United Slates
Environmental Protection
Agency
Environmental Research
Laboratory
Corvallis, OR 97333
EPA/600/ 3-90/074
August, 1990
Research and Development
q EDA Response of Forest Trees to Sulfur, Nitrogen, and
^ Associated Pollutants •
Forest Response Program
Major Program Output #4
C/
United States
Environmental Protection
Agency
United States
Department of Agriculture
Forest Service
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EPA/600/3-90/074
August, 1990
Response of Forest Trees to Sulfur, Nitrogen,
and Associated Pollutants
by
Kim G. Mattson,1 Lynn Y. Arnaut,2 Gregory A. Reams,3
Steven P. dine,2 Charles E. Peterson,2 and Richard J. Vong3
1University of Idaho
2NSI Technology Services, Inc.
'Oregon State University
US EPA Environmental Research Laboratory
Corvallis, OR 97333
Project Officer
Roger Blair
US EPA Environmental Research Laboratory
Corvallis, OR 97333
Hie Forest Response Program is a cooperative program of the
US Environmental Protection Agency and the USDA Forest Service with support from
the National Council of the Paper Industry for Air and Stream Improvement, Inc.
Environmental Reseach Laboratory
US Environmental Protection Agency
200 SW35th Street
Corvallis, OR 97333
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ABSTRACT
The National Acid Precipitation Assessment Program created the Forest Response Program
(FRP) to assess the effects of acidic deposition on trees and forests in regions of the United States.
Research from the FRP and other programs is summarized in four Major Program Output
documents that address policy questions regarding forest condition, mechanisms of effects of air
pollutants, and projected responses of pollutants on forests. This document summarizes infor-
mation available up to February, 1990.
The major findings include several observations on mechanisms of effect. There is evidence that
supports the hypothesis that acidic deposition alters soil chemical properties. The rate of changes
in soil chemical properties and how trees may respond to the changes is not certain. Controlled
exposures of simulated acid precipitation most often showed no effect on growth of seedlings,
but caused delayed development of cold tolerance in red spruce seedlings Ozone caused
decreased growth in most seedlings tested, but at levels higher than typical ambient ozone
concentrations. Species that may be sensitive to ozone at ambient levels include ponderosa pine
and loblolly pine.
The findings allow conclusions regarding consistency between forest condition and pollutant
levels in several regions of the United States. Observations of foliar injury symptomatic of ozone
exposure on ponderosa pine and Jeffrey pine in the San Bernardino Mountains and in the Sierra
Nevada of California are spatially and temporally consistent with measured increases in average
ozone concentrations. Hie number of standing dead red spruce in the Adirondack and Green
Mountains of the northern Appalachians increases with elevation. At elevations above cloud
base (800-1200 m), atmospheric deposition of adds and acidiiying substances is estimated to be
twee that below cloud base. There is consistency between soil chemical properties or nutrient
cycling properties and spatial trends of atmospheric deposition of sulfate and associated ions in
the eastern hardwoods region. However, change in forest condition associated with the atmos-
pheric deposition patterns in the eastern hardwoods is not pronounced. Some reduction in radial
growth of oak has been observed on sites with low soil calcium-to-aluminum ratios. Although
decreased radial growth of loblolly pine in natural stands growing in the Piedmont region of the
South has been observed in recent years compared with earlier years, consistency with ozone
levels cannot be established since exposures of these stands to ozone has not been quantified.
The decrease in radial growth in the stands of loblolly pine is also related to recent increases in
stem density and increased age of the trees.
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NOTICE
The research of the Forest Response Program described in this report is a part of the National
Acid Precipitation Assessment Program and has been funded by the US Environmental Protec-
tion Agency (EPA) and the USDA Forest Service, with support from the National Council of the
Paper Industry for Air and Stream Improvement, Inc. This document has been prepared at the
EPA Environmental Research Laboratory in Corvallis, OR, through cooperative agreement
CR-814667 with the University of Idaho. It has been subjected to the EPA's peer and administra-
tive review and approved for publication. Mention of trade names or commercial products does
not constitute endorsement or recommendation for use.
u
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MPO#4 FRP FOREST EFFECTS REPORT MATTSON ET AL.
TABLE OF CONTENTS
1 EXECUTIVE SUMMARY 1
LI Policy Question #1 1
1.1.1 Acidic Deposition 1
LL2 Ozone 2
L2 Policy Question #2 2
L2.1 Soils 2
122 Roots and Myconhizae 3
1.2.3 Carbon Allocation 3
L2.4 Winter Injury 3
125 Foliar Leaching 3
13 Conclusion 3
2 INTRODUCTION .5
2.1 Forest Response Program 5
22 Purpose of this Document 8
23 Background and Statement of the Problem 8
2.4 FRP Research Methods 9
25 Summary of MPO#l&2 9
23.1 Changes in Forest Condition 10
252 Spatial Patterns in Forest Condition and Pollutant Exposure 10
2.6 Summary of MPO #3 10
2.6.1 Effects of Sulfur Dioxide 10
2.6.2 Effects of Acidic Deposition 10
2.6.3 Effects of Ozone 11
2.7 Summary of Atmospheric Deposition and Pollutant Exposure 11
26 Ozone Exposure 16
3 RESULTS AND DISCUSSION 21
3.1 Soil Chemistry and Nutrient Cycling 22
3.1.1 Trends Along Regional Deposition Gradients 22
3.12 Trends Along Elevational Gradients of Cloud Deposition 28
3.13 Experimental Additions of Acidic Solutions to Soils ' 31
3.L4 Literature Renews and Modeling Projections 34
3.L5 Tree Condition as a Function of Soil Chemistry 34
3.L6 Soil Studies of Other Programs 35
3.1.7 Summary 41
3 2 Roots and Mycorrhizae 42
3.2.1 FRP Seedling Studies 42
322 FRP Mature Tree Studies 43
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3.23 NCASI Results 43
3.2.4 ROPIS Results 43
3.2.5 Summary 44
33 Altered Carbon Allocation 44
33.1 FRP Seedling Studies 44
332 FRP Mature Tree and Sapling Field Studies 48
333 FRP Branch Exposure Studies 49
33.4 ROPIS Results 31
33.5 Summary -54
3.4 Winter Injury -54
3.4.1 FRP Seedling Studies .54
3.42 FRP Mature Tree and Sapling Field Studies .56
3.4.3 ROPIS Results 36
3.4.4 Summary .58
33 Foliar Leaching 38
3.5.1 FRP Seedling Studies 38
33.2 FRP Mature Tree and Sapling Field Studies 38
333 IFS Results 59
33.4 ROPIS Results 39
333 Summary 39
3.6 Insects and Pathogens 39
3.7 Reproduction and Regeneration 62
3.8 Forest Condition Studies 63
3.8.1 Western Conifers 63
3.8.2 Spruce-Fir 63
3.83 Southern Commercial Pines 65
3.8.4 Eastern Hardwoods 65
3.83 Summary 66
4 SUMMARY AND CONCLUSIONS 67
4.1 Purpose of this Document 67
4.2 Summary of Principal Findings 67
4.2.1 Soils 67
4.2.2 Roots and Mycorrhizae 68
423 Carbon Allocation 68
4.2.4 Winter Injury 68
4.2.5 Foliar Leaching 69
4.2.6 Forest Condition 69
43 Answers to Policy Questions 70
43.1 Acidic Deposition 70
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432 Ozone 71
4.4 Recommendations for Future Research 71
4.4.1 Soils 71
4.4.2'Roots 72
4.4.3 Carbon Allocation 72
4.4.4 Winter Injury 72
4.4.5 Foliar I caching 72
4.4.6 Forest Condition 72
4.4.7 Atmospheric Deposition 73
4.4.8 Controlled Exposure Studies . 73
5 ACKNOWLEDGMENTS 74
6 LITERATURE CITED 75
7 APPENDICES 90
7.1 Appendix A; Assessment of Data Quality 90
7.1.1 Use of Data Quality Assessments 90
7.1.2 Quality Assurance Activities 90
7.13 Quality Assurance Findings 91
7.1.4 Quality Assurance of Branch Exposure Chambers 92
72 Appendix B: Methods and Materials 97
7.2.1 Forest Condition Surveys . . . ,. 97
722 Atmospheric Deposition Data 99
723 Controlled Exposure Studies 100
13 Appendix C: Abbreviations 103
7.4 Appendix D: Scientific Names of Trees 104
IS Appendix E: Summary Tables of FRP Research 105
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1 EXECUTIVE SUMMARY
The Forest Response Program (FRP) is a cooperative research program of the US Environmental
Protection Agency, the USDA Forest Service, and the National Council of the Paper Industry
for Air and Stream Improvement, Inc., initiated under the National Add Precipitation Assess-
ment Program. The purpose of the FRP is to determine the nature and extent of the effects of
acidic deposition and associated pollutants on trees and forests in regions of the United States.
This document is one of a series of Major Program Outputs (MPOs) that summarizes research
from the FRP and other programs and that addresses questions relevant to environmental policy.
The purpose of this document (MPO #4) is to address two policy questions posed at the initiation
of the FRP:
L Is there significant forest damage in North America caused by acidic deposition, alone or
in combination with other pollutants?
2. By what mechanisms does acidic deposition, alone or in combination with other
pollutants, contribute to forest damage in North America?
1.1 Policy Question #1
In this section, we summarize research on forest condition to evaluate whether there is significant
forest damage in North America that may have been caused by acidic deposition. Because ozone
is the most widespread phytotoxic air pollutant found in forested regions, we also summarize
research designed to determine how ozone may be affecting forest condition.
1X1 Acidic Deposition
Significant forest damage (change greater than expected) is thought to be occurring among red
spruce at high elevations in the Appalachian Mountains of the northeastern United States based
on three observations of forest condition: 1) high proportions of standing dead red spruce basal
area above 1000 m in the Adirondack and Green Mountains; 2) reductions in radial growth of
red spruce in many areas; and 3) tree condition visually assessed to be poor or declining over
time. The range of possible natural variation in forest condition is quite large. The observed
changes in red spruce at high elevations may not be outside the range of natural variability, but
it does appear that they are above normal expectation and are consistent with increasing levels
of wet deposition. In addition, experiments with red spruce have linked acidic mists to decreased
cold tolerance in seedlings and ambient cloud water to increased winter injury to mature
branches. Winter injury has been associated with reduced red spruce growth in a field
provenance study. These experimental and field observations are consistent with the hypothesis
that repeated winter injury, exacerbated by high levels of acidic cloud water deposition, may
contribute to reduced radial growth and deteriorated crown condition in red spruce. To date,
however, no experimental evidence has demonstrated conclusively that acidic deposition is a
direct cause of increased mortality of red spruce.
Significant forest damage has not been detected in the eastern hardwoods. No relationship has
been established between biomass increment and spatial patterns of sulfate deposition in
Michigan. However, reduced radial growth has been observed in black and white oaks on sites
with low soil calcium-to-aluminum ratios (025 molar ratio in the upper SO cm of soil) in the Ohio
River Valley.
1.12 Ozone
Ozone has been shown to cause foliar injury, decreased growth, and increased mortality of
sensitive individuals of specific forest tree species. Ozone has caused foliar injury to sensitive
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individuals of white pine over much of its range in eastern North America. Ozone has also
resulted in reduced growth of sensitive white pines in the Blue Ridge Mountains of Virginia and
in a plantation in eastern Tennessee. In addition, ozone has caused foliar injury, reduced needle
retention, decreased photosynthesis, and reduced growth eventually leading to increased mor-
tality (caused by the western pixie beetle) of ponderosa pine and Jeffrey pine in the San
Bernardino Mountains in southern California. There is spatial consistency between ozone
exposure and symptomatic crown injury to mature ponderosa pine along a 500-km north-to south
corridor in the southern Sierra Nevada. Ozone occurs in concentrations sufficient to cause visible
injury to vegetation in most of eastern North America.
Ozone may be causing growth reductions in southern pines, although no data directly
demonstrate this. Three observations support this conjecture: 1) in selected instances, loblolly
pine seedlings and mature branches of loblolly pine show reductions in photosynthesis at ambient
ozone levels (i.e., 40-50 ppb); 2) a reduction in radial growth of loblolly pine has been observed
in natural stands in the Piedmont; and 3) potentially phytotoxic levels of ozone have been
measured in this region (43-51 ppb). However, other information limits this conjecture. A
number of the seedling studies did not show reductions in photosynthesis at ozone levels twice
ambient. The reductions in growth in loblolly pine stands may be due to natural factors, since
stand density changes and increased competition from hardwoods have not been accounted for
in these surveys. Until these uncertainties are resolved, ozone-induced growth declines of loblolly
pine in the South cannot be established.
12 Policy Question #2
Scientific questions were posed at the beginning of the FRP to address Policy Question #2; that
is, to determine mechanisms for forest damage due to acidic deposition. Possible mechanisms
for forest damage identified in these scientific questions include changes in soil chemistry/effects
on roots and mycorrhizae, altered carbon allocation, winter injury, foliar leaching, insects and
pathogens, and filtered reproduction and regeneration. Research projects designed to answer
the scientific questions included surveys of forest condition, dendroecological studies, charac-
terization of pollutant deposition, controlled exposures of seedlings and branches of mature trees
to pollutants, soil studies, and forest ecological studies along deposition gradients. The answers
to the scientific questions based on the research presented in this document can be summarized
as follows.
12.1 Soils
Several observations support the hypothesis that atmospheric deposition of acidic or acidifying
substances such as hydrogen, sulfate, nitrate, and ammonium ions alters soil chemical properties.
Changes in soil chemistry similar to those that would be expected as a result of soil acidification
were observed along four regional gradients of increasing sulfate deposition in eastern hardwood
forests. When compared with lower elevations on ML Moosilauke, NH, and Whiteface Moun-
tain, NY, changes in soil chemistry under red spruce were observed at high-elevation sites where
deposition of sulfate is high due to high cloud water deposition. Two analyses of the extent of
susceptible soils and acidic deposition in the Southeast indicated that loss of soil cations and
increases of soil nitrogen will occur in some soils. The timing of this change is uncertain. Soil
chemical changes induced by artificial additions of acid were consistent with trends observed in
the Geld.
122 Roots and Mycorrhizae
Responses of seedling root growth to simulated acid precipitation were highly variable. No
consistent effects of acidity on growth or mortality of roots were evident in these studies.
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Root growth of loblolly pine, trembling aspen, Douglas-fir, ponderosa pine, and lodgepole pine
seedlings was reduced by ozone. A possible mechanism appears to be reduced carbon allocation
to roots.. Mycorrhizal frequency,may be reduced and morphotype distributions may be altered
by ozone; however, this work is still preliminary.
123 Carbon Allocation
In seedling studies, tested levels of acidity ranged from pH 2.1 to 5.6, with typical values from
pH 3.0 to 5.0. Compared with control treatments (Le, the highest pH value used), overhalf the
studies showed no effects of increased acidity onfoliage.biomass, stem growth, or root growth.
The remaining , studies showed both increased .growth and decreased growth. ^ Increased
photosynthesis of seedlings in treatments with increased acidity of simulated acidic precipitation
was observed m some studies of red spruce and,southern pines.
Ozone exposures of wiling* ranged from charcoal-filtered air to 320 ppb, with typical values
ranging from charcoal-filtered to 3-times-ambient concentrations, or about 120 ppb (ambient site
concentrations ringed from 33.to 48 ppb). Compared with control treatments (die lowest ozone
level), ozone exposure led to decreased growth in most studies. Loblolly pine, ponderosa pine,
western hemlock, and black cherry showed decreases in above- and/or belowground growth. In
addition, loblolly pine also showed reduced photosynthesis. Photosynthesis was hot measured
for ponderosa pine, western hemlock, or most hardwood species.
12.4 Winter Injury
In controlled tests of simulated acidic precipitation, increasing acidity decreased the rate of
development of cold tolerance of red spruce seedlings. The response was fairly linear as acidity
increased, starting as high as pH 4.0. Solutions containing sulfuric acid caused greater injury
following overnight freeze tests than solutions containing nitric acid. When cloud water contain-
ing ambient concentrations of pollutants was filtered from branch exposure chambers, freezing
injury decreased for branches of mature red spruce in the field on Whiteface Mountain, NY.
Reductions in radial growth, basal area increment, and height growth were associated with degree
of over-winter injury to needles of 30-year-old red spruce trees growing in a provenance test site
in northern New Hampshire.
U5 Foliar Leaching
Precipitation addity can increase foliar leaching, but the effects of canopy leaching on tree growth
and health are unclear. In chamber exposures, most studies showed no effect of acidity on foliar
nutrient levels. In the field, hydrogen ion loading arid throughfaU enrichment of cations were
correlated in all of the reviewed studies, indicating a possible effect of precipitation acidity.
1J Conclusion
Damage to red spruce has been identified at high elevations in the northern Appalachians. At
the highest elevations, acidic cloud water deposition and odd temperatures are greatest, and, in
the Adirondack and Green Mountains, red sphice mortality and deteriorated crown condition
is greatest Three; experimental findings support thehypothesis that reduced growth and crown
deterioration of red spruce is related to winter injury,' which may be increased by chronic
deposition of acidic doud water. First,-controlled exposures of acidic precipitation caused
reduced cold tolerance to current-year needles of red spruce seedlings during autumn hardening.
Second, reduced exposure to ambient doud water was associated, with decreased winter injury
to needles on branches of susceptible mature red spruce trees. Third, damage to needles in winter
has been related to reduced carbon gain (shown as reduced height and diameter growth) in
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30-year-old red spruce trees growing in a provenance study plot. Whether acidic cloud water can
cause sufficient winter injury to lead to increased red spruce mortality is still to be determined.
Changes in forest condition (visible foliar injury or reduced growth) of some species sensitive to
ozone have been identified in regions that may have relatively high ozone exposures. In particular,
ponderosa pine in the San Bernardino Mountains and in the Sierra Nevadas of California have
shown changes in forest condition. The condition of loblolly pine in natural (i.e., unman aged)
stands of the Piedmont may also have changed. However, the relationship between spatial and
temporal distributions of ozone in the Piedmont and forest condition are as yet to be determined.
Controlled exposures indicate that high levels of ozone cause reduced photosynthesis, reduced
growth, reduced carbon allocation to roots, and increased foliage senescence in many species of
seedlings, and ponderosa, Jeffrey, and loblolly pine appear to be particularly sensitive. Ozone
has also been associated with reduced photosynthesis in mature loblolly pine. The effects of
ozone on mature ponderosa pine are currently being studied using branch exposure chambers.
Soil chemical properties have been shown to change with controlled applications of acidic
precipitation. Chemical properties of the soil and forest floor, such as exchangeable cations
(notably calcium and magnesium), available aluminum, or sulfur contents, and nutrient cycling
properties, such as nitrification, or chemistry of foliage and wood of trees, vary spatially in a
manner consistent with patterns of acidic deposition. How such changes in soil chemical
properties may be affecting trees in the forests is still under study. However, reduced growth of
red spruce seedlings have been observed at soil solution aluminum (Al3+) concentrations as low
as 200fi M. These concentrations have been measured in association with high soil solution nitrate
concentrations in red spruce stands at Whitetop Mountain, VA.
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2 INTRODUCTION
The Forest Response Program (FRP) is a research initiative under Task Group V of the National
Add Precipitation Assessment Program (NAPAP). The FRP is responsible for estimating the
actual and potential effects of acidic deposition and its associated pollutants on trees, forests,
and forest ecosystems in regions of the United States (Schroeder and Kiester, 1989). This
document reviews and summarizes research performed by the FRP and other programs.
2.1 Forest Response Program
The FRP is a joint program of the US Environmental Protection Agency (EPA), the USDA
Forest Service (USFS), and the National Council of the Paper Industry for Air and Stream
Improvement, Inc. (NCASI). The FRP was created in 1985 in an effort to consolidate into a
national research program several separate programs that were collecting data on forests and
acid rain. The objective of the FRP is to address three policy questions regarding the status of
North American forests, the potential and actual effects of acidic deposition, mechanisms of the
effects, and quantification of the effects.
The three policy questions are:
1. Is there significant forest damage in North America caused by acidic deposition, alone or
in combination with other pollutants?
2. By what mechanisms does acidic deposition, alone or in combination with other
pollutants, contribute to forest damage in North
America?
3. What is the dose-response relationship between acidic deposition, alone or in
combination with other pollutants, and forest damage in North America?
The FRP is organized into six research cooperatives with a national management structure. The
six research cooperatives are responsible for managing research in identified problem areas.
Four research cooperatives are organized according to forest regions. The Spruce-Fir (SF)
Research Cooperative focuses primarily on red spruce and, to a lesser extent, balsam fir and
Fraser fir in high-elevation spruce-fir forests of the Appalachian Mountains. The Southern
Commercial (SC) Forest Research Cooperative studies commercially important pines of the
southern states. The Eastern Hardwoods (EH) Research Cooperative examines hardwood
species primarily in midwestern and northeastern states. The Western Conifers (WC) Research
Cooperative studies conifer species in western states. The two remaining research cooperatives
were organized to facilitate the collection and assembly of data sets: the National Vegetation
Survey (VS) is concerned with inventories of forests conducted primarily through dendrochronol-
ogy or surveys of permanent plots, and the Atmospheric Exposure (AE) Cooperative established
pollutant deposition monitoring sites and developed cloud water collection techniques. The FRP
also included two program-wide projects: Quality Assurance (QA), which is concerned with data
integrity, and Synthesis and Integration (S&I), which provides technical support to the coopera-
tives and produces program-wide summaries such as this document.
At the beginning of the FRP, a series of scientific questions (Table 1) was formulated for each
policy question to guide the research. As individual research projects progressed, the
investigators' analyses of their data were made available to S&I. S&I was then responsible for
producing documents called Major Program Outputs (MPOs) to answer the scientific and policy
questions by synthesizing and integrating results across individual experiments where possible
(see Table 2 for a list of these MPOs). The MPOs have two purposes: 1) to summarize FRP
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research for the scientific community, and 2) to answer the policy questions to the extent possible.
The path from problem statement to research projects and MPOs is summarized in Figure 1.
Table 1. Original Scientific Questions of Policy Questions #1 and #2
Scientific Questions for Policy Question #1
1. Are changes in forest condition greater than can be attributed to natural variability?
2. What spatial patterns exist in forest condition and how do they relate to spatial patterns
of pollutant exposure?
Scientific Questions for Policy Question #2
What are the effects of sulfur, nitrogen, and associated pollutants on forests through the
mechanisms of:
1. a. direct toxicity to roots, mycorrhizae, or soil microbial populations by mobilized metal
in acidified soil water;
b. nitrogen toxicity to mycorrhizae; or
c. increased leaching of soil nutrients resulting in reduced nutrient availability?
2. altered photosynthesis, respiration, and carbon allocation patterns (e.g., morphology)
with possible induction of water and/or nutrient stress?
3. delayed cold hardening or premature break in dormancy resulting in increased winter
Table 2. Major Program Outputs, Associated Policy Questions, and Authors
MPO #1&2:
Extent and magnitude of recent changes in forest condition and the role
of air pollution and non-air pollution factors. (Policy Question #1)
(Reams et al., 1990)
MPO #3:
Seedling response to sulfur, nitrogen, and associated pollutants. (Policy
Question #2)(Peterson et al., 1989)
MPO #4:
Response of forest trees to sulfur, nitrogen, and associated pollutants.
(Policy Questions #1 and #2)(Mattson et al., 1990)
MPO #5:
Projection of responses of trees and forests to acidic deposition and
associated pollutants. (Policy Question #3)(Kiester et al., 1989)
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Co-occurrence?
Widespread
pollution
Perception of
forest decline
Major Program Outputs (MPOs)
Coop-level synthesis (case studies,
symposia, workshops)
Modeling efforts
FRP Environmental Policy Questions developed:
L Extent of change in forest condition
2. Causal relationship between forest
condition and pollutants
3. Exposure-response relationship
> 100 individual research projects funded
1. Surveys of forest condition
2. Atmospheric chemistry
3. Seedling exposures
4. Intensive field studies
5. Literature reviews
6. Model development
Scientific Questions developed:
For Policy Question #1:
L Are changes in forest condition greater than
can be attributed to natural variability?
2. What special patterns exist in forest
condition and how do they relate to spatial
patterns of pollutant exposure?
For Policy Question #2:
What are the mechanisms of the relationship?
L Soil-mediated effects
2. Increased foliar leaching
3. Altered carbon allocation
4. Increased winter injury
5. Altered reproduction/regeneration
6. Effects of insects/pathogens
Problem
Definition
Research
Answers
Figure 1. The path from problem statement to research synthesis in the FRP.
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22 Purpose of this Document
The purpose of this document (MPO #4) is, first, to summarize FRP research that was conducted
to answer Scientific Questions 1 through 6 for Policy Question #2 and, second, to provide answers
to Policy Questions #1 and #2. In meeting these objectives, we also review the findings of
MPO #1&2 and MPO #3 since these documents incorporated many of the FRP studies
discussed here and they attempted to answer aspects of Policy Questions #1 and #2.
23 Background and Statement of the Problem
Forest decline is defined as a response to one or more stresses, resulting in a decrease in the vigor
of individuals of one or more tree species and often in increased mortality rates over a large area
(Freedman, 1989; Weidensaul et a!., 1989). Changes in forest condition can result from natural
factors, such as stand dynamics, climate, insects, and pathogens, and from anthropogenic factors,
such as harvesting, site preparation, and atmospheric deposition. These factors can act alone or
in combination. In this section, we briefly review evidence from regions in Europe and North
America that led to a perception of forest decline. For a more comprehensive historical
perspective, see Brandt (1987) or Reams et al. (1990).
Concern over effects of air pollutants and acid rain dates back more than a century. In 1852,
Smith described the chemical composition of rain and related increasing acidity in precipitation
to industrial coal combustion (cited in Brandt, 1987). In 1871, Stockhardt related changes in plant
growth to pollutants when he attributed spruce and fir injury to sulfur dioxide from a smelter
(cited in Brandt, 1987). In 1955, Gorham stated that acidic precipitation could acidify lakes,
streams, and soils (cited in Binkley et al., 1989).
In the early 1970s, chlorosis and crown-thinning of silver fir in southern forests of the Federal
Republic of Germany were reported (Brandt, 1987). The symptoms typically progressed from
defoliation to death. In the mid-1970s, similar symptoms were observed in widely distributed
stands of Norway spruce. Damage to deciduous trees (European beech and oak) has also been
observed since 1981. In the 1970s, because of concern over both this apparent new decline (i.e.,
affecting many species) and the potential effects of acid rain on aquatic systems, attention focused
on acidic deposition as the primary cause. More recently, other contributing factors have been
suggested, such as soil and foliar nutrient deficiency, tree harvesting, pathogenic fungi, and
drought (Blank et al., 1988).
From 1980 to 1984, reports of spruce disease have also come from other parts of central Europe,
southern Scandinavia, and northern Italy (United Nations Environment Program, 1987). Initial
projections of increasing damage leading to destabilization of forest ecosystems have not been
supported (Blank et al., 1988).
In North America, Packard reported in 1884 on spruce mortality that was due to insects in New
York and Maine. According to Blais (1983), spruce budworm outbreaks in eastern Canada have
occurred periodically for 300 years. He related increased outbreak severity to human interven-
tions such as clearcutting, fire protection, and pesticides.
Surveys of spruce-fir forests at high elevations (above 800 m) in the northern Appalachian
Mountains in the late 1960s and early 1970s indicated either declines in growth rates or increases
in mortality of red spruce and balsam fir (Johnson and Siccama, 1983; Scott et al., 1984;
Vogelmann et al., 1985). At lower elevations over most of the northeastern United States, a
decline in radial increment of red spruce beginning about 1960 was also reported (Hornbeck and
Smith, 1985). A similar growth-trend decline since the 1960s has been reported for red spruce
in the mid-Appalachians (Adams et al., 1985) and southern Appalachians (Bruck, 1984; Mc-
Laughlin et al., 1987). With respect to moitality observed in the southern Appalachians, most
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was Fraser fir that had been killed by the balsam woolly adelgid (Johnson and Siccama, 1983;
Bruck et aL, SF02-2; Zedaker et aL, SF25-4).
Average annual radial growth rates of southern pines less than approximately 41 cm (16 in) in
diameter have declined 30% to 50% over the past 30 years (Sheffield et aL, 1985). This decline
was reported for natural stands in the Piedmont'and mountain regions of South Carolina, the
Piedmont region of Georgia, and coastal plain areas of Georgiaand South Carolina.
Millers et aL (1989) reviewed mortality in eastern hardwood forests over the last century. They
reported that many species showed declines and mortality and that the incidence has increased
in the last few decades. Most mortality could be attributed to weather, silviculture, or insects and
pathogens, and the increase in reports of decline was attributed to more consistent reporting and
forest Saturation.
Miller(1984) related increased mortality of ponderosa and Jeffrey pine to ozone concentrations
in the San Bernardino Mountains of California. Recent trends of tree condition in the San
Bernardino National Forest indicate decreased crown injury. Ponderosa and Jeffrey pine have
shown visible symptoms of damage in the Sierra Nevada Mountains; the growth index of
large-diameter Jeffrey pine growing:on poor sites exposed to ozone has decreased 11% since
1965 (Peterson et aL, 1987).
2.4 FRP Research Methods
Most of the research funded by the FRP began during the summer of 1986. The research
presented in MPO #1&2, MPO #3, and in this document used two conceptual approaches to
address the policy questions: epidemiological and physioIogicaL
The epidemiolojjpul approach is characterized by surveys of forest condition conducted to
identify patterns that may be related to atmospheric deposition or other environmental factors.
This approach addresses Policy Question #1, and, indirectly, Policy Question #2. Several types
of epidemiological studies were funded by the FRP, including surveys of forest growth, mortality,
and crown condition, dendroecological studies, and atmospheric deposition monitoring: Air
quality measurements were.also made at a number of sites.
The physiological approach is characterized by expierimental studies of. the effects of particular
environmental variables on the health of individual trees or stands, and it addresses Policy
Question #2. The physiological studies were primarily controlled exposures of pollutants on
experimental material to identify correlations and to test the hypothesized mechanisms of cause
and effect Tree seedlings were the most common experimental material, but branches of mature
trees, mycofrhizae, and forest soils were also studied. Treatments were applied under varying
environmental conditions ranging from growth chambers to open-top field chambers to field
manipulations. Growth responses and physiological effects were determined for a wide range of
tree species in relation to quantified exposures of pollutants.
25 SummaiyofMPO #1&2
In MPO #1&2, Reams et al. (1990) addressed the two scientific questions of Policy Question #1:
1) whether recent changes in forest condition are Cheater than what would be expected from
natural variability; and 2) whether spatial patternsfin forest condition are related to spatial
patterns of pollutant exposure. Reams et al. concluded that in two forested areas studied by the
FRP, significant changes in'forest condition maybe related to pollutant exposure. In this section,
we present the conclusions of Reams et aL regarding the status of forests and spatial patterns in
forest condition and pollutant exposure.
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FRP FOREST EFFECTS REPORT
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2.5.1 Changes in Forest Condition
In answering the first scientific question based on the research presented in MPO #1&2, two
regions were identified as showing changes in forest condition. First, the incidence of ponderosa
pine foliar injury in the southern Sierra Nevada of California is greater than would be expected
from natural sources of variability. Second, in the Northeast, high-elevation red spruce showed
increased mortality in the 1960s. However, it is not known if the proportion of standing dead red
spruce is outside the range of natural variability.
2£2 Spatial Patterns in Forest Condition and Pollutant Exposure
To most effectively evaluate the second scientific question, Reams et al. concluded that both
forest condition and deposition levels should be known at the location of interest. Since
deposition monitoring typically is not conducted at the same sites at which forest condition is
assessed, pollutant levels at the forest plots of interest had to be estimated. Reams et al. suggested
that the variability of these estimates is either unknown or quite large, such that only plots that
are a great distance apart have significantly different estimated deposition levels. Identification
of spatial patterns in deposition over time was further limited because historical data extend back
only to the late 1970s, and patterns vary greatly from year to year. Thus, there has been limited
success in answering the second scientific question.
These problems notwithstanding, spatial patterns of changes in forest condition and increased
pollutant exposure were determined to exist in the two regions identified in answering the first
scientific question. In the southern Sierra Nevada of California, injury to ponderosa pine needles
is consistent with symptoms typical of ozone injury, and injury is found in areas with elevated
levels of ozone. Second, the percentage of red spruce standing dead basal area increases with
increasing elevations in the Adirondack and Green Mountains of the northern Appalachians.
These increases are consistent with increasing levels of wet deposition.
2.6 Summary of MPO #3
In MPO #3, Peterson et al. (1989) summarized the results of controlled exposures of sulfur
dioxide, simulated acidic deposition, and controlled exposures of ozone on seedlings conducted
by the FRP through 1988. Peterson et al. concluded that although there are currently no data on
the long-term effects of multi-year pollutant exposures on seedlings, differential changes in above-
versus belowground biomass in response to short-term pollutant exposures indicate long-term
problems for seedlings. Under chronic exposure, eventual tree productivity or survival could be
affected. In this section, we summarize the conclusions of MPO #3.
2.6.1 Effects of Sulfur Dioxide
Increased concentrations of sulfur dioxide (up to 66 ppb) caused several changes in growth and
carbon allocation patterns during controlled exposures using western conifer seedlings. Changes
included increased aboveground growth for Engelmann spruce, white fir, western red cedar, and
Douglas-fir; reductions in root biomass and root/shoot ratios for Douglas-fir, ponderosa pine,
and lodgepole pine; and increased bud elongation for ponderosa pine, Douglas-fir, western
hemlock, and western red cedar. The altered post-exposure growth and imbalance in above- and
belowground responses indicated changes in carbon allocation patterns.
2.62 EfTects of Acidic Deposition
The clearest response to increased acidity was reduced frost hardiness of current-year needles
in red spruce seedlings. The seedlings were exposed to simulated acidic mists during the growing
season, and twigs were exposed to simulated frosts during the autumn hardening period.
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MPO#4
FRP FOREST EFFECTS REPORT
MATTSON ETT AL
Although individual species showed some effects of short-term exposures to simulated acidic
deposition, these results cannot be generalized for all species tested. For example, growth of
black cherry was decreased by pH 3.0 versus 42. Furthermore, increased aboveground growth
coupled with no apparent effects on belowground biomass in western conifers at pHZl compared
with pH 5jS indicated changes in carbon allocation patterns. Most of the species that were tested
at pH levels below 3.0 showed some visible injury.
2j63 Effects of Ozone
The direct effect of ozone varied from suppressed growth of loblolly pine, ponderosa pine, and
some hardwood species to physiological changes in the foliage of red spruce. Stem and root
growth of loblolly pine was reduced at 80 ppb or higher. At intermediate levels (40 to 80 ppb)
results were more variable, and it was not uncommon for growth rates to be greater than those
in charcoal-filtered air. Net photosynthetic rate of loblolly pine showed cumulative decreases in
response to increased exposure to ozone. Several growth measures of ponderosa pine were
reduced while most other western conifer species showed increased growth rates at levels less
than 100 ppb. Ponderosa pine, white fir, subalpine fir, and western hemlock also showed visible
injury in response to ozone at 70 ppb. Growth of black cherry, white oak, red maple, and yellow
birch was reduced at concentrations above 70 ppb. Yellow-poplar, white ash, and red oak
displayed no growth response at the same levels. Most eastern hardwood species showed visible
injury with exposure to ozone of 70 ppb or higher. Yellow-poplar, yellow birch, sweetgum, red
maple, white ash, and black cherry appeared to be the most sensitive to foliar injury of the species
tested. Damage to foliar mesophyll cells, decreased photosynthetic pigments, and seasonal
changes in photosynthesis in red spruce occurred in response to ozone at 40 ppb and higher.
