PB84- 198944
Response cf 'Carex'-Dominat«d Wetlands to
Altered ivwperatute and Flooding Patterns
Wisconsin Power P.'.ant Impact Study
Wisconsin Univ.-Madison
Prepared for
Environmental Research Lab.-Duluth, MM
Sen 83
»C?^^^ rf »S3Baffi;aJ!Bfta!;'5
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Page Intentionally Blank
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EPA-600/3-83-081
September 1983
RESPONSE OF t?AREX-DOMINATED WETLANDS TO
ALTERED TEMPERATURE AND FLOODING PATTERNS
Wisconsin Power Plant Impact Study
by
Barbara Bedford
Orie Loucks
Institute for Environmental Studies
and Wfcter Resources Center
University of Wisconsin-Madison
Madison, Wisconsin 53706
Gi-ant No. R303971
Project Officer
Gary E. Glass
Environmental Research Laboratory-Dul uth
Duluth, Minnesota 55804
This study was conducted in cooperation with
Wisconsin Power and Light Company,
s* Madison Gas and Electric Company,
Wisconsin Public Service Corporation,
Wisconsin Public Service Commission
and Wisconsin Department of Natural Resources
ENVIRONMENTAL RESEARCH LABORATORY-DULUTH
OFFICE OF RESEARCH AND DEVELOPMENT
U.S. ENVIRONMENTAL PROTECTION AGEMCY
DULUTH, MINNESOTA 55804
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TECHNICAL REPORT DATA
(ftefte rout Instructions on tht tvene
i. REPORYNO.
EPA-600/3-83-081
3. RECIPIEIMT-S ACCESSION NO.
4. TITLE AND SUBTITLE
Response of Car-ex-Pominated Wetlands to Altered
Temperature and Flooding Patterns: Wisconsin Power
Plant Impact Study
B. (HCFORT DATE
September 1983
6. PERFORMING ORGANIZATION CODE
7. AUTMOFKSI
B.L, Bedford and 0. Loucks
». PERFORMING ORGANIZATION NAME AND ADDRESS
Institute for Environmental Studies
University of Wisconsin-Madison
Madison, Wisconsin 53706
S. PERFORMING ORGANIZATION REPORT NO.
10. PROGRAM ELEMENT NOT
TT CONTRACT/GRANTNO.
12. SPONSORING AGENCY NAME AND ADDRESS
Environmental Research Laboratory
6201 Congdon Blvd.
U.S. Environmental Protection Agency
Dulcth. MX 55804
13. TYPE OF REPORT AND PERIOD COVERED
14. SPONSORING AGENCY CODE
EPA/600/03
15. SUPPLEMENTARY NOTES
16. ABSTRACT
This report presents the 1974 to 1977 results of a study undertaken on the site
of the Columbia Electric Generating Station to determine the effects of leakage from
the cooling lake on wetland vegetation. Results showed that changes in water levels
and -jater temperatures caused by Seepage from the cooling lake led to significant
charges in wetland plant populations and communities within 1 yr after the Columbia
Station began operation. Dominant perennial rhizomatous species of rarer decreased
in density and distributior., hydrophytic species increased, and Annual species increases:
markedly. A predominant trend of decreasing species diversity and richness was observed
fro*!. 1974 to 1977. However, no uniform relationship was observed between diversity and
intensity of disturbance—neither species richness nor distribution of their abundances.
Recommendations for future research are made with respect to the development of
effective management and assessment tools for wetland plant communities.
17.
KEY WORDS A'.D DOCUMENT ANALYSIS
DESCRIPTORS
b.lDEMTIFIERS/OPEN ENDED TERMS
C. COSATl FfeM/GtOUp
1». DISTRIBUTION STATEMENT
19. SECURITY CLASS
Unclassified
SO. SECURITY CLAftS (TMtfSSrl
Unclassified
22. PBICE
CPA Pww 2220-1 (IU«. 4-77) »MBVIOUI HOITIOM is OCBOUCTC
1
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NOTICE
This document has been reviewed in accordance with
U.S. Environmental Protection Agency policy and
approved for publication. Mention of trade names
or commercial products does not constitute endorse-
ment or recommendation for use.
ii
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FOREWORD
The U.S. Environmental Protection Agency was established as a focus of
scientific, governmental, and public efforts to improve the quality of the
environment. These efforts require expansion of our understanding of the
mechanisms that govern environmental changes and in particular those changes
that result from our own manipulations of the environment. One specific
thrust of these efforts must be the continuous developnient of more effective
and more efficient taethods for analyzing the environment and the changes
occurring in it.
One such project, which the Environmental Protection Agency is
supporting through its Environmental Research Laboratory in Duluth,
Minnesota, is the study "The Impacts of Coal-Fired Power Plants on the
Environment." The Columbia Generating Station, a coal-fired power plant
near Portage, Wis., has been ths focus of all field observations. This
interdisciplinary study, involving investigators and experiments from many
academic departments at the University of Wisconsin, is being carried out by
the Water Resources Center and Institute for Environmental Studies at the
University of Wisconsin-Madison. Several utilities and state agencies are
cooperating in the study: Wisconsin Power and Light Company, Madison Gas
and Electric Company, Wisconsin Public Service Corporation, Wisconsin Public
Service Commission, and Wisconsin Department of Natural Resources.
The results of a study undertaken to determine the effects of leakage
from the cooling pond on wetland vegetation are presented in this report.
The study included field inventory and classification of plant communities,
vegetttion monitoring, field and laboratory experiments to test hypotheses
regarding mechanisms controlling population changes, and assessment of field
and theoretical approaches. Results showed that changes in water levels and
water temperatures caused by seepage from the cooling pond led to
significant changes in wetland plant populations and communities within 1 yr
after the power plant began operating.
Norbert A. Jaworski
Director
Environmental Research Laboratory-Duluth
Duluth, Minnesota
iii
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ABSTitACT
This report presents the 1974 to 1977 results of a study undertaken on
the site of the Columbia Electric Generating Station to determine the
effects of leakage from the cooling lake on wetland vegetation. The study
Included four phases: Field inventory and classification of plant communi-
ties; vegetation monitoring; field and laboratory experiments to test
hypotheses regarding mechanisms controlling population changes; assessaent
of field and theoretical approaches. Results showed that changes in water
levels and water temperatures caused by seepage from the cooling lake led to
significant changes in wetland plant populations ar.d ccr^r/jnities within 1 yr
after the Columbia Station began operation. In general, dominant perennial
rhizomatous species of Car>ex decreased in density and distribution, hydro-
phytic species such as Typha latifolia increased, and annvi; species such as
Bidens azrnua and Pilea pumila, which had been insignifica . jr absent
before disturbance, increased markedly. Major shifts in dominance and
diversity patterns and .» continuing trend of decreasing vegetative cover
occurred from 1974 to 1.977. Open water and exposed mudflats replaced the
p:?viously closed and densely vegetated perennial plant communities over an
increasing portion of the study area. Annuals colonized some of the habitat
opened by the removal of perennial species, but large areas remained unvege-
tated. By 1977, 19^ of the quadrats sampled in the area of major impact had
no rooted vegetation. Another 2% contained only annual vegetation.
A predominant tren-1 of decreasing species diversity and richness was
reserved from 1974 to i''77. However, no uniform relationship was observed
Between diversity and Intensity of disturbance—neither species richness nor
distribution of their abundances. Disturbance did not sisply increase or
decrease diversity. Species richness, diversity, and equitability sotaetimes
varied independently. All of the diversity measures used decreased in most
cases, but increased in others, and frequently did both during the period
from 1974 to 1977 as the spatial distribution and intensity of disturbance
increased on the Columbia site. Caution is urged in interpreting diversity
data for wetlands, subject to human-induced alterations in the physical
environment.
Physiological and phenological data from laboratory and field experi-
ments related the response-of T. latifolia and C. lacitstris to altered
seasonal patterns of carbohydrate storage and shoot phenology Induced
primarily by groundwater temperatures out of phase with normal cycles of
plant growth. Results for C. lacustris and T. latifolia suggested that the
likelihood of predicting the response of dominant species to disturbance
would be enhanced by knowing the key characteristics of their life cycle.
The extreme sensitivity of C. lacustT*ie appeared to be a consequence of its
particular life history cycle and the timing, as well as the magnitude, of
the disturbance.
Recommendations for future research are made with respect to the
development of effective management and assessment tools for wetland plant.
communities.
