery refers to restoration of the original life forms such as
forests or grasslands, but in the aeolian environment where the only life forms
are microorganisms, lichens, insects, and a few incidental animals, there is
little to restore. Erosion, either violent or gradual, must be considered as
a natural process of wearing down mountain ranges. At lower elevations where
life zones other than aeolian are present, the term recovery regains its signifi-
cance and the reader is referred to the appropriate chapters of this series.
5-17
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However, while recovery is not an applicable term, prevention or reduction
of the severity of certain perturbations of mountain environments may be both
possible and desirable. With respect to transuranic spills and cleanup, certain
preventative measures may aid to reduce spread of the spilled material. This
concept will be discussed at greater length in a later section. It is of in-
terest here, however, to note that some success has been encountered in the re-
duction of the incidence and/or severity of avalanches, erosion and mud flows
through afforestation. Afforestation is certainly not a short-term procedure,
but it may have some applicability with respect to treatment of transuranic
spills. Discussions of afforestation at lower elevations in the aforementioned
1 24 4
context may be found in: Al'benskii and Nikitin; Margaropoulos; Aulitzky;
Martinelli; and De Quervian and Der Gand.
Al'benskii and Nikitin discuss the topic of afforestation as a possible
4
means of reducing mudflows and avalanches. Aulitzky notes that in many cases,
timberlines lie below altitudes where tree growth is climatically possible and
he discusses the possibility of afforestation above present timberlines. Mar-
26
tinelli lists possible methods of snowpack and avalanche control: weather
modification by cloud seeding; intentional avalanching for the purpose of stor-
ing snow in shaded valleys at high elevations; reshaping of natural terrain to
improve show trapping efficiency and capacity; control of snowraelt by addition
of materials to the snow surface; and the erection of snow fences and other
12
barriers to increase snow accumulation in desired areas. Dortignac discusses
the possibility of increasing the melt rate of glaciers and packed snow by
scattering dark materials over the surface.
5.3 MAN-MADE PERTURBATIONS
No precedents were found in the literature for intentional perturbations
of mountain peaks in the aeolian life zone; however, perturbations of mountain
peaks and slopes at lower elevations are common in the form of plowing and re-
contouring for strip raining and agricultural purposes; these perturbations may
occur in desert mountains which have certain similarities to the aeolian zone
with respect to the absence of vegetation.
5.3.1 Regrading and Replanting
28
May and Striffler discuss regrading and revegetation of mountain watersheds
5-18
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sustaining severe mechanical and hydrological disturbances due to strip mining
operations. Al'benskii and Nikitin discuss increased erosion due to agricul-
tural efforts on mountain slopes, and methods of afforestation of these damaged
slopes by terracing and replanting. i
5.3.2 Alternative Techniques
The aeolian mountaintop environment presents unique logistical problems for
cleanup that are not present in other terrestrial environments. As discussed
earlier, the potential for immediate and possibly widespread dissemination of
spilled material by wind and water is great. Possibly, the first problem to be
addressed will be that of containment rather than cleanup. As noted in the fore-
going section, most of the treatments considered for other terrestrial environ-
ments will not be applicable to mountain peak spills. They might, however,
become applicable if an uncontained spill spreads; the contamination of streams,
lakes, and mudflows presents a definite hazard. The derivation of possible
substitute treatments is beyond the scope of this report, but certain observa-
tions are pertinent.
It is important to note that wind is an important component of the high
mountain macroenvironment in the aeolian zone. Life forms that are adapted to
an existence based upon the providence of the windfall most likely will be more
abundant in sheltered microhabitats where windborne debris can settle out of
suspension. This precipitation process will include atmospheric contaminants.
Osburn has noted that lichens collected in areas adjacent to the Greenland
"Broken Arrow" incident contained higher than background contamination.
Various aspects of the physics and management of snow and ice are discussed
in Martinelli, Dyunin,13, Gary,15 Shiotani and Arai,35 Tabler,39'40 Tabler and
41 33
Schmidt, and Perla and Martinelli. An important factor in the treatment of
a spill in the aeolian zone will be whether the spill occurs on a snow-covered
surface, soil surface, or rock surface. The observation of Osburn that snow
adsorbs and concentrates particulate matter can be of extreme importance for the
design of effective containment and cleanup procedures. The combined actions of
water and gravity, which present the immediate danger of spread of the spill to
lower levels on the mountain, might also make possible the utilization of the
properties of an affected watershed to concentrate and contain a spill.
5-19
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Similarly, the effects of wind barriers, serving to concentrate organic
and particulate matter in the aeolian environment, might also provide additional
possibilities for treatment. Devised techniques embodying these and similar
factors might also be environmentally compatible and offer comparatively short
recovery times.
The possibility of controlling snow surface temperatures by dusting with
various materials has been studied by Arnold, Grove et al., and Williams and
Gold.44
It is likely that there will be a degree of similarity between the responses
of the aeolian and alpine environments to cleanup procedures. Swan primarily
distinguishes between the biological components of the two zones on the basis
of nutrition; with respect to the physical phase of the environment, there probably
will be a number of similarities in the response of terrain in the two zones to
cleanup operations. It should be realized that mountains, particularly the
peaks, present a dynamically unstable condition rather than the dynamic equilibria
presented by biological systems. Geologically speaking, all mountains are doomed
to destruction by erosion; therefore, "recovery" of the physical component of the
mountain ecosystem does not have the same meaning that it does in more horizontal
situations. At best, "recovery" will imply a return to the pre-treatment dynamic
state, or rate of erosion.-
5.4 EFFECTS OF CLEANUP PROCEDURES ON AEOLIAN MOUNTAIN PEAKS
5.4.1 Proposed Treatment Techniques
As discussed previously in the section on recovery from natural perturba-
tions, the high mountain peak environment presents a totally different situation
from those discussed in reports on other life zones. First, the very nature of
what is meant by the term "recovery" is open to question. There are few life
froms present to be significantly affected by possible cleanup procedures..
There are no flowering plants in the aeolian life zone; life forms present on
the high peaks are limited to bacteria, fungi, algae, lichens, insects, nema-
todes, and a few species of birds and reptiles. Second, the nature of the moun-
tain peak terrain, combined with the lack of flowering plants will make questions
concerning recovery from most of the treatments considered in other reports
moot: there is virtually no plant life to "recover" and such treatments as
5-20
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vegetation removal, surface alteration, soil removal, plowing, soil fill,
sludge application and flooding are either not applicable or, if logistically
possible, impractical. It appears likely that alternative and innovative
treatment procedures will be necessary to treat primary spill sites, while
conventional treatments may be necessary at points below the spill if it is not
contained.
While it is true that there is little variety or abundance of life in the
aeolian environment, the ecosystem that exists may be considered quite fragile.
As previously discussed, it has been observed that lichens are slow to become
established on high mountain surfaces that have been uncovered from permanent
snow. Those life forms that have become established in the aeolian system are
dependent upon accumulations of nutrients that: are ultimately derived from the
winds; it is likely that the time required for such accumulations to form is
rather long. There are very little data on this subject.
An important consideration in the design of cleanup techniques for the
mountain peak environment is the accessibility of this zone to men and equip-
ment. The operation of helicopters may not be feasible at higher elevations;
ground access to many sites by heavy equipment may be impossible, and the severity
of mountain physiognomy may preclude its ure. Equipment used in cleanup opera-
tions may be restricted to that which can be packed in or parachuted. Air removal
of contaminated materials may be the only feasible method. For these reasons,
methods based upon (or partially utilizing) the management and manipulation of
natural features and phenomena (see discussion of the Nival Phase of the Aeolian
Zone) at the site, such as snow cover and water runoff, may be desirable from
the standpoints of logistics, economics and ecology. The impact of devices to
manage wind, snow drift and water runoff would, be variable with their design
construction and placement. It is expected that their major impact would be upon
the abiotic phase of the environment (erosion, etc.) and that the impact of
such devices upon the life forms of the aeolian zone would be minimal.
The following discussion of suggested cleanup techniques will be generally
limited to the aeolian life zone. Some of the comments might also have limited
application to steep mountain slopes and peaks in lower life zones or in a
desert environment.
5-21
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(0-1) Uati&al Rehabilitation
Little has been published on the topic of natural rehabilitation of per-
turbations to the aeolian mountain peak environment, making the estimation of
recovery time from a spill cleanup operation rather difficult. "Natural re-
habilitation" would depend largely upon the rates of two processes: dispersion
of spilled material by wind and water and the rate of decay of spilled material
that becomes trapped in rock crevices, snow and ice. These processes could be
quite rapid or very slow, depending upon the properties of the spilled material
and climatic conditions at the site.
(1-1) Chemical Stabilization
Soil stabilization by the addition of chemical stabilizers to the surface
is probably not a viable treatment in the aeolian mountaintop environment.
(1-2) Clear Cutting Vegetation ("Removal")
This technique, applicable in many life zones, will be generally inapplicable
in the aeolian environment. With the exception of lichens, fungi, and certain
algal species, there is no vegetation present. The removal of lichens from rock
surfaces or algae from cliff faces, snow, or ponds probably will have little
lasting impact upon the ecosystem, with the exception that lichens probably
will be very slow to become reestablished. It is unlikely that the removal of
lichens will have measurable effects upon temperature, radiation, soil moisture,
precipitation, or surface runoff. Removal of algae from snow or ice may increase
surface albedo, thereby decreasing surface temperatures and runoff; this treat-
ment might possibly affect the microclimate. The possibility of controlling snow
surface temperatures by dusting with various materials has been studied. Removal
of algae from cliff surfaces can increase surface erosion.
(1-3) Stumping and Grubbing
Not applicable to this land type.
(1-4) Scraping and Grading
Whether surface alteration techniques, such as scraping and grading with
"air-dropped" equipment, will be logistically possible on mountain peaks in the
aeolian environment is highly questionable. Surfaces are likely to be snow, ice,
5-22
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rock, and debris with little soil accumulation on steep slopes; some surfaces
might be almost vertical. High winds, precipitation, or dense cloud cover might
be present. The potential for an avalanche must be considered in some areas.
Under these conditions, manual labor might be the only effective resource,
as was largely the case in the Greenland "Broken Arrow" incident.
Removal of surface snow and ice can be expected to produce minimal lasting
impact. Surface scraping and grading of rock, soil, or debris will tend to
accelerate erosive action, the severity of which will depend upon the composi-
tion and slope of the surface. If the treatment increases the smoothness of the
surface, the potential for a snow avalanche will be increased. Severe altera-
tion of mountain peaks will produce a strong visual or aesthetic impact. Post-
treatment measures might be required to reduce the potential for erosion and
avalanches. Methods of afforestation and terra.cing might be considered for these
purposes. Depending upon the location of the spill, climatic conditions might
permit some degree of afforestation or vegetation above the timberline. Without
such measures, recovery, or return to the pre-treatment conditions, could be
quite slow. In fact, the net effect of the treatment might be to potentiate the
pre-treatment erosive condition. Erosive processes could be accelerated and
recovery might never occur.
(1-5) Shallow Plowing
Not applicable to this land type.
(1-6) Deep Plowing
Not applicable to this land type.
(1-7) Sail Cover Less than 25 am
Application of soil as a coverup type of treatment would not seem to be
applicable in the mountain environment because of steep slopes and rapid erosion.
Construction of mechanical retaining structures probably would be required. This
treatment might be possible behind glacial moraines and in small valleys but
contamination of ground water and subsequent flow to streams would appear to
render such treatments ineffective. Because of the absence of plant cover growth
in the aeolian environment, stabilization of such soil fill would be quite diffi-
cult.
5-23
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(1-8) Soil Cover 25 to 100 cm , ;,
Mot applicable to this land type.
(2-1) Remove Plow Layer
Removal of soil (if present) will increase exfoliation and erosion of the
underlying rock surfaces by making them accessible to temperature extremes and
alternation between freezing and thawing. As discussed in Section 5.1.2.3, the
daytime sun and shade temperature differential on a mountain peak can exceed
70°F. Snow removal would be expected to produce similar effects. Reference to
the particulate adsorptive properties of snow was made earlier in Section 5.1.2.1,
(2-2) Remove Shallow Root Zone
A "root zone" in the sense used in other ecological zones does not exist in
the aeolian mountain peak environment. The comments in 2-1 will apply to
soil removal to depths usually thought of as the root zone.
(2-3) Remove by Scraping and Grading, Mechanically Stabilize
Removal of soil and rock by scraping and grading, if logistically possible,
would probably serve to increase erosive processes. Mechanical stabilization in
the sense of soil compaction would probably not be applicable to many sites in
this zone. Partial stabilization by methods analogous to those used in trail
maintenance may be possible, but their long-term effectiveness is questionable.
(2-4) Remove Plow Layer., Mechanically Stabilize
The mechanisms for thermal fractures of newly exposed surface rock were
described earlier in treatment 2-1. For this land type, the feasible mechanical
stabilization would be the temporary system of rock-weighted mesh and drilled
pins in lead anchors or the use of "rock-bolts." Mechanical stabilization of
soil patches by a soil compaction process would be quickly exfoliated by frost
heaving and cannot be recommended here. Large areas would be prohibitive to
cleanup, and "recovery" in this context would be an indefinable term.
5-24
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(2-5) Remove Shallow Root Zone, Mechanically Stabilize
This combined treatment is inappropriate for the aeolian mountain peak
environment.
(2-6) Remove by Scraping and Grading, Chemically Stabilize
Soil removal followed by chemical stabilization would mitigate some of the
consequences of rill and gravitational creep erosion caused by slope steepness
until the chemicals break down under ultra light exposure. This breakdown is an
indeterminate result and highly dependent upon the cumulative duration of snow
and ice cover, and particularly dependent upon slope aspect.
The removal of spilled material by scraping and grading of hard surfaces
is subject to those points discussed in treatments 2-1 through 2-3. The effec-
tiveness and consequences of chemical stabilization would depend upon the nature
of the site and the properties of the stabilizing material. The use of these
methods in areas subject to severe erosive forces is questionable.
(2-7) Remove Plow Layer., Chemiaallii Stabilize
This treatment is inappropriate for the same reasons as treatment 1-4.
Chemical stabilization would be less effective than weighted mesh upon those
patches where some soil has collected.
(2-8) Remove Shallow Root Zone, Chemically Stabilize
This treatment is not appropriate.
(3-1) Barriers toExclude People
If the supporting posts can be bolted into rock to support the ice during
snow melt, this might be the most realistic temporary procedure while cleanup
is carried out. Access barriers might be necessary at greater distances from
the primary spill site than for other life zones. Because of the absence of
protective vegetative cover, rapid transport of spilled material by water and
dissemination by wind can occur immediately after the spill; the spread of con-
tamination to locations remote from the primary site is a definite possibility.
5-25
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Due to the high danger of spreading of spilled material by wind (in the
absence of protective plant cover) and water to sites downslope and/or possibly
remote from the primary location, erection of barriers some distance from the spill
may be necessary. It may be necessary to restrict access to lakes and streams at
lower elevations in the watershed. Valleys at the base of a mountain peak spill
site may be subject to wind contamination. Assessment of the dangers of such
spread will have to depend upon local evaluation of the site and consideration
of the properties of the spilled materials.
(3-2) Exclude Large Animals
The erection of animal access barriers might or might not be necessary,
depending upon the site location and altitude. Barriers excluding large animals
probably would not be necessary for spills in the aeolian environment since it is
far above their normal range. It is unlikely that animals will interfere with
the recovery of a treated area, however, they can act as a vector for direct
dissemination of radioactive materials.
(3-3) Exclude Large and Small Animals
Small animals in the lower portion of the aeolian zone are generally
limited to a few reptiles and insects; these are discussed in the first part of
this chapter. Birds, which are occasional visitors to this life zone (also
discussed earlier in this report), can be problematical.
(4-1) Asphalt Hard-Surface Stabilization
Outside the scope of work of this study.
(4-2) Concrete Hard-Surface Stabilization
Outside the scope of work of this study.
(5-0) Application of Sewage Sludge
Outside the scope of work of this study.
(6-1) High-Pressure Washing (<3 mm)
Not applicable to this land type due to logistics and recontamination
problems.
5-26
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(6-2) Flooding to 30 am
Not applicable to this land type.
(7-0) Soil Amendments Added
Outside the scope of work of this study.
5.4.2 Alternative Treatment Techniques
Severe climate is characteristic of this zone with high velocity winds
and severely eroding steep slopes at those seasons free water occurs. Snow
blasting can redistribute contaminants impacted on high vertical surfaces
without interference but horizontal movement can be influenced by diverting
melt water with structures, and snow may be managed or directed while in
motion.
(8-1) . Snowfences and Wind Barriers
These structures can be of temporary benefit in reducing snow accumula-
tion at one small area by holding it in another site. The wind shadow extends
leeward 10-15 times the height of permeable barriers. By rule of thumb, a
solid wall 0.75 meters high protects the adjacent surface from snowblast and
wind erosion to 10 meters downwind and a snowfence 1.2 meters high and of
about 50% frontal area casts a wind shadow 12 meters downwind. The most
effect is obtained with a rough edge. Wind velocity is least near the ground
at 3 to 5 barrier heights on the downwind side of both solid and penetrable
barriers. Effectiveness of the barriers and snowfences seems independent
of wind speeds, at even high velocity if the barrier is vertical. The principal-
problem with barriers is that of determining the perpendicular to the direction
from which the prevailing high winds scour a given area consistently.
(8-2) Watershed Control Devices Constructed
The usual operations of shaping by clearing (1-2) , scraping and grading
(1.-4, 2-3, 2-6), and revegetation are not viable in this ecosystem as ways of
controlling movement of contamination in water. Streams are torrential and
mudflows scour deeply in above-freezing weather. The high kinetic energy
5-27
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requires that manual construction methods or small air-freighted equipment
of limited capability be used for the diversion structures. These can include
stone riprap and diversion dikes and stone gabions across rills and smaller
channels. Contoured terraces, stone walls and check dams, and rock outfalls
may be feasible as aids in containment when the contaminated area is snow-free.
Grade stabilizing structures such as chutes and stone drop spillways can be
supplemented by stone levees to modify smaller stream channels and reduce
erosive cutting into contaminated "soils" and snowbanks. None of these appear
to be effective controls in areas with landslides, avalanches, and even severe
snow blast.
(8-3) Snow and Ice Additives
The application of dusts to snow and ice to retard or enhance melting
can be useful. Experience with dusting charcoal dusts and lamp black powders
over snow and ice showed significant increases in melt rates. That observation,
when taken with the observation that deposits of solid particulates are captured
while melting occurs, suggests a unique procedure for reducing the volume of
i
snow to be cleaned up. The transportation requirements for dusting material
are modest enough to be handled by backpackers, small fixed-wing aircraft,
or even avalanche-prevention artillery rifles. Subsequent snow cover cancels
the effectiveness of the dusting, but it can be renewed again repeatedly. On
the other hand, the potential of reducing melt rates by foamed polyurethane
insulation blankets seems not to have been tested experimentally in snowfields
as a containment technique. In thoery it would be an effective method for
isolating small areas of contamination from heat and winds.
(8-4) Removal of Contaminated Snow and Ice
The logistics of travel in the area seem the most likely source of environ-
mental damage. Melting ice and packed snow requires heat, but given air support,
fuel tanks can be supplied and the contamination concentrated by melting the
snow and ice carrier. The characteristics of the contamination would control
the selection of resin column adsorbers, or using alcohol gels or thixotropic
mixtures for containerizing the contamination prior to transportation. Reflec-
tive surface solar stills would also be effective as concentrators where sunlight
is available because of the high light intensity at high elevations.
5-28
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5.5 RECOVERY AFTER CLEANUP , .>-.
The applicability of the term "recovery" to both the biotic and abiotic
components of the aeolian zone and mouritaihtop environment was discussed at
the beginning of Section 5.4 on cleanup procedures. The following discussion
is subject to the same reservation's.
5.5.1 Irreversible Changes
Any treatment that drastically alters the shape or surface of the mountain
peaks or slopes or greatly increases the rate of erosion in the barren ecosystem
under discussion, can for all practical purposes be considered as irreversible.
Destruction of habitats or extremely slow-growing life forms as lichens might
be considered to be irreversible from the standpoint of the human lifespan. There
is little data on the growth rate of these organisms in the aeolian environment.
5.5.2 Rates of Recovery
There is insufficient data available from cleanup procedures to provide a
meaningful discussion of recovery rates of the aeolian mountaintccp environment.
The abiotic components of the ecosystem might not recover, per se, but will
instead establish new rates of erosion which incorporate changes brought about by
the cleanup procedures. The degree of the effect will depend largely upon the
severity of the severity of the treatment implemented.
With respect to the biotic components of the aeolian system, it can be
inferred from observations on the establishment of lichens in areas uncovered from
permanent snow that recovery for these organisms will be extremely slow. Algae,
if removed from cliff surfaces, or with snowpack, probably will be able to be-
come reestablished in a relatively short period of time. If food sources for
zoological components of the aeolian environment are removed from the spill
area, it can be expected that their reestablishment (dependent upon buildup
of concentrations of organic materials of aeolian derivation) will be slow in
some cases and rapid in others. Lizards that depend upon windblown insects
might be able to become reestablished in a treated area within a few generations;
aeolian insects, dependent upon collected organic materials in cracks and crevices,
might require many years to become reestablished. There is insufficient data to
speculate upon the recovery rate of snowworm populations that might be depleted
or eliminated with the removal of contaminated snow during the cleanup process.
5-29
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5.5.3 Successional Stages -
The "recovery" events that occur within arbitrary "successional stages" will
vary greatly depending upon the location, situation, season of the spill, 'and the
treatment applied. The discussion here will apply only to the biotic phase of the
environment. It is emphasized that there is little data or precedence for these
estimates, and that they are essentially educated guesses. Deterioration can be
expected for the abiotic phase of the system; the rate will depend upon the loca-
tion of the spill and the nature of the treatment. Since lichens are the most
visible biotic component of the aeolian mountain environment, their recovery
will be assumed to essentially signal the "recovery" of the biotic component.
5.5.3.1 First Year
In the first year, regeneration of disturbed, removed, or destroyed microbial
forms, including algae on cliffs and snow fields, probably will be well underway.
It is assumed that these organisms are reasonably well adapted to the environment
and enjoy relatively short generation times. Higher forms of animal life that
are mobile and can subsist on windblown insect.s might have begun to reinvade
the treated area.
5.5.3.2 Fifth Year
By the end of the fifth year, the microbial lifeforms will be well established
and the higher animal life forms probably will have recolonized the niches able to
provide sufficient food. If algal forms were removed from cliff faces during
the treatment, they also probably will be reestablished, although the thickness
of their "mat" probably will not be fully developed.
5.5.3.3 Tenth Year
By the end of the tenth year, there should be sufficient accumulation of
windblown organic debris in cracks and crevices to permit survival of small
populations of those species of spiders, mites, etc., that utilize this nutri-
tional source. Algal mats should be well developed on cliff faces (if there is..
a favorable habitat in the cleanup area). Vertebrate populations (lizards)
probably will have attained equilibrium by this time. With the exception of the
slow-developing lichens, the biological climax populations of the aeolian life
5-30
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zone should be well on the way to recovery in the treatment zone, assuming that
the treatment did not leave residual chemicals or mechanical structures. By the
tenth year, small lichen colonies may be reestablished over the treatment area,.
if lichen growth preexisted the treatment and lichen growth was completely removed
during the treatment.
Speculation beyond this time period seem:; meaningless because, in the absence
of protective vegetation sufficient to provide stable microhabitats, changes in
climatic patterns might occur that are great enough in magnitude to alter the
environment and its biota. If lichen growth preexisted.the treatment, it should
be reasonably recovered by the 100th (or perhaps by the 50th) year, subject to ."'
the factors discussed earlier in this section. . '
5.6 QUANTITATIVE ASSESSMENT OF CLEANUP IMPACTS '
Environmental forces are asserted differentially in the aeolian mountain
from "normal" zones, and the effects of recovery from cleanup are evaluated
differently. Lack of soil cover throughout and the absence of flowering
plants lends a restricted meaning to recovery. In the following discussion,
recovery means that the rate of erosion of surface features has been slowed to
the rate of loss that existed before contamination. The eroding surfaces
may be snow fields, snow banks, aeolian mineral drifts from rock, ice features,
rock faces, or other surfaces, including patches of frozen and unfrozen "soils."
Life forms that exist year 'round are sophisticated, such as lichens and
snow worms or primitive bacteria and algae. Transient populations of insects
attract scavenger birds temporarily into the aeolian peaks.
Wind-drifted mineral deposits collected around rocks and ice features
and on and in snowbanks form the sites for "soil" accumulation. Soils and
vegetation in the normal sense are absent. In their place are patches of
rock-weathering products combined with wind-drifted solids to form mineral
pockets of a few square meters in area. Continuous areas of soil patch as
large as 0.01 km are rare, and for discussion of larger areas to 0.1 and 10 km2
of cleanup, the effects must be imagined as imposed upon an increasing number of
patches scattered around one or several mountain peaks. Consequently, the
impacts from the effects of cleanup are those registered upon small mineral
patches whether it is one patch or large numbers of "soil" patches among
bare rock and snow and ice fields.
5-31
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The majority of the cleanup treatments evaluated in the report are in-
appropriate in this zone, especially those which involve the redistribution
of soils (1-3, 1-6, I-?, and especially 1-8).
Use of stabilizers is judged ineffective without there being precedent to
judge from. This area is considered significantly different from spoil banks
at lower elevations. At those sites particle size ranges exist, and the surface
dries off after precipitation. In the mountain, piles of aeolian debris are
intermittantly soaked or ice sheathed where chemical stabilizers are unlikely
to stick, and it is not likely that sublimation is an effective drying agent.
Single-grain coarser material is filled with rock fragments or covered with
rock too large to hold in place with sprayed solution. No effective use can
be projected for treatments 1-1, and 2-3 through 2-8. Thermal problems with
chemical stabilizers are extreme at these heights.
Five groups of time to recover are shown in Table 5-2. These rank
as groups from most destructive but acceptable at some sites (1-4, 2-1, and
2-2); through less destructive, if considered to apply only to lichens (1-2
and 1-5); then, potentially destructive, but not required to be (8-2). These
are the cleanup techniques that can take a century or more to repair.
Impacts only fractionally as retrogressive are imposed by Treatments 8-1
and 8-3 and mainly on solid precipitation. Removal of contaminated ice or
snow is ranked in this same time span. The non-impact cleanups are the
barriers (3-1, 3-2, and 3-3).
In Table 5-2 the operations of clear cutting (1-2) and shallow plowing (1-5)
are restricted to scraping lichens from their support. In this snow-blasted
and windy zone, ten years may pass before recplonization occurs, and one or
several centuries are likely to pass before a full-standing crop is established
again. This is a drastic cleanup and has the longest recovery time of the
likely treatments on vegetated sites. Similar effects and recovery are
attributed to treatment 1-5 when applied to lichens.
The most drastic cleanup after-effects upon the environment derive from
removal of the aeolian "soils" in treatments 1-4, 2-1, and 2-2. Replacement
with additional aeolian debris to an equivalent depth is postulated to take
one to several centuries. If treatment 8-2 were to be constructed of these
5-32
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5-33
-------
"soil" materials it would be rated equally damaging. The recommended con-
struction materials are rock fragments for the structures proposed to divert
snow melt.
Stone filled diversions created from tatus (8-2) are expected to be
restored in a few years by natural rock-falls. Except for the potential for
misuse of soils, this technique would be rated as little impact, as are
Treatments 8-1 and 8-3. Installation of fences (8-1) to create drifts and
melting of snow and ice (8-3) are rated benign as is removal of contaminated
snow and ice (8-4). High pressure hosing down with water (6-1) has little
impact if the logistics of obtaining the required water is met by an environ-
mentally benign way.
The procedures judged least destructive are shown in Table 5-2 as
barriers, mainly barriers to keep people out (3-1) and a few transient animals
that may pass through (3-2, 3-3). Damage during barrier installation is pre-
sumed minimized and remedied by solid precipitation cover in a few months.
The effect of increasing the area of cleanup can only be visualized as
including additional numbers of discrete and overall cleanup sites because
of the terrain being limited in area. The impacts and the times to recover
are area independent due to frequent transitions from ice to rock to snow
cover.
5.7 CONCLUSIONS
Because of the complete lack of vegetative cover and the extreme severity of
physiographic and climatic factors in the aeolian mountain peak environment,
most of the conventional cleanup procedures considered for other terrestrial life
zones and environments appear to be either inapplicable or logistically impracticable,
and probably would be minimally effective. For these reasons, and the fact that
precedents for perturbations of this environment and recovery therefrom are ex-
tremely rare in the literature, accurate quantitative estimation of the impacts
of these treatments would be difficult. It might appear that alternative treat-
ments that are applicable to the aeolian mountain peak situation should be
devised as a separate study, and their impacts then considered. Possible alterna-
tive avenues of approach have been mentioned in this report. With respect to
"conventional" cleanup procedures, those involving surface alteration and hard-
5-34
-------
surface stabilization appear to have the most lasting impacts. The severity of
impact and the amount of time required for "recovery" varys depending upon the
location and precise situation of the spill and the exact nature of the treat-
ment imposed.
It is suggested that alternative techniques for immediate containment
and subsequent cleanup which are suited to the aeolian mountain peak situation
be devised. These techniques would be more effective and less detrimental than
those methods devised for other environments.
The preferred treatments are those involving barriers (3-1, 3-2, 3-3) and
removing contaminated snow or ice (8-4). The least suitable treatments are
those which strip the lichens from surfaces, and defined this way are Treat-
ments 1-2 and 1-5, although they are not physically the most destructive.
5-35
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5.8 AEOLIAN MOUNTAIN PEAK REFERENCES
1. Al'benskii, A. V. and P. D. Nikitin. Handbook of Afforestation and Soil
Melioration. 3rd ed. (Gosudarstvennoe Izdatel'stvo Sel'skokhozyais-
tvennoi Literatury, Moscow: 1956.) Translated from Russian by Israel
Program for Scientific Translations. Jerusalem, 1967.
2. Armstrong, R. A/- Studies on the Growth Rates of Lichens. In: Lichenology:
Progress and Problems. D. H. Brown, D. L. Hallsworth and R. H. Bailey,
eds. London: Academic Press, 1976.
3. Arnold, K. C. An Investigation into Methods of Accelerating the Melting
Ice and Snow by Artificial Dusting. In: Geology of the Arctic.
G. D. Raasch, ed. University of Toronto Press. 11:198-1013, 1961.
4. Aulitzky, H. Forest Hydrology Research in Austria. In: Forest Hydrology.
W. E. Sopper and H. W. Lull eds. Oxford: Permagon Press, 1967.
5. Aulitzky, H. Significance of Small Climate Differences for the Proper
Afforestation of Highlands in Austria. W. E. soppef and H. W. Lull
eds. Oxford: Permagon Press, 1967.
6. Bailey, R. H. Ecological Aspects of Dispersal and Establishment in Lichens,
In: Lichenology: Progress and Problems. D. H. Brown, D. L. Hallsworth
and R. H. Bailey, eds. London: Academic Press, 1976.
7. Bettler, G. T. The Plant Ecology of the Drakensberg Range. Nat'l Museum
Ann., v. 3, pp. 511-565, 1964.
8. Billings, D. W. Arctic and Alpine Vegetation: Plant Adaptations to Cold
Summer Climates. In: Arctic and Alpine Environments. J. D. Ives and
R. G. Barry, eds. London: Metheuen $ Co., Ltd., pp. 403-443, 1974.
9. Bond, E. K. Plant Disseminules in Wind Blown Debris from a Glacier in
Colorado. Arctic Alpine Res. 1, 165-169, 1969.
10. DeQuervain, M. R. and H. R. Der Gand. Distribution of Snow Deposit in a
Test Area for Alpine Reforestation. In: Forest Hydrology. W. E.
Sopper and H. W. Lull eds. Oxford: Permagon Press, 1967.
11. Dingwall, P. R. Erosion by Overland Flow on an Alpine Debris Slope. In:-
Mountain Geomorphology. Slaymaker, 0. and McPherson, H. J., eds.
Vancouver: Tantalus Research, 1972.
12. Dortignac, E. J. Forest Water Yield Management Opportunities. In: Forest
Hydrology, W. E. Sopper and H. W. Lull, eds. Oxford: Permagon Press,
1967.
5-36
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13. Dyunin, A. K. Fundamentals of the Mechanics of Snow Storms. In: Physics
of Snow and Ice. International Conference on Low Temperature Science
Proceedings. Sapparo, Japan, pp. 1065-1073, August 1966.
14. Gams, H. Die Herkunft der Hochalpinen Moose und Flechten. Jahrb. Ver.
Schutre Alpenpflanz. Munchen 25, 1-11, 1960.
15. Gary, K. L. Airflow Patterns and Snow Accumulation in a Forest Clearing.
West. Snow Conference Proc. 43:106-113, 1975.
16. Gregory, P. H. The Microbiology of the Atmosphere. New York: Wiley
(Interscience), 1961.
* ,
17. Grove, C. S., Jr., S. T. Grove, and A. R, Aidun. The Theory and Use of
Aqueous Foams for Protection of Ice Surfaces. In: Ice and Snow Pro-
perties, Processes and Applications. W. D. Kingery, ed. Cambridge-
M.I.T. Press, pp. 666-684, 1963.
18. Hale, M. E. Jr. The Biology of Lichens. London: Edward Arnold (Publishers!
Ltd., 1967. 176 pp.
19. Hutchinson, G. E. The Ecological Theater and the Evolutionary Plan. New
Haven: Yale University Press, 1965.
20. Kappen, L. Response to Extreme Environments. In: The Lichens. V. Ahmndjian
and M. E. Hale, eds. pp. 289-400. New York: Academic Press, 1973. 697 pp,
21.
Llano, G. A. The Terrestrial Life of the Antarctic. Sci. Am. 297-212-230
1962. '
22. Luty, E. T. and R. W. Hoshaw. Airborne Algae of the Tucson and Santa
Catalina Mountain Areas. Journal of the Arizona Academy of Science
pp. 179-182, 1967.
23. Mani, M. S. Introduction, to High Altitude Entomology. London: Methuen,
24. Margaropoulos, P. Woody Revegetation as a Pioneer Action Towards Restor-
ing of Totally Eroded Alopes in Mountainous Watersheds. In: Forest
Hydrology. W. E. Sopper and H. W. Lull, eds. Oxford: Permagon Press,
25. Martinelli, M. Jr. Snow Fences for Influencing Snow Accumulation. In:
The Role of Snow and Ice in Hydrology. Syrap. on Measurement and Fore-
casting Proceedings. Banff, Alberta. 1972. Handout, pp. 1394-1398.
26. Martinelli, M. Jr. Possibilities of Snowpack Management in Alpine Areas.
In: Forest Hydrology. W. E. Sopper and H. W. Lull, eds. Oxford:
Permagon Press, 1967.
27. Mattick, F. Die Flechten als Ausserste Vorposten des Lebans in Gebirge.
Montagne e Uomini, 2, 494-6, 1950.
5-37
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28. May, R. F. and W. D. Striffler. Watershed Aspects of Stabilization and
Restoration of Strip-Mined Areas. In: Forest Hydrology. W. E. Sopper
and H. W. Lull, eds. Oxford: Permagon Press, 1967.
29. O'Loughlin, C. L. A Preliminary Study of Landslides in the Coast Mountains
of Southwestern British Columbia. In: Mountain Geomorphology. 0. Slay-
maker and H. J. McPherspn, eds. Vancouver: Tantalus Research Ltd.
30. Osburn, W. S. The Dynamics of Fallout Distribution in a Colorado Alpine
Tundra Snow Accumulation Ecosystem. In: Radioecology. V. Schultz and
A. W. Klement eds. M.Y.: Reinhold and Am. Inst. Biol. Sci. Publ., 1963.
31. Osburn, W. S. Jr. The Impact of Technology: Large Scale Examples. In:
Arctic and Alpine Environments. Ives, J. D., ed. London: Methuen,
1974.
32. Owens, I. F. Morphological Characteristics of Alpine Mudflows in the
Nigel Pass Area. In: Mountain Geomorphology. 0. Slaymaker and H. J.
McPherson, eds. Vancouver: Tantalus Research Ltd., 1972.
33. Perla, B. I. and M. Martinelli, Jr, Avalanche Handbook. USDA Forest
Service. Agriculture Handbook 489, 1976. 238 pp.
34. Schaerer, P. A. Terrain and Vegetation of Snow Avalanche Sites at Rogers
Pass, British Columbia. In: Mountain Geomorphology. 0. Slaymaker
and H. J. McPherson, eds. Vancouver: Tantalus Research Ltd., 1972.
35. Shiotani, M. and H. Arai. On the Vertical Distribution of Blowing Snow.
In: The Physics of Snow and Ice. pp. 1075-1083, 1967.
36. Swan, L. W. Some Environmental Conditions Influencing Life at High Alti-
tudes. Ecology 33:109-111, 1952.
37. Swan, L. W. Aeolian Zone. Science 140:77-78, 1963.
38. Swan, L. W. Alpine and Aeolian Regions of the World. In: Arctic and Alpine
Environments. H. E. Wright, Jr. and W. H. Osburn, eds. Indiana
University Press, 1967.
59. Tabler, R. D. Predicting Profiles of Snowdrifts in Topographic Catchments.
West. Snow Conference Proc. 43:87-97, 1975.
40. Tabler, R. D. Evaporation Losses of Windblown Snow, and the Potential for
Recovery. West. Snow Conference Proc. 41:75-79, 1973.
41. Tabler, R. D. and R. A. Schmidt. Weather Conditions that Determine Snow
Transport Distances at a Site in Wyoming.. In: The Role of Snow and Ice
in Hydrology, pp. 118-126, 1973.
42. Wangersky, P. J. The Organic Chemistry of Sea Water. Am. Scientist. 53:
358-374, 1965.
5-38
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43,
44,
45,
46.
Whittaker,.Robert A. Communities and Ecosystems. Macmillan Publishing
Co., Inc. 1970. 385 pp.
Williams, G. P. and L. W. Gold. The Use of Dust to Advance the. Breakup
of Ice on Lakes and Rivers. East. Snow Conference Proc. 1963. pp 31-60.
(Also available as: Tech. Paper 165. Division of Building Res. Nat. Res.
Council of Canada, Ottawa.)
Wilson, A. T. Organic Nitrogen in New Zealand Snows. Nature 183:318-319
1959.
Wilson, A. T. Surface on the Ocean as a Source of Airborne Nitrogenous
Material and Other Plant Nutrients. Nature. 184:99-101, 1959.
5-39
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CHAPTER 6
TUNDRA
6.1 OVERVIEW
Tundra, which in Russian-Finnish usage referred to the treeless zone of
northern Eurasia, especially Finland, was subsequently applied to its counter-
part in the Arctic and Alpine North America. The Soil Conservation Society of
America defines tundra as "the treeless land in arctic and alpine regions;
varying from bare area to various types of vegetation consisting of grasses,
sedges, forbs, dwarf shrubs, mosses and lichens." It is generally considered
that the tundra vegetational life-form represents the integrated effect of
primary climatic parameters. From a practical point of view, tundra should be
defined by combinations of physiognomy and environment. In this definition
the tundras are the grassless arctic plains, the vegetation of which may form
varied and often complex patterns of dominance by dwarf-shrubs, sedges and
grasses, mosses, and lichens. The tundras of North America and Eurasia are
quite similar; their principal herbivorous mammals include the musk ox, cari-
bou, arctic hare, and lemming. Longspurs, plovers, snow bunting, and horned
larks are characteristic birds; reptiles and amphibians are few or absent, as
in alpine grasslands. In many tundras the deeper layers of soil are perma-
nently frozen, and only the surface soil is thawed and becomes biologically
active during the summer. The semi-arid areas of the Arctic are generally
considered as part of the tundra.
Dagon stated that the variety of definitions and the resultant misunder-
standing accompanying the application of the term tundra have been far too
numerous. He lists numerous definitions for the term and points out that there
is a great deal of ambiguousness associated with the use of the word tundra.
For the purpose of this report, the term tundra defined on the basis of its
physiognomy and environment is more appropriate.
6-1
-------
6.1.1 Geographical Distribution
Tundra lies between the northern limit of trees and the area of perpetual
ice and snow in the far north, or above timber line in high mountains. In
North America, it forms a broad band completely across the continent, and it
also occupies the narrow low coastal area around most of the periphery of
Greenland. It occurs on mountains as far south as Mexico if their elevation
is sufficient to produce a timber line. Thus it is limited in its northern
or upward extent by ice and bounded on the southern or lower margin by boreal
or subalpine conifer forest. The tundra is essentially an arctic grassland.
It is the cold polar area beyond the treeline in the northern circumpolar lands
of North America and Eurasia. The tundra vegetation and environment continues
southward along mountain alignments in western North America and Siberia. The
term tundra is further subdivided into Arctic and alpine. Alpine and Arctic
tundra are discussed in detail in the vegetation section (6.1.3) of this
chapter.
6.1.2 Environment
Low temperatures and a short growing season (about 60 days) are the main
characteristics of tundra environment. The ground remains frozen except for
the upper few inches during the growing season. The dominant factors which
shape the tundra environment are: the character of the solar energy input,
the nature of the immediate and adjacent surfaces, weather systems, and topog-
raphy. The annual and daily cycling of solar energy received on a unit surface
in the arctic tundra is quite different from that experienced at lower lati-
tudes. In general, tundra summer is limited to the three months of June, July,
and August; winter occupies the remainder of the year. Daily air temperatures
are generally below 10°C in summer but may rise occasionally to 20°C during
brief sunny spells. The mean daily range of temperature in summer is about 6°C.
The coldest months are December through April; the mean daily temperature in
tundra areas in February is about -30°C and the mean daily range varies from
about 10 degrees in continental areas to about 6 degrees elsewhere. Extreme
low temperatures of about -50°C occur, in the exposed tundra. Topography and
vegetative cover are probably important factors in the temperature regimes of
tundra environments.
6-2
-------
The tundra is often termed a "polar desert." Annual precipitation in this
area is indeed light. However, thawing of the active layer each summer causes
vast tracts of wet lands. By and large the annual rainfall is equal to the
water equivalent of snowfall. Normally there is adequate precipitation for
vegetative growth; deficiencies in moisture supply become critical only briefly
during the occasional summer droughts. Droughts have been sufficiently severe
to permit serious tundra fires to occur. Low evapotranspiration rates and the
presence of permafrost result in a large percentage of the precipitation run-
ning off into the tundra's poorly developed streams and stagnant ponds. It is
difficult to overemphasize the importance of the snow cover on the tundra
during the eight to ten months of the year. Snow is essential to the survival
of many plants and animals. In addition to being a source of water, snow acts
as a protective blanket to many plants and animals.