2.7 Summary of Atmospheric Deposition and Pollutant Exposure
Networks of monitoring sites have been established to characterize the concentration and
deposition of atmospheric pollutants in forests. The principal monitoring networks in the United
States are the National Atmospheric Deposition Program/National Trends Network
(NADP/NTN) and the Mountain Cloud Chemistry Program (MCCP) of the Atmospheric
Research Cooperative. Figures 2 and 3 present pH and sulfate (SC>42~) wet deposition for the
United States. Dry deposition (and cloud deposition at high elevations) can add considerably
more total sulfur (S) deposition than that shown in Figure 3. For example, dry S deposition
accounted for 40% to 60% of total S deposition at low-elevation forested sites in the southeastern
United States and for 10% to 40% at most other low-elevation forested sites in North America
(Lindberg, 1989). At a high-elevation forest site in the Smoky Mountains, NC, and a high-eleva-
tion forest site at Whiteface Mountain, NY, approximately 50% of total SO42' deposition was due
to cloud water interception by the forest canopy (lindberg, 1989).
Hie MCCP consists of one low-elevation monitoring site at Howland, ME, and five high-elevation
sites that experience frequent cloudiness: Whiteface Mountain, NY, Mt. Moosilauke, NH,
Shenandoah, VA, Whitetop Mountain, VA, and Mt. Mitchell, NC (see Figure 4). The data
collected include cloud water concentrations of the following ions: SO4 , nitrate (N03*)< chloride
(CT), hydrogen (H+), ammonium (NH4*), sodium (Na+), magnesium (Mg2*), potassium
(K+), and calcium (Ca2+). At all sites, liquid water content is measured; aqueous hydrogen
peroxide (H2O2) also is measured in some samples. Data have been collected from April to
October in 1986 through 1988.
Precipitation concentrations of acidifying compounds in the United States are lower (i.e., higher
pH) than levels shown to be harmful to seedlings (see Figures 2 and 5 for data on the concentra-
tions, and MPO #3 for data on seedling exposure). In contrast to precipitation, cloud water
collected at the five MCCP sites had pH levels below 33 from 10% to 40% of cloudy hours. These
11
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MATTSON ETAL.
MPO#4
1986 Annual
PH
Figure 2. Annual volume-weighted mean pH in precipitation for 1986. Note that shading is
different for eastern and western regions (Olsen, 1989).
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MPO#4
FRP FOREST EFFECTS REPORT
MATTSON ETAL
-14.7
-12.4
1986 Annual
Sulfate Deposition
kg ha-1
Figure 3. Annual SO42" wet deposition via precipitation for 1986 (kg/ha). Note that shading
is different for eastern and western regions (Olsen, 1989).
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FRP FOREST EFFECTS REPORT
MA1TSONETAL
Whiteface
Shenandoah
Whitetop
Mitchell
Figure 4. Land areas above mean cloud base in the eastern United States that receive
significant cloud droplet deposition. (High-elevation MCCP sites are indicated.)
14
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MPO#4
FRP FOREST EFFECTS REPORT
MATTSON ET AL.
I
CN
¦"l"
o
CO
$
tn
c
0
>
a;
c
D
Q_
C/>
c
o
c
D
u
"D
C
a>
>
o
.Q
O
100
80
60
40
20
20
40 100 200 400 600 800 1000 1200 1400
Concentration {fJ. eq/l)
f2 Precipitation
Cloud
Figure 5. Comparison of SO42" concentrations in cloud water and rain water. (Data are from
cloud samples at Whiteface MCCP site and precipitation samples at Whiteface
MAP3S site).
15
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MPO04 FRJ> FOREST EFFECTS REPORT MATTSONETAL.
levels are within the range shown to reduce frost tolerances of red spruce seedlings (Peterson et
al., 1989).
The MCCP results also indicate that chemical deposition to forests is greater at higher elevations
than at lower elevations due to interception of douds. Generally, cloud deposition contributes
a much smaller proportion of input at low elevations than do dry and precipitation deposition.
Two factors regulate the amount of chemical deposition from clouds: the amount of cloud water
deposited and the concentrations of chemicals in the douds. Frequency of doudiness increases
with increasing elevation (see Figure.6). Cloud base height is typically between 800 and 1200 m
in the Appalachian Mountains'(Vong, 1989; Mohnen, 1988a,b). Therefore, high-elevation sites
are reasoned to have greater amounts of deposition than lower elevations. With respect to
chemical concentrations, the aqueous concentrations of the major ions (NH4+, H+, SO42", and
NO3*) typically are higher in douds than in predpitation (see Figure 5) by factors.ranging from
5 to 20, depending on location in the Appalachians.
Increasing doud water interception by forest canopies should occur with increasing doud
frequency (see Figure 7). Comparison of Table 3 with Figure 3 suggests that doud water SO42*
deposition (21 to 140 kg/ha/yr) is often greater than SO42" deposition via predpitation (25 to 35
kg/ha/yr). Cloud water deposition estimates are too uncertain to detect spatial patterns across
peaks within the Appalachian Mountain range. However, a sharp vertical gradient in total
deposition (sum of wet, dry, and doud) exists when:comparing forests below doud base with
those frequently immersed in clouds at one mountain. Therefore, with increasing elevation above
doud base, increasing doud water interception by foliage occurs.
Table 3. Range0 of published estimates of SO42' and water deposition from
intercepted doud water6 (from Vong, 1989; Mohnen, 1988a)
SO42* Water
(kg/ha/mo) (cm/yr)
MCCP Site
Low
High
Low
High
Moosilauke
2
12
18
68
Whiteface
2
11
13
127
Whitetop
8
13
-
25-26
Mitchell
5
10
32
35-77
Shenandoah
1
1
5
9
.Smokies
3
4
15-80
37
a Range is a function of variation in doud frequenaes, elevations, and uncertainties
in the Lovett modd (1984).
b Goud water flux was determined by: 1) a version of the Lovett model (1984); or
2) collecting throughfall under the canopy and correcting for predpitation and
evaporation.
2.8 Ozone Exposure
At rural, low-elevation, forested sites in the northeastern United States, the Great Lakes region,
the Ohio River valley, and the southeastern United States, daytime (0900-1559 hr) average
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FRP FOREST EFFECTS REPORT
MATTSONETAL
100
90
70
60
a)
v>
0
-Q
1 I 80
<_> o
>
X _0J
•1 "
c
CO a)
~c -
5 01 50
CL>
V o
0)
Q_
Whitetop Mtn.
10
Whiteface Mtn.
0
600
_L
700 800 900 1.000 1,100
Elevation (m)
1.200 1,300 1,400
Figure 6. Cloud frequency by elevation during growing season for two MCCP sites. (Total
cloud impaction frequencies at the summits are 28% and 42% of all hours for
Whitetop Mountain and Whiteface Mountain, respectively)(Vong, 1989).
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KRP l-ORI-ST EITIICrS REPORT
MATISON ITI' AL
Code Site
# Mt. Moosilauke, NH
¦ Whiteface Mtn,, NY (WF)
A Whitetop Mtn., VA (WT)
~ Mt. Mitchell, NC
O Shenandoah, VA
>fc Great Smoky Mtns., NC
• Ml. Moosilauke, NH
m
# Mt. Mitchell, NC
Elevation (m)
1220
1483
1220
900
1686
2000
1014
1740
1220
2000
10 20 30 40 50 60 70
Estimated cloud frequency (percent of hours)
Figure 7. Published values for cloud frequency and predicted water interception. The lines
approximately describe this relationship for a site with low liquid water content and
low wind speed (Whitetop Mountain) and high liquid water content and high wind
speed (Whiteface Mountain)(from Hicks et al., 1989).
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FRP FOREST EFFECTS REPORT
MATTSON ETAL
ambient ozone (O3) concentrations during the growing season typically ranged from 35 to 55 ppb
during 1978-1985 (Lefohn and Pinkerton, 1988; Pinkerton and Lefohn, 1987). Peak concentra-
tions over 100 ppb were not unusual. Garner et al. (SOOl-2) reviewed ambient exposure data
from Whiteface Mountain, NY, and stated that similarly high one-hour peak concentrations (i.e.,
100 ppb) have been observed in most years between 1975 and 1984 (Lefohn and Mohnen, 1986;
Molmen, 1987). Garner et aL also noted that because O3 showed little diurnal variation at
high-elevation sites, forests at these elevations are exposed to high O3 concentrations for more
consecutive hours than are forests at low elevations.
Lefohn and Pinkerton (1988) extended their analysis to include sites along the northwest Pacific
Coast. The daytime O3 concentration for this region over the 1978-1985 growing seasons
averaged 31 ppb. However, a more detailed analysis of the western sites for 1980-1987 has been
done by Bohm (1989). Concentrations between 60 and 80 ppb occurred between 5% and 25%
of the measured hours at most sites except those in the Pacific Northwest where O3 is lower. The
Sain Bernardino Mountains in California are exposed to O3 concentrations over 100 ppb during.
10% of measured hours during summer.
Spatial patterns of ambient O3 concentrations across the continental United States for 1978-1983
were produced by kriging as pah of the NAPAP Interim Assessment (Figure 8). Data from the
EPA Storage and Retrieval of Aerometric Data (SAROAD) database were selected to minimize
urban influences. Concentrations were calculated as 7-hr means (0900-1559, local standard time)
for April through October to reflect typical growing season O3 levels. A kriging algorithm was
used to interpolate from the randomly located; sites: to a 0-5° latitude by 0.5° longitude grid
(Reagan, 1984). Areas that did not have monitoring sites within 30 km of at least five stations in
a 500-km^ area were excluded, as was the Los Angeles Basin.
General regional patterns in Figure 8 indicate that areas in southern and central California, the
high desert and intermountain region of the West; and the southcentral East and midwestern
states were more likely to be exposed to elevated O3 levels than were other areas. However, the
patterns in Figure 8 may reflect errors inherent in spatial ^krigjhg, such as violation of the
stationarity assumption (Delhomme, 1978), which assumes that sites located closest to each other
have the most similar concentrations. At present, the high concentrations shown in the much of
the interior West are thought to be somewhat higher than actual.
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FRP FOREST EFFECTS REPORT
MATfSON bTAL
Prepared by Geeercphic D«U SriUmi in Cooperation
with CnTironmcnul Srirncn Division. ORNL
Figure 8. Ambient O3 concentrations (ag/m3) expressed as 7-hr means, for April-October,
1978-1982 (ljUg/m3 of O3 = 0.51 ppb of O3).
20
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MPO#4
FRP FOREST EFFECTS RCPORT
MATTSONETAL
3 RESULTS AND DISCUSSION
To aid b synthesizing the diverse FRP research projects, tables have been prepared to summarize
findings of individual studies. This summary shows the breadth of research and allows the reader
to compare results of studies. Since the tables are long and are referred to repeatedly, they are
located in Appendix E. The reports summarized in the tables vary from published manuscripts
to comprehensive annual reports to briefer research summaries that included only preliminary
interpretations. In the tables and in the body of the report FRP reports, published or
unpublished, are referred to by the first author followed by a repn;.,) umber. The rep, -umber
consists of two letters that indicate the research cooperative that funded the research, the project
number, and a number identifying the report (e^, SF04-5 or EH 12-1). These report numbers
are also included in the Literature Gted section.
The first table (Table 4) summarizes the controlled exposures of acidic precipitation and O3 on
sfifidlingg, The remaining tables group studies of similar types, highlighting the basic methods
and findings of each. The main conclusions of the authors as they pertain to the scientific
questions are listed in boldface. In cases where conclusions were not provided by the authors,
we have provided our conclusions. The authors have reviewed the tables and changes were made
based on their comments.
Table 4 shows the general trend of the seedling response with respect to the control or lowest
level of treatment. We report the response qualitatively as positive (+), negative (-), or no (0)
response. In determining whether a response was positive or negative, our criterion was more
liberal than many of the authors, who typically relied on statistical tests with a =0.05. If a
consistent trend was evident in the data, yet no significant treatment differences were found
(perhaps because the power of the test was low), we report a response and indicate that our
interpretation differed from the authors'. Scanning down a particular column gives an impression
of the overall response of a class of seedlings to acidity or O3. Although this may be less
informative than a quantitative description of response for each individual study, the purpose of
the tables is simply to present general findings from numerous studies that were designed with
different objectives in mind. Individual reports must be referred to for a more complete
description of the response. Alternatively, MPO #3 (Peterson et al, 1989) presents the seedling
responses for individual studies in greater detail for studies up to February, 1989.
Tables 5 through 10 present the results of other research, grouped by type of study (e.g., soils and
nutrient cycling b Table 5 and forest condition studies b Table 7) or by the scientific question
that is bebg addressed (e.gn winter injury findings b Table 8). The tables have a similar format,
showing study type, variables collected, findings, and general interpretations or relevance of the
study. Table 11 lists conclusions from FRP-sponsored literature reviews and syntheses.
The explanation and discussion of results has been organized according to the scientific questions
identified for Policy Question #2. Each scientific question did not receive equal emphasis b the
FRP research projects, and our tables and discussion reflect the emphasis each question received.
We discuss the results b the order of the listbg of the scientific questions b Table 2. For each
question, we first present and discuss FRP findings. We then discuss non-FRP research where
it provides additional information that addresses the question. The non-FRP research was
generally from ongoing programs that parallel the FRP; these include programs funded under
NAPAP, such as the Direct/Delayed Response Program (DDRP), and nongovernmental efforts
by groups such as the Electric Power Research Institute (EPRI) and NCASI.
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FRP FOREST EFFECTS RE!»ORT
MA7TS0NGTAL
3.1 Soil Chemistry and Nutrient Cycling
Soil studies may only indirectly assess whether changes in chemical properties of natural soils can
be caused by atmospheric deposition because no suitable controls are available and because
changes typically occur over long time periods. However, some consensus may be reached by
evaluating several types of studies simultaneously. We examine four types of soil
studies:!) studies conducted along regional atmospheric deposition gradients; 2) studies along
elevation transects where deposition above cloud base (800 to 1200 m in the Appalachian
Mountains) is two times greater than it is below cloud base; 3) experimental additions of acids to
soils; and 4) literature reviews and modeling projections.
3.1.1 Trends Along Regional Deposition Gradients
Along large-scale gradients of increasing SO4 deposition in hardwood forests (compare Figure
9 with Figure 3), four projects have produced data demonstrating that soil chemical properties
or nutrient cycling vary spatially in a manner consistent with spatial patterns of acidic deposition
and associated compounds. These results are discussed briefly in the following paragraphs and
are summarized in Table 5.
Along a gradient of increasing SO42" deposition from western Minnesota to Michigan, in 169 plots
distributed among five forest types, a pattern of increasing S was observed in the soil and in the
organic forest floor lying above the mineral soil (David et al., VS10-7). David et al. observed this
pattern after first adjusting S using nitrogen (N) concentrations as a covariate. Thus, this pattern
in S means that the S:N ratio increases along the deposition gradient. Along this same gradient,
increasing lead (Pb) and cadmium (Cd) in the forest floor were observed (Grigal and Ohmann,
VS10-3). Grigal and Ohmann also observed a decrease in cations in the forest floor along the
gradient of increasing S deposition. However, they believed the cation pattern was more likely
due to wind deposition of soils from more westerly sources.
Increases of S in sugar maple foliage and of S and N in litterfall (Figure 10)(Pregitzer et al.,
EH03-4) and increases in soil S and soil S leaching (Figure ll)(Witter, EH03-7) were observed
across five sites in the sugar maple forests distributed along a second SO42" deposition gradient
from northeastern Minnesota to Michigan. The sites used by Witter and Pregitzer et al. were
selected so that deposition of SO42" increased by about 5 kg/ha/yr between successive sites from
Minnesota to the southeastern region. After this criterion was met, 15 plots were selected (three
per site) controlling for three variables: 1) landform (glaciated, mesic uplands with slopes of
0-20%; south slopes were avoided except in two plots); 2) soil texture (sand-loam A horizons,
distinct E horizon, and sand B horizon); and 3) vegetation (sugar maple overstory with mean age
of55-75 yrs, no obvious disturbance). The effort invested in locating analogous stands strengthens
the argument that long-term deposition patterns of S and N may be involved in influencing
nutrient cycling in these forests. A number of other patterns in nutrient chemistry are noted in
in the entry for Witter et al, in Table 5; however, SO42" deposition does not appear to be affecting
these patterns. Research is still continuing, but no change in forest growth or mortality has been
observed along the gradient (Witter et al., EH03-2, Table 7).
A decrease in soil pH, a decrease in exchangeable soil calcium (Ca), and an increase in soil C
(Figure 12) were observed in the Al horizon of soils along a gradient of increasing SO42"
deposition across seven sites from Arkansas to Ohio (Table 5, Loucks and Somers, EH05-6). In
addition, exchangeable aluminum (Al) was higher at sites with a high ratio of equivalents of SO42"
deposition to equivalents of total soil basic cations. Precipitation decreases along the Ohio
corridor gradient from west to east (130 versus 100 cm annual average; O. Loucks, personal
communication). Thus, these results contradict the view that soil C increases with precipitation
(Brftriy, 1974; Oades, 5.938), and Loucks and Somers concluded that acidic deposition may have
reduced rates of surface layer decomposition processes. Plots in the Ohio gradient were selected
22
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FRP FOREST EFFECTS REPORT
MATRON ETAL
• Pennsylvania gradient: red maple sites *>'
¦ Ohio gradient: oak-hickory sites
A -.Michigan gradient: sugar maple sites
£7^ Minnesota gradient
Figure 9. Forested regions studied by the FRP in the eastern hardwoods. (Refer to Figure 3
for SO42" deposition patterns.)
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FRP FOREST EFFECTS REPORT
MATTSON EI'AL
2,000
I 1,900
.E a.
1,800
1,700
1,600
1,500
Nitrogen
• Sulfur
N.E. Minnesota
S.W. Michigan
Figure 10. Foliar S concentrations in sugar maples and S and N flux in litterfall (all species) at
sites along the Michigan gradient (from Pregitzer et al., EH03-4). (Refer to Figure
9 for site locations.)
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MPO#4
FRP FOREST EFFECTS REPORT
MATRON ETAL
250 -
200 -
~ O)
o
W w 150
100 -
A' B horizon
# A + E horizon
mean ts.e.
4
*
I
r 3,ooo
- 2,000
- 1,000
L 0
c
o
_N
*u
o
JC
° §>
c#
CO
"co
£¦
t
1
-1
-2 -
-4 -
N.E. Minnesota
S.W. Michigan
Figure 11. Soil S pools and net SO42" loss below the B horizon from Michigan gradient sites.
Soil nutrient flux was calculated using an estimate of evapotranspiration of 42% for
all sites (from Witter et al., EH03-7). (Refer to Figure 9 forsite locations.).
25
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FRP FOREST EFFECTS REPORT
MATPSON ET AL
Soil Chemistry Along Ohio Gradient
0.07
0.06
0.05
0.04
0.03
0.02
0.01
0
10
mean ± s.e.
n=8 plots/site
_j i i i
i i
1 2 3 4 5 6 7 7
Site (acid) (calc)
Arkansas ~Ohio
Figure 12. Total S and total C in the Al horizon of siliceous, sandstone-based soils in sites
along the Ohio gradient. (Refer to Figure 9 for site locations.) Site 7 is displayed
on acid soils (4 plots) and on calcareous soils (4 plots); the plots on calcareous soils
are not comparable to the remaining sites (from Loucks and Somers, EH05-6).
26
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FRP FOREST EFFECTS REPORT
MATTSON ETAL
to be as analogous as possible; eight plots per site were selected on unglaciated and poorly
buffered soils, on mostly southerly and upper slope positions, supporting oak and hickories
typically from 75-130 years of age. It was recognized that deposition at a site would vary as a
function of both rainfall differences due to local topography and distance from local sources of
SO2 emissions (coal-burning power plants). The three sites near the Ohio River were in closer
proximity to local sources of SO2 compared with three sites to the north (Figure 9). Effects of
these local sources of SO2 have not yet been analyzed, but the regional trend in soil S is in the
same direction as that reported by David et aL (VS10-7) and Witter et aL (EH03-2).
Loucks and Somers [EH05-6] attempted to examine whether their observed trend of decreasing
pH and increasing soil C with increasing SO42" deposition along the Ohio gradient is a recent
phenomenon. They compared their data to county soil survey data of similar soils collected
during the 1960s and 1970s. The county soil survey data indicated no trend in either pH
(mid-range among the sites varies from pH 4.9 to 5.4) or percent C (mid-ranges vary from pH 1.4
to 3.2). The pH values of Loucks and Somers tend to be lower than values from the 1960s and
1970s at all sites (medians vary from pH 3.9 to 4.6), whereas the C values are higher at the eastern
sites (means vary from 4.5 to 7.8%). Comparisons of pH values or percent C between the two
data sets should be made with caution since Loucks and Somers did not determine what portion
of the differences could be due to differences in methods.
Preliminary analyses of forest condition along the Ohio gradient indicate that subtle changes may
be occurring. Mortality rates of larger trees have increased in the last decade; however, the rates
still appear to be quite low and no spatial patterns exist (Loucks et al., EH05-8)(Table 7). On
sites with low Ca Al ratios, radial growth of black oak and white oak has declined since 1960
(LeBlanc, EH05-7)(Table 7).
Along a deposition gradient in Pennsylvania, soil exchangeable magnesium (Mg) and Ca were
correlated with atmospheric deposition of Mg and Ca. Sap concentrations of Mg and Ca in red
maple stems were also correlated with deposition patterns (McCormick, EH04-3). Similarly,
there was a strong association between sap N concentrations and levels of atmospheric N
deposition. This suggests that nutrient cycles in the soil and in the trees are responding to
atmospheric deposition.
In summary, several trends have been reported in nutrient cycling or soil chemical properties
alongregionalgradients of SO42' deposition. The same variables were not measured in all studies,
makirigit difficult to reach a common conclusion. However, three studies measured some aspect
of soil S, and all observed an increase with increasing SO42' deposition. Increased S suggests that
deposition can have measurable effects on nutrient cycling. While these types of studies cannot
establish cause, these findings do establish a relationship between atmospheric deposition and
soil chemical properties.
If SO42" deposition is causing increases in soil S availability and cycling within the forests, a
number of possible responses may be expected. Along with S, increased N and hydrogen (H)
deposition also occurs (Reams etal., 1990). Soil nutrient availability may be increased due to the
inputs of S and N and due to increased weathering of basic cations. As deposition of anions
increases to levels exceeding plant uptake, leaching below the root zone will occur because soils
have low anion retention capacities (Bohn et al., 1979). Anion leaching will act to remove basic
cations, causing some reductions in soil pH. But S deposition alone will not acidify soils to values
below pH 42 because SO42' can be fixed in soils as aluminum hydroxosulfate (Schulze, 1989).
Alternatively, mineral weathering may exceed the rate of anion leaching and no detectable change
in exchangeable cations may occur for decades. Concomitant changes in forest condition
(mortality or decreased growth) and changes in nutrient cycling should probably not be expected
during the early phase of increased deposition. An early effect of increased S, N, and H
deposition could be a fertilizer response due to greater availability of S, N, and basic cations in
27
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the soil. Some fertilizer response is suggested in the tree tissue chemistry data of both the
Michigan gradient and the Pennsylvania gradient.
3.12 Trends Along Elevational Gradients of Cloud Deposition
In the spruce-fir forests in the Appalachian Mountains, patterns of soil chemistry may be
examined to test the hypothesis that levels of soiJ exchangeable nutrients are related to patterns
of atmospheric deposition. Although not directly measured on all mountains, atmospheric
deposition of acidic compounds is reasoned to increase with elevation because the frequency of
cloud events increases with elevation, and cloud water chemistry is more concentrated than other
forms of precipitation (see Section 2.7).
Exchangeable nutrients are positively charged ions (cations) that are "held" electrostatically by
the soil. Exchangeable cations are measured in the laboratory by replacement with another
positively charged ion (typically NH4+ ). With the exception of nutrients dissolved in soil solution,
exchangeable nutrients are the most easily "removed" from soil and are thought to represent what
is readily available for root uptake. Elements (such as phosphorus (P) or Al and sometimes
cations) may be referred to as extractable since stronger chemical analyses (e.g., dissolutions) are
used to remove these elements from the soil in the laboratory.
In sampling soils along transects with increasing elevation in the noithern Appalachians,
decreases in exchangeable Ca (Ryan and Huntington, SF05-8; Huntington and Ryan, SF05-6;
Johnson et al., SF08-4; see also McLaughlin et al., SF10-3 in Table 9) and exchangeable Mg
(Johnson et al., SF08-4) have been observed. Exchangeable cations in the forest floor and the
soil at two elevations on Mt. Moosilauke, NH, are shown in Figure 13. Increases in extractable
P (Ryan and Huntington, SF05-8), extractable Al (Johnson et al., SF08-4), and exchangeable
potassium (K) (Johnson et al., SFOS-4) have also been observed. Exchangeable K concentrations
did not always increase with elevation (Ryan and Huntington, SF05-8).
In contrast, no changes in extractable Al or in base saturation were observed with increasing
elevation in the southern Appalachians (Wells et al., SF21-4). Wells et al. did observe decreases
in exchangeable Mg and increases in exchangeable K, increases in extractable Pb, and increases
in extractable SO42* with increases in elevation.
Joslin et al. (SF27-1) observed higher concentrations of soil solution NO3' and soil solution Al at
a site receiving higher cloud water inputs compared with a site with lower cloud water input at
Whitetop Mountain, VA. These extremely high NO3" concentrations and similar patterns of high
and low concentrations over a season between soil solution Al and NO3" at Whitetop are shown
in Figure 14. Decreases in base saturation and increases in soil solution Al are the type of changes
one would expect due to increasing soil solution acidity (Bohn et al., 1979). Increases in
nitrification may be expected with increased deposition of NH4-N. Strader et al. (SF17-1)
reported high N contents in throughfall (18-32 kg/ha/yr with two-thirds as NH4-N) and high soil
N mineralization (26-180 kg/hayyr) at elevations from 1579 to 2006 m in the southern Ap-
palachians. Nitrate was the dominant anion in soil solution collected from a high (2006 m) and
a low (1750 m) site in the Black Mountains of North Carolina (Smithson et al., SF12-7). Changes
in solution Al, Ca, and Mg were highly correlated with changes in NO3" concentrations.
Wells et al. (SF21-4) found that extractable Pb was higher on west-facing slopes than on
east-facing slopes in the southern Appalachian Mountains, but other soil properties did not vary
according to exposure. No differences in soil chemical properties between east and west aspects
were reported by Ryan and Huntington (SF05-8) for Mt. Moosilauke, NH. Lack of an influence
of exposure on soil chemical properties suggests that deposition loadings do not vary with
exposure in the high-elevation spruce-fir forests, even though it is assumed (but has not been
demonstrated due to lack of data) that west-facing slopes of these mountains receive higher
deposition loadings, especially in the northeastern Uaited States.
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FRP FOREST EFFECTS REPORT
MATTSON ETAL.
Soil
Forest Floor
CO
£
O TD
¦*-> U)
03
o
0
CD CD
05
03 ^
0 Q
CD =
C
03
+
O
X
LU
O
E
o
Ca
30
I
a
i
0-10
1
\
10-20
Q
I
1
20+ I
1
Mg
Al
15
20
10
Oie
Oa
840 1000
840 1000
Elevation (m)
Figure 13. Exchangeable Ca, Mg and Al (extracted in IN NH4CI) in the Oie and Oa horizons
of the forest floor and at three depths in the mineral soil. Spodosols at two eleva-
tions on east and west aspects of Mt. Moosilauke, NH, were sampled. Note varying
scales of Y-axis (from Huntington and Ryan, SP05-6, and Ryan and Huntington,
SF05-8).
29
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FRP FOREST LFFliCIS RKI'ORT
MATTSONETAL
CD
E
0)
03
300
250
200
150
100
50
o Nitrate
~ ~
~~
On °0 °0
250
200
150 ^
O
E
100 £
Z3
C
E
50 3
A S O
1987
AM J J A S
1988
Figure 14. Seasonality in soil solution concentrations of Al and NO3' collected in tension
lysimeters in A horizons at a site receiving high amounts of cloud deposition on
Whitetop Mountain, VA. (from Joslin et al., SF27-1).
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FRP FOREST EFFECTS REPORT
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Failure to detect differences in soil chemical properties as a function of exposure or other
topographic features may be due to the inherent variability of soils in forested ecosystems. Using
a sampling area of only 12 x 14 m, Robarge and Smithson (SF12-2) have demonstrated that the
within-plot variability for most soil chemical properties is greater than 30% when expressed as a
coefficient of variation. Such inherent variability in soil chemical properties for forested soils
limits the ability to detect statistically significant differences unless the experimental design
includes a large number of plots and/or intensive sampling within plots (Robarge and Smithson,
SF12-2). This variability may be further complicated by changes in soil type as a function of
elevation or landscape position. Different soils may not respond to atmospheric deposition to
the same extent. For example, Ryan and Huntington (SF05-8) concluded that Cryofolists, found
at higher elevations on ML Moosilauke, NH, were more sensitive to further cation depletion than
were the Spodosols at lower elevations.
In summary, these correlative trends of decreases in base cations and increases in Al with
elevation demonstrate a fairly consistent relationship between soil chemical properties and
atmospheric deposition of acidic compounds from clouds. However, the trends do not
demonstrate that changes in soil chemistry were caused by atmospheric deposition. We do not
have the historical data on soil chemical properties necessary for causal inference. In addition,
other possible explanations for the observed trends exist, such as elevation differences in parent
material, climate, mineral weathering patterns, vegetation, and land use history. In the southern
Appalachians, site (i.e., mountain) had a greater effect on variation in soil chemical properties
than did elevation (Wells et al., SF21-4; W. Robarge, personal communication).
3.1 J Experimental Additions of Acidic Solutions to Soils
Soil chemical properties (e.g., complexation, ion exchange, dissolution and precipitation, and
microbial processes) react relatively rapidly in response to changes in soil solution. Deposition
of acidic compounds via rainfall and throughfall may cause short-term changes in soil solution
composition as well as long-term changes in bulk soil chemical properties. Four FRP studies
examined changes in soil chemistry as a function of artificial additions of acidic solutions to soils.
Three studies are summarized in Table 5 and one seedling study from Table 4 is also discussed
here. In addition, the ROPIS East project and the Watershed Manipulation Project (discussed
later in this section) are examining changes in soil chemistry as a function of simulated acidic
additions.
In controlled laboratory experiments, Smithson and Robarge (SF12-6) compared the effects on
soil solution composition of simulated throughfall solutions (equal in composition to throughfall
from a spruce-fir canopy at 2006 m elevation in the southern Appalachians) with distilled water
(Figure 15). Increasing the acidity or ionic strength of the simulated throughfall resulted in
increased Al concentration in soil solution, but the Al concentrations in extracts from Oa, A, or
B horizons did not exceed 100 ^M. Failure to obtain high concentrations of Al (i.e., 200 ^M)
with simulated throughfall agrees with the field measurements of soil solution composition
obtained by Smithson et al. (SF12-7) using tension lysimeters. Concentrations of Al exceeding
200//M were observed by Smithson et aL (SF12-7) in only approximately 1% of the 983 samples
collected throughout the growing season in the Black Mountains, NC, and Whitetop Mountain,
VA. The controlled experiments of Smithson and Robarge (SF12-6), however, were confounded
by the production of relatively large amounts of NO3', even when soil samples were stored at 4°C.
Huntington et al. (SF30-1) hydrologjcally isolated blocks of soil and added sulfuric acids of pH
35,4.5, and 5.1 at Whiteface Mountain, NY. The isolation procedure cut live roots and caused
increased production of NO3' in the soil solutions. In addition, concentrations of Al sampled in
tension lysimeters were highly correlated with concentrations of NO3'. Concentrations above
those thought to be toxic to red spruce roots (200 ^M) were induced, but only with abnormally
31
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MATTSON ETAL
200
150
100 -
50
0
60
50
40
30
20
10
Al
~
Ca Mg
Oa horizon
mm
w
A horizon
HgO
Acid
2X Acid
Salt
T reatment
Figure 15. Solution Al, Ca, and Mg concentrations in pressure extracts of spruce-fir forests
soils treated with water, acid, or salt solutions. Shown are Oa and A horizon
samples collected at Smithson and Robarge's 1760-m site near Mt. Mitchell, NC.
Asterisks above each element in the H2O treatment indicate statistical significance
(p <, 0.01)(from Smithson and Robarge, SF12-6).
32
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FRP FOREST EFFECTS REPORT
MATTSON ET AL-
high NO3" in the soil solution that had itself been induced during the first year by the isolation
procedure. Based on realistic NO3' concentrations, the authors concluded that roots were
exposed to A1 concentrations of200/jM only in the forest floor and less than 1% of the time under
ambient conditions. These conclusions agree with the observations of Smithson et al (SF12-7)
in the southern Appalachian Mountains. Research is continuing, and results from a second year
should provide more definitive information as the disturbance effect is expected to subside.
Meier et aL (SP02-l)(Table 4) observed greater than 50% decreases in base saturation, exchan-
geable Ca, and exchangeable zinc (Zn) following simulated rains of pH 25 when compared with
simulated rains of pH 55. They also observed decreases of up to 0.6 pH units in soil pH and
greater than 20% increases in exchangeable acidity during the treatments. Changes in Mg, K,
and P were not statistically significant The treated soil was classified as a loamy-skeletal, mixed
frigid, Typic Haplumbrept. It was collected at 1885 m from a red spruce stand on Mt. Mitchell,
NC, that, according to Meier et al., showed "visual evidence of decline." The soil was exposed to
simulated rains three times per week, either with or without red spruce seedlings planted in them.
Compared with pH 5.5, statistically significant effects (decrease in base saturation, decrease in
exchangeable Ca, decrease in exchangeable Zn, decrease in soil pH, and increase in exchangeable
acidity) were observed after 25 applications at pH 25 (p < 0.05). After 50 applications, some
effects at pH 3.5 were significantly different from those at pH 5.5 (for soils without seedlings:
increased exchangeable acidity and decreased base saturation; for soils with and soils without
seedlings: decreased soil pH).
Ludovici et al. (SC05-8) observed about 10% decreases in base saturation, Ca concentration, and
Mg concentration in soils following applications of simulated acid rains of pH 33 compared with
simulated acid rains of pH 43. In addition, soil pH decreased from 4.57 to 4.49 and cation
exchange capacity (CEC) increased from 3.00 to 339 cmol/lcg. Ludovici et al. placed the top
10 cm of Helena sandy clay loams (clayey, mixed, thermic aquic Hapludult) into pots and planted
them with loblolly pine seedlings. The soils and seedlings received fertilizer before treatments
of simulated acid rain began. Rains of pH 33 and 43 (with varying S:N ratios) were applied three
times per week for 20 weeks. Soil pH, base saturation, and Ca and Mg concentrations showed
slightly greater reductions in soils receiving acid applications composed of sulfate compared with
acids composed of nitrate. After 20 weeks, Ludovici et aL observed a 13% increase in fine root
growth at pH 33 compared with pH 43.