iv
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CONTACTS
FOREWARD ii i
ABSTRACT iv
FIGURES vi
TABLES xi
I. Introduction 1
Scope of Study 1
Research Objectives 3
Study Site 5
2. Summary, Conclusions, and Recommendations 8
Summ.'i ry 8
Conclusions 9
Recommendations 11
3. Wetland Plant Population and Community Responses to
Altered Temperature and Flooding Patterns 13
Introduction 13
Methods 15
Results 16
Discussion and Conclusions 72
4. Seasonal Changes in Phenology and Carbohydrate Reserves
of Typha latif'olia and Carex lacustris Populations
Subject to Altered Temperature and Flooding Patterns 78
Introduction 78
Methods 79
Results 83
Discussion and Conclusions 112
REFERENCES 119
APPENDICES
A. Plant Community Data 128
B. Total Nonstructural Carbohydrate Content of Tt/pha
latifolia and Car-ex lacustris 133
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FIGURES
Page
Plant communities at th-a Columbia Station prior to
construction. 2
2 Aerial photograph of Columbia Station taken in 1971
showing area of meadow/raarsh to be used for generating
station, cooling pond, and dikes 6
3 Vegetation map showing distribution of wetland plant
communities in 1975 18
4 Study area showing configuration of groundwate:: flow
system before and after filling of the cooling pond 22
5 Groundwater discharge patterns in the wetlands 24
6 Water level fluctuation.1; in the wetland west of the
cooling pond before and after filling of the cooling
pond 25
7 Afcrial photograph of me;.dow/marsh showing open water
areas on 1 March 1976 26
8 Groundwater temperature variations in wells we&t of the
Columbia cooling pond 29
9 Changes in mean water depth before and after filling
of the cooling pond for six wetland plant communities
within the area of maj or impact •... 32
10 Changes in scan wster depth before and after filling of
the cooling pond for six wetland plant communities
within the entire sampling area 33
11 Mean groundwater temperature in the plant rooting zone
at the time of vegetation sampling for the area of
maj or impact 34
12 Mean groundwater temperature in the plant rooting zone
at the time of vegetation sampling for the entire area... 34
13 Depth of peat and marl deposits at the Columbia site 36
vi
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Number . Page
14 Typha latifclia. Chang-s from fall 1974 to fall 1977 in
mean number of .shoots per quadrat in five wetland plant
coraraunities in cbe area of major impact 42
15 Carex lacuetrie. Changes from fall 1974 to fall 1977
in mean number of shoots per quadrat within five
wetland plant communities in the area of major impact.... 43
16 Carex roetrata. Changes from fall 1974 to fall 1977
in mean number of shoots per quadrat within five wetland
plant communities in the area of major impact 44
17 Carex etricta.. Changes from fall 1974 to fall 1977 in
mean number of shoots *per quadrat within five wetland
plant communities in the area of major impact 46
18 CalamagroBti.8 aanadensie. Changes from fall 1974 to fall
1977 in mean number of shoots per quadrat within five
wetland plant i^oniaunities in the area of major impact.... 47
19 Sagittarid lat-i-folia. Changes from summer 1974 to
summer 1977 in mean number of shoots per quadrat within
five wetland plant communities in the area of major
impact 48
20 Epilobium colot
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Number fagc
2.6 Typha la.tifolia. Changes from fall 1974 to fal.l 1977 in
mean number of shoots per quadrat within fivo uvtland
plant communities for the entire sampling area 57
27 Calamagroetis canadensis. Changes from fall 1974 to fall
1977 in mean number of shoots per quadrat within five
wetland plant communities for the entire sampling area... 59
28 Sparganium eurycarpun:. Changes from fall 1974 to fall
1977 in mean number of shoots per qu»drat within five
wetland plant communities for the entire sampling area... 60
29 Lemna. minor'. Changes from fall 1974 co fall 1977 in
mean number of shoots per quadrat within five wetland
plant communities for the entire sampling area 61
30 Community measures before and following disturbance for
four wetland plant communities 66
31 Community measures before and following disturbance for
four wetland plant communities. Data presented are fall
data for the entire sampling area 67
32 Community measures before and following disturbance for
six wetland plant communities. Data presented are fall
data for the entire sampling area ; 68
33 Community measures before and following disturbance for
six wetland plant communities. Data presented are fall
data for the entire sampling area 69
34 Temperature patterns in the substrate and mean water
levels at control sites for Typha. latifolia and Carex
lacuetr-is 73
35 Changes in vegetative cover from 1974 to 1977 74
36 Temperature patterns in the substrate aiid mean water
levels for Typha latifolia sites 85
37 Seasonal changes in total nonstructural carbohydrates
for the Typha control site and Area 03 compared with
values reported by two other authors 87
38 Seasonal changes In total nonstructural carbohydrates
for the Typha control site and four other sites
compared with values reported by another author 88
viii
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Averag_ height of Typha. latifolia shoots at control and
four other sites 91
40 Seasonal changes in short densities for Typha latifolia.
at control and four otht-r sites .. 92
41 Typha latifolia shoots exhibiting chlorosis on 15
October 1977 at control and four other sites.... 94
42 Temperature patterns in the substrate and mean water
levels for Carex lacuetris sites %
43 Seasonal changes in percentage of total nonstructural
carbohydrates in above ground and below ground tissues
of Carex lacuetris 98
44 Seasonal changes in total nonstructural carbohydrates
In rhizomes of Carex lac-uetrie at r.ontrol and t hree
other sites 99
45 Seasonal changes in mean number of shoots/quadrat for
Carex lacustris at cont.rol and three other sites 103
46 Seasonal changes in average height of Carex lacuetrie
shoots at a control and three other sites 105
47 Seasonal changes in Carex lacustris shoots exhibiting
> 80% chlorosis 106
48 Number of Carex lacuetrie shoots exhibiting various
degrees of chlorosis for different size classes 107
49 The fall size-class structure of the Carex lacustris
population at Area 10 compared to the control site
populations (September 1977) 109
50 The fall size-class structure of the Carex lacuctris
population at Area 10 compared to the control site
populations (October 1977) 110
51 Expanding distributions of Typha latifolia between
1974 and 1977 113
52 Typha latifolia in 1977 invading areas of the Columbia
marsh which Carex previously dominated 114
53 Decline of Carex laeuetrie population in Area 01
between April 1976 and April 1978 115
Ix
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Number . Page
54 Areas of open water and exposed mudflats that have
replaced the closed and densely vegetated perennial
plant communities 117
B-l Total nonstructural carbohydrates in rhizomes, shoots,
and shoot bases of Typha latifolia at control and four
other sites 134
B-2 Means and standard deviations for percent total
nonstructural carbohydrates in rhizomes and shoot bases
of Carex lacustr>i(s at three sites and a control U5
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TABLES
Number Page
1 Plant Species Composition, Absolute Density, and
Relative Density for Six Plant Communities 20
2 Chemical Characteristics of Water at the Columbia Site... 28
3 Sample Numbers for the Full Data Set and Uniform
Random Subsets for Each Community and Sampling Period.... 64
A Location and CharactersiUics of Sampling Sites 82
A-l Summer Data for Four Plant Communities Before and
Following Disturbance for Area of Major Impact 129
A-2 Fall Data for Four Plant Communities Before and
Following Disturbar ce for Area of Major Imoact 130
A-3 Summer Data for Fivi> Plant Communities Before and
Following Disturbance for Entire Area 131
A-4 Fall Data for Six Plant Communities Before and
Following Disturbance for Entire Area.... 132
xi
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SECTION 1
INTRODUCTION
SCOPE OF STUDY
Research on wetland plant responses was—like other studies—carried
out at the Columbia Electric Generating Station site, conducted as part of a
larger program designed to evaluate environmental changes brought about by
construction and operation of the 1100 MW facility. The research objectives
of the program as a whole were formulated in 1970 in the context of
Wisconsin's recent Shoreline Zoning Act (1965), imminent passage of the
Wisconsin Environmental Policy Act (1971), and a long history of protection
of navigable waters under the Public Trust Doctrine of the State
Constitution. Regulatory responsibilities established under these
legislative and constitutional mandates required evaluations, in advance, of
the prospective effects of the proposed development. The Columbia study,
undertaken initially with support from the three Wisconsin utilities
building the power plant (Wisconsin Power and Light Co., Madison Gas and
Electric Co., and the Wisconsin Public Service Corp.), was intended to
provide information for government and industry in future environmental
protection decisions involving coal-fired steam electric plants,' Additional
support provided by the U.S. Environmental Protection Agency (U.S. EPA)
permitted the study r.o expand between 1975 and the present to take advantage
of the baseline studies and obtain more definitive answers to a wide range
of questions on environmental effects.
The project was a unique opportunity to examine fundamental ecological
questions about the response of wetland ecosystems to the external
influences of nearby development. The Columbia station and its associated
facilities which were under construction in 1971 at the time the study was
initiated, were located adjacent to and in the floodplain of the Wisconsin
River. Most (81.9%) of the 1900-ha site in its pre-construct.ion state was
wetland (Figure 1). Almost 50% of the site was an extensive raarsh—sedge
meadow (31%) or emergent aquatic vegetation (17%)—considered to be
important as walleye and northern pike spawning habitats. These areas
represented a major portion of tne nonwooded wetlands remaining on the
Wisconsin River in Columbia County.
The 200-ha cooling lake built for the generating station was sited in
the marsh. The utilities and the project research staff predicted that the
lake would leak substantial amounts of warm water. Although thf. effect of
the leakage on the remaining marsh was not examined fully during pre-
construction evaluation, it became a major question during later assessment
of environmental effects from the Columbia power station development.
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e irteadcw
Wet for»»t
Dry toraal
Sampling Araa
Basin
iP
rMBlnCenaritlng Unita
\
Figure 1. Plant communities at the Columbia Station prior to
construction.
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The wetland pla;it ecology study in the Columbia project was undertaken
In 1974 to monitor vegetation changes associated with leakage from the
cooling lake. Although it was known that the remaining wetlands would be
affected by elevated groundwater levels and temperature increases due to
leakage from the cooling lake, uncertainty existed regarding the nature and
probable timing of the changes. Neither the type, magnitude, nor rate of
change was predictable at tha time. Using the existing paradigms for
ecosystem response, potential effects considered by the 1973 Wisconsin
Department of Natural Resources (WDNR) Environmental. Impact Statement ranged
from gradual decrease of intolerant species, increase of early-blooming
plants, and decreased diversity to disrupted competitive interactions,
changed rates of succession, and shifts to vegetation types—e.g., cattail—
unsuitable for spawning habitat. In response to concern by the U.S. EPA,
the National Marine Fisheries Service, the Bureau of Sport Fisheries and
Wildlife, and the WDNR about effects on the marsh, the Army Corps of
Engineers predicted no significant effect on the marsh vegetation, and the
environmental assessment was left in that form (Depprtment of the Army, St.
R»ul District Corps of Engineers 1974).
RESEARCH OBJECTIVES
The principal objective of the wetland vegetation study was to
determine how the wetland plant communities west of the cooling lake (Figure
1) might change in response to mild heat and water stress which required
answers to five basic questions:
1,. What types of change would occur? Would changes occur at the level
of species response:! only, or would the marsh community change in
unique ways? Would the composition or structure of the vegetation
change?