Wind plays a dominant role in the tundra. Strong winds are usually the
most critical.
Both plant and animal life exist precariously, mainly by taking refuge in
a particular microclimate environment and thereby escaping the rigors of gen-
eral climate. The microclimatic environment is in a delicate state of balance,
and alteration of this balance either naturally, or unnaturally, such as through
vegetative modification, may have serious consequences. For example, the alter-
ation of albedo can upset the energy balance at the soil surface and result in
thermokarst conditions. The removal of tall vegetation will result in increased
winds and shallower snow cover which may also significantly change the thermal
regime near and in the ground.
6.1.3 Vegetation
Tundra vegetation is low, dwarfed, and often matlike, and includes a high
proportion of grasses and sedges. Even the woody plants, including the willows
and birches, are usually prostrate. The herbs are mostly perennial and of a
rosette type, producing relatively large flowers, often with conspicuous colors.
Mosses and lichens may grow anywhere and in favorable habitats form a thick
carpet with the low herbs. The number of species is small compared with floras
of temperate climates; and, even within the tundra, the number decreases north-
ward. Most of the genera and many of the species are to be found throughout
the Northern Hemisphere wherever tundra occurs.
6-3
-------
The uniformity of the flora is undoubtedly related to the peculiarities
of environment. The growing season is short and its temperatures are relatively
low. Permafrost in the ground and its depth of thawing in summer is of great
importance as is the extreme instability of soil, related to the frost action.
Light is continuous throughout the growing season in the arctic tundra, and is
intense and high in the ultraviolet rays in alpine tundra. Local marked dif-
ferences in vegetation are commonly related to minor variations in topography
and differences they"produce in drainage and retention of snow.
The tundra ecosystem can be divided into (1) Arctic Tundra, and (2) Alpine
Tundra.
6.1.3.1 Arctic Tundra--
The circura-artic tundra can be regarded as comprising a simple formation-
type composed of Eurasian and North American formations. Even within the same
formation, however, in spite of superficial similarities, considerable con-
trasts are evident in both life-form and general appearance. Although flower-
ing herbaceous plants, particularly grasses and sedges, are almost universal
throughout all communities, dwarf shrubs, mosses and lichens compete successfully
in most places. Furthermore, there is a great contrast between the almost
closed-cover tundra communities near the forest margins and the scattered,
sparse communities on almost bare ground in the most inhospitable parts of
north Greenland and Spitzbergen.- It is clear also that not all the extensive
tundra communities are to be regarded as true climatic climax.
In the climatically more favored areas of the tundra, the true climatic
climax communities are probably those in which grasses and sedges are dominant
with a substantial understory of lichens and mosses. Communities of this
nature are found on undulating areas with a considerable range of slope, aspect
and lithology. The dominants in the American formation are various species of
sedge (Carex spp.), cotton grass (Eriophorum spp.), and woodrush (Luzula spp.),
along with species of many genera of grasses such as the bents (Agrostis spp.),
foxtail grasses (Alopecurus spp.), fescues (Festuca spp.), and timothy (Phleum
spp.) which are also of common occurrence in middle latitudes. The commonest
associated lichens belong to the genera Stereocaulon, Alectoria, Cetraria, and
Cladonia, while mosses of the genus Polytrichum are most frequently encountered.
Along with these are a great variety of plants with showy flowers belonging to
6-4
-------
genera which are also distributed throughout the woodlands and meadows of mid-
dle latitudes such as the anemones (Anemone spp.)» marsh marigolds (Caltha spp.),
buttercups (Ranunculus spp.), avens (Beumspp.), cinquefoils (Potentilla spp.),
campions (Lychnis spp.), catchflies (Silene sp>p,)j> a*«d primroses (Primula spp.)'
These are accompanied by flowers which are more typically associated with high
latitudes and high altitudes such as the mountain avens (Dryas spp.)> saxifrages
(Saxifraga spp.), and gentians (Gentiana spp.)- A varied cover of predominantly
herbaceous vegetation thus forms an almost complete turf over the ground.
Over very large areas, however, the grasses and sedges are much less im-
portant and dominance is assumed by foliose lichens and mosses, particularly
the former. This cover of cryptogams, if ungrazed, may be anything from four
to ten inches high and, in the more southern parts of the tundra, may be almost
continuous. Further north communities similar to the two already described
are much more discontinuous and a great deal of bare ground is found between
individual plants or plant aggregates. This type of vegetation has been most
vividly described in the Taimyr Peninsula by Middendorf. Here, in many places,
the ground is only about half covered by plants, permafrost is not more than
three inches beneath the surface in many places, and a varied patchwork of com-
munities is found. In places mosses (Polytrichum spp.) dominate; elsewhere
sedges or lichens (Cladonia spp.). Throughout all these communities, however,
there is an admixture of flowering plants, creeping shrubs such as the dwarf
willow (Salix lapponum) and xerophytic, heath-like shrubs such as the crowberry
(Empetrum nigrum). Even at the height of summer, when many species are in
flower, these communities give the landscape a drab or yellowish aspect. This
is partly due to the colors of the mosses and lichens, but partly to the fact
that many of the grasses and other flowering plants, as an adaptation to reduce
transpiration, retain the dead remains of last year's growth. Ultimately,
around the very fringes of ice caps and on some exposed sea coasts, the vegeta-
tion dwindles and only an occasional tussock of sedge or cushion-shaped plant
is to be found.
Dwarf shrubs occur sporadically throughout the communities already de-
scribed but locally shrubs become dominant. Usually, however, the shrubs, which
are subordinate elements in predominantly herbaceous communities, belong to
different species from those which form arctic heath and arctic scrub communi-
ties. In arctic heath the species are low growing, the Canadian communities
6-5
-------
being dominated by small shrubs such as the arctic bell-heather (Cassiope
tetragona), crowberry (Empetrum nigrum), and alpine bearberry (Arctostaphylos
alpina). In arctic scrub, on the other hand, quite a busy growth is attained
which may reach a height of several feet. It is dominated by broad-leaved
shrubs such as the narrow-leaved Labrador tea (Ledum palustre), Lapland rose-
bay (Rhododendron lapponicum), alder (Alnus sinuata), scrub birch (Betula
glandulosa), and numerous species of willow (Salix spp.)- Many communities are
found containing both these types of shrub, however.
Usually the arctic shrub communities are found on sheltered slopes, par-
ticularly where the soil thaws unusually deeply in summer and where it is rich
and moist. It seems probable that they constitute a zone of ecotone between
the more typical tundra communities on the interfluves and the outliers of the
forest on the lowest slopes. There is some evidence that, where trees are
nearby, invasion takes place sporadically in a series of favorable years only
to be rebuffed in a subsequent unfavorable period.
Finally, there is another suite of communities, covering extensive areas
in the tundra, which cannot be regarded as climatic climax; these are the tundra
bogs and moors. They are very similar in appearance and species-content to the
bogs or "muskegs" which occupy ill-drained localities within the general area of
the boreal forest. Very often in both Europe and America, they are dominated
by cotton grass (Briophorum vaginaturn) along with many other species of sedge
and some grasses. Usually also various species of moss, particularly bog moss
(Sphagnum spp.), compose a sub-dominant understory. The surface of these bogs
is usually "tussocky" and the tussocks of cotton grass and moss are frequently
invaded by dwarf willows. Indeed, at an advanced stage of development, when
the peat has achieved considerable thickness, the vegetation may become quite
luxuriant, similar in many ways to that of the better-drained arctic heaths.
These "heath moors,"-as they have been called, ensure a copious supply of
available moisture throughout the growing season and, at the same time, thaw
out to a sufficient depth to accommodate the rooting systems of shrubs. Apart
from the heathy shrubs, some broad-leaved, deciduous shrubs also invade this
kind of surface. In Canada, for instance, several species of birch (Betula)
and many of willow (Salix) are of frequent occurrence. It seems likely that
soil conditions here would be quite suitable for those species of tree which
regularly invade drying-out muskegs within the boreal forest areasspecies
6-6
-------
like the black spruce (Picea mariana) and the Canadian larch or tamarack
(Larix laricina). Indeed, if these species of tree were able to advance un-
interruptedly, along a solid front, across bogs in the southern parts of the
Canadian tundra, they would probably demonstrate their ability to survive the
climatic rigors there. Individual tree seeds which have been carried by the
wind have been observed to germinate here quite satisfactorily but have sub-
sequently been incapable of surviving the desiccating blizzards of winter.
Isolated saplings cannot survive but if they had the partial shelter of nearby
parent trees, they would probably be able to do so; the forest would thus en-
croach gradually. This cannot take place, however, since the deep peat areas
are separated from the forest edge by less favorable types of terrain.
The intense physiological drought of the winter months should be stressed
as a limiting factor in the tundra far more than mere low temperatures. If the
air always remained still, many of the northern trees could probably withstand
even lower temperatures than they do. Strong winds, even at very low tempera-
tures, are able to abstract water quite quickly from living plant tissues; if
this proceeds beyond a critical point, death ensues, since no replacements are
obtainable from the completely frozen soil. The plants of the tundra minimize
the danger of this in several distinct ways. On the most exposed areas, all
are very low-growing; many die down completely in winter and survive as under-
ground rhizomes, root stocks, corms and bulbs. Those herbaceous plants which
do maintain organs above ground level in winter do so in the form of very tight-
packed rosettes or cushions; many species of saxifrage do this very success-
fully. As a group, the lichens are noted for their ability to survive in an
almost desiccated state for protracted periods. It is understandable therefore
that they should form such an important element in the vegetation of many of
the bleakest and baldest arctic interfluves. The arctic shrubs are also low-
growing except in the most sheltered valleys. They have adopted different de-
vices to prevent over-rapid transpiration. Many of the broad-leaved ones are
deciduous (Salix, Alnus, Betula) while the heaths all have the characteristic
small leaves with rolled-back margins.
The shortness of the growing season also imposes great restrictions on
plant growth. It is mainly because of this factor that the flowering herbs of
the tundra fall into two classes; there are those which flower at the beginning
of the growing season and those which flower towards the end of it. The
6-7
-------
early-flowering species are typically plants with substantial underground food-
storage organs; they use the stored energy from the preceding year to flower
and produce seed and then utilize the remainder of the growing season to build
up food for the following year. The late-flowering species use the first part
of the season to build up a store of energy and then use most of it in produc-
ing seed; they then pass the winter as inconspicuous underground organs or, if
annuals, survive merely as seeds.
The factors of winter frost, winter winds, short growing season and perma-
frost are responsible, collectively or separately, for precluding trees from
the tundra. Because of contrasts in relief and aspect the relative importance
of these different factors varies greatly and an evaluation of the exact reasons
for the absence of trees in a particular place is usually obscure. However,
the complex inter-digitation of the southern edge of the tundra with the north-
ern edge of the forest indicates that, generally speaking, wind force along
with shallowness of unfrozen soil are the operative factors in the southern
parts of the tundra. Here, forests occupy the valleys while the interfluves
are tundra. Wind force is obviously important on these interfluves but,
whether forest would extend further up the slopes if the depth of the thawed
layer in summer were deeper is not clear. The existence of permafrost, as
such, does not preclude forest since vast areas of the northernmost parts of
the boreal forest are underlain by it both in Siberia and Canada; northern
species such as the Dahurian larch (Larix dahurica) and Siberian dwarf-pine
(Pinus pumila) are adapted to this soil condition in that they develop a root
system which is entirely spreading with no tap root whatsoever. In the north-
ern archipelago of Canada and the arctic peninsulas and islands of the U.S.S.R.,
as well as in the Spitzbergen and the north of Greenland, it appears probable
that trees cannot possibly regenerate regardless of wind and soil depth. Though
increase in the length of the season with continuous daylight does, to a cer-
tain extent, compensate for increased latitude, it is doubtful if the growing
season here is sufficiently long for trees. Even if trees could survive the
winter, it is very doubtful if they would be able, to flower and produce seed.
In these fringing areas, so near to perennial ice, there is no recognizable
frost-free season. Everywhere in the tundra the mean length of the frost-free
season is less than fifty days but here, in spite of continuous daylight, air
frosts occur frequently in all the summer months. Returning to the southern
6-8
-------
fringes of the'tundra, however, it is doubtful whether the length of, the frost-
free season has any bearing on the position of the limits of the, forest. Prob-
ably the length of the frost-free season is sufficient here to permit forest
regeneration but,wind speed in winter and extreme shallowness of soil in summer
prevent the spread of trees.
Fluctuations in the position of the northern edge of the boreal forest
have occurred during the past few millennia. Locally, in European Russia, a
distinctive fringing zone of ."tundra moor" has been described. Here, hummocks
of bog moss (Sphagnum spp.) peat, each several yards in diameter, with narrow,
marshy channels between them, cover the. landscape. The mosses on the hummocks
;are often still growing but the cores of the hummocks are permanently frozen.
This permanently frozen peat contains the stumps of both birches and conifers,
many of which are in position of growth. Clearly these areas were forested
not so very long ago but the reason for forest recession is not altogether
clear. Possibly a deterioration in climate was responsible; possibly, the
activities of reindeer herders along the former forest margins caused the sap-
lings to be grazed off and thus prevented regeneration; possibly both climatic
change and human activity played some part in the changes that occurred.
Although the flora of the tundra is fairly well known, its communities and
their successional relationships have not been sufficiently studied. In con-
trast with temperate vegetation, many species may occur in any type of habitat,
and several that appear to be climax may also be pioneers in the newest of
habitats. Even climax is not agreed upon, possibly because observations have
been made in widely separated areas. Variations do exist, as has been shown
for eastern Canada. It is also possible that the climax criteria used for
temperate climates are not always applicable in the arctic. Interpreted in
terms of Greenland vegetation, Cassiope heath appears to be climax, and a Sedge-
Dryas dominated community, of equal extent but on drier sites, is preclimax.
Two subclimaxes are frequent. Any habitat with sufficient moisture, whether it
be pond margin, seepage area, or boggy ground, eventually is covered with a
thick moss mat supporting several herbs, of which cotton grass (Eriophorum spp.)
is most conspicuous. Xerarch succession on rock exposures eventually results
in a lichen-moss mat, which may continue almost indefinitely. ,
Important climax dominants are Cassiope tetragona, one or more species of
Vaccinium, Archtostaphyloas alpina, Empetrum nigrum, Andromeda polifolia,
6-9
-------
Ledum palustre, Phododendron lapponicum, and species of Betula and Salix.
These and other species occur in varying combinations and degrees of importance.
Practically all habitats support some of the many species of Carex, of
which the commonest include C. capillaris, C. nardina, and C. rupestris. The
preclimax sedge community invariably includes Elyna bellardi in abundance.
Some grow mats, some are in clumps, but all are dwarfed. The same can be said
for the grasses, which, although relatively abundant and widespread, are re-
stricted to a few genera, of which Festuca and Poa are especially well repre-
sented. Many of the conspicuous herbs previously mentioned are included in the
numerous species of one of the following genera: Saxifraga, Potentilia, Ranun-
culus, Draba, Cerastium, Selene, Lychnis, Stellaria, and Pedicularis. Conspic-
uous and widespread species typical of tundra are Oxyria digyna, Papaver spp.,
Dryas octopetala, and Epilobium latifolium.
6.1.3.2 Alpine Tundra-
Mountains high enough to have timber line support tundra, whose upward
extent is limited by the snow line. In the east, as a consequence, tundra is
found only on a few high peaks in New England. Farther south, the Appalachians
are not of sufficient height to support tundra. That on Mt. Washington is
representative of the type and is essentially similar to the not far distant
arctic vegetation.
Alpine tundra in the western mountains mostly lies far to the south of the
arctic and, consequently, is found at high altitudes only. In the Canadian
mountains, it is found as low as 6,000 feet, but southward its lowest elevation
steadily increases some 360 feet per degree of latitude to 30° north latitude,
and then declines very gradually to the equator. In the central Rocky Moun-
tains, tundra is well developed between 11,000 and 14,000 feet. In the Sierra
Nevada, where the snow line is lower, tundra lies mostly between 10,500 and
13,000 feet. In general, it is lower on coastal than interior ranges and on
the wetter sides of mountains.
When climate changed arid terminated the glacial period, vegetation similar
to modern tundra must have followed the ice as it receded northward. This left
only these high peaks and ridges where tundra could survive as relicts. The
relict vegetation obviously belongs to the Tundra Formation because of the
6-10
-------
growth form and the duplication of characteristic genera as well as many species.
The greater importance of grasses and the presence of numerous endemics in the
western mountains suggest that these alpine tundras might be classed as asso-
ciations of the Tundra Formation.
23
Webber compared the composition and production of the vegetation at
Point Barrow (Alaska) and Niwot Ridge (Colorado). The apline tundra vegetation
on Niwot Ridge is twice as productive as arctic tundra (Point Barrow) but only
because of higher incoming solar radiation (Table 6-1).
6.1.4 Animal Life
The animal life in the tundra biome consists of caribou, musk ox, arctic
hare, lemming, longspurs, plovers, snow bunting, and horned larks. There are
very few, if any, reptiles and amphibians in the tundra environment. Though
vertebrate animals inhabiting arctic and alpine tundra environments are faced
with many similar environmental problems, such as low temperatures and scarce
cover, important differences between arctic arid alpine environments exist in
day-length and solar radiation patterns, topography and moisture, and other
physical factors of the environment. These differences in environment are
reflected in the distribution of animal life in the arctic and alpine tundra.
The differences occurring between arctic and alpine faunas are due not only
to real differences in the habitats available as a result of physical environ-
mental differences, but also to the much patchier "island" distribution of
alpine habitats in contrast to those of the more continuous circumpolar arctic.
6.1.5 Soils
Low temperatures and, in most places, the presence of an impermeable
perennially frozen substratum, are the dominant factors affecting the develop-
ment of soils of the arctic and alpine tundra,, The cold environment modifies
soil-forming processes to such an extent that it overshadows, and may even
completely obliterate, the effects of relief and time on soil characteristics.
Tundra soils are wet nearly continuously during the thaw period. In general,
the tundra soils can be divided into two groups: (1) poorly drained soils that
are usually saturated, and (2) well drained soils.
6-11
-------
Table 6-1. Comparison of arctic and alpine environments and vegetation.
Component
Latitude
Altitude (meters)
Average July solar radiation
(cal/cm2/min)
Maximum photoperiod
Maximum air temperature (°C)
Maximum soil temperature (°C)
Annual mean precipitation (mm)
Permafrost
Average length of growing period
(days)
Number of common vascular plants
Average area! vascular production
Arctic tundra
71°N
7
0.30
84 days
3.9
2.5
107
Universal
55
40
100
Alpine tundra
40°N
3749
0.56
15 hours
8.5
13.3
1021
Sporadic
90
100
200
(grams/m2/yr)
Average ratio of above- to
below-ground biomass
Average area! net photosynthetic
efficiency (percent)
1:8
0.5
1:12
0.5
6-12
-------
Poorly drained mineral soils of the tundra all have essentially the same
sequence of horizons. They consist, typically, of a mat of organic materials
at the surface; a grey, greyish brown, or bluish mineral layer which may be
mottled in whole or in part with colors ranging from olive or olive brown to
reddish brown and which may contain patches or streaks of organic matter; and
a grey perennially frozen layer which may have patches of organic matter in its
upper part. The description in Table 6-2 of a soil in northwestern Alaska
is representative. (Color and Munsell color notations are for moist conditions
unless otherwise noted. Depths are measured up and down from the surface of
the mineral soil.)
Well drained soils occur throughout tundra areas, but are of relatively
small total extent except in arid regions near the northern limits of vegeta-
tion. South of those regions they occur almost exclusively in stony, gravelly,
or coarse sandy materials on steep slopes, high narrow ridges, escarpment edges,
stabilized dunes and beach ridges, and elevated portions of flood plains. The
combination of coarse-grained materials and exceptionally good surface drainage
is, with rare exceptions, an essential condition for their existence. Either
bedrock or dry permafrost underlies these soils; where they are developed in
thick unconsolidated materials, solid permafrost may occur at greater depths.
The well drained soils differ from most soils of the tundra in that excess
moisture is able to escape.. As a resultj oxidizing rather than reducing
processes are dominant, and soluble products of weathering are redistributed or
removed from the soil. The rate of weathering, decomposition or organic mate-
rials, and movement of materials (that is, the intensity of soil development)
depend on temperature and the amount of moisture available. In the cold and
relatively arid arctic environment, these processes go on at a much slower rate
than in forested areas to the south. As a consequence, the soils that are
formed may have the same sequence of horizons as in comparable well drained
soils of taiga areas, but have much thinner hcirizons. In nearly all cases,
physical and chemical properties of the soils reflect those of the parent
materials.
The well drained soils vary in the kinds of horizons that develop, and in
the thickness and degree of development of the horizons. The soil described in
18
Table 6-3, from southwestern Alaska, is representative of the most extensive
of these soils. Colors are for moist conditions.
6-13
-------
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6-14
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6-15
-------
The principal horizons in this soil are the dark upper horizon and the
yellower subsoil horizon, which grades into the shaly parent material. The
soil is acid and low in exchangeable bases throughout. Chemical analyses in-
dicate the A12 horizon is slightly higher in free iron than both the All hori-
zon above it and the B horizon below it. A similar distribution of iron has
been noted in other soils of this kind,9' indicating that there is a tendency
in these soils toward the development of an iron-rich subsurface horizon. The
process of podsolization, in which iron, aluminum, and organic carbon are moved
in solution from the upper mineral horizon and reprecipitated in a lower hori-
zon, is common in soils of cool, moist, forested regions. In a few places in
tundra regions just north of the treeline where large quantities of water move
through coarse-grained soils, as in micro-depressions in uplands or protected
areas where snow accumulates, the process is also intensive. There the soils
have bleached upper horizons over thin horizons of iron accumulation. Soils
of this kind are more common in tundra areas immediately above treeline in sub-
arctic regions.
Soils developed in materials derived from basic rocks, such as basalt,
limestone, and calcareous shales, are similar in appearance to the acid soils
described above, but pH values and base saturation are high. In some places,
calcium carbonate has accumulated in the lower part of the soil.
With increasing distance from the treeline, the amount of organic matter
added to the soil decreases and, because of lower temperatures and lower pre-
cipitation, chemical and biological processes such as oxidation and huraifica-
tion proceed at a slower rate. Well drained soils in the colder tundra areas
may have only very thin or no dark upper horizons and thin brown B horizons.
In the far north, where precipitation rates are very low and the vegetative
cover is sparse, well drained soils that have no discernible horizon develop-
ment are dominant. Other soils with no horizon development are the young sandy
soils of active dunes bordering some major rivers and the very gravelly soils
of flood plains, low terraces, and steep colluvial slopes.
6.2 NATURAL PERTURBATIONS
6.2.1 Fire
Little is known of the role of fires in tundra ecosystem, yet they do oc-
cur. Fire removes most of the insulating layer of live vegetation and litter,
6-16
-------
damages or destroys the peat, and greatly changes the albedo of the surface.
The result is a potential rapid increase in thermal erosion with increased
runoff. A general account of vegetation recovery following a major fire in
the tundra is given by Cody.6 Nine years after the fire, grasses, sedges,
and forbs recovered fairly well but lichens and mosses showed little recovery.
With lichens playing an important role in the diet of caribou and reindeer, it
is evident that burned areas will be lost to grazing for many years.
6.2.2 Drought
The tundra ecosystem is subjected to frequent droughts. Droughts have
been sufficiently severe to permit serious tundra fires to occur. Any long
term drought patterns are expected to affect the structure and productivity of
an ecosystem.
6.2.3 Grazing
Overgrazing by the caribou and reindeer is quite common in the tundra eco-
system. These animals lead to selective removal of lichens through grazing.
Vegetation composition and density are affected considerably. In the tundra,
intense grazing activities tend to result in more woody and hardy shrubs.
6.3 MAN-MADE PERTURBATIONS
Disturbances to tundra vegetation due to activities of man derive from
both winter and summer roads, pipelines, seismic lines, drill sites, crude oil
spillage, tundra fires, living sites, and waste disposal.
The discovery of oil on July 18, 1968 near Prudhoe Bay on Alaska's arctic
coastal plain (the North Slope) and subsequent flurry of oil and gas explora-
tion and development have already had a pronounced impact on the tundra environ-
ment over a large area. In addition to the direct effects of oil development
on the North Slope, there will be subsidiary effects in other parts of arctic
tundra. Klein described the impact of oil development in Alaska. Detailed
descriptions of human impact of tundra are also given by Watson, Bayfield, and
Moyes22 and by Walker.21
Bliss and Wein examined 25 seismic trail sites in the Low Arctic. By
using control plots in adjacent vegetation, they were able to characterize
6-17
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the disturbance (Table 6-4). They concluded that wherever viable roots and
rhizomes of shrubs, sedges, or grasses remained in the disturbed substrate, a
30 to 50 percent recovery in natural plant cover will occur in 3 to 5 years.
Subsidence will occur in areas of high ice content. To date, there is little
evidence that immediate reseeding can prevent ground ice melt and subsidence.
Less detrimental effects from surface rutting and scraping were measured in
the High Arctic.
Table 6-4. Change in conditions caused by seismic lines and
winter roads with paired control plots in 1970
(adapted from Bliss and Wein3).
Community type
Shrub-sedge-heath
hummock
Hummocks
Wet sedge meadows
Spruce-alder
Upland winter road
Year
disturbed
1965
1967
1969
1969
1969
Increased
active
layer (cm)
26
8
1
10
7
Increased
bare soil
(percent)
63
25
5
98
100
Decreased
plant cover
(percent)
65
34
7
169
99
Revegetative studies are underway in several locations. Bliss and Wein
reported trails with 16 species seeded in 1970. At the rate of 20 kg per ha,
Festuca rubra, Poa pratensis, Poa compressa, and Phieuro alpinum have the best
results in establishment and winter survival on mineral and peat soils.
Alopecurus pratensis grew better on mineral soil. Fertilizer treatment with
100 kg per ha actual N and P205 doubled culm height over nitrogen fertilizer
alone. The authors recommend sowing seeds with snowmelt in the spring or be-
fore snowfall in the autumn.
Experiments with oil spillage on terrestrial vegetation are few. Bliss
and Wein3 reported that oil poured directly on the foliage killed those leaves
in contact with the oil in a few days. Some regrowth was evident in late sum-
mer from June treatment, but none from July treatment. Greater damage was
6-18
-------
evident in wet sedge and cotton grass tussock communities than in shrub com-
munities. Microbial activity in the soil may increase tenfold, but the impli-
cations of this activity for the nutritional status of the community are not
yet established. McCown and Brown applied oil to the soil surface (avoiding
foliage contact) and observed little immediate damage. Shoot growth response
of Dupontia through the summer was not suppressed, except at the heaviest
treatment of 12 liters per square meter, but root biomass seems to have been
reduced. Observations in the second growing season showed reductions in stems
per plot and in growth per stem. Carex aquatilis and Eriopjiorum angustifolium
seemed less sensitive than Dupontia. To the extent that effects of oil spillage
are manifest through limited root growth, vegetative response may not be appar-
ent in aboveground tissue for one or more years.
A study of the effect of an air cushion vehicle (SK-5) on tundra vegeta-
tion ' was measured quantitatively. The results clearly show that the exhaust
air blows the litter and loosens organic matter, but principal damage was
caused by dragging of the vehicle skirt on the surface. Although such effects
change the albedo, the direct visible damage by the air cushion vehicle after
25 passes was often less than that of a single weasel pass.
In general, any disturbance which eliminates or greatly reduces plant
growth, vegetative cover, or the organic litter or peat layer by any cause will
increase thaw depth as a result of increased solar heat flux. Greater under-
standing of response to disturbance in different landscape units is needed for
regulating land use and for providing design criteria for land vehicles.
6.4 EFFECTS OF CLEANUP PROCEDURES ON TUNDRA
The concept of the fragility of the tundra has probably been too uncriti-
cally accepted as a convenient shibboleth by conservationists, in order to
totally exclude resource development from the tundra. Undoubtedly, wet tundra,
which may contain frozen water up to five or six times in excess of dry soil
weight within the upper 40 meters, is fragile. This problem is rare in alpine
tundra. Degree of disturbance potential could be mapped on a regional scale
according to water content, grain size and vegetation physiognomy. However,
there are other reasons behind the concept of the fragile tundra that relate
specifically to plant adaptation and community structure and primary productivity
6-19
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considered both as daily rates and total season's production. Bliss" has argued
that the very limited number of plant species in the Arctic is a real indica-
tion of fragility of the ecosystem since adverse impact on a very few species
may damage the whole: the potential for recovery may be proportional to plant
Q
community variability. Dunbar emphasizes that a proper consideration of
"fragility" hinges on one's definition of stability. A steady-state situation,
which may pertain to. arctic lakes and perhaps also to tundra vegetation, is
vulnerable to excessive disturbance since the system cannot adapt. Another
type of stability is represented by a system which can absorb disturbance and
return to its previous state. Tundra animal populations undergo drastic fluc-
tuations but recover, perhaps as a result of their ability to draw on outside
areas. Dunbar concludes that simplicity of an ecosystem, coupled with slow
growth rates, leads to vulnerability to disturbance which can be tolerated only
if the spatial scale is large (as in the Arctic) and the time scale is suffi-
ciently long.
(0-1) Natural Rehabilitation
Natural rehabilitation after a contamination of land in the tundra environ-
ment is suggested as a high priority treatment for cleanup. Ecosystem recovery
tends to follow ecologically normal and predictable successional trends, i.e.,
patterns following daaage from most postulated contaminants are sinilar to those
following fire, logging, or shipping of top soil and other natural catastrophic
2
events. Bliss reported that nine years after a fire, grasses, sedges and forbs
recovered fairly well but lichens and mosses showed little recovery. It is as-
sumed that in case of a contamination of an area in the tundra environment,
ecological recovery will follow a different pattern. The area would still have
its litter and organic cover and will not be subjected to a deeper thaw during
summer. The vegetation in a tundra ecosystem has a higher below-ground biomass
production and would provide better soil binding against water erosion during
the summer thaws.
(1-1) Chemical Stabilization
The cleanup by chemical stabilization is to reduce the infiltration rate
and thereby reduce the mobility of contaminants into the vadose zone. The
chemical stabilization will not be practical in the tundra environment.
6-20
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(.1-2) Clear-cutting Vegetation ,
Removal of woody shrubs by clearcutting can be used as a possible technique
for cleanup. Along the Alaska pipeline route, the tundra vegetation was removed
by clearcutting of woody plant species and shrubs. In arctic and alpine envi-
ronments the plants are small, close to the ground, and often widely separated
by bare soil or rock. Unlike the situation within a forest, the modification
of microclimate by vegetation is minimal and the physical environment dominates
the vegetation. In such open and windy places, the effects of microenvironment
are pronounced. Even a few centimeters difference in microtopography makes a
marked difference in soil temperature, depth of thaw, wind effects, snow drift-
ing and resultant protection to vegetation. The microtopographic effects may
be caused by a rock, a soil polygon rim or by another plant itself. The re-
moval of larger vegetation plants would result in an uneven distribution of
snow and thus differential distribution of soil moisture, heat exchange, and
protection from windblast.
It is assumed that the clearcut areas will not be disturbed as far as the
litter and organic horizons of the tundra soils, and that the clearcut areas
will be replanted or reseeded.
General effects of clearcutting are described in the coniferous forest
land type (see Chapter 4). Clearcutting of the woody shrubs in a small area
within the tundra ecosystem can have extreme effects on the microclimate and
the hydrological factors, since so much of the alpine or arctic landscape is
characterized by scattered woody shrubs and forbs. Removal of the vegetation
will affect the snow and soil moisture distribution due to microtopographical
changes created by the removal of larger shrubs. Soil temperature within the
clearing will increase and there would probably be a deeper and earlier thaw
during the summer. The effects of clearcutting on heat balance, soil moisture,
precipitation, runoff, and on wildlife have been described in the coniferous
forest land type (Chapter 4). These effects of clearcutting in tundra environ-
ment would be somewhat different in magnitude but there are no data available
on these effects of clearcutting in a tundra environment.
(1-3) Stumping and Grubbing
Removal of roots and stumps in a tundra environment would cause considerable
disturbances. The practice would create depressions and other microtopographical
6-21
-------
disturbances in the treatment area. As mentioned earlier, the effects of micro-
topographical changes in a tundra environment are quite drastic and would af-
fect snow distribution, heat exchange, depth of thaw, soil moisture, soil
temperature, and surface runoff. Surface litter and the organic layers on the
surface would also be disturbed.
Due to the drastic nature of disturbances such as increased potential
hazards for soil erosion and sediment losses and deeper thawing and freezing
that would be caused by a stumping and grubbing operation, the practice of
vegetation removal by stumping and grubbing should not be used as a contaminant
cleanup technique in the tundra environment.
(1-4) Scraping and Grading
The surface alteration through scraping and grading in the tundra environ-
ment would require some prior clearcutting and removal of stumps from the treat-
ment area. Surface litter and some organic.matter would be removed in the
process of scraping. Grading processes may even expose some mineral soil hori-
zons. The insulative effects of vegetation, surface litter and organic matter
would be destroyed and therefore the heatflow would not be insulated. Soil
thawing and freezing would be relatively faster and deeper.
Infiltration rates would decrease with an increase in surface runoff and
water erosion. The frequent freeze-thaw cycles at the soil surface coupled
with the common presence of permafrost not far beneath the surface results in
physical frost-thrusting of soil, rocks and plants wherever water is abundant.
Surface scraping and grading would enhance such soil frost activity which
produces various kinds of polygons, stone nets, and solifluction terraces.
These disturbances would make the edaphic environment unstable. Such wide-
spread soil frost activity, combined with the frequent presence of permafrost
not far below the soil surface, would have a significant effect on getting the
vegetation reestablished in the treatment area. Vegetational patterns in
arctic and alpine tundra are strongly shaped by such soil frost activity.
Other effects of surface alteration in the tundra environment would be
similar to those described in the coniferous forest land type (see Chapter 4).
6-22
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CJ.-5) Shallow Plowing >
Shallow plowing operations for contaminant cleanup would not be practical
for the tundra land type.
(1-6) Deep Plowing ' .
Deep plowing operations for contaminant cleanup would not be practical for
the tundra land type.
(1-7) Soil Cover Less Than 25 am.
Top soil dressing the treatment area would cover up the surface litter and
organic matter horizons. Ecological impacts of the treatment would vary accord-
ing to the depth of top soil application. The treated areas should be reseeded
or replanted for getting vegetation reestablished.
Beneficial effects of top soil dressing would be in terms of better in-
sulation against heatflow, thus slowing soil thawing and freezing. Infiltration
rates would also increase. However, lack of vegetative cover would make the
soil surface vulnerable to the soil losses due to wind and water erosion.
(1-8) Soil Cover to 25 to 100
Same as for treatment 1-7.
(2-1) Remove Plow Layer
Removal of surface soil (10 cm) from a contamination area in the tundra
environment would be similar to scraping and grading practices. Surface litter
and organic matter layers would be disturbed. Ecological impacts of this opera-
tion would be similar to those described under Scraping and Grading (1-4).
(2-2) Remove Shallow Root Zone
Removal of shallow root zone soil (<40 cm) would also be similar to the
operations for surface alterations. The ecological disturbance and impact are
very similar to those described under Scraping and Grading (1-4).
6-23
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(2-3) Remove Scraping and Grading, Mechanically Stabilize
Surface scraping and removal of a shallow layer (<5 cm) from a contami-
nated area in the tundra environment would be impractical. Tundra soils have
thick layers of litter and organic horizons on the surface. Moreover, the re-
moval of a shallow layer from soil surface would disturb the area and would
result in loss of insulative layer against heat flow. The operation would
cause increased frost action and unstable surface conditions. Exposed surface
would not be suitable for mechanical stabilization.
(2-4) Remove Plow Layer3 Mechanically Stabilize
The technique would not be applicable for the same reasons described above
(2-3).
(2-5) Remove Shallow Root Zone* Mechanically Stabilize
Would not be practical.
(2-6) Remove Scraping and Grading, Chemically Stabilize
Chemical stabilization is not practical in the tundra environment.
(2-7) Rerxove Plena Layer^ Chemically Stabilize
Chemical stabilization would not be practical.
(2-8) Remove Shallow Root Zone, Chemically Stabilize^
Chemical stabilization would not be practical.
(3-1) Barriers to Exolude People
Exclusion of people from the treatment area would not affect the ecology
of tundra.
(3-2) Exclude Large Animals
Exclusion of large herbivores such as reindeer, caribou or musk oxen
would reduce local grazing pressure and result in increased surface biomass,
increased insulation by organic material and a gradual change in permafrost
6-24
-------
depth. Since large herbivores can cause a decrease in lichens and in increase
in woody shrubs, continued exclusion might lead to a shift in relative abundance
of some species, but otherwise would not affect the ecology of the area.
Herding arctic animals follow set migration,paths; however, unless the
exclusion fence blocked a natural barrier such as a mountain pass or river ford,
even the largest fenced area should have little effect on gross animal movement.
(3-3) Exclude Large and Small Animals
Exclusion of the small and large animals from the treatment area would
help the process of natural restoration. There would be no disturbances caused
by browsers and grazers. Large animals like reindeer, caribou and musk oxen,
and small animals like lemmings, have quite a grazing impact on the ecology of
the tundra environment. The other impacts are due to compaction, surface soil
disturbances and physical damage to the vegetation.
(4-1) Asphalt Hard Surface Stabilization
This treatment is outside the scope of work of this study. However, ex-
perience in construction of arctic roadways and air strips suggests that changes
in the insulation properties of the surface and the resultant change in the
depth of permafrost would be the major effect. Lachenbruch has detailed the
procedures for calculating the proper thickness of gravel fill for different
surface materials and climatic conditions that will minimize the effect on the
permafrost layer.
(4-2) Concrete Hard Surface Stabilization
This treatment is outside the scope of work of this study.
(5-0) Application of Sewage Sludge
This treatment is outside the scope of work of this study.
(6-1) High Pressure Washing
This treatment is outside the scope of work of this study.
6-25
-------
(6-2) Flooding to 30 am
This treatment is outside the scope of work of this study.
(7-0) So£l Amendments Added
This treatment is outside the scope of work of this study.
6.5 RECOVERY AFTER CLEANUP
6.5.1 Irreversible Changes
The cleanup techniques described earlier for the tundra environment would
not have irreversible impact on the ecology. However, the harsh nature of the
tundra environment, relatively short growing season and low temperatures during
the growing season would make the vegetative regeneration, ecological succession
and animal recovery very slow processes.
6.5.2 Rates of Recovery
The sensitive nature of the tundra ecology to disturbances has led to the
concept of "fragile" tundra. Figure 6-1 illustrates the series of events which
follow the damage of tundra vegetation. The altered plant cover reduces both
surface insulation and albedo, and more heat is absorbed by the soil with the
result that there is a greater depth of thaw and both subsidence and erosion
may ensue. Such disturbance will ultimately recover due to the natural homeo-
static mechanisms in ecosystems which bring about new equilibrium. Unfortu-
nately little is known about the time factor in these recoveries; it may range
from a few to hundreds of years. In Figure 6-1, well drained sites where the
ground contains little ice show slight changes and recovery to a new, little
altered equilibrium is rapid. However, on wet sites containing much ground ice
greater damage is caused, and recovery will be slow and may result in a different
vegetation when equilibrium is regained.
One of the greatest concerns of ecologists is the degree to which tundra
vegetation can be disturbed and yet reestablish a turf within three to five
A
years prior to therniokarst development. According to Brown et al., even the
replacement of mulch results in nearly as deep a thaw as does the removal of
total plant cover, 61 cm versus 75. cm, respectively. The control plots averaged
6-26
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32 cm for maximum summer thaw. The changed albedo is probably the major factor
even though an insulative layer was returned in the one treatment.
The rates of vegetative recovery and seedling establishment in the tundra
environment are very slow, thus increasing the potential for permafrost melt
and thermokarst development.
6.5.3 Succession Stages Following Cleanup
6.5.3.1 First Year--
During the first growing season after the cleanup the ecological succes-
sion would depend upon the nature of treatment and the degree of disturbances
associated with it. In the natural restoration areas there would be no signi-
ficant disturbances in the surface litter and organic horizons. Some of the
woody shrubs which have quite an extensive and well insulated rooting system
will start sprouting. Grasses, sedges and forbs would also regenerate fairly
well. Lichens and mosses would not show much of regeneration. Cleanup pro-
cedures such as stumping and grubbing, surface alterations, and removal of sur-
face soil layers would cause major surface disturbance and thus the treated
area would be subjected to severe frost action.
6.5.3.2 Fifth Year
In the natural regeneration area, and in the areas which were fenced out
to keep the people or large and small animals out, the surface disturbances
and frost action were minimum. The vegetative recovery for grasses, woody
shrubs and forbs should be quite normal. Again the lichens and mosses would
have a relatively slow recovery. The seeds from the nearby sources, and sprout-
ing of shrubs and grasses, which have an extensive rooting system, would get
the vegetative establishment started. In the areas where surface litter and
organic horizons were removed or disturbed, there would be a considerable in-
crease in the frost action and microtopographic changes. Erosion rates would
be quite high. There would be very poor vegetative recovery and succession.
6.5.3.3 Tenth Year--
Vegetative succession after ten years from cleanup treatment of an area in
the tundra environment would have a near normal vegetative cover recovery
6-28
-------
except for lichens and mosses. This is based on an assumption that there were
no major disturbances to the surface litter and the organic horizons. The
situation would be different in areas where the cleanup operation disturbed the
insulating layers of litter and organic matter and changed the albedo con-
siderably. The vegetative establishment would have a very slow start in the
disturbed areas. However, during the first ten years after the treatment, most
of the frost action induced disturbances and land subsidence would have already
taken place and natural or man induced revegetation would start taking place
on a new surface.
6.5.3.4 Climax--
It would be very difficult to evaluate the post cleanup treatment effects
on vegetative recovery and succession to a climax stage. Differences in eco-
logical conditions after fifty or 100 years after different cleanup treatment
are not expected. In terms of geological time, there would be no differences
due to different cleanup treatments reflected in the climax vegetation.
6.6 QUANTITATIVE ASSESSMENT OF CLEANUP IMPACTS
The proceeding sections of this chapter have clearly shown that any cleanup
procedure (except the benign exclusion by barrier) involves major perturbation
of the tundra biome that will result in long lasting environmental effects.
Quantitative assessment of the ecological differences among the various pro-
cedures is meaningless since any procedure which would result in removing a
hazardous material will result in approximately the same ecosystem desruption.
6.7 CONCLUSIONS
Cleanup techniques result in changes in albedo, in microclimate, in thermo-
equilibrium, and in the relationships between unfrozen ground and permafrost.