Although not an experimental addition of acid, an experimentally induced change in cation
availability in soils was examined by Binkley et al. (SC16-1) and is reviewed here. Binkley et aL
observed decreases in soil pH of 03 to 0.8 units after 20 years following a conversion of a cotton
field to a pine plantation. They also observed decreases in extractabie cations and increases in
Al. These changes were attributed to increased cation uptake and storage by the vegetation as
hypothesized by Ulrich (1983) and Reuss and Johnson (1986).
In summary, these studies demonstrate changes in soil chemical properties due to additions of
acids or change in some other component of the nutrient cycle. These results indicate that some
soils may be less buffered against changes than is generally expected. However, the observed
changes can be interpreted in different ways. It is uncertain what effects, if any, the increases in
Al mobility or decreases in base cations would have on tree growth. Both Smithson and Robarge
(SF12-6) and Huntington et al. (SF30-1) observed that most of their elevated Al concentrations
were still below200/
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FRP FOREST EFFECTS REPORT
MATTSONETAL
is also warranted since two studies mentioned that potential confounding of Al concentrations
by high NO3" was caused by the experimental manipulations of the soils.
The observation of high NO3" in soil solutions of soil that was manipulated or disturbed during
the collection procedure merits further discussion. These soils were from high-elevation spruce-
fir forests. As discussed earlier, Joslin et al. (SF27-1) observed high solution NO3* in soils at
Whitetop Mountain, VA. High rates of N inputs in thrcughfall and high rates of mineralization
were observed at high-elevation sites on Mt. LeConte in the Great Smoky Mountains National
Park and on Whiteface Mountain, NY, by Strader et al. (SF17-1) and on Mt. Mitchell, NC,
Clingmans Dome in the Great Smoky Mountains National Park, and Whitetop Mountain, VA,
by Sasser and Binkley (SF17-2). Increased Al in soil solutions is associated with high NO3'
concentrations (Joslin et al., SF27-1) and with N03* formation (Smithson and Robarge, SF12-6).
The N cycle in these high-elevation forests may be enriched by high rates of atmospheric inputs
of N and by a high potential for soil nitrification which in turn, appears to be linked to increased
Al mobilization.
3.1.4 Literature Reviews and Modeling Projections
Literature reviews and modeling projections have indicated that atmospheric deposition can
change soil chemical properties (Table 11). Binkley et al. (1989), in an analysis that included a
literature review and computer simulations, concluded that half of southern forest ecosystems do
not retain S inputs in the soil. Therefore, these ecosystems may be prone to SO42" leaching of soil
cations. Richter (SC99-19), in a review of soil solution chemistry and acidic deposition in
southeastern forests, also speculated that acidic deposition may increase the distribution of
polyvalent cations such as Al in soil solutions and result in greater leaching of nutrient cations.
Additionally, atmospheric deposition is thought to be replenishing soil N lost due to past land
use practices.
3.1.5 Tree Condition as a Function of Soil Chemistry
Four FRP studies examined red spruce crown condition as a function of soil chemical status
(Table 5). Crown vigor was assessed as percent of recent needle loss from live crowns.
On Mt. Moosilauke, NH, Huntington et al. (SF05-7) observed lower concentrations of soil P and
forest floor Mg and Ca at sites where red spruce showed declining crown condition. They also
reported a positive correlation between soil and foliar Ca. Overall, the authors concluded that
foliar nutrient concentrations were not related to crown condition and, in general, that red spruce
do not appear to be deficient in foliar nutrients with the possible exception of P. They suggested
that availability of nutrients, particularly Mg and P, may play a role in spruce vigor on Mt.
Moosilauke, but there is no demonstration that nutrient stress causes reduced vigor.
On Whiteface Mountain, NY, Johnson et al. (SF08-3) detected no relationships between soil pH,
soil cations, or soil Al and crown damage in red spruce. In another study, Johnson et al. (SF08-14)
observed no correlation between soil and foliar levels of K, Ca, or Al, and no relationship between
foliar Ca or Mg and crown condition, although decreases in foliar K were associated with
declining crown condition. Johnson et al. (SF08-3) concluded that soil cations were generally not
limiting, but that a potential for limitations of P and Mg exists.
Joslin et al. (SF27-1) observed decreased foliar growth of red spruce at a site on Whitetop
Mountain, VA, that received higher cloud deposition of water, SO42', NO3', and NH4 + compared
with a site that received lower deposition of the same components. They also observed soil Al
levels near levels reported to be toxic to roots and decreased foliar Mg, Zn, and Ca concentrations
at the high-deposition site.
In summary, soil uutriunt status does not appear to be related to loss of foliage in red spruce,
particularly on Whiteface Mountain. Although red spruce crowns are reported to be in worse
34
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MAT1SONETAL
condition on Whiteface Mountain than on Mt. Moosilauke (Friedland, SP05-9; T. Huntington,
personal communication), the soils at Whiteface Mountain have higher base saturations and
higher concentrations of soil exchangeable Ca than the soils at Mt. Moosilauke (see Johnson et
aL, SF08-14, and Huntington and Ryan, SP05-6). These two observations (Lc., worse crowns but
better soil nutrient status at Whiteface compared with Moosilauke) suggest that cation deficiency
is not a primary cause of change in crown condition. However, on Whitetop Mountain, there is
a correlative relationship between soil nutrient status and foliar condition: high soil Al levels,
reduced foliar Mg, Ca, and Zn concentrations, and decreased foliar growth occur at a high-
deposition site compared with a low-deposition site (Joslin et aL, SF27-1). Cation deficiency
should not be judged on the basis of these correlative studies alone.
3.1.6 Soil Studies of Other Programs
In this section, we compare soil studies of several concurrent programs with the FRP results
discussed above. Special emphasis is placed on nutrient cycling since results discussed thus far
demonstrate that atmospheric deposition of SO42" and possibly NO3' alter nutrient cycling
patterns. The FRP results by themselves are too incomplete to allow definitive conclusions. The
results discussed here support many of the FRP results. Since these programs were not reviewed
in the methods section, a brief description of each program is provided.
IFS Results
The Integrated Forest Study (IFS) has performed a substantial amount of research on atmos-
pheric deposition and nutrient cycling. The IFS was funded primarily by the Electric Power
Research Institute (EPRI) and also in part by the FRP, the Canadian Forest Service, and the
Norwegian Forest Research Institute. Research was conducted at 17 forest sites in the United
States, Canada, and Norway. These sites, which represent a range of climates, air qualities, soils,
and vegetation, facilitate testing of hypotheses about the effects of atmospheric S and N deposi-
tion on forest nutrient cycling. Data were collected at 13 intensive measurement sites to estimate
nutrient standing stocks in the vegetation, forest floor, and soil and to estimate fluxes between
the atmosphere, canopy, and two soil depths. The following information is from the IFS Annual
Report (Lindberg and Johnson, 1989).
Total atmospheric deposition of S042'-S across the 17 sites ranged from 10 to 42 kg/ha/yr, while
N deposition ranged from 5 to 25 kg/ha/yr. The lowest deposition of both elements occurred in
the northwestern United States and the highest occurred in the Great Smoky Mountains, the
Piedmont, and at Whiteface Mountain, NY. Levels of S flux from a site generally corresponded
to S input levels. Sites with low S inputs tended to retain S inputs. A surprising result was that a
number of sites, especially those with high S input levels, exhibited net S losses (Figure 16).
However, the amount of S loss relative to the amount of S input was relatively small. These net
S losses could be due to underestimates of S inputs, overestimates of S losses, SO42" desorption,
and/or net S mineralization.
Annual gains or losses of N varied considerably across sites (measured as inputs versus outputs,
as shown in Figure 17). High N losses were observed at some of the Great Smoky Mountain sites
and the Turkey Lakes in Ontario, and, as expected, in the N-fudng red alder site in Washington.
Overall, most sites appeared to be in steady state with regard to S leaching that is, outputs were
relatively similar to inputs. However, N appeared to be accumulating in most sites, and three
sites appeared to be N-saturated (i.e., leaching NO3' in excess of inputs of total N). Saturation
of N did not appear to be induced by deposition. The potential effects of N saturation include
increases in soil acidity, soil solution ionic strength, soil solution Al activity, and decreases in soil
base saturation (Cole and van Miegroet, 1989).
35
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l-RI' I'OKLSTEKPliClS REPORT
MATISON in' Al_
>
~co
sz
CT
(1)
-g
C\J
cf
(f)
Z)
a
"3
O
Input of S04 " (keq/ha/yr)
CP, Coweeta Hyd. Lab, NC
DF, Thompson Forest, WA
DL, Duke Forest, NC
GL, BF Grant Forest, GA
HF, Huntington Forest, NY
LP, Oak Ridge, TN
NS, Nordmoen, Norway
FiA, Thompson Forest, WA
TL, Turkey Lakes, Ontario
WF, Whitetace Mtn., NY
Figure 16. Sulfate outputs from B horizon as a function of SO42" inputs in total (wet plus dry)
deposition at IFS sites. Soil water flux was obtained from nearby gauged streams,
modeling, CI" balance, or from evapotranspiration estimates. Diagonal line indi-
cates equal inputs and outputs (from Mitchell, 1989).
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FRP FOREST EFFECTS REPORT
MATRON ETAL
Inputs of total N (kmol/ha/yr)
CP, Coweeta Hyd. Lab., NC
DF, Thompson Forest, WA
DL, Duke Forest, NC
FL, Findley Lake, WA
HF, Huntington Forest, NY
NS, Nordmoen, Norway
RA, Thompson Forest, WA
SB, Smoky Mtns., NC
SS, Smoky Mtns., NC
ST, Smoky Mtns., NC
TL, Turkey Lakes, Ontario
WF, Whiteface Mtn., NY
Figure 17. Total N outputs from B horizon as a function of total N deposition (wet plus dry) at
DFS sites. Soil water flux was obtained as described for Figure 16. Diagnoal line in-
dicates equal inputs and outputs (from Cole and Van Miegroet, 1989).
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A principal objective of the IFS study was to determine the extent to which acidic deposition may
be inducing cation losses and soil acidification. As in FRP results, high-elevation sites had lower
soil base saturation (less than 10% in the B horizon). High-elevation/northern soils were more
acidic than those of low-elevation/southern sites (base saturation ranged from 8% to 85% in the
B horizon). Glaciated soils tended to have higher total cation contents due to greater weatherable
minerals.
More than 75% of the IFS plots showed base cation losses (inputs minus outputs; range = + 500
to -2800 eq/ha/yr). No particular regional patterns of cation loss were evident. Since pollutants
are assumed to be regional in effect, pollutants may not be a primary factor in the cation loss.
Greatest cation losses occurred in the red alder site and the Turkey Lakes site, both of which
have high NO3' production in the soil. Calcium budgets (inputs minus outputs) were positive for
about half the sites and negative for the remaining sites. The same was true for K, while Mg
budgets were negative in 17 of 19 sites. Fourteen of 19 sites lost at least 1.5 kg/ha/yr of Mg. In 7
of 19 sites, this represented more than 5% of the soil exchangeable pool (Figure 18). Thus, there
appears to be a potential for Mg deficiency in the near term (without substantial weathering
resupply). Also, Al was released in greater amounts in high-elevation or high-acidity sites.
ALBIOS Results
The Aluminum in the Biosphere (ALBIOS) project was initiated with EPRI funding to examine
patterns of Al biogeochemistry and effects of Al on physiological processes of trees in eastern
North America and northern Europe. The project focused on two hypotheses: 1) acidic deposi-
tion increases the concentrations and transport of soluble Al in soils and surface waters of forested
watersheds; and 2) in sensitive ecosystems, acidic deposition may increase available Al to levels
that are toxic to trees and aquatic biota, causing growth reductions, nutritional deficiencies, or
mortality. The following is from a summary of ALBIOS by Cronan et al. (1989).
Field studies of Al biogeochemistry included 10 North American and four European watershed
catchments that provided a broad range of contrasting forest types. Controlled studies included
hydroponic systems, greenhouse soil culture experiments, and root ingrowth core experiments to
evaluate potential toxicity of Al to an "indicator" tree species, honey locust, and to several
commercial tree species: red spruce, sugar maple, red oak, American beech, European beech,
and loblolly pine.
In the controlled studies, tree species exhibited a range of concentrations at which negative
responses to Al occurred. Root and shoot growth of red spruce, European beech, and sugar
maple were reduced by soluble Al concentrations of 200 to 800 //M; red spruce root growth was
uniformly reduced at soil solution Al concentrations between 200 and 300 /*M. In contrast, red
oak, American beech, and loblolly pine tolerated up to 3000 (iM of soluble Al. Elemental
concentration of Al in plant tissues typically increased before growth reduction occurred.
Additionally, these experiments indicated that apparent sensitivities of trees to Al in the rooting
medium may be strongly influenced by ionic strengths of the culture solution or soil solution.
The comparative field results showed significant interregional differences in the concentrations
of aqueous Al and strong acid anions in soil solutions at the North American and northern
European study catchments. In general, the highest concentrations of soluble Al were found in
the mineral soil horizons of the northern Spodosols and high-elevation southern Inceptisols in
the United States, and the Inceptisols in Germany. These soils shared the following charac-
teristics: base saturation usually less than 15%; pH in water less than 4.9; and soil solution SO42"
greater than 80/iM.
Cronan et al. (1989) speculated that the potential for Al toxicity probably varies across landscapes
and may be most likely under the following conditions: in forests with trees shown to be sensitive
from seedling studies (e.g., red spruce); forest ecosystems in which fine roots are concentrated
38
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MAT1SON ETAL.
¦c
o
Q.
E
0.2
0.15
0.1
0.05
O
o.
di
(0.05)
(0-1),
I
J
Ca g] Mg |K
n A
I
< i
_L
J_ I 1 I I L
J I
J L
HF SS2 SS1 SB1 SB2 DF NS2 CH RA LP2
TL ST1 ST2 WF FL NS1 CP DL LP1
IFS site
HF, Huntington Forest, NY
TL, Turkey Lakes, Ontario
SS, Smoky Mtns., NC
ST, Smoky Mtns., NC
SB, Smoky Mtns., NC
WF, Whiteface Mtn., NY
FL, Findley Lake, WA
CF, Thompson Forest, WA
NS, Nordmoen, Norway
CP, Coweeta Hyd. Lab., NC
QH, Coweeta Hyd. Lab., NC
DL, Duke Forest, NC
RA, Thompson Forest, WA
LP, Oak Ridge, TN
Figure 18. Fraction of soil exchangeable Ca, Mg, and K lost annually by leaching ([leaching -
deposition]/exchangeable) at the IFS sites (from Johnson, 1989).
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in mineral soil horizons with less than 10% to 15% base saturation; in northern and high-elevation
southern ecosystems in the United States with large amounts of acidic deposition; in forests with
marginal soil supplies of Ca, Mg or P; and in forests subject to drought stress and dependence
on deep rooting for water supplies. Conditions for Al toxicity to some tree species appear to exist
at some ALBIOS study watersheds. However, this conclusion is uncertain for several reasons:
studies of AJ toxicity were based primarily on seedlings; rooting media were artificial; chemical
environments in roots have been in limited and manipulated rtinges; experimental trees have
generally not had mycorrhizae; and field soil solution chemistry may not reflect the soil solution
chemistry in rhizospheres due to difficulties in sampling techniques.
DDRP Results
The Direct/Delayed Research Project (DDRP) is an EPA research program funded under
NAPAP to predict the effects of acidic deposition on surface water chemistry (Church et al.,
1989). The DDRP projects potential surface water chemistry changes as a function of varying S
deposition scenarios in the northeastern United States and the Appalachian Mountains using the
following: regional deposition chemistry and surface water chemistry data bases, a statistically
rigorous watershed selection and extrapolation scheme, regionally extensive watershed mapping,
soil sampling and analysis, and model simulation of watershed behavior. Because deposition
chemistry is altered by soils as soil waters drain to surface waters, and because S retention by soil
and leaching of base cations from soils influence whether surface waters in a watershed may
acidify, much of the DDRP effort was directed towards evaluating regional soil conditions and
projecting chemical responses.
A number of the DDRP findings pertain to soil chemistry and S deposition. Net watershed
retention of atmospherically deposited S varied regionally. Approximately 75% of total S
deposition was retained within the soils of the watersheds in the Southern Blue Ridge Province.
From there, S retention generally decreased as one goes northeasterly, soil S pools in watersheds
of the northeastern United States were approximately at steady state. Therefore, continued
inputs via deposition are balanced by leaching. Leaching of SO42", the mobile S anion, carries
base cations from the watershed to the surface waters. The importance of cation losses to forest
condition depends on whether or not cation resupply through mineral weathering can match the
losses.
Results of projections indicated that continued deposition at current rates could continue to
mobilize Al and other elements in soils. This Al could be toxic to root systems. The importance
of processes represented in the models used by the DDRP is being tested in field acidification
experiments as part of the Watershed Manipulation Project (WMP). Whole watersheds are
being treated with ammonium sulfate applications, and a series of soil chemical processes are
being monitored.
ROPIS Results
The Response of Plants to Interactive Stresses (ROPIS) program has been sponsored by EPRI
to examine the interactive effects of environment and air pollutants on tree growth, to determine
the underlying physiological mechanisms of tree response, and to develop and test physiological
and growth models to predict long-term responses of trees to the environment and air pollution.
Specific regional hypotheses are being tested at three United States sites.
In ROPIS East, red spruce and sugar maple are under study at Boyce Thompson Institute at
Cornell University, NY (Laurence et al., 1989). The red spruce research has two components:
controlled exposures of seedling and sapling trees in open-top chambers and assessment of
mature trees in the field. Red spruce saplings from a red spruce stand in Maine were dug out
with their attached roots aud soils and placed in large pots in open-top exposure chambers at the
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Boyce Thompson site. The forest floor and soil A and B horizons were reconstructed in the pots
and lysimeters were installed to sample soil solutions. Controlled exposure treatments consist of
four levels of O3 (charcoal-filtered, 1,1.5, and 2 times ambient) alone and in combination with
three levels of acidic precipitation (pH 5.1,4.1, and 3.1). Seedlings and saplings have been studied
for two years, and mature trees is the Maine stand have been studied for one year. Sugar maple
exposures were planned for 1990, but results are not available yet
After two years of exposure in the ROPIS East study (Laurence et al., 1989; Sherman and Fahey,
1989), the forest soil supporting red spruce saplings had significantly lower pH, significantly lower
exchangeable Ca and Mg, significantly greater exchangeable Al, and higher rates of leaching of
NO3" and cations as acidity of the simulated run increased from pH S.l to 3.1. Most differences
between the pH 5.1 and 4.1 treatments were statistically significant In addition, pH treatments
had significant effects on soil solution concentrations; greater soil solution concentrations of
NO3', SO42*, Ca, Mg, manganese (Mn), and Al were observed with higher acidity treatments. Al
toxicity was not expected due to relatively low Al:Ca ratios in the soil. In general, O3 treatments
did not affect concentrations of soil solutions.
In ROPIS South, loblolly pine are under study at Oak Ridge National Laboratory, TN, in
cooperation with the Tennessee Valley Authority (TVA) (Kelly et al., 1989). This project has
two components: a three-year (1986-1988) O3 screening study and a three-year (1987-1989)
factorial study of acidic precipitation, O3, and soil Mg. During the screening study, five half-sib-
ling families (one parent in common) were exposed to three levels of O3 (from charcoal-filtered
to ambient-plus-60 ppb). After one year of exposure, a family with an intermediate response was
selected for the factorial study. Controlled exposure treatments consisted of three levels of O3
(charcoal-filtered, ambient, and 2-times-ambient), two levels of acidic precipitation (pH 5.2 and
3.8), and two levels of Mg availability. In this study, Mg-deficient soil had no significant effect
upon the seedling growth of loblolly pine after two years of applications of 03, acidic precipitation,
and soil Mg.
In ROPIS West, ponderosa pine are being studied at Whitaker's Forest, CA, near Sequoia
National Park, in cooperation with University of California and the USFS (Temple, 1989).
Controlled exposures of two-year-old ponderosa pine seedlings in open-top chambers began in
1988, using 1,400 seedlings from 19 half-sibling families and one full-sibling family (both parents
in common). Controlled exposure treatments consist of three levels of O3 (charcoal-filtered air,
non-filtered, and non-filtered plus 150 ppb), three levels of acidic precipitation (pH 53 to 3.5),
two levels of dry deposition (5% or 40% of ambient), and two levels of water availability (irrigated
every 2 or 3-4 weeks). No results are available yet from this study.
3.1.7 Summary
Several observations support the hypothesis that chronic atmospheric deposition of acidic or
acidifying compounds, such as H+, SO42*, NO3', and NH44, significantly alters soil chemical
properties. Trends similar to those that would be expected due to soil acidification were observed
along regional gradients of increasing SO42* deposition and along gradients in the northern
Appalachians where deposition of S042' is reasoned to increase due to increased cloud water
deposition. These observed trends include increases in soil total S, increases in soil exchangeable
Al, and decreases in soil exchangeable base cations (notably Ca and Mg). Soil solution Al3*
concentration is highly correlated with solution NO3' concentration, and it may be mobilized by
NO3'. Changes in soil chemical properties can also result naturally from changes in vegetation
and have been found to be highly variable on spatial scales as small as meters. Continued losses
of soil Mg may be a future problem with high-elevation soils. However, data are generally lacking
to link forest condition and deficient soil cations.
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Soil chemical changes can be induced with artificial acidification. Modeling projections and
literature reviews suggest that SO42' deposition may eventually lead to increased cation leaching
in the Southeast. The DDRP indicated that sites varied in their ability to retain atmospherically
deposited SO42', and that sites in the Northeast are already saturated with respect to SO42". Most
of the EFS sites were sustaining net losses of soil Mg; weathering resupply is still an unknown.
The ALBIOS studies sugges' f 'iat Al solubility increased with acinic deposition and that it may
be contributing to tree stress in some sensitive sites.
32 Roots and Mycorrhizae
The effects of pollutants on roots and mycorrhizae have been examined directly via controlled
exposure work with seedlings and indirectly through field surveys that correlate tree and root
conditions. Table 4 summarizes the FRP seedling studies on roots and mycorrhizae.
3.2.1 FRP Seedling Studies
Effects of Acidity
In the 13 seedling studies that examined the effects of simulated acid precipitation on roots, results
were highly variable. Miller et al. (WC09-1) found reduced root growth due to acidity for all
species of western conifers except Engelmann spruce. In contrast, Hogsett and Tingey (WC08-1)
observed mixed effects due to acidity, and Turner et al. (WC07-1) observed increased root growth
in three of four western conifer species.
Of six studies evaluating the effect of simulated add precipitation on red spruce roots, reduced
growth of roots due to acidity was found in one study (Patton et al., SP07-1), and increased fine
root branching, decreased coarse root growth, and decreased mycorrhizal infection were
reported in another study (Deans et al., SF14-19). The remaining four studies reported no effect
(Jacobson et al., SF06-1,2; Patton et al., SF07-2; Laurence et al., SF31-2; Thorton et al., SF27-3).
No effects were observed on roots of Fraser fir (Seller et al., SF13-1) or loblolly pine (McLaughlin
et al., SC04-1; Reinert et al. SC05-1).
Dean and Johnson (SC13, personal communication) reported increases in root length density of
slash pine exposed to increased acidity at a Gainesville, FL, site. The soils were sandy and low
in nutrients, and the root increases may have been a response to the additional N in the acid
treatments. Seedlings were grown in artificial potting media and not in naturally occurring soils
in many studies (most laboratory studies and most of the field studies except those of the Southern
Commercial Cooperative), and it is difficult to predict how increased acidity may interact with
the exchangeable cations or act as a N fertilizer in these potting mixtures. The effects of acidity
on soil nutrient cycling would occur relatively slowly, and effects may not become evident for
several years.
One seedling study found no effect of acid on numbers of mycorrhizal root tips in red spruce
grown in mixed soils collected from Mt. Mitchell, NC (Meier et aL, SF02-1). However, there was
an increase of the mycorrhizal species Cenococcum geophilum with increasing acidity. The acid
applications resulted in decreased soil pH and base saturation, suggesting that a change in
mycorrhizal-species associations may be induced by increased acidity.
The only meaningful conclusion at present is that there was no consistent direct effect of acidity
on roots across these seedling studies. Moore (1974), in a review of acidity effects on roots, stated
that often the effect of soil solution pH on roots is confounded with other chemical properties of
the soil, such as the nutrient concentrations to which roots are exposed. Furthermore, the use of
artificial potting media in these studies precludes assessment of the effects of simulated acidic
deposition on roots due to soil changes.
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Effects of Ozone
Thirteen seedling studies examined root growth (root length or mass increment) as a function of
controlled exposures of O3; seven of these studies observed some reduction in growth. All five
loblolly pine studies showed negative effects due to O3 (Mclaughlin et al., SC04-1; Kress et al.,
SC06-3; Wiselogel, SC02-1.2; Reinert et aL, SOQS-1). Dean and Johnson (SC-13) found no effect
on slash pine roots. One study reported reduced mycorrhizal colonization of roots of loblolly
pine seedlings due to O3 (McLaughlin et aL, SO04-1).
All three red spruce studies reported no change in root growth due to O3 (Alscher et aL, SF16-5;
Patton et aL, SF07-2; Laurence et aL, SF31-2). Laurence et aL's (SF31-2) data indicated an 18.5%
increase (p - 0.11) in root mass in their highest versus lowest O3 levels (averaged over the three
acid levels), which we reported as a significant effect in Table 4 due to our more liberal criteria.
No effect of O3 on roots was reported for Fraser fir (Tseng et aL, SF13-2).
In other species, reduced root growth was observed for trembling aspen (Kamosky et al.,
EH03-5), Douglas-fir (Miller et al., WC09-1), ponderosa pine (Miller et al., WC09-1; Hogsett
and Tingey, WO08-1), and lodgepole pine (Hogsett and Tingey, WO08-1). Generally, the
remaining western conifers showed no consistent effects on roots due to O3.
Effects of O3 on root growth thus appear to be species specific. Loblolly pine appears to be
sensitive, and red spruce appears to be tolerant.
322 FRP Mature Tree Studies
As was seen in seedlings, declining trees have been found to have declining root systems. Wargo
et aL (SF15-1) studied trees showing 11% to 50% crown deterioration on ML Abraham, VT.
They observed fewer live fine roots, fewer mycorrhizal tips, and fewer mycorrhizae types in red
spruce with declining crowns than in trees with healthy crowns.
323 NCASI Results
In a study funded by NCASI, Sharpe et al. (1989) studied the effects of O3 on C gain and allocation
in loblolly pine seedlings using CO2 tracers. Seedlings were exposed for 12 weeks to either
120 ppb of O3 for 7 hrs, 5 days a week, or to charcoal-filtered air. Sharpe et aL reported that O3
substantially reduced transport of photosynthate to roots of Cottonwood and of loblolly pine
seedlings.
In another study, four families of loblolly pine seedlings were exposed to one of six O3 concentra-
tions for 12 hrs, 7 days a week, during 3 consecutive growing seasons (NCASI, 1989). Ozone
concentrations ranged from approximately 0.5 to 2.0 times ambient. After the first year, seedlings
in each family showed visible injury. After two growing seasons of exposure, two families showed
decreases in stem and branch dry weight when exposed to non-filtered air compared with
seedlings exposed to charcoal-filtered air. The authors suggested that current ambient O3 levels
in the North Carolina Piedmont may suppress growth of some loblolly pine families.
3.2.4 ROPIS Results
In the ROPIS South study of O3, acidic precipitation, and soil Mg (described in Section 3.1.6),
root biomass, root length, and branching frequency of loblolly pine seedlings were not changed
significantly after one growing season. In contrast, increasing acidic precipitation and soil Mg
concentration resulted in a significantly greater number of mycorrhizal short roots, suggesting
that mycorrhizal infection was more sensitive to these treatments than was seedling root growth.
In the ROPIS East study, the proportion of different red spruce mycorrhizal morphotypes
counted in the Oa horizon changed significantly in response to O3 alone, pH alone, and O3 and
pH in combination. The morphotypes are not taxonomically classed to species but simply as class
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A, B, C, etc. Therefore, the only meaningful interpretation at present is that interactions of O3
with morphotypes led to increases and decreases in both growth and frequency.
325 Summary
Short-term responses of seedling root growth to simulated acid precipitation were highly variable.
Direct and consistent Effects of acidity on growth or mortality of roots were not evident in these
studies. However, indirect effects via changes to soil chemistry (S and N fertilization, loss of
cations, and mobilization of Al) should not be discounted. Such changes will probably require
several years of treatments because most soils are buffered against rapid changes in pH. The use
of artificial potting media common in most of the seedling studies precludes assessment of the
effects of simulated acidic deposition on roots due to soil changes.
Root growth of loblolly pine, trembling aspen, Douglas-fir, ponderosa pine, and lodgepole pine
seedlings was reduced by O3. A possible mechanism appears to be reduced C translocation to
roots. Mycorrhizal frequency may be reduced and morphotype distributions may be altered by
O3; however, this work is still preliminary.
33 Altered Carbon Allocation
Carbon allocation includes components of photosynthesis and respiration as well as biomass
allocation within the tree. The effects of atmospheric deposition on C allocation can be examined
directly via seedling exposure studies and mature branch exposure studies, and indirectly via field
surveys and measures on trees in environments with varying pollutant exposures. The special
case of roots has been discussed above.
33.1 FRP Seedling Studies
The following discussion is derived primarily from the results in Table 4. The most recent findings
of the Southern Commercial Forest Cooperative are summarized in Table 11.
Effects of Acidity
FRP studies have examined the effects of acidity on C allocation in seedlings by measuring
photosynthesis, foliar mass and condition, and stem growth. In this section, we discuss each of
these responses in turn.
Photosynthesis. Only data from loblolly pine and red spruce seedlings were available at the time
of this summary. Of eight seedling studies that examined the effects of acidity on photosynthesis,
none observed decreases in photosynthesis expressed on a leaf-area basis due to increased acidity.
Four studies showed increases due to increasing acidity (Eamus and Fowler, SF14-9; Kohut et
al., SF31-1; McLaughlin et al., SC04-1; Flagler, SC14), and four showed no effect (Richardson
and Sasek, SC07-6; Chappelka et al., SC15-7; Seiler et al., SF13-1; Thornton et al., SF27-3). Of
studies showing increased photosynthesis rates, progressive increases were observed at relatively
low acid levels (pH 45 and 43)(McLaughlin et al., SC04-1, and Flagler et al., SC99-20).
Increases in photosynthesis due to acidity may be due to a fertilizer effect of N or other nutrients.
Two of the studies reporting increased photosynthesis also measured growth responses. Kohut
et al. (SF31-1) reported data that indicated increased growth due to increased acidity at the
highest O3 levels (2-times-ambient O3); however, no growth trends due to acidity were apparent
at lower O3 levels. McLaughlin et al.'s (SC04-1) data indicated increased growth responses at
moderate levels of acidity (pH 4.5 versus 5.2).
The increases in photosynthesis at higher acidities may also be related to changes in leaf chemistry
or physiology. Jacobson et al. (SF06-1.2) showed that foliar N increased due to nitric acid
application. Flagler (SC14) and Chappelka (SCL5, cited in Flagler et al., SC99-20) observed no
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acid effect on chlorophyll content, while Reardon et aL (SC12, cited in Flagler et al., SC99-20)
did observe increases in chlorophyll at pH 43 and 33 compared with pH S3. McLaughlin
(SC04-1) observed no effect of acidity on stomatal conductance, but Eamus and Fowler (SF14-9)
observed enhanced stomatal conductance and higher chlorophyll contents in green needles
remaining on seedlings that had suffered foliar necrosis due to acidic ousts of pH 25 versus pH
5.0.
Eamus and Fowler (SF14-9), when expressing their photosynthesis data on a chlorophyll-content
basis instead of a leaf-area basis, observed decreased photosynthesis rates associated with
increasing acidity. These observed decreases contrast with their observations of increasing
photosynthesis due to acidity when photosynthesis was expressed on a leaf-area basis. Therefore,
the measure of photosynthesis used should be considered when evaluating results.
Foliar mass and condition. Fourteen studies that reported data on the effects of acidity on foliar
mass showed varied results. Simulated acid precipitation had mixed effects on loblolly pine
foliage mass. Researchers found increases (Chappelka et aL, SC15-1), decreases (Reardon et
al., SC12-1), and no effect on foliage mass (McLaughlin et aL, SC04-1; Kress et al., SC06-3;
Reinert et al., SC05-1; Flagler et al., SC14). Red spruce showed either no effect of increased
acidity (Laurence et al., SF31-2; Kohut et al., SF31-1; Patton et aL, SP07-2), or decreases in foliage
mass (Patton et al., SF07-1). Sulfuric acid of pH 23 increased red spruce needle abscission
(Jacobson et al., SF06-1).
The effects of acidity on hardwoods varied across species. Black cherry (Davis and Skelly,
EH01-1), white ash, yellow birch, and sugar maple (Jensen and Dochinger, EH06-1) had reduced
foliage mass due to acidity. White oak, shagbark hickory, American beech, and European beech
appeared to be insensitive (Jensen and Dochinger, EH06-1). Red maple and sweetgum appeared
to have increased foliage mass due to acidity (Davis and Skelly, EH01-1).
Eleven seedling studies examined foliar condition (typically as discoloration) as a function of
acidity, negative effects signify chlorosis and, in some cases, necrosis. Generally, negative effects
on foliage condition occurred at or below pH 3.0. No study showed enhanced foliage conditions
relative to control treatments. Hardwoods showed no negative effects of acidity on foliage
condition (i.e., stipple, adaxial yellowing, necrosis, or fleck). Other responses appeared to be
species specific. When comparing species common to different projects, foliage response to
acidity appeared to be more consistent within a given species than were other responses, such as
growth. Both Hogsett and Tingey (WC08-1) and Turner et al. (WC07-1) reported increased
foliar injury for western red cedar and western hemlock, but Douglas-fir and ponderosa pine
were not affected (injury was not specified, but all western conifer seedling studies considered
banding, chlorotic mottle, tip necrosis, pigmented mottle, necrotic mottle, chlorosis, bud break,
senescence, and abscission in their injury assessments). However, Miller et al. (WO09-1)
observed increased foliar injury to Douglas-fir, ponderosa pine, white fir, and Engelmann spruce.
Red spruce foliage was sensitive in three studies where low pH levels (pH 2S) were used (Leith
et al., SF14-6; Chen and Wellburn, SF14-7; Jacobson et aL, SP06-1.2), and insensitive in Patton
et al.'s (SF07-2) study in which a higher pH level (pH 3S) was used. Jacobson et al. (SF06-1^2)
observed that acid-induced foliar injury to red spruce was significantly greater for sulfuric acids
than for nitric acids. Two studies found that southern pine foliage was insensitive to solutions of
pH 33 (Kress et al, SC06-3; Flagler, SC14).
Stem growth. Seventeen studies examined seedlings for various changes in growth of stems, total
mass, stem diameter, or stem height as a function of acidity. A total of 24 species were tested
under varying periods of growth and exposure conditions. Although responses were somewhat
variable, most studies showed no effect on growth.
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In seven studies with red spruce, one reported a decrease in stem growth, four reported no change,
and two reported reduced stem growth due to acidity. These observations contrast with the
observations of increased photosynthesis due to acidity for red spruce, since increased growth
would be expected due to the increased rates of photosynthesis. Seiler et al.'s (SF13-1) data
indicated reduced stem growth for Fraser fir.