2. What would be the magnitude of change? Would changes be within the
range of natural variability In wetland eco-systens? How large an
area would be affrcted?
3. At what rate would changes occur? Would the changes be gradual, or
would they occur over a short tine-frame and be more noticeable to
observers?
4, WouJ.rt a new equilibrium community become established or might the
vegetation continue to change Almost as long as the stress was
continued? ;
5. Would changes be irreversible or might the communities recover
following a period of complete abatement?
Wetland vegetation is dynamic, and methods for determining vegetation
response to waste heat and elevated groundwater levels are not widely agreed
upon. Wetlands in the upper midwest sometimes undergo natural shifts in
specie* composition and structure without being subject to anthropogenic
environmental influences (Bedford et al. 1974, Van der Valk and Davis 1978,
Weller and Fredrickson 1974). Thus, the study had to examine whether
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changes indi'^ed jy cooling lake leakage could be detected in the limits of
existing field monitoring techniques. Furthermore, it was necessary to
determine whether the theoretical pardigms for analysis provided criteria by
which significant impact could be recognized.
The principal research objectives had to gc beyond documenting
resultant changes in wetland plant communities to an understanding of the
process of change itself. The research goals designed to address the above
questions, therefore, were aggregated into three broad categories:
1. Documenting the response of wetland plant species and communities
to mild heat and water stress.
2. Determining causal mechanisms potentially relating vegetation
changes to environmental variables that—in turn—could be related
to leakage from the cooling lake.
3. Examining available field techniques and paradigms for recognizing,
monitoring, and—if possible—projecting the probable --ffects of
waste heat and elevated water levels on wetland vegetation.
These objectives—in summary—represent a program designed to document
the change, establish the cause, and—in the process—improve asse' ••ment
capabilities anc' theoretical understanding of the responses of frt^.iwater
wetland plant communities when placed under stress
At the same time, the wetland plant ecology study was undertaken in
close cooperation with related research. Concerns with efficient assessment
techniques, and the relative difficulty of wetland field work, led to the
development of a separate subproject in the Columbia study to explore the
integrated use of ecological and remote sensing methods in freshwater
wetlands.
The wetland plant ecology research included four phases, .lamely, field
inventory and classification of plant communities, vegetation monitoring,
field and laboratory experiments to test hypotheses regarding raechanmisms
regulating population changes, and assessment of field and theoretical
approaches. Field surveys, species lists, and air photographs were used in
the initital phases of the study to inventory, classify, and nap the plant
communities of the site. Fhytosociologicai methods have been used since
197A to monitor plant population changes and species composition. Field and
laboratory experiments began in 1977, following intensive field studies
during 1976. Measurements were made of changes in plant phenology and
associated changes in amounts of carbohydrates stored in underground organs
of two species of perennial plants. These measurements were used both to
test hypotheses regarding mechanisms controlling population responses and to
identify ecologically-based criteria by which significant impact on the
wetland plant communities could be recognized and monitored in the field at
the species level.
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STUDY SITE
The study was conducted In non-forested freshwater wetlands lying
Immediately west of the cooling lake of the Columbia Electric Generating
Station. The station is located in southcentral Wisconsin 6.4 km (4 miles)
south of Fbrtage (43° 33' N, 89° 27' W) on a 1900-ha site which is almost
entirely in the floodplain of the Wisconsin River. Prior to construction,
an extensive and diverse wetland system covered = 80% of 1100 ha on the site
declared for utility purposes. Dominant vegetation types in the wetland
system included marsh (emergent aquatics and southern sedge meadow),
southern lowL nd forest, and lowland shrub communities (Curtis 1959,
Wisconsin DNR 1973). In 1971, more than 50% of the area was classed as non-
forested wetiand: sedge meadow - 31% (340 ha), emergent aquatics - 17% (183
ha), and lowland shrub communities - 2% (22 ha) (Wisconsin DNR 1973).
Approximately 200 ha of this were filled for the construction of dikes or
flooded for the cooling lake of the generating station (Figure 2). The non-
forested wetlands remaining west of the cooling lake, between it. and the
lowland forest bordering the Wisconsin River, were oelected for study.
Tha Columbia station consists of two 527-MW coal-fired electric power
generating uniis, a 200 ha cooling lake, 28 ha ashpit, 16 ha coal pile, and
other associated facilities. Construction began in 1971. Rimping to fill
the cooling lake first began 13 June 1974 and ceased on 17 July 1974. The
lake was almost empty due to high ler.kage rates by 1 September 1974.
Riraping resumed 4 November 1974 after the dikes were sealed with
bentonite. By 2 January 1975 the lake was full. Operation o:: the first
unit began in May 1975. The second unit did not begin operation until
spring 1978 (Andrews and Anderson 1980).
Data collection for this study began in June 1974 and continues to the
present. Some preliminary studies of wetland vegetation on the site were
carried out from 1971 to 1973 by Samuelson (1972). Studies of the
groundwater system and surface flows on the site began in 1972.
The wetlands on the Columbia sii.w are located in a regional groundwater
discharge area and occupy a former channel of the Wisconsin River. A layer
of peat varying in thickness from 1 to 3 m overlies a thin layer of organic
clay and silt underlain by alluvial sands with clay lenses. Bedrock
composed of Upper Cambrian sandstones and Pre-Cambrian granites occur at a
depth of 125 IB below the surface (Andrews 1978b).
Prior to filling the cooling lake, groundwater discharge,
precipitation, and floodwaters supplied water to the extensive wetland
communities on the site. Precipitation was the most important source,
providing =< 76 cm/yr. Groundwater inflow averaged = 22 cra/yr. Floodwaters
from the Wisconsin River and Duck Creek frequently inundated the site,
usually in early spring. However, their residence time in the wetlands was
short « 3 days) due to the gentle slope of the area toward the Wisconsin
River. Other surface water inflows were minor (Stephenson and Andrews
1976).
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Figure 2. Aerial photograph of Columbia Station taken in 1971 showing area of meadow/marsh to be
used for generating station, cooling pond, and dikes. Sampling area is above and
immediately to the right of the dike shown intersecting the upper right-hand corner cf
the photograph.
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Wetland surface water levels fluctuated widely prior to lake filling.
Generally, levels were high during spring floods, decreased in summer,
frequently to levels below the soil surface, and rose again in the fall as
plant growth and evapotranspiration ceased (Stephenson and Andrews 1976).
The climate in the vicinity of the site is continental. Weather is
seasonally variable with a large annual temperature range. Winters are cold
and summers ate warm. Mean annual temperature is 6.5°C (0.89 s.d.) with a
mean sumroar maximum of 25.7°C (0.94 s.d.). Mean maximum temperature for
winter is -3.3°C (1.78 s.d.) with a minimum mean of -12.9°C (2.06 s.d.)
(Wang and Suomi 1958). The first killing frost is likely to occur around 30
September and the last around 1 May. Normal daily average monthly
temperatures near ft>rtage are: January, -7.78°C; May, 14.45°C; July,
22.78°C; and October, 9.45°C (Wang and Suomi 1957 and 1958). Average annual
precipitation is ^ 76 CM, with somewhat more than 50% of it falling between
May and September.
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SECTION 2
SUMMARY, CONCLUSIONS, AND RECOMMENDATIONS
SUMMARY
The environmental Impact statement for the Columbia Electric Generating
Station (Department of the Army, St. Paul District Corps of Engineers 1974)
raised but did not answer the question of significant change occurring in
wetland plant communities on the site as a result of leakage from the
cooling lake. This report presents the results of a study undertaken on the
site from 1974 to 1977 to determine the effects of leakage on wetland
vegetation. The study included four phases: 1. Field inventory and
classification of plant communities, 2. vegetation monitoring, 3. field and
laboratory experiments to test hypotheses regarding mechanisms controlling
population changes, and 4. assessment of field and theoretical approaches.
Field surveys, species lists, and air photographs were used in the initial
phases of the Columbia Study to inventory, classify, and map the plant
communities of the site. Phytosociological methods have been used since
1974 to monitor changes in plant populations and community structure. Field
and laboratory experiments began in 1977, following intensive field studies
during 1976. Measurements were made of alterations in plant phenology and
associated changes in amounts of non-structural carbohydrates stored in
underground organs of two species of perennial plants. These measurements
were used to test hypotheses regarding the causes of population decline and
to identify ecologically based criteria by which significant impact on the
wetland plant communities could be recognized and monitored in the field at
the species level. .
The scope of the study, research objectives, and description of the
study site are summarized in Section 1. Results of the first two phases of
the work covering changes in wetland plant populations and community
structure ure presented in Section 3. Section 4 reports the results of
field and laboratory measurements of changes in plant phenology and patterns
of carbohydrate storage. It identifies field signs of heat stress and
suggests general species characteristics that may be useful indicators of
potential sensitivity to stress. Initial assessment of field techniques and
paradigms of analysis that might improve assessment capabilities and
theoretical, understanding of the responses of wetland vegetation to
anthropogenic disturbance are discussed in Sections 3 and 4.
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COHCLUSIO'iS
Results of data collected from 1974 to 1977 showed that changes In
water levels and water tenperatur;? caused by seepage from the cooling lake
led to significant changes in the plant populations and communities.
Plant popular.'on data showed that species were not equally sensitive to
flooding, heat stress, or increased surface water flow. Sone species, e.g.,
Car>ex lacustrie and C. r>ostt\ita, wore extremely sensitive, declining rapidly
and dramatically In all communities. Other perennial species, e.g., C.
stricta and Calamagroetis canadeneis, responded more slowly, decreasing only
after 1976. Typ'na latifolia, on the other hand, increased continuously in
the EMERGENT community and invaded all other communities. Other hydrophytic
but non-persistent species, e.g., Sagittaria latifolia, increased in some
communities. Lervia m'-nor, a floating annual, increased dramatically in
expanding areas of open water. Annual species, e.g., Bidens cernua and
Piled pumila, which had been insignificant or absent before disturbance,
Increased markedly where perennial dominants declined.