To a large extent homeostasis is maintained by the mosses and lichens. During
the short summer growing period when the sun is the warmest, there is an
abundance of standing melt water on the tundra. Moss has a very high evapo-
transpiration rate that tends to keep the air layers closest to the ground
cool. The lichens prevent the direct rays of the sun from striking the ground
surface. The interaction of cool air, cool water and no direct sunlight permits
6-29
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only a minimum melting of the permafrost and leads to the formation of a shal-
low active area where plant growth takes place.
If the cover material of the tundra is disturbed in any way the active
layer becomes thicker while the permafrost table is lowered. The thicker
active layer collects additional water from surrounding areas. This additional
water leads to formation of frost heave structures, thermokarsts and soil move-
*
ment through solifluction.
All cleanup techniques alter the cover material and are therefore delete-
rious to the tundra.
6-30
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6.8 TUNDRA REFERENCES
1. Abale, G./W. H. Parrott, and D. M. Atwood. Effects of SK-5 Air Cushion
Vehicle Operations on Organic Terrain. CRREL Report, 1972. 141 pp.
2. Bliss, L. C. Primary Production within Arctic Tundra Ecosystems. In:
Productivity and Conservation in Northern Circumpolar Lands, 77-84.
IUNC. Pub. 16. Merger, Switzerland, 1970.
3. Bliss, L. C., and R. W. Wein. Plant Community Response to Disturbances in
the Western Canadian Arctic. Can. J. Bot., 50:1097-1109, 1972.
4. Brown, J., W. E. Richard, and E. Victor. The Effect of Disturbance on
Permafrost Terrain. CRREL Special Report 138, 1969. 13 pp.
5. Brown, J., and J. C. F. Tedrow. Soils of the Northern Brooks Range, Alaska,
4: Well-Drained Soils of the Glaciated Valleys. Soil Sci. 97:187-195, 1964.
6. Cody, W. J. Reindeer Range Survey. Plant Res. Inst., Canada Dept. of
Agric., Ottawa, 1964. 17 pp.
7. Dagon, R. R. Tundra - A Definition and Structural Description. Polar
Notes. 6:22-34, 1966.
8. Dunbar, M. J. Stability and Fragibility in Arctic Ecosystems. Arctic,
26:179-185, 1973.
9. Hill, D. E., and J. C. F. Tedrow. Weathering and Soil Formation in the
Arctic Environment. Amer. J. Sci. 259:84-101, 1965.
10. Holowaychuk, N., J. H. Petro, H. R. Finney, R. S. Farnham, and P. L. Gersper.
Soils of Ogotoruk Creek Watershed. In: Environment of the Cape Thompson
Region Alaska (N. J. Wilimovsky, and J. N. Wolfe, eds.), 1966. pp. 221-273.
11. Johnson, P. L. and W. D. Billings. The Alpine Vegetation of the Beartooth
Plateau in Relation to Cryopedogenic Process and Patterns. Ecological.
Monographs, 32:105-135, 1962.
12. Klein, D. R. The Impact of Oil Development in Alaska. In: Productivity and
Conservation in Northern Circumpolar Lands, 209-242. IUCN. Pub. 16. Merges,
Switzerland, 1970.
13. McCown, B. H. and J. Brown. Ecological Effects of Oil Spills and Seepages in
Cold-Dominated Environments, In: 1971 Tundra Biome Symposium Proceedings,
61-65, 1971.
6-31
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14. McKay, G. A., B. F. Findlay, and H. A. Thompson. A Climatic Perspective of
Tundra Areas. In: Productivity and Conservation in Northern Circumpolar Lands,
10-33. IUCN Pub. 16. Morges, Switzerland, 1970.
15. Osburn, W. S. Jr. Radioecology. In: Arctic and Alpine Environments (J. D.
Ives and R. G. Barry, Eds.), 875-903. Methuen, London, 1974.
16. Richard, W. E. Ecological Evaluation of Air Cushion Vehicle Tests on Arctic
Terrain. CRREL Tech. Report, 1971. 30 pp.
17. Rickert, D. A. and J. C. F. Tedrow. Pedological Investigations on Some
Aeolian Deposits of Northern Alaska. Soil Sci. 104:250-262, 1967.
18. Rieger, S. Dark Well-Drained Soils of Tundra Regions in Western Alaska.
J. Soil Sci. 17:264-273, 1966.
19. Sigafoos, R. S. Frost Action as a Primary Physical Factor in Tundra Plant
Communities. Ecology. 33:480-487, 1952.
20. Vuilleumir, F. Insular Biogeography in Continental Regions. The Northern
Andes of South America. Amer. Nat. 104:373-388, 1970.
21. Walker, J. The Influence of Man on Vegetation at Churchill. In: Pro-
ductivity and Conservation in Northern Circumpolar Lands, 266-269. IUCN.
Pub. 16. Morges, Switzerland, 1970.
22. Watson, A., N. Bayfield, and S. M. Moyes. Research on Human Pressures in
Scottish Mountain Tundra, Soils, and Animals. In: Productivity and Con-
servation in Northern Circumpolar Lands, 256-265. IUCN. Pub. 16. Morges,
Switzerland, 1970.
23. Webber, P. J. Tundra Primary Productivity. In: Arctic and Alpine Environ-
ments [j. E. Ives and R. G. Barry, eds.), 445-473, Methuen, London, 1974.
24. Whittaker, R. H. Communities and Ecosystems. Macmillan Publishing Company,
New York, 1975. 385 pp.
6-32
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CHAPTER 7
COASTAL INTER-TIDAL MARSHES
.7.1 OVERVIEW
Heavy vegetational development takes place where the soil is waterlogged
or covered by shallow standing water for all or most of the year. Wher.e this
vegetation is dominated by grasses, reeds, sedges, and other non-woody types
the development is referred to as a marsh. If the vegetation is largely
bushes and trees, it is called a swamp. Coastal marshes and swamps represent
some of the highest zones of primary productivity in the world. Some marshes
exhibit a net primary productivity of greater than 3,000 g/m2/yr (Table 7-1).
In coastal marshes, however, less than 10 percent of the net production of the
ecosystem is consumed by grazing herbivores, mostly insects in this case, and
at least 90 percent follows the detritus path of energy flow. The bulk of
the aninals in the coastal marsh such as shellfish, snails, and small crabs,
seem to obtain their energy directly or indirectly from detritus.
The five mechanisms and conditions that maintain this biological energy
flow at rates far superior to the adjacent ecosystems are: (1) Tidal action
promotes a rapid circulation of nutrients and food, and aids in the rapid re-
moval of the waste products of metabolism. (2) A diversity of plant species
and life forms provides a continuous photosynthetic carpet despite variable
physical conditions. The three major life forms of autotrophs that work to-
gether to maintain a high gross production rate are: (a) phytoplankton; (b)
benthic microfloraalgae living in and on mud, sand, rocks, or other hard
surfaces, and bodies or shells of animals; (c) large attached plantsthe sea-
weeds, submerged eel grasses, and emergent marsh grasses. (3) A coastal marsh
is often an efficient-nutrient trap that is partly physical (differences in
salinities cause vertical as well as horizontal stratification of water masses)
and partly biological. (4) A year-round primary production by a succession of
"crops," even ,in northern regions. (5) Close contact between autotrophic and
heterotrophic layers.
7-1
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Coastal marshes develop on relatively flat terrain between the limits of
normal high and low tide of protected bays, estuaries, and lagoons. They are
dominated by a few species of tall emergent reed-like vegetation which are
tolerant of rhythmic submergence and saline conditions. The water may be nearly
fresh or nearly marine or highly variable in salinity, and flushing occurs with
each tidal cycle. Within saltwater marshes there is a gradual build-up of organic
peat deposited by the vegetation itself. Highly dendritic tidal creeks dissect
the marshes and serve as avenues of entrance and egress of the tidal waters
which alternately flood and drain the marshes. Because of their adaptations to
the intertidal zone, salt marshes are highly sensitive to even minor change
in water levels.
The coastal marsh ecosystem lies from a few feet above sea level to a
few feet below it. Hence, it is subject to the ebb and flow sweeping action of
tidal currents, and all must be tolerant of some salinity change. All trap
suspended nutrients by slowing down the water currents, and they all provide
shelter and food for a variety of small brackish water and marine animals. These
are among the most productive ecosystems of the world with annual production
rates running around five tons per acre. Much of this plant production becomes
available as organic detritus which provides the chief food base for the coastal
fish and shellfish populations of commercial importance. Without these important
production and nursery areas, our coastal seafood resources would suffer severe
decline.
Although tolerant of short-term inundations with fresher or more saline
waters and even short-term exposure to the air, these systems cannot tolerate
long-term changes in these environmental factors. Drying of the habitat or
major intrusion of fresh- or saltwater has been shown to change the composi-
tion of the dominant vegetation with long-term erosion of the productivity of
these systems.
The marsh vegetation is dominated by several species of the tall Spartina
grass and to lesser extents by other emergent species such as Distichlis, Juncus,
and Salicornia. Around the bases of these plants and on the surfaces of old
leaves grow a variety of filamentous algae including blue-green, brown, and red
algal types. On the mud flats between the bases of the plants grow a variety of
7-3
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diatoms and blue-green algae. Plant production of the marsh is dependent upon
all three groups of producers, the tall emergent species, the filamentous attached
forms, and the mud flat inhabitants.
Only grasshoppers and a few birds such as seaside sparrows may be found among
the tall Spartina grass, but the water and mud flats are teeming with animal
life. This includes snails, mussels, and oysters, as well as a variety of worms,
crabs, shrimp, and small fishes. Many of the crabs, shrimp, and fishes are juve-
niles of species which support the commercial catch as adults. Large numbers
of shore and wading birds forage in these marshes at low tide.
Studies have shown that there is a regular export of decomposing organic
matter through the tidal creeks to the estuaries, but the major export occurs
when storms inundate the marshes with high water and flush out great quantities
of organic matter to the estuaries and the continental shelves.
7.1.1 Occurrence of Coastal Marshes
Coastal marshes (or intertidal emergent wetlands) are recognized as an eco-
logical class within the Estuarine System of a wetland classification (Figure
7-1). There are nearly 70 million acres of natural wetlands in the continental
United States of which coastal marshes total about 17.5 million acres.
7.1.2 Related Land Tyj)es_
Coastal marshes as an ecosystem type are very similar to coastal swamps
and grass flats. All are emergent wetland ecosystems (Figure 7-1).
A coastal swamp is an association of mangrove trees which grows in the sea
or in the water of sheltered bays and estuaries of subtropical regions. The
average water depth may be from a few inches to about four feet. Extensive prop
root systems reduce the action of waves and tidal currents and produce a charac-
teristic set of internal environmental conditions. Water flow is greatly reduced.
Sedimentation is high, and much organic matter accumulates. Oxygen levels are
low, and the environment is in many respects similar to that of anaerobic sub-
merged soils. Strong gradients in oxygen content and other factors exist from
the periphery to the interior of the swamp. In some cases, saltwater swamps
grade inland into saltwater marshes.
7-5
-------
Coastal swamps are dominated by the low, bush-like red. black, and white
mangrove trees. A few other shrubs and vines may also be present. The exten-
sive root systems developed by the mangroves provide surfaces for attachment of
filamentous algae, and the surface muds may support large and productive diatom
floras. Large numbers of oysters are often found attached to the mangrove roots;
a variety of small crabs, shrimp, and fishes feed on the organic forage around
the roots and mud flats at low tide; and birds nest in the branches of the man-
groves.
Grass flats or submarine meadows consist of a few species of grasses which
are tolerant of continual submergence in salt and brackish waters. They are
normally found from the low water line to a depth of about three feet, but they
may extend considerably deeper in very clear waters. Although seldom found in
very strong current, they are most luxuriant where there is moderate flushing.
The long flat blades of the dense beds protect the bottom from erosion, and
extensive deposition creates a substratum of finely particulate, high organic
muds. Sufficient water penetrates the beds to-maintain high oxygen levels in
the water above the bottom.
The grass flats are dominated by eelgrass (Zostera spp) in northern lati-
tudes or by turtle grass (Thalassia spp) or manatee grass (Cymodocea spp) in
the more tropical areas. The long grass blades are often clothed with a layer
of attached filamentous algae which produce organic matter and which also act
as brushes to remove suspended matter from the flowing water above. Many small
animals live among the stems and roots of the grass beds, and larger fishes and
birds forage there.
7.2 NATURAL PERTURBATIONS
Coastal marshes are generally considered to represent a serai stage in the
succession of water to dry land. In areas with relatively stable climatic
conditions, succession is extremely slow and the marsh maintains the same appearance
year after year. In other areas, violent climatic fluctuations cause coastal
marshes to revert to an open water phase in some years and the concept of succes-
sion in the normal sense of the word has little meaning. Fire has been shown to
play an important role in maintaining coastal marshes. Coastal marshes can
recover from fires in a couple of years if the fire does not burn down to the
bare soil and thereby permit excessive erosion.
7-6
-------
Large storm systems (e.g., hurricanes) can cause extensive damage to coas-
;tal wetlands due to erosion and excessive freshwater runoff. Erosion physically
disrupts the marsh while the freshwater inflow may temporarily upset biota
adapted to marine or estuarine conditions. These effects are generally short
term and marsh recovery would be expected within a few years. Studies of natu-
ral perturbation show effects on primary and 'secondary productivity but these
perturbations are well within the range of homeostatis within the marsh ecosystem.
7.3 MAN-MADE PERTURBATIONS
7.3.1 Impact on Baseline Ecosystem Components
The coastal marsh is a semi-aquatic system in equilibrium with the prevail-
ing climatic, hydrographic, geological, and biological forces of the coast.
Even slight modification in the level of the water table or the rate of surface
freshwater flow greatly modifies the biological characteristics of the system.
Although the coastal marshes vary greatly in detail, a more or less typical
marsh has freshwater vegetation at the landward side, saltwater vegetation at
the marsh is drained by highly dendritic tidal creeks which empty into the bay
or estuary. Freshwater entering along the upper edges of the marsh drain across
the surface and enter the tidal creeks.
Many of the marshes of the Atlantic and Gulf coasts have undergone great
attrition in recent years, primarily as a result of levee and canal construction.
A levee placed across the upper end of a coastal marsh has the following primary
effects:
cuts off all distributaries feeding the marsh
prevents freshwater flooding
prevents annual flushing
prevents annual renewal of sediments and nutrients
ends foi-mation of new marshes.
Canals which lace the coastal marshes for navigation, pipelines, or mosquito
control have the following primary effects:
intercept and carry off freshwater drainage
block freshwater from flowing across the portion of the marsh that
is seaward of the first canal
rapidly carry off freshwater to the bay or estuary
7-7
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lower the water table
permit saltwater intrusion well into the marsh proper.
7.3.2 Unassisted Recovery Sequence
The biological consequences are clear. On the Atlantic coast where sub-
sidence rates are fairly slow, the marsh vegetation gives way to dry land vege-
tation with accompanying changes in the animal populations. Bourn and Cottam
reported on a detailed 10-year study of the fate of a drained coastal marsh in
Delaware. Prior to canalization, 90 percent of the marsh vegetation was salt-
marsh cordgrass (Spartina alterniflora) with smaller amounts of other marsh
species, especially at higher elevations. A few open water areas supported
luxuriant growths of widgeongrass (Ruppia maritima) and other submerged aquatic
species.
Ten years after ditching had taken place the wetland plants had been reduced
to small groups in the remaining low spots and along canal margins. Groundsel-
bush (Baccharis halimifolia) dominated the plant community which now was made up
largely of dry land species such as asters, goldenrods, terrestrial grasses, and
young trees (pine, juniper, sweetgum, maple, and hawthorn). Aquatic animal
populations of the ditched areas had been greatly reduced in areal extent and in
density, even in the wetland habitat which still remained (Table 7-2). The
density of the total invertebrate population was reduced from 39 to 97 percent
in the various samples, and the mollusks and crustaceans, which make up important
food items for many fishes and shore birds, were reduced 32 to 100 percent. Open
aquatic areas, which formerly supported widgeongrass and other important duck foods,
had been reduced to mud flats and dry land. Thus, the wetland habitat, important
in the production of fishes, shellfishes, ducks, and wading birds, had given way
to land with its low wildlife values.
On a subsiding coast, such as occurs in southern Louisiana, elimination of
the normal freshwater and sediment input upsets the land-water equilibrium, and.
the subsiding marsh tends to become an open water area. This tendency is intensi-
fied by canals which drain the marshes, enhancing compaction. These canals tend
to grow wider as a result of marginal subsidence, wave erosion, and disturbance
from boat traffic. Plant production by marsh grasses of the Gulf coast is very
high, exceeding 10 tons per acre per year and a great deal of additional plant
production occurs in the marshes due to attached algae, mud flat diatoms, and
7-8
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Table 7-2. Effects of ditching a Delaware tidewater marsh on the aquatic
invertebrate populations. Vegetational zones are characterized
by the dominant plant species. Six-foot square quadrants were
sampled for comparison of invertebrate density in the drained
and undrained sections of the marsh, and they represent three
consecutive years of sampling during the months of April-December
(from U.S. Environmental Protection Agency^)-
Vegetation Zones
Feet above mean
sea level (for the
undisturbed marsh)
Percent reduction of the
invertebrate populations
Total
invertebrates
Mollusks and
crustaceans
Saltmarsh cordgrass
(Spartina alterniflora)
Saltgrass
(Distich! is spicata)
Saltmeadow cordgrass
(Spartina patens)
Saltmarsh bulrush
(Scirpus robestus)
1.88-2.93
2.35-2.90
2.58-3.32
2.75
39-82
64-88
41-97
50-97
32-95
82-94
55-100
58-98
phytoplankton in the shallow waters. A large fraction of this organic matter
is exported through tidal creeks to nearby bays and estuaries. When the marsh
becomes an open water area, however, production is apparently reduced, and
instead of exporting organic matter, the area becomes a nutrient sink. Birds
and mammals no longer find food and refuge among the marsh grasses, and canals
create migrational barriers to terrestrial and semi-terrestrial animals which
utilize the marsh. Complete shifts in vegetation accompany increased salinity
and subsidence.
Saltwater intrusion increases the salinity of the marshes, eliminating
the broad mixing zone so important as nursery grounds for juvenile fishes,
shrimp, and crabs. In deeper channels where reducing conditions prevail,
large quantities of hydrogen sulfide are produced which are toxic to the marsh
o
grasses and to the aquatic animals. Acid conditions of the canals may also
result in release of heavy metals from the sediments. As a result of habitat
loss, decreased food supply, increased salinity, and increased hydrogen sulfide,
7-9
-------
populations of aquatic animals are adversely affected. Moore and Trent compared
oyster production in natural and canalized marshes. They found that in the
altered marsh the set of young oysters was reduced by over 90 percent, juvenile
growth was slowed, average length was reduced by 36 percent, weight was reduced
by 27 percent, and mortality was increased by 39 percent. As a result of these
and other studies, St. Amant (unpublished) has concluded that lack of freshwater
has drastically modified the ecology of coastal marshes and severely damaged
production of valuable oysters, shrimp, fur animals, and waterfowl.
In areas of eroding shorelines where dredged spoil has been used to sup-
port vegetation, both seeding and transplanting methods have been used to re-
develop the flora. Both methods have been highly successful and after two grow-
ing seasons, little or no difference existed in appearance and primary produc-
tivity between these new marshes and long established natural marshes.
The methods of soil removal are dependent on the depth and characteristics
of the unstable material as well as upon the nature of the underlying stable
substrate (Figure 7-2). Where depths of unstable material do not exceed about 10
feet a dragline, shovel, or dredge may be used to excavate the unstable material
to sufficient width. The excavated material handled by dragline or shovel is
usually side cast beyond the excavation, forming a spoil bank, and it must be
removed a sufficient distance to prevent lateral displacement back into the
excavation.
Where deeper unstable deposits are encountered (about 10 to 25 feet), dis-
placement methods are commonly used. In such methods the fill is advanced by
end-dumping and placement with a bulldozer in a V-shape (i.e., highest along the
central crest). Fill height is increased until the load is sufficient to produce
failure in the underlying unstable materials, displacing them laterally. Dis-
placement may be accelerated by jetting with water prior to, during, and after
displacement of the fill. As the fill settles, additional material must be
placed to maintain the grade. The weight of the fill will cause lateral compres-
sion in the displaced materials which may result in settling and horizontal
movement of the shoulders for several years.
Displacement of unstable materials under the fill may also be accomplished
by blasting. In the "underfill" technique the surface layers are broken with
equipment or light charges, the fill is placed, and explosives are then positioned
through the fill in jet holes or casings. Usually one to three rows of explosives
7-10
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are placed along the center line about midway between the fill bottom and the top
of the underlying solid substratum. In addition, at each edge of the fill two
or three rows of charges are placed 4 to 5 feet below the surface. The explo-
sion displaces the soft materials, creating a cavity under the fill which then
settles rapidly. In the "toe-shooting" technique the soft material is displaced
by blasting ahead of the advancing fill. Added fill material is pushed into the
cavity left by the blast, and the fill is advanced with a V-poir.t which displaces
the soft material and', develops a wave in front of the fill. In the process, the
front face of the fill is overburdened, and the explosive charges are placed
around the toes of the fill near the bottom of the soft material.
The cutting and digging action of the dredging operation breaks through
the thin oxidized layer of the submerged soil and exposes the deeper unoxidized
layer. Furthermore, most of the sediments placed in suspension are removed from
this layer and, hence, are in the chemically reduced state. Such materials have
very high chemical and biological oxygen demands. Frankenberg and Westerfield
calculated that some dredge spoils require 535 times their own volume of oxygen
for complete oxidation, and Brown and Clark reported oxygen levels near dredges
18-83 percent below normal. Both the sedimentary particles and the interstitial
waters released contain immediately toxic materials such as hydrogen sulfide,
methane, and a variety of organic acids, ketones, aldehydes, etc., as well as
heavy metals and pesticides which exhibit persistent toxic effects. Turbidity,
per se, reduces light penetration and interferes with photosynthetic production
of oxygen, and it tends to elevate water temperatures. Eventually the suspended
material settles to the bottom either near the dredging site or far downstream.
Thus, there is a redistribution of sediments together with whatever nutrients
and chemical pollutants which they may contain, and this may result in modified
bottom topography and altered patterns of water circulation. Such sedimentation
problems are greatly accentuated when dredge spoil is placed back into the water.
General and immediate effects of dredging and spoil placement are listed in
Table 7-3.
In coastal marshes the matter is complex because of the adjacency of salt-
water and the natural process of coastal subsidence. Coastal marshes, in the
undisturbed state, represent vast drainage systems. Freshwater enters on one
side, generally from the floodwaters of annual river overflow, and it gradually
works down to the coast in a broad, flat surface sheet. Occasional creeks and
bayous aid in the runoff. Near the estuaries the marshes are dissected by
7-12
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dendritic tidal creeks. Thus, through the marsh there is naturally a gradual
salinity gradient from freshwater to the more brackish waters of the estuary.
Marshes overlie deep layers of unconsolidated river deposits which gradually
undergo compaction as the water is squeezed out. Such marshes would gradually
subside, but sediment input through river overflow and buildup of organic matter
through plant growth counteracts this tendency and maintains the delicate land-
sea, and freshwater-saltwater balances.
Soil removal (including denuding) from marshes accelerates the rate of
freshwater runoff, and it may lower the water table of the soil, drying out the
higher areas of the marsh. Artificially denuded areas do not correspond to nat-
ural coastal meandering tidal streams. They may, however, erode to form open
canals. Once opened, such canals tend to widen due to tidal and other natural
action or due to the effects of boat traffic. Land loss from canal erosion has
reached serious proportions in Louisiana and elsewhere.
In addition to draining away the freshwater, the canals offer paths for
saltwater penetration of the marshlands, and this is especially prominent in
the deeper canals. Since rivers no longer are permitted to flood the upper
reaches of the marshes, they are now deprived of both the annual freshwater
and the annual sediment load. Thus, as compaction and subsidence proceed, and
as saltwater penetrates through the canals, the effect of saltwater is being
felt further and further inland. Vehicular traffic over the marshlands (mud-
boats, marsh buggies, and heavy equipment) associated with restoration activities
accentuates this problem.
Marsh canals have very high contents of organic matter and high oxygen
demands. Yet water circulation is often poor, and this leads to reducing or
near reducing conditions, especially in the bottom water. Saltwater is rich in
sulfates, and when the sulfates enter the reducing conditions, they are con-
verted to sulfides, which are very potent biotoxins. Precipitated iron sulfide
is a common marsh deposit.
Spoil banks are often cast up alongside the canals creating a surface dam
effect. Such banks impound waters on both sides and seriously interfere with
normal surface drainage patterns. The spoil banks directly cover vast acreages
of marshland, and erosion from the spoil banks tends to drain back into the
canal, on one side, and into the marshland, on the other. Since the sediment
7-14
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itself is mostly in the chemically reduced state, it tends to lower the oxygen
concentration of the canal waters when it flows back. Erosion of spoil banks
and shallowing of canals require redredging in a never-ending cycle. Effects
of soil removal and spoil placement in marshlands are listed in Table 7-4.
Table 7-4. Effects of soil removal and placement of dredge
spoil in marshlands (modified from U.S. Environ-
mental Protection Agencyll).
Interference with surface drainage patterns
Acceleration of surface drainage by canals
Damming of surface drainage by spoil banks
General acceleration of freshwater runoff
Loss of marshland habitat
Loss due to canalization
Loss due to water table lowering
Loss due to erosion and widening of canals
Loss due to spoil coverage
Loss due to acceleration of marsh subsidence
Acceleration of saltwater penetration
Conversion of sulfates (of saltwater) to sulfides in the
canals and precipitation of iron sulfide in the
canals
Erosion of spoil banks and distribution of chemically
reduced sediment into canals and open marsh
7.4 EFFECTS OF CLEAN-UP PROCEDURES
ON COASTAL MARSHES
Clean-up procedures considered for marsh land types include temporary con-
tainment, contaminant removal and barrier exclusion. The following subsections
discuss the effects of these treatments on the marsh ecosystem.
The first techniques considered are those which may be applicable for pre-
venting further spread of contaminants across the marsh until contaminant removal
7-15
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by clean-up can be accomplished. The various alternative methods are considered
to be appropriate for coastal marshes if they might pre/ent further redistri-
bution. The techniques discussed in this subsection include chemical stabili-
zation, clear cutting, stumping and grubbing, plowing, and application of un-
contaminated soil cover.
(1-1) Chemical Stabilization
Chemical stabilizers are materials employed to bind soil particles together
as an aid to preventing erosion. Chemicals may also be applied to mulch mater-
ials to act as a binding agent.
The effect of chemical stabilizers is usually temporary and in the water-
logged soils of the marsh environment may be very transitory. Because of this
characteristic, chemical stabilization may not be an appropriate treatment for
large areas. However, for small plots, this approach may be of some use. Since
chemical application is commonly a part of revegetation programs, little eco-
logical impact would be expected from application in marsh areas.
Certain chemical stabilizers are designed to reduce the rate of infiltration
In a coastal marsh environment, with the frequent flooding associated with high
tides, infiltration reduction has little meaning. Use of this treatment is
therefore inappropriate for this land type.
(1-2) Clear Cutting Vegetation
Clear cutting would be an appropriate treatment for relatively upland por-
tions of coastal marshes which support significant populations of trees and
to large emergent stands such as found in mangrove swamps. Since root systems
would not be removed, erosion potential will clearly be appreciably diminished
relative to root layer removal techniques discussed in subsequent sections.
Root and/or stump sprouting is likely to occur and recovery would thus be ac-
celerated relative to total clearing treatments.
(1-3) Stumping and Grubbing
Stumping and grubbing involves the removal of all surface vegetation and
major root systems. Disposal of vegetation may be by natural decomposition or
by burning, depending on the volume of organic material and the properties of
the contaminant.
7-16
-------
The clearing of the land removes the vegetative cover and permits the rain-
fall to strike the bare land surface. These processes lead to increased surface
runoff and severe erosion. The effects will be accentuated in rainy weather.
In dry weather considerable quantities of soil in relatively upland areas may be
raised as dust clods which will be transported at a later date when the rains
fall. Runoff and erosion will add a great deal of soil solids to the marsh re-
sulting in greater water turbidity and increased sedimentation in tidal creeks.
Denuded areas have been shown to lose large quantities of dissolved min-
erals, particularly sodium, potassium, calcium, magnesium, nitrates, and phos-
phates. In some cases increased groundwater and springflow has been noted
immediately following removal of phreatophytes (which normally pump water up
through the roots to be lost via transpiration), but the springflow may even-
tually diminish as the water table is lowered through lack of recharge.
If the brush cleared from the land is burned in the flood plain the ashes,
which are highly alkaline, may enter tidal creeks and cause an immediate in-
crease in the pH of the water (in one study the pH jumped almost immediately
from 7.8 to 11.3 and remained high for some time). In addition, heat from
the fire can elevate the marsh water temperature quickly and keep it high for
some hours.
Denuding equipment in operation as well as spills in maintenance yards can
result in the passage of petroleum products into the water courses.
The net result may be summarized in the following points:
loss of habitat from devegetation of the area
loss of land fertility from surface erosion and subsurface flow
increased erosion from denuding site activities
lowered groundwater level from devegetation
greatly increased fluctuation in water level due to faster runoff
following rains and decreased flow during dry periods because of
loss of groundwater
greatly increased marsh sediment load due to erosion and
runoff
greatly increased marsh turbidity due to erosion and runoff
7-17
-------
modified chemical composition of the water due to increased
sedimentation and runoff, turbidity, leaching of soil
nutrients.
As a result of these influences, the coastal marsh will undergo a number
of changes. The violent fluctuation in water level will result in greater
freshwater flow rate during wet weather. The creek beds may be cut deeper,
the banks will be undercut, and the open water sections will be widened. Rif-
fles may disappear and pool areas fill. Marsh areas may be swept clear by
flood waters.
Increased sediment loads clog the interstices of riffles, fill the pools,
and cover the bottom generally with a layer of inorganic silt. Bottom habitat
diversity would be significantly diminished. Accompanying the increased run-
off, there would be an increase in water turbidity. This lowers the light
penetration of the water, increases oxygen demand, and modifies the chemical
characteristics of the water in other ways. Loss of vegetative cover and in-
crease in turbidity both serve to elevate the temperature of the water (as
much as 10°F).5
During dry weather freshwater flow may slack off or it may cease entirely,
since the marsh now receives less groundwater inflow than before. As pointed
out by Bayly and Williams, land clearing may so alter the local hydrological
regime that formerly perennial streams may approach or become intermittent.
Since open water pools tend to be reduced or lost, the aquatic habitat may be-
come severely restricted or dried up between floods. Any water that remains is
now subjected to more rapid and estreme temperature fluctuation in response to
prevailing atmospheric conditions.
The long-term results will depend greatly upon local circumstances but,
in general, they would include the following:
permanent loss of natural land habitat If the topsoil is
eroded away, a native ecosystem will not return for many years
increased surface runoff and reduced groundwater flow The
denuded surfaces will continue to yield rapid and complete runoff
persistent chemical changes The high level of sedimentation
and turbidity may eventually taper off.
7-18
-------
Recovery after stumping and grubbing would be dependent upon several fac-
tors including
size of area denuded (the magnitude of the effects outlined
above would be increased with increasing area)
location of disturbed area relative to open water (areas
adjacent to open water would be subject to runoff effects
as well as the erosional influence of tidal currents and
wave action)
weather following cleanup (heavy rains would magnify runoff
impacts and extended dry periods would delay recovery by
possibly drying exposed muds).
(1-4) Scrap-ing and Grading
Surface alteration such as scraping and grading of a marsh area would
have environmental consequences similar to those discussed above for vegeta-
tion removal. However, more complete removal of the surface layer organic
matter would result with this type of treatment. In addition, epibenthic
and burrowing animals would be more directly affected by surface alteration.
Because of the relatively flat characteristics of marsh lands, grading
for containment would not entail leveling as may be the case in more upland
ecosystems. Grading in coastal marshlands would probably include banking
of materials so that drainage patterns would be from the edges of the af-
fected area inward (the reverse of the normal drainage pattern). This could
alter the fresh - salt water gradients within the marsh and ultimately modify
the biological character of the marsh. However, the slight gradients in-
volved here would undoubtedly be overcome by tidal and wave action and flood
events and eventually more-or-less normal gradients would prevail and con-
tainment would be temporary.
(1-5) Shallow Plowing
Plowing is not felt to be an appropriate treatment for a coastal marsh.
Bottom sediments in marshes are continually in a state of flux in response
to tides, waves and runoff events. Plowing would be not only destructive to
the marsh habitat but would also probably enhance contaminant mobility by dis-
rupting the hydrologic regime and creating new flow routes.
7-19
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(1-6) Deep Plowing
See treatment 1-5; this technique is not appropriate for this land type.
(1-7) Soil Cover Less than 25 cm
Because of the scouring action of tides, waves and flood events, thin soil
cover may be only a very temporary containment treatment for this land type.
Thus its use in marsh systems may be limited.
The effects o£"this treatment are in two areasthe area covered and the
source of the cover material. Naturally the magnitude of effects, and hence
the restrictions to recovery are a direct function of the area treated.
In the covered area, the habitat of epibenthic, burrowing and semi-
terrestrial animals would be destroyed. Also young stands of marsh grasses
would be buried and would not be expected to survive. Larger grasses, bushes
and trees would not be buried; however machinery used to dump the cover soil
may be very destructive.
Recovery would be more rapid than if the covering process was preceded
by vegetation removal, as root or stem sprouting may not be prevented with the
shallow cover. Vegetation recovery would be fairly rapid with this treatment
due to the shallowness of the cover which would not bury larger plants and
which would probably soon erode.
(1-8) Soil Cover 25 to 100 am
If the uncontaminated soil fill is up to 100 cm in depth, then the marsh
has simply been filled in and it no longer can be referred to as a coastal marsh.
The addition of 100 cm of soil may cause the land level to excbed the tidal
ranges and, consequently, the saltwater intrusion which is characteristic of a
coastal marsh will cease to occur. The marsh may: (1) cease to have a hydric
soil and begin to behave as a predominantly non-hydric type; (2) change from a
vegetation cover of hydrophytes to predominantly mesophytes or xerophytes;
(3) change from land that is flooded at some time of the year to land that is
infrequently or never flooded during years of normal precipitation.
Treatments considered next are those which remove contaminated soil
layers. Mechanical and chemical stabilization after soil removal is also
discussed.
7-20
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(2-1) Remove Plow Layer1 ,.
The plow layer is defined here as the soil layer from the surface to a
depth of about 10 centimeters. Removal would be accomplished by hand shovel-
ling or larger digging machinery. The unstable marsh soils would necessitate
working from platforms, barges or other support structures.
The ecological effects of soil removal in the marsh would be similar to
those discussed for surface alteration (scraping and grading) and vegetation
removal. Some inference can also be drawn from the earlier discussion of
dredging effects (Section III). Major influences include
acceleration of surface runoff
alteration of drainage patterns
loss of habitat for wildlife
increased erosion
loss of organic matter and nutrients in surface
soil layers.
Recovery would be similar to that for scraping and grading but would be
slower because more of the soil-organic layer is removed and elevations are
somewhat altered thus changing the tidal flooding depth.
(2-2) Remove Shallow Root Zone
In a coastal marsh, the root zone is relatively shallow and theiefore,
the effect of soil removal to the depth of a plow layer and/or to the shallow
root zone can be treated the same. See treatment 2-1.
(2-3) Remove by Scraping and Grading,
Meohanioally Stabilize
The effects of scraping and grading are discussed in treatment 1-4.
This treatment, combined with "mechanical stabilization" includes removal of
contaminated soils (less than 5 ^m in this case) and compaction of subsurface
soils or surfacing with impervious materials to seal the subsurface against in-
filtration. As previously noted (treatment 1-1) infiltration control in a marsh
area which is at' least periodically flooded has little meaning. Hence this
combined treatment method is inappropriate since mechanical stabilization is
inappropriate.
7-21
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(2-4) Remove Plow Layer., Meohaniaally Stabilize
This combined treatment is inappropriate for the marshland type; see treat-
ment 2-3 and 2-1 for further discussion.
(2-5) Remove Shallow Root Zone, Mechanically Stabilize
This combined treatment is inappropriate for the marshland type; see treat-
ments 2-3 and 2-2 for further discussion.
(2-6) Remove by Scraping and Grading,
Chemically Stabilize
The effects of this combined treatment are essentially those discussed in
treatments 2-3 and 1-1. The chemical stabilization method employed would
have to be instituted for erosion control rather than infiltration control for
the reasons previously given. The erosion control provided would be expected
to be transient but might be sufficient to somewhat mitigate runoff impacts
resulting in a more rapid recovery than scraping and grading alone.
(2-7) Remove Plow Layer, Chemically Stabilize
This combined treatment would result in effects similar to those discussed
for plow layer removal alone (treatment 2-1). However, as discussed above,
erosional problems would be mitigated temporarily and recovery would be some-
what more rapid than that without stabilization.
(2-8) Remove Shallow Root Zone, Chemiaally Stabilize
The effects of this treatment are discussed in treatments 2-2 and 2-7.
Barriers to exclude people and to exclude both large and small animals are
discussed in the following treatments.
(3-1) Barriers to Exclude People
It is assumed that exclusion would be accompanied through the use of
barbed wire fencing or some sort of mesh material such as chain link or Cy-
clone fencing, hardware cloth, or poultry wire.
If a natural state is deemed beneficial, then nothing but benefit can
derive from the exclusion of humans. Benefits due to increased "naturalism"
will accrue in direct proportion to the intensity of previous human use or
intrusion. Numbers of species and their diversity will certainly increase as
shy species return to the marsh; this may be especially true in the case of
7-22
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migratory game fowl if hunting is terminated. Vegetative cover, arid hence
primary and secondary productivity, will increase if these parameters had been
below maximum levels due to human trampling. However, note that secondary
productivity is not likely to increase greatly due to the lack of macrophyte-
consuming herbivores which frequent salt marshes. Finally, erodibility would
likely remain unchanged or perhaps even decrease; indeed, a negative erodibility
may exist for marshes since they are areas of deposition.
Humans often find cause for interfering in coastal marshes, especially
when they live near such areas. Natural marshes are .doomed to self-destruc-
tion due to sedimentation and consequent evolution (succession) into an.up-
land habitat. Part of this evolution is often the buildup of a bar at the "
tidal inlet(s), hence, the tidal flushing of the marsh is greatly reduced or
eliminated. As this happens, conditions may become anaerobic as water temper^
ature and salinity rises and, therefore, marsh flora and fauna die and decay.
Such conditions create a great nuisance near points of human activity, and
they provide a haven for insects such as gnats and mosquitoes, further ag'gra-
vating the condition of local human populations. For exactly these reasons,
and also to maintain a maximum level of productivity, marsh channels are often
dredged regularly, especially at the tidal inlet(s).4 Such dredging also en-
hances the flood control value of marshlands by providing open channels for
runoff during precipitation events. Thus, exclusion of human activity may not
be taken to include channel dredging, especially if there is significant human
activity in the vicinity of the contaminated area. It should be noted that, if
periodic dredging is performed, the dredged materials must be checked for con-
taminant level and, if found to contain unacceptable levels of contamination,
must be dealt with accordingly.
(3-2) Barriers to Exelude Large Animals
Not applicable to this land type.
(3-3) Barriers to Exclude Large and Small Animals
It is assumed that exclusion would be accomplished through the use of
fine-meshed materials, such as screen with mesh diameter less than 1.0 cm, or "
through the use of solid materials, for example, brick and cinder block.
7-23
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Animals such as mice, voles, raccoons, rabbits, possums, skunks, weasels,
4
and coyotes could be excluded by this treatment. Mammals rarely live within
a coastal marsh; generally they reside in nearby upland habitat and use the
marsh only for forage, consuming seeds, some plants, insects, and other small
aniirals. Further, such mammals are noted to be "represented by relatively
small populations." Hence, exclusion of these creatures would have very little
effect on the marsh ecosystem; a slight drop in species diversity and in the
total number of species occurring in the marsh would be the only noteworthy
effects.
However, if a large area, e.g. 1 to 10 km2, were fenced off, the result-
ing pressure on surrounding lands for forage and prey could cause significant
harm to these lands. This also could cause effects on nearby human popula-
tions ranging from a minor nuisance to a significant economic hardship, for
example, if the search for food led the displaced animals into human dwellings
or into agricultural lands, of if predators were forced to prey upon domestic
animals.
Birds are the most important small animals in a coastal marshland from the
perspective of contaminant mobility. Birds forage on seeds, benthic invertebrates,
open channel vertebrates, and insects; some of these prey species may concentrate
a contaminant through direct ingestion (e.g., worms and filter feeders), or
through their own food source which has already ingested a contaminant and per-
haps concentrated it to some degree. Hence the birds may ingest significant
quantities of a contaminant and may then pass it through their digestive system
and deposit it offsite in feces or concentrate the contaminant in their own tis-
sues and then die or be preyed upon offsite. The former seems more probable.
The same set of circumstances may also apply to fish and insects, in which cases
the latter event is more likely.
Therefore it may be pointless to prohibit only horizontal crossings at the
land surface; some sort of barrier to movements above and below the surface
may also be desirable. The effects of such barriers would be considerable,
compounding greatly as the size of the area of exclusion increases.
7-24
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First, although net secondary productivity may change very little over a
long period of time, large short-term fluctuations may be expected as predator
species and prey species adjust to sudden partitioning from each other. It
is especially the prey species which may explode in population with a sudden
halt to predation. "Boom and bust" cycles of prey populations could be ex-
pected as the affected species increase their numbers, outstrip the available
food supply, and die back in catastrophic instances, whereupon the cycle is
renewed. Ifcan be seen that, within this cycle, vast effects on the food
sources of the former prey species can be expected.
Additional effects can be anticipated from the elimination of certain
species which spawn in the marshland. These effects may range from the triv-
ial to the extreme depending on the size of the area fenced from the intru-
sion, the availability of alternative breeding sites, and the importance of
the species whose spawning grounds have been contaminated.
Additional pressure on surrounding lands from avian predators and for-
agers displaced from the contaminated areas can be highly significant if sur-
rounding marshland is burdened beyond its capacity to produce food for the
o
displaced birds. This could, occur, for example, if half of a 20 km marsh
were fenced and screened* Thus, wildly fluctuating populations of predator,
prey, and forage species may occur offsite in areas unaffected by contamina-
tion.
Finally, diversion of migratory waterfowl from contaminated marshlands
can not only have serious effects on surrounding areas, but may also irrevoc-
ably reduce the populations of sensitive species already pressured by general
habitat reduction, diversion from nesting or wintering sites by human activi-
ties other than habitat reduction, and hunting. Such effects would be en-
tirely site-specific and cannot be addressed further for the general case.
(4-1) Asphalt Hard Surface Stabilization
This treatment is outside the scope of work.