The spruce and fir studies itTf used potted seedlings that should not have been nutrient deficient.
Seedlings grown in artificial potting media may not be appropriate for growth response studies
because one mechanism for changes in tree condition may be a fertilizer effect on nutrient-poor
soils. Increased growth could occur with additions of acid in soils where N or S is limiting. Either
increased stem growth or no effects were observed in the eight southern pine studies. The
southern pine studies that reported increased stem growth used seedlings planted in natural soil
(Kress, SC06-3; Dean and Johnson, SC13; Wright et al. and Chappelka et al., SC15-6.7), indicating
a fertilizer effect.
Douglas-fix, western red cedar, and Engelmann spruce appeared to show some increased stem
growth due to increased acidity, but the remaining western conifers appeared to be insensitive
(Hogsett and Tingey, WC08-1; Miller et al., WC09-1). Black cherry (Davis and Skelly, EH01-1),
white ash, and sugar maple (Jensen and Dochinger, EH06-1) showed reduced stem growth due
to acid. Yellow birch and sweetgum showed increased stem growth (Jensen and Dochinger,
EH06-1). Other hardwood species showed no changes in stem growth response to pH 3.0 versus
4.2.
Variability. Seedling response to acidity was highly variable across both studies and species.
Sources of variation not under experimental control, or at least not available to be evaluated in
this document, include: stage of phenological development; degree of environmental stress (i.e.,
moisture, temperature, nutrient, and light); length of treatment exposures; level of treatment
(mean and extremes); length of time between treatment and assessment; rooting medium and
size of pots (if used); degree of mycorrhizal infection; and genetic family (in the case of species
that have wide range of occurrence or have been hybridized, such as loblolly pine). Shafer et al.
(1989) examined the variation in response of loblolly pines from the seedling projects in the
Southern Commercial Research Cooperative. Specific genetic families were chosen on the basis
of geographic range, availability of a large number of seeds, and information about O3 sensitivity.
Shafer et al. reported substantial variation in growth response of loblolly pine seedlings across
the projects examined, particularly in the response to O3 between field and laboratory studies
and among laboratory studies conducted at different sites. However, when Shafer et al. examined
responses from one laboratory project that used continuously stirred tank reactors (which afford
the greatest amount of environmental control), responses were typically repeated in the two years
the same experiment was performed. From these findings, seedling response is expected to be
somewhat predictable within a species, but the exact response depends on a number of factors
other than treatment levels.
Effects of Ozone
As was found for acidity, the effects of O3 on C allocation in seedlings have been measured on
photosynthesis, foliar mass and condition, and stem growth. In this section, we discuss each of
these responses.
Photosynthesis. Seven of 10 studies demonstrated some suppression of net photosynthesis due
to increasing O3 concentration. All five loblolly pine studies reported decreased photosynthesis
due to O3 (McLaughlin et al., SC04-1; Kress et al., SC06-3; Richardson and Sasek, SC07-6;
Wiselogcl ct al., SC02-1; Chappelkaet al., SC15-7). Preliminary results from these studies suggest
that reductions in photosynthesis often were progressively greater with increasing concentrations
of Cb, and ambient concentrations reduced photosynthesis when, compared v/ith below ambient
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concentrations. Reductions in photosynthesis of southern pines due to ambient O3 were more
apparent in recent studies by Flagler et al (SC99-20).
Shortleaf pine photosynthesis was also sensitive to O3 (Flagler, SC14). White oak (Foster et al.,
EH06-2) and red spruce appeared less sensitive than other species. Although by our criteria we
report a trend of declining photosynthesis due to O3 in Laurence et aL's (SF31-2) red spruce data
and in Tseng et aL's (SF13-2) Eraser fir data, in neither study was the effect statistically significant.
Tseng et aL (SF13-2) reported large photosynthesis suppressions (over 40%) due to O3. Kohut
et aL's (SC31-1) data, which were results from the second year of exposures of the same seedlings
used by Laurence et aL (SF31-2), did not demonstrate a suppression of photosynthesis with
increasing O3. Furthermore, Thornton et aL (SF27-3) did not detect an O3 effect on photosyn-
thesis of red spruce seedlings exposed to ambient levels on top of Whitetop Mountain, VA.
Therefore, with respect to photosynthesis, red spruce and white oak seedlings appear to be
tolerant to O3, but southern pines appear to be sensitive.
Foliar mass and condition. In the IS seedling studies that examined foliage mass as a function
of O3, no increases in foliage mass were reported. Douglas-fir, ponderosa pine, lodgepole pine,
western hemlock, and western red cedar were exposed to O3 by Hogsett and Tingey (WC08-1),
and all five of these western conifer species appeared to be sensitive to O3. Decreased bud
elongation and decreased needle dry weight were commonly observed. Six of eight loblolly pine
studies reported reduced foliar growth, increased foliar chlorosis, or increased needle loss
(Reinert et al., SC05-1,5; Kress et al., SC06-3; Reardon et al., SC12-1; Wiselogel et al., SO02-2;
Wright et al., SC15-6). Wright et al. (SC15-6) demonstrated that sensitivity of loblolly pine also
depended on genetic family. All three red spruce studies reported no effects of O3 on foliage
mass (Patton et aL, SF07-2; Laurence et aL, SF31-2; Koh'ut et aL, SF31-1). Hardwood response
varied by species. Species that appeared to be sensitive under these exposure regimes included
white ash, yellow birch, sugar maple, red maple, black cherry, and white oak (Jensen and
Dochinger, EH06-1; Davis and Skelly, EH01-1).
Eleven of the 13 seedling studies that examined foliage condition as a function of O3 reported
negative effects (e.g., increases in chlorosis, necrosis, or loss of foliage). Sensitive western conifer
species included ponderosa pine (Hogsett and Tingey, WC08-1), white fir, and subalpine fir
(Miller et al., WC09-1). Only one of three red spruce studies reported negative effects: Fincher
et al. (SF16-4) found increased mesophyll cell damage. Both loblolly pine studies reported
increased needle abscission, increased banding, and chlorosis (Kress et al., SC06-3; Wiselogel et
al., SC02-1.2). Increased banding, chlorosis, and necrosis to foliage were also reported for slash
pine (Flagler, SC14). As can be seen in Table 4, every hardwood species except red oak was
sensitive (Le., showed some combination of increased fleck, stipple, adaxial yellowing, or
necrosis) in Davis and Skell/s (EH01-1) study, and half the hardwood species showed increased
fleck in Jensen and Dochinger's (EH06-1) study. More recent data from open-top chambers
show that foliar stippling of black cherry and yellow-poplar seedlings was significantly reduced
by filtering O3 from ambient air at sites in Pennsylvania (Skelly et al., EH04-4).
Stem growth. Of 21 seedling studies that examined changes in stem mass, total mass, stem
diameter, or stem height as a function of increasing O3,12 showed reductions in at least one
growth measure. Western conifer species showing decreases in these measures included
ponderosa pine and western hemlock (Hogsett and Tingey, WOOS-1), and possibly Douglas-fir
(Miller et aL, WC09-1). White fir and Engelmann spruce showed some increased growth due to
O3 (Miller et aL, WC09-1). Stem growth of red spruce and Fraser fir appeared to be generally
insensitive to O3 (Tseng et aL, SF13-2).
Seven of eight loblolly pine studies reported reduced stem growth due to O3 (McLaughlin et al.,
SG04-1 lab; Reinert et al.r SC05-1,5; Kress et al., SC06-3; Wiselogel et aL, SC02-1^ Wright et al.,
SC15-6). Shortleaf pine was showed no response to O3 (Flagler, SC14), but slash pine stem
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FRP FOREST EFFECTS REPORT
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growth was reduced (Dean and Johnson, SC13). As can be seen in Table 4, half of the hardwood
species showed reduced growth due to O3. Variability in seedling stem growth as a function of
O3 appears to be primarily a function of species. Of species that responded similarly in at least
two studies, red spruce, sweetgum, and yellow-poplar showed no growth response, and loblolly
pine, ponderosa pine, and yellow birch showed decreased growth (Jensen and Dochinger,
EH06-1; Davis and Skelly, EH01-1; Karnosky et al., EK03-5). In open-top chambers in Pennsyl-
vania, Skelly et al. (EH04-4) observed increased stem diameter growth and increased height
growth of black cherry and possibly yellow-poplar seedlings when O3 was filtered from ambient
air. The differences were apparent in 1988, a year with high levels of O3, but they were not evident
in 1989, a year with lower O3 levels.
Variability. In general, seedling response to O3 appeared to be much less variable than responses
to acidity. Seedlings showed increases in growth or photosynthesis in response to O3 much less
frequently than they did to acidity. Although response to O3 appeared to be species specific,
studies using the same species typically reported results that agreed qualitatively (i.e., in the
direction of response). The same is not true for seedling response to acidity. The quantitative
seedling response to O3 appears to be fairly complex. For example, responses of loblolly pine
vary as a function of genetic family. The effects of O3 may interact with age of needles, and effects
may carry over from the previous year (Flagler et al., SC99-20). Kress et al. (SC06)(reviewed in
Flagler et al., SC99-20) observed a nearly linear effect of O3 on photosynthesis, needle length,
and needle number on first flush foliage. The second flush foliage shows no impact of O3 except
in the 3-times-ambient treatment. However, the third and fourth flush needles are 127% longer
and photosynthesize at a higher rate (36%) when high-03 treatments are compared with ambient
treatments.
Acidity and O3 did not interact to any great degree, and any reported interactions were neither
consistent nor easily interpretable. Compared with acidity, O3 may act more directly on seedlings
(e.g., on leaf condition, photosynthesis, and growth) or have more acute effects (e.g., on
membranes of leaves). Acidity may act through more indirect mechanisms (e.g., winter injury or
soil chemistry) and may interact with other variables (temperature or nutrient availability) to a
greater degree than O3 does. Thus, research on acidity may require longer study intervals to test
for effects than O3 studies require.
3.3.2 FRP Mature Tree and Sapling Field Studies
Five FRP studies described in this section present some physiology or growth data of sapling and
mature trees from sites receiving differing amounts of acidic deposition.
McLaughlin et al. (SF10-3)(Table 9) compared red spruce saplings 1.5 to 2.5 m in height growing
at an elevation of 1935 m with saplings growing at 1720 m on Clingmans Dome in the Southern
Appalachians. They reported reduced photosynthesis and growth at low light levels and in-
creased respiration. Although McLaughlin et al. did not present data to show that greater
deposition of acidity occurs at the higher site, this is probably a reasonable assumption since the
higher site receives 30% more precipitation. In addition, an increase in the Al:Ca ratio in soils
and foliage was observed at the higher site.
Aroundson et al. (SF31-3)(Table 9) examined the time course of needle physiology and chemistry
of red spruce in three naturally regenerated stands, one at Whiteface Mountain, NY, and two at
low-elevation sites in Maine (the latter do not receive cloud water deposition). The authors
reported lower rates of net photosynthesis, lower sugar contents, earlier starch depletion, and
lower C assimilated per unit of foliar N at Whiteface Mountain, and they concluded that these
trees have a reduced capacity to assimilate C compared with red spruce at the two sites in Maine.
Amundson et al. also observed higher foliar N but lower foliar P, Ca, and Mg at Whiteface
Mountain than at the Maine sites.
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Joslin et aL (SF27-l)(Table 5) studied mature red spruce trees at a site near the summit of
Whitetop Mountain, VA, that, because of wind and topographic conditions, received 15% more
SO42* and 29% more NO3' than another nearby site. The site with greater deposition showed
decreased foliar growth, decreased needle retention, and reduced foliar nutrient levels of Mg,
Zn, and Ca. Like McLaughlin et aL (SF10-3), Joslin et al. reported increased soil Al (up to 200
M) levels at the high-deposition site.
Pregitzer et aL (EH03-4)(Table 5)and Witter (EH03-2)(Table 7) evaluated sugar maple stands
along a gradient bf increasing acidic deposition from Minnesota to Michigan. They reported no
changes in growth along the gradient, but they found increases in the amount of cycled N and S
in litterfall and throughfall as well as increases in cation fluxes in throughfall along the gradient
Loiicks at al. (EH05-8)(Table 7) observed no trend in mortality rates of hardwood trees greater
than 20 cm in diameter along a deposition gradient from Arkansas to Ohio. However, along the
whole gradient, they observed increased mortality from 1978 to 1987 when compared with rates
from 1968 to 1977. Loucks et aL did not use direct measures of tree death, but rather they
estimated year of tree death using criteria such as condition of the remaining tree, cross-dating
of wood cores, or aging saplings that were released by the tree's death. These results are still
preliminary.
333 FRP Branch Exposure Studies
Branch exposure chambers (BECs) are a method for assessing mature tree response to air
pollutants. Branches of mature trees growing in the field are contained inside chambers in which
the ambient air can be controlled. Either pollutants can be removed via filters or pollutants can
be added to obtain higher than ambient concentrations. The reliability of data from BEC studies
depends on the degree to which a branch is autonomous in meeting its C requirements. With
respect to C translocation, preliminary results of fall 14C02 pulse-trace experiments indicated a
high degree of autonomy of mature branches of ponderosa pine growing under uncontrolled field
exposure conditions (Houpis and Cowles, WC20-1). After eight days of potential C translocation,
less than 1% of the labeled C was found in needles, buds, or stems of the three branch whorls
closest to the labeling point. Thus, since branches appear to be autonomous with respect to C
movement, BECs should be appropriate for study of some aboveground air pollution effects, at
least for mature ponderosa pine.
The BECs.can be used as a.cuvette to measure CO2 uptake of whole branches. Houpis and
Cowles (WC20-1) enclosed the foliage of a 5-yr-old potted ponderosa pine sapling in a BEC, and
continuously monitored CO2 uptake for three months. Figure 19 shows a typical diurnal trend
in CO2 uptake and illustrates variation due to light and temperatures inside the BEC.
Effects of Acidity
Vann et aL (SF34-1) used BECs to expose branches of four mature red spruce to treatments in
the summer of 1988. Treatments were: 1) ambient gases and cloud water, with a chamber (control
treatment); 2) ambient gases and cloud water, without a chamber (open treatment); 3) ambient
gases with cloud water excluded (dry treatment); 4) charcoal-filtered air with cloud water
excluded (filtered treatment); 5) charcoal-filtered air with cloud water excluded and deionized
water added as mist (misted treatment)(see Table 9). Foliar samples collected at the end of
treatments showed significant treatment effects: misted branches had (he highest concentrations
of total chlorophyll and carotenoids, and open branches had the lowest (p = 0.01). Cuticle
thickness-measurements followed a similar trend (Berlyn, 1989).
These data suggest that the measured foliar characteristics improved when ambient cloud water
was excluded and that foliar characteristics were best when exposed to deionized mist compared
with other treatments. Furthermore, treatments appeared to affect the degree of winter injury
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~l
Ld
v:
<
h-
CL
Z>
CNJ
O
o
2
0
-4
CO2 Flux
" f t •
/ V ' • V '
: » it * ».
- Ozone Level /
.1 * '
» % 0
* •*
%
# •
60
40 O
NJ
O
20 ^
m
0 np
m
i-
~20 ^
~0
-40 go
400 600 800 1000 1200 1400 1600 1800 2000
TIME OF DAY
Figure 19. A diurnal patter of CO2 uptake and O3 concentration inside a branch exposure
chamber on ponderosa pine. The midday depression in CO2 uptake is due to high
temperatures (38°C). Key; a, increasing CO2 uptake and light intensity, sunrise;
b, shaded by adjacent building; c, light intensity increased; d, peak CO2 uptake;
e, late-afternoon recovery, f, decreasing CO2 uptake and light intensity at sunset
(from Houpis and Cowles, WC20-1).
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incurred during the following winter. Foliage from "clean" treatments (filtered, misted, and dry)
had significantly less winter injury than foliage exposed to ambient cloud water (control and open;
p = 0.10). The levels of winter injury in dry treatment and the filtered treatment were between
the clean treatment and the control treatment (Figure 20). Degree of winter injury, however, was
not significantly correlated with the cuticle and wax data of Berlyn (1989); the best correlation
was with total cuticular layer (r = -0.59; p < 0.10).
Effects of Ozone
Wiselogel (SC18-3) found that photosynthesis was lower for sapling loblolly pine branches
exposed to 2J-times-ambient O3 than for those exposed to ambient O3 or to charcoal-filtered
air. Figure 21a illustrates typical daily patterns of photosynthesis by O3 treatment and in relation
to light. Figure 21b shows differences in light intensity from ambient among chambers due to
both the chamber skin and shading. In addition, although the chambers tracked ambient light
similarly, light intensity varied up to 20% among chambers on the same tree. Differences in light
intensity among chambers may complicate interpretation of results because light may influence
the rate of photosynthesis irrespective of O3 treatment, especially if light levels are below
saturation (photon flux density 1400/*mol/m2/s; Teskey et al., 1986). In turn, the rate of photosyn-
thesis may also affect the rate of O3 uptake and thus the level of O3 stress.
In contrast to Wiselogel's (SC18-3) results for photosynthesis, Vann et al. (SF34-2) found that
the concentration of total chlorophyll and carotenoids in the foliage of mature red spruce trees
was not significantly different between branches exposed to ambient versus charcoal-filtered air.
33.4 ROPIS Results
In the ROPIS South study, five half-sibling loblolly pine families were exposed to O3 for three
growing seasons. After the first growing season, seedlings grown with ambient-plus-60 ppb O3
showed decreases in stem and root biomass compared with seedlings receiving ambient or
charcoal-filtered air, and there was a significant family x O3 interaction. During the second and
third growing seasons, only family differences were statistically significant. In harvesting at the
end of the second growing season, seedlings grown with ambient-plus-60 ppb O3 showed
significant decreases in stem and root biomass. After the third growing season, there were
consistent, but not statistically significant, decreases in all but stem biomass measures for
seedlings grown under ambient-plus-60 ppb O3. Similarly, loblolly pine seedlings exposed to
2-times-ambient O3 had a 13%-18% reduction in biomass compared with seedlings in charcoal-'
filtered air after two years.
No statistically significant growth responses to acidity were observed in loblolly pine seedlings in
the ROPIS South study. In addition, rainfall chemistry had no significant effect upon either the
visible coloration or the pigment concentrations of needles. However, results indicated sig-
nificantly less chlorophyll a (7%), chlorophyll b (10%), and carotenoids (3%) in second-year
needles of seedlings growing in the Mg-deficient soil compared with seedlings in a high-Mg soil.
In the ROPIS West study, one year of O3 and simulated acid precipitation exposures equal to
levels currently observed in the southern Sierra Nevada Mountains did not significantly affect the
growth of ponderosa pine seedlings. Elevated O3 did cause visible injury symptoms on ponderosa
pine foliage, showing the susceptibility of this species to O3 and suggesting that tree growth effects
may be found in subsequent years of this experiment. No visible effects of acidity were observed.
In the ROPIS East study, red spruce saplings had significantly lower rates of net photosynthesis,
as estimated from whole-tree CO2 uptake and total foliage mass after two years of exposure to
O3. These results are considered preliminary because photosynthesis rates were calculated based
on estimated needle mass. Photosynthesis rates will be recalculated when the saplings are
harvested, and needle mass will be measured at the end of the experiment. In the first year of
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7
-
fi-6? .
6
-
r^\
l 5
0
E 4
C
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exposure, there were significant acid and acid x O3 effects on terminal length and first-order
shoots. The nature of the interaction has not yet been evaluated, but for the main effect of acidity,
lengths were shortest in the highest pH treatment. In addition, antioxidant ratios changed with
increasing O3 exposure in a pattern consistent with other studies. Finally, simulation model runs
predicted that the 2-times-ambient O3 treatment during the full growing season would reduce
carbon gain by 8%, with maintenance of aboveground tissue maintained at the expense of root
tissue.
3.3.5 Summary
More than half of the measures of foliage growth, stem growth, and root growth in the FRP
seedling studies showed no effects of increased acidity in simulated acid precipitation. Of the
remaining measures, where simulated acid precipitation produced either increases or decreases
in growth of seedlings, southern pines and western conifers appeared to respond with increased
growth more often than decreased growth (with the exception of western conifer root growth).
Red spruce, Fraser fir, and eastern hardwoods more often showed decreased growth. Foliar
injury occurred in most species (at or below pH 3.0), and SO42' appeared to be more harmful to
red spruce seedlings than NO3*. Increased photosynthesis of seedlings due to increased acidity
of simulated acid precipitation was observed in four of eight studies of red spruce and southern
pines. Some increases in chlorophyll content, foliar N, and stomatal conductance were also
observed.
Ozone may reduce seedling growth as well as photosynthesis in both seedlings and branches of
mature trees. Loblolly pine and ponderosa pine were particularly sensitive; western hemlock,
other southern pines, and several hardwood species may also be sensitive. Levels required to
produce reductions were typically higher than ambient concentrations in many of the seedling
reports summarized in Table 4; however, more recent results (Flagler et al., SC99-20) suggest
that southern pines may be affected at ambient O3 levels. In addition to the reductions in
aboveground growth, O3 also appeared to cause reductions in root growth of sensitive species,
such as loblolly pine, trembling aspen, ponderosa pine, cottonwood, Douglas-fir, and lodgepole
pine.
3.4 Winter Injury
Winter injury was assessed for red spruce in seedling studies, branch exposure studies, and in
measures made on branches of mature red spruce growing in the field. In seedling studies, injury
is typically assessed via controlled overnight freezing of clipped branchlets followed by measure-
ments of electrolytes leached into water. In field studies, injury is assessed by examining needle
necrosis.
3.4.1 FRP Seedling Studies
There is evidence that exposure to acid mists delays the development of cold tolerance in red
spruce seedlings during the autumn and early winter (Cape et al., SF14-4; see Figure 22). Cape
et al. used acid composed of equimolar solutions of ammonium sulfate and nitric acid. Although
the effects of acidity, S, and N could not be separated, Cape et al. noted that their results were
consistent with the hypothesis that N delays frost hardiness. Subsequent data from experiments
in 1988 indicate that S rather than N caused the delay in frost hardening of red spruce seedlings
(N. Cape, personal communication). This result occurred even at neutral pH: ammonium sulfate
mist delayed hardening relative to water, ammonium nitrate, or nitric acid.
Jacobson and Lassoie (SP06-3) did not observe any difference in the development of cold
tolerance of red spruce seedlings as a result of simulated acidic mists applied during the growing
season. Jacobson and Lassoie exposed seedlings to acidic mists of pH 2.8,3.5, and 4.2 and tested
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Date
9/21 10/5 10/19 11/2 11/16 11/30
0
-10
-20
-30
-40
treatment pH
O 2.5
—©— 2.7
-50
3.5
—Q—
-60
LT(
Figure 22. Delayed cold tolerance in red spruce seedlings exposed to one of six acidic mists
and tested during the autumn hardening peroid. Vertical axis is the threshold
temperature for a 50% kill, assessed via electrolyte leaching (from Cape et al.,
SF14-4).
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cold tolerance of current-year needles to freezes twice in the autumn (September and November)
and twice in the spring (early and late April). Jacobson and Lassoie did not freeze test their
shoots to sufficiently low temperatures to induce tissue death in their November test. Therefore,
Jacobson and Lassoie's data do not adequately address autumn hardening, but they suggest that
acidic mists do not affect cold tolerance by April.
3.42 FRP Mature Tree and Sapling Field Studies
Vann et al. (SF34-2) studied mature branches of red spruce on Whiteface Mountain, NY. They
reported decreased winter injury for treatments in which cloud mists and O3 were filtered out of
the branch chambers and clean mist was added when compared with both mature branches in a
chamber with no pollutants removed and unchambered branches (see Figure 20).
Sheppard et al. (SF14-2) analyzed foliage samples that were collected during the fall and winter
hardening period from normal-appearing red spruce trees at Whiteface Mountain, NY, New-
found Gap, NC, and Kilmun, Scotland, and from trees showing visible decline at Clingmans
Dome, NC. The shoots were subjected to simulated overnight freezing, and necrosis was visually
assessed 14 days later. The authors reported several observations: shoots withstood progressively
colder temperatures throughout the hardening period; trees on average hardened to nearly the
same temperatures at all sites; the start of hardening differed across sites; and there were
significant differences among trees (lethal temperatures varied by 10°C among trees at Whiteface
Mountain during December and January). Shoots from Clingmans Dome, the decline site, were
at least as hardy as shoots from Newfound Gap. Most importantly, for trees at both Whiteface
Mountain and Newfound Gap, the minimum temperature at which trees hardened decreased at
a rate that was faster than the rate at which the temperature dropped, as shown in 22 years of
temperature data (Figure 23). However, there were occasional minimum temperatures low
enough to cause necrosis for at least 10% of the tested trees. Sheppard et al. concluded that their
data provided "...only weak evidence to support the hypothesis that the trees that are suffering
decline in the high Appalachians are predisposed to direct freezing injury." The authors acknow-
ledged that this study did not test winter desiccation or premature dehardening, and that they
may have been sampling only surviving shoots which would be somewhat frost tolerant. Although
the authors performed a preliminary study to determine the effects of collection, shipping, and
storage time on frost hardiness of needles, they did not discuss how well visible assessment of
necrosis after 14 days would assay freezing injury in the field or how comparable results are to
those from cell electrolyte leaching methods.
From 1986 to 1988, Wilkinson (SF19-3) studied 30-year-old red spruce growing in 12 rangewide
provenances on a plantation in northern New Hampshire. Wilkinson made observations of winter
injury to needles and measured radial increment and height growth. In each of the three years,
radial increment was smallest for trees with the highest proportion of damaged needles in their
upper crown or with the most frequent winter injury. A similar but less pronounced pattern was
observed for height growth. Growth losses following winter injury were greater for trees in pure
red spruce provenances than for trees in provenances that were introgressed with black spruce.
The results support the contention that winter injury could be an initiating or perpetuating factor
in red spruce decline.
Nicholas and Zedaker (SF25-1) reported on the physical effects of winter injury on trees. They
stated that during ice storms up to 10 cm of ice could accumulate on trees. The extra weight of
the ice, combined with winds measured as high as 95 km/hr, could cause tops to break off.
3.43 ROPIS Results
In the ROPIS East study, the cold tolerance of current-year needles of red spruce saplings showed
no consistent differences during spring (April to early May) in response to O3 or simulated acidic
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Whitefaee Mountain,NY
10 lowest daily minimum
temperatures over 22 years
LTxj of
20 trees
1987/88
• + * * f
80^76
Newfound Gap , NC
10 lowest daily minimum
temperatures over 22 years
) IT* of
( 20 trees
t ' 1987/88
85
1988
Figure 23. Change in LTio (lethal temperature from a 10% kill, assessed visually) of shoots of
mature red spruce from Whiteface Mountain, NY, and Newfound Gap, NC, during
fall hardening period (straight lines). lines with high-frequency variation show his-
torical low temperatures recorded for each site. Numbers indicate years in which a
recorded temperature dropped extremely low (from Sheppard et al., SF14-2).
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precipitation treatments either alone or in combination. In contrast, more consistent and
significant differences in cold tolerance were evident due to acidity during fall (September to
early November): trees receiving pH 3.1 rain were less hardy than trees receiving either pH 4.1
or 5.1 rain, especially during middle to late October.
In the ROPIS West study, one year of O3 and simulated acidic precipitation exposures at levels
equal to those currently observed in the southern Sierra Nevada Mountains did not have any
apparent effect on severity of winter injury in ponderosa pine seedlings.
3.4.4 Summary
Simulated acidic precipitation decreased cold tolerance of red spruce seedlings in controlled
tests, and ambient cloud water concentrations increased freezing injury to branches of mature
trees under controlled exposures. The seedling response appeared to be fairly linear as acidity
increased, starting as high as pH 4.0. Other results indicate that S042"acids induce greater injury
than NO3" acids. Extrapolation to field observations of declining trees may be questioned by the
study of Sheppard et al. (SF14-2) in which shoots of mature red spruce trees appeared to be able
to harden sufficiently to survive expected minimum temperatures. Support for extrapolation of
seedling data to mature trees is provided by the branch chamber studies of Vann et al. (SF34-2)
which indicate that winter injury on mature branches was associated with greater exposures to
ambient clouds and gases during the growing season.
3.5 Foliar Leaching
Foliar leaching refers to the dissolution and subsequent removal of nutrients from foliage by
solutions.
3.5.1 FRP Seedling Studies
Turner et al. (WC07-1) applied simulated acidic fog to western conifer species in 24 4-hr events
over an 84-day period. Compared with pH 5.6, the pH 3.1 treatment increased foliar throughfall
concentrations of K, Ca, and Mg in Douglas-fir. However, Turner et al. observed no concomitant
decrease in foliar concentrations, and, via studies of nutrient depletion of a hydroponic solution,
they estimated that root uptake could easily prevent foliar depletion due to leaching.
Patton et al. (SF07-1) exposed red spruce seedlings to 12.7 mm of simulated acidic precipitation
(S042":N03" of 1:1) once per week for 28 weeks. Two levels of acidity were tested: pH 3.0 and
4.2. The pH 3.0 treatment increased throughfall concentrations of iron (Fe) and Mn compared
with the pH 4.2 treatment for a measurement made at the end of the treatment period.
Jacobson et al. (SP06-1.2) reported decreased foliar K, Ca, and Mg concentrations in red spruce
seedlings that had been exposed to acidic mists of pH 4.2,3.4, or 2.6 for 6 to 19 weeks compared
with seedlings not exposed to mists. Continuous mists produced a greater reduction in nutrient
concentrations than intermittent mists. Jacobson et al. also observed acid-induced injury to
foliage, but they did not observe any effects on diameter or root growth in these short-term studies.
3.5.2 FRP Mature Tree and Sapling Field Studies
Joslin et al. (SF27-1) (Table 5) compared mature red spruce trees from two sites on Whitetop
Mountain, NY, that have different amounts of cloud water deposition. They reported increased
solution flux of SO42*, NO3'' and NH4 + to the forest floor and decreased foliar concentrations
of Mg, Ca, and Zn at the site with higher deposition. In a similar study of saplings on Whitetop
Mountain, Joslin et al. (SF27-5) reported that as the acidity of cloud water increased from
pH 4.6 to 2.9, throughfall concentrations of Ca increased 18-fold, and Mg increased 25-fold.
McLaughlin et al. (SFlO-3)(Table 9) reported decreased foliar Ca, Mg, and P concentrations in
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red spruce saplings at a high-elevation site that received 30% more rainfall than a similar site 250
m lower on Clingmans Dome, NC. The lower foliar Ca reflected less soil-exchangeable Ca at the
higher site. Soil-exchangeable P was greater and soil exchangeable Mg was no different at the
higher site.
Liechty and Mroz (EH03-3)(Table 5) observed positive correlations between SO42" deposition
and throughfall concentrations of Ca and Mg. However, the correlations were considered to be
weak.
3.5.3 IFS Results
The IFS project (described in Section 3.1.6) estimated that H + deposition to the forest canopies
ranged from 250 to 740 eq/ha/yr for wet deposition and from 350 to 1950 eq/ha/yr for total (wet,
dry, and cloud) deposition at 10 of the 17 intensive study sites, as shown in Figure 24 (Knoerr and
Conklin, 1989). In contrast, there was considerably less variation in the net canopy effect
(difference between total throughfall of base cations and total atmospheric deposition of base
cations, which estimates cation leaching from the canopy). The net canopy effect varied by a;,
a factor of two across the same 10 intensive study sites, as shown in Figure 25 (Ragsdale, 19b..
Furthermore, no trend in H+ deposition was evident across sites in the net canopy effect,
suggesting that H + deposition did not directly influence cation leaching.
3.5.4 ROPIS Results
In the ROPIS South study, nutrient concentrations of loblolly pine seedlings were not affected
significantly by acid, O3, or soil Mg after one growing season. In the ROPIS East study,
throughfall flux in red spruce sapling crowns was greater with pH 3.1 rain than with either pH 4.1
or 5.1, and concentrations were greater in 1988 than in 1987. Increasing O3 exposure appeared
to significantly increase the leaching of Zn from red spruce saplings. Foliar nutrition was
adequate to date, but K may become deficient due to a relatively small exchangeable pool in the
soil and a high plant demand.
3.5.5 Summary
There is evidence that precipitation acidity can increase foliar leaching, but not dramatically
(except for the study by Joslin et al., SF27-5), and the effects of canopy leaching on tree growth
and health are unclear. In chamber exposures, differences occurred among species in the effect
of acidic precipitation on foliar nutrient levels, with some studies showing increased nutrient
levels, some showing decreases, and most showing no effect. In the field, loading of H + and
throughfall enrichment of cations are at least weakly correlated in all of the reviewed studies.
Factors such as wash-off of dry deposition, damage to cuticles by the feeding activities of canopy
insects, or growth phenology, may partially mask leaching effects due to acidity.
3.6 Insects and Pathogens
Insects such as the spruce budworm, the balsam woolly adelgid, and the gypsy moth can kill large
areas of forests (Millers et al., 1989). The seven FRP studies available for this review (Table 10)
suggest that insects are abundant and may be a potential problem in specific areas. No relation-
ship between insects and air pollution has been found, and limited evidence that insects may be
affecting red spruce seedling survival is presented in this section.
Brack (SF02-3) found a remarkable absence of insects (less than 5% incidence) on red spruce
trees in the southern Appalachians. Hartman et al. (SF02-4) found two species of parasitic
nematodes at more than 80% of their high-elevation sampling sites in the southern Appalachians,
but frequency of both nematodes was either negatively or not correlated with tree decline indices.
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2,000
1,800
1,600
1,400
1.200
¦C
% 1,000
+
3= 800
600
400
200
0
0 cloud
dry
precipitation
DL WF LP GL NS CP
IFS site
ST, Smoky Mtns., NC
DL, Duke Forest, NC
WF, Whiteface Mtn., NY
LP, Oak Ridge, TN
GL, BF Grant Forest, GA
NS, Nordmoen, Norway
CP, Coweeta Hyd. Lab., NC
HF, Huntington Forest, NY
RA, Thompson Forest, WA
DF, Thompson Forest, WA
Figure 24. Deposition of H+ to forest canopies at 10 IFS intensive sites (from Knoerr and
Conklin, 1989).
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B NS
200 400 600
Net canopy effect (eq/ha/yr)
800
ST, Smoky Mtns., NC
WF, Whiteface Mtn., NY
RA, Thompson Forest, WA
HF, Huntington Forest, NY
NS, Nordmoen, Norway
DF, Thompson Forest, WA
CP, Coweeta Hyd. Lab., NC
GL, BF Grant Forest, GA
LP, Oak Ridge, TN
DL, Duke Forest, NC
Figure 25. Throughfall enrichment of base cations in 10 DPS sites, calculated as throughfali
and stemflow of base cations minus the total deposition (wet plus dry) to the
canopy (from Rags dale, 1989).
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Weidensaul et al. (SF08-10), in a survey on Whiteface Mountain, NY, detected some primary
pathogens such as a fir needle rust caused by Uredittopsis spp., but they concluded that insects
and facultative parasites were not important in causing decline. Knight and Grosman (SF05-15)
placed sticky-board, passive aerial barrier, pitfall, Malaise, and blacklight traps near mature red
spruce and mature balsam fir trees on Mt. Moosilauke, NH, and they conducted visual searches
of branches and lower boles of these trees. They found large numbers of Korschellellus gracilis
(Grote)(formerly known asHepialus gracilis and commonly called the swift moth or ghost moth).