Results of community level measure of vetland response to leakage from
the Columbia cooling lake showed significant changes occurring In the struc-
ture of the plant communities. In addition to major shifts in dominance and
diversity patterns in each plant community, a continuing trend of decreasing
vegetative cover occurred in the Columbia wetlands frora \974 to 1977. Open
water and exposed mudflats replaced the previously close-i and densely
vegetated perennial plant communities over an increasing, portion of the
study area. Annuals colonized SOUK of the habitat opened by the removal of
perennial species, but large areai remained unvegetated. By 1977, 192 of
the quadrats sampled in the area •: f major impact had no rooted vegetation.
Another 2% contained only annual vegetation.
The magnitude of effect produced at both the population and community
levels appears to be outside the range of natural variability for this
particular wetlar.d. Shifts toward more hydrophytic species and decreasing
vegetative cover are not uncommon for some wetland systems (Van der Valk and
Davis 1976), but evidence for the Columbia site suggests that the 1974
vegetation represented a fairly long-lived community type under historically
existing environmental conditions. The data from this study are limited
since they contain only 1 yr of pre-impact measures. However, early survey-
ors' (1830's) records (Tans 1976), soil cores, well-developed C. etricta
tussocks (Costeilo 1936), long-term flooding patterns on the Wisconsin River
(Department of the At ray, Chicago District Corps of Engineers 19721, 1949 air
photographs, and early description indicate that densely vegetated perennial
wetland plant communities probably have occupied the site for at least the
last century.
Water level changes significantly affected ^ 75% of the study area by
1977. The area significantly affected by waste heat is more difficult to
define. The physiological and phenological data for C* lacustr>is and T.
latifolia showed adverse effects from waste heat occurring within 100 tn of
the wet dike in 1977 and apparent subsidy effects on Typha at distances up
to 300 m from the dike. .
-------
Vegetation changes on the Columbia site occurred almost Immediately.
Changes were obvious and evident In the field at community and population
levels within 1 yr after t'.ie station began operation in spring 1975.
Effects of flooding were seen In the summer 1975 data. Late flowering and
delayed dieback of individual plants occuired in localized areas near the
dike In fall 1975. Major phonological changes were evident within 100 ra of
the dike by spring 1976. Significant changes in population density and
community structure occurred in all communities by summer 1976.
A predominant trend of decreasing species richness and diversity was
observed from 1974 to 1977. However, no uniform relationship existed
between diversity and intensity of disturbance—neither species richness nor
distribution of their abundances. Although obvious changes in community
structure took place from 1974 to 1977, the •scologlcal signficance of
different community patterns of response was not evident from the diversity
data alone. Disturbance did not simply Increase or decrease diversity.
Species richness, diversity, and equitability sometimes varied indepen-
dently. All of the diversity measures used decreased in most cas^s, but
increased in others, and frequently did both during the period from 1974 to
1977 as the spatial distribution and intensity of disturbance increased on
the Columbia site. Differences observed between communities in diversity
measures were related to the differential sensitivity of spatially dominant
species to disturbance. Where disturbance was of the type to which dominant
species were sensitive, diversity and equitability increased as new or
competitively inferior species colonized or spread to space made available
by the decline of previously dominant populations. Diversity and equita-
bt.lity decreased where disturbance favored one or two dominant species.
C. lacustris exhibited much greater sensitivity to stress than T.
lavifolia. Population data showed an almost uniformly negative response by
C» lacuetris, but both positive and negative responses by 7". latifolia-
Typha exhibited a clear positive response to elevated water levels, increas-
ing Its density where it had been abundant and expanding its distribution
substantially by 1977. Adverse effects on Typha. were restricted to limited
areas where temperature increases were > 7 to 16°C and occurred in winter.
Viable populations of C* lacustris persisted only in areas where temperature
increases were negligible throughout the year.
Physiological and phenological data from laboratory and field experi-
ments related the response of T. latifolia and C* lacuetrie to altered
seasonal patterns of carbohydrate storage and shoot phenology induced
primarily by groundwater temperatures out of phase with normal cycles of
plant growth. In addition to establishing the causal mechanism relating
vegetation changes to leakage from the cooling lake, this data set identi-
fied field signs of heat stress and suggested general species characterise
tics that may be useful indicators of potential sensitivity to stress.
Phenological changes appear to be reliable indicators of heat stress.
Although changes in population density occurred throughout the study area,
obvious phenological changes were not observed outside the area affected by
altered temperature patterns. In areas receiving waste heat, individual
10
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plants showed visible signs of stress before Ltie population collapsed.
Where the species grew in dense stands, the symptoms were visible to the
naked eye at. distances up to 300 m. In general, phenologies! changes became
evident 1 yr before population density was reduced and 2 yr before r.he
population collapsed.
Characteristics of plants ^>:periencing heat stress that were observable
and easily measured in the field included: 1. Unseasonable chlorosis,
2. reduced height of mature shoots, 3. increased height of new spring and
fall shoots, and 4. early or delayed shoot emergence at reduced density.
RECOMMENDATIONS
The concept of life history strategy warrants further consideration as
a theoretical tool for predicting species sensitivity to disturbance and
assessing the probable effects on wetland plant communities. The physiolog-
ical and phenological data for C. lacustr>is and 7*. latifclia suggested that
the likelihood of predicting the response of dominant species would be
enhanced by knowing the key characteristics of its life cycle. The extreme
sensitivity of C* la.custr>ie appeared to be a consequence of its particular
life history cycle and the timing, as well as the magnitude, of the distur-
bance. Species characteristics that may serve as useful indicators of
potential sensitivity to stress include life span, the seasonal schedule of
various phenophases, seasonal distribution of bioiaass between above- and
below-ground parts, ability to regenerate or colonize, and reproduction and
mortality schedules.
Research should be continvied on the Columbia site in order to -.ake
advantage of the long-term (1974 to present) data base and i-onitor !:he
eventual outcome of a sustained perturbation on wetland vegetation. The
1974 to 1977 data address but cannot answer tV/e questions regarding estab-
lishment of an equilibrium community cr recovery following disturbance.
Examination of temporal patterns in both the population and community data
reveals that the Columbia wetlands are still in a phase of transient
behavior that should continue to be monitored. Further changes can be
expected at both the population and community levels. In terns of environ-
mental factors, the Columbia wetlands are only 33% through a predicted
transient. Although water levels have more or less stabilized, temperatures
are expected to increase in magnitude and spatial extent after 1978 as the
heat load of the second Columbia unit is added to the cooling lake (Andrews
1973b). The results'of 1974 to 1977 population data and 1977 physiological
data for the Columbia site indicate that dominant perennial populations of
rhizomatous sedges and grasses will continue to decline. As they do, the
structure of the community will continue to change. In areas subject to
minimal temperature increases tolerant hydrophytic species such as T.
latifolia probably will become dominant. Areas subject to maximum tempera-
cure increase may support only annual vegetation or remain as unvegetated
exposed muck or open water.
Future research should address the system-level consequence of change
in the vegetative component* The development of effective management and
assessment tools depends on the identification and understanding of critical
11
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system components and Interactions. Field observations on the Columbia site
Indicate that increased credibility of tlie peat mass may be associated with
the transition in doninanlis from perennial to annual and from persistent to
non-persistent species. Changes in species numbers and diversity values
appear to be less relevant than changes in the life history characteristics
of spatially dominant species. Further research should address the problem
of identifying appropriate analytical categories and the components and
processes of wetland systems critical to effective environmental impact
assessment. The data from this study suggest that grouping speciec with
similar sets of life history traits may identify meaningful aggregate vari-
ables between the level of the i-idividual plant species and the community.
Activities which alter physical inputs to wetlands are likely to con-
tinue to occur as the result of energy-related developments. More effective
tools and paradigms of analysis for predicting short- and long-term effects
of environmental changes on wetland plant communities are more likely to
come from research based on demographic principles than on existing commu-
nity theories of succession or diversity. Studies on the Columbia site
showed no evidence of the community by community replacements predicted by
the succession model and no fixed relationship between disturbance and
diversity measures. Future research should include studies of: 1. The
population biology of important wetland species includi-.g temporal life
history characteristics, seasonal changes in population age/size structure,
and germination requirements [Bernard and (lorhar, (19715) Van der Valk and
Davis (1976a, 1978) have already undertaken studies in ihis area); the
relationship between population characteristics and the type, severity, and
periodicity of naturally occurring fluctuations in the physical environment;
and 3. the relationship of life history characteristics to the probability
of extinction and to the cspacit/ to regenerate or recoionize under human-
induced fluctuations in the physical environment.
12
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SECTION 3
WETLAND PLANT POPULATION AND COMMUNITY RESPONSES
TO ALTERED TEMPERATURE AND FLOODING PATTERNS
INTRODUCTION
Research Objectives
The wetland plant ecology study of the Columbia Project was undertaken
in 1974 to monitor vegetation changes associated with leakage from the
cooling lake (Green 197'J, cf. Cairns 1980). Although it was known when the
study began that the sedge meadow and shallow marsh west of the lake would
be affected by elevated groundwater levels and temperature increases caused
by leakage, uncertainty existed regarding the nature and probable timing of
t'.ie environmental and vegetation changes expected. The principal objective
of the wetland research was to determine how wetland plant populations and
communities might change in response to heat arid water stress.
Hypothesis
It was hypothesized that changes in water levels and water temperature
caused by seepage from the cooling lake would lead to significant changes in
vetland plant populations and communities. In the framework of this general
hypothesis, five basic questions were examined during the monitoring
program. These are stated in section 1.