(4-2) Conarete Hard Surface Stabilization
This treatment is outside the scope of work.
(5-0) Application of Sewage Sludge
This treatment is outside the scope of work.
7-25
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(6-1) High Presure Washing (<3 om)
This treatment is outside the scope of work.
(6-2) Flooding to SO am
This treatment is outside the scope of work.
(7-0) Soil .Amendments Added
ftiis treatment is outside the scope of work.
7.5 RECOVERY AFTER CLEANUP
Recovery of coastal marsh ecosystems following clean-up operations is de-
pendent upon several factors beyond the characteristics of the clean-up oper-
ation itself. Included in these factors are
the size of the area affected by the clean-up operation
location of the disturbed area relative to open water (areas
adjacent to open water are subject to wave and tidal effects
as well as fresh water runoff)
weather conditions following cleanup (heavy rains would
increase runoff erosion problems)
The sequence of events leading to "complete" recovery in a coastal marsh sys-
tem is not a multistep successional scheme such as is the case with develop-
ment of the classic climax forest. Recovery in the marsh system would be
essentially directly from disturbed state (e.g. denuded) to the original
vegetation type (e.g., Spartina). Graphs portraying a very general recovery
sequence are provided in Figures 7-3 through 7-5 (see Appendix B).
The rate of recovery is largely determined by the erosional processes.
which characterize the marsh system and which may be intensified by cleanup.
The growth rate of vegetation is probably secondary to the physical processes
determining soil stability and substrate composition. With the normal high
productivity rates characteristic of the marsh land type, once erosion is con-
trolled and revegetation initiated, recovery would be expected to proceed quite
rapidly.
7.6 QUANTITATIVE ASSESSMENT OF CLEAN-UP IMPACTS
Clean-up procedures in coastal marshes are scaled in Table 7-5 with re-
gard to impact on this ecosystem. The scaling provides a relative view of
the length of time (in growing seasons) required for complete recovery to the
7-26
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SOIL STABILIZATION (Chemical)
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Figure 7-3. Recovery of coastal inter-tidal marsh following chemical
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7-27
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VEGETATION REMOVAL
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7-28
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ACCESS BARRIERS
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Figure 7-5. Response of coastal inter-tidal
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7-29
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"natural" state after clean-up operations are terminated. It should be
stressed that these rankings are highly subjective in nature. The specula-
tive nature of these results is also emphasized by the location and meteor-
ological factors which will influence recovery.
The confidence with which this scaling is provided is somewhat inversely
related to the size of the area affected. This results from the uncertainties
related to recovery processes and the potential for external influences on
the marsh ecosystem subsequent to clean-up operations. Hence the scaling
here is much more relative than absolute (more numerical than quantitative).
The rationale for developing Table 7-5 is provided in Section 7.4. General
conclusions drawn from Section 7.4 and Table 7.5 are presented in the following
section.
Examination of Table 7-5 indicates that for the 0.01 km area, the treat-
ments may be grouped into three basic categories with regard to level of ef-
fect and length of time to recovery.
The lowest impact group includes construction of barriers (3-1, 3-2),
chemical stabilization alone (1-1), clear cutting (1-2) and soil covering
(1-7, 1-8). Tne common characteristic of this group of treatments is gen-
erally a lack of disturbance of the root and "native soil" structure. Or-
ganic muds and root systems may mitigate erosion, which is an important fac-
tor in recovery of the coastal marsh. Naturally, some disruption will occur
from the means and equipment involved in the clean-up operations. Hence, bar-
rier construction (3-1, 3-2) will have the least impact and soil covering
(1-7, 1-8) the most within this relatively low impact group of treatments.
Deep soil coverings (1-8) may elevate the marsh to a level where the
natural flooding cycles ar'e eliminated. Recovery in such areas would not
lead to a marsh habitat, but creation of a new terrestrial habitat type with-
in the coastal marsh.
The group of treatments which have an intermediate level of effect in-
cludes surface alteration (scraping and grading) alone (1-4) or accompanied by
chemical stabilization (2-6); stump and root removal (1-3); and removal of
the plow layer followed by chemical stabilization (2-7). These clean-up
treatments are characterized by a more severe disruption of the native soil
7-30
-------
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7-31
-------
structure than would be experienced with the lowest impact group. Thus the
potential for erosion is more substantial and recovery would be delayed as
a result.
In addition to increasing erosion, removal of roots and disruption or re-
moval of surface soils would remove the plant and soil materials which would
most enhance rapid habitat recovery. Root sprouting, which would occur after
clearcutting (1-2) would be eliminated and revegetation would occur via root
systems in adjacent areas and seeds dispersed by wind and flooding of the area.
Revegetation by seeds would be hindered to some extent by surface disruption
and soil removal.
The most deleterious set of clean-up treatments include removal of the
plow layer (2-1) and removal of the shallow root zone (2-2). The processes
of increased erosion and delayed revegetation, which are discussed above, are
enlarged by these treatments.
As previously stated, the level of effect associated with any of the
treatments for the marsh land type is area dependent. That is, the effects
generally increase with size of the area affected. This dependence can be
clearly seen from the importance of erosion in determining recovery and the
importance of neighboring areas for revegetation. With the smaller sized
clean-up areas, the surrounding area would act as a buffer for both tidal
and freshwater flooding events. In addition, seeding and root sprouting from
adjacent areas would be more effective with smaller cleared zones. Larger
clean-up sites would benefit less from these erosion buffer and revegetation
processes, and hence slower natural recovery would be expected.
Treatments which do not involve disturbing the spill area (i.e. natural
rehabilitation (0-1) and barrier construction (3-1, 3-2) would not have area
dependent impacts. However, some increased stress in adjoining areas may re-
sult with increasing size of barrier enclosures.
As discussed in the preceding sections several of the alternative clean-
up treatments may effectively destroy the marsh land type. In these instances,
recovery would not be to the original habitat form. Such treatments include
2-2, removal of the shallow root zone (less than 40 cm), and 1-8, deep soil
covering (up to 100 cm). The flooding cycle may be disrupted to the extent that
the former treatment results in an open water area and the latter in a more
7-32
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dryland environment. Because of these consequences, these treatment types may
not be reasonable with regard to recovery considerations. The effects of
other treatments are probably not irreversible although subsequent erosional
damage may result in an extended recovery period, particularly for larger
treatment areas.
7.7 CONCLUSIONS
Of the clean-up treatments considered, several were concluded to be inap-
propriate for the coastal marshland type. Shallow and deep plowing is not ap-
propriate for containment of spill materials. Mobility would be enhanced rather
than retarded by this action. Also, mechanical stabilization is inappropriate
as a mechanism for sealing the marsh soils against infiltration. This is because
infiltration control has no clear meaning for a frequently flooded environment
such as a marsh. For similar reasons, some chemical stabilizers are inappropri-
ate treatments in coastal marshes. However, for binding, soil materials together
to mitigate erosion, chemical treatments may be useful as a temporary measure,
particularly for rather small disturbed areas.
Soil removal methods were concluded to be the most deleterious to marsh
recovery. Effects of such treatment increases with the depth of removal.
Deep soil coverings may have similar effects. In fact, appreciable eleva-
tion alterations in either direction may effectively destroy the marsh hab-
itat; recovery may be to more terrestrial or to open-water communities. Chem-
ical stabilization may mitigate erosion and thus aid recovery for all soil re-
moval techniques from scraping and grading to removal of the shallow root
zone. Vegetation removal was felt to be less destructive than soil removal
treatments since the substrate materials which supported "climax" vegetation
may remain largely undisturbed. Clear cutting is certainly less detrimental
than removal of all vegetation and roots.
Barriers were felt to have little overall effect on the coastal marsh
although certain stresses in neighboring areas may result.
7-33
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7.8 COASTAL INTER-TIDAL MARSH REFERENCES
1. Bayly, I. A. E. and W. D. Williams. Inland Waters and Their Ecology.
Longman, Australia, 1973, 316 pp.
2. Bourn, W. S. and C. Cottam. Some Biological Effects of Ditching Tide-
water Marshes, Res. Rep. 19, U.S. Fish and Wildlife Service, 1950, 30 pp.
3. Brown, C. L. and R. Clark. Observations of Dredging and Dissolved Oxygen
in a Tidal Waterway, Water Resour. Res. 4(6):1381-1384, 1968.
4. California Department of Fish and Game. The Natural Resources of Capinteria
Marsh and Recommendations for Use and Development, Coastal Wetlands Series
No. 13, 1976.
5. Chapman, D. W. Effects of Logging Upon Fish Resources of the West Coast,
J. Forest., 60:533-537, 1962.
6. Frankenberg, D. and C. W. Westerfield. Oxygen Demand and Oxygen Depletion
Capacity of Sediments from Wassaw Sound, Georgia, Bull. Georgia Acad.- Sci.,
1969.
7. Moore, D. and L. Trent. Setting, Growth and Mortality of Crassostrea
virginica in a Natural Marsh and a Marsh Altered by Housing Development,
Proc. Nat'l. Shellfish Assoc. 61:51-58, 1941.
8. Smith, W. G. Spartina "Die-back" in Louisiana Marshlands, Coastal Studies
Bull. Special Sea Grant Issue, 5:89-96, 1970.
9. U.S. Dept. of Interior. Interim Classification of Wetlands and Aquatic
Habitats of the United States, U.S. Fish and Wildlife Service, 1976, 109 pp.
10. U.S. Dept. of Interior. A Study of the Disposal of Effluent from a Large
Desalinization Plant, Office of Saline Water R§D Prog. Rep. No. 316, 1968.
11. U.S. Environmental Protection Agency. Impacts of Construction Activities
in Wetlands of the United States, Rep. No. EPA-600/3-76-045, 1976, 392 pp.
12. Whittaker, R. H. Communities and Ecosystems. The Macmillan Company,
London, 1970.
7-34
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PART II
MANAGED ECOSYSTEMS
CHAPTER 8, AGRICULTURAL LAND AREAS
CHAPTER 9, URBAN/SUBURBAN LAND AREAS
-------
-------
CHAPTER 8
AGRICULTURE
8.1 OVERVIEW
Lands used for the production of renewable resources and products con-
sumed as food, fiber, timber, and feeds for livestock are by definition agri-
cultural lands. Crops raised for livestock feeds are discussed as forage,
permanent pasture, rangeland and the native pastures of woodlots. Plant spe-
cies discussed range from local area natives to patented specialty cultivar
crops.
In the broad sense, agricultural land could include tundra crops of li-
chens consumed by reindeer herds and the alpine meadows grazed by rodent her-
bivores. A narrower view is held in this chapter. Agricultural lands are
considered to be those managed to produce crops at commercially significant
rates for food, feeds, and fibers.
In this chapter the impacts by cleanup are taken as short-term disturb-
ances because the vegetative component can be replaced preciselyfor a price.
Mature deciduous trees as large as 20 to 23 cm in diameter and 8 meters tall
can be dug up, moved, and replanted in normal landscaping. Sodding or reseed-
ing is likewise economically determined as are most decisions about rehabili-
tation of agricultural lands after cleanup of some contaminant. As a routine
practice in the deciduous forest, a farm can be cleared of standing crops,
whether small grains or timbered woodlot, surface-mined for coal, the spoils
graded to the original contour, limed, fertilized, reseeded, and be back in
full production in 2 years. Equipment used in surface mining is different
from earthmoving equipment for local road building, light building construc-
tion and farming. In general, surface-mining earthmoving equipment is orders
of magnitude larger than usual construction equipment.
Agricultural land is estimated to be from 526 million hectares to 930
million hectares in the United States but a variety of figures are used for
agriculture depending on the author's interest. The percentages of use are
8-1
-------
approximately 25 percent for grazing in livestock production and 20 percent
for crop production.
This chapter concentrates on farming in three of the natural ecosystems.
These are the hot desert of the southwestern United States, where irrigation
supplies almost all agricultural water supply, the adjoining midcontinental
grasslands, and the formerly hardwood forest areas. These are located as
defined in Figure 8-1. Because it lies in the intermediate position between
the other two sources of agricultural land, and because almost the entire
grassland has been appropriated for agriculture, the prairie is described in
some detail with its crops. The irrigated desert is confined to gently slop-
ing or flat terrain and the actual commercial use is a small portion of the
desert terrain. Deciduous hardwoods occupy rolling to steeply sloping terrain
but agriculture is practiced on the flatter slopes which, as in desert, are
only a fraction of the total area.
Agriculturally important, the midcontinental grasslands in Figure 8-1
reach from the 30th parallel in the south to the north beyond the Canadian
border. Bordered on the west by the Rocky Mountains, they rise along the
105th meridian from the central Mexican border into Wyoming, turning north-
westly across 8 degrees of longitude before meeting the Canadian border. The
eastern grasslands boundary lies along the 96th meridian with a major incur-
sion, generally northeast on a concave arc, from the Red River into south cen-
tral Ohio. The east grassland boundary keeps west of the Mississippi River
to the Missouri River, crosses both in a few miles and arches north of the
Ohio River into central Ohio, north across Ohio, and turns generally west to
recross the Mississippi and parallel it to the northwest, crossing into Canada
on the 96th meridian.
Topography of the agricultural prairie ranges from the western short
grass high terraces and alluvial fans across the plains to the steep hills and
lakes on the eastern fringes of Illinois and west Ohio. The wide, level to
gently rolling plains with tree-clad streambanks in the prairie midsection
were the first to fall totally to the plow as croplands. Hard red winter
wheats grow in -the southern prairie and grade into hard spring wheats in upper
Nebraska north to the Canadian border. Annual precipitation in the winter
wheat belt ranges from 350 mm in eastern Colorado, Wyoming, and Montana to
8-2
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8-3
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900 mm in eastern Kansas and Oklahoma, with warmer summers and longer growing
seasons than the spring wheat belt. Precipitation" in the spring wheat belt
ranges from 300 mm in northern Montana to 600 mm in western Minnesota and
eastern Dakotas. Generally, the separation of the winter and spring red
wheats is the isotherm of 18°C for the three summer months of growth into
ripeness.
Precipitation regimes for prairie are shown in Chapter 2, Part I, and
these are basic figures around which agricultural needs are managed. In the
west side near the Little Powder River in northeast Wyoming, annual rainfall
is 400 mm with an evaporation potential for 1500 mm in an area where wheat
and oat agriculture displaced mixed prairie grassland and artemesia species,
but the primary use became cattle-grazing because of the combination of lim-
ited rainfall and deficiencies in soil phosphorus and nitrogen.
The physical characteristics of prairie soils reflect the environmental
regimes of the grasslands as shown in Table 8-1. On the Missouri side, the
soils are deep and the rainfall is sufficient for tall grass. The Colorado
side of the prairies have permanently dry subsoil and short grass. Between
these boundaries lies the minimum line of annual runoff shown in Figure 8-1
as the 2-cm precipitation isogram. The small grains straddle this precipita-
tion feature and their presence results in the designation of "breadbasket."
Table 8-1. Relationship between annual precipitation, species composition,
and moisture consumption, Rocky Mountains to Missouri transect
of prairie (adapted from Jenny
Indigenous
Plant
Community
Grama grass
Buffalo grass
Wire grass
Bluestem grass
Bunqh grass
Bluestem grass
Sod grass
Depth to
permanently
dry zone
(cm)
30-36
60-80
85-115
absent
Approximate
annual
pptn
(cm)
<45
45-55
55-70
70-100
Plant
height
(cm)
10-35
45
75
110
Region of
observations
Eastern Colorado
Western Kansas
Central Kansas
Eastern Kansas and
Western Missouri
8-4
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8.2 NATURAL PERTURBATIONS . .
The significant agricultural event in physical and economic terms is the
18
loss of soil by erosion processes. These losses are generated by two dif-
ferent agencies, wind and water runoff. West of the 2-cm isogram (Figure 8-1)
erosion is driven by wind. East of the 2-cm isogram water runoff is the
principal erosive force.
Publications dealing with erosion are numbered in the thousands. One
agency field office has collected 2,500 reports, bulletins, and books on wind
erosion alone. This author estimates runoff erosion publications number
more than twice as many as cited for wind erosion. A simplification is called
for.
The national wind erosion area is defined in Figure 8-2, while water
erosion sites are shown in Figure 8-3.
Wind erosion data and its erosive forces are used in general predictions
of soil loss as shown in handbooks. However, these must be used with cau-
tion. Attempts to estimate wind erosion by land types across the spectrum of
suggested cleanup techniques faces a basic inadequacy in the primary data.
The data on wind speed and direction are generally collected at airport loca-
tions and a few electricity-generating plants. These locations are represen-
tative of flat terrain rather than rolling, or hilly or mountainous regions.
The erosive power of wind may be seriously underestimated by using published
2 '
data to predict wind erosion damage for sites as small as 10 km and smaller
and a few kilometers distant, since the extreme wind speed is pertinent.
Horizontal extrapolation of wind speed for offsite predictions faces direc-
tional shear, turbulent discontinuities, and orographic deflection of unknown
magnitudes.
Wind-energy distribution maps are being undertaken at this time and may
alleviate a degree of the risk in making horizontal extrapolations from the
site of measurement to the cleanup site. These maps will be useful in flat
terrain under overcast conditions. They are not available for generic use
unless the cleanup treatments are restricted to the vicinity of airports.
Probably the best return in deciding what sites should be chosen as can-
didates for cleanup would come from installing remote wind recording equipment
8-5
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Wind erosion
Soil moisture-Wind velocity factor
Very low [1110-10%
Low
Intermediate ["JJ 26-60%
High ££381-150%
Very high QH > 150%
Figure 8-2.
Surface soil moisture-wind velocity soil loss
factor as a percent of soil loss at Garden City,
Kansas (marked by X) (adapted from Agricultural
Research Service^).
8-6
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Figure 8-3. Rainfall erosivity index, based on maximum
30-minute intensity, from an average of
annual maximums (from Wischmeierl?).
and precipitation recorders at the sites. From onsite data general regres-
sions would be possible with the weather station network data. Without onsite
data the predictions are worthless since they can be highly misrepresentative
of the site.
Rainfall intensity is the factor detaching soil fragments and allowing
runoff to carry them away. The data summarized in Figure 8-3 represent a
portion of the work done by Wischmeier and his colleagues." .One of their sum-
maries has been widely used in erosion predictions. Two reviews of erosion
dislocation mechanisms and of detachment by wind and water lay the basis
for the widely used "Universal Rainfall-Erosion Equation." This is based on
the kinetic energy of the rainfall and the maximum 30-minute intensity of
the storm. It must be used by trained staff for particular sites.
Plant growth, precipitation and climate are interrelated variables that
determine the erosive force exerted upon soil from which sediments are derived.
8-7
-------
A general integration for all these factors is shown in Figure 8-4. That
precipitation regime transects the natural ecosystems upon which the agri-
culture discussed in this chapter draws. These are the natural forces that
test the wisdom in selection of cleanup treatment, when the choice is field-
tested at a site.
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CENTIMETERS
EFFECTIVE PRECIPITATION
Figure 8-4. Idealized effective precipitation, vegetation, and sediment .yield
on west to east transect (adapted from Bennett and Donahue8).
8.3 MAN-MADE PERTURBATIONS
All agriculture is a man-made perturbation that functions as a production
system because of the energy added to change it from a natural ecosystem. In
8-8
-------
the context of this chapter the alleviation of natural perturbations on
cleanup areas is addressed.
The ideal preventative of wind and water erosion is a layer of wetted,
attached mulch. For semi-arid lands the procedures were derived after the
enormous dust storms of the late 1930s. The amount of mulch needed varies
with soil texture and species of crop. A summary of application rates for
deciduous forest agriculture is given in Table 8-2. As shown there seedling
plants hold soil losses to those comparable to tonnage quantities of straw
and stover (fodder) residues. Plant residues and seedling grasses are almost
universally used for wind and water erosion control.
Table 8-2. Effectiveness of ground cover on soil erosion
loss at construction sites in deciduous forest
zones.
Ground cover
Soil loss relative
to bare surfaces
(percent)
Established seedlings
Permanent grasses
Ryegrass (perennial)
Ryegrass (annual)
Small grain
Millet and sudangrass
Field bromegrass
Grass sod
Hay (5 tons per ha)
Small grain straw (5 tons per ha)
Corn residues (10 tons per ha)
Wood chips (10 tons per ha)
Asphalt emulsion (310 gal per ha)
1
5
10
5
5
3
1
2
2
2
6
2
(Adapted from Notes et al.11)
Large amounts of surface runoff are generated by acreages of cropped
soils. Need for runoff control is intensified where the soil is bared and
8-9
-------
multiple treatments are rated for runoff control in Table 8-3. These are
the kinds of combined treatments that are evaluated in Section 8,.6, Quanti-
tative Assessments.
Table 8-3. Control systems and relative effectiveness.
System
Components
Percent effectiveness
1.
2.
3.
4.
Seed, fertilizer, straw mulch plus
erosion structures, normal
Same as (1) except chemical (12
months protection) replaces straw
Same as (1) except chemical straw
tack replaces asphalt
Seed, fertilizer, straw mulch with
diversion berms plus sediment basins
Seed, fertilizer, straw mulch; down-
stream sediment basin using flocculants
Same as (3) without straw mulch
Chemical (12 months protection) sedi-
ment basin using flocculants
Same as (4) with seed, fertilizer
91
90
91
90
96.
94
94
96
(Adapted from Hotes et al.11)
8.3.1 Runoff and Fertilization
Runoff does more than produce sedimentation. It can strip away organic
matter and mulches. The plant nutrients lost in this way are some of those
recommended for reseeded areas in Table 8-3. These nutrient losses were
studied quantitatively on field plots in 1917 and included nitrogen, phos-
phorus, calcium, and sulfur. A recent review on phosphorus losses from
14
vegetables fertilized with manure placed losses at 70 kg/ha per year.
This is much more than many farm programs call for in fertilization regimes.
4
Seasonal variations are pronounced with three identified loss periods. Most
of the nitrogen and phosphorus loss occurred when the plants were newly estab-
lished and correspond to plowing and soil cover treatments evaluated in Section
3.6.
8-10
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The 24 cleanup treatments are potential treatments for a variety of
soils and crops grown in the desert, grassland, or forest. Representative
groupings of species for different purposes are shown in Table 8-4 with the
environment in which they are being produced. A number of the contaminant
removal techniques include soil removal to a. specified depth and these depths
can be compared to the optimum root zone shown in Table 8-5 that each species
will permeate in deep soils.
8.3.2 Soil Compaction
.The average density of weathered rock fragments in soil is approximately
2.5 times the density of water. Taking the density of air as close to zero,
compared to rock, and a mixture of 50 percent air and 50 percent rock, the
average density of the mixture would be expected to be about 1.25 times that
of water. For most soils with rock minerals as their principal ingredient,
the density is near 1.3. In these soils there is a little more rock than
air if the density is judged from this discussion.
Our hypothetical soil with 50 percent air would be a mass of small rock
fragments, with holes among the solid particles for the air. The rock frag-
ments would not float because they are about 2.5 times heavier than water.
After a rain part of the air space is filled with water; in fact,the escape
of air can be seen where water is held on soil as in basin irrigation. In
most soils the water wets the weathered rock particles and lubricates them
with the result that they slide across one another much easier wet than when
dry.
The objective in compacting soils is to squeeze the particles close to-
gether so the volume occupied by the soil is smaller, and the density is more
like rock than air. When the density is near 1.5 to 1.7 plant roots do not
penetrate and plant growth is halted. The water sprayed onto soil during
compaction is intended to lubricate the particles so they move across one
another under pressure from equipment. A list of equipment and the depths
to which it compacts the root zone is given in Table 4-2 of Chapter 4. These
are the depths to which the soil must be broken apart for crop production if
the soils are intended for agriculture.
8-11
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Table 8-4. Commercial crop species in managed ecosystems.
Ecosystem Forage/pasture Row crops/field crops
Desert alfalfa/ladino clover sugar beets/dry farmed
dry beans/dry fanned
vegetables/dry farmed
Grasslands sweet clover/ fescues corn /winter wheat
alfalfa/wheatgrasses soybeans /spring wheat
home grass sorghum /barley
sugar beets/rye
Deciduous clovers/1 espedosa corn
forests timothy/bluegrass soybeans
tobacco
vegetabl
Table 8-5. Rooting depths of agricultural
soils.*
/spring wheat
/oats
es
crops in fertile,
Orchards
citrus
apricot
peach
household
plants
apple
pear
peach
deep, well drained
Use/species
Forage
alfalfa
sweetclover
clover
timothy
Pasture
ladino clover
fescue
wheat grass
brome grass
1 espedosa
blue grass
Row Crops
cotton
sugar beets
dry beans
corn
*Examples are irrigated
Rooting depth
observed
(meters)
3-4
3
1-2
1
0.5
1-2
3-4
1-2
1
0.5
1.5-3
1-2
1.6-1.8
2
Use/ species
Field Crops
wheat
barl ey
rye
oats
flax
Orchards
citrus
peach
apricot
apple
pear
Row Crops
sorghum
soybeans
tobacco
vegetables
Rooting depth
observed
(meters)
2-3
2-3
2-3
2
2
2-3
2
5
8-10
2
2-3
1.5-2
1-1.5
1-4
desert and tall-grass prairie.
8-12
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8.3.3 Compaction and Runoff
Any description of hydrologic effects originating from clearing large
tracts of cultivated land and then resurfacing with an impervious layer de-
pends on having generic predictors available. The net hydrologic effects
from resurfacing do have an area-dependent generic factor. Intuitively, the
surface-storage of runoff is related to precipitation intensity and to local
topographic features. Resurfacing a flat, downwardly concave area creates
runoff storage capacity that may enhance groundwater supplies locally, but
resurfacing the rolling topography that formerly supported deciduous forest
has variable outcomes that are directly dependent on the area involved.
Flood water runoff on the northeastern belt of the former deciduous
forests of Ohio was most highly correlated with watershed area. However,
there were two distinctly different area-dependent watershed classes, so
different that square kilometers of area drained was used as the criterion
for dividing the classes. The zone separating the two flood classes was
o
50 to 75 km . Runoff volume correlated best with drainage area size, rain-
fall intensity, and soil infiltration rate. These three variables were sig-
nificantly different from random correlates (probability of random correla-
tion being less than 1 percent for all three variables taken together or
individually).
The effects of compacting soil on local runoff from micro-areas are
well known. Examples are streets that require storm drains and diversion
structures, parking lots, building sites, and construction areas in general.
Bar-Kochba and Simon rated infiltration rate into surface soil as the most
important non-climatic variable in their eastern Ohio study. Reduction of
surface water infiltration rates has the obvious effect of increasing runoff
and reducing groundwater recharge rates. This effect is less damaging upon
2
10-km areas in humid precipitation regions than in semi-arid zones where
agriculture depends on pumped water for crop production. Thus, the effect
of a compacted area in restricting groundwater recharge increases as the hypo-
thetical compacted area is moved westerly along a decreasing precipitation
gradient.
8-13
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8.3.4 Infiltration and Crops
In an intensively studied area, eastern Ohio, the average water infil-
tration rate for grassed areas was more than twice the intake rate of adja-
cent row-cropped fields. A soil-series-dependent influence on intake rate
was measurable but the relative infiltration rates were consistent among the
2
several soil series within the approximately 40,000-km study area. The
higher infiltration rate suggests why runoff is reduced and groundwater re-
charge increased by grass cover in deciduous forest agriculture. Grass is
the preferred cover for drainage waterways because the stems reduce runoff
flow velocity and the abundant fibrous roots keep soil aggregates in place
against detachment.
8.4 EFFECTS OF CLEANUP PROCEDURES ON AGRICULTURE
Qualitative descriptions of the effects that each of the different
cleanup treatments have on agricultural land are presented in this section.
The recovery of longer-lived agricultural crops to their precleanup produc-
tivity is briefly described in Section 8.5. Quantitative assessment of the
impacts of cleanup treatments on agricultural systems is given in Section 8.6
in terms of the estimated times required for return to commercial productivity.
The cleanup procedures described in this section have essentially three
different kinds of functions: (1) treatments temporarily holding the con-
taminant in place, (2) treatments physically removing contaminants which
depend upon stabilization after the cleanup to prevent wind or rainfall ero-
sion until rehabilitation occurs, and (3) restriction of access into the
area by humans and animals.
The projections made in this section are predicated on the information
which was available at the time the literature survey was completed. Serious
revisions of these recommendations or rejections of the projected consequences
of the cleanup in agricultural lands as more information is obtained appear
unlikely. However, a number of publications will soon be available which are
indirectly related to cleanup techniques in agricultural areas. Surface min-
ing in the Western states has resulted in a great many techniques being per-
formed for rehabilitation and reclamation of semi-arid and arid lands. These
techniques are experimental at present and are being evaluated for their
8-14
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effectiveness at the different sites involved in surface mining. In a few
years these experimental methods will have been published in journals which
carry reports of experimental research, and subsequently they will be in-
corporated into books and reports that will be of use to individuals con-
cerned with agricultural land cleanup after a contaminating event. An ;exam-
ple of the kind of material to be anticipated from surface mining rehabili-
tation is the statement in the recently released operating handbook published
by Coal Age. This handbook stated in its Foreword:
This Coal Age operating handbook of underground mining
is the first of a series of books planned to cover key
areas of present day coal mining operations. Future books
in this series will cover strip mining and reclamation,*
coal preparation, management, and maintenance"]
As noted in Section 8.1 the agricultural areas described as impacted
represent the irrigated southwestern desert, the short grass irrigated and
dryland agriculture on the west side of the American prairies and grasslands,
and from the midcontinent east to the northeastern middle-west of the United
States formerly covered by hardwoods and river bottom deciduous forests.
The desert area represents a transect across the American Southwest, extend-
ing east from the Imperial Valley of California to those irrigated parts of
New Mexico and southwest Texas.
The impact of the cleanup treatments on domestic animals is not covered
here. It is presumed that rehabilitation of contaminated areas for produc-
tion of agricultural crops is a prerequisite to any animal husbandry enter-
prises. The general crops for which cleanup impacts are described generally
fall within three groups of cultivars: (1) dryland and irrigated forage
crops, (2) commonly produced row crops and small grains, and (3) tree crops
ranging from the citrus orchards of the irrigated desert to the stone fruit
and pome orchards in originally deciduous forest areas.
CO-1) Natural Rehabilitation
Unlike natural ecosystems, agricultural ecosystems have no capacity to
replace the destroyed commercial crop by the same species after cleanup.
Since agricultural crops are grown at an energy cost, when this energy is
*Emphasis added.
8-15
-------
no longer supplied to the system the crops will no longer grow in commer-
cially productive quantities. Waiting for natural rehabilitation to replace
an agricultural crop is an unacceptable procedure. The time course of re-
turn from agricultural to natural ecosystems (Old Field Studies) has been
defined in Chapters 1, 2, and 3 under the heading Man Made Perturbations.
Further details for recovery sequences are in each of those chapters in
sections headed Recovery after Cleanup. Those descriptions should be re-
viewed before forecasting the vegetational changes that will occur on aban-
doned farmland. Ecologic journals are replete with flora succession studies
conducted on Old Field farmlands; they do not return to cultivars.
(1-1) Chem-leal S-tdb-Jt-izat-ion
Containing the contaminant to diminish its redistribution has an imme-
diate and obvious benefit in both hazard reduction and in minimizing the size
of the area of ecological impact by later cleanup methods. The function of
chemical stabilization in an agricultural system is to prevent redistribution
of the deposited contaminant. More than seventy stabilizers are reviewed in
Appendix A; those suitable for use in agricultural fields have been desig-
nated in Table A-l. With the exception of water-soluble emulsions, applica-
tion of a preferred chemical stabilizer requires a number of preparatory
steps before the field can be treated. The area to be treated must be cleared
of vegetation or clearcut, stumped, and grubbed for tree crops, the slash and
vegetative refuse removed, and the fields smoothed and either graded or shal-
low plowed. Most of the "preferred" stabilizers require direct mixing with
friable soils before they become effective in preventing resuspension of soil
and contaminant particles. Because of this requirement for similar pretreat-
ment, the after effects from most of the chemical stabilizers will be very
similar on the farmlands treated.
Chemical stabilizers which deflocculate soil particles, such as sodium.
chloride, sodium hydroxide, sodium carbonate, and Ca.lgon, are unsuitable for
use in western agricultural fields. Although this class of alkaline and high-
sodium dispersants would stabilize surface soil, they can only be used in
areas which have high levels of precipitation or access to free water in basin
irrigation. The requirement for large amounts of water is to assist plants
in withstanding the effects of the saline soil that would be produced by these
8-16
-------
stabilizers. Leaching of the soil for a long period of time before green
manure crops would compound the damage these stabilizers produce by removing
free salts, resulting in the deflocculated smrface soil becoming impervious
to water infiltration. Sodium adsorbed on clay disperses mineral particles
and prevents water infiltration. Lack of soil moisture prevents subsequent
plant growth. Growth of plants prior to extensive water leaching has been
found the simplest way to remove the effects of sodium deflocculants and
reconstruct soil tilth. Surface incorporation of high quantities of organic
matter into the soil is mandatory at the time recovery is instituted. Crop
residues from plants produced for organic matter (green manure), or addition
of mulch which is worked into the surface soil are standard procedures.
Thirty-six "preferred" stabilizers for agricultural use are listed in
Appendix A; 29 of these require reseeding or replanting of the crops to which
they are applied. The remaining seven would not destroy the crop to which
the stabilizer was applied. Appendix A has an additional list of 22 "accept-
able" stabilizers that are acceptable as alternates for use when the pre-
ferred stabilizer cannot be used.
Only 9 of the 58 stabilizers can be applied directly on growing crops
without totally endangering their commercial value. Two of the nine plant-
safe stabilizers require special handling for cropland application; three
of the nine that are safe for plants are water emulsions of asphalt or
resin, and four are colloidal suspensions of protein.
(2-2) Clearcutting Vegetation
Clearcutting orchards has the same effect as clearing coniferous and
deciduous forests insofar as crop production is concerned. It is very
improbable that the operators of commercial orchards would depend on stump
sprouting, for those species in which it occurs, as a method of creating
a replacement orchard. It is more likely that the trees would be removed
in toto (treatment 1-3). Clearcutting of irrigated and nonirrigated for-
age is the normal harvesting procedures and would have no significant im-
pact in cleanup considerations.
Row crops would be eliminated by Clearcutting if undertaken before the
normal harvest time. Clearcutting is the method of harvest for a number of
8-17
-------
row crops. Examples are machine-harvested tomatoes, combine harvesting of
all the small grains, the harvesting of the various species of maize and
sorghums, and the mechanical picking of cotton crops.
The physical structure of agricultural soils would be unaffected by
this treatment. Organic matter content would be undisturbed and the fer-
tility levels unchanged. There would be no change in the suitability of
seed beds for subsequent crop production.
(1-3)- Stumping and Grubbing
With the exception of orchards, this treatment is inappropriate for
agricultural crops. The effects of stump chippers and root rakes on east-
ern orchards would be similar to the effects described for deciduous forests
(Section 3.4). This technique would, of course, eliminate any productive
capacity of an orchard by eliminating the producing plants.
The physical effects on the soils in the eastern United States would
be due primarily to mixing the fertile surface layers with the relatively
infertile subsoil layers which the new tree roots would normally penetrate.
For desert orchard soils, there would be a small increase in fertility of
the lower segments of the profile and little decrease in fertility of the
upper parts of the profile, Irrigated desert citrus would be eliminated
as a crop, but the effects upon the soil structure would be relatively mild
for most undeveloped irrigated desert soils. The principal post-cleanup
effects would be the reduction in the fertility of the profile utilized in
the new mixed soil surface. This would need correction before reestablish-
ing orchards in the eastern United States. A secondary impact on eastern
orchards would be displacement of wildlife from hedgerows and fencelines
surrounding the orchards. The measure of any economic impact would be the
potential for a reduction in production of those crops dependent upon dis-
placed animals for pollination.
(1-4) Scraping and Grading
The consequences of surface scraping and grading upon any agricultural
crop is seasonally dependent. Performing this operation when fields have
been harvested and are normally clear of crops would result in removal of
8-18
-------
substantial portions of the limited organic matter in the desert, it would--';-
have essentially no effect in the grassland areas but clearcutting would make
it be an extreme perturbation in eastern orchard areas and on any of the grow-
ing eastern row crops. Surface soil would be laid bare to wind and water ero-
sion. If the soil were moist at the time of scraping and grading Cpresumably
by heavy equipment such as road graders, land scrapers, and bulldozers), sig-
nificant compaction would be likely to result (the effects of soil compaction
are described in cleanup treatments 2-3, 2-4, and 2-5).
The physical-chemical properties of most agricultural soils would not
be greatly changed by scraping and grading (excluding compaction effects).
The principal effects would be increased susceptibility to wind or water ero-
sion at the loosened surface. However, there would be little opportunity for
excess sedimentation since the basic runoff water diversion structures would
be unchanged.
(1-5) Shallow Plowing
Shallow plowing would eliminate an unharvested cultivated crop and, if
the crop were near maturity, would create a trashy surface. In the noncrop-
ping season its impact would be minimal or insignificant since plowing is a
normal operation of agriculture. Plowing with disc equipment would have lit-
tle impact on standing orchards in either irrigated or rainfed agriculture.
The most likely effect would be soil compaction in the wheel tracks, and fur-
row bottoms resulting from the use of plowshare equipment, if the soil were
significantly moist at the time operations were carried out.
The effects overturning the plow layer has on the seed sources, vegeta-
tion, and soil erosion processes of semi-arid rangeland sods-are overcome in
one or two seasons of regrowth. Shallow plowing of less than 10 cm has little
impact on survival of grasses but afterward the roughened surface is unsuit-
able for stabilizing by mechanical compaction because the surface is trashy.
Clays and deflocculants would fall among the sod chunks and be lost to subse-
quent stabilization techniques.
Runoff is reduced by the increase of surface storage in the roughened
area but groundwater recharge in the western shortgrass prairie would be un-
changed because the subsoils are permanently dry. Surface erosion by wind
8-19
-------
and water would be unchanged as grass cover is the cure recommended for both
erosion mechanisms.
Damage to woody plants is of short duration. Seed stocks would remain
and stump and root sprouts would soon revegetate the plowed rangeland. Ani-
mal grazing on the new growth may be a problem in establishing regrowth.
(1-6) Deep Plowing
Plowing to a depth of 40 cm would entirely disrupt any of the agricul-
tural crops during their growing season. If the land were fallow, it would
eradicate standing orchards, pastures, and rangelands. The fallow season im-
pact in areas with row crops and small grains would be relatively small and
approximately analogous to the consequences of shallow plowing (treatment 1-5).
Its effect in pastures and rangelands would be a reduction in productivity
of one or more growing seasons. On shallow profiles in the short grass prai-
ries it is likely to produce a mixing of the A- and B-horizons, reducing plant
growth in subsequent seasons unless fertilization, and possibly reseeding in
the drier areas (less than 35 cm mean annual precipitation), is carried out.
(1-7) Soil Cover Less than 25 cm
The significance of the impact on agricultural crops is a direct function
of the quality of the soil used for the cover. A soil high in clay would sig-
nificantly impair aeration in orchard crops and production decline would begin
in a few months. Attempts to add soil to areas with row crops would be im-
practical in terms of attempting to save the crop from the equipment. The
minimum impact would occur in those areas which are grassedeither rangelands
or irrigated grasses. Sweetclover forages would probably survive but the sur-
vival of irrigated forages, such as alfalfa and ladino clover, is uncertain.
The basic soil fertility in the root zone would be unchanged by this depth of
cover. The principal effects on seed bed suitability for cropping would be
fertility changes from the soil added. The soil used for covering would prob-
ably not be equal in tilth and fertility to the soil it covers up.
(1-8) Soil Cover 25 to 100 am
It is improbable that commercial agricultural crops would survive the
addition of a soil cover of this depth.
8-20
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(.2-1) Remove Plow Layer
This layer is about the minimum depth that can be removed as a controlled
cut by ordinary heavy earthmoving equipment. Soil removal would create a
radical disturbance in agricultural land, almost regardless of the crops that
were involved. It would totally destroy rangeland grasses, forage crops,
irrigated forage crops, small grains, and standing tree crops normally found
in orchards. It would represent an especially severe disturbance east of the
2-cm -runoff isogram (Figure 8-1). In the short grass prairie this treatment
accomplishes complete removal of the A- and a substantial part of the B-horizon
with the corresponding loss of the normal organic accumulation upon which the
fertility of the land is based. Removal of the organically rich A-horizon in
this area would leave the soil with a severe nitrogen deficit.
It is unlikely that any of the standing orchard species would survive
removal of the surface 6 inches of soil in the long term, outside of irrigated
areas. Minimum effect would be anticipated in those deep-lying desert soils
that are normally irrigated for crop production. These generally coarse-
textured soils allow a more rapid deep penetration of plant nutrients from
surface and shallow subsoil applications into the soil profile than occurs
with nonirrigated agriculture. However, removal of this layer in irrigated
agriculture would destroy row crops produced there.
(2-2) Remove Shallow Root Zone
On the shallower soils, removal of up to 40 cm of soil profile would
eliminate the fertilized root zone where the major dry-farmed crops are grown
(i.e., the infertile and highly calcareous regions of the short grass prairie
and in some of the caliche areas underlying irrigated deserts). The resulting
truncated soil profile would more nearly resemble an unpaved roadway after
deep cuts to maintain a uniform grade in hilly terrain. Shallow root zone
removal in the tall grass prairies would have relatively little effect since
the profile would still contain significant depth and amounts of organic mat-
ter below the soil cut away. In crop lands formerly occupied by deciduous
forests, this treatment would destroy the agricultural potential of many of
the farmed areas, eradicating the entire organic matter content of those soil
profiles as well as any residual artificial fertility elements applied to pro-
mote production of crops. The phosphate-rich plow layer would be removed and
the surface remaining would be more suitable for nonagricultural purposes.
8-21
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Prevention of erosion is the immediate problem in soil management when
the root zone has been stripped to a depth of 40 cm. West of the 2-cm runoff
isogram surfaces not naturally compacted or cemented are vulnerable to wind
erosion. East of the 2-cm isogram, post-cleanup surface erosion by runoff
water would be a severe problem throughout the stripped areas. Uniformly
removing 40 cm of soil surface would impair runoff diversion structures nor-
mally incorporated into farmlands. Removal of the shallow root zone west of
the 2-cm runoff isogram would leave a smooth erodible surface in the place
of the roughened trashy surface normally utilized to prevent wind erosion;
that is, planting ridges, grass waterways, lister ridges, shallow terraces,
and the basic contour structures would be removed. The basic contour struc-
ture could be maintained if care were taken during the soil stripping to take
the soil along field contours previously constructed for dry farming and
irrigation.