Knight and Grosman concluded that K. gracilis is currently the most common and potentially
damaging insect species for red spruce and balsam fir.
Tobi et al. (SF99-7) demonstrated in laboratory studies that K. gracilis fed on roots, causing
girdling. This girdling in turn killed seedlings of red spruce, balsam fir, and white spruce. The
authors found similar symptoms on large numbers of dead seedlings in the field in spruce-fir
stands that were in the process of decline on Camel's Hump, VT.
Smith and Armstrong-Colaccino (SF05-12) did not observe any significant fungal infection, insect
infestation, or mechanical wounding of woody or fine roots of red spruce on Mt. Moosilauke,
NH. However, high densities of nematodes (10 times values found in Connecticut) were observed
in the forest floor. The proportion of nematodes that were pathogenic, if any, was not determined.
On Mt. Moosilauke, NH, and Whiteface Mountain, NY, at sites from 500 to 1300 m, Grehan
(SF99-16) found greatest numbers of K gracilis between 700 and 1100 m, where red spruce is the
dominant forest species. More larvae were found on the western windward slopes of Whiteface
Mountain, which are reasoned to receive higher levels of acidic deposition than the eastern slopes
due to winds and precipitation from the industrialized Midwest. Field and laboratory inocula-
tions of spruce seedlings with feeding larvae resulted in a significant increase in foliage dieback
and reduction of root mass and area. Grehan concluded that the potential impact of K. gracilis
on red spruce should be a primary consideration in any evaluation of the effect of atmospheric
deposition on high-elevation spruce-fir forests.
3.7 Reproduction and Regeneration
The hypothesis that acidic deposition may affect reproduction or regeneration was proposed
early in the program but was not explicitly tested. At least two studies examined aspects of
reproduction and regeneration.
Peart (SF05-1,4) surveyed red spruce and balsam fir seedling ( < 1 m tall) and sapling distributions
and growth patterns on the east slope of Mt. Moosilauke, NH. Red spruce seedlings occurred
at much lower densities than balsam fir, and densities of red spruce seedlings were greater at 990
m versus either 840 or 1140 m. Both species exhibited J-shaped age-class distributions at the
mid-elevation sites, as expected for stable populations. At low-elevation sites, both species
showed markedly reduced numbers of seedlings less than 15 years old. High-elevation sites were
not analyzed since red spruce was uncommon. Extension growth of seedlings and saplings of
both species declined with increasing elevation, and there was a trend of declining sapling growth
over the last five years. Growth of red spruce saplings was less than balsam fir, and crown
condition was poorer. The percent of saplings that were standing dead increased with elevation,
and overall the proportion of standing dead was higher for balsam fir than for red spruce.
Nicholas et al. (SF25-7) collected seeds in litterfall traps and also studied seedling survival in
undisturbed and cleared permanent plots in spruce-fir forests in the southern Appalachians.
They found that high proportions of Fraser fir (51% to 90%) and red spruce (54% to 74%) seeds
were empty, but this is reported to be typical given variations in climate and activities of seed
predators. Seed viabilities were higher than previous estimates made by the USFS, but were
within expected ranges (31% to 87% for Fraser fir; 82% to 96% for red spruce). Seedling
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densities varied by mountain. Both spruce and fir seedling densitk 'lowed overstory competi-
tion densities. Spruce densities decreased and fir densities increased with increasing elevation.
Seedlings germinated readily in the cleared and scarified plots. However, while spruce and fir
both germinated at plots in the Mt. Rogers National Recreation Area, only hardwood species
regenerated at cleared and scarified plots in the Black Mountains. Continued long-term monitor-
ing is needed to describe regeneration success of the southern spruce-fir forests; however,
seedfall, viability, and seedling densities indicate an active regeneration process.
3.8 Forest Condition Studies
Studies of forest condition in the United States, both FRP and non-Fx have been extensively
reviewed in MPO #1&2 (Reams et al., 1990). The following discus. > is condensed from
MPO #1&2 and from the summaries of FRP studies in Table 7.
3.8.1 Western Conifers
Chronic symptoms of O3 damage to ponderosa pine and Jeffrey pine in the San Bernardino
Mountains have been documented for over a decade (Miller et al., 1989)(Figure 26). Ponderosa
pine crown condition (based on chlorosis and numbers of needles retained) and radial growth
(based on tree cores) were assessed in five National Forests and two National Parks that form a
contiguous north-south 500-km corridor in the Sierra Nevadas (Peterson et al., WC26-3; Peterson
and Arbaugh, WC26-1). Foliar injury to ponderosa pine occurs over the 250-km southern portion
of the corridor (Peterson et al., WC26-3). Although increases in radial growth since 1950 were
observed as frequently as reductions over the entire corridor, reductions in growth occurred more
frequently in the southern area which is closer to sources of O3 pollution (Peterson and Arbaugh,
WC26-1). Graybill and Rose (WC24-1) compared actual radial growth to predicted radial
growth (using precipitation as an independent variable) for 41 sites in mixed forest stands
supporting mostly ponderosa pine and Douglas-fir on the Mogollon Rim and on geographically
isolated peaks in southeastern Arizona. Of the 22 sites on the Mogollon Rim, nine sites showed
reductions in radial growth and one site showed an increase; for the 19 sites in the in the peaks
to the southeast, 12 showed reductions and two showed increases. Cause of reduced growth was
not determined; however, increased competition, air pollution, and changes in growth/precipita-
tion relationships were suggested. Brubaker (WC25-1) observed increasing radial growth of
old-growth Douglas-fir since the 1880s at sites near Puget Sound, WA, and at HJ. Andrews
Experimental Forest in the Oregon Cascades. Causes of growth increases wrrc not determined
but were thought to be due to regional temperature increases.
3.8.2 Spruce-Fir
Reams et al. (1990) reviewed studies that indicate increases in mortality of red spruce at high
elevations in the northeastern United States since the early 1960s. At elevations above 950 m, the
percent of basal area of red spruce that is dead is much higher than that observed for other species
(Friedland, SP08-17). Reams et al. noted that a similar episode of high red spruce mortality
occurred in the Northeast during the period from 1871 to 1885. The exact cause of this mortality
is not agreed upon, but the spruce bark beetle is known to have contributed. For the more recent
episode of red spruce mortality, the cause of individual tree death has not generally been
described In the surveys reviewed by Reams et al.
Crown condition of forest stands that include red spruce has been evaluated in the southern
Appalachians (Bruck et al., SF02-5; Dull et aL, SF26-1; Nicholas et al., SF25-6; Nicholas and
Zedaker, SF25-1). Overall, no abnormally high proportions of dead red spruce have been
observed. High proportions of dead Fraser fir are correlated with balsam woolly adelgid
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35
30
25
•;=• 20
15
O
O
o
I
o
10
o
o
o
1978 1988
• O
o
o
o
50 60 70 80 90 100
Estimated Og exposure in ppb
(24-hr ave. during May-Oct., 1974-78)
110
120
Figure 26. Crown injury (combination of needle color, needle length, needle retention, and
branch mortality) as a function of O3 exposure to ponderosa pine in the San Ber-
nardino Mountains of California (from data presented in Miller et al., 1989).
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infestations. Recent declines in crown conditions of red spruce and Fraser fir are thought to be
due to droughts and ice storms.
Miller-Weeks and Cooke (VS14-3) surveyed crown condition of red spruce and balsam fir in
permanent plots at a wide range of elevations (300-1200 m) in New York, Vermont, New
Hampshire, Massachusetts, and West Virginia. Surveys have been conducted yearly since 1985.
The authors reported a deterioration of crown condition of red spruce and balsam fir over time
in all regions, little overall discoloration in the crowns was noted, but foliage loss due to branch
mortality or dieback was prevalent. However, there was no observed change in the number of
recently dead trees. Reams et aL (1990) reviewed studies that have described decreased radial
growth of red spruce and sometimes balsam fir in the northeast United States (see also Hornbeck
et al., VS06-5) and a slight reduction of radial growth of red spruce at the highest elevations in
the southern Appalachians. Initiation of growth reductions has been thought to be synchronous,
beginning in the early 1960s in the Northeast and in the mid-1960s in the southern Appalachians.
However, Reams et aL (1990) point out that many red spruce stands that showed growth decreases
after 1960 also show growth increases during the 1950s (see also Conkey and Keifer, SF05-13).
In addition, when individual trees or stands are examined, radial growth declines are not always
observed and declines that are observed do not always appear to occur synchronously. Reams
et al. list two hypothesized causes of red spruce radial growth reductions in the Northeast: stand
or release history and frequent winter injury events in the late 1950s and early 1960s. The cause
of reduced radial growth of red spruce at the highest elevations in the southern Appalachians is
uncertain since factors such as stand dynamics have not been assessed. However, air pollution,
climate, .and the effect of the balsam woolly adelgid on Fraser fir have been suggested as
contributing factors to the reported radial growth reductions of red spruce at the highest
elevations in the southern Appalachians.
3.83 Southern Commercial Pines
In an analysis of data from the Forest Inventory and Analysis (FIA) Research Work Unit at the
USFS Southeastern Forest Experiment Station, Sheffield et al. (1985) reported reductions in
radial growth between 1961-1972 and 1972-1982 for pine species growing on nonindustrial private
lands in the Southeast. To assess the effects of stand factors that might affect growth, Bechtold
et al. (VS-04) reanalyzed the FIA data set using linear models incorporating such factors as stand
age, stand density, site quality, mortality, and hardwood competition. Bechtold et al. concluded
that the adjusted mean growth of pines during 1972-1982 declined by 19% in natural loblolly pine
stands, 28% in natural shortleaf pine stands, and 28% in natural slash pine stands. Zahner et aL
(1989) used a linear aggregate model and accounted for only a portion of the observed decreases
in terms of identifiable factors such as tree age, drought, and stand density. Zahner et al.
concluded that the portion of the decline that was unaccounted for was due to unidentified
factors, possibly including air pollution. Reams et aL (1990) concluded that Bechtold et aL and
Zahner et aL still may not have adequately accounted for changes in stand density, particularly
since samples for the two periods of comparison were not taken from the same plots and appear
to represent different populations. Therefore, additional research is necessary before the causes
of the radial growth declines are identified.
3.8.4 Eastern Hardwoods
There is limited evidence of changes in forest condition in FRP studies of eastern hardwoods
(Reams et al., 1990). Increased rate of basal area growth was observed for most hardwood species
in the Northeast (Hornbeck et al., VS06-5). Witter et aL (EH03-2) observed no unusual patterns
of growth or mortality in their sugar maple and hardwood plots in the Michigan gradient. Leblanc
(EH05-7) observed radial growth reductions of black oak and white oak at sites along the Ohio
gradient that had molar Ca:Al ratios less than 0.25 in the top 50 cm of soil. In a study of
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yellow-poplar, white oak, chestnut oak, and northern red oak, Smith (1990) reported that trees
have become more sensitive to climate over the last 10 to 30 years. No coincident changes in
climate or stand structure occurred that may have influenced this change. Brooks (VS11-1)
studied forest growth along an atmospheric deposition gradient in Pennsylvania. Stand and
stocking density were the best predictors of growth variation, and there was no evidence of a
significant relationship between mortality and atmospheric deposition. Finally, in a North
American sugar maple research project conducted jointly by the United States and Canada, Allen
and Barnett (1989) reported that crown condition of sugar bushes and forest stands appeared
healthy, with 89% of the sugar bushes and 92% of the forest trees showing less than 10% crown
dieback.
3.8.5 Summary
Many FRP studies of forested regions produced results showing significant spatial or temporal
change in some measure of forest condition. Separating the changes due to natural causes from
any induced by air pollution is difficult. In the West, both increases and decreases in radial growth
over time have been observed at different sites. Areas in the southern Sierra Nevada show
reduced radial growth of ponderosa pine that may be related to foliar damage by O3. An O3
effect has already been documented in earlier studies in the San Bernardino Mountains. In the
spruce-fir forests in the Northeast, a recent increase in red spruce mortality at high elevations
and reductions in radial growth at high and low elevations appear to have occurred. Repeated
winter injury during consecutive or closely spaced years is one likely explanation for red spruce
mortality suggested by Reams et al. (1990) in MPO #1&2. Stand history was identified in
MPO #1&2 as a likely explanation of reduced radial growth of red spruce. Radial growth of
southern pines has declined recently on natural stands in the Piedmont. Again, the exact role of
natural factors is not yet clear, and relationships with air pollution have not been conclusively
demonstrated. Hardwoods have shown increased growth rates in recent years in the Northeast.
Along the Ohio River Valley, gradient reductions in radial growth of black oaks and white oaks
have been observed. The reductions appear to be correlated with low soil Ca:Al ratios.
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4 SUMMARY AND CONCLUSIONS
4.1 Purpose of this Document
The FRP was developed to determine the nature and extent of the effects of acidic deposition on
trees and forests of the United States. The purpose of this document is to address two environ-
mental policy questions:
L Is there significant forest damage in North America caused by acidic deposition, alone or
in combination with other pollutants?
2. By what mechanisms does acidic deposition, alone or in combination with other
pollutants, contribute to forest damage in North America?
Toanswer these questions, we first summarized research on changes in forest condition (dis-
cussed in Reams et al., 1990) and controlled exposures of seedlings to pollutants (discussed in
Peterson et al., 1989). We then discussed additional research on soil chemistry (Section 3.1),
roots and mycorrhizae (Section 3.2), altered carbon allocation (Section 33), winter injury
(Section 3.4), foliar leaching (Section 3.5), insects and pathogens (Section 3.6), reproduction and
regeneration (Section 3.7), and forest condition (Section 3.8). Here we summarize and then
integrate these findings to draw conclusions about the potential effects of atmospheric pollutants
on tree and forest condition.
42 Summary of Principal Findings
4.2.1 Soils v
Several observations support the hypothesis that atmospheric deposition of acidic or acidifying
compounds, such as H+, SO42", NO3', and NH4* significantly alters soil chemical properties.
Changes in soil chemistry similar to those that would be expected as a result of soil acidification
were observed, along four regional gradients of increasing SO42' deposition in eastern hardwood
forests. When compared with lower elevations on Mt. Moosilauke, NH, and Whiteface Moun-
tain, NY, changes in soil chemistry were observed at high-elevation sites where deposition of
SO42" increases due to increased cloud water deposition. The observed trends include increases
in soil total S along the eastern hardwood gradients, and increases in soil exchangeable Al and
decreases in soil exchangeable base cations (notably Ca and Mg) at the mountain sites. At high
elevations in the Appalachians, seasonal changes in soil solution Al3* concentration are highly
correlated with seasonal changes in solution NO3' concentration, suggesting Al3+ may be
mobilized by NO3.
Changes in soil chemical properties can result naturally and have been found to be highly variable
on spatial scales as small as meters. The observed trends in soil chemical properties could be
caused by factors other than atmospheric deposition, such as cation uptake by vegetation,
accumulation of litter, harvesting practices, and weathering. Data are generally lacking to link
deficiencies in soil cations with changes in forest condition such as mortality, reduced growth, or
damage to crowns.
Measurable soil chemical changes (i.e., decreases in base saturation, increases in exchangeable
Al, or increases in soil solution ionic concentrations) can be induced with additions of simulated
acidic solutions. In some cases, significant changes were not detected unless very acidic solutions
were applied (e.g., pH 23 versus 5S). In another case, a decrease of one pH unit (i.e., 43 versus
33) caused a decrease in exchangeable Ca and Mg and in base saturation. Applications of
solutions with acidities equal to those observed in throughfall solutions caused increased solution
concentrations of Ca, Mg, and Al in leachate (when compared with applications of distilled
water).
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422 Roots and Mycorrhizae
Responses of seedling root growth to simulated acidic precipitation were highly variable. No
consistent effects of acidity on growth or mortality of roots were evident in these studies.
However, most soils are buffered against rapid changes in pH. Thus, to detect potential effects
on roots via changes to soil chemistry (such as S and N fertilization, loss of cations, and
mobilization of Al), several years of treatment will be necessary.
Root growth of loblolly pine, trembling aspen, Douglas-fir, ponderosa pine, and lodgepole pine
seedlings was reduced by O3 levels above ambient. Reduced carbon translocation to roots is a
possible mechanism for this effect. Mycorrhizal frequency may be reduced and morphotype
distributions may be altered by O3; however, this work is still preliminary.
423 Carbon Allocation
In seedling studies, tested pH values ranged from 2.1 to 5.6, with typical values from pH 3.0 to
5.0. Compared with control treatments (i.e., the highest pH value used), most studies showed no
effects of increased acidity on foliage biomass, stem growth, or root growth. In studies where
effects were observed, southern pines and western conifers responded with increased growth
more often than decreased growth. Red spruce and black cherry more often showed decreased
growth than increased growth in experiments where pH 3.0 was the lowest pH value tested. Foliar
injury occurred in most species at or below pH 3.0. Increased photosynthesis of seedlings in
treatments with increased acidity of simulated acidic precipitation was observed in some studies
of red spruce and southern pines. Increased aboveground growth coupled with no apparent
effects on belowground biomass in western conifers at pH 2.1 compared with pH 5.6 indicates
that changes in carbon allocation patterns occurred.
Ozone exposures in seedling studies ranged from charcoal-filtered air to 320 ppb, with typical
values ranging from charcoal-filtered to 3-times-ambient concentrations (ambient site concentra-
tions ranged from 33 to 48 ppb). Compared with control treatments (i.e., the lowest O3 level),
O3 exposure led to decreased growth in most studies. Loblolly pine, ponderosa pine, and western
hemlock showed decreases in above- and belowground growth. In addition, loblolly pine showed
reduced photosynthesis. Photosynthesis was not measured for ponderosa pine and western
hemlock. Most eastern hardwood species tested showed foliar injury in response to O3, and
several hardwood species showed decreases in stem mass. Levels of O3 required to produce
reductions were typically higher than ambient concentrations, although recent results showed
decreased photosynthesis in seedlings and branches of mature loblolly pine at ambient O3
concentrations (i.e., 40-50 ppb).
4.2.4 Winter Injury
In a controlled test of simulated acid precipitation, increasing acidity decreased the rate of
development of cold tolerance of red spruce seedlings. Seedling response was fairly linear as
acidity increased, starting as high as pH 4.0. Solutions containing sulfuric acid caused greater
injury than solutions containing nitric acid. When ambient cloud water was filtered from branch
exposure chambers, freezing injury decreased for branches of mature red spruce in the field.
Although hardening rates differed among sites, shoots of mature red spruce trees appeared to
be able to harden sufficiently to survive expected minimum temperatures. Reductions in radial
growth, basal area increment, and height growth were associated with degreeof over-winter injury
to needles of 30-year-old red spruce trees growing in a provenance test site in northern New
Hampshire.
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42£ Foliar Leaching
Precipitation acidity can increase foliar leaching, but the effects of canopy leaching on tree growth
and health are unclear. In chamber exposures, species differences were observed with respect
to the effects of acidic precipitation on foliar nutrient levels. Some studies showed increased
nutrient levels, some showed decreases, and most showed no effect In the field, H + loading and
throughfall enrichment of cations were correlated in all of the reviewed studies, indicating a
possible effect of precipitation acidity. However, other processes may contribute to the enrich-
ment of nutrients in canopy throughfall, such as wash-off of dry deposition, damage to cuticles
by feeding insects, and increased nutrient uptake.
42Jb Forest Condition
In this section, we examine forest regions of the United States for consistency between a change
in forest condition and the presence of atmospheric pollution.
San Bernardino Mountains and Southern Sierra Nevada
There is consistency between foliar damage (chlorotic mottle, premature needle loss, shortened
needle length, and increased branch mortality) and exposure to O3, both spatially and temporally,
for ponderosa pine and Jeffrey pine in the San Bernardino Mountains of southern California.
Foliar condition improved over a spatial gradient of decreasing O3 concentration from west to
east (estimated O3 dose, 24-hr average, for May-October from 1974-1978, ranged from 110 to SO
ppb from west to east) and over a temporal gradient of decreasing concentration with time from
1974 to 1988.
There is some spatial consistency between O3 exposure and symptomatic crown injury (needle
chlorosis and needle retention) to mature ponderosa pine within a 500-km north-to-south
corridor in the southern Sierra Nevada. In stands showing symptomatic O3 injury, chlorosis is
greatest in the southern sites and needle retention is greatest in the northern sites. Oi'one
exposure increases in the same direction as the injury increases (i.e., from north to south).
High-Elevation Spruce-Fir Forests of the Northern Appalachians
In high-elevation forests in the northeastern United States, red spruce mortality increased in the
1960s. Whether or not the change is outside the range of natural variability is not known, since
mortality episodes of similar magnitude occurred in the late 1800s. However, the earlier episode
occurred at lower elevations, and climate and bark beetles were suggested causal factors. In the
Adirondack and Green Mountains, the percent of standing dead red spruce increases with
elevation. These increases in standing dead are consistent with increasing levels of wet deposition
of ions at elevations above cloud base (800 to 1200 m). However, other factors that increase with
elevation, such as increased wind, lower temperatures, shallower soils, and shorter growing
seasons, may be associated with the higher proportions of standing dead red spruce.
There is a weak spatial consistency between chemical j" Terties of forest floors and mineral soils
in high-elevation, spruce-fir forests on Mt. Moosilauk; "I, and Whiteface Mountain, NY, and
cloud water deposition. Soil chemical properties show c ased base saturation and increased
exchangeable A1 at high elevations when compared with low elevations.
Eastern Hardwoods
There is consistency between spatial trends in atmospheric deposition of SO42' and spatial trends
in soil chemical properties or nutrient cycling in trees. In hardwood forests in Michigan,
concentrations of S in foliage and litterfall and the amount of S and N cycled in forest litter
increased as SO42* deposition increased. In the Ohio River Valley, increased concentrations of
total soil S, decreases in soil pH, and increases in soil C have been found. In Pennsylvania, sap
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concentrations of Ca in red maple varied directly with atmospheric deposition of Ca. Although
substantial changes in forest condition have yet been associated with deposition patterns, recent
reductions in radial growth of white and black oak are associated with low soil Ca:Al ratios.
Research is still in progress.
Southern Pines
FLA surveys of natural southern pine species on nonindustrial private land in the Piedmont
indicate a reduction in average radial increment in the last survey (1977-1985) when compared
with earlier surveys (1957-1966 and 1966-1977). In one study, the observed changes in radial
growth were modeled using a number of factors known to affect growth (such as tree age, density,
and drought). Part of the growth decline was attributed to increased competition, part to drought,
and part to unknown factors. Air pollutants have been suggested as one of several possible causes
of this reduction. Because O3 exposures to these stands are unknown both spatially and
temporally, the analyses cannot be considered to be a demonstration of spatial or temporal
consistency between change in forest condition (reduced growth) and O3.
43 Answers to Policy Questions
In this section, we address the policy questions stated earlier: that is, is there significant forest
damage in North America caused by acidic deposition, alone or in combination with other
pollutants, and by what mechanisms might acidic deposition and other pollutants contribute to
forest damage?
Uncertainty exists in our answers to these questions for several reasons. First, our understanding
of acidic deposition and O3 exposures in many of the forest regions studied is incomplete. At
many of the sites where forest condition is assessed, atmospheric deposition and O3 levels must
be inferred from data collected at sites in other locations. In some regions, such as those
containing mountainous terrain, deposition can vary considerably over short distances. For
example, at two sites within 100 m of each other on top of Whitetop Mountain, VA, annual
deposition of SO42', NO3', and NJ-Lt"1" to the forest floor differed by 15%, 29%, and 45%,
respectively.
Second, as seedling studies show, most effects from pollutants at ambient levels are relatively
subtle when compared with the known effects of other environmental variables such as drought
stress, light, temperature, nutrients, insects, pathogens, and competition.
Third, most FRP studies examined the more specific scientific questions, such as the effects of
pollutants on a specific seedling function or descriptions of crown condition at a given location.
Program time lines and costs limited coordination between pollutant monitoring and the studies
of forest condition mentioned above, considerably different exposure regimes were used among
the seedling studies, and additional information necessary to interpret likely causes of observed
change was not collected in surveys of forest condition. Thus, subtle effects of pollutants on
forests are difficult to detect.
43.1 Acidic Deposition
Significant forest damage (change greater than expected) is thought to be occurring among red
spruce at high elevations in the Appalachian Mountains of the northeastern United States, based
on three observations of forest condition: 1) high proportions of standing dead red spruce basal
area above 1000 m in the Adirondack and Green Mountains; 2) reductions in radial growth of
red spruce in many regions; and 3) tree condition visually assessed to be poor or declining over
time. Although the range of possible natural variation in forest condition may be quite large, the
range of variability we would expect under normal conditions is probably somewhat less than
what is possible. The observed changes in red spruce at high elevations may not be outside the
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range of natural variability, but it does appear that they are above normal expectation and are
consistent with increasing levels of wet deposition. In addition, experiments with red spruce have
linked acidic mists to decreased cold tolerance in seedlings and ambient cloud water to increased
winter injury to mature branches. Winter injury has been associated with reduced red spruce
growth in a field provenance study. These experimental and field observations are consistent
with the hypothesis that repeated winter injury, exacerbated by high levels of acidic cloud water
deposition, may contribute to reduced radial growth and deteriorated crown condition in red
spruce. To date, no experimental evidence has demonstrated that acidic deposition may be a
direct cause of increased red spruce mortality.
Significant forest damage has not been detected in the eastern hardwoods. No relationship has
been established between biomass increment and spatial patterns of sulfate deposition in
Michigan. However, reduced radial growth has been observed in black and white oaks on sites
with low Ca^Al ratios (0.25 molar ratio in the upper 50 cm of soil) in the Ohio River Valley.
432 Ozone
Ozone has been shown to cause foliar injury, decreased growth, and increased mortality of
sensitive individuals of specific forest tree species. Extensive research efforts have previously
demonstrated that O3 has caused foliar injury to sensitive individuals of white pine over much of
its range in eastern North America. Ozone has also caused foliar injury, reduced needle
retention, decreased photosynthesis, and reduced growth eventually leading to increased mor-
tality (caused by the western pine beetle) of ponderosa pine and Jeffrey pine in the San
Bernardino Mountains in southern California. In controlled exposures, O3 has caused reduced
growth of ponderosa pine seedlings. Ozone occurs in concentrations sufficient to cause visible
injury to vegetation in most of eastern North America. Ambient O3 levels have been shown to
cause increased foliar injury to seedlings of several hardwood species and reduced growth of
black cherry and possibly of yellow-poplar. However, O3 has not been shown to be related to
changes in forest condition in the hardwood forests, nor does O3 appear to be influencing growth
of red spruce.
An argument may be made that O3 may be causing growth reductions in the southern pines,
despite the fact there are no data to directly demonstrate this. Three FRP observations support
this conjecture: 1) in selected instances, loblolly pine seedlings and mature branches of loblolly
pine show reductions in photosynthesis at ambient O3 levels (i.e., 40-50 ppb); 2) a reduction in
radial growth of loblolly pine has been observed in natural stands in the Piedmont; and 3) poten-
tially phytotonc levels of O3 have been measured in this region (43-51 ppb). However, other
information limits this conjecture. A number of the seedling studies did not show reductions in
photosynthesis at O3 levels twice ambient. The reductions in growth in loblolly pine stands may
be due to natural factors, since stand density changes and increased competition from hardwoods
have not been accounted for in these studies. Until these uncertainties are resolved, ozone-in-
duced growth declines of loblolly pine in the South cannot be established.
4.4 Recommendations for Future Research
4.4.1 Soils
The hypothesis that atmospheric deposition of SO42", NO3', and possibly NH4* can alter soil
chemical properties in a relatively short time period (within the lifespan of trees) is still tenable.
The relationship between soil chemistry and tree condition is not clear. Leaching rates of SO42'
below the rooting zone should be assessed in those areas that are suspected to be losing cations.
Mineral weathering rates should be estimated (or a method developed to estimate mineral
weathering) to determine if leaching rates will result in base cation depletion. The relationship
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between N cycling and Al mobilization in the high-elevation Appalachian forests deserves further
attention.
4.4.2 Roots
Future work addressing the effects of acidic deposition on roots should incorporate root growth
systems that more realistically reflect the soil nutrient regimes to which roots are exposed in the
field. Research of basic root growth processes and interactions with nutrient availability should
also be supported. Our lack of understanding of root functioning and growth limits our ability
to interpret results from the FRP seedling studies.
Reduced carbon translocation to roots caused by ozone appears to be a tenable hypothesis that
should be evaluated in future research. 14C tracer work would help answer questions of
short-term carbon allocation. We still lack understanding of C and energy requirements of roots
for growth, maintenance, and transport processes; both applied and basic research in this
important area of tree ecophysiology should be supported.
4.4 J Carbon Allocation
Results appear to be more consistent and interpretable when exposures are performed for at
least two growing seasons. Several years of exposure may be required to obtain data sets that
show the effects of O3 at ambient levels, if any effects exist. Ozone studies should attempt to
define minimum levels at which a species will show chronic reductions in physiological or growth
processes. Several studies that examined tissue chemistry results suggested O3 effects on starch,
protein, N concentrations, mesophyll cell disruptions, and cuticle wax formation. Process-level
studies should be encouraged. Studies of acidic precipitation should focus on interactions with
nutrient availability and growth, particularly in red spruce stands at high elevations. Areas that
warrant attention include leaching of Mg and Ca, SO42* deposition, and the interactions of Al,
Ca, and NO3'.
4.4.4 Winter Injury
The hypothesis that winter injury of red spruce at high elevations is increased by acidic com-
pounds in cloud water and precipitation appears to have received the most experimental support
of all the hypotheses tested in the FRP. Continued research of the mechanism of winter injury
is recommended. The extent to which trees may be affected in the field should be determined.
The linkages, if any, between winter injury, reduced radial growth, and tree mortality must be
examined if the Policy Questions raised at the beginning of the FRP are to be answered.
4.4£ Foliar Leaching
In future leaching studies, foliar chemistry and soil nutrient availability should also be evaluated.
Red spruce at high elevations, where cloud water inputs are high and nutrients may already be
limiting, are most likely to be affected by foliar leaching.
4.4.6 Forest Condition
Studies should test whether changes in foliar and crown condition, mortality, and growth rates
are associated with each other, and the factors responsible for variability in these measures of
forest condition should be evaluated. For example, better identification and characterization of
natural factors associated with mortality are necessary (i.e., information necessary to characterize
competition, soil moisture availability, climate, and atmospheric deposition), as are empirical
models of mortality rates.
The usefulness of dendroecology research can be enhanced in several ways. Work is needed to
determine the magnitude of potential bias in dendroecology procedures and the implications of
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extrapolating modeling results to future climate scenarios. Threshold and cumulative weather
variables should be developed. Stand history must be adequately considered in relationship with
climate and atmospheric deposition, and better growth and yield data and analyses might indicate
that many growth reductions are associated with natural factors. Neither dendroecology nor
forest mensuration alone has produced an approach that satisfactorily accounts for regional scale
changes in forest productivity. On one hand, traditional dendroecology studies do not reveal
stand dynamics information over time; only survivors are included (usually dominant or overstoiy
survivors), and these individuals may not reflect stand response. On the other hand, forest growth
and yield models usually relied only stand dynamics while ignoring the influence of climate and
other exogenous effects. Thus, since each approach currently quantifies the effects of important
sources of variation that the other ignores, research combining forest growth and yield informa-
tion with dendroecology is critical. A good starting point would be to develop sampling and
analysis methodologies that address both low-frequency (stand dynamics) and high-frequency
(climate) variations in tree-ring series.
4.4.7 Atmospheric Deposition
Current atmospheric deposition monitoring emphasizes point measures (mountain tops) and
surrogate surfaces (i.e^ not tree foliage). A shift in emphasis should be made to intensive studies
of the cloud deposition process. Although monitoring of cloud deposition is useful, studies of
deposition mechanisms would help to determine spatial patterns of atmospheric input into
different types of forest canopies. Dry deposition of S and N should be included in estimates of
atmospheric deposition.
4.4.8 Controlled Exposure Studies
Future seedling exposure studies can be improved in several ways. First, a primary source of
variation in plant response is the plant material itself. Careful selection and randomization of
plants prior to treatment would help to alleviate this nonuniformity. Second, correct interpreta-
tion of seedling responses among sites, or among years at a given site, requires adequate
characterization of the microclimates of each site. That is, the spatial and temporal differences
in factors such as light, temperature, and humidity must be known.
The statistical power of an experiment to detect treatment differences should be considered when
planning research, and it should be computed at the conclusion of each project. In the absence
of formal statistical significance due to low power, evidence of treatment effects may still be
present in the form of trends or patterns, and these trends should not be overlooked.
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5 ACKNOWLEDGMENTS
We thank first the Principal Investigators and report authors for providing us with manuscripts
and written reports of their ongoing research. We recognize that many of you made special efforts
to deliver reports to us within limited time frames. We thark also the Program Managers,
Research Cooperative Managers, scientists, peer reviewers, and other reviewers who provided
new insights, corrections, and constructive comments during the review process. We are grateful
to James Boyle for his review of many of the reports and to C. Jeffrey Brandt for his assistance
with the historical perspectives and for his many helpful comments. We also appreciate Margi
Bohm's help with the ozone exposure section. Finally, we thank Bryn Juntunen, Kristina Heike,
Brenda Huntley, Greg Baumgardner, Don Richards, Susan Buhler, and Rob Matthews for
invaluable assistance in the production of this report.
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Dissertation, The University of Tennessee, Knoxville, TN. 363 pp.
Smith, W.H., and A. Armstrong-Colacdno. Pathological survey of the spruce-fir forest on Mt.
MoosUauke m New Hampshire. Forest Response Program Report. U.S. Environmental
Protection Agency, Corvallis, OR. [SF05-12]
Smlthson, P.C., and W.P. Robarge. Short-term solution responses to additions of add and salts
in spruce-fir forest soil horizons of NC and VA. Forest Response Program Report. U.S.
Environmental Protection Agency, Corvallis, OR. [SF12-6]
Smlthson, P.C., W.P. Robarge, and J.D. Josiin. Solution chemistry of lysimeter leachates from
Mt. Mitchell, NC and Whitetop Mtn., VA: Forest Response Program Report. U.S.
Environmental Protection Agency, Corvallis, OR. [SF12-7]
Strader, R.H., D. Blnkley, andC.G. Wells. 1989. Nitrogen mineralization in high elevation forests
of the Appalachians. I. Regional patterns in southern spruce-fir forests. Biogeochemistry
7:131-145. [SF17-1]
Temple, PJ. 1988. Injury and growth of Jeffrey pine and (pant sequoia in response to ozone and
addicmist. Environ. Exp. Bot. 28(4)323-333.
Temple, PJ. 1989. Responses of ponderosa pine seedlings to the interactions of ozone, wet and
diy aadic deposition, and soil moisture availability. Response of Plants to Interactive
Stresses (ROPIS) Program Report.
Teskey, R.OnJA. Files, LJ.Samuelson, and B.C. Bonprten. 1986. Stomatal and nonstomatal
limitations to net photosynthesis in Pinus laeda L. under different environmental conditions.
Tree Physiol 2:131-14Z
Thornton, F.C., PA. Pier, and CX McDufEe. Effects of douds and ozone on spruce seedlings: A
Field Chamber Stucfy at Whitetop Ml., Virginia. Forest Response Program Report. U.S.