Two factors constrained more specific formulation of hypotheses end
sampling design: 1. The spatial scale, temporal distribution, and
magnitude of the expected environmental changes were not known when sampling
began, 2. empirical evidence and theoretical understanding of the effects of
exogeneous disturbances on wetland vegetation dynamics were limited. A
general trend from sedge meadow and shallow marsh species coward more
hydrophytic species could be expected for the Columbia stte if water levels
increased sufficiently. The critical relationship between wetland
vegetation and the frequency, range, and duration of water level
fluctuations seasonally and from year to year has been well established
(Kadlec 1962, Harris and Marshall 1963, Sculthorpe 1967, Walker and Wehrhahn
1971, Auclair et al. 1973, Weller and Fredrickson 1974, Van der Valk and
Davis 1976b and I978b, Gosselink and Turner 1978). However, since the
magnitude of the increase was not known and the elevation of the meadow and
marsh covered a range of more than 60 cm, the magnitude and rate of change
in the vegetation and the size of the area that might be affected by water
level changes could not be predicted. The effects of waste heat on aquatic
systems also have been studied extensively (Krenkel and Parker 1969,
13
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Coutant 1973, Gibbons and Sharitz 1974a and 1974b). However, at the time
this research was Initiated, few studies had addressed the question of
thermal effects on vascular aquatic plants (Anderson 1969, Wood and Zleraan
1969, Sharltz et al. 1974, Youn£. 1974). No studies existed on northern
freshwater wetland plant populations or communities. Furthermore, neither
the magnitude, temporal patternn, or spatial extent of temperature changes
on the site was known. Small Increases in temperature might act as a
subsidy rather than a stress on the system (Oduo 1974, Gibbons 1976, Odura
et al. 1979).
The monitoring program on the Columbia site provided a unique
opportunity to examine some fundamental empirical and theoretical questions
about the response of wetland plant populations and communities to exogenous
disturbances. The principal theoretical paradigms regarding vegetation
change in wetlands, succession, and diversity theory were questioned,
especially with respect to environmental impact assessment. Several authors
have suggested that the concepts of static stability ar.d diversity generally
associated with classical succession theory (Clements 1916, Tansley 1939)
are of limited use in interpreting or predicting the effects of
anthropogenic disturbance on ecosystems (Loucks 1970, Kolllng 1973, Botkin
and Sobel 1975, Green 1979). Although diversity measures are widely used
among environmental biologists (Cairns 1974, Weber 197i, States et al. 1978,
Darnell et al. 1976), little agreement could be found on their meaning or
relationship to successional status or response to disturbance (Goodman
1975). The general succession tiodel was criticized (Drury and Nisbet 1971
and 1973, Horn 1974) and its validity in terns of controlling factors,
predicted sequence, direction, tind rates of change for wetlands in
particular was questioned (Welle- and Spatcher 1965, Walker 1970, Heinselman
1970, Van der Valk and Bliss 1971, Weller and Fredrickson 1974, Bedford
et al. 1974). The limited empirical evidence available for wetland systems
does not support the presumed relationship between diversity and
disturbance, either naturally-occurring (Van der Valk arid Bliss 1971, Van
der Valk and Davis 1976b) or anthropogenic (Sharitz et al. 1974). The types
of vegetation changes predicted by the succession model are those regulated
by autogenic processes taking place in the system as a result of species
interactions under equilibrium conditions. Response to disturbance is
regarded as a function of community complexity and stability, seen as
increasing together with "advance" in successional stage, and measured as
species diversity (Odum 1969, Margalef 1968, Caswell 1976). The types of
vegetation changes which were of concern in this study were those that might
be caused by external influences. They would occur under non-equilibrium
conditions and would likely reflect individual species-environment
relationships as well as biotic Interactions and community processes.
Reported herein are changes observed in wetland plant populations and.
community characteristics at the Columbia site from 1974 to 1977 together
with the relationship between the response of dominant species and changing
diversity patterns.
-------
METHODS
Vegetation Sampling
Changes in species occurrence and plant, community composition and
structure were monitored semiannually from 1974 to 1977, by identification
and stem counts of all plant species in 0.25 n" quadrats. Quadrats were
located by reference to a regular 50 x 50 n grid system laid out within
well-defined sedge meadow/marsh boundaries. In 1974, permanent station
markers were placed at 50 m intervals along 40 linear transects running
approximately perpendicular to the west dike of the cooling lake. In 1976,
transects and stakes were added at 25 ra intervals between transects 18 and
28 to intensify sampling in areas of apparent rnajor eisviroKsicntal change.
For each sampling period, counts were taken in quadrats placed 1 or 2 ra from
the permanent stake in a random choice of two of the four directional quad-
rants. The stake narked the intersection of the quadrant boundaries.
Stations were sampled during summer and fall of each year from 1974 to
1977. In each quadrat, plant species were identified and counted as number
of steus or culras. Counts of Lerxna rrrinor were recorded as absent (0),
sparse (25), moderate (50), or dense (73). Exceptions to the general
sampling procedure are: In 1975 and fall 1976 only the presence or absence
of species were recorded for "v 33£ of the total sanple. Only transects 18
to 30 were sampled in summer 1976 and 1977. From summer 1976 through fall
1977 the sampling Interval for environmental factors between transects 18
and 28 was based on a 25 x 25 m grid rather than a 50 x 50 m grid. Frequent
field observations, ground photographs, color air photographs, and color
infrared air photographs (Wynn and Kiefer 1977) were used to supplement
field-measures.
Plant nomenclature follows Gray's Manual (Fernald 1950). Species
present in the study area are enumerated in Kiefer et al. (1976). Plant
specimens were deposited in the University of Wisconsin Herbarium for
verification.
Mapping
Two vegetation maps were prepared using conventional air photograph
interpretation and field data. The base map was a 1974 photographic map of
the site, prepared and corrected by the Wisconsin Department of Transporta-
tion- to a topographic map with 2-ft contour intervals. Air photographs from
1975 and 1977 were projected onto the base nap and corrected to cultural
features. Vegetation patterns visible on the air photographs were outlined
and identified by a combination of field checks and references to sampling
data.
The naps represent the distribution of visually prominent assemblages
(Curtis 1959) of plant species. Boundaries are necessarily arbitrary and
shift with seasons (Buchanon and Scarpace 1980); the communities intergrade
with each other. Visually distinct communities may or may not be ecolog-
ically significant (Greig-Smith 1964).
15
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Environmental Factors
Changes in environmental factors prevailing, in the meadow/taarsh west of
the Columbia cooling lake were studied in two subprojects of the Columbia
Study: The Hydrogeology Group assessed alterations in three parameters of
the groundwater system: 1. The. quantity of groundwater flow into the
wetland and the surface water levels iu the wetland, 2. the temperatures of
groundwater.and surface water, and 3. the quality of groundwater and surface
water as expressed by concentrations of commonly occurring anions and
cations. Field data were used to develop and test models to sirailate
groundater flow before and after filling the cooling lake and long-term
seasonal temperature patterns in the wetland west of the cooling lake
(Andrews 1976, Stephenson and Andrews 1976, Andrews and Anderson 1978,
Andrews 1978a, 1978b, and 1980).
The Wetland Plant Ecology Group collected data on water depths,
substrate temperatures, and surface water temperatures in each quadrat
during semi-annual vegetation samplings. Two water depths were recorded:
1. Depth t<> plant rooting zone, measured as the distance between water
surface and the top of the soil surface in which plants were rooted, and
2. depth to solid subctate, measured as the distance between water surface
and the top of the substrate capable of supporting the recorder's weight.
Data measures were taken with a wooden meter stick marked to 0.1 era.
Substrate temperatures were measured % 15 cm below the soil surface in which
plants were rooted, i.e., in the plant rooting zone. Surface water
temperatures were recorded at 15 cm below the water surface or just above
the soil surface if water depth was < 15 cm. Temperatures were measured
using a glass-mercury thermometer or a Reotemp Inc. 60-cra raeta'.. probe
thermometer.
RESULTS
Plant Communities Prior to Disturbance
Prior to significant environmental change, the study area consisted of
three basic vegetation types: 1. Sedge meadow, 2. emergent aquatic or
shallow marsh, and 3. lowland shrubs (Curtis 1959, Wisconsin Department of
Natural Resources 1973). The sedge meadow category included two areas
distinguished on the basis of the prominence of well-developed tussocks of
Carex etr*ieta or dense stands of Car>ex lacustr^ie. The area of emergent
aquatic vegetation was distinguished by t'.;e prominence of Typha latifolia or
Scirpue fluviatilie in the canopy. A transition community between distinct
sedge meadow and emergent aquatic zones contained understory species from
the emergent aquatic zone and prominent overstory species from the sedge
meadow zone. Areas of lowland shrubs were characterized by the prominence
of Spiraea alba with understory species closely resembling the sedge meadow
areas, especially the <7. etricta dominated meadow, or by a mix of shrubs
(Salix spp. and Cornue etolonifera) with lowland trees. Thus, six visually
distinctive plant conmunities were defined.
16
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Mapping was used to define approximately the broad spatial distribution
of the six plant connunities. Sampling data were used to characterize the
species composition and structure of each community. The map of 1975
vegetation patterns is shown in Figure 3. Note that In addition to the six
basic plant communities, areas obviously dominated by Calamagrostie
canadeneie, Scirpue fluviatilie, or Sparganium eurycarpum are mapped
separately. The latter two, along with open water areas, are combined with
the emergent aquatic community for data analysis. The C. canadeneis areas
are considered part of the C, etricta community. The map also separates
shrub areas consisting of a mix of Salix spp. and C. etolonifera with some
S. alba from similar shrub areas which also contain lowland trees such as
Topulus deltoideo, Ulmua americana, Betula nigra, Ajer eaccharinum, and
Populus tremuloidee. For data analysis the two are pooled. Because of the
small size of the quadrats (0.25 m"), the species sanpled largely reflect
the understory composition of shrub and tree <_oramunites.