The most severe impact in the excavated agricultural areas would be soil
erosion. Other serious impacts relate to crop production, i.e., loss of the
soil organic matter, and hence loss of soil fertility.
(2-3) Remove Scraping and Grading, Mechanically Stabilize
This treatment would have little impact on the internal structures nor-
roal to control of overland water flovf in agriculture. The dikes, berms,
drainage ditches, grassed waterways, and overfall structures normally present
would be devegetated but not basically eradicated. Scraping and grading on
grasslands in pasture- and rangelands would remove the surface organic matter
layer, subsequently reducing nitrogen availability in the grasslands. The
principal consequence would be reduction of sedimentation onto lands adjoin-
ing the cleaned up area. Scraping and grading, removing the loosened mate-
2
rial, and stabilizing the surface in areas as large as 10 km would signifi-
cantly reduce sediment loss that would otherwise occur from scraping and
grading large areas.
The effects of this treatment and removal of deeper layers of soil to
40 cm were previously described in cleanup treatments 2-1 and 2-2.
The basic physical effects of this cleanup treatment on desert, grass-
land, and crops grown on the formerly deciduous forest lands have been de-
scribed in Chapters 1.4, 2.4, and 3.4 (under cleanup treatment 2-3) to which
8-22
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the reader is referred for added detail. The effects and probabilities of
wind erosion and runoff erosion by surface flow are discussed there and are
not repeated here. The descriptions in Chapter 2 (Prairies) are especially
pertinent to cleanup in areas producing grasses under dryland conditions and
for both native and reseeded vegetation on rangelands.
The number of mechanical stabilization procedures that can be used in
agricultural areas to be returned to croplands is limited. The slopes in
cropped areas are not usually steep enough to require that meshes, nettings,
or plastic films be laid in the areas involved. Furthermore, the areas; to
be protected in farmed fields may be so large that substantial problems would
arise from attempts to use plastic films as covers. In a relatively short
time the plastic would rip and tear and lose its effectiveness in containing
contamination. The otherwise usable mechanical stabilizations would subse-
quently require removal of an additional layer of soil because they are
variations of the compaction process.
The success of compaction methodology is directly dependent on the
amount of clay in the soil which is compacted. It is unsuccessful in the
coarse-textured, sandy soils frequently found in the irrigated desert where
reduction of pore space will be sufficient to destroy agricultural crops.
Removal of shallow soil and mechanical stabilization by compaction in an
orchard would kill the trees in a short time due to the combined effects of
poor aeration and severe moisture deficits brought about by preventing pre-
cipitation infiltrating into the soil profile of the orchard. If there is
enough clay in the surface soil for compaction to be effective, compaction
would be relatively permanent in agricultural terms. Return of the area to
agricultural productivity would require rippers, subsoil chisels, repeated
plowing, and other action to break apart the compacted layer and free the
^oil aggregates from the effects of prior compression. The offsite surface
flow of runoff would have a major impact on adjacent areas. For areas as
large as 10 km , uncontrolled runoff could be a significant factor down-
stream. It is also probable that there would be a drastic reduction of the
2
groundwater in an area where 10 km was mechanically compacted for stabili-
zation purposes. It is unlikely that deflocculants such as sodium chloride
would be tolerated for lands that were to be returned to agricultural pro-
duction, so mechanical stabilization or short-term chemicals are needed.
8-23
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(2-4) Remove Plow Layer-} Mechanically Stabilize ' .
The physical effects on the suitability of the cleaned-up area for agri-
cultural crops under this cleanup treatment are essentially the same as those
described under cleanup treatment 2-1. The effects of mechanical stabiliza-
tion would be very similar to those described in treatment 2-3. The princi-
pal differences relate to changes in organic matter and soil fertility induced
by compaction. .Where there is a relatively high water table and a high or-
ganic matter content below the compacted area (e.g., from a large root mass),
the fields would be subject to anaerobic decomposition of the organic matter
and the nitrogen would be reduced to ammonia forms with the potential for its
slow volatilization out of the soil profile. Effectively, the nitrogen con-
tent of the cropland would be reduced compared to that which existed prior
to the cleanup, as in treatment 2-3. Crop production could not be resumed
until the compacted area had been broken apart by mechanical means.
(2-5) Remove Shallow Root Zone, Mechanieal~iy Stabilize
The effects of this treatment, insofar as agricultural use of-the land
is concerned, are very similar to those for plow layer and shallow root zone
removal. Soil fertility would be reduced more than with removal of the plow
layer. The deeper truncation of the soil profile would render revegetation
of the rangcland or native pastures unlikely without renovation in the semi-
arid short grass prairie region. The desert soils on alluvial fans and
deeper profiles would be least affected by this treatment. The deeper cut-
ting is likely to have significant effects on surface runoff control struc-
tures in the sub-humid and humid agricultural regions. These control and
diversion structures would have to be reinstituted before surface stabiliza-
tion was undertaken if severe erosion effects are to be avoided. The same
soil preparation methodology as described for treatments 2-3 and 2-4 would
have to be undertaken to neutralize soil compaction disadvantages prior to
reestablishing agricultural production.
(2-6) Remove Scraping and Grading,, Chemically Stabilize
The physical effects upon agricultural production from this .treatment
are about the same as the combined effects of cleanup treatments 1-4 and 2-3.
The effects of chemical stabilization would, not be as. long-lasting as the
8-24
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mechanical stabilizing treatments, and in a number of cases immediate reveg-
etation with some variety of the grasses is required where runoff may cause
surface erosion. Infiltration into the soil profile is controlled by the
soil profile physical and chemical characteristics rather than by the chemi-
cal stabilizer applied; hence, it is unaffected by this treatment.
The most suitable chemical stabilizers to use in an agricultural area
are those which break down without leaving toxic residues that would impair
food values or plant growth at a later time. Some of the chemical stabili-
zers described in treatment 1-1 would be the stabilizers of choice in this
treatment also.
(2-7) Remove Plow Layer, ChemJoally Stabilize
This is a composite technique described separately under treatments 1-4
and 2-6. The overall consequence is one of reduced soil fertility with seed
bed conditions less suitable for reintroduction of agricultural crops than
those conditions resulting from treatment 2-6.
(2-8) Remove Shallow Root Zone, Chemically Stabilize
Slicing away the surface profile to a depth of approximately 40 cm would
require the greatest application of chemical stabilizers. Loss of the or-
ganic debris leaves the grassland soils susceptible to wind erosion, and re-
quires immediate reseeding with grasses to stabilize the soil against runoff
in sub-humid to humid regions. Removal of the loosened soil minimizes sedi-
mentation problems downstream in the runoff area but increases flooding po-
tential from runoff out of areas as large as 1 to 10 km2.
(3-1) Barriers to Exclude People
The most effective fencing for the exclusion of people would be a chain
link fence 6 to 10 feet high posing a physical restraint to trespassers.
(3-2) Barriers to Exclude Large Animals
Design of fences to restrain cattle is a well developed technology. Re-
straining of large game animals, such as elk and moose, is not likely to be
a problem in most agriculturally developed areas. Preservation of mechani-
cally and chemically stabilized surfaces would require that large animal
8-25
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traffic be restricted. The hooves of domestic cattle and sheep would rapidly
break down either of the stabilized surfaces, especially since the animals
are prone to travel single file which concentrates the cutting action of the
hooves in a small path.
(3-3) Barriers to Exalude Large and Small Animals
Attempts to eliminate small burrowing animals, such as ground squirrels
and gophers, would probably not be successful in large areas. Containment
of these animals within the area would be more successful than elimination.
Consequently, fencing should be directed towards retention of animals pre-
sumed to have become contaminated in the area rather than to keep small mam-
mals out of the area. Horizontally oriented small-mesh fencing in ditches
around the cleaned-up area and backfilling to provide a mesh ledge will pre-
vent the escape of both large and small burrowing animals. Because these
animals have a relatively limited home range there is not much danger of
them transporting large quantities of contaminants significant distances.
Fencing of successive containment areas may be the most practical method to
deal with burrowing animals. It is assumed that-larger animals can be suc-
cessfully excluded from contaminated areas until the appropriate cleanup
treatment has been selected for the area.
(4-1) Asphalt Hard-Surface Stdb-Llizat-ion
Consideration of the use of this treatment in an agricultural area
should be based on the understanding that it will be a very temporary cover.
Since the surface in most: agricultural areas will inevitably be disrupted
by stray cattle at some time soon after the material is laid down, it cannot
be considered to be a permanent way of securing a contaminant. In areas
where surface soil experiences freezing and thawing, such as the grassland
and deciduous forest areas, frost heaving is likely to be highly destructive
to an asphalted or road-oil treated area in a relatively few seasons.
Application of hot road oil or asphalt to an existing crop in agricul-
tural production would be disastrous. In most circumstances the standing
agricultural crop would be removed, with the possible exception of tree
crops. An agricultural crop must be considered a total loss if the appli-
cation of asphalt or hot road oil is necessary to hold the contaminant in
8-26
-------
place until subsequent cleanup treatments are undertaken. Few agricultural
crops can resprout and puncture heavy asphalt surfacing. The more damaging
effects would include compression tracks introduced by the heavy equipment
needed for transporting asphalt or hot road oil across the areas to be
treated. Reclamation of the sites will be an extremely expensive process
since the oil-soaked or asphalt layers must be removed before agricultural
production can be resumed.
(4-2) Concrete Hard-Surfaoe Stabilization
This is the most severe cleanup treatment proposed for use in agricul-
tural areas. The expense of removing the concrete at a later date almost
entirely eliminates use of this cover from consideration. It is inappropri-
"2
ate for use in areas as large as 1 to 10 km . The transportation costs of
recovering and disposing of the large amount of concrete that would be re-
quired for even 0.01 km is almost certain to eliminate it from serious con-
sideration in areas where agriculture is to be resumed.
. (5-0) Application of Sewage Sludge
The properties of urban sludge are significantly different from farm
manures and crop residues. The use of sludge requires highly specialized
information in agricultural management practices. Outright recommendations
for the application of sludge are unsafe. Urban sludge is still suspected
of containing viable viruses and must not be allowed to come into direct
contact with the edible portions of plants.
Sludge contains high quantities of industrial wastes at times. Such
wastes contain heavy metals which are poisonous to man: lead, cadmium,
chromium, copper, and nickel. Other elements hazardous to man (unless proper
soil management practices are used) are aluminum in various compounds, ar-
senic, selenium, antimony, and mercury. Wastes from industrial electroplat-
ing processes are extremely high in these particular metals.
Sludge supplies moderate amounts of nitrogen to cropland and increases
the organic matter content of soils. Sludge application is not safe for
crops grown on acid soils of the former deciduous forest areas for either
human consumption*or as animal, feeds. However, the low solubility of the
8-27
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heavy metal elements in neutral and alkaline soils minimizes these hazards.
Sludges contain from 1 to 6 percent nitrogen on a dry-weight basis. Moder-
ate amounts of sludge would supply nitrogen to croplands and significantly
increase the organic matter content of the soil. Five to 40 tons of dry
matter per hectare will supply nitrogen and organic matter in the alkaline
grassland and desert soils. A decay series worked out for breakdown of the
organically contained nitrogen indicates that approximately 25 percent of
the nitrogen will be available to plants in the first four years the sludge
is in the field. Approximately 30 to 60 percent of the nitrogen in the
sludge is in an inorganic form and would be readily available to plants in
the first year after the sludge application. This soluble nitrogen poses
a potential hazard to groundwater supplies. For this reason, large excesses
of sludge should not be applied in renewing the organic content of soils
following soil removal, scraping and grading of desert soils, or the addi-
tion of soil covers at a depth of 25 to 100 cm over croplands.
(6-1) High Pressure Washing (<3 mm)
This cleanup treatment is outside the scope of work for this report.
(6-2) Flooding to SO am
One-time flooding for redistribution of the contaminant into the soil
profile is outside the scope of work for this report.
(7-0) Soil Amendments Added
Experiments in which a variety of materials have been added to soils
for the purpose of preventing plant uptake of hazardous material have been
unsuccessful. Contaminants that are adsorbed onto the exchange surfaces
of soil minerals become available to plants either by contact exchange be-
tween the mineral surface and the root or by normal solution processes.
Once a contaminant is no longer retained on the surface soil but has, in
fact, penetrated the root zone of agricultural crops, the suggested reclama-
tion procedure is one of management that will produce luxuriant vegetative
growth that is discarded. This is accomplished by normal management prac-
tice, soil liming where needed in the deciduous area, and large additions
of nitrogen, potassium and phosphate to promote luxuriant plant growth where
8-28
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water supplies are adequate. In the prairie and desert areas the limiting
factor in land reclamation is the water supply. Attempts to immobilize
heavy metals to avoid plant uptake in the deciduous area have been unsuc-
cessful. Breakdown of the sludge releases nitrates, sulfates, and other
acid forms which will readily consume the added lime and result in highly
acid soils from which plants readily extract the injurious metals cpntained
in the sludge.
8.5 RECOVERY FOLLOWING CLEANUP
8.5.1 Irreversible Changes
The complement of cleanup techniques discussed in this report has no
irreversible changes. The limits to recovery of croplands are economic; the
question is whether to rehabilitate the spill area, soils, and crops. The
limits to the use of the most damaging cleanup practices, asphalt (treatment
4-1) and concrete (treatment 4-2), are the cost and effort required to in-
stall the asphalt/concrete cover and remove it later. The soils under these
two hard surfaces are damaged more by compaction than by seepage of chemi-
cals. Compaction can be rectified mechanically, as highway reconstruction
and relocation have shown.
8.5.2 Rates of Recovery
In this chapter all the cropping systems that are discussed have been
created by energy input by man. The rates of recovery from cleanup are
directly proportional to the energy input expended for rehabilitation in
agricultural systems. None of the agricultural systems described will re-
habilitate themselves to commercially viable levels once cleanup has been
performed. Agricultural systems do not follow the concept of species suc-
cession through intermediate stages to climax as described in Appendix B
for natural ecosystems. They follow the growth, pattern of one individual
plant.
Few of the environmental insults that may have extremely large impacts
in natural systems would have significant impacts in nonorchard agricultural
systems. Agricultural systems normally have structures appropriate for con-
trol of erosion by wind or water runoff. The suggested cleanup treatments
need not destroy structures.
8-29
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Rangeland and pasture grasses would need reseeding and modest nitrogen
fertilization to recover their productivity. Precipitation controls the
rate of recovery to be expected. Unusually intense rainfall would float
the seed away and drought would kill the seedlings after germination. In
normal weather, productivity on rainfed land is regained in 2 to 3 growing
seasons.
Row crops, small grains, and field crops would need the same management
they are given each season for normal productivity. The same recovery scheme
is appropriate to nontree irrigated crops. Land leveling for irrigation is
more severe than any of the recommended cleanup techniques; only mechanical
stabilization and asphalt/concrete resurfacing are more disturbing than re-
sloping a field for irrigation.
Orchards would require replanting after any but cleanup treatments 1-1,
5-0, and 7-0. First fruit bearing would begin in 5 to 6 years and full pro-
duction by 10 to 12 years, including citrus.
The general case for recovery of row crops, small grains, irrigated,
and rainfed pastures follows the sequence imposed by natural disasters such
as drought, fire, or flooding. Tree orchards likewise have as their recov-
ery model the growth and management steps that would follow renovation of
an old, declining orchard.
8.6 QUANTITATIVE ASSESSMENT OF CLEANUP IMPACTS
The impact assessment assumes in cleanup treatments that the contaminant
is on the surface soil initially, and that clearcutting is carried out before
any of the other temporary containment and removal measures (1-3 through 2-2,
2-3 through 2-8, and 4-1 and 4-2) are performed. Tree crops are assumed to
be entirely removed prior to soil manipulation, including root removal (treat-
ment 1-3) .
All erosion control devices for runoff are expected to remain functional
in the eastern hardwood croplands.
The impacts in this chapter require the intervention of man in almost
all cases after a cleanup treatment has been performed. The multitude of
corrective actions possible with four kinds of crops (forages and pasture,
row crops, small grains, and citrus, stonefruit and pome orchards), 24 cleanup
8-30
-------
techniques, and three ecosystems (desert, grassland, and deciduous forest)
requires that the impact analysis be general and easily reproduced. To that
end the impact indexing system is shown here for reference.
Response Required to Resume Production
No measurable impact, no correction needed
Loss ends with crop directly exposed to contaminant
Restored by normal agricultural practice for that crop
One renovating technique required for crop next year**
Two renovating techniques required for crop next year**
Three or more renovating techniques required for crop
next year**
Renovation restores crop production in second growing
season**
Greater than 5 seasons for commercial crop
Greater than 10 seasons for commercial crop
Index
Number*
0
1
2
3
4
6
7
8
The soil profile and climatic variables for pasture and grassed range
are discussed in Chapter 2.6. Removing 40 cm of soil on the Rocky Mountain
side of the shortgrass prairie cuts into the alkaline B-horizons. In that
region natural precipitation is too low for maize and orchards. On the Iowa
side of the grasslands revegetation will recover almost spontaneously in
rainfed pastures.
Cleanup techniques that are similar in impact intensity to normal farm-
ing are mowing (1-2) forage and pastures; shallow plowing (1-5) and scraping
and grading (1-4, 2-1) are similar to land leveling and are readily erased
by the usual seed bed preparation in row crops; and small grains. Trees are
entirely traumatized by clearcutting (1-2); thus stumping and grubbing and
subsequent operations have no additional effect on the tree crop. Trees in
orchards in the broad sense are totally destroyed by cleanup. They survive
*A11 treatments requiring unusual treatments for regaining productivity are
equivalent to conditionally retrogressive (Index Number = N+2).
**Renovating techniques are early reseeding, early transplants, annual fer-
tilizer additions, mulching, unusual irrigation, reterracing, recontouring,
and other substantial, unusual treatments such as early summer defoliation
of orchards.
8-31
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contamination retention processes and soil amendment but not any of the
standard decontamination procedures where soil is moved about.
No significant physical impact on the land occurs when barriers (3-0)
are used, but the economic impact caused to the owner by lack of resource
availability may be severe. This is true in all the systems reviewed and
for normal fertilization (7-0). Recommended chemical stabilizers (1-1) have
a similar impact across the species and soils and cause the loss of the
standing contaminated crop from the sprays and machinery used in the fields.
Clearcutting (1-1) forage and pastures is ordinary mowing and likewise costs
one cutting of one crop. On row crops the entire crop seasons' product is
lost from clearcutting (1-1) unless it occurs at harvest time. Sludge ap-
plications (5-0) are risky and surface applications are limited to fields
that grow animal feeds or to citrus orchards if injected into the subsoil.
Rendering the surface impervious to precipitation entry has two effects,
deficits in subsurface stored water and downstream channel flooding, whether
it is accomplished by soil compaction (treatments 2-3, 2-4, and 2-5) or by
paving (treatments 4-1 and 4-2). Groundwater in the treated zone is cut off
from local recharge and channel flow becomes proportional to the incidence,
intensity, and duration of precipitation once the surface threshold for wet-
ting is reached. Erosion control structures would need to be maintained on
all far^s to handle the increased runoff from soil stabilizers.
Loosening the surface soil by plowing (1-5, 1-6) and using soil covers
(1-7, 1-8) can lead to enormous runoff erosion losses but are otherwise non-
traumatic to forage, pastures, and small grains. Land leveling fills is
similar to treatment 1-4, and erosion control terracing and contouring fields
are analogous to treatment 1-8.
Hardsurfacing treatments (4-1 and 4-2) are likely to be acceptable on
a few acres if they are removed later or the land is condemned. The concrete
or asphalt residues are not especially harmful to plants where they have been
mixed with the soil. Removal of slabs might be expensive but hard surfacing
has features of, retention that other treatments lack.
No treatments were judged entirely prohibited on a reclamation basis,
except some chemical stabilizers.
8-32
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Successful soil compaction increases runoff from rainfall to high per-
centages. The proportion may increase to three-quarters of the local pre-
2
cipitation, and downstream flooding is assured in areas as large as 1.0-km .
The degree of success in compaction sets the magnitude of impact afterward
for degrees of hazard. An effective resurfacing depends on low organic
matter content in the soil and high clay. These are soil characteristics
of the deciduous forest agricultural areas. Cleanup treatments 2-3, 2-4,
and 2-5 have been given consistently high recovery time indices in ail non-
tree crops in deciduous areas, and lesser impact recovery time indices in
prairie. Mechanical compaction is impaired in prairie fields by the high
organic matter residue in the profile, even if 40 cm of topsoil is removed
as in treatment 2-5.
Lands in crops will have basic erosion control structures in place be-
fore cleanup where wind or water erosion is predictable; however, as the
area compacted increases in size, effects on underlying groundwater tables
and adjoining water sheds become more severe. Community flood control
structures needed for 1.0- and 10-km fields would exist in deciduous agri-
cultural zones.
Desert crop system impact indices are shown in Table 8-6. Removing
soil and chemically or mechanically stabilizing the fields has relatively
low impact because the coarsely textured soils pack together poorly and
plant nutrients are dispersed vertically throughout the profile. Surface
soil removal has less impact on fertility than in other land types, and a
lower impact recovery time index rating. Soil renovation practices needed
for recovery are ordinary irrigation management practices in irrigated
agriculture. Soil chisels and heavy fertilization are common.
Grasslands in small grains and irrigated row crops have deep lying
nitrogen reserves in the soil profile and are less impacted than the shal-
lower profile on the forested land types. The relative impact index for
grasslands under cleanup is given in Table 8-7. Soil cover in grasslands
may add weed seeds and be infertile, which has more impact than in forested
lands which are of lower fertility initially.
Removing the upper profile has severe impact on later crops in the
deciduous forest land type by removing fertility in organic matter and nu-
trients. The deeper cuts have greater impact as shown in Table 8-8. Runoff
8-33
-------
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erosion is more of a problem because the deep cuts on pastures remove pro-
gressively more grass roots, that have bound soil together. Row crops gen-
erally are on flatter slopes in well managed farms where erosion is less
severe than on scalped pastures.
8.7 CONCLUSIONS
The preferred cleanup treatments are those which isolate the food chain
from man. For small areas this may include fencing (treatment 3-1) or apply-
ing hard surfaces (treatments 4-1 and 4-2) to a small area with the expecta-
tion that they will be retrieved at a later date. Shallow or deep plowing
to 40 cm is acceptable with the exception of eastern orchards which might
suffer moderate root pruning from deep plowing. Seven of the chemical sta-
bilizers recommended for agricultural use would be appropriate in short-term
response to a contaminating event.
Cleanup techniques which axe inappropriate in an agricultural area ex-
pected to be returned to crop production are those which involve dispersing
soil by the addition of sodium compounds in large quantities, particularly in
either desert or semi-arid grassland areas. Removal of the shallow root zone
soil to 40 cm depth should not be considered for areas larger;than 1 or 2 hec-
tares because the problem of disposing of the contaminated soil is a greater
problem than other ways of decontaminating. Although fenced areas to exclude
cattle have been recommended in the natural ecosystems as a preferred treat-
ment, they are not recommended here because of their position near the top
of the food chain leading to man. Jt is almost inevitable that domestic
cattle would breach fencing in grassland or deciduous forest areas if the
land is left fenced for more than a few months.
8-37
-------
8.8 AGRICULTURAL REFERENCES
1. Agricultural Research Service. Predicting Rainfall-Erosion Losses from
Cropland East of the Rocky Mountains: Guide for Selection of Practices
for Soil and Water Conservation. Agriculture Handbook No. 282, U.S.
Dept. of Agriculture, 45 pp.
2. Agricultural Research Service. A Universal Equation for Measuring Wind
ErosionAn Aid to Conservation Farming in the Great Plains. U.S. Dept.
of Agriculture, Special Report ARS-22-69, 1961, 20 pp.
3. Agricultural Research Service. Wind Erosion Forces in the United States
and Their Use in Predicting Soil Loss. Agriculture Handbook No. 346,
U.S. Department of Agriculture, 42 pp.
4. Alberts, E.E., G.E. Schuman, and R.E. Burwell. Seasonal Runoff Losses
of Nitrogen and Phosphorus from Missouri Valley Loess Watersheds.
J. Environ. Qual., Vol. 7, No. 2, 1978, pp. 203-208.
5. . Don't drift . . . avoid Wind Erosion. Agribook Magazine,
Vol. 3, No. 1, 1977, p. 10.
6. Bar-Kochba, Y., and A.L. Simon. Factors Affecting Floods from Watersheds
in Humid Regions of Northeastern Ohio. Water Resources Bulletin, Vol. 8,
No. 6, 1972, pp. 1235-1245.
7. Barrows, H.L., and V.J. Kilmer. Plant Nutrient Losses from Soils by Water
Erosion. Advances in Agronomy, 15: 303-316, 1963.
8. Bennett, F.W., and R.L. Donahue. Processes, Procedures and Methods to
Control Pollution Resulting from Silvicultural Activities. Misc. Publi-
cation, U.W. Environmental Protection Agency, Office of Air and Water
Programs, Washington, D.C. 1973.
9. Chepil, W.S., and N.P. Woodruff. The Physics of Wind Erosion and Its
Control. Advances in Agronomy, 15: 211-302, 1963.
10. Godfrey, R.S., ed. Building Construction Cost Data, 34th Annual Edition.
Robert Snow Means Co., Inc., Duxbury, Mass., 1975, 330 pp.
11. Hotes, F., L.K.H. Ateshian, and B. Sheikh. Comparative Costs of Erosion
and Sediment Control, Construction Activities. EPA-430/9-73-016, U.S.
Environmental Protection Agency, Washington, D.C., 1973, 205 pp.
12. Jenny, H. Factors of Soil Formation. McGraw-Hill, New York, 1941.
13. Nuttonson, M.Y. Wheat-Climate Relationships and the Use of Phenology in
Ascertaining the Thermal and Photo-Thermal Requirements of Wheat. Ameri-
can Institute of Crop Ecology, Washington, D.C., 1955, 388 pp.
14. Ryden, J.C., J.K. Syers, and R.F. Harris. Phosphorous in Runoff and
Streams. Advances in Agronomy, 25: 1-45, 1973.
8-38
-------
15.
16.
17.
18.
D
, Fart it 1924.
> Z°n> Natural Vegetation. Atlas of American Agricul-
'H' WiSCh*eier-
Erosion. Advances in Agronomy,
Wischmeier W.H. A Rainfall Erosion Index for a Universal Soil-Loss Equa
tion. Soil Sci. Soc. Amer. Proc. 23: 246-249, 1959.
Wischmeier, W.H. Use and Misuse of the Universal Soil Loss Equation
Soil Erosion, Prediction and Control. Soil Conservation Society of
America, Ankeny, Iowa, 1977, pp. 371-378.
8-39
-------
-------
CHAPTER 9
URBAN/SUBURBAN AREAS
9.1 OVERVIEW
Urban/suburban areas differ from the agricultural and undeveloped areas
addressed in other chapters of this report in a number of ways that affect the
reclamation decisions and their impacts.
The characteristics of urban/suburban areas that may influence the cleanup
strategies and procedures are diverse. At one extreme, urban/suburban areas
include downtown areas of major cities which are completely covered by build-
ings and pavements, with residential and transient populations numbering hun-
dreds of thousands of people per square mile at any one time. In contrast,
urban/suburban areas also include single-family homes on spacious lots with
only a small fraction of the land area covered by buildings and paved walkways
and roadways, and with populations of, at most, a few thousand persons per
square mile. Between these extremes are various other types of land use
classes, such as commercial and industrial sections. In addition, within an
area of certain overall characteristics, such as a residential area of single-
family homes, great diversity can exist. Such places can have significant park
and recreational areas, scattered shopping centers and other commercial areas,
and undeveloped areas.*
In addition to the diversity of population density and land use and the
degree of structural buildup, a particular area will have other characteristics
that influence the cleanup options. Some of these factors are: the surface
and subsurface hydrology of the area, the existing sewer and storm-drain sys-
tem, availability of equipment and manpower, the source of water supply (in-
cluding areas outside the affected area whose water supply might become
*Undeveloped areas within urban/suburban areas are not addressed in this chap-
ter. For these areas, the land type which best describes the undeveloped
area should be determined and the appropriate chapter in this report referred
-to while recognizing that the greater likelihood of human exposure in the
vicinity of urban/suburban areas may require special considerations as to the
cleanup techniques.
9-1
-------
contaminated unless care is taken), season of the year (e.g., whether the
ground is frozen or covered with snow), and short-term meteorology (e.g.,
humidity, winds, likelihood of rain).
From this discussion it must be recognized that for any particular inci-
dent that releases contaminating materials in an urban/suburban area, the
courses of action and the effectiveness and consequences of such actions are
highly dependent on the specific situation. However, it is useful to attempt
to describe a "typical" urban/suburban area. One important characteristic is
the fraction of land area that is covered by (1) impervious surfaces such as
roofs, paved walkways and road areas, and (2) permeable surfaces consisting
of lawns, plants and trees, and bare earth. Each of these types of areas
requires different cleanup techniques having different environmental impacts.
The Census Bureau defines an "urbanized area" as a central city (or con-
tiguous cities) with a total population in excess of 50,000 plus the surround-
ing "closely held" populated areas, i.e., what is generally thought of as an
urban area and its suburbs (exclusive of large parks, golf courses, cemeteries,
etc.). Based on 1970 Census data, there were 248 such urbanized areas in the
United States with a total land area of 35,081 square miles and a total popu-
lation of 118,446,566 people, or 58 percent of the total U.S. population.
Thus, according to the U.S. Bureau of the Census , the average population
density in urbanized areas is 3,376 people per square mile.
National statistics regarding the fraction of ground surface covered by
streets, buildings and permeable surfaces in urban/suburban areas could not
be found, so residential areas in Santa Barbara, California, were randomly
selected and surveyed to develop these statistics. The population density of
the "place" of Santa Barbara is 3,333 people per square mile6, which is in
excellent agreement with the average population density of urbanized areas,
so it is assumed that statistics for Santa Barbara are reasonably representa-
tive of typical urban/suburban areas of the Nation.
Within single-family housing tracts of Santa Barbara, the approximate
coverage of the ground surface area is 20 percent by buildings; 15 percent
by streets; 8 percent by driveways, sidewalks, walkways, patios, etc.; and
the remaining 57 percent by lawn and soil areas. Thus within housing tracts,
9-2
-------
the impervious surfaces comprise approximately 43 percent of the surface
area. Such single-family housing tracts that are fully developed have popu-
lation densities of approximately 10,000 persons per square mile.
The above statistics are applicable for small areas within fully devel-
oped single-family housing tracts. Within a larger area, the permanent popu-
lation density is less because of commercial areas, open spaces, etc., and
therefore -the proportion of the area which is covered by impervious surfaces
may differ. A recent study was concerned with the recharge of groundwaters
in suburban areas of Santa Barbara. Within the area of interest of that
study, which can be described as primarily residential single-family suburban
housing tract areas (upper-middle to middle income housing), the population
density is approximately 3,500 to 4,500 persons per square mile (i.e., roughly
in agreement with the typical population density of an urbanized area). The
ground surface consists of approximately 37 percent impervious surfaces (build-
ings, streets, etc.), 24 percent lawn and yard areas, 9 percent agricultural
areas, and 30 percent open space and native vegetation areas. Thus it can be
seen that a surprisingly large percentage of a suburban area (39 percent for
the case of Santa Barbara) consists of areas having "rural" or "natural" char-
acteristics. However; the percent of surface which is impervious is not much
less than the value of 43 percent within housing tracts.
It is estimated that approximately one-half of the rainfall from small
storms in Santa Barbara that falls on impervious surfaces finds its way to
storm sewer systems with the remaining one-half soaking into the ground.4
Therefore, if the cleanup option is to flush the contaminant from building
roofs, streets, and walkways with water, approximately one-half of the con-
taminated water can be expected to soak into the ground unless measures are
taken to prevent this occurrence.
Other data for the upper Santa Ana Valley in California indicate that the
fraction of land area which is covered by impervious surfaces varies linearly
from approximately 20 percent for an area that is 40 percent urban developed
to approximately 70 percent for an area that is 100 percent urban developed.4
For the Santa Barbara area, which is approximately 60 percent urban developed,
the ground surface should be approximately 38 percent covered by impervious
surfaces. This is in excellent agreement with the actual value of 37 percent.
9-3
-------
In summary, the characteristics of small areas of 0.01 km in size withir,
an urbanized area may vary considerably. If one randomly selects a small area
within an urbanized areas, the probability is approximately 40 percent that
the area will have "rural" or "natural" characteristics rather than urban
characteristics. As the area, of contamination is increased to the maximum of
10 km2 used in this study, the characteristics of the area approach the aver-
age characteristics of 60 percent urban developed with 37 percent of the land
covered by impervious surfaces and a population density of approximately 3,400
people per square mile.
9.2 NATURAL PERTURBATIONS
Natural perturbations that produce some of the environmental effects that
could occur from cleanup treatments in urban/suburban areas include most of
the natural disasters, i.e., floods, fires, earthquakes, and severe storms.
In most cases, these natural perturbations will have significant effects on
man-made structures; whereas the reclamation treatments will have little ad-
verse effects. In contrast, some of the reclamation techniques will typically
have more adverse effects on the "natural" ecology of urban/suburban areas than
do natural disasters. For example, removing 40 cm of soil will destroy essen-
tially all vegetation, whereas no natural disaster is likely to produce this
degree of total destruction.
9.3 MAN-MADE PERTURBATIONS
A number of activities of man can cause destruction to the man-made envi-
ronment and the natural environment of urban/suburban areas. Such activities
include war, urban development or redevelopment, and spills of hazardous ma-
terials.
The normal construction activities associated with urban development or
redevelopment usually employ most of the cleanup techniques that are discussed
in Section 9.4. Typically, earthmoving and destruction of vegetation are re-
quired to prepare land for development. By design, the land is not allowed
to return to its natural condition; instead, lawns are established and desir-
able trees and smaller plants are planted. Within a few months to a couple
of years the desired vegetation, except large trees, is established.
9-4
-------
Spills of materials that are hazardous or ecologically damaging require
cleanup techniques identical or similar to the treatments for cleanup of radio-
active material. Again, in the urban/suburban situation there is usually no
significant lasting effect (except for social and economic impacts) because
the artificial man-made environment that is disturbed by the treatment can
usually be reestablished relatively quickly. An exception to this statement
would OCCIT if the contamination could not be cleaned up to the necessary de-
gree, forcing restriction or abandonment of an urban/suburban area or removal
of structures. However, even in this case the impact is primarily social and
economic, with little additional effect on the natural environment.
9.4 EFFECTS OF CLEANUP PROCEDURES ON
URBAN/SUBURBAN AREAS
The urban/suburban environment is largely a man-made environment, in
contrast to the natural environments of undeveloped areas. Some cleanup op-
tions that might^cause significant environmental impact in undeveloped areas
(e.g., vegetation clearing, removal of soil layers, and applying soil cover)
are common activities in urban/suburban areas.
Because of the greater hazard to humans from contamination of urban/
suburban areas, a greater cleanup effort is not only justified but required.
To clean up the area to the maximum possible extent, a series of cleanup tech-
niques would probably be used rather than a single technique. The effective-
ness of the cleanup is primarily limited only by the monetary cost of carrying
out the tasks. For example, contaminated roofs could be stripped of shingles
and reshingled if necessary. Contaminated pavements could even be removed.
In an urban/suburban area, virtually the entire surface area could be stripped
and removed without significant impact on the "natural" ecologybut with a
high monetary and social cost.
Treatments that can be used in urban/suburban areas to remove contami-
nants or to reduce the hazard from such contaminants can be grouped into
those that lend themselves to application for lawn, plant, and soil areas in
yards and parks (treatments 1-1 through 7-0 in the following list), and those
that lend themselves to application for hard, relatively impervious, artifi-
cial surfaces, such as building roofs, walkways, and paved areas (treatments
8-1 through 8-7 in the following list).
9-5
-------
Treatments for Lawn, Plant and Soil Areas*
0-1 Natural Rehabilitation-
1-1
1-2
1-3
1-4
1-5
1-6
1-7
1-8
2-1
2-2
2-3
2-4
2-5
2-6
2-7
2-8
3-1
3-2
3-3
4-1
4-2
5-0
6-1
6-2
7-0
Chemical Stabilization
Clear Cutting Vegetation
Stumping and Grubbing
Scraping and Grading
Shallow Plowing
Deep Plowing
Soil Cover Less than 25 cm
Soil Cover 25 to 100 cm
Plow Layer
Shallow Tloot Zone
Scraping and Grading, Mechanically Stabilize
Plow Layer, Mechanically Stabilize
Shallow Root Zone, Mechanically Stabilize
Scraping and Grading, Chemically Stabilize
Plow Layer, Chemically Stabilize
Shallow Root Zone, Chemically Stabilize
Remove
Remove
Remove
Remove
Remove
Remove
Remove
Remove
Barriers to Exclude People
Exclude Large Animals
Exclude Large and Small Animals
Asphalt Hard Surface Stabilization
Concrete Hard Surface Stabilization
Application of Sewage Sludge
High Pressure Washing (<3 mm)
Flooding to 30 cm
Soil Amendments Added
Treatments for Hard, Impervious, Artificial Surfaces
8-1 Washing with High-Pressure Water (Firehosing)
8-2 Vacuuming
8-3 Sweeping
8-4 Mechanized Street Flushing
8-5 Surface Removal Techniques
8-6 Other Removal Methods
8-7 Containment
' In general, treatments 1-1 through 1-8 are not treatments for the removal
of a contaminant (although 1-2 is a removal treatment if contamination of
vegetation is significant). Instead, these treatments are those that might be
*This list of treatments applies to all land types, and is included for a com-
plete discussion. Some of these treatments are not appropriate for urban/
suburban areas.
9-6
-------
applied as a temporary measure to hold the contaminant in place to prevent its
redistribution. In the case of treatments 1-5 through 1-8, the immediate haz-
ard is reduced because the contaminant is shielded by soil cover.
Treatments 1-1 through 7-0 apply to land types in general. Most of these
treatments also apply for the lawn, plant, and soil areas (yards) of urban/sub-
urban areas. However, in the urban/suburban situation some of the treatments
may be more appropriate than others and the environmental impacts may be sig-
nificantly different than would be the case for an undeveloped or, agricultural
area.
Because of the greater potential hazard from a contaminating incident in
a populated area, several of the treatments might be used on urban/suburban
yards so as to reduce the hazard to the maximum practical extent. For example,
a stabilizer might be applied to lawns to hold the contaminant in place while
the sod is removed and any residual contamination hazard might be further re-
duced by turning over the soil before resodding.
Depending on circumstances it may be desirable or it may be -undesirable
to coat the ground with a sealant, such as liquid asphalt, so that contami-
nated water from washing of roofs and walkways will run off into the storm
drain system rather than soak into the soil.
Flushing with water or blowing with compressed air may remove the con-
taminant from the foliage of plants if the resuspension in air or the washing
into the soil of the contaminant is acceptable. Otherwise, the contaminant
can be fixed onto the leaves of the plant by a stabilizer and then the plant
can be pruned, defoliated, or removed.
Some of the treatments which are used for cleanup of hard artificial
surfaces, such as sweeping and firehosing, cam also be used with some limited
effectivess on frozen ground.
Each of the potential treatments is discussed below in the order listed.
The discussion is based primarily on Owen et al. and to a lesser extent on
Bennett and Owen and Cobb and Van Hemert.
9-7
-------
9.4.1 Lawn, Plant and Soil Area Treatments
(0-1) Natural Rehabilitation
Because of the proximity of humans, it is assumed that doing nothing to
clean up urban/suburban areas is not a viable option; rather, any contamina-
tion will have to be reduced to some acceptably low level. Therefore, natural
restoration does not apply for urban/suburban areas.
(1-1) Chemical Stabilization
The purpose of the chemical stabilizers is to hold the contaminant in
place, to prevent redistribution until the contaminant can be removed. The
properties of the general classes of chemical stabilizers are given in Appen-
dix A, Soil Stabilizers. Chemical stabilizers vary as to their effectiveness
and longevity in holding the contaminant in place and in their effects on
vegetation. Some of the stabilizers cannot be used without necessitating
subsequent removal of the vegetation>
In lawn areas the sod will undoubtedly be removed and the lawn area re-
established with seed or resodding, in which case the use of chemical stabi-
lizers has no significant adverse environmental effect.
(1-2) Clear Cutting Vegetation
For lawns and ground covers, this treatment consists of mowing or perhaps
renovating down to the soil. There is no significant adverse effect from mow-
ing or renovating, since the root zone is not damaged and the grass or ground
cover grows back relatively quickly.
In general, clear cutting of bushes and trees is to clear the ground sur-
face for plowing or soil removal. Many bushes, and some trees, will reestablish
from the r-oot systems of the clear-cut vegetation, although not as quickly as
grass. The time to reestablish varies from a year for small shrubs to many
decades for large trees.
(1-3) Stumping and Grubbing
This treatment contributes little additional impact to that which occurs
when the trees and bushes are cut down. If trees are cut down, new trees would
probably be planted so removal of stumps is desirable. Shrubs would have to be
replanted rather than allowed to propagate from existing root systems.
9-8
-------
(1-4) Scraping and Grading
The removal of up to 5 cm of soil by scraping and grading is equivalent
to removing the sod layer for lawns. Removal of this layer will not have any
effect on trees and larger shrubs unless they must be removed to provide room
for equipment. Smaller plants may be damaged, but they would likely be re-
moved in any case to ease the task of scraping and grading.
(1-5) Shallow Plowing
The disturbance of the upper 10 cm of soil by shallow plowing will have
more significant effects than treatment 1-4. If plowing is done close to
small plants they may be killed by root disturbance; but most trees will not
be killed or seriously damaged by plowing to this depth.
(1-6) Deep Plowing
Deep plowing (10 to 40 cm) will have more serious effects on trees. Most
trees in yards and parks have shallow root systems because of improper water-
ing; plowing to a depth of 40 cm will damage these root systems. However, be-
cause of interference by larger roots it may not be possible to plow close to
the tree, so many trees that might otherwise be killed by close plowing will
survive.
(1-7) Soil Cover less than 25 am
(1-8) Soil Cover 25 cm to 100 am
If not only a temporary treatment, and if not removed within a relatively
short time period, soil cover in an urban/suburban area will change grade lev-
els and affect water drainage around buildings. As a short-term measure, add-
ing soil cover will not affect trees and larger bushes. Smaller bushes may be
covered and killed and lawns will die in a short time period.
Except for palms, trees cannot tolerate the permanent addition of soil
unless measures are taken to ensure adequate air circulation about the trunk
down to the original grade level. If soil is placed around the trunk, rot
will set in and the tree will eventually die. The addition of 25 cm of soil
will have no effect on trees if it is kept from the trunk. A 100-cm layer
requires a larger space around the trunk to ensure adequate air circulation,
and can be expected to affect the root system of the trees by oxygen depletion.