Environmental Protection Agency, CbrvalHs, OR. 18 pp. [SF27-3]
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Tingey, D.T., and G.E. Taylor, Jr. 1982. Variation in plant response to ozone: A conceptual
model of physiological events, pp. 113-138. In: M.H. Unsworth and D.P. Ormrod, eds.
Effects of Gaseous Air Pollution in Agriculture and Horticulture. Butterworth Scientific,
London.
Tobi, D.R., W.E. Wallner, and B.L. Parker. The conifer swift moth, Hepialus gracilis, and
spruce-fir decline. Forest Response Program Report. U.S. Environmental Protection
Agency, Corvallis, OR. [SF99-7]
Tseng, E.C., J.R. Seiler, and B.I. Chevone. 1988. Effects of ozone and water stress on green-
house-grown fraser fir seedling growth and physiology. Environ. Exp. Bot. 28(1):37-41.
[SF13-2]
Turner, D.P., D.T. Tingey, and W.E. Hogsett 1988. Acid fog effects on conifer seedlings. In:
Proceedings of the International Union of Forestry Research Organizations Conference on
Air Pollution and Forest Decline, Oct., 1988, Interlaken, Switzerland. [WC07-1]
Ulrich, B. 1983. A concept of forest ecosystem stability and of acid deposition as driving force
for destabilization, pp. 1-29. In: B. Ulrich and J. Pankrath, eds. Effects of Accumulation
of Air Pollutants in Forest Ecosystems. D. Reidel Publishing Co.
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1986 Forest Damage Survey in Europe. United Nations Environment Program and
Economic Council of Europe, Global Environment Monitoring System, Geneva, Switzer-
land.
Vann, D.R., A.H. Johnson, and R. Strimbeck. Effects of ambient air quality at Whiteface Mt. on
the foliage of mature red spruce. Forest Response Program Report. U.S. Environmental
Protection Agency, Corvallis, OR. [SF34-1]
Vann, D.IL, A.H. Johnson, G.R. Strimbeck, and M.M. Dranoff. Effects of ambient levels of
airborne chemicals on the foliage of mature red spruce. Forest Response Program Report.
U.S. Environmental Protection Agency, Corvallis, OR. [SF34-2]
Vogelmann, H.W., GJ. Badger, M. Bliss, and R.M. Klein. 1985. Forest decline on Camels
Hump, Vermont. Bull. Torrey Botan. Club 112:274-287.
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National Acid Precipitation Assessment Program, Washington, DC.
Vong, RJ., S. Cline, G. Reams, J. Bernert, D. Charles, J. Gibson, T. Haas, J. Moore, R. Husar,
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research. EPA/600/3-89/030, U.S. Environmental Protection Agency, Environmental Re-
search Laboratory, Corvallis, OR.
Vong, RJ., B.H. Bailey, M J. Makus, and V.A. Mohnen. In press. Factors governing cloudwater
composition in the Appalachian Mountains.
Wargo, P.M., D.R. Bergdahl, C.W. Olson, and D.R. Tobi. Root vitality and decline of red spruce.
Forest Response Program Report. U.S. Environmental Protection Agency, Corvallis, OR.
[SF15-1]
Weidensaul, T.C., A.M. Fleck, D.M. Hartzler, and C.L. Capek. Quantifying spruce decline and
related forest characteristics at Whiteface Mountain, New York. Forest Response Program
Report. U.S. Environmental Protection Agency, Corvallis, OR. [SF08-10]
Wells, C.G., W.P. Robarge, and LAV. Zelazny. Soil and plant tissue chemical properties as-
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Response Program Report. U.S. Environmental Protection Agency, Corvallis, OR. [SF21-
4]
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Wilkinson, R.C. The efTects of winter injury on growth of 30-year-old red spruce from twelve
provenances growing in the northern New Hampshire. Forest Response Program Report.
U.S. Environmental Protection Agency, Corvallis, OR. [SF19-3]
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Corvallis, OR. [SC18-3]
Wiselogel, A.E., and F. Fong. Comparison of 12-week-old and 1-year-old seedlings of loblolly
pine response to ozone fumigation. Forest Response Program Report. U.S. Environmental
Protection Agency, Corvallis, OR. [SC02-2]
Wiselogel, A.E., J.K. Bailey, RJ. Newton, and F. Fong. Growth responses of loblolly pine (Pinus
taedal) seedlings to three concentrations of ozone. Forest Response Program Report. U.S.
Environmental Protection Agency, Corvallis, OR. [SC02-1]
Witter, J., G. Mroz, and K. Pregitzer. Michigan gradient case history study for the NAPAP
Assessment Plan. Forest Response Program Report. U.S. Environmental Protection
Agency, Corvallis, OR. [EH03-7]
Witter, J., K. Pregitzer, and G. Mroz. Effects of an air pollution gradient on northern hardwood
forests in the northern Great Lakes region.: A summary for MPO1 and 2. Forest Response
Program Report. U.S. Environmental Protection Agency, Corvallis, OR. [EH03-2]
Woodman,J.N. 1987. Pollution induced injury to North American forests: Facts and suspicions.
Tree Physiol. 3:1.
Wright, I*M^ R. Meldahl, B.G. Lockaby, F. Thornton, and A.H. Chappelka. The influence of
acid precipitation and ozone on nitrogen nutrition of young loblolly pine. Forest Response
Program Report. U.S. Environmental Protection Agency, Corvallis, OR. [SC15-6]
Zahner, R, J.R. Saucier, and R.K. Myers. 1989. Tree-ring model interprets growth decline in
natural stands of loblolly pine in the southeastern United States. Can. J. For. Res. 19:612-
621.
Zedaker, S.M., N.S. Nicholas, C. Eagar, P.S. White, and TJE. Burk. 1988. Stand characteristics
associated with potential decline of spruce-lir forests in the Southern Appalachians. In:
G.D. Hertel, tech. coordin. Proceedings of the US/FRG Research Symposium: Effects of
Atmospheric Pollutants on the Spruce-fir Forests of the Eastern United States and the
Federal Republic of Germany. October 19-23,1987, Burlington, VT. General Technical
Report NE-120, USDA Forest Service, Northeastern Forest Experiment Station, Broomall,
PA. [SF25-4]
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7 APPENDICES
7.1 Appendix A: Assessment of Data Quality
The goal of the FRP quality assurance (QA) program is to ensure that data used for policy
formulation are technically sound and of known and documented quality. The FRP QA program
was developed using existing EPA guidance (e.g., EPA 1976,1979,1982,1983,1986a,b, 1987).
The FRP QA program, which is outlined in the FRP QA Implementation Plans (EPA, 1986b,
1987), focused on the measurement process. Thegoal was to cany out operations and procedures
so that the data produced were of specified quality within a stated level of uncertainty. Data
quality was specified quantitatively as precision and accuracy for each measured variable. The
specifications were developed through a concensus of scientists and expressed as data quality
objectives. Precision was estimated by repeated measurements of the same materials using the
same methods. Accuracy was estimated by the difference between a measured value and a
primary standard, reference material, or equivalent method.
7.1.1 Use of Data Quality Assessments
The purpose of data quality assessment was not to reject project data or results, but to improve
data by providing real-time information for principal investigators to use in monitoring and
controlling variation due to operational or measurement procedures. The data quality objectives
were used as program goals, rather than as boundaries for accepting and rejecting data. In fact,
one purpose of the data quality assessments was to evaluate the degree to which data quality
objectives could be realistically attained; for example, application of a pollutant at target value
_±. 10% (Peterson et al., 1989).
The QA staff summarized data quality assessments from each project and advised the authors of
this document as requested. The authors evaluated the significance of the QA findings within
the context of the whole study, making no attempt to discount project data and results solely on
the basis of data quality assessments. Instead, the QA information was used with other informa-
tion in evaluating and interpreting project results.
7.1.2 Quality Assurance Activities
Four general types of activities were carried out to assess data quality: planning, on-site auditing
and performance evaluations, comparability studies, and QA documentation. Each of these are
described briefly in the following paragraphs. Further details can be attained from MPO #1&2,
MPO #3, and final QA reports that are now being written.
The first activity, QA planning, required projects to prepare a QA project plan. The QA staff
reviewed each plan and made recommendations for improvement if necessary. Approval indi-
cated that sufficient QA activities were planned for the project to determine and document data
quality. QA project plans were developed for most FRP projects; the exceptions were those
funded at the beginning of the FRP, before the QA program was fully implemented.
An annual on-site technical system audit (TSA) was required for each project. The TSAs
involved a comprehensive review of the QA activities of the whole project as described in the
project plan. In addition, annual air monitor performance evaluations were implemented in
projects conducting controlled exposures or collecting ambient air quality data. Air monitors
were evaluated by calibrating project equipment with audit equipment used as a standard to
assess accuracy in comparison with a certified reference gas.
The QA staff conducted 34, 48, 38, and 45 system audits for 1986, 1987, 1988, and 1989,
respectively. Air monitors at 13, 21, and 23 sites were audited for 1987, 1988, and 1989,
respectively. Following each audit, a report highlighting audit findings and recommended
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corrective action was written. These reports were confidential and were distributed only to
project personnel and the QA staff. Most recommended corrective actions were technical and
were reconciled between the project personnel and the QA staff, with a follow-up by the QA
staff. Occasionally, audit findings revealed management issues, such as changes in project
research direction or questions regarding cooperator interactions and funding. These issues were
referred to the respective cooperative manager for resolution.
The third activity, comparability studies, included promoting the use of similar measurement
methods and equipment, and documenting differences among methods, laboratories, and field
crews. For example, the FRP QA project funded the development of three methods manuals
(Evans and Dougherty, 1986; Robarge and Fernandez, 1987; Zedaker and Nicholas 1988). These
manuals contained recommended methods and were distributed for use in FRP-funded projects.
Furthermore, the QA project funded 12 research initiatives on methods comparability, and
managed four FRP-wide interlaboratory sample exchange programs. In 1988, there were respec-
tively 9,31, and 24 FRP projects participating in the soil, water, and foliage sample exchanges.
Finally, the QA staff helped coordinate and evaluate group training sessions for several field
survey projects.
The final activity, documentation, focused on promoting thorough record-keeping within projects
in order to document QA activities and assessment of data quality. Other activities included
maintenance of QA project plans and audit reports, collection of project QC results, and
formation of a database of project summaries and QC data.
7.13 Quality Assurance Findings
Data quality assessments revealed several common problems:
1. QA project plans were not fully implemented, especially documentation of procedures
and collection and use of QC data.
2. Air monitors were not calibrated within acceptable limits.
3. Application of controlled pollutant treatments within and among exposure technologies
could be an important source of experimental error (Peterson et al., 1989).
4. Some chemical elements in foliage and soil reference samples varied notably among
laboratories.
5. Bias existed in analytical results due to the method by which experimental material was
either sampled or measured.
The significance of these findings varies depending on the particulars of the project and how the
data were used. For example, the significance of an air monitor miscalibration depended
primarily upon when it was discovered. Fewer data were compromised the earlier the detection
within an exposure treatment or season. Thus, equipment audits were scheduled and conducted
as early as possible for each project. Differences among laboratories or measurement methods
can be an important consideration, gjven the goal of summarizing data across several projects.
For several reasons, no studies were excluded from this document because of QA findings. First,
the purpose of the QA program was to improve data quality by detecting problems early and
preventing their repetition. This process also allowed questionable data to be identified, but this
was not the primary goal of the improvement process. Second, the QA program focused on the
measurement process. Failure to meet a data quality objective or rccognlzation of method bias
raised concerns, but it was not sufficient cause for completely dismissing project data and results.
Numerous other factors must be considered before the quality of a project can be fully evaluated,
such as sampling design, statistical analysis, selection of treatment levels, and the nature of the
experimental material. The QA information was thus properly used in conjunction with other
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project information during the evaluation and interpretation phases. Third, some QA guidelines
are qualitative, and they may thus be interpreted in different ways. For example, lack of
documentation of project procedures or remeasurement data does not necessarily indicate that
work was poorly done, although it does mean that evidence of good work is lacking. Furthermore,
the level of documentation that will satisfy a data user may vary. Lack of documentation may add
uncertainties, but it alone is not cause for rejecting project data or results.
These findings illustrate situations in which projects did not meet QA guidelines. More detailed
QA reports are in preparation. Results that are indictative of the accomplishments of the QA
program include: 1) increased documentation of projects; 2) increased use of standardized
methods and better appreciation of the need to have comparable data; 3) improvement in data
quality due to audits and introduction of QA concepts; and 4) increased ability to quantify
estimates of data quality.
7.1.4 Quality Assurance of Branch Exposure Chambers
An overall goal of the FRP is to assess the effects of atmospheric deposition on forest stands.
Much of this work has used controlled exposures of seedlings, as discussed in MPO #3. The QA
findings for open-top chambers (OTCs), continuously-stirred tank reactors (CSTRs), and growth
chambers used in the seedling research are discussed in detail in MPO #3. Branch exposure
chambers (BECs) have been proposed as one method for assessing the effects of air pollution
upon mature trees. In this section, we review QA findings for branch exposure chambers.
The BECs are a relatively new technology, and they present both conceptual and operational
difficulties that must be overcome before results are considered reliable. Data reliability of BECs
depends in part on how well ambient environment is maintained and pollutant treatments are
controlled. Peterson et al. (1989) have shown that variation in the application of pollutant
treatments in OTCs, CSTRs, and growth chambers may be an important source of experimental
error in plant effects studies. They reported that some FPR Q A guidelines for exposure research
were difficult to meet consistently. Consequently, a similar analysis of BECs was undertaken for
this document.
On the basis of three projects, BECs appear to be reliable. Although results are preliminary and
do not cover all aspects of BEC use, they do represent two to three years of work per project on
the development, testing, and use of BECs under lab and field conditions. For example, BECs
appear to meet or exceed FRP guidelines for maintenance of the ambient environment. Data
from Wiselogel [SC18-3] in Figure Al show that chamber temperature was within 3°C of ambient
temperature outside the chamber, which is the FRP guideline (Evans and Dougherty, 1986). In
addition, other data from Wiselogel (SC18-3) showed that hourly chamber temperatures varied
less than 1°C among chambers on the same tree. Similarly, Vann et al. (SF34-2) found that mean
air temperature was 1.1 to 2.4°C greater in chambers compared with open branches on the same
tree during a 20-day period in late summer, 1988. Chamber temperatures showed consistency
among trees; within any given treatment, mean chamber temperatures varied less than 2°C across
trees.
Figure A2 shows that chamber light intensity is within 10% of ambient, which meets the FRP
recommended guideline and easily exceeds the FRP control limit of 25% less than ambient (Evans
and Dougherty, 1986). These differences from ambient were found in full sunlight and are due
to light absorption of the Teflon skin. Wiselogel [SC18-3] has shown that the skin reduced light
transmission up to 200//mol/m2/s; therefore, chamber light intensity would be within al least 25%
of ambient during midday throughout the growing season.
The BECs are capable of meeting or exceeding FRP guidelines for control of pollutant concentra-
tions. Figure A3 shows that O3 concentrations can be delivered within 10% of target, which meets
the FRP control limit (Evans and Dougherty, 1986). Houpis (WC20-1) found no significant O3
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Figure A2. Example of diurnal trend in O3 concentrations (actual/target) for two treat-
ment chambers on the same loblolly pine tree in relation to FRP control limits
(adapted from Wiselogel, SC18-3).
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target
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Figure A3. Example of diurnal trend in light intensity in relation to ambient (target) and
FRP control limits (adapted from Houpis and Cowles, WC2G-1).
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gradients within BECs (mean maximum difference among test points was 6 ppb). In addition,
O3 concentrations surrounding and inside a branch canopy differed by only 4 ppb. Finally, the
scrubbing efficiency of the BEC charcoal filter system increased with test O3 concentrations and
varied from 79% to 88%.
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72 Appendix B: Methods and Materials
7.2.1 Forest Condition Surveys
Research conducted to investigate the two scientific questions addressed in MPO #1&2 used an
epidemiological approach, characterized by broad surveys of forest condition and a search for
patterns that may be related to natural factors or atmospheric deposition. The techniques used
in these studies are discussed in this section. The techniques and limitations of all survey methods
are discussed in more detail in MPO #1&2.
Dendrochronological Analysis
Tree core samples are taken from the population of interest The obtained tree rings are
measured and crossdated (Fritts, 1976). Ring widths are then modeled to determine how
environmental factors, both natural and anthropogenic, affected tree ring growth. Endogenous
disturbances (those affecting a single tree or a subset of trees in a stand) and exogenous
disturbances (those affecting radial growth across stands) must each be considered. To assess
the effects of pollutants, the pollution signal must be separated from all other factors, linear
aggregate and multiplicative models have been used.
Transect Surveys
Transects of varying lengths were used to sample tree vigor class at a number of mountain sites.
Transects were run at different elevations so that elevational differences in forest conditions could
be quantified. In sampling, the tree nearest to the transect line that exceeds a lower size class
limit is sampled. In studies cited in this document, crown classification and live/dead status were
the measures recorded for each sample tree/transect Transects or sample trees are not identi-
cally remeasured over time, as initial transects are not usually permanently marked. However,
the same forest stands are represented.
Permanent Study Remeasurement Data
Permanent plots are used because the sampling error associated with remeasurement and growth
and change estimates is likely to be lower than the error associated with independent samples
(Avery and Burkhart, 1983). They are chosen using two criteria: 1) plots must be representative
of the forest population for which inferences will be made; and 2) plots must be subject to the
same management practices as the unsampled portion of the forest. To determine forest
condition over time, plots of a fixed area were also used, with the number and size of plots required
a function of the size and variability of the population, required sampling precision, and cost
(Husch et aL, 1972). Data obtained from plots typically includes both plot and individual tree
measures. Examples of plot data are location, cover type, stand size and condition, stand age,
stocking, slope, soil classification, and understory vegetation. Individual tree measures include
species, diameter at breast height (dbh), height, crown class, vigor, diameter growth, and
mortality. Because a long intermeasurement period can mask important changes in the rate of
growth, long remeasurement periods should be avoided.
Forest Inventory and Analysis (FIA) Data
The Forest Inventory and Analysis (FIA) Research Work Unit of the Southeastern Forest
Experiment Station inventories the forests of Florida, Georgia, North Carolina, South Carolina,
and Virginia (Sheffield et al., 1985). FIA data from Pennsylvania, Minnesota, Wisconsin,
Michigan, and Vermont are also collected, and are presented in this document. FIA inventories
across the United States are conducted approximately every 10 years to measure changes in the
population. In the Southeast, the first inventory was initiated in 1933, and the fifth was completed
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in 1985. There are approximately 25,000 permanent FIA plots in this region, each representing
an average of 3,400 acres.
In the Southeast, inventory methods and sampling techniques have changed over the years, which
has to be taken into account when interpreting survey results. For FLA remeasurement data used
in the FRP, the point sampling method, generally referred to as selection with probability
proportional to size, is used. The trees are selected by the basal area factor (BAF), the
cross-sectional area (ft2/acre) that a tree represents. As the BAF increases, the probability of a
tree being selected decreases. The BAF system provides for rapid and unbiased estimates of
stand conditions at a given point in time. In subsequent surveys, the live trees identified by the
BAF in the previous survey are remeasured to calculate diameter growth.
To analyze individual-tree growth from the Southeast FLA data, average annual radial increment
(AARI) is calculated for each tree and then a mean AARI is calculated for each diameter class
and species. Even though the same trees are remeasured, some trees die or are cut, new trees
are included, and most trees grow into larger diameter classes. Comparison of mean AARIs for
successive time periods thus indicates how trees of the same diameter class grew in each period,
not how growth of the same trees might have changed.
The nonindustrial lands of the Southeast surveyed by FIA are not usually as intensively managed
as are private lands, and trees of all crown classes are included. High percentages of intermediate
and overtopped trees in the smaller diameter classes suppress growth values. Thus, growth curves
are not typical of those derived for intensively managed stands. The changes in FIA inventory
design over the years make comparisons of individual-tree growth rates difficult. Individual tree
growth data from the earlier surveys are limited; thus, reports of growth reductions are based on
comparisons of average growth rates from the fourth and fifth survey periods only. Additional
difficulties arise in determining possible causes of tree decline because some important tree,
stand, and site information is not available for all plots. Missing information can include crown
position, crown ratio, competing basal area of trees and shrubs, site quality and prior land use.
However, some of these measures can be added to the sampling procedure.
Spatial Study Data
Spatial studies are conducted along known deposition gradients spanning large geographical
areas. Fixed plots are sampled at sites along the gradient to identify patterns in forest response
to natural factors and pollutants; in particular, the responses at either end of the gradient are
compared to determine the magnitude of change. To minimize variation in response due to
differences in stand characteristics, plots are selected to have similar stand characteristics.
Responses measured along the gradient include tree growth, tree mortality, crown vigor, and
precipitation, throughfall, soil, and litterfall chemistry. Spatial studies have been conducted along
gradients in the Great Lakes region (Minnesota to Michigan), in the Ohio Valley (Arkansas to
Ohio), and in Pennsylvania.
Aerial Photography and GIS
Maps, in conjunction with software designed to analyze large data bases of geographic informa-
tion, have been used in a few instances to evaluate forest condition for a large geographic area,
such as estimated standing dead. In one study, existing type maps for the area were used to
identify stands of known species. The applicable maps were then transferred to aeronautical
section charts, flight lines were plotted, and aerial color infrared photographs were taken in stereo
at a scale that allowed individual trees to be studied under magnification. Next, photo interpreters
classified by mortality the area wiuiin each of six previously defined geographic regions and
determined the stand boundaries. Mortality classes were then randomly sampled in proportion
to the area of tree species affected, A random ground sample of the selected aerial plots was also
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performed, providing data on species, dbh, crown condition, total height, and crown position for
each sampled tree, as well as site information. The GIS software was used to construct the
database.
722 Atmospheric Deposition Data
Wet Deposition Data
While some researchers have used survey data to evaluate forest growth and condition, other
research has been conducted to assess trends across the Unite States in atmospheric deposition
of pollutants and exposure to ozone. These data and the methods used to obtain the data are are
presented in MPO#l&2. In that report, annual summaries of precipitation chemistry from the
National Atmospheric Deposition Program (NADP/NTN) are used to describe spatial (horizon-
tal) variation in wet deposition (NADP, 1988; Olsen and Slavich, 1986). Cloud water chemistry
data from the Mountain Cloud Chemistry Project (MCCP) also are presented to describe
elevational (vertical) variation (Mohnen, 1988a,b; Vong, 1990).
Elevational variation in deposition is primarily related to the amount of time a forest is immersed
in clouds. In the East, at elevations below about 1000 m, wet deposition is primarily due to
precipitation, while above 1000 m cloud water chemical deposition may equal or exceed precipita-
tion deposition. Cloud frequencies and chemical flux contributions from cloud water have not
yet been quantified for the West.
Either wet deposition or concentrations of H+, SO42", NOs", and NH4* may be relevant to
describe acidic precipitation, depending on the ecological effect of interest. For example, foliar
leaching in spruce needles might be related to chemical concentrations in acidic precipitation,
whereas soil buffering processes might reflect wet deposition. Because observed precipitation
concentrations of H + (NADP, 1988) are consistently lower than those found to harm seedlings
(Peterson et al., 1989), precipitation deposition, not concentration, is considered relevant to
forest effects. However, because of the much higher chemical concentrations (lower pH) in cloud
water, both cloud water chemical concentrations and deposition are considered relevant to forest
effects.
Regional estimates such as isopleth maps typically are used to show the magnitude and extent of
acidic deposition and to locate areas of high or low deposition. Spatial interpolation is necessary
to generate contour maps of wet deposition and to estimate data for non-monitored locations.
Recognizing that there are numerous equally valid methods for presenting these data, a regional
map with bars was used because it best demonstrates annual deposition, its variability, and
gradients over regional scales (< 100 km). Contour maps require interpolation assumptions and
can mask some small-scale variability, but they are also very useful for displaying large-scale
spatial trends (over areas greater than 100 km; Vong ct aL, 1989; Olsen, 1989). To produce
summaries, multiannual averages from only NADP/NTN sites were specified to ensure data
comparability and reduce temporal variability. Contour maps for individual years are available
elsewhere (summarized by Vong et aL, 1989).
Ozone Data
Ozone is the only regionally dispersed pollutant known to injure foliage and cause tree mortality
(Woodman, 1987). Ozone injury to coniferous forest species is well documented (e.g., Miller et
aL, 1963; Miller, 1973,1984; Peterson et aL, 1987; Peterson and Arbaugh, 1987; Temple, 1988).
Regional and national trends in O3 exposure are reported in MPO#l&2. However, because O3
levels are not known for the forested sites in FRP studies, formal correlations of O3 levels and
forest growth and conditions were not possible in either MPO#l&2 or this report.
99
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MPO#4
FRP FOREST EFFECTS REPORT
MATTSON ETAL
Several indices of O3 exposure have been used, such as simple 24-hour means and cumulative or
weighted sums. When relating growth trends to pollutant exposure across large spatial areas,
these indices may not reflect subtle differences in O3 exposure (and consequently response) at
different places. Because the "physiologically effective" dose for O3 is the integrated flux into
leaves via the stomata, the correspondence between diurnal patterns of stomatal conductance
and O3 concentration determines the effective dose (Guderian, 1985; Krupa and Teng, 1982;
Tingey and Taylor, 1982). Thus, differences in diurnal O3 patterns may produce different
physiological responses, and therefore an index that incorporates both the temporal aspect and
the magnitude of O3 concentration is desirable.
Since the formation of O3 is related to meteorology, which can vary considerably from year to
year, the median can be influenced by the sampling period. To reduce the likelihood of such
influence, periods longer than three years were usually used for averaging. Worst-case scenarios
can also be influenced by sampling period, but at worst they will underestimate extreme condi-
tions. Seasonal and diurnal patterns in 03med and 03worst do not reflect actual patterns, but are
rather 50th percentile and 99th percentile surfaces.
723 Controlled Exposure Studies
Research conducted to investigate Scientific Questions 2.2, 23, and 2.4 uses an ecological
approach, characterized by controlled exposures of seedlings in chambers to simulated acidic
deposition and gaseous pollutants. Results from seedling studies, such as visible or latent seedling
response, are the major source of information currently available to address the scientific
questions. The term seedling refers to trees small enough (e.g., height generally less than 1 m)
to be housed in standard open-top chambers. The techniques and limitations of these methods
are discussed in detail in MPO #3. Thus, only a brief summary of the technique is given here.
General Methods
To quantify responses to simulated acid deposition, SO2, and O3,12 conifer species, 12 hardwood
species, and 100 commercially important families of loblolly pine were tested. Most studies used
seedlings, but studies performed with branch exposure chambers used mature trees. This section
describes the general methods used. Methods varied among studies and may have affected the
particular results observed. A more complete overview of the experimental approaches used in
individual research projects by the four research cooperatives is given in MPO #3.
Experimental Material
Seedlings were grown from germinated seeds obtained from known seed sources. These sources
were: 1) specific regions of forest occurrence for spruce fir; 2) tree nurseries for the eastern
hardwoods; 3) commercial and research seed orchards of loblolly pine; and 4) regions of forest
occurrence and forest-tree nurseries for western conifers. Most seedlings were planted in
individual containers. Rooting media were typically composed of commercial mixtures (e.g.,
peat, vermiculite, perlite), although soil representing a forested site was sometimes used. Ages
of seedlings at time of treatments ranged from 12 weeks to 4 years; the majority were 2 years or
younger at the beginning of the studies.
Exposure Facility
To apply treatments to seedlings, chambers were used that provided for delivery of simulated
acid deposition and that allowed some modification of the air space around the seedlings. Two
types of chambers were generally used, and choice of chamber type involved a trade-off between
experimental control and replication of realistic conditions. Completely enclosed chambers,
referred to as continuously-stii red tank reactors (CSTRs) in greenhouses or laboratories allowed
for higher precision in tbc application of gaseous treatments. Most exposure facilities were
100
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MPO#4 FRP FOREST EFFECTS REPORT MATTSON ETAL
open-top chambers (OTCs), located outdoors where some exclusion of ambient air, but exposure
to sunlight, humidity, and normal air temperatures, was desired. The outdoor chambers may or
may not have had rainfall exclusion devices, depending upon experimental objectives.
Branch Exposure Chambers
Branch exposure chambers were used to assess the effects of air pollution on large, mature trees.
These chambers enclose tree branches for the purpose of controlling pollutant exposure by
filtering ambient pollutants and/or by delivering known levels of pollutants; Modification of the
ambient environment within chambers is common; in particular, temperature,flight, and air
humidity are controlled. Branch exposure chambers incorporate features such as fans to promote
air exchange, materials that allow light penetration but do not hold heat, and humidifiers. In
addition to being influenced by these technical concerns, the reliability of results from branch
chamber studies is also influenced by conceptual issues such as branch autonomy, sampling
design, and integration with root processes.
Treatments
The most prevalent treatments included simulated acid precipitation and O3 applied alone or in
combination. One to six levels of acidity were used, ranging from pH 2.1 to 5.6. Simulated acid
precipitation typically consisted of a chemical composition that reflected rainfall chemistry of the
study area (S:N typically 2:1). In MPO #3, terms'such as'acidity, acid, or acid deposition refer
to H+ concentration plus the chemical composition of the simulated precipitation.
One to six levels of O3 concentration were used, ranging from 0 to 320 ppb. Charcoal filtering
can remove up to 100% of O3 in ambient air. Therefore, CSTRs can attain 0 ppb treatments while
OTCs never quite approach 0 ppb due to mixing of filtered air and ambient air through the open
tops. Concentrations of O3 in OTCs that receive charcoal-filtered air are typically 30% to 50%
of ambient concentrations. In addition to acidity and O3, one project varied the ratio of S to N
in the precipitation, while others applied treatments of SO2. Finally, several studies tested for
interactions of acid precipitation and/or O3 with winter injury or interactions with water stress.
Treatments Ayere applied to the seedlings during periods of active aboveground growth over
intervals vatying from 10 weeks to 7 months. Multiple-year exposures are also being carried out.
Simulated deposition was applied as rain, mist, or fog, usually to both foliage and rooting medium
in a pattern reflecting historical trends for a specific region. In some cases, deposition was applied
only to saturate the foliage; in such cases, the rooting medium received controlled watering.
Ozone was applied over regulated time intervals, usually during daylight hours. Applications
varied among studies, but were of two general types. One type was a square-wave regime where
a constant concentration of O3 was applied over a definite time interval during the day. In more
sophisticated designs, O3 applications followed the monitored ambient concentrations for the
region, where 63 concentrations typically increased to a mid-afternoon peak then decreased until
dusk.
Response Variables .
Response variables' measured are either effects or mechanisms. Effects represent a change in
seedling condition and include visible injury or growth changes. Mechanisms are the processes
by which effects are manifested. The mechanisms examined include carbon allocation, winter
injury, and foliar leaching, reflecting Scientific Questions 12,23, and 2.4. Carbon allocation is
used as a general term that includes growth, morphology, and general physiology, including
photosynthesis and respiration.
The actual response variables measured in some studies were quite numerous. Some variables
were measured several times during the treatments, while others were measured only at the
101
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MPO#<
FRP FOREST EFFECTS REPORT
MATTSONETAL
termination of treatments. Visible effects included foliage discoloration (chlorosis, necrosis),
foliage loss (senescence), or whole-tree subjective classification. Growth effects involved some
measure of seedling biomass (linear measures of branches or roots, diameter of stem, or mass of
various components). Carbon allocation involved measures of photosynthetic rates, respiration
rates, tissue damage assessed microscopically, or tissue chemistry (sugars, starch and nonstruc-
tural carbohydrates, photosynthetic pigments, or enzymes). Winter injury was examined as an
interacting stress; in these cases, seedling responses were measured after treated seedlings were
allowed to over-winter at ambient temperatures or after tissues were exposed to simulated frosts.
Foliar leaching involved some measure of solution chemistry of throughfall or of solutions in which
treated tissues were leached.
Statistical Methods
All seedling studies were designed to test hypotheses statistically. Building on exposure studies
of crops in the National Crop Loss Assessment Network (NCLAN), the experimental designs
were generally a variation of split-plot or randomized blocks. Most studies were designed for
repeated measures (usually five or more intervals) of total plant height and root collar diameter.
Data were analyzed via analysis of variance, analysis of covariance, or regression techniques.
Important statistical issues identified for the seedling exposure experiments are design and
analysis, relevance, combining results across experiments, and statistical power. These issues are
covered in MPO #3 and elsewhere (Peterson, 1989).
102
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MPO*4
FRP FOREST EFFECTS REPORT
M/UTSON ETAL
7J Appendix C: Abbreviations
AARI
average annual radial increment
AIRS
Aerometric Information Retrieval System
ALBIOS
Aluminum in the Biosphere
A
ambient
BAF
basal area factor
BEC
Branch exposure chamber
CF
charcoal-filtered
CSTR
Continuously-stirred tank reactor
dbh
diameter at breast height
DDRP
Direct/Delayed Response Program
EH
Eastern Hardwoods
EPA
Environmental Protection Agency
EPRI
Electric Power Research Institute
FIA
Forest Inventory and Analysis
FRP
Forest Response Program
IFS
Integrated Forest Study
MCCP
Mountain Cloud Chemistry Program
MPO
Major Program Output
NADP/NTN
National Atmospheric Deposition ProgratWNational Trends Network
NAPAP
National Acid Precipitation Assessment.Program
NCASI
National Council of the Paper Industry for Air and Stream Improvement, Inc.
NCLAN
National Crop Loss Assessment-Network
NEDS
National Emissions Data System
GTC
Open-top chamber
QAPP
Quality Assurance Project Plan
QA
Quality Assurance
QC
Quality Control
ROPIS
Response of Plants to.Interactive Stress
S&I
Synthesis and Integration
sc
Southern Commercial
SF
Spruce-Fir
TSA
Technical system autdit
TV A
Tennessee Valley Authority
USDA
United States Department of Agriculture
USPS
USDA Forest Service
VS
Vegetation Survey
WC
Western Conifers
WMP
Watershed Manipulation Project
103
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MPO#4
FRP FOREST EFFECTS REPORT
MATTSON ETAL
7.4 Appendix D: Scientiflc Names of Trees
American beech
Fagus grandifolia Ehrhart
Balsam fir
Abies balsamea (Linnaeus) Miller
Black cherry
Prunus serotina Ehrhart
Black spruce
Picea mariana (Mill.) B.S.P.
Douglas-fir
Pseudotsuga menziesii (Mirbel) Franco
Engelmann spruce
Picea engelmanni Parry
European beech
Fagus sylvatica Linnaeus
Fraser fir
Abies fraseri (Pursh) Poiret
Honey locust
Gleditsia triacanthos Linnaeus
Jeffrey pine
Pinus jeffreyi Greville and Balfour
Loblolly pine
Pin us taeda Linnaeus
Lodgepole pine
Pinus contorta Loudon
Norway spruce
Picea abies (Linnaeus) Karaten
Ponderosa pine
Pinus ponderosa Douglas
Red maple
Acer rubrum Linnaeus
Red oak
Quercus rubra Linnaeus
Red Spruce
Picea rubens Sargent
Shagbark hickory
Carya ovata (Miller) K. Koch
Shortleaf pine
Pinus echinata Miller
Slash pine
Pinus elliottii Engelm. var.elliotii
Subalpine fir
Abies lasiocarpa (Hooker) Nuttall
Sugar maple
Acer saccharum Marsh
Sweetgum
Liquidambar styraciflua Linnaeus
Trembling aspen
Populus tremuloides Michaux
Western hemlock
Tsuga heterophylla (Rafmesque) Sargent
western red cedar
Thuja plicata Donn
White ash
Fraxinus americana Linnaeus
White fir
Abies concolor (Gordon & Glendinning) Lindley
White oak
Quercus alba Linnaeus
Yellow birch
Betula alleghaniensis Britton
Yellow-poplar
Liriodendron tulipifera Linnaeus
104
-------
TOP FOREST EFFECTS REPORT
7.5 Appendix E: Summaiy Tables of FRP Research
MATRON ETAL
105
-------
Tabie 4. Seedling responses to controlled exposures of pollutants (see legend at end of table).