For purposes of data analysis, each sampling station in the grU system
was assigned to one of the six communities. Assignment was based on
vegetation patterns and shown or. the 1975 map and on field data. If a
station fell within a locally abundant patch of C, lactstrie within a
largely C. Btricta area, it was assigned to the CAREX STRICTA community.
The six plant communities are defined as follows:
1. The CAREX LAUSTRIS community consists of areas with dense stands of
C. lacustrie visually prominent in the canopy, with C1. stricta, C.
canadeneis, and Sagittaria latifolia locally abundant.
2. The CAREX STRICTA community is made up of areas with numerous well-
developed tussocks of i'. etricta or C. canadeneie visually
prominent In the canop> , mixed with other sedj'.es, grasses, forbs,
and ferns. C. canadenvis, C. lacustriB, S. latifolia, and Spartina
pectinata were locally abundant. For purposes of data analysis,
areas mapped as prominant C* aanadensie areas are pooled with this
group.
3. The EMERGENT community is dominated by tall, robust, emergent
aquatic vegetation, such as T. latifolia, Scirpue fluviatilie, and
5. eurycarpum. Carex wet-rata, C. lacuetrie, S. latifolia, and
Accrue calamus are locally abundant.
4. The TRANSITION community is a mixed transition zone between
distinct sedge meadow and emergent aquatic plant assemblages. C.
roetrvttaf C. canadeneie, C. lacustrie, C. etriota, and S. latifolia
are locally abundant.
5. The SPIRAEA community occupies areas with the shrub. Spiraea alba,
prominent in the overstory, and with an understory similar to, but
less dense than, CAREX STRICTA areas.
17
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Rtver Floodpljin Forest
40 39 M 37 36 35 3t 33
31 30 29 28 27 ?6 ?5 24 23
D •*'"" r-~ ' f CS?Fz~~ ^- i X"1"* \i v*"*^7-> - •* ^-^"rT^/^i "
.-"I vr-ii-1 xtr--")•/ T-ll '«^"->-\\-IT J -
- -c 1^/i^m- M*^^11: ^^
• I a ~~"* • J^T" "t^— *~fr~ **• H "i * v-Cj •* I-1-!1'— ~ i™
I- wz. -.' \f yl_ " IT—i C.X"" p ' * ^ • -*f BirVV1"-. ^ *• 4 ** j<"
/ v. - * »v
22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 765432 1
West Dike
Cooling Pond
Figure 3. Vegetation map showing distribution of wetland plant
communities in 1975.
18
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6. The MIXED SHRUBS and LOWLAND TREES community comprises tvjo areas,
namely, areas with mixed shrub species (Salix spp. and (?,.
etolinfera with some S. alba) prominent in the overstory, and areas
of mixed shrubs containing scattered lowland trees such as P.
deltoidee, U» americana., B. nigra, A. sacakarinum, and P.
tremuloides.
Areas disturbed by construction activity were mapped but not analyzed.
The six plant communities actually represent a single complex of
wetland plant communities which form a continuu-n (Gleason 1939, Curtis 1959)
of intergrading types. Many of the major species are distributed throughout
the area with all of the communities sharing numerous species. They can be
distinguished on the basis of physiognomy (shrubs, tall robust eraexgents,
non-sedge/grass emergents, sedges, and grasses), ccmparative abundance of
dominant species, and average water depth.
Table 1 lists the plant species composition, absolute density, relative
density, and total number of species for the six communities in summer
1974. Note that three of the species (C. etricta, C. LacuetriG, and C*
canadeneie) occur in the top seven ranked species in all communities. The
CAREX STRICTA community assemblage had the greatest number of species (58)
and the TRANSITION zone the fewest species (35).
Environmental Changes
The principal physical characteristics examined on the Columbia site
were the hydrologic regime and the thermal regime. The chemical
characteristics of surface and groundwater flows on the -site also were
monitored (Andrews 1978b).
Hydrologic Regime—
Four important attributes of the hydrologic regime have been altered in
the Columbia wetlands (Cosselink and Turner 1978): 1. Source, 2. quantity,
3. velocity, and 4. timing. In 1975, the cooling lake replaced the regional
watershed as the source of water to the wetlands. Leakage occurred through
the walls of the dike and from the bottom of the lake through the peat bed
(Figure 4). Consequently, groundwater discharge rates increased by a factor
of six times with subsequent changes in surface water flow (velocity) and
water level fluctuation (timing or frequency of inundation and its
regularity) (Andrews 1978b).
Prior to filling the lake, the sources of groundwater discharging on
the site were upland areas to the east and southeast and knolls on the
site. Precipitation provided the greatest supply of water, % 76 cm/yr.
Good internal drainage and a constant exchange of water kept water quality
in the wetlands high. Precipitation and groundwater discharge together
usually exceeded evapotranspiration, except at the height of the. growing
season when evapotranspiration exceeded water supply. At that time water
levels in the wetlands were drawn down, and water flow out of the wetlands
almost ceased. Throughout the year water levels fluctuated widely due to
19
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TABLE t.
PLANT SPECIES COMPOSITION. ABSOLUTE DENSITY (D) AND RELATIVE DENSITY (RD)
FOR SIX PLANT COMMUNITIES IN SUMMER, 1974 (T. 1-40)
ftWOT LACUSTRT
Species
Carex ptrieia
Carex laeuatria
Calamagroetia eonadeneia
r/rijopterie thelypteria
Pilea punila
Bidena eoronata
Aetar simpler
Oraelea eenaibilia
Sagittaria latifolia.
Lyeimehfa thyeiflora
Campanula aparinoidcB
Calium sp.
Hentha arveneia
Leeraia oryxoidea
Cirex aquatilia
Carex roetr&ta
Seutallaria galerieulata
Lycopua uniflorua
Typha latifolia
Spiraea alba
Lyeopua amerieanua
Hater lucidulua
Rumax orbieulatua
/tgropyron repena
Heleniun auturunale
Polygotaffn eagittatum
Polygo>:u"i natana
Polygonum eoeeineum
Aater sp.
Cieuta bulbifera
Bvpatorium perfoliatun
Convolvulus eepium
Salix petiolaria
Solanum dulcamara
Lemut minor
Rumex vertieillatua
Lyaimaehia txrreatria
Polygonur. sp.
Luduigia paluptria
Stellaria Imgifolia
Veronla fasclculat.i
S«-4I, S-40
S
(D)
333
229
168
151
K5
109
37
10
29
27
22
18
18
17
15
15
15
11
9
8
8
7
6
5
5
4
4
1
3
3
2
2
2
2
1
(RD)
.226
.156
.114
.103
.099
.074
.025
.020
.020
.018
.015
.012
.012
.012
.010
.010
.010
.007
.00ft
.005
.005
.005
.004
.003
.003
.003
.003
.002
.002
.002
.001
.001
.001
.001
.000
.001
.001
.001
.001
.001
.001
CARKJC STRICTA
Species
Carax atrieta
Cilamgroatia eanadeneie
Lerma minor
Sagittaria latifolia
Bidena coronatx
Leeraia oryzoidea
Dryoptfirio thfflyptario
Carax lar.utttria
Pilea punila
Lyeopua uniflorua
Calium sp.
Unknown
Carex roctrata
Juncuti hranhyecphalua
ftyfiinnchisi thurniflora
Vrrj'f.f**! rW?t-.Tr.t-l
Salix p*itioi.nrin
Hentha aruentsin
Campanula aparinoidea
Phalarifi arundinacna
Polyqtmuni atigittatum
Rochmeria eylindriea
Aat.er aimplax
Kumax orhir.ulatua
Ononlea rtentti-bilia
ittjcfljj'ijft rf3Jn(?i*t*'7rt'*ufl
Carex atjufitilio
Potentilla paluetrie
Polygonun hydropiperoidoii
Triadnnim oirginir.im
f.upatftrium mrulatum
Cinuta bulbife*3
'if^liai'inun /Trofl/Tflscrr.ttiw
Pnlugr.nun mtiinfium
Vicia americana
tlelenittm autumnal?.
!>tfilltiria long\fn\\n
Polyginum ..itann
Attter luniduluti
AotJr punir.nue
Aeorua calomun
Spirnaa alba
Veronita anutellaria
Viola aueullata
S-44, N-46
(D)
698
265
150
129
116
92
85
84
81
57
38
37
36
29
29
28
20
20
17
16
14
II
10
9
8
8
7
7
6
6
5
5
4
4
4
3
3
2
2
2
1
I
1
1
(RD)
.349
.in
.000
.064
.058
.04
.043
.042
.041
.029
.019
.019
.018
.014
.014
.Til 1
.010
.010
.OO1)
.008
.007
.005
.005
.004
.00*
.004
.003
.003
.003
.003
.002
.002
.002
.002
.002
.001
.001
.001
.001
.001
.000
.000
.000
.000
EMERRENTS
Species
Ca rex roa t r& t>i
Carex laeuatria
Sagittaria latifolia
liGTvn mnor
Calium sp.
Aeorua calotuua
Calamgrontia mnadanaia
TypHa latifolia
Pol ygo-.tuft kydropiperoidea
Stellaria longifolict
i.yei.nachia thyi-aiflora
Seirpus fluuiatilia
Hcutellaria galarieulita
Carex atjuatilie
Can's prairea
"pargaiLun c.^r^carputi
t,Hi>un 'imrieanua
l,ijropun uniflorua
l/orippa i.nlrmli'm
Iria tthrcvii
H\t*v>r. orhi^ulatua
Rumr°~z verticill'itue
Spiraea alba
After ai-rrplox
C'lnpanula aparinoidea
,"iun auave
Carux ftrieta
SeirpuK validue
Nquinetun fluviatile
Aliem plantago-aauatioa
r,cut.nllnria latnriflo*!