9-9
-------
There may be practical limitations on using soil cover. To cover the
ground to a depth of 100 cm in one square kilometer of the typical urban
area, whose surface is comprised of 63 percent soil and vegetation, requires
824,000 cubic yards (630,000 cubic meters) of fill soil.
Treatments 2-1 through 2-8 are designed to remove a contaminant from
yards so that it can be transported to a safe place. These treatments are
straightforwardby whatever means are practical, sod and layers of soil are
removed until the residual contamination is at an "acceptable" level. In the
urban/suburban situation, uncontaminated topsoil will usually have to be
brought in as fill to restore yards to the original grade level. Stabilizers
might be used to prevent erosion, but stabilization techniques which have
adverse effects on the revegetation of the area, such as compacting, would
not be required. Stabilization is required only for a relatively short time
period while lawns become established.
The depth to which soil can be removed from around a tree without injur-
ing or killing the tree depends on the proximity of the root system to the
ground surface. This, in turn, primarily depends on the type of tree, its
location, and the watering it has received. Some of the most desirable trees,
such as maples and some oaks and conifers, have relatively shallow root sys-
tems. Also, because of frequent and shallow watering, trees in yards often
develop root systems relatively close to the ground surface; such trees ar&
more susceptible to damage from soil removal than are trees which rely on
rainfall.
For lawns, using sod cutters and rolling up the sod for hauling away is
effective. Past experiments indicate that this procedure will remove 98 per-
cent to 99 percent of a contaminant. Removing sod by garden tractors or by
hand shoveling appears to be less effective in removing contaminant than us-
ing a sod cutter, although the data are limited.
Where access is not restricted, larger machinery such as bulldozers, back-
hoes, road graders, etc., may be used to scrape off the top layers of soil.
Typically, for large working areas, removal of 5 to 10 cm of soil will sig-
nificantly reduce contamination, although results are quite variable. For
smaller working areas, such as typical urban/suburban yards, the effectiveness
of heavy machinery is limited and it must be supplemented by hand labor.
9-10
-------
The magnitude of the disposal problem associated with removing contami-
nated soil, and the task of hauling in uncontaminated soil for fill, must be
appreciated. Removing the plow layer of soil (10 cm) from the "typical"
urban/suburban area requires the disposal of 82,400 cubic yards (63,000 cubic
meters) of contaminated earth per square kilometer, compacted to the original
density. Disturbed earth takes up more volume than undisturbed earth, prob-
ably by a factor of 20 to 40 percent, so removing the plow layer of soil from
a 10-km2 typical urban/suburban area requires disposing of approximately one
million cubic yards of contaminated earth and hauling in the same volume of
uncontaminated earth for fill. Removing soil in the shallow root zone quad-
ruples these requirements.
(2-1) Remove Plow Layer
In the urban/suburban situation there is little impact from removing the
top 1.0 cm of soil from yards. Lawns can be reseeded or resodded, and plants
and small bushes can be replaced. Only very shallow-rooted trees will be
seriously damaged or killed by the removal of soil to this depth.
(2-2) Remove Shallow Root Zone
Whether or not a tree is killed from removal of 40 cm of soil depends
on the particular tree and its situation; however, in general, the removal
of this amount of soil will probably kill most trees that do not have signif-
icant taproots. The use of heavy equipment will cause more damage than care-
ful use of hand tools.
, . : » " ' , , ".
(2-3) Remove Seraping and Grading, Mechanically Stabilize
Removal of the top 5 cm of soil will have no significant effect on trees
and large bushes. This is equivalent to removing the sod layer from lawns.
The lawns can be reseeded or resodded, and smaller plants that have been
removed can be replaced. Compacting of the soil for erosion control would
not be required; other means of stabilization that are practical would have
no significant adverse effects.
(2-4) Remove Plow Layer, Mechanically Stabilize
The impact is the same as for treatment 2-1, provided compacting or hard-
surface stabilization techniques are not used.
9-11
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(2-5) Remove Shallow Root Zone, Mechanically. Stabilise
The impact is the same as for treatment 2-2, provided compacting or
hard-surface stabilization techniques are not used.
(2-6) Remove Scraping and Grading, Chemically Stabilize
The impact is the same as for treatment 2-3.
(2-7) Remove Plow LayeT3 Chemically Stabilize
The impact is' the same as for treatment 2-1.
(2-8) Remove Shallow Root Zone, Chemically Stabilize
The impact is the same as for treatment 2-2.
(3-1) Barriers to Exclude People
This technique is probably practical only as a short-term measure while
the contaminant is removed. Barricading people from urban/suburban areas to
which they normally have access for longer than a few days or weeks would
cause considerable social disruption and adverse economic impact.
(3-2) Exclude Large Animals
Any barrier to exclude large animals would also exclude people, which is
unacceptable in an urban/suburban area except for a brief time period. Because
of the relative scarcity of large animals in urban/suburban areas, there would
be no significant impact on them.
(3-3) Exclude Large and Small Animals
Except for very small areas, exclusion of small animals would be difficult.
Household pets would have to be relocated with their owners or impounded. Wild
animals, primarily birds and rodents, might multiply. They also might become
vectors for spreading a contaminant to other areas.
(4-1) Asphalt Hard-Swfaoe Stabilization
Probably in most cases asphalt hard-surface stabilization would be com-
bined with some degree of plant and soil removal, thus entailing additional
logistic and economic problems both for initial treatment and subsequent
9-12
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removal. An asphalt surface would kill any unremoved vegetation. Unre-
moved trees would die from lack of water and oxygen to the roots.
Ii^JLLJ?grcorete Hard-Surfaae Stabilization^
The same comments apply as for treatment 4-1, except that concrete would
provide a more permanent surface or, if removed, be slightly more difficult
to break up and transport.
(5-0) Appliaation of Sewage Sludge
Outside the scope of work.
(6-1) High-Pressure Washing
Outside the scope of work.
(6-2) Flooding to 30 am
Outside the scope of work.
(7-0) Soil Amendments Added
Outside the scope of work.
9.4.2 Impervious, Artificial Surface Treatments
The treatments that may apply to remove a contaminant from the hard, im-
pervious artificial surfaces that cover much of the urban/suburban land areas
are: washing with high-pressure water (treatment 8-1), vacuuming (treatment
8-2)," sweeping (treatment 8-3), mechanized street flushing (treatment 8-4),
surface removal techniques (treatment 8-5), and other removal techniques
(treatment 8-6).
As would be expected, smoother surfaces retain less residual contaminant
than rougher surfaces, larger particulates are more effectively removed than
smaller particulates, and the fraction of contaminant removed is greater for
initially greater loading densities. Data on the effectiveness of the cleanup
techniques are primarily based on results of simulations using sand. The par-
ticulate sizes were often on the order of 100 microns or more and the surface
loading densities on the order of 100 grams/ft2. For smaller particulates and
less dense surface loading, effectiveness should be considerably less.
9-13
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(8-1) Washing with High-Pressure Water f>3 mm)
Large, impervious areas such as roofs and streets can be cleaned by high-
pressure streams of water. The high-pressure water dislodges and dilutes most
of the contaminating particles and carries them away in the runoff. In this
case, the contaminant is simply being moved to a different location. Deter-
gents, manual or motorized scrubbing, and special hose nozzles may be employed.
In general, firehosing has been envisioned as an emergency technique to be used
in catastrophic situations to clean up a relatively large populated area where
concern with the runoff of contaminated water is secondary to reduction of the
immediate hazard.
Examination of results from numerous experiments summarized by Owen et al.
indicates that, in general, firehosing will remove 90 percent or more of con-
taminating particulates from areas paved with asphalt, concrete, and asphaltic
concrete. Often less than 1 percent of the residue remained after a single
pass. Repeated passes with the water stream removed more contaminant, but
with decreasing effectiveness. Contaminants in slurrys appear to be removed
as effectively as are particulates. Although roofs are not as effectively
firehosed as are street areas, tar-and-gravel and composition shingle roofs
can be 90 percent or more decontaminated. Limited data on wood shingles indi-
cate 80 to 90 percent decontamination effectiveness.
Firehosing roofs and paved areas requires 10 to 20 liters of water per
square meter of area per pass. To treat a typical suburban area in .this man-
ner would require 1 to 2 million gallons (3.7 to 7.4 million liters) of water
per square kilometer per pass, exclusive of water needed to wash down vertical
*l O
surfaces. Even the smallest-sized area of 0.01 km would result in 500 to
1,000 50-gallon drums of wastewater. Thus, except for very small areas, it may
not be practical to collect and store contaminated wastewater from cleanup .
Hosing down impermeable surfaces simply moves the bulk of the contaminant.
to a different location and/or reduces it to more acceptable concentrations.
Runoff from structures moves the contaminant to the ground level onto other
impermeable surfaces, or onto soil and plants. Flushing walkways and streets
moves the contaminant onto soil surfaces or into storm drain systems. If
9-14
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measures are not taken to collect the runoff, shrubs, lawns, and bare earth
areas will receive contaminated water as will storm drain discharge points.
Uncontaminated, permeable surfaces can be sealed with substances such as
liquid asphalt to prevent contaminated runoff water from soaking"into the
ground. However, it is unlikely that all splashes can be contained; in fact,
it may be desirable in some instances to let contaminated runoff water soak
into permeable ground surfaces as a means of contaminant collection. Radio-
active contaminants are often quite insoluble and can be effectively filtered by
soils, and the portions that are soluble are quickly adsorbed onto surface
soil particles. For example, as discussed in The Behavior of Radioactive
Fallout in Soils and Plants^ approximately 99 percent of fallout is insoluble
(in distilled water) and a solution oi soluble portions poured through the
soil in one set of experiments was 80 to 85 percent adsorbed by the first few
centimeters of soil. Plutonium, a radionuclide of great concern, is very in-
soluble in water and might best be trapped by soil filtration and subsequent
removal of a layer of soil.
(8-2) Vaouuming
Removal of contaminating particulates from hard surfaces by vacuuming has
not been examined in as much detail as other techniques, such as firehosing.
The reason for this relative neglect may be because of the slow working rate
compared to firehosing. A street can be firehosed at a rate of 300 to 500
square feet per minute compared to a few tens of square feet per minute for
vacuuming. Nevertheless, examination of the data from Owen et al.5 indicates
that vacuuming can be effective in removing particulate contamination from
hard surfaces. In general, based on a limited number of experiments, vacuum-
ing can remove in excess of 90 percent, and sometimes in excess of 99 percent,
of the particulate contamination from composition shingles and concrete with
a single "pass." In the single experiment where repeated vacuumings were
employed to decontaminate concrete, the second vacuuming removed 90 percent
of the residue from the first vacuuming and the third and fourth vacuumings
removed about one-half of the remaining residue. Thus, it appears that care-
ful vacuuming can remove in excess of 99 percent of particulate contamination
from pavement and roofs. In an experiment for decontaminating frozen bare
ground, vacuuming removed about 60 percent of the contaminant after 4 passes
(40 percent was removed on the first pass).
9-15
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Details on the design of the vacuuming experiments are not.available,
but it is presumed that the particulates were "fresh," i.e., the particulates
were not allowed sufficient time to "weather" and become more firmly attached
to the contaminated surfaces.
Vacuuming has a significant advantage over firehosing and other types of
methods that simply move the contaminant to another location because vacuum-
ing picks up the contaminant and contains it for safe disposal. Care must be
taken that absolute filters are used, in addition to the coarse filters in
the typical vacuum cleaner, so that very small particulates will be trapped
rather than resuspended in the air by the cleaner's exhaust. Otherwise, no
adverse environmental effects appear to be associated with vacuuming contam-
inants from hard surfaces.
(8-3) Sweeping
Mechanized street sweepers can remove significant amounts of contaminants
from dry paved surfaces. In experiments few passes of these sweepers typically
removed more than 99 percent of the contaminant. Mechanical street sweepers
have a realtively high rate of cleaning, e.g., a few thousand square feet per
minute per pass. Again, in a large-scale emergency where the primary concern
is to reduce the gross hazard as quickly as possible, street sweeping may be a
viable technique. However, in cases where it is less critical, street sweepers
probably would be a less acceptable alternative due to resuspension of paticu-
late materials. Dust can be kept down to some extent by sprinkling. In any
event, mechanized street sweepers can only be used on large paved areas where
access is available. (Street sweepers can also be used, with limited effective-
ness, on open areas of frozen ground.) Hand brooms have some limited effective-
ness for sweeping roofs.
Environmental impact from sweeping is limited to particulate resuspension.
(8-4) Mechanized Street Flushing
As is the case with mechanized street sweepers, street flushers have the
advantage of a high rate of areal coverage, e.g., a few thousand square feet
per minute per pass. A single pass typically removes 90 to 99 .percent of the
contaminant and a second pass typically results in more than 99 percent removal
of the original amount of contaminant. Thus mechanized street flushers appear
9-16
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to be as effective as firehosing and faster. However, their use is limited
to streets or other large paved areas.
Using mechanized street flushers-poses the potential problem of flushing
contaminants into the storm sewer system and thence into the sewage treatment
plant or some other discharge point. If this is not desired, the runoff must
be captured. Otherwise, there are no significant adverse ecological effects.
(8-5) Surface Removal Teohni-ques
Firehosing, flushing with water, sweeping, and vacuuming do not usually
have any significant effect on the building or paving surfaces which are being
decontaminated. Another class of cleanup techniques for hard surfaces consists
of removal of some of the surface to which the contamination adheres. Surface
removal techniques would likely be applied only for residual contamination
which cannot be removed by the nondestructive techniques. These techniques
include removal of contaminated surfaces by chemicals, scraping or wirebrush-
ing, sandblasting, or other abrasive techniques. Sandblasting, while very
effective in removing contaminants from hard surfaces, poses the hazard of
suspending contaminants in air unless preventive measures are taken.
Using surface removal techniques on artificial surfaces poses no signif-
icant ecological problems. Paint stripping requires the use of caustic chem-
icals, but the sludge will have to be collected in any case. Sandblasting is
not a viable technique unless measures are taken to contain the particulate
dust which would otherwise be resuspended in the air.
(8-6) Other Removal Methods
Other methods for removing contaminants from hard surfaces, primarily
small areas, include wiping with tac-cloths or similar material, applying
strippable films, and perhaps even ultrasonic cleaning. Strippable films and
wiping are probably only effective on very smooth surfaces such as furniture
tops or automobiles, but may have some application. Ultrasonic cleaning poses
the possible hazard of resuspending small particulates.
(8-7) Containment
Containment techniques may be used (1) to temporarily immobilize contam-
inants onto hard surfaces while cleanup measures are being formulated, (2) as
9-17
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a long-terra measure to seal off a contaminant from being a hazard, or (3) as
a final step to seal off any residual radiation after cleanup measures have
been completed. Containment techniques using an impervious sealant are 100
percent effective for reducing the hazard from alpha emitters since the ex-
ternal hazard from these radionuclides is negligible. However, the sealant
must be maintained for as long as the underlying surface might be a hazard,
to avoid a hazard when the sealant weathers or otherwise deteriorates. Paint,
tar, oils, and liquid asphalts are the commonly known containment materials,
based on 1950s and 1960s technology that was primarily concerned with nuclear
weapon fallout. Many of the soil stabilizers shown in Table A-l (Appendix A)
could also be used to temporarily contain contaminants.
If the containment is temporary, solvents or other techniques are needed
to remove the sealant to permit cleanup of the surface. (The sealant itself
may be employed as a means of removing the contamination by "locking onto"
the contaminant so that it is removed with the sealant.)
Applying techniques for containing contaminants in place on impervious
surfaces and then perhaps removing the containing material may be costly in
monetary terms and disruptive to human activities, but otherwise there is no
significant effect on the environment.
9.5 RECOVERY AFTER CLEANUP
Most of the cleanup techniques for urban/suburban areas will not cause
significant long-term ecological damage. Within a matter of months to a year
or two following the destruction of vegetation, lawns and small plants could
be reestablished. The only long-term impact would be the lack of large trees
and shrubs, if they had to be removed.
Many of the treatments involving earthmoving, destruction of vegetation,
or soil stabilization are commonly used in urban/suburban areas when preparing
land for development.
9.6 QUANTITATIVE ASSESSMENT OF CLEANUP IMPACTS
Table 9-1 is an estimate of the relative impact on the ecology of an
urban/suburban area as a result of applying the cleanup treatments described
9-18
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9-19
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in Section 9.4. The impacts are rated on a scale of 0 (no impact) to 100
(greatest impact) for the various treatments and the size of the area disturbed.
In the urban/suburban case impact is assumed to be directly proportional
to the area affected, because there are relatively few wild animals, except
those considered pests, to be displaced and the vegetation will be replaced
rather than permitted to reestablish naturally. Therefore, the impact on a
10-km2 area is assumed to be 1,000 times greater than the impact on the 0.01-
km2 area. This is" in contrast to undeveloped land types where impact is not
assumed to be directly proportional to the size of the area.
Treatments 4-1 and 4-2, stabilization with a hard surface, are judged to
be the most severe with a rating of 100.* Not only will these treatments re-
sult in killing all vegetation and obviating most social and economic uses,
but the surface remains in place for a significant time period, in contrast
to the other treatments where the area can be restored to near its original
condition within a few years.
Treatment 1-3, stumping and grubbing, and treatments 2-2, 2-5, and 2-8,
removing the shallow root zone, are rated next in severity with a rating of
75. These treatments will result in the death of essentially all vegetation.
Treatment 1-2, clear cut vegetation, is rated less damaging at 70 because some
of the vegetation can propagate from existing root systems.
Treatments 1-7 and 1-8, soil cover; treatment 1-6, deep plowing; and
treatments 2-1, 2-4, and 2-7, removing the plow layer, are judged roughly
equivalent with a rating of 50. Most trees will not be seriously damaged or
killed by these treatments, but all other vegetation will be destroyed. Treat-
ments 1-4, 2-3, and 2-6, scraping and grading, and treatment 1-5, shallow plow-
ing, are rated approximately equal with a rating of 25. Damage is to a lesser
degree than with removal of the plow layer.
Treatments 3-1, 3-2, and 3-3, barriers to exclude people and animals,
are assigned impact ratings of 10. Presumably the barriers are for a short
time period. Application of sewage sludge may pose some problems in social
unacceptability.
*A11 ratings are for a 10 square km area.
9-20
-------
Treatment 1-1, chemical stabilization, and treatments 8-1 through 8-7,
treatment for artificial surfaces, are judged to have negligible environmental
impact provided they are done correctly so that the contaminant is either con-
tained or controlled in a desirable manner.
9.7 CONCLUSIONS
Although it may be very expensive and socially disruptive to clean up
contamination from a large urban/suburban area, significant adverse effects
on the natural ecology are short term. Many of the treatments are used during
normal construction activities that occur in urban/suburban areas. Within a
matter of months to a year or two following cleanup, lawns and small plants
will be reestablished (except in the case of hard-surface stabilization).
The only change will be the lack of large trees and shrubs if they have been
removed. The consequences of not effectively cleaning up the contaminant
(e.g., human health) may be more significant than concern for the environ-
mental impact of cleanup treatments. Thus, environmental impacts must be
secondary to selecting the most effective treatment or treatments. The resid-
ual contamination must be reduced to some acceptably low level; if this neces-
sitates the complete destruction of all vegetation, that impact must be ac-
cepted. In this context there are no treatments that are'unacceptable, ex-
cept natural rehabilitation. Circumstances will dictate the most desirable
treatments for a particular situation.
9.8 URBAN/SUBURBAN LAND AREAS REFERENCES
1. Bennett, C.B., and W.L. Owen. Planning Radiological Reclamation of Test
Facilities at Kwajalein Contaminated by Plutonium, Volume IIRadiologi-
cal Reclamation Procedures. U.S. Naval Radiological Defense Laboratory,
San Francisco, CA 94135, Report USNRDL-TR-67-68 (AD 820010), 29 May 1967.
(Official Use Only)
2. Cobb, LTC F.C., and LTC R.L. Van Hemert. USAF, Source Book on Plutonium
and its Decontamination. Field Command, Defense Nuclear Agency, Technol-
ogy and Analysis Directorate, Kirtland Air Force Base NM 87115, 24 Sep-
tember 1973.
3. National Academy of Sciences, National Research Council. The Behavior of
Radioactive Fallout in Soils and Plants. Washington, D.C., Publication
1092, 1963.
4. Office of Environmental Quality (in cooperation with Geotechnical Consul-
tants, Inc.). Impact of Urbanization on Recharge Potential of the Goleta
Groundwater Basin. Prepared for the County of Santa Barbara, Santa Barbara,
California, March 1976 (revised July 1976).
9-21
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Owen, W.L., F.K. Kawahara, and L.L. Wiltshire. Radiological Recalamation
Performance Summary, Volume 1-Performance Test Data Compilation. U.S.
Naval Radiological Defense Laboratory, San Francisco, CA 94135, Report
USNRDL-TR-967, OCD Work Unit No. 3114A, 13 October 1965.
U.S. Bureau of the Census. County and City Data Book-1972 (A Statistical
Abstract Supplement). U.S. Government Printing Office, Washington, D.C.,
1973.
9-22
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PART III
WILDLIFE
CHAPTER 10, WILDLIFE
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CHAPTER 10
WILDLIFE
10.1 OVERVIEW
A large amount of information must be integrated to describe which
impacts to wildlife will occur in particular situations. For example,
the time span over which impacts occur, the type of disturbance, land
area, land types, vegetation component, wildlife component, and wild-
life ecology all must be considered. In addition, feedback and inter-
actions among these factors must be considered. So that this informa-
tion can be more easily dealt with, several simplifications will be
made. These include a standardization of the above variables. This is
followed by a general discussion of characteristics which relate to im-
pacts on each wildlife group of birds and mammals. This discussion is
made first for immediate impacts, and then repeated for long-term effects.
The term "ecological impact" implies two basic actions. First,
there is some disturbance to an area. Second, there is a reaction
(impact) which results from the disturbance. Of interest are those im-
pacts caused by human disturbance which result in a change in population
numbers and/or species content of an area. Since impacts can be subtle
or gross, only those impacts which are quantitatively measurable in the
field are considered.
The impact on an area usually has short-term and long-term com-
ponents. The short-term component can be measured immediately following
the disturbance. The long-term component must be examined for duration
as well as magnitude. Some criterion is needed to decide how much change
is required to "recover" the disturbed areat (i.e., the quality of the
recovery), and how long the recovery will take. However, the product of
the recovery can vary. If the land and vegetation return to a different
condition, a new wildlife community may become established which is very
10-1
-------
different from the original one. Naturally, the rate of recovery will
vary among land types and climates.
This raises the question of the location of the end point of the im-
pact. Since "impact" is defined as a change, the end point is where
changes become too small to measure quantitatively. However, natural en-
vironmental processes are dynamic; that is, they fluctuate constantly.
When this fluctuation is slow the ecosystem is considered stable, or in
equilibrium. Likewise, wildlife communities are only relatively stable.
Thus it is both unreasonable and impossible to restore a community to its
exact original condition. The practical solution is to restore the origi-
nal natural conditions in land and vegetation as nearly as possible, and
simulate recolonization of wildlife. A new, but somewhat different, wild-
life community will become established in a dynamic equilibrium with the
new and somewhat different habitat.
A broad range of human disturbances can result from the treatment of
hazardous material spills. The least significant disturbance is probably
surface scraping of a thin layer of ground. The impact of this to wild-
life might be unmeasurable. Probably the greatest impact would result
from defoliation of plant life, followed by covering the soil surface
with cement or some other mechanical stabilizer. If done on the maximum
area size, this treatment would cause immediate local extinction or emi-
gration of the majority, if not all, of the wildlife in the area. It
might also cause abnormally high population densities in areas contiguous
to the treated area due to emigration.
In order to evaluate the impact of treatment disturbance in the dif-
ferent land types, a reference standard for "disturbance" is needed.
This standard will be taken as the most drastic disturbance as described
above. In this case the immediate impact is that which follows the
treatment. The recovery phase is defined as following the erosion or
removal of the ground covering. For simplicity this is assumed to be
removed at one point in time. Less drastic treatments can be evaluated
across the land types by using the same rationale applied on a lesser
scale.
10-2
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The impact to the local wildlife of a land treatment is heavily
dependent on the land area that is disturbed. The areas of concern
range from 0.01 km to 10 km2. These areas can be envisioned as
squares: the smaller is 100 meters on a side and the larger is approxi-
mately 3.16 km on a side. Since a point-to-point discussion of this
entire size range is impractical, these end points plus a midpoint area
of 1 km2 (1 km or 1000 meters on a side) will be discussed. An addition-
al area 100 km2 is also included because it approaches an upper "end
point", at which a measurable impact can be expected for almost all wild-
life species. These should typify the desired range of areas.
A wide variation in habitats exists for each land type under con-
sideration. Again, some simplification is needed in order to organize
the wide range of impacts. This can be done by using a procedure which
has proved successful in plant ecology; i.e., describing a typical
habitat type within each land type. The following is an adaptation of
Whittaker's system for this purpose:
Deserts include a wide range of communities. It is appropriate to
note that two types of desert occur in the United States: (1) warm-
temperate deserts, represented by the widespread creosote bush com-
munities and the floristically rich uplands of the Chihuahuan and
Sonoran deserts, and (2) cool-temperate desert scrub, including the
sagebrush semidesert of the Great Ba.sin. The floras of both these
desert types share a scrubby habitat. Also, in both a lack of
moisture is critical to the maintenance of the various habitats.
Thus deserts can be typified as those areas of extremely low
annual rainfall.
Prairie (or grassland) includes the great prairies, plains, and
desert grasslands of the United States. Despite reduction of
vegetation structure to a single major horizontal stratum, plant
species diversity in grasslands can be high compared with most
forests. These are areas of relatively low rainfall (but more
than deserts) and experience a broad range in mild temperatures.
10-3
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Deciduous forests grow in modera,tely humid, continental, tem-
perate zone climates, with summer rainfall and severe winters.
Broad-leaved deciduous trees (oak, beech, maple, ash, basswood,
etc.) are dominant in forests with trees 30 to 40 meters tall.
Animal life of temperate deciduous forests is abundant but
varies according to the season; diversity of plant and animal
species is moderately low to moderately high. Deciduous for-
ests are extensively developed in the eastern United States.
C Coniferous (evergreen) forests occur in varied temperate zone.
circumstances. Extensive needle-leaved evergreen forests occur
in continental climates of the western United States, and in
places where soil characteristics, or fire frequency, or both,
favor pines over broad-leaved trees in the milder climate of
the eastern United States. Coniferous forests are dominated
by pine, fir, spruce, etc. A special type of coniferous for-
est is the subarctic-subalpine needle-leaved forest of the
cold edge of the climatic range of forests. These areas exist
in the northern part of North America and exist to the south
at higher elevations in mountain areas.
a Mountain areas can be categorized as vertical extensions of
other land types, as well as those areas which are exclusively
non-forested aeolian or alpine regions. Aeolian mountain areas
are almost never the sole habitat of animals using them. There-
fore, wildlife responses detailed in the discussions of the
other land types are applicable. When mountain areas are ex-
tensive, they may be very similar to tundra, and that land
type should be referred to. The reader is referred to these
specific sections for treatment of the wildlife of mountain
habitats.
Turidras are the treeless arctic plains. The vegetation forms
are varied and there are often complex patterns of dominance by
dwarf-shrubs, sedges and gresses, and mosses and lichens. In.
many tundras the deep layers of the soil are permanently frozen,
and only the surface soil is thawed and becomes biologically
10-4
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active during the summer. In many of these communities, re-
peated freezing and thawing of the soil separates rocks from
finer soil materials and arranges the rocks in parallel strips,
or in networks with polygonal cells; striking internal pattern-
ing of the plant communities in relation to soil differences
results. Vegetation cover decreases toward the sparse lichen
communities, rock fields and ice of high elevations.
Coastal inter-tidal marshland can be salt-water or estuarine.
These areas, especially salt-water marshes, are extremely rich
energy sources. Like prairies, they are limited in vertical
structure. The plants of salt-water marshes are herb and forb-
like. Marshes are not usually extensive, but are rather patchy in
occurrence, or form a narrow band along a lake or coast.
Agriculture is unique, being the substitution of a usually monotypic
community for one or more natural plant communities. Agriculture
is practiced in nearly all climates, although many hot and cold
areas are not yet occupied fully. Agriculture can be characterized
as managed fields with generally low vegetation (under 12 feet)
dominated by 1 or 2 cultivated plant species. The most common
secondary species are those generally considered "weeds," i.e.,
introduced herbs. Agriculture is extremely widespread .in the
United States except where climate and/or terrain are exceed-
ingly harsh.
Suburban land types are best described as those areas which make
up areas of human habitation. Like agriculture, these areas are
extremely widespread. The numerous roads and human activity
associated with this land type severely restrict the type of
wildlife which can exist. The human dwellings are usually asso-
ciated with exotic introduced plants and/or weedy species. As
with agriculture, this land type is an imposition of a new com-
munity upon a previous and older natural community. This favors
a low number of species, but with high densities.
10-5
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Some species have extremely low population numbers and must be
examined individually to assess potential cleanup impact. Identification
of these sensitive species can be obtained from Federal and State lists
5 22
of threatened and endangered species. ' State lists are to be pre-
ferred since they often include recent information on steps which have
been taken to protect the species. State agencies also usually have
recent literature and staff knowledge which may bear on the problem.
If a habitat which supports such, a species is disturbed, several
things may be done to speed up the recovery phase for the animal. This
may be necessary for disturbances to rare species. For example, the
Trumpeter Swan was close to extinction (about 65 birds) in 1935. Areas
where these birds breed were designated as off-limits to hunters. Also,
additional food was made available at these sites in winter. Finally,
the birds were introduced to other potential breeding sites. Due to
these steps, the population had recovered (to about 915 in the U.S.)
by 1976. Other direct steps can be taken to accelerate faunal recovery,
that is, increasing the rate of vegetative recovery.
Faunal recovery is strictly related to the recovery of the vegeta-
tion. The fauna cannot normally respond before the vegetation has
done so. There are three components of the vegetation which are particu-
larly important to animals. The first is the plant species which colo-
nize a disturbed area. These are of especial importance to the herbivores.
The other two components are vegetative height and density, i.e., the
vegetational structure (see Emlen for an exception). All three of the
above components will change over time in the successional processes of
the vegetation. Faunal recovery must, to some degree, be an upward pro-
cess in terras of the food chain. Carnivores cannot colonize an area
until their prey is available. Since abundances may increase slowly by
reproduction, or quickly by invasion, it is difficult to predict a re-
covery for animals at the top of the food chain. However, these effects
can be mitigated for those predators which can utilize a wide variety of
prey, so that food can be caught during several stages of the vegetation
succession.
10-6
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Once vegetational succession has produced a new climax community,
the more similar the new vegetation is to the original, the more similar
the new fauna should be to the original fauna. This does not require a
vegetation be established that is identical to the original. All that
should be required is an approximation of the original vegetation which
provi-es the same resource value in terms of food and structure. The
critical questions to wildlife restoration are the "quality" and duration
of vegetation recovery.
25
Plant succession has been well studied by plant ecologists but
the faunal community succession process which occurs in nature has not
been studied as much. As plant succession occurs, multiple feedbacks
are possibly among and within plants and animals (not to mention soil
content changes, ground-level temperature regime cahnges, etc.). The
network can be extremely complicated. However, faunal changes can be
closely examined with respect to plant succession, and different animal
species will show greater or lesser facility for recovery.
In most cases some species which were not among the original fauna
of the area will move in during part of the vegetative recovery. These
species will probably move out of the disturbed area as the habitat
changes toward one more similar to the original one. This causes a
decrease in species diversity as the climax of the faunal succession is
reached. The pattern of plant species diversity in succession emerges
as a rise from the start of recovery to a pre-climax peak, and then a
leveling off at a slightly lower level as the dynamic equilibrium of
Q
the climax ensues.
The few studies that have been done on faunal succession draw
evidence from the fossil record and emphasize evolutionary (very long
term) time. Of concern here is ecological, not geological, time, i.e.,
a relatively short period of time during which succession may occur,
19
but evolution cannot. Thus this discussion emphasizes the responses
which are expected from individual species, rather than faunal succession.
10-7
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10.2 EFFECTS ON BIRDS
Much information must be integrated in an examination of impacts on
birds. Unfortunately, much of this information dealj with particular
species, making generalizations difficult. However, in order to understand
impacts on birds some generalization is necessary, as a discussion of each
species individually is impractical. Therefore, impacts are described
for groupings of birds which share some general life history and/or feed-
ing characteristics, or are closely related. These groupings are examined
for short-term effects (immediate impacts) and long-term effects (recovery
phase), then each land type is examined for specific short- and long-term
effects.
Measurement of a change in the numbers, or population, of a bird
species is not an easy or unambiguous process. First the term "popula-
tion" must be defined in some way which is not necessarily land-area de-
pendent. Once this is done a census method must be picked from those
which have been shown to be accurate. ' But even after a standard for
measurement is chosen, and the data taken, it is still necessary to put
the measured impact into context. What is really desired is the effect
on the local species. This effect can only be ascertained by having a
local wildlife expert analyze the data for the disturbed area and gener-
alize the measured impact into an impact value based on local abundances.
10.2.1 Short-Term Effects
In general, a disturbance to an area will be much more serious to
permanent residents than to migrators. This is especially true where the
disturbed area is along a migration route. If .adequate alternative routes
of migration are available there may be no quantitative impact. Where
only one route is possible, if food is not taken from the area by the
migrants the impact may be very slight. However, once alternative routes
of travel are used, it may prove very difficult to reintroduce the dis-
turbed area as a part of the migration route. This will depend on how
many of the migrators are lost, whether the alternative route is really
as adequate as the original, and whether the route is learned or innately
known. The slow rate of reintroduction of residents and migrants who
10-8
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feed on an area should be slightly greater for the more mobile migrant
populations.
The seasonality of a disturbance is of extreme importance to birds.
In general, disturbances in the spring will have a much greater initial
impact than those in other seasons for two principal reasons. The first
is that the breeding season occurs in the spring for most American bird
24
species. The second reason is that the spring is also a very critical
time of growth for plants. Naturally, a disturbance in another season
can affect spring conditions; however, most bird species can react to ad-
verse habitat conditions before breeding occurs. For example, they may
nest elsewhere, or at least nest in lower densities.
Among most birds, a disturbance to the breeding grounds is generally
more serious than an equal disturbance to the wintering range. Many
birds hold territories during the breeding season, but form flocks during
the winter. Flocks can lose members to other flocks when food is scarce,
or can remain cohesive at a small cost to each of the members. This is
not true of the destruction of breeding territories. The area lost here
will almost always result in a lower number of breeders. Thus an immediate
impact is more likely to be of greater magnitude when breeding habitats
are destroyed.
Some birds feed away from the nesting area or hold feeding terri-
tories around the nesting area. The nesting can be done in tightly
packed colonies or, when food is taken at some distance away from the
area of the nest, in looser aggregations. Those species which hold
feeding-nesting territories are much more spaced out. Obviously, dis-
turbance of a colonial breeding area will affect more birds than the
same area disturbance to a feeding-nesting territory.
A strong correlation between body size and feeding-nesting terri-
tory size has been shown for many bird species. Thus a disturbance
of a given-sized area will usually affect more members of small species
2 ~
than larger ones. The loss of an area of 0.01 km can cause the loss
of six song sparrows' feeding-nesting territories. However, the same
area is only 0.25 percent of a red-tailed hawk's feeding-nesting terri-
2
tory. A 1 Ion area is roughly a quarter of the size of a red-tailed hawk's
10-9
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territory, and is a reasonably large area in terms of most smaller birds.
2
In any case, there can be little doubt that the loss of an area of 100 km
from the breeding range of almost any species will have a measurable impact.
10.2.2 Long-Term Effects
Birds respond very quickly to habitat changes due to their high mo-
bility. When the proper conditions prevail, bird dispersal is facilitated.
However, different life histories will cause some differences. Size dif-
ferences will also be critical, as larger birds can expand their terri-
tories more easily than smaller birds. The following differences also
hold for some broad groups of birds.
In general, migrators being more mobile than permanent residents,
will colonize areas more quickly. However, where migration routes and
summer/winter grounds do not border on a suitable area, colonization can
be much slower. Permanent residents have an advantage in being able to
establish themselves at a time when migrators are not present. Some
species, such as the Trumpeter Swan, can migrate or not, depending upon
food resources, and will recover accordingly.
The area used for breeding grounds by migrators may spread at a
somewhat more rapid rate than that of permanent residents. However, the
choice of wintering grounds is likely to be even more flexible. The par-
ticular migratory species which uses an area will probably depend on the
successional stage of the vegetation. Some species of migrators may
colonize new breeding habitats more quickly than others. These effects
may not have corresponding effects on the wintering range except for a
change in the number of young present. However, since the breeding ter-
ritories must be reestablished each year, complicated variable changes in
the species pattern on the breeding grounds may occur. The damping of
these changes may extend beyond the vegetative recovery phase.
Feeding flocks are apt to be rapid colonizers since their foraging
method entails high mobility and allows them to exploit a thinly spread
f\
resource. Birds with feeding territories usually colonize from a
"leading edge" of the population. This movement is necessarily slower.
The recruitment into flocks may be somewhat slower, by reproduction, so
10-10
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that even though a flock may use an area, the vegetation is not exploited
to as great an extent as by the slower colonizing territorial species.
Competition among species may be important to recolonization. The
first bird species to colonize an area can move in unopposed. However,
the species which replace it in faunal succession may have to compete
with the established species in the area. The net effect is one of pro-
longing the faunal successional process. Just how long the succession
takes will therefore be somewhat dependent on the intensity and duration
of the total amount of interspecies competition that occurs.
The following "trophic/niche" groups of birds contain families whose
species share trophic level and lifestyle characteristics. Naturally,
some families have members in more than one group. These families are
divided into the respective groups in the following discussion. Examples
of typical families are:
1. Large carnivorous birds: American vultures, buteo hawks
(Accipiter family), and large owls..
2. Medium-sized carnivorous birds: medium-sized falcons, kites
3.
(Accipiter family), and medium-sized owls.
Small carnivorous birds: kestrels (Falcon family), shrikes,
and small owls. ;
Large primarily herbivorous birds: grouse, pheasants, and
turkeys.
Medium-sized primarily herbivorous birds: mockingbirds,
thrashers, thrushes, blackbirds, and quail (Pheasant family).
Small primarily herbivorous birds: hummingbirds, titmice,
and sparrows (i.e., almost all of the Fringillid family).
Medium-sized insectivorous birds: woodpeckers, tyrant fly-
catchers, and swallows.
8.
9.
Small insectivorous birds:
All sized truly omnivorous birds:
gulls.
wrens, vireos, and wood warblers.
ducks, jays, crows, and
10. All sized aquatic feeder birds: plovers, sandpipers, and
phalaropes.
Some land types take longer to restore than others. This can be
considered the sensitivity of the land type to disturbance. The reasons
for sensitivity can be the magnitude of the disturbance, the amount of
vegetative structure, and climatic conditions present, the length of the
10-11
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growing season, the soil types present, and other, factors. These many
factors are integrated in the analysis of recovery of vegetation and land
types over time. Here, differences in the responses of the bird faunas
to the immediate disturbance and the subsequent recovery of the different
land types are described.
Table 10-1 gives examples of bird species from each trophic/niche
group in each land type which yield a measurable impact if the maximum
disturbance has been made on the specified (or larger) land areas. The
table uses ;area size differences among groups of birds to show how the
groups are affected. This should not be equated with the qualitative
"importance" of a species. For example, more robins would be lost than
red-tailed hawks for a disturbance to a habitat for both. But the hawks
may be more "important" than the robins in terms of numbers in existence
or aesthetics.
The table assumes that at least ten breeding territories must be
lost to a species before impact can be measured. No literature is
available upon which to base an estimate of the number of breeding pairs
which must be removed from a habitat to yield a measurable impact,
The figure of ten was chosen because it represents a number at which
large and/or uncommon species will begin to show a measurable impact.
The figure of ten is thus a minimum. The real figure should be higher
for many species. However, lower figures should seldom occur. A
further assumption is made that measurement is solely on a local scale.
Bird breeding territory area is used because the breeding grounds are
of the greatest immediate importance to the multiplication (reproduction)
of most populations. Bird breeding territories may vary with food
resources in some cases. However, breeding area should generally be
less variable than any other type of defended area used by individual
birds.
10.2.2.1 Deserts
The imp'act of a disturbance in deserts will be greatest for small
herbivores, medium sized insectivores, and all carnivorous birds. An
added impact on carnivores is the loss of a great diversity of reptilian
10-12
-------
Table 10-1.
Examples of bird species impacted by maximum disturbance
to specified types arid sizes of land areas.
MAJOR GROUPS
1. LAND TYPE
DESERT
Large Carnivores
Medium Carnivores
Small Carnivores
Small Herbivores
Medium Insectivores
PRAIRIE
Large Carnivores
Medium Carnivores
Small Carnivores
Large Herbivores
Omnivores
DECIDUOUS FOREST
Large Herbivores
Medium Herbivores
Smal 1 Herbi vores
Medium Insectivores
Small Insectivores
CONIFEROUS FOREST
Small Herbivores
Medium Insectivores
Small Insectivores
TUNDtfA
large Herbivores
Aquatic Feeders
COASTAL INTER-TIDAL
Medium Herbivores
Small Herbivores
Medium Insectivores
Small Insectivores
Omni tore:
Aquatic Feeders
2. LAND USES
AGRICULTURE
Large Carnivores
Medium Carnivores
Small Carnivores
Medium Herbivores
Small Herbivores
SUBURBAN
Medium Herbivores
Small Herbivores
Medium Insectivores
Omnivores
SIZE fir LAND AREA
0.01 km2
Franklin's gull
Least flycatcher
White-eyed vireo
Song sparrow
Bank swal low
Robi n
House sparrow
Cardinal6
Song sparrow
Cliff swallow
1 km2
Loggerhead shrike
Black-throated s,parrow
Ash-throated flycatcher
Greater prairie chicken
Common crow
Ruffled grouse
Baltimore oriole
Black-capped chickadee
Acorn woodpecker
Tennessee warbler
Pine siskin
Western flycatcher
Olive warbler
Willow ptarmigan
Whimbrel
Yellow-headed blackbird
Marsh wrens
Tree swallow
Yellow- throat
Pintail
Willet
Loggerhead shrike
Mockingbird
Chipping sparrow
Mockingbird
House finch
Black phoebe
Blue jay
10 km2
Elf owl
Sparrow hawk
Barn owl
Burrowing owl
Sparrow hawk
100 km2
Red-tailed hawk-
Prairie falcon
Golden eagle
Prairie falcon
Common raven
Territory sizes takjn from Welty and Schoener or estimated from sizes of similar species.