Southern pines
SOURCE
SPECIES
TREATMENT1
RESPONSE2
Foliage
Stem
Root
Ps
Other
Dura-
tion
O3 ppb
range
(# levels)
pH
range ;
(# levels)
cond.
mass
mass
ht.
dia.
O3
pH
O3
pH
O3
PH
03
pH
O3
pH
O3
pH
O3
pH
McLaughlin
et al.
SC04-1
(Jab)
(field)
loblolly
pine
12
wks
0-320
(3)
0
0
+
0
-
-
0 foliar nutrients
loblolly
pine
12
wks
CF-A+160
A-38
(5)
3.3 - 5.2
(3)
0
0
0
0
*
-0 +
+
0
0
-
0
-
+
O3: - foliar nutrients
- mycorrhizal infection
- C allocation to roots
pH: + foliar Al
0 stomatal conductance due to O3
Reinert et al.
SC05-5
(lab)
loblolly
pine
13
wks
0-320
(5)
-
-
-
-
Reinert et al.
SCC5-I
(lab)
loblolly
pine
13
wks
0-320
(5)
3.3 - 5.3
(3)
-
0
-
0
-
0
-
0
-
0
O3: t foliar N (greatest at
160 ppb)
4 foliar starch
Kress et al.
SC06-3
(field)
loblolly
pine
8 mo/jT
2yrs
CF-3A
A-48
(5)
3.5 - 5.2
(2)
-
0
-
0
-
0
-
0
-
+
-
enhanced growth at 1.5 x ambient
O3 vs ambient concentrations
Richardson
& Sasek
SC07-6
(field)
loblolly
pine
8mo/yr
2yrs
CF-3A
A =48
(5)
3.5 - 5.2
(2)
-
0
Same seedlings used by Kress et al.
SC06-3
Reardon
et al.
SC12-1
(field)
shortleaf
pine
12
mo
CF - 2.5A
A-?
(4)
3.3 - 5.3
(3)
-
-
0
0
O3: + needle glucose
- needle starch
+ needle protein
Flagler
SC14
pers. comm.
(field)
shortleaf
pine
16
mo
CF-2.5A
A -403
(4)
3.3 - 5.3
(3)
-
0
-
0
-
0
-
0
-
0
-
+
O3: -chlorophyll content
• needle area
pH: 0 chlorophyll content
0 needle area
continued
-------
1 UI/IV 4j CuilbllJU6«i yw-36 ivgvud 21* vt
-------
Table 4, continued, (see legend at end of table)
Y/eslsrn conifers
TREATMENT1
RESPONSE2
SOURCE
SPECIES
Foliage
Stem
Root
Ps
Dura-
O3 ppb
range
(# levels)
pH
range
(# levels)
cond.
mass
mass
ht.
dia.
Other
tion
O3
PH
O3
pH
O3
pH
03
pH
O3
pH
O3
pH
O3
PH
Hogsett &
Tingey
WC08-1
Douglas-
fir
4,2
mo/yr
2yrs
2.1 - 5.6
0
0
+
4-
+
-
Duration of exposure are 4 mo. of
O3 in summer followed by 2 mo.
(fieid)
see also:
pond-
erosa
pine
(3)
0
0
0
+
0
0
of acid fog in the winter
Measurements are taken during
growth season following
exposure
Hogsett et al.
WC38-2
Douglas-
fir
CF-71(220]
2.1 - 5.6
0
0
-
-
0
0
0
0
0
0
0
0
pond-
erosa
pine
4,2
mo/yr
2yrs
ave(peak)
(3)
(3)
-
0
-
0
-
0
-
0
-
0
-
0
Second-year observations generally
agree with first year except
lodgepole pine showed reduced
western
hemlock
-
-
-
0
-
0
-
0
0
0
-
0
root and foliage mass due to O3
western
red
cedar
0
-
-
+
0
+
+
0
0
0
0
-
Ponderosa pine & western hemlock
most sensitive to O3
lodge-
pole
pine
-
0
0
0
0
0
0
0
0
0
0
0
Western red cedar least sensitive to
O3
continued
-------
Table 4, continued, (see legend at end of table)
Western conifers
TREATMENT1
RESPONSE2
SOURCE
SPECIES
Foliage
Stem
Root
Ps
Dura-
O3 ppb
range
(# levels)
PH
range
(# levels)
cond.
mass
mass
ht.
dia.
Other
tion
O3
pH
O3
pH
O3
pH
O3
pH
O3
pH
O3
pH
O3
pH
Miller et al.
WC09-1.3
1988
white fir
-
-
-
0
0
0
+
+
0
0
0
•
Exposures are similiar to Hogsett
results
(field)
nibatpine
fir
Engelmann
spruce
3,2
mo/yr
2yrs
CF - 71(220]
(4)
2.1 - 5.6
(3)
-
-
-
•
0
-
0
+
0
0
0
-
and Tingey WC08-1
Considerable variability in seedling
response between 1988 and 1989
exposures.
0
0
+
+
+
+
0
0
0
+
+
0
ponderosa
pine
*
-
+
-
0
0
-
-
+
-
-
Douglas-
fir
0
•
0
+
-
+
+
+
0
+
-
-
1989
results
(new
seedlings)
(field)
white fir
-
+
+
+
-
+
+
0
+
+
0
xubatplne
fir
Engelmann
(pruce
-
+
-
+
0
0
+
+
0
0
-
0
-
0
0
0
-
-
-
-
0
+
ponderosa
pine
-
0
0
0
0
+
+
+
+
0
0
i
i
I
Douglas-
fir
-
0
'
+'
-
-
0
+
-
0
-
continued
-------
Table 4, continued, (see legend at end of table)
Western conifers
SOURCE
SPECIES
TREATMENT1
RESPONSE2
Foliage
Stem
Root
Ps
Other
Dura-
tion
O3 ppb
range
(# levels)
pH ,
range
(# levels)
cond.
mass
mass
ht.
dia.
O3
pH
O3
pH
O3
PH
O3
pH
O3
pH
O3
pH
O3
pH
Turner et al.
WC07-1
(field)
Douglas-
fir
pond-
erosa
pine
western
hemlock
western
red
cedar
2 mo
2.1 - 5.6
(3)
0
0
0
Growth responses are derived
from Hogsett & Tinge/s (WC08-1)
seedlings
- root-to-shoot ratio
Douglas-fir tested for foliar leaching
in a lab study.
+ foliar leaching of K, Ca, Mg
0 foliar content of K, Ca, Mg
0
0
0
-
0
-
-
+
0
continued
-------
Tauiv ~Tj Cijiiiiii JCC. yt»vC L&_J 2ll of ww.vj
Eastern spruce and fir
SOURCE
SPECIES
TREATMENT1
RESPONSE2
Foliage
Stem
Root
Ps
Other
Dura-
tion
03ppb
range
(# levels)
pH
range
(# levels)
cond.
mass
mass
ht.
dia.
o3
PH
o3
pH
Oa
PH
o3
pH
O3
pH
O3
pH
O3
pH
Jacobson
etaL
SF06-1.2
(lab+field)
red
spruce
6-19
wks
2.5-4.5
(3)
w
S04
-
+
0
w
N03
- foliar K, Ca, Mg
+ foliar N W/NO3 at low pH
+ foliar S w/ SO4 at low pH
t foliar injury w/ low N to roots
Patton
et al.
SF07-2
(lab)
red
spruce
6
mo
CF-150
(3)
3.5 - 4.5
(3)
0
0
0
0
0
0
0
0
0
0
0
current-yr needles:
O3: + carbohydrates, P
- Cu
pH: + Ca
Patton
et al.
SF07-1
dab)
red
spruce
6
mo
50-150
(3)
3.0-4.2
(2)
0
-
-
+
•
-
O3: + thrufall Mg, Mo, B, and
Na
pH: * W/H2O freq.
+ thrufall Fe, Mn
- thrufall B, Mg, Na
Seiler &
Chevone
SF13-4
(lab)
Fraser
Br
10
wks
<20-100
(3)
0 needlewater potential,
osmotic potential, and
turgor potential
Seiler et al.
SF13-1
(lab)
Fraser
fir
10
wks
3.0-5.6
(3)
.t
0
0
? needle conductance and
transpiration
Tseng etal.
SF13-2
Gab)
Fraser
fir
10
wks
<20-100
(3)
0
0
0
-
continued
-------
Table 4, continued, (see legend at end of table)
Eastern spruce and fir
SOURCE
SPECIES
TREATMENT1
RESPONSE2
Foliage
Stem
Root
Ps
Other
Dura-
tion
O3 ppb
range
(# levels)
pH ¦
range
(# levels)
cond.
mass
mass
ht.
dia.
O3
pH
03
PH
O3
PH
O3
pH
O3
pH
O3
pH
O3
PH
Cape et al.
SF14-4
(field)
red
spruce
21
wks
2.5 - 5.0
(6)
- frost hardening
Leith et al.
SF14-6
(field)
red
spruce
22
wks
2.5 - 5.0
(6)
-
Neighbour &
Melhorn
SF14-16
(lab)
red
spruce
4 mo/yr
2yrs
CF-CF+70
(4)
- frost hardening
NO removal reduces O3 effect
Chen &
Weliburn
SF14-7
(field)
red &
Norway
spruce
6 mo
(rs)
3 mo
(Ns)
2.5 - 5.0
(6)
-
+ stress ethylene emission rate
Eamus &
Fowler
SF14-9
(field)
red
spruce
6 mo
2.5 - 5.0
(2)
+
+ stomatal conductance due to
acidity
Eamus et al.
SF14-8
(field)
red
spruce
3 mo
2.5 - 5.0
(6)
0 transpiration and cuticular
resistance
- shoot H2O potential, maximum
turgor, ana relative H2O
content
Alscher
et al.
SF16-5
(field)
!
red
spruce
6
mo
CF-2A
A =40
(4)
0
0
0 non-structural carbon in foliage
and roots
0 electron transport rate
0 foliar pigments
delayed production of raffinose
i Cumming
| et a':.
! SF16-2
(field)
red
spruce
16
wks
CF-3A
A =40
+ electron transport rate* and
respiration
- photosynthetic pigments
continued
-------
Table 4, continued, (see legend at end of table)
Eastern spruce and fir
TREATMENT1
RESPONSE2
SOURCE
SPECIES
Foliage
Stem
Root
Ps
Dura-
O3 ppb
range
(# levels)
pH
ranee
(# levels)
cond.
mass
mass
ht.
dia.
Other
tion
O3
PH
O3
PH
O3
pH
O3
PH
03
pH
03
pH
O3
pH
Fincher et aL
SF16-4
red
spruce
7
mo
CF-3A
A-40
(4)
• mesophyll cell condition following
frosts
- photosynthetic pigments
Laurence
et al.
SF31-2
(field)
red
spruce
3
mo
0.5A-2A
A=38
(4)
3.1 - 5.1
(3)
0
0
+ ~
0
0
0
+ t
0
.t
0
+ & - responses were not
statistically significant (see text)
Kohut et al.
SF31-1
(field)
red
spruce
4
mo
0.5A-2A
A "38
(4)
3.1 - 5.1
(3)
0
0
0
0
0
+
Second year of exposures of
seedlings used by Laurence et
aL SF31-2
Thornton
et al.
SF27-3
(field)
red
spruce
13
wks
CF-A
(2)
mist filter
-A
(2)
0
0
0
0
0
0
0
0
0
0
Ambient clouds.on Whitetop Mt.
filtered w/B-GON mist filter
Native seedlings not affected,
commercial seedlings (Phyton)
showed enhanced Ps w/pollutant
exclusion (not statistically
significant)
Deans et al.
SF14-19
red
spruce
22
wks
2.5-5.0
(6)
+ root branching
• partitioning to coarse roots
- mycorrhizal fruiting bodies
continued
-------
Tabie 4, continued, (see legend at end of table)
Easisrn hardwoods
TDC ATMCWt'
RESPONSE2
SOURCE
SPECIES
Foliage
Stem
Root
Ps
Dura-
O3 ppb
range
(# levels)
pH
range
(# levels)
cond.
mass
mass
ht.
dia.
Other
tion
O3
pH
O3
pH
O3
pH
O3
pH
O3
pH
O3
pH
03
pH
Davis &
Skeily
EHOi-1
black
cherry
-
0
-
-
-
-
-
some interaction of pH and O3 on
(lab)
sweetgum
12
wks
0-150
(3)
3.0 - 4.2
(2)
-
0
0
0
foliar injury
yellow-
poplar
-
0
0
0
no consistent demonstrable effect
of pH on growth of any species
other than black cherry
1
white ash
-
0
0
0
yellow
birch
-
0
-
-
red maple
-
0
-
-
white oak
-
0
-
-
red oak
0
0
0
0
continued
-------
Table 4, continued, (see legend at end of table)
Eastern hardwoods
TREATMENT1
RESPONSE2
SOURCE
SPECIES
Foliage
Stem
Root
Ps
Dura*
03ppb
range
(# levels)
pH
range
(# levels)
cond.
mass
mass
ht.
dia.
Other
tion
o3
pH
o3
pH
o3
pH
o3
pH
o3
pH
o3
PH
CH
pH
Jensen &
Dochinger
EH06-1
white ash
-
0
-
-
-
-
(lab)
yellow
birch
16
wks
0-150
(3)
3.0-4.2
(3)
-
0
-
-
-
+
sweetgum
-
0
0
+
0
+
sugar
maple
0
0
-
-
-
-
yellow-
poplar
-
0
0
0
0
0
red maple
-
0
-
+
0
0
white oak
0
0
0
0
0
0
shagbark
hickory
0
0
0
0
0
0
American
beech
0
0
0
0
0
0
European
beech
0
0
0
0
0
0
continued
-------
'i able 4, continued, (see legend at end of table)
Eastern hardwoods
SOURCE
SPECIES
TREATMENT1
RESPONSE2
Foliage
Stem
Root
Ps
Other
Dura-
tion
O3 ppb
range
(# levels)
pH '
range
(# levels)
cond.
mass
mass
ht.
dia.
O3
pH
03
PH
O3
pH
O3
pH
O3
PH
O3
PH
O3
PH
Foster et al.
EH06-2
(lab)
white
oak
18
mo
20
wks/yr
2yrs
0-150
(2)
1st yr;
0-1.15A
(2)
2nd yr
0
0 quantum efficiency
0 carboxylation efficiency
0 respiration
0 stomatal conductance
Karnosky
et al.
EH03-5
(field)
sse also
EH03-1
trembling
aspen
3
mo
CF-80
(3)
-
-
-
-
-
-
LEGEND
1 Treatment symbols:
Abbreviations:
A = ambient concentration
ppb = parts per billion
CF = charcoal filtered
cond = visible condition
2 Symbols represent the seedlings' response relative
to the control or nominal treatment:
0 = no effect
= negative effect or suppression
t = positive effect or enhancement
* = treatment interaction
t = our interpretation(different from author's)
ht. = height
dia. ~ diameter
Ps = photosynthesis
wks. = weeks
SC = Southern Commercial Research Cooperative
WC = Western Conifer Research Cooperative
SF = Spruce-Fir Research Cooperative
EH = Eastern Hardwoods Research Cooperative
Note: blank cells indicate response not measured
-------
Table §. Soil/Nutrient Cycling Studies
SOURCE
STUDY MATERIAL A
SITE CHARACTERISTICS
VARIABLES
OFINTEREST
ASSOCIATED
VARIABLES
RESULTS
Binkley et al.
SC16-1
Soils sampled in 1962 and
1982 in a cotton Held con-
verted to loblolly pine in
1957:
Calhoun Experimental
Forest, SC
Soil:
pH>
extra ctable cations
titratable acidity
titratable alkalinity
Time
Over 20 yea re:
V pH by 0.3 to 0.8 units in all horizons
marginal^. in titretablealkalinity and marked f in titratable acidity
i extractrMeCa,Mg, &k by 20-80%
t exlractable Al by 1040%
Most ration loss probably doe (0 accumulation In biomass; changes In
soil chemistry may be Induced by land-nse changes
David et al.
VS10-7
Soil and forest floor in 5
locations in each of 169
plots across MN, WI, Ml
Soil and forest (loon
C
N
S
SO4 deposition
Relative location
Forest type
C, N, and S concentrations in the forest floors and mineral soil not very dif-
ferent across gradient
Balsam fir stands tad f S in forest floor
S, after adjusting for, N.was 15% greater In forest floors and mineral soli at
east* rn high deposition plots
Fernandez & Lawrence
SP04-1
Nutrient fluxes In spruce-
fir forest;
Howlahd Site, ME
Chemistries:
soil solution
through fall
precipitation
stemflow
Litter
Biomass
Foliage
Precipitation neutralized by contact with foliage
Cations andorganic acids leached from foliage
No evidence of N saturation based cm foliar chemistry
Precipitation chemistry Is modllled by foliage
Grigal & Ohmann
VS10-3
Forest floor at S locations
in each of 171 plots across
MN, WS, MI
Forest floor
P
cations
heavy metals
SO« deposition
Relative location
West to east: I Ca, Mg, K, Na; f Pb, Cd; no change in Cu, Zn;
N1 differences but no pattern
Trends consistent with atmospheric deposition of Ca, Mg, K, Na, and P
from western solMertved sources and deposition of Pb and Cd from
eastern anthropogenic sources
Huntington et al.
SFCS-7
Red spruce stands at vary-
ing elevations and.aspects;
ML Moosilauke, NH
Tree foliage
Crown condition
Soil chemistry
Forest floor chemistry
Cryofolist soils
Spodosol soils
Elevation
Aspect
With t crown vigor f soil P, forest floor exchangeable Mg & Ca
t exchangeable soil Ca with f foliar Ca
Foliar element concentrations not correlated with crown vigor
Red spruce do not appear to be deficient In foliar nutrients with the
possible exception of P
Huntington et al.
SP30-1
i
Soil solution in hydrologi-
cally isolated soil blodcs;
Whitefacc Mtn., NY
Soil Solution Chemistry:
rapidly reactive (RR)
Al
anions
Simulated SO< deposi-
' lion
Precipitation of pH
IS, 4J, 5.1
RR Al t with anion concentration; highest just below forest floor
Unrealistic N mineralization with soil block isolation may influence results
RR Al In soli solutions considerably less than 'harmful' (100/iM/L)
concentration
continued
-------
Table 5. Soil/Nutrient Cycling Studies (continued)
SOURCE
STUDY MATERIAL &
SITE CHARACTERISTICS
VARIABLES
OF INTEREST
ASSOCIATED
VARIABLES
RESULTS
Huntington & Ryan
SFG5-6
Soils sampled on east
aspects at 840,1000, and
1200m;
Mt. Moosilauke, NH
Soil and forest floor
extractable cations
Al
P
Elevation
Soil type
With t elevation:
t occurrence of cryofolists, I spodosots
t soil mass in cryofolists
in spodosols:
forest floor 1 Ca, Mg, K, base saturation, t Al, ?P
mineral soil: 1 Ca, Mg, base saturation, t Al, K, P
in cryofolists:
forest floor j Ca, Mg, P, base saturation, 7 Al, K
mineral soil: 4 Ca, Mg. K, Al, P, base saturation
Trends associated with elevation within soil types
No difference between soils on east vs. west aspect
Johnson ct al.
SP08-4
Soils and 69 red spruce
trees on NW aspect at 700
and 1300 m;
Whiteface Mtn., NY
Foliar chemistry
Crown vigor
Soil chemistry
Elevation
j foliar K with j crown vigor; foliar Ca & Mg not correlated with crown
vigor
Sufficient foliar Ca and K; foliar Mg moderately deficient
No correlation between soil A foliar levels of K, Ca, Mg, or Al
With f elevation: | foliar & soil Mg, soil Ca; f soil K & Al
Relatively low soil cations do not limit foliar content
Johnson ct al.
SF08-14
Forest floor and soil at S6
plots in hardwood-spruce
and fir-spruce zones on all
aspects from 700-1200 m;
Soil:
exchangeable
nutrients
pH
depth
Al
Forest floor pH
Red spruce mortality
No Indication that soli depth, soil pH, forest floor pH, and exchangeable
Cm, Mg, K, and Al are correlated with crown damage
Whiteface Mtn., NY
Joslin et al.
SF27-1
Nutrient fluxes and tree
condition in 2 red spruce
stands at summit that differ
in atmospheric inputs
Whitetop Mtn., VA
Chemistries:
throughfall
stemflow
soil solution
bulk soil
foliage
Foliar injury
Stem elongation
Litterfall
SO< deposition
Goud water deposi-
tion
High-cloud deposition vs. low-cloud deposition site:
solution flux to the forest floor was 15%, 29%, and 45% greater for SO<
NOj, and NH4, rcsp.
| foliar growth, bud mortality, and needle retention
only evidence for f winter damage was slightly f litterfall, probably from
wind and ice
1 foliage concentrations of Mg, Zn, Ca
t foliage concentrations of K and B
soil solution dominated by NO3 and responsible for fluctations in Al conc.
High N deposition may be Inducing toxic Al concentrations In soil
Joslin et al.
SF27-5
1
1
i
l
Cloud-water generated
throughfall from red spruce
saplings at 1700 m summit;
Whitetop Mtn., VA
Throughfall chemistry
Cloud water deposi-
tion
Relative importance of cations shifts as cloud water becomes throughfall:
i H to 2/3, NH< to 1/3 of original contribution
| K, Na, Mg, Ca at least 100%
t Ca by 18-fold and Mg by 25-fold as cloud water pH j from 4.6 to 2.9
Relative importance of major anions (SO4, NOj, CI) remained
relatively constant
Acidic cloud water may contribute to nutrient deficiencies on nutrient-poor
sites
continued
-------
Table 5. Soil/Nutrient Cycling Studies (continued)
SOURCE
STUDY MATERIAL &
SITE CHARACTERISTICS
VARIABLES
OF INTEREST
ASSOCIATED
VARIABLES
RESULTS
Loucks & Somen
EH05-6
Soil in oak-hickory forest; 7
sites; 8 plots/rite; along a
gradient of acid deposition;
ARtoOH
Soil:
f
S
Soil type
Elevation
Aspect
4 soil pH from west to east
High C in At horizon in eastern states
Increasing soils from west to east
High SO* deposition may be Inhibiting soil C decomposition
Ludovici et al.
SC05-8
(co-funded by NCASI)
Soils (clayey,-mixed, ther-
mic aquic Hapludultl in
pots, planted with loblolly
pine seedlings, exposed to
simulated acid rain. 3 ap-
plicationsAvk for 20 wks.
Piedmont, NC
Soil:
^bbase saturation
(%BS)
%Ca (%BS)
%Mg(%ofBS)
CEC(cmol/kg)
pH of simulated acid
rain (3.3 vs 4.3)
Ratio of S:Nof
simulated acid rain
pH 3.3 vs 43:
| %BS (27.9 vs 31.3)
i %Ca (21.4 vs 24.0)
i %Mg(5.2vs5.8)
i %pH (4.49 vs 4.57)
t CEC (3.39 vs 3.00)
McCormick
EH04-3
Nutrient content in sap of
ted maple trees at 7 sites
along a deposition gradient
Pennsylvania
Sap chemist ty:
pH. ••
conductivity
speciHc ions
Atmospheric depos-
ition
Soil chemistry
Large tree-to-tree variation in sap chemistry
Positive relationship observed between sap concentration atmospheric
deposition and Ca, and soil exchangeable concentrations of Mg and
ofCa
Robarge & Smithson
SF12-2
Small-scale spatial
variability of soil chemical
parameters;
Roan Mtn., NC
Soil:
pH
extractable cations
titratable acidity
extractable sulfate
NandC
Within-plot variability (12x14m) for most soil chemical parameters is
high: >30% coefficient of variation
Variability generally remains constant with soil depth
Expressing results on a mass per unit area basis increases variablity
Expressing results as a ratio decreases variability
Assessment of between-plot and within-plot variability in the southern
Appalachian Mtns. suggests minimum detectable differences of > 10%
for soil chemical parameter* over time across all plots
Detecting differences in single plots over time is probably not possible
without extensive sampling per plot
Ryan & Huntington
SF05-8
Soil sampled on west
aspects at 840,1000, and
1200 m;
Mt. Moosilauke, NH
Soil and forest floor
extractable cations
Al
Soil type
Elevation
With f elevation:
t occurrence of ciyofolists, 4 spodosols
i soil mass in both soil types
in spodosols:
forest floor. 1 Ca, Mg, K, base saturation, t Al
mineral soil: j Ca andbase saturation, t Mg, K, ?A1
in ciyofolists:
forest floor 1 Ca, Ms, K base saturation, f Al
mineral soil: * Ca, M, t Mg, K, base saturation
Trends associated with elevation within soil types
continued
-------
Table 5. Soil/Nutrient Cycling Studies (continued)
hO
o
SOURCE
STUDY MATERIAL &
SITE CHARACTERISTICS
VARIABLES
OF INTEREST
ASSOCIATED
VARIABLES
RESULTS
Sasser and Binkley
SF17-2
2 fir waves: Eraser fir on
Mt. LeConte, Great Smoky
Mtns. National Park (1900
m, NE slope);
balsam fir on Whiteface
Mtn, NY (1200m, S slope)
Net N mineralization
Throughfall
Forest type
Forest zone (dead,
mature, regen-
eration, juvenile)
Net N mineralization: Dead and mature zones showed twice the rates of
regenerating of juvenile zones (43-61 vs. 21-39 kg N/hatyr)
Throughfall ranged from 4-10 kg N/hatyr across all zones at both sites.
75% of throughfall N was NH< for both site
N mineralization similar between mountains and relatively high at all
stages of stand development
Smithson et al.
SF12-7
Soil solution from field
lysimeters installed in 1986;
Mt. Mitchell, NC
Whitetop Mtn., VA
Soil solution:
pH
Al,
Ca,
Mg,
K,
Na,
NH4,
NOj,
SO«,
CI
Season
Elevation at Mt.
Mitchell (2006 vs
1760m)
Location:
(Mt. Mitchell vs
Whitetop)
Soil solution from high elevation at Mt. Mitchell is slightly more concentrated
in H, Al, and SO4 than low elevation, however differences are not
statistically significant.
Soil solution from Whitetop Mtn. more concentrated than solutions from
Mt. Mitchell
Seasonal variation in soil solution highly significant, especially for NO3, Al,
Ca and Mg
Al and NO} are dominant ions in solution
SO4 is accumulating in rooting zone. There is a net export of NO] and
possibly Mg (estimated to be 25 and 1 kg/ha/yr, resp. at Mt. Mitchell)
Al in soli solution at ML Mitchell Is generally less than 'harmful' (200 flM)
concentration. A larger number of samples had >200)WMAI
concentration at Whitetop Mtn.
Smithson & Robarge
SF12-6
Leachate from Oa, A, B
horizons collected near
MCCP study site and ex-
posed to simulated through-
fall in a lab study, same
sites as those used by Smith-
son et al. SF12-7
Mt. Mitchell, NC
Whitetop Mtn., VA
Leachate solution:
PH
Al,
Ca,
Mg,
K.
Na,
NH4,
NOj,
SO4,
a
Simulated throughfall:
pH:
deionized H2O
lx throughfall
2x throughfall
ionic strength:
lx throughfall
(created using K
salts)
Storage conditions
time (12 wks)
4°C
Solution concentrations of leachate increased with decreased pH of
throughfall; acid and salt treatments of equal ionic strength
have same effect; Ca, Mg dominant cations; Al concentrations < 100
//M; no change in pH; proton consumption equal to SO4 adsorption not
metal ion release; relative sensitivity to leaching: Oa > A > B horizon
Storage at 4 °C does not inhibit NOj formation; NOj release is immediate
following soil disturbance and lowers pH and increases Al concentration
in soil solution
Acidic Inputs via throughfall can cause short term changes In soli
solution composition. Short-term changes are dominated by base
cations, not AL
Straderet al.
SF17-1
Red spruce and Eraser fir
in 3 high-elevation sites (19
plots) ranging in elevation
from 1579-2CW6 m;
Mt. Mitchell, NC;
Qingmans Dome, GSMNP;
Whitetop Mtn, VA,
N mineralization rates in
situ
Throughfall N
Elevation
Aspect
N content of throughfall was high, (18-32 kg N/hatyr) indicating substantial
atmospheric deposition
N mineralization rates were high (26 to 180 kg N/ha/yr)
NO3 accounted for approximately 50% of total mineralized N on Clingmans
Dome and 40-50% on Whitetop Mtn.
Rates of N mineralizations were thought to be equalled by vegetation
uptake. If not, potential exists for cation leaching
*n
O
73
9
|
q
£
continued
-------
Table 5. Soil/Nutrient Cycling Studies (continued)
SOURCE
STUDY MATERIALS
SITE CHARACTERISTICS
VARIABLES
OF INTEREST
ASSOCIATED
VARIABLES
RESULTS
Wells et al.
SF21-4
Foliar and toil samples
from 115 permanent plots
and root samples from 30
plots in the spruce-fir
forests of the southern -
Appalachians at elevations
of 1525,1678,1952m
Mount Rogers, VA
Black Mountains, NC
Clingmans Dome,
TN
Foliar and root;
concentrations:
N.P.K,
Ca, Mg, Cu, Fe, Mn,
Zn, Pb, S, B, Sr, Ni,
Cd
Soil:.
pH (in water),
extractable cations,
titratable acidity,
extractable sulfate,
extractable metals
total N and C
Location
Elevation
Topographic
position(draw. -
slope, ridge)
Exposure(exposed
slopes: north and
west; protected:
east and south)
GSMNP,
Foliar concentrations:.
similiar for three locations; Ca and Mg near critical range; N and K may
be excess; P, S, Cu, Fe, Mn sufficient; 7 Zh
Red spruce do not appear to lie deficient In foliar nutrients except for Ca
' and Mg; Al is high and Increases with elevation.
Soil:
' Oi & Oe layer, mean(s.d.):
pH « 3.9 (0.32); base saturation - 35 (16); Ca: Al « 2.45 (5.02)
15-20 cm depth, mean(s4.):
pH = 4 J (032); base saturation « 73 (7.0); Ca: Al - 0.035(0.035)
pH, Ca, K, base saturation vary by location not elevation; Mg J with
elevation; Al, titratable acidity vaiy by topographic position; Pb > on
west aspects then on east aspects; total mass of Ca and Mg | with
*elevation; total mass of Pb, S, N, K t with elevation
Highly significant elevation-location Interaction for most soil
parameters. Within plot variability limits ability to detect significant
trends.
Witter et al.
EH03-7
Pregitzer et al.
EH03-4
Liechty and Mroz
EH 03-3
Nutrient cycling in sugar
maple-hardwood forest at 5
sites: 3 plots/site; along a
gradient from ne MN to sw
Mass fluxes between and
contents in:
foliage
forest floor (Ol),
(Oea)
woody biom ass
soil A A E horizon
soil B horizon
SO4 deposition
NO} deposition
Relative location
With T SO« and N deposition along gradient from northwest to southeast:
1 S contents in foliage and in Utter (Oi), related to f mass of Oi
t S fluxes in litterfalT and in soil leaehate
t N contents in litter (Oi), related to T mass of Oi .
0 foliar contents of N, Ca, Mg, K (Ca A Mg related to soil)
Nutrient contents in soils follow soil organic matter trends except S, which
follows deposition of SO4
Nutrient teaching below B horizon is greater than wet A dry deposition for
SOj/Ca, Mg, and K; only SO* follows deposition trend of SO4
Ca losses below B horizon > literature estimates of mineral weathering
Cations (Ca, Mg) fluxes in throughfall are at least weakly correlated with
deposition 01SO4
Nutrient cycling rates and pools are correlated with deposition trends of
SO4, N, and H
-------
Tabic 6. Root Studies
SOURCE
STUDY MATERIAL &
SITE CHARACTERISTICS
VARIABLES
OF INTEREST
ASSOCIATED
VARIABLES
RESULTS
Wargo et al.
SF15-1
21 red spruce co-dominant
trees in 3 decline classes at
950 m;
Mt. Abraham in Green
Mountain National Forest,
VT
Roots:
mycorrhizae
pathogen isolation
vitality
chemistry
Crown characteristics
(class 1, 2, and 3:
6-10%, 10-50%,
50-100% crown
deterioration,
respectively)
Increment cores
Branch condition
Class 2 and 3 trees showed greater radial growth reductions than class 1 trees
Declining trees had root decline symptoms: fewer non-woody fine roots,
fewer mycorrhizal tips, fewer morphological types of mycorrhizae, greater
discoloration, greater amounts of dead tissue, lower starch, lower soluble
carbohydrates, and lower soluble N concentrations
While some pathogenic fungi have been isolated, none of the "common" root
rot fungi have been isolated to date
Patterns of root and crown deterioration suggest that fine roots deteriorate
first, followed by deterioration of crown condition, finally followed by
woody root death
Decline In crown conditions of red spruce may be caused by a declining root
system
See also:
Smith and Armstrong-Colaccino SP05-12 Table 7
Clineei al. SC09-1 Table 11
Seedling studies Table 4
-------
Table 7. Forest Condition Studies
SOURCE
STUDY MATERIAL &
SITE CHARACTERISTICS
VARIABLES
OF INTEREST
ASSOCIATED
VARIABLES
RESULTS
Bnibaker
WC25-1
Increment cores from 13
old-growth Douglas-fir
sitesi .12 sites are in the
Puget Sound area, 1 in the
H J. Andrews Exp. Forest,
OR
Annual tree ring width
overtime
Monthly precipitation
and temperature
records from nearby
weatherstations
Overall radial growth increases since 1880; likely related to a regional
temperature increase.
No growth patterns appear related to pollution sources
Brocket al.
SF02-5
Ftoiir annual surveys of
forest condition conducted
in 16 plots, 272 red spruce
and 213 fraser fir were as-
sessed
Ml Mitchell, NC
..-Foliage loss
Live vs.dead
Time (1984-1987)
Crowns of both red spruce and.Fraser fir deteriorated over time
By 1986 7% of red spruce and 16% of Fraser fir had died, after winter of 1986-
87 41% of red spruce and 49% of Fraser fir had died
No causal.biotic agents observed
Abrupt Increase In mortality b thought to be doe to drought and severe
rime Ice
Confcey & Kcifer
SF05-13
Increment cores from 20
red spruce and 10 balsam
fir at eachof 6 sites on east
and west aspects at 840,
990, and 1140 m;
Ml. Moosilauke, NH, and
Northeastern US
Growth rate
Aspect
Elevation
Species
Tune
Growth increases in 1900 & 1940; a radial growth reduction beginning about
1955
Patterns similar for balsam fir and red spruce
No greater decline on west slope or with t elevation
Recent decline not clearly related to pollution, maybe related to climate
change
Dulletal.