Vr:mnia faeiicitlfita
S-32, N-38
TO)
270
138
112
84
33
29
20
17
17
16
13
12
11
10
7
•',
1
1
3
2
2
7.
2
2
2
2
1
1
t
1
1
1
<<«n)
.365
.186
.151
.000
.045
.019
.027
.023
.023
.022
.018
.016
.015
.014
.009
f'ifl
.003
.Ml
.O'n
.002
.002
.002
.002
.002
.002
.002
.001
.001
.001
.001
.001
.001
Cent tnucd
-------
(Table 1) conttmie
.010
.010
.008
.008
.005
.005
.005
.005
.005
.001
.001
.001
.001
.001
.001
1-nWIA'JI) TKKKS AND •
Species
Calvngroetia sanadcnsie
Cnecle,-> ccizihilin
Pilea piirrila
Aeter simplex
Carex etrieta
Geranium me-jlatum
r.upat.'jri^ri nzculatum
Spiraea alba
Antzr puniveita
Lyvopufi americanuff
*orfntfi racmfioBa
Sali-x bebbiana
Carex lacnnt>*ia
Attele.riiaR incamnta
Rumex orbir.ulat'to
Cilim ap.
Icnt'na arvensia
Pol'jgonum eayittatun
IjHiiiJigia palitetrig
S-19, N-4
.
•IIRIIRS
(n)
15
12
10
8
3
1
2
2
2
2
2
2
(an)
.214
.171
.143
.114
.043
.041
.029
.029
.029
.029
.029
.029
.014
.Oil
.014
.014
.014
.014
.014
*S*tot«l mmber of opecles, N»numher of quadrats
-------
River
111
Study Area
Cooling Lake
River
230
w
0>
**
0)
220
210
*Z 200
£
1U
IU 190
__. routing uase •—,
i^^ "• — ITI ^r™T^"^P"^7T""^^T™'^^"^^™^^^^ ^^
After
SCO
1500
2000
1000
METERS
Figure A. Study area showing configuration of groundwater flow system before
and after filling of the cooling pond (modified from Andrews
1978b).
22
-------
spring floods, growing season drewdowns, ai*d water level recovery when the
growing season ended (Stephenson and Andrews 1976).
After filling the lake, the Cotal groundwater supply to the wetlands
from leakage greatly exceeded precipitation and evapctranspiration. In 1976
groundwater discharge averaged 305 cm/yr near the dike, with rates as high
as 760 cm/yr in some places. The major zone of groundwater discharge is
shown in Figure 5.
Changes in water depth and fluctuation patterns due to increased rates
of groundwater discharge were evident immediately. Water level increased an
average of 10 cm (Andrews and Anderson 1978). More significantly, water
levels stabilized (Figure 6), This is due to the fact that water supplied
from the cooling lake la constant and the fraction removed by
evapotranspiration is small compared to the total amount of water supplied
by leakage. It is clear from Andrew's data on water levels (Andrews and
Anderson 1980), known elevation points within the marsh, and monthly field
observations, that almost all stations have been continuously saturated or
inundated and, therefore, are anaerobic except for a thin, oxidized layer at
the surface (Gambrell and Patrick 1978) since early 1Q75. Of 20 water depth
measures taken in August 1973 (liite summer vhen evapotranspiration is high),
only one showed water standing above the peat surface.
Prior to filling the lake, no surface water flow was apparent in the
meadow/marsh except for minir flew in two ditches. In winter the entire
area was frozen and covered with snow. Flow is now evident in many parts of
the area, with rates high enough to maintain continuous >pen water during
winter months (Figure 7). Other changes in the physical characteristics of
the study site occurred as a result of increased rates o'J groundwater
discharge. Continuous flooding and high hydrostatic pressures caused
expansion of the peat and lifting or floating up of the surface and root
layer. Thus the effective water depth for plants is frequently less than
the averge increase in water depth. The proportion of qvadrats sampled with
a floating surface layer increased from 1.32 in 1975 to 70.4% in 1977.
Increased and continuous surface water flows have resulted also in the
development of flow channels and substrate erosion. As expected, the
principal flow channels developed within the areas of highest groundwater
discharge. They are most evident in winter (Figure 7) and remain largely
unvegetated throughout the year.
The combined effects of peat lifting, substrate erosion, and channel
development have altered the microtopography of the peat surface. The
variation in surface topography was smoothed in places and accentuated in
others.
Direct hydrologic effects on the Columbia wetlands of leakage from the
cooling lake thus include: 1. Increased groundwater discharge, 2. nearly
constant water levels, 3. higher water levels, and 4. increased surface
water flows. Secondary effects on the wetlands include: 1. Expansion and
Lifting of the peat, 2. development of flow channels, 3.. substrate erosion,
23
-------
INCREASING GROUNDWATER
MajmytUVniirtWua
DISCHARGE
COOLING LAKE
Figure 5. Groundwater discharge patterns in the wetlands (modified from Andrews 1976)
-------
ec
u
u
>
u
cooling lake filled
238.0S
e 237.74
237.44
JAN
1972
JAN
1973
JAN
1974
.'AN
1975
JAN
1976
JAN
1977
Figure 6. Water level fluctuations in the wetland west
of the cooling pond before and after filling
of the cooling pond (from Andrews 1978b).
Marsh elevation varies from 237.26 to
238.20 m.
25
-------
Figure 7. Aerial photograph of meadow/marsh
showing opei! water areas on 1 Hard
1976. White areas are snow-covered.
Lower edge of photograph shows the
west dike of the cooling lake. Area
shown is bef.ween transects 18 and 40.
26
-------
4. changes In substrate ralcrotopography, and 5. alteration of winter ice
formation patterns.
No significant changes in the ionic composition of the groundwatet were
noted in the study area. Chemical characteristics of surface and
groundwater flovs on the. site are given 5n Table 2 (Andrews 1976). These do
not differ greatly throughout the wetland area (Andrews 1976).
Thermal Regime—
Leakage from the cooling lake has significantly altered the thermal
regime of the wetlands in the study area. In general, groundwater
temperatures are warmer and out of phase with normal cycles of plant growth
(Figure 8).
Prior to filling the lake, the temperature of the groundwater
discharging to the wetlands remained fairly constant throughout the year at
% 10°C. Presently, the temperatures reflect the. annual temperature
variation in the cooling lake (1 to 30°C). However, the temporal and
spatial distributions of. water temperature changes in the wetland west of
the coolinp. lake are complex. The location and time of occurrence of the
seasonal maximum and minimum groundwater temperatures in the wetland are
functions of distance from the cooling lake and the distribution of
subsurface materials as well as lake temperature patterns. Because water
moving from the lake to the wetland passes through the subsurface materials,
water•temperatures in the wetland lag behind those of the cooling lake.
Because subsurface materials are not homogeneous in permeability, depth, or
spatial distribution, the time lag is not distributed unifoimly with
distance from the dike. In general, the time lag between the occurrence of
oaximura groundwater temperature and maximum cooling lake temperature
gradually increases, and the amplitude of the fluctuation between maximum
and minimum temperatures decreases with distance from the dike (Figure 8)
(Andrews 1973b). Significant temperature changes are confined to an area
within 100 m of the dike. However, where the peak layer is thickest or
where a layer of pronounced low permeability material occurs below the peat,
temperature patterns are attenuated or may resemble control areas, even
though the area is within 100 m of the dike.
The most significant departures from normal temperature patterns occur
near the dike where a pronounced low permeability layer does not exist
beneath the surface. In these areas, flow through the groundwater system is
fairly rapid. From 1975 to 1976, temperatures of the groundwater
discharging near the dike lagged behind temperatures in the cooling lake by
4 to 8 months. This lag resulted in cold water « 3°C) discharging into the
wetland during spring 1975 and warm water discharging during the late fall
and early winter (19 to 24°C) (Andrews 1976).
Area of Major Impact—
Environmental change has been most pronounced and rapid near the lake
where flow rates of groundwater coming from the cooling lake are highest.
In general, substrate temperature variation, departure from normal temporal
27
-------
TABLE 2. CHEMICAL CHARACTERISTICS OF WATER AT
THE COLUMBIA SITE (FROM ANDREWS 1976)
Parameter
TDSa, ing/liter
Mg, rag/liter
Ca, rag/liter
S04, mg/Uter
N03, mg/llter
POA, mg/liter
Na, rag/liter
PH
Groundwater
200
21
21
7
< 0.01
< 0.02
10
Sedge meadow
230 (variable)
> 20
—
10
< 0.01
< 0.02
17
7.4
Cooling lake
260
10
35
154
0.7
0.2
29
Wisconsin
River
145
5.1
18
86
0.4
0.1
16
dissolved solids.
28
-------
N>
\O
JAN MAR MAY
JUL SEP NOV JAN MAR MAY JUL SEP
1975 1976
NOV JAN MAR MAY
1977
Figure 8. Groundwater temperature variations in wells west of the Columbia cooling pond. Curve A
is based on data from a well cased to 4 m below the surface and located 3 m west of the
dike. Curve B is based on data from a well cased to 2.5 m below the surface and located
60 m west of the dike. The solid line represents normal seasonal temperature variation
in the plant rooting zone for a control site. (Modified from Andrews 1979b).
-------
patterns, surface water flow, and water depth changes are greatest for the
area between transects 18 and 30 (Figure 5). This has been designated as
the area of major environmental Impact for purposes of data analysis. Data
were analyzed for this area alone (transects 18 to 30) and for the entire
study area (transects 1 to 40). Although the area near the dike, between
transects 1 and 17 was subject to similar conditions, only two of the six
communities occurred in the area. Therefore, transects 1 to 17 were not
included In the designated area of major impact.