Species nomenclature follows Peterson,1 where scientific name;, are also qiven.
Member of the sparrow family.
10-13
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prey. Large- and medium-sized herbivores occasionally occur in desert,
usually on its fringes, as is true of most small insectivores and omni-
vores which live in or near deserts. The desert itself is not the sole
habitat of these species, and impacts are thus lessened.
Resident desert bird faunas should contain a high proportion of
specialist species which have low population densities. These birds
will be extremely slow to respond to most recovery situations. The
generalist species which do occur in desert can usually be expected to
expand their numbers beyond the normal level upon colonizing a disturbed
area. In this particular habitat the presence of generalists in abundance
will probably further retard reeolonization of specialists to a measurable
degree. Management may be extremely useful in this unusual case.
10.2.2.2 Prairies--
Prairies are remarkable for having a distinct lack of vegetative
height. Large herbivores and omnivores are the groups most impacted by
a disturbance here. These are closely followed by carnivores of all
sizes. Carnivores feed not only on bird prey on prairies, but also on
the high populations of mammals which are common herbivores. Medium-
sized and small herbivores, while not as diverse on prairies as in other
land types, may still be very abundant. Once again, as smaller herbi-
vore* are examined; the impact of a disturbance is usually magnified.
Medium-sized insectivores often feed over prairie, but seldom nest there.
Thus the impact to this group should be reduced. Even less impact should
be seen in aquatic feeders, who use prairie areas as stopping-feeding
sites during migration.
Prairies contain an imbalance of generalist species, mainly due to
the high carnivore and omnivore diversity. Thus the recoveries of prairie
bird faunas are largely secondary effects, since both the above groups
depend to some extent on animal prey. Carnivore recovery may lag far
behind the vegetative recovery. The omnivores, on the other hand, are
generalists and will recover more quickly. Much more omnivore feeding
than breeding occurs in prairie areas, also facilitating the return of
this group. The remaining breeding species are herbivores which are
10-14
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generally mobile species for their size. They will recover relatively
quickly.
10.2.2.3 Deciduous Forests--
Deciduous forests have good diversity and abundance of herbivores
and insectivores of all sizes. These groups will bear the major impact
of a disturbance in most cases. Here also large and medium sized
carnivores will occur mainly where there are breaks in the forest, and
be impacted in proportion to the disturbed area of the forest breaks.
Small carnivores and omnivores, while lacking in diversity in these
forests, may be locally abundant. These last two groups should be wide-
spread where they occur, thus lessening potential .impacts upon them.
Deciduous forests are generally richer in bird fauna than coniferous
forests and relatively higher proportions of specialist species occur.
Thus, the faunal recovery will take longer in deciduous forests. However,
these forests also have the advantage of being extensive, so colonists
are available. These bird faunas may be extremely sensitive to dis-
turbance, since the specialists may have a more "patchy" distribution
as well as lower population densities. Because of their size and lesser
mobility, the smaller herbivores and insectivores may be very slow in
recolonization.
10.2.2.4 Coniferous Forests
The disturbance of coniferous forests should impact small herbivores
and insectivores of all sizes to the greatest degree. A great abundance
and diversity of these groups occur here. In breaks in the forest, large
and medium-sized carnivores occur and will be impacted where the breaks
are disturbed. Coniferous forest supports relatively less small carni-
vores, large and medium-sized herbivores, and omnivore diversity. Where
these groups occur, however, they may do so in abundance, and thus be
impacted. Again, these last groups (except the small carnivores) are
more likely to occur in breaks in the forest.
Coniferous forests tend to contain a relatively limited fauna
compared with the other land types. However, the number of specialists
10-15
-------
and generalists is usually evenly balanced. Naturally, the generalists
will respond to vegetative recovery more quickly. However, since coni-
ferous forests are generally extensive, surrounding forest areas are
almost always present to provide colonists. As vegetative recovery nears
completion, more and more specialists will move in to supplement the
labile generalists.
10.2.2,5 Aeolian Mountain Peaks
A disturbance to a mountain-alpine habitat will affect only those
few birds which have adapted to this barren land type. An example of
one of the few species of birds which are specialized for this type of
habitat are the Ptarmigans (in the Grouse family). During winter,
alpine birds move to lower elevations, and live in other land types.
Herbivores of all sizes will receive the greatest impact from an environ-
mental disturbance, because of the disruption in their food supply.
Large and medium sized carnivores may use alpine areas for hunting and
breeding, but carnivores will be impacted to a lesser degree due to
their ability to move into other types of habitat below treeline. The
other trophic/niche bird groups should rarely occur in alpine areas and
thus receive no impact from a disturbance to it.
Due to specialization of herbivorous alpine birds and the patchy
and disconnected nature of the alpine habitat, recovery from a disturbance
will be an arduous process. Mountains are to a large extent "islands"
25
separated by a "sea" of forest; therefore, recolonization of alpine
areas may only be possible from within the original population. Many
alpine birds winter in nearby forests, thus, the more isolated a mountain
is, the longer it will take for colonists from other mountains to arrive.
Since large and medium carnivores of alpine areas are generalists they
will recover more quickly. However, they will only be able to recolonize
alpine areas as their prey also recolonizes.
10.2.2.6 Tundra Areas
The tundra is commonly only the summer range of species which breed
there. However, a group of large herbivores (ptarmigans) are resident
on tundra, and thus are subject to the greatest impact of any disturbance.
10-16
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Impact on the principal'summer breeding migrants, the aquatic feeders, is
also very serious. Many of these birds nest in aggregation, so impacts
are either drastic or considerably dampened, depending on the location
of the disturbance. A few omnivores (gull species) share this charac-
teristic and nest on or near tundra. Two large carnivores (the snowy
owl and gyrfalcon) feed on tundra and breed nearby. These last two birds
have large ranges which help to mitigate any impact upon them.
Tundra bird faunas are largely migratory, so that bird recovery can
be relatively rapid. However, since the bulk of breeding for the aquatic
feeders occurs here, the recovery of breeding populations must generally
follow the recovery of food resources. The yearly freezing of the. ground
does not encourage invertebrates, so that more vegetation must be eaten.
The only resident birds, the large herbivorous ptarmigans, are also
closely tied to vegetative recovery. Where tundra occurs it is usually
extensive, so that the bird fauna can recolonize an area easily.
10.2.2.7 Coastal Inter-Tidal Marshlands
OC
Marshlands are usually rich energy sources and therefore all non-
carnivorous groups except large herbivores are usually represented.
The small insectivores and aquatic feeders are especially noticeable,
the former even more so in fresh-water marshlands. Since those species
which live in marshes are pften restricted to it, they will be impacted
severely by a disturbance. Large- and medium-sized carnivores which
frequent marshes usually include other areas in their hunting range,
or can easily do so. They are therefore less impacted. Many aquatic
feeders and omnivores use marshland as stopping and/or feeding places
during migration, and can be subjected to a lesser impact by changing
their migration routes.
Marshland bird species are generally very sensitive in terms of
faunal recovery. A very high relative proportion of specialists occurs
here. Their recovery is complicated by the patches in which this habitat
occurs. If the disturbance occurs over an entire patch of marshland,
recovery will be much slower than that expected for a disturbed area
within a patch. Thus, disturbed area size effects are especially
10-17
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important. Size effects will be greatly magnified for smaller birds, but
may have relatively little significance for the more mobile large- and
medium-sized carnivores.
10.2.3 Land Uses
10.2.3.1 Agricultural Areas--
Agricultural areas contain either breeding or feeding areas for
some members of all the trophic/niche groups except small insectivores.
However, the groups which are most impacted by disturbance of agriculture
are the medium and small herbivores and the carnivores of all sizes which
prey upon them. Large herbivores, medium insectivores, and omnivores are
more likely to feed on agricultural areas than to breed on them, and will
usually be less heavily impacted. Aquatic feeders are the least likely
group to be impacted since they occur only under special conditions
(excess water or ponds available). However, the impact on this group
increases if they can breed where an area is disturbed, again a special
case.
Agricultural land mainly supports generalist type bird species (i.e.,
those with a broad niche). This land type has not existed long enough for
specialists (birds with a narrow niche) to evolve necessary adaptations
for habitat specialization. The few specialists found here were pre-
adapted to some special feature of the agricultural habitat, and moved
in from other habitats. The result is an extremely resilient bird
fauna. This fauna will follow vegetative recovery very closely. Since
the species which occur in agricultural areas have dense populations,
dispersal from surrounding populations should send almost constant waves
of colonizers into the disturbed area.
A second alternative for agricultural land is to allow it to revert
to a state more similar to its preagricultural condition. In this case
the agricultural condition can be considered an additional disturbance
from which the avifauna must recover. In order to evaluate this particular
type of recovery, the sections dealing with the preagricultural land
type should be consulted. Differences from these land type recoveries
should not vary greatly due to the agricultural use of the land. The
10-13
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avifauna will change from an agricultural one to one commensurate with
the particular land type's plant succession.
10.2.3.2 Suburban Areas--
Suburban birds are generally birds which were preadapted to live
with humans. This implies a versatile lifestyle and a broad niche.
The groups which would be impacted (about equally) by a disturbance are
medium and small herbivores, medium-sized insectivores, and omnivores.
Groups which occur on the fringes of suburban areas are large carnivores,
large herbivores, small insectivores, and aquatic feeders. These will
be lightly impacted by a suburban disturbance, if at all.
Suburban bird faunas will also respond quickly in recovery of a
disturbed^area. Evidence for this is abundant in almost any spreading
city. A heavy proportion of generalists exists in most suburban habi-
9 12
tats. In addition, rather dense populations usually occur. These
areas are usually extensive or at least connected by corridors such as
freeways, construction sites, and/or rural human populations. Thus
colonization can be extreme during the recovery of the land type. In
addition, the recovery of many species need not be tied to vegetation
recovery since human dwellings provide structural diversity, and may
provide food.
As in the agricultural land use, the alternative of allowing the
suburban area to succeed to something more like the presuburban land
type exists.. However,-this process is complicated by the presence of
semipermanent structures (e.g., buildings) which increase bird habitat
heterogeneity. Without these structures a recovery similar to that
described in the appropriate land type is possible. However, if suburban
land is simply deserted, species which depend on suburban structures for
nesting and/or roosting (or cover from predators) will be favored.
These will generally not be the species commonly found in the presuburban
land type, and recovery will be retarded.
10-19
-------An error occurred while trying to OCR this image.
-------
7. Small omnivorous mammals: opossums, raccoons, ringtails,
and armadillos,
8. Insectivorous mammals: shrews and moles.
9. Flying mammals: two bat families.
10.3.1.1 Large Carnivores--
The primary immediate impact of a land disturbance to the large
carnivores should be negligible for the range of area sizes under
consideration. An area of 100 km is equivalent to only about one to
23
six mountain lion home ranges. Due to the wide ranging of these cats,
even a much larger disturbance would be very hard to measure in terms of
a change in population numbers. However, a secondary impact to this
animal is the loss of its prey. Again this effect is probably unmeasur-
able, since the deer they feed on are also large animals which are
widely distributed.
A slightly different situation exists for the other large carnivore
group, the wolves. Measurement of populations is extremely difficult,
even for the exceedingly common coyote. But in addition to measurement
problems, the grey (timber) wolf also forms packs. A disturbance to the
2
100 km area size could eliminate (from the area) a minimum size pack of
two, but this area is only about one-tenth the home range of a pack of
eight, so that primary impacts are impossible to assess. Some attempt
can be made to measure the change in pack size as an indication of impact,
but this is an extremely variable characteristic. Again, secondary im-
pacts are possible, but they are unlikely to be measurable. In all large
mammalian species emigration is the most likely cause of a drop in popu-
lation numbers after a disturbance.
1073.1.2 Medium-Sized Carnivores
Impacts on medium-sized carnivores are also difficult to measure,
Once again, the maximum disturbance to the maximum area size specified
2
(10 km ) for consideration should not produce a measurable impact in
most cases. The major prey of these carnivores, small herbivorous birds
and mammals, will be impacted at some area size, so that it may be
possible to get some measure of secondary impacts. The medium-sized
10-21
-------
carnivores are not as mobile as the large carnivores, so that it may
be possible to estimate an impact in some cases for a disturbed area
size of 100 km2.
10.3.1.3 Small Carnivores--
Many of the small carnivorous mammals are nocturnal, and thus
ignored by the majority of humans. However, it is in this group that
impacts in the larger area sizes can be measured. Weasels will have
measurable impacts where pre-cleanup prey densities are either high,
or are moderate but extensive in area. The other small carnivores
have larger home ranges in general and will be much harder to examine.
Secondary (prey) effects need not be examined for the groups which have
measurable impacts, since these effects are included in the change in
population size.
10.3.1.4 Large Herbivores
With the large herbivores size of the cleanup area again becomes
important. This difficulty is compounded by the ability of most large
herbivores to change home ranges seasonally (by migration). Local
changes in population size can probably be measured for disturbances
of the 100 km area size. However, these changes will probably be
measurable only immediately, for the high mobility of the larger herbi-
vores will soon reduce the possibility of finding many of the animals
which reside in the area, since they may leave it or perish. Animals
which successfully leave the area are not defined as being impacted.
10.3.1.'5 Small Herbivores--
Small herbivores are generally restricted to living their entire
lives in relatively small areas. The once popular idea that some small
13 14
mammal herbivores migrate has been thoroughly disproved. ' . These
animals are the most important United States mammals in terms of species
diversity and abundance. Their populations are easily sampled and moni-
tored in most cases. In addition, they form an important link between
primary producers (plants) and the carnivores which depend on them for
- , 11
food.
10-22
-------
Table 1Q-2 gives examples of small herbivorous mammal species that
occur in each land type which yield a measurable impact if the maximum
disturbance has been made on the specified (or larger) land areas and
types. The table indicates the kind of rodents and lagomorphs (the
rabbit order) which occur in the various land types and the general
disturbed area sizes which will produce impacts. The density of these
animals is relatively easy to measure.
Table 10-2 assumes that at least 12 to 15 home ranges must be lost
in an area before a local impact can be measured. As in the bird section,
this home range (area) amount is a minimum for measurable impact, except
for large and/or uncommon mammals. A special case of vole and lemming
home ranges being very small is somewhat counteracted by their excep-
tional movement abilities, so that a larger area must be disturbed for
these species than just 15 home ranges. Home range size usually varies
with changes in the density of food resources. Special cases in specific
locations are to be expected to vary from the predictions of the table.
It may be that small herbivore species can be used as indicators
to measure the effects of various disturbances. Small herbivore species
can change at the onset of a disturbance. As succession ensues, changes
in species composition and density can also occur.16 When the original
species distribution and density reoccur, an advanced stage of recovery
has probably been entered. A distinction must be made, however, between
those small rodent species considered "pests," or those deemed undesirable
by man, and species which are more beneficial to man's interests. Pest
species are generally exterminated periodically where they exist near
humans and impacts on them, although measurable, may not be of real
concern.
10.3.1.6 Large Omnivores
Large omnivores (bears) are another group for which it is exceedingly
difficult to measure impacts. Only three bear species occur within the
designated land types in North America. These will not be measurably
impacted for disturbances to the land area sizes under consideration.
For example, even without the problems of impact measurement, the 100 km2
10-23
-------
Table 10-2. Examples of -small herbivorous mammals, impacted by maximum
disturbance to specified types and sizes of land areas.a
MAJOR GROUPS
LAND TYPE
Desert
Prairie
Deciduous
Forest
Coniferous
Forest
Tundra
LAND USE
Agriculture
Suburban
SIZE OF LAND AREAb
0.1 km£
Cactus mouse
Pocket gophers
Pocket mouse
Harvest mouse
Grass voles
Jumping mouse
Deer mouse
Deer mouse
Phenacomys
Redback voles
Lemmings
Tundra redback vole
House mouse
Pocket gophers
Cotton ratsc
Black ratc
Norway rat
House mouse
1 km
Antelope squirrels
Kangaroo rats
Wood rats
Jackrabbits
Ground squirrels
Prairie dogs
Jackrabbits
Tree squirrels
Flying squirrels
Chipmunks
Cottontail rabbits
Marmots
Tree squirrels
Flying squirrels
Chipmunks
Showshoe hare
Ground squirrels
Jackrabbitsc
a Home range sizes taken from McNab, Vaughn, and Burt and
Grossenheider,4 or estimated from home range sizes of similar
species. Nomenclature of the genera and species follows Burt
and Grossenheider,4 where scientific names are also given.
b For land areas of 0.01 km2 or less no small mammal herbivore
should be impacted, above 1 km2 all should be impacted.
c Denotes pest species or genera.
10-24
-------
area size is only about half the size of the Grizzly bear home range.23
However, the actual effects on these animals can be serious since they
art. restricted to isolated patches of wilderness areas,4 and emigration
may not always be possible.
10.3.1.7 Small Omnivores
The impacts from disturbance of the larger area sizes may be
measurable for the small omnivores. These animals are generally nocturnal
and occur in areas which are human-disturbed (mainly agricultural). Im-
pacts should be easier to measure for opossums, and more difficult to
measure for the wider ranging raccoons.17 These animals are widely dis-
tributed where they occur, so that immediate impacts are difficult to
measure due to a reassortment of individuals during movement away from
the disturbed area.
10,3.1.8 Insectivores
Insectivores are small mammals with extremely limited mobility.
Like small rodents, they are closely tied to their area of residence
and can be expected to be measurably impacted in disturbances to all but
the smallest land area sizes. In'addition, these animals depend on insect
and other small animal prey, so that a disturbance to the prey can cause
as great an impact as a direct disturbance to the insectivores themselves.
10.3.1.9 Flying Mammals
The impact from a disturbance on the flying mammals (bats) is
roughly comparable to that on insectivorous birds. These nocturnal
animals have excellent mobility, but are most sensitive to disturbances
to breeding areas. In addition, many bat species are colonial, so the
breeding areas are patchy in occurrence. A disturbance of the smallest
designated area size could have a measurable impact on a breeding colony.
On the other hand, much larger feeding areas would have to be disturbed
to yield a measurable impact. Bat species occur in several types of land
areas.
10-25
-------
10.3.2 Long-Term Effects
The recovery phase of a mammal community is closely tied to the re-
covery of the vegetation. The food value of the vegetation is an impor-
tant determinant in mammal recovery. In addition, the amount of cover
provided by the vegetation is important to small mammals which are subject
to avian predators. The vertical height of the vegetation is actually of
less general importance since relatively fewer mammals are canopy dwellers
than ground dwellers. The main benefit provided by the vegetation height
is the amount of feed which exists at each level for herbivores and om-
nivores. Another extremely important benefit for some prey species is
cover.6 Naturally, the habitat beneath the vegetation should vary with
vegetative height and density. Therefore an important indirect benefit
is provided.
10.3.2.1 Large Carnivores--
Large carnivores will respond to the recovery of their prey following
a disturbance. The functional response of carnivores, an increase in the
exploitation of prey, can be practically instantaneous. However, the
numerical response, an increase in the number of predators in an area,
is necessarily slower. This response can occur both through immigration
or large carnivores to the recovering area and by reproduction, but
the latter process is much slower and may be masked by immigration.
Since large carnivores are not measurably impacted by a disturbance,
their recovery in an area will be a qualitative rather than a quantita-
tive change. Qualitative changes can be measured, but only on a very
restricted local scale, so that the measurements are of questionable
significance in assessing impacts to the individuals of highly mobile
species. The pertinent point is that the quality of the local area
changes when the animals leave.
10.3.2,2 Medium-Sized Carnivores--
The recovery of medium-sized carnivores should share the same
characteristics as the recovery of large carnivores, but on a more local
scale. Since medium-sized carnivores have less mobility, they will be
slower in responding to prey in the interior of a large disturbed area.
10-26
-------
However, the numerical response will still be made mainly by immigration.
Again, population changes of these animals will be limited by changes in
the populations of their prey. The medium-sized carnivores are also
unlikely to be impacted measurably, so that recovery will only be a
qualitative process.
10.3.2.3 Small Carnivores--
Disturbances to the larger land area sizes will have measurable
impacts on the small carnivores, and therefore "recovery" can be demon-
strated quantitatively. Since these carnivores are less mobile than the
larger classes, much of the numerical response must come from reproduc-
tion. Small carnivores should follow fluctuations in prey density much
more closely than larger carnivores due to their more limited mobility.
10.3.2.4 Large Herbivores--
For large herbivores, size effects are again of critical importance
in evaluating recovery from a disturbance and their recovery will be
qualitative rather than a measurable change. Since the large herbivores
are highly mobile (some are migratory), the rate of movement back into
an area will depend on the reestablishment of edible vegetation. The
number of large herbivores that a disturbed area can support will change
gradually, and some disturbed areas may actually support higher densities
than originally existed. This will occur where the plant food is
actually denser and/or of better quality during recovery than in the
climax community.
complex.
12
10.3.2.5 Small Herbivores--
The recovery phase of small herbivore populations can be extremely
3,12
Interspecies competition effects will be important in many
cases.~~ The recovery of small herbivore numbers should depend on both
immigration and reproduction. Small mammals are noted for their ability
to respond reproductively, but dispersal abilities can also play a
key role in their population dynamics. The recovery of small herbi-
vores should be very closely tied to changes in the vegetation, and
several distinct successional communities may occur.
10-27
-------
The immediate disturbance to an area may well create ideal conditions
for invasion by small "pest" rodents. These animals may aid plant suc-
cession by cycling nutrients in the community and thus provide a beneficial
function. However, competition may occur among "natural" species attempt-
ing to immigrate and could have a very detrimental effect. Careful manage-
ment of small mammals can provide means for facilitating community recovery.
Predators can be introduced to dampen outbreaks in small herbivore popu-
lations, if control measures are needed. Small mammal populations can
provide an index for monitoring community recovery of both the flora and
i.
fauna.
10.3.2.6 Large Omnivores
Because of their great mobility and large home range sizes, the re-
covery of large omnivores (bears) after a disturbance to an area is, like
that of other large animals, a qualitative process. The recovery of bears
is most likely to consist of them simply using the area to forage and/or
den in again. The problem of range reduction is a serious one for North
American bear species. Therefore real recovery may be very difficult if
the maximum area size disturbance causes the loss of one or both of a
breeding pair which live in an isolated patch of habitat. This problem
will rarely occur, however, and can be overcome by introduction of one or
more outside individuals as appropriate.
10.3.2.7 Small Omnivores--
The small omnivorous mammals are for the most part opportunistic
species. Both the opossum and raccoon are familiar species which have
managed to survive in areas of human disturbance due to their versatile
feeding abilities. The armadillo has actually extended its range of
occurrence in the Southwestern United States during the last hundred
years. Quantitative recovery of these species should occur closely
in pace with changes in both vegetation and prey species on the largest-
size area. These Species are reasonably mobile and can probably spread
as well by immigration as by reproduction.
10-28
-------
10.3.2.8 Insectivores
Insectivore recovery will depend on the recovery of insectivorous
prey, which in turn will probably depend largely on vegetative recovery.
Thus the return of insectivores to a disturbed area is a second-order
effect and will'require a longer time lag than that which will occur
for the similarly impacted small rodents. The recovery of moles will be
stimulated where macroinvertebrates are added to the soil ,o assist
vegetative recovery. Few insectivores breed more than twice a year, and
many breed but once. This will tend to retard recovery, as reproduction
is an essential part of colonization due to the animal's limited mobility.
10.3.2.9 Flying Manrnals
The recovery of bats after a disturbance to an area will vary with
the nature of the disturbance. Like many birds, bats require the re-
establishment of vertical structure in the vegetation. However, several
bat species roost in dead trees, so that available roosts may actually
increase from a disturbance. Bats are commonly known for their mobility.
Several species migrate seasonally, or nightly, to food sources. For
these reasons, bat recovery can occur rapidly after recovery of insect
prey in feeding habitats, and densities may actually increase given the
proper circumstances. Changes in bat populations will usually be due
to emigration and immigration rather than reproduction,
10.3.3 Land Types
Table 10-3 gives examples of mammal species other than small herbi-
vores from each trophic/niche group in each land type which are measurably
impacted if the maximum disturbance has been made to the specified land
areas. Large mammal groups are extremely mobile, and are therefore im-
pacted only by area sizes greater than 100 km2. Many of the species occur
in more than one land type. This phenomenon is more evident in this table
than it is for birds (Table 10-1) and small herbivorous mammals (Table 10-2)
The greater body size and mobility of many of the mammal species may be the
reason for this. Again, the number of home ranges lost is used in estimat-
ing the types of species lost when a given size area is disturbed.
10-29
-------
Table 10-3.
Examples of mammals other than small herbivores impacted by
maximum disturbances to specified types and sizes of land
areas.3
MAJOR GROUPS
1. LAND TYPE
DESERT
Large Carnivores
Medium Carnivores
Small Carnivores
targe Herbivores
Bats
PRAIRIE
Large Carnivores
Medium Carnivores
Small Carnivores
Large Herbivores
Small Oronivores
Insectivores
DECIDUOUS FOREST
Large Carnivores
Medium Carnivores
Small Carnivores
Large Herbivores
Large Omnivores
Small Omnivores
Inseetivores
Bats
CONIFEROUS FOREST
Large Carnivores
Medium Carnivores
Small Carnivores
Large Herbivores
Large Oranivores
Small Oranivores
Insectivores
Sats
TUNDRA
Large Carnivores
Medium Car-sivoren
Small Carnivores
Large Herbivores
Large Omnivores
2. LAND USES
AGRICULTURE
Medium Carnivores
Small Carnivores
Large Herbivores
Small Omnivores
Insectivores
Bats
SUBURBAN
Small Omnivores
Bats
SIZE OF LAND AREA
0.1 km2
. b
Yuma myotis
Vagrant shrew
Pacific mole b
Little brown myotis
Shortfall shrew .
Mexican freetail bat0
Eastern mole
Evening batD
h
Pallid bat0
! km2
Armadi llo
Least weasel
Least weasel
10 km2
Hoqnose skunk
Spotted skunk
Opossum
Long-tail weasel
Opossum
Short-tail "weasel
Opossum
Short-tail weasel
Spotted skunk
Opossum
Opossum
-100km2
Mountain lion
Kit fox
Mule deer
Coyote
Red fox
Pronghorn
Mountain lion
Lynx
Marten
Whitetail deer
Slack bear
Raccoon
Grey wolf
Lynx
Marten
Mule deer
Grizzly bear
Raccoon
Grey wolf
Arctic fox
Barren ground caribou
Grizzly bear
Red fox
Mule deer
Raccoon
Raccoon
3 Home ranqe si^es taken from McNab, Vaughn,23 and Burt and Grossenheider, or estimated from home range sizes
of similar species. Nomenclature of the genera and species follows Burt and Grossenheider»H where scientific
names are also given.
0 Bats, although migratory, appear in the smallest area category because of their colonial or semicolonial
nesting :haracteristics.
10-30
-------
Impacts can be defined more precisely as smaller mammals are ex-
amined, due to their reduced mobility which smaller size usually causes.
Therefore, in the discussion of the mammal fauna, small mammals are
emphasized. In addition, some land types, notably agricultural and
suburban, support more "pest" specimens than others. A special con-
sideration regarding these land types is the desirability of restoring
these mammals.
10.3.3.1 Deserts
The single most important and prevalent group of mammals in the
desert habitat is the small herbivores. Although large, medium, and
small carnivores, large herbivores, and bats may occur in deserts, their
diversity does not approach that of the small herbivores. When a desert
area is disturbed, some measure of the impact on small mammals is often
obtainable. However, the impact must be '.nferred from a comparison of
the disturbed area with some nearby area. The return of herbivores will
keep pace with the vegetation return, a distinctly slow process. Deserts
are continuous, so that colonization by both dispersal and reproduction
can occur from the edges of the disturbed area. Intermediate faunal com-
munities are not expected for succession in most desert disturbances.
10.3.3.2 Prairies
The prairie habitat supports a diversity of large herbovores. Car-
nivores of all sizes as well as small omnivores may occur here, but by far
the most abundant and diverse group in prairies is the small herbivores.
The importance of small herbivores in this habitat is greater than in any
other habitat except tundra, where their importance is roughly equal.
A disturbance to prairie will certainly have a measurable impact on some
small herbivores for all but the smallest area size. Therefore some
measurement of the recovery may be possible. The recovery of the small
herbivores may involve changes in the densities and distributions of the
species present, as the vegetation changes. The community recovery in
this habitat can be relatively rapid. The continuous nature of prairies
should aid in this process.
10-31
-------
10.3.3.3 Deciduous Forests--
Deciduous forests follow a pattern of response similar to coni-
ferous forests, but with some important differences. These forests can
be expected to be somewhat richer in their mammal fauna. The seasonal
change in canopy cover allows a richer understory of forage for both
large and small herbivores. Bats and insectivores occur here, but are
seldom a major component of the fauna. Medium size carnivores and
small omnivores should occur more frequently in deciduous forests. The
response of the mammal fauna to a disturbance may again involve the
movement of large mammals out of the area, and an increase in small
herbivores. In comparison to forests, the importance of small mammals
will be greater than in nonintensive agriculture during the recovery;
but in the mature forest, small mammals will have a similar importance
to that in nonintensive agriculture.
10.3.3.4 Coniferous Forests
In coniferous forests during the recovery cycle following a dis-
turbance the number of small mammals will probably increase rather than
decrease. Large mammals (carnivores, herbivores, and omnivores) will
usually leave the area, at least until restoration is well under way,
and then return. Thus in coniferous forest, impacts are very difficult
to measure but: recovery is easier to assess. This habitat is ideal for
the use of small mammals as indicators of recovery.
Bats and insectivores are relatively unimportant components of the
mammal fauna, though they do occur in coniferous forest. If insectivores
are present they may feed on insects which attack the dominant trees,
and thus increase their importance. The medium carnivores and small
omnivores are more likely to occur at the forest border, and thus will
recolonize from other habitats. The continuity of coniferous forests
should help most species recolonize from undisturbed areas.
10.3.3.5 Tundra Areas--
In tundra, small herbivores are key species to the ecosystem
economy. Small carnivores depend upon these herbivores for prey.
10-32
-------
Large herbivores, large omnivores, and large and medium carnivores may
also occur seasonally in tundra. A disturbance to tundra will certainly
impact the small mammals measurably in most years. The well known cyclic
fluctuations in population size of the dominant herbivores may cause an
inability to measure immediate impact in some years. However, the
recovery phase measurements of following years will show the impact
belatedly. Tundra is extremely sensitive to disturbance and a long
period of time is required for the vegetation to recover. Whether
the recovery of the tundra habitat and fauna is possible in ecological
time is questionable, and predictions about recovery cannot be made.
10.3.3.6 Coastal Inter-Tidal Marshlands--
The marshlands are not expected to support extensive mammal faunas.
10.3.4 Land Uses
10.3.4.1 Agricultural Areas--
Herbivorous species are generally detrimental to man's interests
where they occur in agricultural areas. The most common pests are, of
course, the small herbivores. However, as the intensity of agriculture
increases, the role of small herbivores decreaises. The other trophic/
niche groups are less frequent in occurrence in agriculture, but small
omnivores and medium-sized and small carnivores are considered pests
where animal husbandry is involved. Large omnivores and carnivores
should occur only rarely. Farm buildings are usually excellent places
for bat "nursery" breeding places, so that their occurrence in agri-
culture areas may be relatively high. Insectivores are a relatively
unimportant, though occurring, component of the mammal fauna here.
The recovery of mammals, particularly small herbivores, on dis-
turbed agricultural land can be extremely rapid. Most, if not all, of
the responding animals will be pest species. Most recovery problems
will involve having too many animals, at least in density, rather than
too few. Some beneficial effects may result from nutrient cycling
through small herbivores. However, these benefits are minimal because
of the control that man can exert on the nutrient balance.
10-33
-------
Here again, another alternative exists of allowing succession to
something similar to the preagricultural land type. This is best thought
of by considering agriculture as an additional disturbance to the treat-
ment under consideration. The mammal recovery will be similar to the
recovery described for the specific preagriculture land type, except
where precluded by fencing. Fences which restrict large mammal access .
will not greatly retard recovery, but may have subtle effects. For
example, if predators are excluded, prey species may be affected. A
fence which excludes all ground-moving mammals will eliminate, the re-
covery for all mammals except bats, and in some cases squirrels.
10.3.4.2 Suburban Areas
The suburban habitat, much like agriculture, is typified by pest
species. No large mammals of any type and no carnivores of any size
occur regularly in this habitat. Small omnivores, small herbivores,
and bats make up the rather depauperate mammal fauna of the suburban
habitat. The small omnivores have principal habitat elsewhere, and
the easily measurable impact to small herbivores is probably not of
concern. Feral domestic species, especially cats, may be impacted.
Again this is probably not of concern. What may be very important,
however, is the increase in rodent pests, and the diseases they carry,
during the recovery. Introduction of predators such as feral cats may
be the best technique for managing these outbreaks. The importance of
mammals in suburban faunas is likely to be quite low, perhaps on a
par with intensive agriculture.
If the suburban land use is abandoned, succession to a land type
similar to the presuburban one may occur. However, the rate and quality
of this recovery will depend on whether man-made structures remain or
not. As in agriculture, this land use itself may be considered a dis-
turbance. Fencing out large mammals will simply cause the loss of these
animals as participants in the recovery. However, fencing out all
ground-moving mammals may also fence surviving pest species in,, These
pests may require control measures to avoid health hazards to humans
which might periodically occur in the fenced area.
10-34
-------
10.4 CONCLUSIONS
The impact of a disturbance to a species was carefully defined at
the beginning of the wildlife section, but many people may simply want
to know if the disturbance will have a significant impact on the wild-
life species. This demands not only a definition of impact, but also an
evaluation of impact significance. If significance is defined as whether
or not a disturbance puts any species in danger of becoming extinct, for
the vast majority of wildlife species and the designated land areas the
answer is "no".
The real concern must be for those species so small in numbers that
extinction is a danger to them. These species fill the rare, threatened,
5 22
and endangered species lists. ' Many of these species are nearly
extinct due to man's encroachment upon their habitats. Other species
may be on the way to extinction with or without man's help. These two
classes of endangered species may be difficult to tell apart. Whether
or not species which are becoming extinct should be preserved is a social
decision. This decision, conscious or unconscious, will govern their
fate.
Many sensitive species may not be recoverable after a disturbance
to their range. Other sensitive species may require expenditure of a
great effort in order to assure their revival. This must be decided
upon in each case where an endangered species is affected, presumably
on the basis of the social and political values which predominate at
the time of the disturbance. Any effort directed to this end may also
have a fringe benefit of aiding in the recovery of the total floral and/or
faunal community.
Table 10-4 rates the relative impacts on wildlife, immediately after
cleanup, of the maximum disturbance possible in the individual treatment
categories in each land type for the stated area sizes. Impacts on
mammal and bird wildlife are scaled from 0 (no measurable impact) to 5
(elimination of most original species) for each combination of the three
axes of land type, treatment, and area size with the exception of fencing,
which divides impacts on mammals and birds.
10-35
-------
Table 10-4.
Relative impacts of land cleanup treatments on wildlife
following maximum possible land disturbance.
MAJOR GROUPS
LAND TYPE
Desert
Prairie
Deciduous
Forest
Conl ferous
Forest
Mountains
(Alpine)
Tundra
Coastal
Inter-Tidal
LAND USES
Agriculture
Suburban
TREATMENT
Stabilization, asphalt
Vegetation removal
Soil removal, stabilization
Fencing (mammals only)
Fencing (birds only)
Vegetation removal
'Soil removal, stabilization
Fencing (mammals only)
Fencing (birds only)
Stabilization, asphalt
Vegetation removal
Soil removal, stabilization
Fencing (mammals only)
Fencing (birds only)
Stabilization, asphalt
Vegetation removal
Soil removal, stabilization
Fencing (mammals only)
Fencing (birds only)
Vegetation removal
Soil removal, stabilization
Fencing (mammals only)
Fencing (birds)
Flooding
Vegetation removal
Soil removal, stabilization
Fencing (mammals only)
Fencing (birds' only)
Vegetation removal
Soil removal, stabilisation
Fencing (birds only)
Stabilization, asphalt
Vegetation removal
Soil removal, stabilization
Sludge application
Fencing (mammals only)
Fencing (birds only), soil additive
Stabilization, asphalt
Vegetation removal
Soil removal, stabilization
Fencing (mammals only)
Fencing (birds only)
TREATMENT*
NUMBER
4^0
1
2
3-2
3-2
1
2.
3-2
3-3
4-0
1
2
3-2
3-3
4-0
1
2
3-2
3-3
4-0
1
2
3-2
3-3
1
2
3-2
3-3
1
2
3-3
4-0
1
2
5-0
3-2
3-3
4-0
1
2
3-2
3-3
RELATIVE IMPACTS FOR DIP- b
FERENT AREA SIZES (in km2)
0.01 0.10 1.0 10 100
34555
1 2345
24555
01210
00001
1 2344
23455
01221
00011
24555
1 1233
23455
01210
00011
24555
1 1223
23455
0 12 10
00011
34555
34555
12321
00011
000 00
3 4 5 5 5
34555
12321
00011
34555
345 55
Oil 11
2 4 555
22345
1 1233
0 01 22
01211
00011
1 2345
01234
0 1122
001 00
0 0.0 00
a Treatment number 1 implies treatments 1-2 through 1-8, in general.
Treatment number 2 implies treatments 2-1 through 2-8, in general.
Relative impact, based on reduction in biomass
0 - No measurable Impact on species, < 5 percent reduction
1 - 5 to 35 percent reduction
2 - 35 to 60 percent reduction
3 - 60 to 80 percent reduction
4 - 80 to 90 percent reduction
5 - Original species eliminated, > 90 percent reduction
10-36
-------
The assignment of the values of the table is a subjective process
which necessarily assumes that all wildlife responds homogeneously to the
disturbance. Although such an assumption is unrealistic, the table still
provides insights toward the truth, i.e., reasonable estimates of hpw a
wildlife community responds to a disturbance. The table can also be viewed
as a ranking of treatments within each land type and area size.
Table 10-5 estimates the relative time for recovery of wildlife from
the maximum disturbance possible and the individual treatment categories
of each land type for the stated area sizes. The relative time to recovery
is scaled from 0 (about one year) to 5 (2 or 3 centuries). The one-year
period is required as a baseline to measure whether a community has changed
to a greater degree than would be expected under "natural" conditions.
The 5 rating puts recovery sufficiently far into the future that it is not
reasonable to consider that recovery can take place, since evolution'may
change the community before it reaches equilibrium.
One major assumption has been made in the derivation of relative im-
pacts: that is, the colonization rate must remain constant for all species
in the succession^! process. While this is not true in most individual
cases, it may be true on the average. That is, the species in the coloni-
zation process may have varying movement rates. But if the rates do not
vary widely, then violating the assumption may not be very serious. The
mathematical reasoning implies a linear relationship between area size and
recovery time. The constant colonization rate assumption is actually
another form of this assumption. .
Wildlife'is dependent on vegetative recovery; in fact, it is not
reasonable to try to uncouple these two types of recovery. Therefore,
Table 10-5 includes biases which are a direct result of considering the
total environment in which the wildlife lives. These biases are necessary
in order to improve the accuracy of impact assessment, and the computa-
tion of recovery times.
10-37
-------
Table 10-5.
Relative time for recovery of wildlife following
maximum disturbance to land and cleanup treatment.
MAJOR GROUPS
LAND TYPE
Desert
Prairie
Deciduous
Forest
Coniferous
Forest
Mountains
(Alpine)
Tundra
Coastal
Inter-Tidal
LAND USES
Agriculture
Suburban
TREATMENT
Stabilization, asphalt
Vegetation removal
Soil removal, stabilization
Fencing (manna Is only)
Fencing (birds only)
Vegetation removal
Soil removal, stabilization
Fencing (mammals only)
Fencing (birds only)
Stabilization, asphalt
Vegetation removal
Soil removal, stabilization
Fencing (mammals only)
Fencing (birds only}
Stabilization, asphalt
Vegetation removal
Soil removal, stabilization
Fencing (mammals only)
Fencing (birds only)
Vegetation removal
Soil removal, stabilization
Fencing (mammals only)
Fencing (birds only)
Flooding
Vegetation removal
Soil removal, stabilization
Fencing (mammals only)
Fencing (birds only)
Vegetation removal
Soil removal, stabilization
Fencing (birds only)
Stabilization, asphalt
Vegetation removal
Soil removal, stabilization
Sludge application
Fencing (mammals only)
Fencing (birds only), soil additive
Stabilization, asphalt
Vegetation removal
Soil removal, stabilization
Fencing (mammals only)
Fencing (birds only)
TREATMENT3
NUMBER
4-0
1
2
3-2
3-3
1
2
3-2
3-3
4-0
1
2
3-2 '
3-3
4-0
1
2
3-2
3-3
4-0
1
2
3-2
3-3
1
2
3-2
3-3
1
2
3-3
4-0
1
2
5-0
3-2
3-3
4-0
1
2
3-2
3-3
RELATIVE TIME FOR RECOVERY FORb
DIFFERENT AREA SIZES (in km2)
0.01 0.10 1.0 10 100
55555
22344
34555
21100
00000
11222
12344
2 11 00
0 00 00
45555
22333
23455
21100
00000
45555
22333
23 4 5 5
2 1 1 00
00000
34555
33455
21100
00000
00000
34555
33455
21100
00000
1 2,3 44
11222
00000
45555
11111
11111
11111
11000
00000
34555
12233
11122
1 1000
00000
a Treatment number 1 implies treatments 1-2 through 1-8, in general.
Treatment number 2 implies treatments 2-1 through 2-8, in general,
b T - - 1 year
1 - 1 to 3 years
2 - 3 to 5 years
3 - 5 to 50 years
4 - 50 to 100 years
5 - -100 years
10-38
-------
10.5 WILDLIFE REFERENCES
1. Adams, D. L. , and G. W. Barrett, 1976. "Stress Effects on Bird Species
Diversity Within Mature Forest Ecosystems." American Midland
Naturalist, 96(1), p. 179.
2. Belrose, F. C., 1976. Ducks, Geese, and Swans of North America.
Harrisburg, Penn.: Stackpole Books.
3. Bunnell, S. D., and D. R. Johnson, 1974. "Physical Factors Affecting
Pika Density and Dispersal." Journal of Mammology, 55(4),
pp. 866-69.
4. Burt, W. H., and R. P. Grossenheider, 1964. A Field Guide to Mammals.
Boston, Mass.: Houghton Mifflin Co., 284 pp.
5. California Department of Fish and Game, 1976. At the Crossroads.
6. Cook, Sherburne F., Jr., 1959. "The Effects of Fire on a Population
of Small Rodents." Ecology 40(1), pp. 102-108.
7. Delacour, J., 1954. The Waterfowl of the World. London: Country
Life Ltd.