SF26-1
Aerial photos and ground
surveys via Geographic In-
formation Systems (GIS);
southern Appalachians
Red spruce and fraser
fir cover typing and
standing dead
estimates
ML range
Elevation
Balsam woolly adelgid
occurrence
Fraser fir standing dead ranges from 44% on Roan Mtn. to 91% in the Great
Smoky Mountains
Red spruce standing dead ranges from 3% on Roan Mtn. to 14% in the Black
Mtns.
Fraser fir standing dead increases with elevation
Fraser fir standing dead b highly correlated with the presence of historical
adelgid Infestation; red aprace standing dead b not higher than expected
Federer et al.
VS06-12
Increment cores of 3001 red
spruce from broad survey
of four northeastern states;'
ME, NH, VT, NY
Basal-area increment
over time
Monthly precipitation
and temperature
records from nearby
weatherstations
High frequency variation of basal-oteanowth negatively correlated with
previous year summer temperature (July & August), and positively
correlated with'early winter temperatures
No change in growth/climate relationship since 1960
Suggests * regional climate signal for red spruce
Federer & Hornbeck
VS06-3
Increment cores of 3001 red
spruce from broad survey
of four northeastern states;
ME,NH,VT,NY
Average annual basal
area increment
Stand age and stand den-
sity as interpolated
from Myer*s normal
yield tables.
Mean basal area increments increased until the early 1960*s and have
decreased since
Maturation of stands throughout New England suggested as a possible cause
continued
-------
Table 7. Forest Condition Studies (continued)
SOURCE
STUDY MATERIAL &
SITE CHARACTERISTICS
VARIABLES
OFINTEREST
ASSOCIATED
VARIABLES
RESULTS
Friediand
SF08-17
Forest condition of canopy
trees assessed in 48 plots
stratified by elevation and
aspect on each of 19 moun-
tains in northern Ap-
palachians
NY.VT, NH.ME
Live vs. dead
Elevation (950-
1100 m)
Aspect ( w vs. e)
Mt. range
Abundance of red spruce varies among ranges (highest in White Mts., lowest
in Adirondacks)
42% of red spruce were dead, 13% of other species were dead
Greater percent red spruce standing dead in western mountains vs. eastern
mountains
Percent of standing dead red spruce is higher on west aspects vs. east aspects
(except Adirondacks)
Percent of standing dead red spruce increases with elevation (particularly
above 1000 m) In the Adirondacks and Green Mts., but not in more
easterly mts.; no trend for other species with elevation
Graybill & Rose
WC24-1
Increment cores of 889
stems representing older
trees at 41 sites on the
Mogollon Rim, AZ & NM,
or on several isolated moun-
tains in southeast AZ.
Ponderosa pine, Douglas-
fir were primary species
AZ
Actual radial growth
Predicted radial growth
using precipitation
records
Time
Location (northern
sites were more
distant from
sources of air
pollution than
southern sites)
Actual growth was less than predicted growth for the period of 1951-1986 in
63% of sites in the south and 38% of sites in the north
Reduced growth rates (Le., below those predicted by precipitation records)
may be due to higher precipitation In previous decades, air pollution,
and/or Increased competition from other stems
Hombeck et al.
VS06-5
Increment cores of > 5000
co-dominant trees repre-
senting existing forest ages,
basal area, and stocking
levels < 1000 m elevation
New England
Annual basal area
increment averaged
across all factors
influencing tree
growth
10 different species
which comprise
86% of New
England forests
Eight species (including sugar maple) had constant or increasing basal area
increments (white pine had highest)
Red spruce and balsam fir had recent decreases in basal area increments
Maturation of stands Is suggested for decreases
LeBlanc
EH05-7
Increment cores from 30
white oak and 30 black oaks
at each of 7 sites;
AR to OH
Change in individual
tree mean DAI and
BAI trend between
pre- and post-1960
Tree age
Competition data
B-horizon Ca:AI ratio
18-33% of black oak and 7-20% of white oak exhibit radial growth reduction
at sites with low soil Ca:Al ratios, but no white oak and 5-10% of black
oak exhibit growth decline at sites with B-horizon Ca:Al ratio > 0.25
No relationship between growth reduction and tree age or competition
Natural or soil-acidlflcatlon-lnduced low Ca:Al ratio may adversely affect
white and black oak growth on low nutrient, poorly buffered soils
Milier-Weeks & Cooke
V314-3
1
Four annual surveys of co-
dominant trees conducted
in 80 plots with 50% red
spruce or balsam fir. Eleva-
tion from 300-1200 m
Adirondacks & Tug Hill,
NY, White Mt. Nat. For.,
VT & NH, Mongahela,
Nat. For., WV, and
Berkshire; of MA
Crown condition
(assessed visually)
Live vs. dead
Time (1985 -1988)
Overall tree crown conditions have deteriorated since 1985, but only a small
% of trees have died
Annual mortality appears very low
Trees are exhibiting foliage loss but little discoloration
Foliage loss attributed to individual branch dieback & mortality
continued
-------
Table 7. Forest Condition Studies (continued)
SOURCE
STUDY MATERIAL &
SITE CHARACTERISTICS
VARIABLES
OF INTEREST
ASSOCIATED
VARIABLES
RESULTS
Pedersori & McCune
SK05-18
Mortal ity rates of 177 dead
trees (>20 cm dbh) were
determined for the past 20
yean at each of 7 sites
alonga gradient of add
deposition;
ARtoOH
Decade by decade mor-
tality rates
Cause of death for the
major species
Relative position on
an acid deposition
gradient
Decade '68 ¦ 77
78 - "87
Among the 7 sites, mean and range of mortality rates (stems/ha/decade) for
all species:
1968-1977:833,6.25.15.62
1978-1987:17.71,833-27.08
Individual mortality rate of o»»*rrm mhm and Caty* rpp. was greater than
O.alha
No apparent differences in cause of mortality between decades
Increased mortality In 78 • *87 rersus '68 - *77 (p *>0.10)
No trend In mortality along an add deposition gradient In either decade
Peterson et at.
WC26-3
Foliar injury and growth
measured in 56 ponderosa
pine stands (either symp-
tomatic or asymptomatic);
Siena Nevada Mountains,
CA
Crown condition growth
ring widths vs. time
sen es
Temporal and spatial
variation in growth es-
pecially pre 1950 vs.
post 1950
Ozone gradient
Symptomatic trees vs.
asymptomatic trees
High degree of variation among trees and stands in symptomatic injury and
tree growth data. Some regional patterns are apparent.
Symptomatic Injury data indicates gradient of Oi induced injury (greatest in
southern Sierra Nevada, lowest in north) and that there is a
high level of pollutant stress
Individual basal area growth analysis of symptomatic southern sites
Indicate general J trend of growth since 1950 In areas of high Os
exposure and tr\|uiy. II Is thought that O3 Injury plays a rote In the
stress complex
Peterson & Arfcaugh
WC26-1
Increment cores from 56
sites of ponderosa pine; 28
sites are on the western
edge, 28 sites are on the in-
terior;
Sierra Nevada Mountains,
CA
Annual tree ring width
over time
Monthly precipitation
and temperature
records from nearly
weatherstations
No apparent large-scale regional reduction of tree growth in the most recent
years
There is a suggestion that the more southern western edge sites are growing
more slowjy than the interior southern cites.
Oj has been suggested as a possible contributor (a growth redactions
Smith & Armstrong-
Colaccino
SFOS-12
Pathogenic symptoms
visually assessed on 189 co-
dominant red spruce trees
in 19 plots at stratified loca-
tions; 46 red spruce trees
destructively sampled for
branch and root assess-
ments
Mt Mooeilauke, NH
Live vs. deadlrees
Foliar discoloration and
loss
Specific symptoms
associated w/crown,
seedlings, branch,
roots
Elevation (824-1172
m)
Aspect (w & e)
Soil type (histosols vs.
spodosols)
Percent standing dead of red spruce ranged from 8 - 52% and averaged 33%,
highest percent occurred at mid elevations w/some differences between
aspects or soil types
Branch and stem symptoms were abundant, unexceptional, and characteristic
of well-appreciated red spruce symptoms
Branch necrosis appeared associated w/crown abrasion caused by wind
damage
No significant symptoms were associated w/roots
Seedlings were generally asymptomatic but not abundant
Red spruce straw symptoms of moderate decline. Any role of air pollution
was not clarified - full potential of surrey win be realized If repeated In
future
-------
Table 7. Forest Condition Studies (continued)
SOURCE
STUDY MATERIAL &
SITE CHARACTERISTICS
VARIABLES
OF INTEREST
ASSOCIATED
VARIABLES
RESULTS
Witteret al.
EH03-2
Forest condition survey con-
ducted in 3 plots at each of
5 sites in similar sugar
maple-hardwood stands
along a SO* deposition
gradient from ne MN to sw
MI
Tree species
Mortality
Biomass
Recruitment (>5 cm
dbh)
SO* deposition
Relative location of
site on gradient
Comparing the plot means of the 5 sites along the deposition gradient:
no differences in net standing biomass or biomass increment of total stems
or of sugar maple stems
Differences in mortality were observed and are thought to reflect.
differences in drought conditions in 1988
Growth rates (biomass or basal area increment) of surviving trees
(excluding newly recruited stems) at 1 site was higher than others
No conclusive evidence that SO* or NO3 deposition Is altering forest growth
or mortality
Zedaker et al.
SF25-4
Nicholas et at.
SF25-6
SF25-7
Four annual surveys of
spruce-fir forests con-
ducted in 129 plots,
stratified by elevation,
aspect and topography type
Mt. Rogers, VA, Black
Mtns., NC, and Great
Smoky Mtns.,TN and NC
Seedfall and viability
Regeneration
Crown condition
Standing dead
Elevation (1524 -1981
m)
Location
Time (1985-1989)
Basal area of standing dead trees increases with elevation
Percent basal area of red spruce classed as dead:
< 10% at all sites in Smoky Mtns., 2 lowest elevations in Black Mtns., and
low elevation site at Mt. Rogers
> 25% at highest elevation sites at Black Mtns. and Mt. Rogers
Percent basal area of dead fraser fir ranged from 32 - 59% among Mt. ranges
Red spruce crown condition declined over time and with increasing eleva-
tions in the Black & Great Smoky Mtns. from 1985-1988: no decline in
crown condition at Mt. Rogers
Germination of red spruce seeds within expected levels
No indication that abnormal events art occurring; no link to air pollution;
droughts In 1986, '87, and '88 and an Ice storm In winter or 1986 • 87
should be considered In evaluations of causes
-------
Table 8. Winter Injury Studies
SOURCE
STUDY MATERIAL &
SITE CHARACTERISTICS
VARIABLES
OF INTEREST
ASSOCIATED
VARIABLES
RESULTS
Andersen & McLaughlin
SF10-2
Red spruce saplings al 1720
and lnS m elevation on
Olngmans Dome, TN
Welter relations assessed
through analyses of
pressure-volume
curves on shoots
'Elevation
During the period of cold hardening, saplings at higher elevation site had
higher saturated osmotic potential reflecting tower solute concentrations
Low solute concentrations may.reflect reduced winter hardening at the
higher elevation site
DeHayes et al.
SF20-1
3-year-old potted red
spruce seedlings, repre-
sentative of Riversdiate, and
Chatham and Waterville
Valley
Foliar N concentration
Shoot growth
Cold tolerance
(electrolyte leaching)
Applications of NH<,
NOj, with or
without P fertilize]
Timing of N appli-
cation up to
Level of N applied to
rooting media (0,
300,1500, 3000
kg N/ha/yr)
N supplements enhances cold tolerance
f foliar N concentrations associated with t N treatment in all cases
P had no effect on foliar N concentration or on cold tolerance
Growth response to N supplements evident only for early-summer treatment
Cold tolerance less responsive to nutrient supplementation applied in early
summer period of active shoot elongation
Enhanced cold tolerance due to soil applications of N appears to be In
direct conflict with "Mitogen fcrtllbatloa" hypothesis
Jacobson el al.
SP06-3
Seedlings in field and lab.
. experiments
Boyce Thompson Inst., NY
Cold tolerance of need-
les by electrolyte
leakage
Sulfate and nitrate
applications
N fertilizer to roots lowered cold tolerance of needles prior to hardening,
raised cold tolerance daring hardening
Sheppatd el al.
SF14-2
Sample shoots of red
spruce from NY, TN, Scot*
land,-Whiteface Mini, and
Newfound Gaps, collected
at 1-3 weekly intervals
Autumn hardening
assessed via develop-
ment of visible tissue
necrosis 14 days after
freezing at various
temperatures
Temperature records
over past 22 yean
at the sites of
sample collection
Historically, minimum air temperatures occasionally fell below the calculated
LTio (temp for 10% kill)
Individual trees differed fai hardiness by up to 10°C
Pollutant-Induced freezing Injury Is Ins am dent, on lis own, to account for
red spruce decline In the Appalachians
Wilkinson
SF19-3
30-year-otd red spruce trees
in rangewide provenance
test sile planted in 1960.
The, 12 provenances range
from 60-1620 m in elevation
and from 35° 36* N to 46°
55* N
Annual radial growth
3-ycar radial growth
3-year height growth
Basal avca growth
Crown injuiy/needle
damage
Winter injuiv
assessed annually
for 3 years (198£>-
1988)
| in radial increment, basal area increment, and height were greatest for
trees with the highest proportion of damaged needles in upper crown or
thoee that were most frequently damaged over the last 3 years
Radial growth reductions Uisting up to 3 yean was observed in trees injured in
oinly a single year
Results support the hypothesis that winter Injury Is a contributing factor In
red spruce decline
Sec also the following studies:
Cape ct al. SP14-4 Table4, Eastern spruce am) fir
Neighbour and Melhorn SF14-16 Table 4, Eastern spruce and fir
Fincher el al. SP16-4 Table 4, Eastern spruceand fir
Vann ei al. SP34-2 Table 9
-------
Table 9. Physiology Studies
SOURCE
STUDY MATERIAL &
SITE CHARACTERISTICS
VARIABLES
OF INTEREST
ASSOCIATED
VARIABLES
RESULTS
Amundson et a!.
SF31-3
i
1
3 naturally regenerated stands
of red spruce:
Millinocket, ME - young
stand, low elevation (518 m),
low pollution
Howland, ME • mature stand,
low elevation (105 m), low pol-
lution
Whitefaee Mtn., NY - mature
stand, high elevation (1090 m),
high acidic dep. and O]
Net photosynthesis
Foliar chemistry
Stomatal Conductance
Age of stand
Pollution level (con-
founded by ele-
vation)
Whitefaee Mtn. vs. Howland
m:
Ps > at Howland
Stomatal conductance similar at both sites
1286
Ps and stomatal conductance similar at both sites
1987:
Ps similar at both sites
Stomatal conductance > at Howland
19R8;
Insufficient Data
Millinocket vs. Howland
1221
Ps similar at both sites
Stomatal conductance > at Millincoket
Ps and stomatal conductance > at Millinocket
1988:
Ps and stomatal conductance decline rate during autumn > at Howland
Whitefaee vs. Maine sties:
J Ps, foliar sugar, P, Ca and Mg
i In foliar starch occurred one month earlier
f foliar N
Assimilation may be Impaired, suggesting accelerated leaching from foliage or
1 uptake from soli
Halpin et al.
SC18-2
Seedling and mature tree com-
parison of loblolly pine;
Athens, GA
Needle retention
Photosynthesis
Stomatal conductance
Tree age (seedling vs.
mature)
Seedlings vs. mature trees:
80% vs. 0% retention of previous year's foliage over winter
24% t photosynthesis
24 % f stomatal conductance
t number of flushes
Based on stomatal conductance, seedlings may be more sensitive than mature
trees to air pollution
continued
-------
Table 9. Physiology Studies (continued)
SOURCE
STUDY MATERIAL &
SITE CHARACTERISTICS
VARIABLES
OF INTEREST
ASSOCIATED
VARIABLES -
RESULTS
Houpis et al.
WC20-1
Mature ponderosa pine at
1280 m;
Siena Nevada Mountains, CA
nC02 distribution
Within tree branches
(branch autonomy)
Position of canopy
brancblets pulsed
with COi
High degree of branch autonomy with respect to carbon allocation
Branch exposure chamben
(BEC);
Livermore, CA
Airflow & speed
Air temperature
Light intensity
Ozone concentration
CO2 concentration
Acidic precipitation
deposition
Ambient vs. chamber
environment
Actual vs. target treat-
ment concentra-
tions
Air flow; > 3 chamber air exchanges/min., no dead spots, good mixing
Air temp: < 3° C elevation from ambient
Light: transmission of PAR > 90 % efficient
Ozone: no sig. gradients (<10 ppb differences w & w/o foliage); scrubbing
efficiency > 80%
COz no sig. gradients ( < 10 ppb differences w & w/o foliage); BEC can
measure variation in CO2 uptake due to natural ambient conditions
Acidic depostksn: rates vary from 12-19 mm/h
BBC performs well and meets performance requirements
Kossuth
SC11-1
Branches of mature slash pine
grafted onto roots (mature
clones) and rooted cuttings of
juvenile spruce pine (E.
yiahrgl (seedling clones)
grown in greenhouse chambers
Diameter
Height
Branch length
Stomatal openings
(via electron micios-
copy)
4 levels of Oj (0-300
ppb) for 1 year
High Ojvs.0ppb:
mature branches:
) 12% in diameter
T 8% in length
1 7% in height
t 80% size of stomatal openings in new needles
reduced or altered wax layer over stomates
seedlings: -
1 78% total weight
4 45% height
i 43%diameter
i 88% root wight
Oj reduces abore ground growth and carbon allocation to roots; mature
branches are similar (but less responsive) than Mwlllng»i responses
more pronounced on expanding tissue
McLaughlin et al.
SF10-3
30 saplings and 10 mature red
spruce at 2 sites (1720 and
1935 m) in red spruce forests;
Southern Appalachians, NC
Net Ps and dark
respiration
Plant and soil
chemistry
Growth
Elevation
Light levels
Greater radial growth decline at higher elevation over last 20 years
Greater radial growth decline at lower elevation during last 5 years
High elevation vs. lower elevation:
sapling growth 40% slower
4 Ps at low light level, no difference at saturated light level
t Respiration
foliar nutrients: f Al; | O, Mg, P, similar N
soil concentration: f P. K, Al; | Ca
f atmospheric Inputs of anions at high site may mobilize Al In soil and In
tissue acWerwIy affecting physiology
continued
-------
Table 9. Physiology Studies (continued)
SOURCE
STUDY MATERIAL &
SITE CHARACTERISTICS
VARIABLES
OF INTEREST
ASSOCIATED
VARIABLES
Results
Norby et al.
SP10-1
Red spruce seedlings/saplings
from 3 sources grown in green
house: New Hampshire and
Nova Scotia, both 1 year old
(from nursery); Great Smoky
Mtn. N.P., 5-15 years old.
Nitrate reductase
activity in needles
Visible injury
Exposure to simu-
.lated:
N02(75ppb)
HNOjHSppb)
Acid mist (pH 3.5
and 5.0)
Plant source
NOi induced nitrate reductase in both nursery-grown seedlings and older
saplings from the GSMNP though nitrate reductase activity was lower
in nurseiy-grown seedlings
HNOj vapor also induced nitrate reductase activity
Acid mist containing nitrale did not induce nitrate reductase activity
No visible foliar injury with NOz exposure
Significant visible injury with HNOj exposure
No nitrate accumulation in needle tissue for both HNO3 and NO2
exposures
Red spruce Is capable of assimilating NOi and HNO3 vapor, therefore
excess N hypothesis Is tenable
Rebbeck et al.
SF32-1
Experiment I:
Red spruce juvenile ( < 4
years J and mature (>25
yean) scions grafted on
rootstock in open-top cham-
bers at low-elevation sites in
Maine
Experiment It:
Red spruce and balsam fir
seedlings grown in open top
chambers as above with dif-
ferent Oj regime
Exp I:
Diameter, height
Net photosynthesis
Stomatal conductance
Chlorophyll content
Exp II:
Diameter, height
Net photosynthesis
Stomatal conductance
Chlorophyll content
Experiment I:
5 levels of Oj
(CF-ambient +
150 ppb)
4-5 mo/yr tor
2 years
Experiment II:
3 levels of Oj
(AA, CF.&NF)
Yrl -2 months
Yr2 -4 months
2 mo/yr for 2 years
Experiment I:
At highest O3 (ambient + 150 ppb) juvenile scion diameter growth 1
27%. No other treatments were significantly different from CF air for
either juvenile or mature scions
23% | chlorophyll content in juvenile rootstocks vs. mature or juvenile
scions. Chlorophyll content of mature needles > juvenile needles
Highest chlorophyll levels at ambient +75 ppb
Al ambient +• 150 ppb, photosynthesis was reduced by 44% & 29% for
juvenile and mature scions, respectively
Experiment II:
Chlorophyll content of balsam fir > red spruce
Highest levels of chlorophyll occurred at CF for both spp.
No growth data available
Vann et al.
SF34-2
Branch chambers on each of 4
mature red spruce for 3
months at 1160 m;
Whiteface Mtn., NY
Needle:
mass
chlorophyll
carotenoids
cuticle thickness
total-cutinized layer
thickness
Stomatal wax plugs
Winter injury
Removal of:
cloud mists
Oj (and other char-
coal-reactive gases)
Addition of "clean"
mist
Photosynthetic pigments, cuticle, wax:
t w/removal of "pollutants" and addition of 'dean* mist
no change w/removal of "pollutants" only
No treatment effects on needle mass
Winter injury:
j w/removal of "pollutants" and addition of "clean" mist
Ambient cloud mlsto and O) affects foliage and Increases winter fi\Jury.
Interaction observed wllh humidity
Wiselogel
SCI 8-3
14-year-old loblolly pine grow-
ing in a plantation
Athens, GA
Leaf area
Net carbon exchange
Dark respiration
Branch growth
03 (ambient to
ambient)
Water availability
(Irrigated vs.
non-irrigated)
i photosynthesis in 2.5x ambient treatment
Response of 14-year-old trees Is slmlllar to response of seedlings
-------
Table 10. Insect/Pathogen Studies
SOURCE
STUDY MATERIAL &
SITE CHARACTERISTICS
VARIABLES
OF INTEREST
ASSOCIATED
VARIABLES
RESULTS
Brock
SF02-3
Survey of insects and
pathogens in spruce-fir
forests, 1985-1988;
Southern Appalachians
Insect/pathogen
preserfce:
stems
branches
foliage
roots
Tree decline
No correlation between tree decline'and insects except balsam woolly
adelgid
Balsam woolly adelgid was found on 50% of fniser fir
Blottc Insect and pathogen Infestation not Important In red spruce decline
• In southern Appalachians
Grehan
SF99-16
I:
Larvae and adults of
conifer swift moth sur-
veyed iii spnice-fir forest!
oo Mt'Moosilauke and
Whiteface Mtn. between
500-1300 m
It
One year old red spruce
seedlings Inoculated with
larvae in field at Mt
Mansfield and Whiteface
Mtn.
I:
Larval density
II:
Foliar dieback
Root mass
I:
Aspect
Elevation
II:
Larval presence
I:
Larve and adults were recorded at all elevations and abundant at 700 -
1100 m
Greater larval numbers occur on slopes facing prevailing winds
It
Presence of one or more larvae per seedling resulted in significant increases
in foliage dieback and reduced toot mass
Conifer swill moth KoraghtHfllm nwlhli h common In the NE and
potentially a factor affecting red spruce regeneration
Hartman el al.
SF02-4
Fraserfir and red spruce
trees at vaiying elevations;
Southern Appalachians
Parasitic nematode
densities
Composite soil-root
samples
Tree decline status
Elevation
With T elevation: f plant-parasitic nematodes, tree & crown decline
Weaker or negative correlation of nematode densities with crown decline
Nematodes probably not related to uwu condition
. Knight & Grosman
SF99-6
Spruce-fir forests; 3 plots
(/SO, 960, & 1110 m) at ML
Moosilauke, NH; 2 plots at
How1and,MB
Insects
Other invertebrates
Elevation
33 insect species associated with red spruce.and/or balsam fir were found
Large numbers of ghost moth (may contribute to red spruce decline)
No Indications of epidemics or outbreaks associated with tree decline
Smith & Armstrong-
Collaccino
SFQ5-12
Pathogenic symptoms
visually assessed on 189 co-
dominant red spruce trees
in 19 plots at stratified loca-
tions
Ml Moosilaake, MB
Roots:
fungal/insect
infections
Forest floor,
nematode densities
Elevation (824-1172m]
Aspect (e &w)
Soil type (histosols vs.
spodosols)
No relationships to elevation, aspect, or soil type were observed
No significant infections or physical wounds were observed on fine roots
Forest floor nematodes exhibited high population densities (by Bierman
FUnncl technique) between 20,00O-50^XX>worms/l00g(dw). Nematodes
pathogenic to red spruce roots were not specifically determined.
Tobi et al.
SF99-7
Spruce-fir forests;
Camels Hump Mtn., VT
Ghost moth densities
Elevation
Larvae, pupae, and adults present at all elevations, with more present at
higher elevation, (positive correlation)
Large number of dead seedlings exhibited girdling injury
Moth larvae are agents of smiling mortality
I Weidensaul et al.
SFC8-6
High-elevation spruce-fir
forests;
Whiteface Mtn., NY
Insect/pathogen presence
Elevation
Crown class
Tree dbh
Species
Insects and facultative parasites are not Important as triggering stresses In
the process of tree decline
-------
Taoie 11. FRP Literature Review
SOURCE
TOPIC OF REVIEW
CONCLUSIONS
Air Pollution and Winter Injuiy
of Red Spruce
Workshop Results
(Adams, ed.)
Summary of results from working groups on
a) cold tolerance and winter injuiy under
ambient conditions
b) experimental results
c) physiological/biochemical mechanisms
Current-year needles of red spruce are inherently susceptible to winter injuiy because of low
mid-winter hardiness levels and because of the likelihood of mid-winter dehardening during
above-freezing temperatures
Lab studies show that sulfate, but not nitrate, deposition can reduce fall and early winter cold tolerance
of red spruce by 3-4 C, thus increasing susceptibility to winter injuiy
The cause of winter injuiy symptoms in the field has yet to be elucidated because "critical* temperatures
for the field cannot be determined from lab studies, and examination of current data on field winter
injuiy and weatherconditions does not clearly suggest either desiccation or freezing
The hypothesis that air pollution predisposes high-elevation red spruce to winter Injury via reduced
cold tolerance Is tenable but natural mechanisms, especially winter it\Juiy via environmentally
Induced desiccation, cannot be ruled out as an explanation of Increased winter Injury. While
there Is evidence of forest decline as a result of localized severe winter lr\Jury, this relationship
Is not well established because winter Injury does not occur consistently with severe climatic
conditions
Binkiey et al.
SC16-2
Evaluate susceptibility of forest soils to chemical
changes due to S & N deposition in SE US
Leaching losses of base cations may have | in an amount equal to about 0.5 to 1.0 kmol/ha/yr as a
result of acidic deposition, perhaps representing a doubling or tripling of background rates
Cannot assume weathering rates are sufficient to prevent depletion of exchangeable cations
Does not support the assumption that forest soils In the South will remain relatively
unaffected by the deposition of S St N compounds
Clir.c et al.
SC09-1
Effects of N on mycorrhizae in SE US and world-
wide
No direct adverse effects of deposited N on mycorrhlzae expected
Cregg et al.
SC18-1
1
I
A literature review highlighting ecophysiology dif-
ferences of seedling and trees as a consideration
when evaluating responses to environmental
stimuli
At the level of physiological processes, seedlings and trees often perform alike. Great differences
exist in structure ana form which may lead to significant differences in diurnal and environmental
responses
Flagler et al.
Southern Case Study
SC99-20
The research strategy of the Southern Commer-
cial Forest Research Cooperative and its most
current findings (9/89) with regard to forest
decline. Emphasis is on results of controlled
exposures of 03 and acidity to southern pine
seedlings in screening studies (1st yr), at Intensive
Research Sites (2nd & 3rd yr), and from mature
branch studies. Conclusions predicated on
incomplete results from all studies; conclusions
may change as these studies or additional analyses
are completed
Acid rain:
No evidence of negative effects upon the growth and physiology of southern pines (based upon
studies designed to study short-term, direct foliar effects, rather than soil mediated effects)
Ozone:
Convincing evidence of significant negative effects on the growth and physiology of southern pines:
4 Ps, f chlorophyll, and altered carbon and nutrient status. Results varied significantly due to
genotype, but combined analysis of 21 genotypes was negative overall
Ambient concentrations impaired growth and physiology in many instances, but in other instances
effects were not noted until 2 x ambient or at any concentration ; in one case, growth increases
were observed at 1.5 x ambient 03
Many growth effects manifested after the first year of exposure maybe linked to a premature
senescence of foliage associated with O3
Seedling; and mature trees were both affected negatively, but seedlings appear more susceptible
Acid rain x ozone:
Few interactions noted; where present 4 pH resulted in more negative ozone effect
continued
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Table 11. FRP Literature Review (continued)
SOURCE
TOPIC OF REVIEW
CONCLUSIONS
Gamer etal. *
SC01-1
Literature review to determine which substances
are most likely to affect eastern hardwoods,
spruce-fir, ana southern pine forests:
1) Oj and other photochemical oxidants, alone,
or in combination with atid deposition or
2) atmospheric deposition of acidic and .
acidifying substances alone
Review concentrate* upon above-ground, foliage-
mediated responses and contain no FRP
results
Ambient deposition of S and N probably will increase growth in many eastern forests; detrimental effects
of N deposition are more likely in high-elevation forests
0} has been proven to cause foliar injury and decrease growth in some eastern white pine seedlings and
also induce visible foliar injury and decreased photosynthesis in several species of pine and oak
seedlings. Ambient O3 concentrations in eastern North America are sufficient to decrease
photosynthesis and growth, increase foliar injury, and alter C allocation between roots and shoots
in sensitive and intermediately sensitive vegetation
SO: can reduce photosynthesis and growth, increase foliar injuty and mortality, and alter C allocation
between roots and snoots. SO2 concentrations in areas near major point sources cause visible injury
to vegetation, but concentrations are rarely high enough to be injurious to forests at the regional
level
Gaseous NOx at ambient concentrations not proven to cause increased foliar injuiy, increased
mortality or decreased growth of trees
The co-occurrence of phytotoxic concentrations of Oj, SOi and NOx are rare, thus eastern US forests
appear to be at low risk of injury from gaseous pollutant mixtures (based on present but inconclusive
evidence)
Toxic gases are the only airborne pollutants shown to cause visible Injury, decreased growth, and
mortality of forest trees In North America. Acid deposition at ambient concentrations has not been
shown to Induce detrimental effects on forests
McLaughlin
SF10-13
Summary of key C assimilation and
allocation processes; summarizes gaps in
understanding of pollutant effects on these
pathways
Information need:
Quantification of interrelationships between photosynthesis, respiration, translocation, and
metabolic repair as they influence availability of photosynthate under chronic exposure
to pollutants
Characterization of shifts in C allocation between roots and shoots due to direct and indirect effects
of pollutants and deposition
Evaluation of changes in levels and types of storage reserves in pollution-stressed trees, in terms
of altered resistance to disease anif altered physiological resilience
Examination of time series of growth patterns of larger trees In the field to test for shifts in response
to natural stresses
Meadows et al.
SC03-1
Natural and airborne chemical stresses on growth
of trees and forests
Direct effects of simulated acid precipitation on trees have been demonstrated, but only by treatment
with artificial add precipitation ofpH 3.0 or less
Indirect effects of acid precipitation on forest productivity may occur through alterations in forest soils
Field studies have thus far failed to demonstrate that these potential effects have occurred over a
widespread area in North America
No conclusive evidence that add precipitation has caused detrimental effects on forest productivity in
North America
Short-term exposures to high concentrations of gaseous pollutants are more detrimental to
photosynthesis and growth than long-term exposures to low concentrations at equal doses
Ambient O) concentrations above 50 ppb have been shown to cause reductions in net
photosynthesis and growth of several types of vegetation, even in the absence of visible injuiy
O) (and possibly other oxidants) is the only regionally dispersed air pollutant known to have injured
foliage, decreased growth, and increased mortality of sensitive tree spedes over a wide geographic
range
Heavy metals deposited from the atmosphere or mobilized in soils are important, at least on a local
scale
The diversity of sites, spedes, and stand conditions exhibiting dedine argue against any one single factor
as the pnmaiy causal agent in the observed dedines in Europe and the Northeast
Natural stresses, especially drought and temperature stress, may be much more detrimental to
vegetation than aiibome chemical stresses
continued
-------
Table 11. FRP Literature Review (continued)
SOURCE
TOPIC OF REVIEW
CONCLUSIONS
Miller ct al.
EH02-1
Tree mortality events in the eastern hardwoods
Over the last century were reviewed to determine
whether, there are'relationships between mor-
tality patterns over time and current patterns of
atmospheric deposition. Species considered were:
American beecn, black cherry, eastern white pine,
northern red oak, shagbark hickory, sugar maple,
white oak, yellow birch, and yellow-poplar.
The apparent increase in the decline and mortality of many hardwood species during the last few
decades may be due to intensification of reporting and to maturation of the forest itself
Most mortality is due to abiotic and biotic stress factors such as weather, silviculture, and damage by
insects and disease
There is evidence of damage to hardwoods by atmospheric pollutants from point sources such as
smelters, and to eastern whitepine from ozone
There Is no conclusive evidence of an association between patterns of hardwood mortality and
regional atmospheric pollution
Richter
Southern Case Study
j SC99-19
!
i
f
I
1
Effects of S & N deposition on forest soils of the
SE US
Two important soil-mediated effects are likely due to acidic S & N deposition:
11 negative short-term effects of accelerated leaching of Ca, Mg, & Al due to S04 deposition
2) positive long-term effects of N fertilization on forest productivity, the timing and magnitude of
which are uncertain because of lack of information on rates on N transformations and of the
contrasting influence of intensive forest management
Forest soils most susceptible to these effects have moderate to extreme acidity, low CEC, and low
weathering rates
Areal extent of forest soils susceptible to these effects has been estimated at 2.8-15.9 mil ha (based
upon data with large uncertainties
Processes countering acidification and leaching in highly weathered soils:
1) soil sulfate absorption
2) nutrient cation uptake by deep roots
3) release of nutrients from secondary soil minerals
4) atmospheric deposition of nutrient cations
Acid deposition Is expected to affect soils; timing is unknown
Shedwick et al.
Southern Case Study
SC99-21
Ambient air monitoring of wet and diy deposition
(1978-86) and gas concentration (1978-83) for 6
regions in the south:
1} Piedmont
2) Inner Atlantic Plain
3) Eastern Gulf Plains
4) Western Gulf Plains
5^ Outer Atlantic Plain
6) Eastern Gulf Flats
Range for 6 regions:
pH: 4.47 ¦ 451
SO4:0.95 -1.88 mg/L; 12.00 - 21.3Skg/ha/yr
NOj: 0.60 -1.00 mg/L; 7.00 - 11.60kg/hatyr
NH«: 0.07 - 0.22 mg/L; 0.63 - 2.38kg/ha/yr
Oj: 7-hour mean - 51 ppb in Piedmont/mountain/ridge regions, 43 ppb in coastal plain region
S02 & NOx rarely at harmful concentrations long enough to injure plants
Annual precipitation-weighted concentration and wet deposition levels for H, SO4, and NO3 Ions are
significantly higher In the Piedmont than each of the other regions
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