8. Emlen, J. M., 1973. Ecology: An Evolutionary Approach. Reading,
Mass.: Addison-Wesley Pub. Co.
9. Emlen, J. T., 1974. "An Urban Bird Community in Tucson, Arizona:
Derivation, Structure, Regulation." Condor 72(2), pp. 184-97.
10, Frauzreb, K. E., 1976. "Comparison of Variable Strip Transect and
Spot Map Methods for Censusing Avian Populations in a Mixed
Coniferous Forest." Condor 78(2) , pp. 260-62.
11. Golley, F. B., K. Petrusewicz, and L. Ruszkowki, editors, 1975.
Small Mammals: Their Productivity and Population Dynamics.
Cambridge, Mass.: Cambridge University Press.
12. Joule, J., and G. N. Cameron, 1975. "Species Removal Studies I.
Dispersal Strategies of Sympatric Sigmodon hispidus and
Reithrodontomus fulvescens Populations." Journal of Mammology,
56(2), pp. 378-96.
13. Krebs, C. J., 1964. "The Lemming Cycle at Baker Lake, Northwest
Territories, during 1959-62." Arctic Inst. N. Amer. Tech. Paper
No. 15, 104 pp.
14. Krebs, C. J., 1966. "Demographic Changes in Fluctuating Populations
of Microtus californicus." Ecological Monographs, 36(3), pp.
239-73.
10-39
-------
15. Krebs, C. J., 1972. Ecology. New York: Harper § Row, Inc.
16. Lawrence, George C., 1966. "Ecology of Vertebrate Animals in Relation
to Chaparral Fire in the Sierra Nevada Foothills." Ecology,
47(2), pp. 278-91.
17. McNab, B. K., 1963. "Bioenergetics and the Determination of Home
Range Sizes." American Naturalist, 97(3), pp. 133-40.
18. Peterson, R. T., 1964. A Field Guide to Western Birds. Boston,
Mass.: Houghton Mifflin Co.
19. Pianka, E. R., 1974. Evolutionary Ecology. New York: Harper-Row,
Inc.
20. Schoener, T. W., 1968. "Sizes of Feeding Territories Among Birds."
Ecology, 49, pp. 123-41.
21. Twigg, G. I., 1975. "Marking Mammals." Mammal Review, 5(3), pp.
191-16.
22. U.S. Department of the Interior, Fish and Wildlife Service, 1976.
Endangered and Threatened Wildlife and Plants. Federal Register,
Wed. 27 Oct. 1976, pt. IV.
23. Vaughn, T. A., 1972. Mammology. Philadelphia, Penn.: W,B. Saunders
Co.
24. Welty, J. C., 1962. The Life of Birds. Philadelphia, Penn.: W.B.
Saunders Co.
25. Whittaker, R. H., 1970. Communities and Ecosystems. New York:
MacMillan.
10-40
-------
PART IV
APPENDICES
APPENDIX A, STABILIZERS
APPENDIX B, IMPACT ASSESSMENT
APPENDIX C. LAND TYPES
APPENDIX D, CLEANUP TREATMENTS
APPENDIX E, GLOSSARY
-------
-------
APPENDIX A
STABILIZERS
A.I INTRODUCTION
This appendix contains a brief description of the major categories of
soil stabilizers, the subgroupings of stabilizers, and the values assigned to
the stabilizer subgroupings, land types, and land-use classes given in Table
A-l. The use of Table A-l is also explained.
A.2 TYPES OF STABILIZERS
For purposes of this report, "soil stabilizers" are defined and categorized
to determine their practical application to soil stabilization with the land
types defined Herein. Stabilizers are generally classified into three major
categories according to Ingles and Metcalf:1 chemical, mechanical, and physi-
cal. A fourth category, chemical with mechanical characteristics, is also
considered here.
Individual stabilizers are shown at the top of Table A-l. The major
category of each is shown by a symbol underneath in one of the first two
horizontal rows; these rows additionally denote whether the stabilizer is
organic or inorganic. The stabilizers listed in Table A-l are listed in
Table A-2 with information on manufacturers provided for those that have
patented name.
A.2.1 Chemical
These stabilizers are liquid or solid additives to soil that effectively
alter the physical properties of the soil being treated.
A.2.2 Mechanical
These stabilizers mechanically provide sufficient stability to bare soils
to retard and/or prevent soil erosion caused primarily by wind and water,
A-l
-------
I,
I lit
IJ
j
k
I
CM
I
-------
without modifying the physical properties of that soil. The process con-
sists primarily of compacting soils to a density that rejects water. It also
includes hard surface materials, manufactured soil retention materials, and
chemical aids to compaction.
Materials used for mechanical stabilization of soils include, but are not
limited to, hard surface paving such as concrete and bituminous surfaces. .Other
manufactured materials are meshes, polyvinyl films, and erosion control-nettings.
Materials such ,as burlap bags with concrete, sandbags, rip-rap, and. cribbing
are also means of mechanical, stabilization.
Other forms of this type of stabilizer include the use of. grouts, sand,
and other filler compounds that can be used to physically fill voids in the
soil by absorbing water and swelling to seal off the surface area from water
infiltration.
Equipment used for mechanical soil stabilization is divided into two types:
(1) compaction equipment such as pneumatic-tired rollers, tandem rollers, sheeps-
foot rollers, vibratory rollers, vibratory packers; and (2) application equip-
ment such as concrete pavers, asphalt pavers, rock spreaders, distributors, and
sprayers.
A third subcategory of equipment also should be considered for mechanical
stabilization of contaminated areas. This includes equipment such as bull-
dozers, turn-a-pulls, and scrapers which are used to construct diversion channels,
ditches, berms, and retention basins around the affected area. (These structures
would be temporary to collect, divert, or retard surface drainage from adjacent
areas or to prevent water from leaving affected areas and causing downstream
contamination.)
A.2.3 Physical
These stabilizers stabilize soils by modifying their physical properties
with heat, electricity, and cold.
A.2.4 Chemical with Mechanical Characteristics
This term applies to stabilizers that are chemically produced or chemical
compounds that bind surface soils for short periods of time. Primarily, they
A-3
-------
are compounds used by the agricultural industry to promote germination and
then break down once germination has begun. They are not true "mechanical"
stabilizers because of their lack of relative permanency, and because there
are brief periods between application and stabilization during which chemical
reaction with soil occurs.
A.3 STABILIZER GROUPINGS
The four categories of stabilizers can be further categorized into group-
ings. These groupings define the physical characteristics and treatment types
to promote "prescription-type" treatment of affected areas within the land
types defined in the report. These groupings are shown at the left of Table
A-l, separated by broken lines. To determine the rating of a grouping cate-
gory for a particular stabilizer, use the number immediately above the broken
line for the grouping category. The key to these number ratings is at the
bottom of Table A-l.
The following definitions are provided for the groupings of soil sta-
bilizers:
Organic and Inorganic the category given to stabilizers that generally
define the physical composition of the specific material.
Hazard Levels primarily the degree of safety with which a stabilizer
can be handled by personnel during the application periods. It also
includes the "environmental safety" of the material after application.
Application the method or procedure of applying the prescribed
stabilizer to a defined area as it relates to available normal applica-
tion equipment and methods.
Durability the ability of a chemical or mechanical stabilizer to
maintain a specified treatment for a prescribed time period. This
includes the ability of a specified stabilizer to withstand the effects
of the seasonal environmental changes.
Vegetation Recovery Period the ability of a chemical or mechanical
stabilizer to disintegrate in the normal revegetation process where
localized natural seed sources are present (does not include conventional
reseeding methods).
A-4
-------
A.4 RATINGS OF STABILIZER GROUPINGS
The ratings of the stabilizer groupings noted on Table A-l are defined
as follows:
1, Safe a material or technique that is generally harmless to the
applicator, environment, and .equipment.
2, Handling Precautions Required requires compliance with manufac-
turers instructions for physical applications during handling, mixing,
applying, and temperature extremes.
5, Adverse Environmental Effects materials where there is no oppor-
tunity for the area to recover from the use of a stabilizer without
major rehabilitation operations. It does not include consideration as
a toxic substance to man.
4, Highly Hazardous materials or techniques where the "cure" is
more dangerous than the "disease." However, these can be situations
where highly specialized personnel can be called upon to perform this
type of stabilization.
A. 4.1 Application
1, Manual (normal) hand-operated.equipment that can be used effec-
tively and is frequently available to the home gardner.
2, Mapual (difficult) stabilizers that must be applied to a small
area, are caustic to operators and equipment, have difficulty staying
in solution, require difficult or specialized mixing techniques, or
require special carrier substances for proper application.
5, Equipment (normal) can be applied to large affected areas using
standard agricultural or construction equipment; restricted to areas
where there is space for the equipment to be used effectively.
4, Equipment (specialized) requires specially, manufactured equipment
for proper application or standard equipment greatly modified to accom-
modate the stabilizer to be used.
A-5
-------
A.4.2 Durability
1, Permanent will remain in place without radical physical change as
a result of normal climatic conditions. This includes the use of chemical
stabilizers that permanently change surface soil characteristics. Any
alteration of an area where this stabilizer is used would require major
construction.
2, Intermediate broad terminology meaning that natural recovery will
eventually take place. This also applies to stabilizers that persist
for at least 5 years when considered for surface applications. These
same stabilizers can persist for periods of more than 5 years when in-
corporated into a compacted soil.
3, Short Term (1 year or less) stabilizers that effectively control
soil movement resulting from normal rainfall. It also includes stabilizers
generally accepted in the agricultural industry as erosion retardents
during germination periods of most crops.
A.4.3 Vegetation Recovery
1, Immediate (natural) stabilizers which have little resistance to
climatic conditions, and which permit natural invader plants to germinate
and grow on disturbed areas.
2, Requires Seeding (normal response) effectively hold surface soils
intact for a period of at least 6 months, providing the applied membrane
is not disturbed. Revegetation requires normal seedbed preparation and
planting of selected varieties. Residues of these stabilizers, after
they are incorporated, are biodegradable and have no effect upon the new
seedlings.
3, Complete New Seedbed Required stabilizers that were used must be
completely removed or buried at sufficient depth with new "cold soil" so
that an affected area can provide suitable growing conditions for vegeta-
tive reestablishment.
4, No Recovery change the physical makeup of the surface soil suf-
ficiently so that the plant zone cannot subsequently support any type of
vegetation, and the stabilizer is not effectively altered by normal freeze
and thaw conditions.
A-6
-------
A.5 LAND TYPES AND LAND USE CLASSES
The seven land types and two land use classes discussed in this report
are shown at the right of Table A-l, separated by solid lines. To determine
the rating of each stabilizer on each land type or land-use class, use the
letter above the solid line for the particular land type or class. The key
to these letters (ratings) is located at the bottom of Table A-l. Each of
these ratings is defined as follows.
a, Preferred materials that are short-term effective, generally
environmentally safe naturally and sociologically, and subject to the
general moisture and climatic conditions of a land type.
b, Acceptable as an Alternate basically the same characteristics as
those classified "preferred," however, because of the effectiveness of
the material or application procedures they should not be considered
exclusively for stabilization of affected areas.
c, Not Acceptable (last resort measure) materials that should not be
used because of the resultant damage, primarily to the natural environ-
ment. When there are situations where the natural environment cannot be
protected from irreversible effects of "accidental spillage," these
materials may be used. This assignment is also made to materials when
applied to various land types because of the variability within the land
types themselves. For example, "prairies" can be divided into many
types of "prairie" and a particular stabilizer can be effective for
one of these "prairie" types without serious environmental damage. In
other "prairies," however, this same stabilizer would produce irreversible
effects and must not be used. Based upon this type of comparison with
each of the land types, the Mnot acceptable" assignment is made where
there is an irretrievable commitment of the natural resources present.
d, Not Applicable materials that cannot be applied because of soil
conditions, temperature extremes, or moisture conditions.
A.6 APPENDIX A REFERENCE
1.
Ingles, O.G., and J.B. Metcalf. Soil Stabilization Principles and Practice.
J. Wiley § Sons, New YorkToronto, 1973. 374 pp.
A-7
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APPENDIX B
IMPACT ASSESSMENT
B.I INTRODUCTION
This appendix presents the steps to be followed to obtain information from
Sections 1 through 3 of each chapter to derive area recovery index numbers.
These numbers are then used to identify preferred and unacceptable cleanup treat-
ments. The ranking of the impacts of these cleanup treatments is also discussed.
B.2 DERIVATION OF RECOVERY INDEX FROM SUCCESSIONAL SERE
The following steps describe the methods to be used to obtain the informa-
tion shown on Tables B-l and B-2 under column 3, titled "Duration of Succession
Stage:"
1. List the stages in the sere for the land type, starting from bare
ground and continuing through climax (herbs, shrubs, softwoods, and
hardwoods) in a loosely tabular format. Indicate the major stages
of co-dominance and assume secondary succession.
2. List the physiognomy stages appropriate to the land type (canopy
closure, subclimax, climax) opposite their successional equivalents,
where both occur.
3. List in a third column the range in years that successional stages and
physiognomy stages last in the sere. The years do not need to be
continuous between two ranges, e.g., 0-3 followed by 9-13 years.
Inflection points on the curves of Figure B-l prepared for the species
diversity, cover, and primary productivity cha.nges over the years from to to
100 or 200 years for 0-1 Natural Rehabilitation (Sections) are examples. The
Recovery Scenario of Section 5 applies a similar assessment routine to derive
descriptions of recovery at specific points in time: 1 year, 5 years, 50 years,
and 100 years after cleanup. For example;
1. Select a median year for each time range of column 3 (Duration of
Succession Stage). Where no median is available in the literature
B-l
-------
Table B-l. Hypothetical forest sere.
Succession
Mixed herbs
(grasses & forbs)
Grasses
Shrubs
Softwoods
Co-dominants
(Softwoods &
Hardwoods )
Hardwoods
Physiognomy
Stage
Pioneer
invasion
Cover
closure
Canopy
closure
Crown
cover
Subclimax
Climax
Duration of
Succession
Stage
0-10
10-20
20-30
30-100
100-150
150-300
Median
Year of
Succession
3
15
25
70
120
200
Median
Years to
Climax
200
185
175
130
80
0
Relative
Recovery
Index
5
4
3
2
1
0
Table B-2. Hypothetical grassland sere,
Succession
Herbaceous
Annual Grasses
Co-dominance
Bunch grasses
Tall grass
Prai ri e
Physiognomy
Stage
Pioneer herbs
Covered
surface
Transition
Subclimax
Climax
Duration of
Succession
Stage
0-2
9-13
18-20
25-75
100- ?
_^« ,«^ ^B^ ^^ ^^ -^^
Median
Year of
Succession
1
12
20
60
200
Median
Years to
Climax
200
190
180
40
0
Relative
Recovery
Index
4
3
2
1
0
B-2
-------
0-1 NATURAL REHABILITATION
HERB (SHRUB | TREE STAGES
MANAGED REHABILITATION
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Example of times for recovery from cleanup in coniferous
forest by natural and managed rehabilitation.
8-3
-------
assume the years are on a logarithmic scale and the median is the log
of the mean (skewed towards the high side). List the medians in column
4 (Median Year of Succession).
2. Subtract each of the medians in column 4 from the climax median and
enter the differences in column 5 (Median Years to Climax), rounding
years >50 to the next decade either forward or backward. Label column 5
as "Years to Climax," observing that the entry for climax is zero.
3. Label column 6 as "Relative Recovery Index" and enter zero opposite
climax in the physiognomy column. Select significant stages in the
sere (for which quantitative data in years are available) as guideposts
for the Index. Starting from climax, which is zero in the Index,
assign numbers to the guideposts so the sequence increases upwards to
the start of the sere. Hardening surface becomes N+l and N+2 becomes
"Intervention required to enter sere." For practical use, N+2 should
be less than 10.
B.3 RANKING OF DISTURBANCE FROM CLEANUP TREATMENTS
The following paragraphs describe the ranking of cleanup impacts upon 0.01
km2.
To evaluate the time required for recovery from the cleanup, define the
physical disturbance caused upon 0.01 km2 of the land type by performing each
one of the treatments given in the working matrix, between 0-1 Natural Rehabili-
tation and 7-0 Adding Soil Amendments. Enumerate the potential disbenefits
that will impact natural revegetation and specify which kinds of vegetation
will be helped and which will be harmed. Consider erosiveness, soil moisture
relationships, fertility and soil tilth reconstitution requirements for revege-
tation to reenter into succession towards climax. This is the material for
Section 4, Effects of Cleanup (damage assessment).
Discuss the retrogressive effects the physical disruption causes upon
climax conditions in the land type for each of the cleanup procedures. Esti-
mate which part of the sere revegetation will start with, which parts of suc-
cession can be skipped over, and which cannot be omitted in the physiognomy
progression.
B-4
-------
Rank the impacts caused by each cleanup on specific parameters important
in the ecosystem and compile a summary of the rankings as in Table B-3. Define
the assumptions made during the ranking and record them (see Table B-4, column
7) for the final tabulation in Section 6, Quantitative Assessment. Assemble
the known data/ on years to return to clisax after specific impacts, from Sec-
tions 1 through 3 and enter the years in Table B-4, Years Estimated to Reach
Climax. Estimate the missing years for the 0.01 km2 column of Table B-4 by
using the ranked impacts in Table B-3.
Next consider the effect that increasing the area cleaned up will have
upon the years estimated to pass before the sites reenter climax. For each
cleanup treatment extrapolate, the recovery years following retrogression from
climax to areas larger than 0.01 km2 and evaluate the impacts at 0.10, 1.0,
10.0 and 100 km. Discuss those cleanups as a unit that reattain climax by
passing through similar numbers of stages of succession. This discussion
forms the interpretive backbone of Section 6, Quantitative Assessment. Fill
in the remaining four columns of Table B-4, Years Estimated to Reach Climax.
Pick a sequence of points in time to discuss that extends from the first
year after cleanup until climax has been reattained. Compare that scenario to
columns 1 and 2 of Tables B-l and B-2, at frequent intervals in succession,
and group those treatments together that pass through the same physiognomy
stages at the same time. These assessments, when written up, constitute the
text of Section 5, "Recovery After Cleanup." The text should also include
comparisons of the times like groups require to attain climax and should iden-
tify irreversible impacts.
B.4 RECOVERY INDEX NUMBER ASSIGNMENT
Use the median year of succession for the cleanup treatment (Table B-4)
as the entry into the treatment-km2 matrix, basing the median on the stage of
succession or stage of physiognomy generated under the heading "Derivation of
Recovery Index from Successional Sere." Median years are required for 0.01,
0.1, 1.0, and 10.0 km areas for each treatment in the matrix (Section 6).
Those treatments that were deleted should be indicated by an asterisk. Those
which require man's intervention before they enter into succession are to be
given # symbols. An NA should be used in the matrix for treatments that should
not be used in the land type, otherwise defined as irreversible impacts. Trans-
fer the "Assumptions" from column 7, Table B-4 to column 7, Table B-6.
B-5
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Go to Section 7 and select the least damaging treatments and discuss their
advantages over other treatments as part of the Conclusions Section (Section 7).
Perform the same analysis for treatments that are not usable on the land type,
rated # or NA in Tables B-5 and B-6.
Once the recovery times and the area effects are evaluated complete the
Recovery Index and Guide Numbers, columns 6 and 7 in Table B-5. Cleanup that
leaves the site at climax is rated as zero impact even though it may be some
time before it regains productivity, for example mowing bunchgrass. The Index
Numbers "count" the stages in a sere. The largest one represents the greatest
site retrogression and the longest recovery time to regain climax; its Guide
Number is N. Cleanup recovery that will progress through succession but de-
lays in starting recovery is more severe than those which begin succession
immediately. Nevertheless, they are of the same order and kind of recovery
as those with a smaller Recovery Index, and the Guide Number is increased one
to account for the greater time for recovery, from N to N+l. An example of
an N+l Guide Number is that of breakup of asphalt hard surface that delays
succession 20 years in the hypothetical coniferous forest of Table B-5.
In some ecosystems, cleanup can provide changes which allow secondary im-
pacts severe enough to prevent a succession occurring that lead:; to the pre-
cleanup climax. One example is removal of the plow layer from conifers on a
shallow soil on a steep hillside, taking the accumulated organic matter and
surface horizon mineral soil. Subsequent erosion over time can eliminate the
contaminated, cleaned-up site by replacing it with a gully that continues to
the barren bedrock. The original forested site no longer exists. In this
case, the timely intervention by site renovators could return the site of
cleanup into conditions that bring back the prior sere. These cleanup impacts
are defined as the "Conditional Stage" and are another one of the pre-succession
stages. They are given a Recovery.Index that is non-numerical (the symbol used
in Table B-5 is #); the analogous Guide Number is N+2, which should be less
than 10 for convenience.
The final Guide Number is that assigned to cleanup impacts which produce
"Irreversible" impacts and in Table B-5 the acronym is NA. This concludes
the mechanism for generating Index and Guide Numbers to represent the impacts
caused by contamination cleanup.
B-8
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B.5 APPENDIX B REFERENCE
1. Lawrence, D. B. The Glaciers and Vegetation in Southeastern Alaska.
.American Scientist, Summer 1958. pp. 89-122.
B-ll
-------
-------
APPENDIX C
LAND TYPES
Aeolian Mountain Peaks High mountain terrain above trees and flowering
plants, above alpine zones.
Coastal Inter-Tidal Marsh Low, flat marshlands traversed by interlaced
channels amid tidal sloughs and subject to tidal inundation;
normally, the only vegetation present is salt-tolerant bushes and
grasses.
Coniferous Forest A plant association predominantly of trees of the
order Coniferae, having evergreen leaves shaped like needles or
scales; such trees produce softwood lumber. Understory may be
highly variable, from humid ferns to semiarid grasses and shrubs.
Deciduous Forest A plant association predominantly of trees and other
woody vegetation which seasonally loses all its leaves.
Desert An area of land that has an arid, hot to cool climate with
vegetation that is sparse and usually shrubby.
Prairie A tract of level to hilly land that has a dominance of grasses
and fprbs, has a scarcity of shrubs, and is treeless. The natural
plant community consists of various mixtures of tall, mid- and
short-growing native species, also known as true prairie, mixed
prairie, and shortgrass prairie, respectively.
Salt Marsh Low area adjacent to the sea that is covered with salt-tolerant
vegetation and regularly flooded by the high tide; similar inland
areas near saline springs or lakes, though not regularly flooded.
Tundra The treeless land in arctic and alpine regions; varying from bare
area to various types of vegetation consisting of grasses, sedges,
forbs, dwarf shrubs, mosses, and lichens.
C-l
-------
-------
APPENDIX D
CLEANUP TREATMENTS
Treatment Treatment
Number Name
1-1 Chemical
Stabilization
1-2
1-3
1-4
1-5
1-6
1-7
1-8
Clearcutting
Stumping and
Grubbing
Surface
Scraping and
Grading
Plowing
Soil Cover
Erosion prevention through the use of soil addi-
tives to promote increases in soil cohesion or
shear strength, bulk density, water retention,
and/or surface cohesion (see Appendix A).
A method of cutting that removes the entire
vegetational stand; usually refers to lumbering
operations. Synonyms here include mowing.
The operation of removing stumps and roots.
Removal of the upper soil layers to 5 cm by means
of bulldozers, road graders, or other heavy or
medium equipment with controlled cutting.
Employment of a device to cut, lift, break up, and
turn over the soil, usually leaving parallel
furrows on the surface. Depth ranges are:
Shallow (<10 cm) and Deep (10 40 cm).
Soil collected from uncontaminated borrow pits,
surface areas, road excavations; generally expected
to be a poorer medium for plant growth than the
soil covered up.
2-1 Removal of
Plow Layer
Soil
2-2 Removal of
Shallow Root
Zone Soil
2-3 Surface Soil
2-4 Removal with
2-5 Mechanical
Stabilization
"Plow layer soil" defined here as from surface to
depth of about 10 centimeters. Removal can be by
hand shoveling,, bulldozers, scrapers, front-end
loaders.
"Shallow root zone" defined as that part of the
soil, up to a depth of 40 cm, that is penetrated
or can be penetrated by plant roots.
Physical removal of contaminated surface and soil
from the affected area with depth-controlled equip-
ment, dozers, front-end loaders, or scrapers. The
exposed surface remaining is mechanically compacted
to a maximum density by heavy equipment or is resur-
faced with impervious materials such as soil-cement
or NaCl. The resultant effect is to remove the con-
taminant and to seal the exposed surface against
water infiltration.
2-3 The cut removes less than 5 cm of material,
2-4 Up to 10 cm of material may be removed.
D-1
-------
2-6
2-7
2-8
Surface Soil
Removal with
Chemical
Stabilization
3-1
3-2
3-3
Barrier
4-0
4-1
4-2
Mechanical
Stabilization
(asphalt)
(concrete)
2-5 Removes the shallow root-zone and may ex-
tend to 40 cm. The deepest soil removal
may cause temporary impoundment of surface
waters.
The physical operations for these treatment pro-
cedures are similar to those discussed for 2-3
to 2-5. The basic differences between the two
treatment types are:
a. the method of subsurface stabilization
b. the size of the treated area.
Chemical subsurface stabilization is the applica-
tion of one of the chemical forms of stabilizers
as defined in "Appendix A, Stabilizers" to create
change in the physical soil structure.
Most chemical stabilizers are restricted to areas
in size where the surface soils were removed by
hand methods or with small tractor end-loader
equipment (from 0.01 km2 to 0.1 km2). The usual
application of the selected chemical stabilizer
is by hand methods. This foregoing description
must not be construed to preclude the use of
chemical stabilization on larger areas where
heavy equipment can be used for the chemical
application. However, the treatment is generally
restricted to smaller areas or to urban situations.
A vertical impediment such as a wall or fence which
serves to prevent horizontal animal movements.
A reinforced heavy high barrier for large animals
(bison, moose, elk) and a buried edge fine mesh
barrier (including sheet metal flashing) to impound
small animals (pocket mouse, moles, grass vole, but
excluding bats). Horizontal barriers (screens or
sheets) may also be employed to prevent vertical
animal movements.
Erosion prevention through compaction of the surface
soil through tamping, rolling, vibration, electro-
static methods, plastic sheeting, and other non-
chemical means. Hard-surface stabilization (paving)
is included here.
5-0
Sewage
Sludge
Settled sewage solids combined with varying amounts
of water and dissolved materials that are removed
from sewage by screening, sedimentation, chemical
precipitation, or bacterial digestion.
Application may serve to increase soil permeability,
increase soil fertility, and increase soil water
retention, thus reducing soil erosion and contaminant
mobility.
D-2
-------
6-1
6-2
7-0
Washing
Flooding
Soil
Amendment
A system to spray water under high pressure over
streets, buildings and impermeable surfaces to sus-
pend and remove contamination in a volume of water
equivalent to 3 mm or less over the washed surface.
Inundation of a surface by water in an effort to
wash a contaminant downslope or into deeper soil
regions, using 3 to 30 cm of water.
Any material, such as lime, gypsum, sawdust, or
synthetic conditioner, that is worked into the
soil to make it more amenable to plant growth.
Plant growth is stimulated to act as a surface
cover and thus as an erosion preventative; some
amendments may also serve to prevent contaminant
uptake by plants or to promote contaminant uptake
by plants, in which case the plants could be
removed for storage as contaminated wastes, having
incorporated the contaminant in their tissues.
D-3
-------
-------
APPENDIX E
GLOSSARY
Aeolian Soil Material Soil material accumulated through wind action.
Adsorption The molecular attraction of a substance to the surface
of a solid or liquid.
Afforestation The artificial establishment of forest crops by planting
\_ or sowing on land that has not previously, or recently, grown trees.
Agricultural Land Land in farms regularly used for agricultural pro-
duction.
A Horizon See Soil Horizon.
Algae Simple plans, many microscopic, containing chlorophyll; forming
the base of the food chain in aquatic environments.
Alluvial Pertaining to material that is transported and deposited by
running water.
Alpine That portion of mountains above tree growth or organisms living
there.
Animal Unit A measurement of livestock numbers based on the equivalent
of a mature cow (approximately 1,000 pounds live weight).
Annual Plant A plant that completes its life cycle and dies in 1 year
or less.
Ap The surface layer of a soil disturbed by cultivation or pasturing.
Arborescent Resembling a tree in properties, growth, structure, or
appearance.
Arid Regions or climates that lack sufficient moisture for crop pro-
duction without irrigation.
Aspect (forestry) The direction that a slope faces.
Autogenic Orginating within.
Autotroph An organism that manufactures its own food, such as a plant.
Benthos The plant and animal life whose habitat is the bottom of a
sea, lake, or river.
Berm A shelf or flat area that breaks the continuity of a slope.
B Horizon See Soil Horizon.
E-l
-------
Biocoenosis The plants and animals comprising a community.
Biomass The total amount of living material in a particular habitat
or area.
Biome A unit of plant and animal communities having similarities
in form and environmental conditions.
Biota The flora and fauna of a region.
Blowout (1^ An excavation in areas of loose soil produced by wind;
(2) a rupture of soil surface attributable to hydraulic pressure.
Bole The'trunk of a tree.
Boreal Of, relating to, or located in northern regions.
Brunizem (Prairie) Soils The group of soils developed under tall
grasses in a temperature, relatively humid climate.
Buffer Strips Strips of erosion-resisting vegetation between culti-
vated strips or fields.
Canopy The cover of leaves and branches formed by the tops or crowns
of plants.
Catch Crop 1) A crop produced incidental to the main crop, usually
occupying the land for a short period; 2) A crop grown to replace
a main crop which has failed.
Check Dam Small dam constructed in a small watercourse to decrease
the streamflow velocity, minimize channel scour, and promote
deposition of sediment.
Chiseling Breaking or loosening the soil" with a chisel cultivator or
chisel plow.
C Horizon See Soil Horizon.
Ciliated Provided with a minute hairlike process of many cells that
is capable of lashing movement.
Clearcutting A cutting method that removes the entire timber stand.
Climate The total of all atmospheric or meteorological influences,
principally temperature, moisture, wind, pressure, and evaporation.
Climax The terminal stabilized system of an ecological succession.
Clone A group of organisms derived by asexual reproduction from a
single parent.
Coarse Texture The soil texture exhibited by sands.
E-2
-------
Co-dominant Trees Trees with crowns forming the general level of the
forest canopy and receiving full "light from above but comparatively
little from the sides.
Colluvial Material that has moved downhill and has accumulated on
lower slopes and/or at the bottom of the hill; material of
avalanches.
Community An aggregation of organisms within a specified area.
Compaction The process by which soil grains are compressed, thereby
increasing the weight of solid material per cubic foot.
Conifer A softwood tree belonging to the order Coniferae with cones
and evergreen leaves of needle shape or "scalelike."
Contour Ditch Irrigation ditch laid out approximately on the contour.
Contour Farming Plowing, planting, cultivating, and harvesting on the
contour.
Coppice - A growth of small trees originating mainly from sprouts or root
suckers rather than from seed.
Copse Coppice.
Cover, Percent The area covered by plants and mulch expressed as a
percent of total area.
Cropland Land used primarily for the production of cultivated crops.
Crown (forestry) The upper part of a tree, including the branches
and foliage.
Crown Class All trees in a stand with tops or crown occupying a
similar position in the canopy. Crown classes usually distinguished
are:
Dominant Trees with crowns extending above the general level
of the forest canopy.
Co-dominant Trees with crowns forming the general upper level
of the forest canopy.
Crown Cover The canopy formed by the crowns of all the trees in a forest,
Cutting Cycle The planned interval between major cutting operations
in a managed woodland tract.
Deciduous Plant A plant that sheds all its leaves every year at a
certain season.
E-3
-------
Deflocculate To separate the individual particles of compound aggregates
by chemical and/or physical means.
Delta An alluvial deposit formed where a stream or river drops its
sediment load on entering a body of more quiet water.
Dendritic Tree-like.
Detritus Matter worn from rocks by mechanical means; generally,
alluvial deposits.
Diatom Algae with silicified skeletons.
Dominant (ecology) Species which by their activity, behavior, or
number have considerable influence or control upon the conditions
of existence of associated species.
Duff The organic layer on top of mineral soil.
Ecology The study of interrelationships of organisms to one another
and to their environment.
Ecosystem A community, including all the component organisms, together
with the environment, forming an interacting system.
Ecotone A transition strip of vegetation between two communities, having
characteristics of both kinds of neighboring vegetation as well as
characteristics of its own.
Environmental Impact Statement A document detailing the environmental
impact of a proposed action that may significantly affect the quality
of the environment.
Erosion The wearing away of land surface by running water, wind, ice,
or other geological agents.
rill erosion a process in which numerous small channels only
several inches deep are formed.
sheet erosion the removal of a fairly uniform layer of soil
from the land surface by runoff water.
splash erosion the spattering of small soil particles caused
by the impact of raindrops on wet soils.
Evergreen Perennial plants that are never entirely without green
foliage.
Fallow Allowing cropland to lie idle, either tilled or untilled, during
the whole or greater portion of the growing season.
Farm Forestry The practice of forestry on farm or ranch lands generally
integrated with other farm or ranch operations.
E-4
-------
Fertilizer Any organic or inorganic material that is added to a soil
to supply elements essential to plant growth.
Fibrous Root System Having a large number of small, finely divided,
widely spreading roots but no large individual roots.
Field Planting (forestry) The establishment of woody plants on land
essentially free of trees.
Forb An herbaceous plant which is not a grass, sedge, or rush.
Fragipan A natural subsurface horizon, low in organic matter, with
high bulk density; seemingly cemented when dry but showing a
brittleness when moist.
Frost Heave The raising of a surface due to the accumulation of ice
in the underlying soil.
Gabion A wire mesh cage filled with rock and used as a protecting
apron against erosion. .
Gley (soil) pale gray to bluish white horizon high in ferrous
compounds and other oxygen deficient decomposition products.
Grass A member of the botanical family Gramineae,characterized by
bladelike leaves arranged on the stem in two ranks.
Grove A small group of trees, usually without understory, planted or
natural. ,
Gully Control Plantings The planting of forage in gullies to establish
a vegetative cover adequate to control runoff and erosion. .
Habitat The environment in which the life needs of a plant or animal
organism are supplied.
Hardwoods Trees that have broad leaves, in contrast to the conifers;
also wood produced by trees of this group regardless of texture.
Herb Any flowering plant except those developing persistent woody
bases and stems above ground.
Heterotrophic Pertaining to organisms that are dependent on organic
material for food.
Homeostasis Ecologic inertia of a population, under stress by changing
conditions, which restores a prior equilibrium through self-adjust
ment. , ,
Hydric Requiring an abundance of moisture.
Hydrophyte A plant that grows in water or in wet or saturated soils.
E-5
-------
Illuvial A soil layer or horizon in which material carried from an
overlying layer has been precipitated from solution or deposited
from suspension. The layer of accumulation.
Insolation Incoming solar radiation.
Interstices The pore space or voids in soil and rock.
Invader Plant Species Plant species that were absent in undisturbed
portions of the original plant community and will invade under
disturbance or continued overuse.
Invasion The migration and establishment of organisms from one area
to another area.
Irreversible Incapable of correction or of being reversed.
Kame A conical hill or short irregular ridge or gravel or sand
deposited in contact with glacier ice.
Mesic (soil) formed under a mean annual temperature range of 15° to
22°C (59° to 72°F) at 50 cm depth.
Mesophyte A plant that grows under intermediate moisture conditions.
Microflora Bacteria, including actinomycetes, viruses, and fungi.
Mitigation (wildlife) The reduction or elimination of damages to
fish and wildlife resources.
Montane (1) pertaining to mountain conditions; (2) the lower vegetation
belt on mountains.
Moraine An accumulation of rock debris by the direct action of glacial
ice.
Mulch A natural or artificial layer of plant residue or other materials,
such as sand or paper, on the soil surface.
Muskeg Bog; especially a sphagnum bog of northern North America.
Mycorrhizal The fungal complex with the roots of a seed plant.
Native Pasture Land on which the climax plant community is forest, but
which is used and managed primarily for the production of native
species for forage.
Native Species A species that is a part of an area's original fauna
or flora.
Niche A habitat that supplies the factors necessary for the existence
of an organism or species.
E-6
-------
Old-Field An abandoned agricultural field.
Outwash The material, cheifly sand or gravel, washed from a glacier
by the action of roeltwater.
Overburden The earth, rock, and other materials that lie above a
mineral deposit.
Overstory The portion of the trees in a forest stand forming the
upper crown cover.
Phenology The study of the time of appearance of characteristic
periodic events in the life cycles of organisms in nature and how
these events are influenced by environmental factors.
Phreatophyte A plant deriving its water from subsurface sources;
commonly used to describe nonbeneficial, water-loving vegetation.
Phytoplankton Unattached microscopic plants of plankton, subject to
movement by wave or current action.
Physiography A description of nature or natural phenomena in general.
Piping Removal of soil material through subsurface flow channels developed
by seepage water.
Pitting (1) making shallow pits to retain water from rainfall or snowmelt
on rangeland or pasture; (2) small cavities in a surface created by
corrosion, cavitation, or subatmospheric pressures.
Plant Succession The process whereby an area becomes successively
occupied by different plant communities of higher ecological order.
Primary Productivity The rate (grams per day) at which organic matter
is stored by photosynthesis and chemosynthesis of producer organisms
(autotrophs).
Protozoa Single-celled animals.
Pyric Resulting from, induced by, or associated with burning.
Range (1) Rangeland, and forestlands with understory suitable for grazing;
(2) the geographic area occupied by an organism.
Reclamation The process of reconverting disturbed lands to their former
uses or other productive uses.
Rehabilitation Returning of land to productivity in conformity with
prior land use, including a stable ecological state consistent with
surrounding aesthetic values.
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Relict A remnant or fragment of a flora that remains from a former
period when it was more widely distributed.
Restoration The process of restoring site conditions as they were before
the land disturbance.
Retrogression Reverse succession under environmental stress.
Savanna A grassland with scattered trees; often a transitional type
between true grassland and forest.
Scarify To abrade, scratch, or modify the surface.
Scenario The order of events in time describing interacting forces,
environmental influences and organisms.
Scree (1) Pebble, stone; (2) a heap of stones or rocky debris.
Seedbed The soil prepared to promote the germination of seed and
the growth of seedlings.
Sequum The generally gradual changes in soil properties in horizontal
or vertical directions from the soil body in question.
Seratinous Late, especially in developing or flowering.
Sigmoidal A slanted S-shaped curve.
Site (ecology) (1) an area considered for its ecological factors with
reference to capacity to produce vegetation; the combination of
biotic, climatic, and soil conditions of an area; (2) an area
sufficiently uniform in soil, climate, and natural biotic con-
ditions to produce a particular climax vegetation.
Snow Fence A fence used in winter to intercept drifting snow, thus
protecting roads and other areas from snowdrifts. Also used to
impound snow where melting in place adds to soil moisture.
Soil Amendment Any material, such as lime, gypsum, sawdust, or synthetic
conditioner, that is worked into the soil to make it more amenable
to plant growth.
Soil Horizon A layer of soil or soil material approximately parallel
to the land surface and differing from adjacent genetically related
layers in physical, chemical, and biological properties or charac-
teristics, such as color, structure, texture, consistence, kinds
and numbers of organisms present, degree of acidity or alkalinity,
etc. Designations and properties of three major soil horizons are
as follows:
A Horizon. Topsoil, the zone of maximum concentration of soil
organisms and biotic activity. This is the horizon in which
organic debris becomes converted into humus and mixed with
mineral matter. It is the zone of eluviation in which pre-
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Solum
cipitation, mixed with acids from decomposing organic matter
dissolves arid carries further down into the soil the more
soluble materials
B Horizon. The lowest true soil, or subsoil. This zone lying
below the horizon of maximum leaching is an area of illuvl-
ation, or deposition for minerals leached out of the topsoil,
and in particular it is a layer in which clays tend to accum-
ulate. In arid regions it will be a layer of accumulation
for calcium carbonate, magnesium carbonate, gypsum, or other
soluble salts.
C Horizon. A layer of unconsolidated material and rock fragments
lying above the unmodified parent rock and below the true
soil. It usually contains little material modified by living
organisms, although it may be broken, split or cracked by the
roots.
The upper and most weathered part of the soil profile; the A and B
horizon.
Spoil Soil or rock material excavated from a canal, ditch, basin, or
similar construction.
Stabilized Grade The slope of a channel at which neither erosion nor
deposition occur.
Stratification The process or arrangement or composition in strata
or layers.
Strip Mining A process in which rock and top soil strata overlying min-
eral deposits are scraped away by mechanical shovels. Also known
as surface mining.
Substrate (1) in biology, the base of substance upon which an organism
is growing; (2) in chemistry, a substance undergoing oxidation;
(3) in hydrology, the bottom material of a waterway.
Succession The progressive development of vegetation toward its highest
ecological expression, the climax; replacement of one plant com-
munity by another.
Surface Compaction Increasing the dry density of surface soil by
applying a dynamic load.
Surface Water All water whose surface is exposed to the atmosphere.
Tacking The process of binding mulch fibers together by the addition
of a sprayed chemical compound.
Taxonomy - (1) the science of classification; (2) classification of
animals and plants, such as species, genus, family, and order.
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Tilth The physical condition of soil as related to its ease of tillage,
fitness as a seedbed, and impedance to seedling emergency and root
penetration.
Topsoil (1) earthy material used as top-dressing with favorable charac-
teristics for production of desired kinds of vegetation; (2) the
surface plow layer of a soil; (3) the dark-colored upper soil that
ranges in depth with different kinds of soil; (4) the A horizon,
varying widely among different kinds of soil.
Trophic Level The level in a nutritive series of an ecosystem in
which a'-group or organisms in a certain stage in the food chain
secures food in the same general manner. The first 'or lowest
trophic level consists of producers (green plants); the second
level of herbivores; the third level of secondary carnivores; and
the last level of reducers.
Truncated Soil Profile Soil profile that has been cut down by accelerated
erosion or by mechanical means. The profile may have lost part or
all of the A horizon and sometimes the B horizon, leaving only the
C horizon.
Undergrowth (forestry) Seedlings, shoots, and small saplings under an
existing stand of trees.
Understory That portion of the trees in a forest below the upper
crown cover, also called underwood.
Urban Land Areas so altered or obstructed by urban works or structures
that identification of soils is not feasible. A miscellaneous land
type; towns of over 2,500 are defined as urban by the U.S. Bureau
of Census.
Vegetation Plants in general or the sum total of plant life in an area.
Vertical Stratification The process of arrangement or composition
in strata or layers vertically, as in understory shrubs and over-
story tree canopy.
Wildlife Undomesticated vertebrate animals, except fish, considered
collectively.
fr U.S. GOVERNMENT PRINTING OFFICE; 1993 7 1 5 - 0 0 3 / 87085
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