Plant Community Distribution and Perturbation Patterns
Population and comcunity level responses must be interpreted in light
of the intersections of the spatial distribution of plant communities with .
the different spatial and temporal patterns of perturbation. The plant
communities at the Columbia site have not been subjected to the same
patterns of perturbation. The type, magnitude, areal extent, and timing of
the disturbances were not distributed uniformly either between or within
communities. Each plant community occurred at a range of distances from the
west dike (Figure 3). Changes ir temperature patterns varied as functions
of distance from the dike and groundwater discharge patterns. Changes in
discharge rates varied according to the distribution of subsurface
materials, previous patterns of discharge, and cooling lake temperatures
(Andrews 1978b).
Spatial and temporal gradients of environmental change intersected a
gradient of wetland community types and resulted In a mosaic of changes In
the plant communities. The sequences of change with time differed for each
type of disturbance and are not yet complste. Changes in water levels were
stabilized by 1975. Temperature changes will not reach equilibrium until
some time in the future.
Data sets from two.subprojects of the Columbia Study were used to
characterize the type, magnitude, areal extent, and timing of disturbance.
Data collected by the Hydrogeology Group on groundwater discharge rates,
water levels, and groundwater temperatures were the primary sources of
Information (Andrews 1976, 1978a, 1978b, and 1979; Andrews and Anderson 1978
and 1980; Stephenson and Andrews 1976). Supplementary data from the Wetland
Plant Ecology Group on water levels and temperatures of the substrate in the
plant rooting zone were used to describe differences between community
types. The data set was collected over a greater area of the wetland than
the groundwater data. However, a number of caveats must be kept in mind in
interpreting the data: 1. The data covered limited periods of time—early
summer and mid-fall of each year—and, therefore, do not show Important
seasonal patterns of change in water depth or temperature. 2. Sample sizes
for 1974 (pre-impact) and summer 1975 are small. 3. Temperature data for
each community are averaged over areas subject to a gradient of temperature
changes and thus mask localized differences. Only substrate temperataures
are reported because of high within-sample variability in surface water
temperatures attributable to diurnal changes, localized shading or wanning
effects resulting from the presence or absence of vegetation, or different
water depths. 4. Water depth data for each community reflect not only
changes in absolute water l?vel, but also changes in depth produced by
30
-------
changes in the elevation and !:innness of. the peat surface. Groundwater
discharging from the cooling lake gradually caused the peat to expand In
volume and In some, areas caused the layer containing the live roots of
plants to detach fvom the pea*: mass and float to the surface. The combined
effects of high surface water flow, warmer temperatures, and the consequent
loss of perennial vegetation caused the peat to decompose and erode In some
areas. Thus while water level increased after winter 1975, and depth from
water surface to plant rooting zone both increased and decreased between
1975 and 1977. Depth to the top of the plant rooting zone and depth to
solid substrate were recorded. Figures 9 and 10 show raeen water depth
changes for communities within the area of major impact and for the entire
study area, respectively. Mean substrate temperatures at the time of
vegetation sampling are presented in Figures 11 and 12 for the area of major
impact and the entire study area.
Water Level Changes—
Water levels increased and stabilized with respect to mean sea level by
1975 for all communities; levels varied <0.15 m annually after 1975 (Andrews
and Anderson 1978). Resulting depth changes in the various communities
depended on their respective elevations and drainage characteristics. The
meadow/marsh covered a topographic range of 237.26 t.T 238.20 ra; water levels
stabilized around 237.96 m. Mean water depth changes and standard
deviations for individual communities within the area of major impact are
shown ir. Figure 8. Figure 9 provides similar infornation for the entire
study area. The large standard deviations for all communities are
indicative of the varied raicrotopography and spatial heterogeneity in the
wetlands.
According to data collected during the vegetation surveys, depth
increases were least in the C,\REX LACUSTRIS community (A cm = +3.6 cm for
transects 1 to 40) and greatest In the EMERGENT coismunity (A cm - -f 24.4 cm
for transects 1 to 40). Average increase for all communities was ^_ 10 cm.
By summer 1976 the peat mat had "floated" up in all stations except the
SPIRAEA and LOWLAND SHRUBS and TREES communities. In most cases this
represented an abrupt change from being "non-floating." Thus, after 1975
further changes in water depth shown in the vegetation survey data largely
reflect changes in the structure of the peat bed: ."floating,"
decomposition, and arosion.
Temperature Changes—
Localized temperature changes first became evident in early spring
1975, spread gradually, and have not reached equlibr^.um (Andrews 1978b).
Temporal and spatial patterns of change in and between communities are
complex. No substrate temperatures were recorded at time of vegetation
sampling in summers 1974 and 1975. The spatial distribution of early
temperature change must be inferred from other data.
All communities located north of transect 30 and within 125 m of the
west dike probably experienced significant temperature changes by December
31
-------
'- Depth to lop of rooting
zone
— — — ~ Depth to solid »ubstr»to
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1974 1975 1976 1977
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Depth to to? of rooting
zone
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cubstnte
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1974 1975 1976 1977
F'S'F'S'F'S'F'
1974 1975 1976 1977
F'S F'S F1S F1
1974 1975 1976 1977
Season
Figure 10. Changes in mean water depth hefore and after (January 1975)
filling of the cooling pond for six wetland plant communities
within the entire sampling area. Vertical lines indicate + s.d.
of the mean. A is CAREX LACUSTRIS, B is CAREX STFIICTA, C is
EMERGENT, D is TRANSITION, E is SPI/MEd, and F is LOWLAND
SHRUBS AND TREES.
33
-------
O CAREX I.ACUSTRIS
O CAREX SJRICTA
A EMERGENT
A TRANSITION
D SPIRAEA
E IOWLAND SHRUBS
and TREES
0°
J)
3
Q.
20-
15-
5-
O
8
D
S F S F 1 S F S F
1974 1975 Season 1976 1977
Figure 11. Mean groundwater temperature in t'le plant rooting zone at the
time of vegetation sampling lor '.he area of major impact.
251
20-
•° is-l
10-
5-
8 W7« ' '
1.75 ' ' S 1976 '
Season
' 1977 ' '
Figure 12. Mean groundwater temperature in the plant rooting zone at the
time of vegetation sampling for the entire area.
34
-------
1973. This conclusion is based on the following information. The ilydro£,e-
ology Group first showc-d localized temperature, anomalies in early spring
1975. These anomalies were recorded at 2.1 and 4-6 R below the surface
within 95 ra of the wes!: dike along transect K in the CASEX STRICTA community
(Stephenson and Andrews 19/6). Cold water (<3°C) moving in winter 1975 from
the cooling lake, «.'hich had been filled between 4 November 1974 and 2
January 1975, discharged in late April 1975 near tlic west dike where no
pronounced low permeabi1iiy layer occurred beneath the surface. In general,
no pronounced permeability layer exists beneath the surface near the west
dike north of transect 30. Given this and the face that "temperatures at a
depth of 3 m deviate from those at 0.6 n by less than 1°C" (Andrews 1973b),
it is reasonable to assume that changes in seasonal temperature patterns
occurred in the plant rooring zone over about 50£ of the nreo of major
impact by April 1975. Coin water (< 5°C) discharged in spring, and warn
water (16 to 25°C) discharged during late fall and early winter 1975. At from the dike cold water emerged in raid-summer, and warn water
discharged In late fall 1975 and throughout winter and early spring 1976
(Stephenson and Andrews 1976).
The fall of 1975 changes were evident in toinper.iture data taken with
the vegetation survey- At that time anomlous ter.peratures were recorded at
90 out of 291 quadrats' sampled for the entire wetland. Most anomalies
recorded in fall 1975 were north of transect 30. By summer 1976, tempera-
tures 2. 3°C above control site temperatures were recorded at 192 of 338
quadrats sampled and as far from the dike as 450 n:. In fall 1976, anomalous
tenperatures were- _>. 3"1' colder than the control temperature at distances >
75 -n from the dike or south of transect 30. North of transect 30 tempera-
tures >_ 3°C war.aer the n the control temperature were recorded 50 to 100 tn
fron the west dike. Summer 1977 patterns were similar to those of summer
197fa, witli somt added data from south of transect 30 indicating that warm
water was discharging at 30 of the 36 quadrats sampled between transects 34
and 36. Warmer than normal temperatures also were recorded lit fall 1977,
but at fewer stations south of transect 30.
The trend appears to be one of gradual warming south of tansect 30.
The peat layer near the dike tends to be deeper (Figure 13) and elevations
near the dike tend to be higher than elsewhere. Consequently, temperature
changes here have been gradual and were at first not very pronounced
(Stephenson and Andrews 1976). Localized temperature anomalies were
recorded at the time of vegetation sampling as early as fall 1975. However,
the anomalous temperatures, recorded in. fall 1976 south of transect 30 were
almost all colder than normal temperatures. By summer 1977, warm tempera-
tures had appeared south of transect 30, as they did in fall 1977 over a
somewhat more restricted area.
Spatial and temporal patterns of perturbation are discussed below for
each community type within the area of major impact and the entire study
area. Each conmunity occurs in both areas. The reader should refer to
Figure 3 throughout the discussion.
35
-------
\
INTERVALS
L«J» than 2.'. „..] 1
Between 2' and 5'. Q3
Between 5' and 10'.
Between -.0' and 20.'
Ov«r 20".
Figure 13. Depth of peat and marl deposits at the
Columbia site (from Andrews 1976).
36
-------
CAREX LACUSTRIS Community—
Plant communities within which C. lacustvie was the. most prominent
species occupied a major portion of the study area prior to disturbance
(Figure 3). Before and after pes. turbation the C* laeuetvn.e areas were
subject to rates of groundwater discharge higher than areas in which C.
etricta was more prominent but lowe than in areas characterized as
TRANSITION and EMERGENT communities (Andrews 1976). As discharge rates
increased approximately by a factor of six times, the CAREX LACUSTRIS
community became subject on the whole to proportionately higher discharge
rates. By spring 1976 the Incre.-tsed flow began to cut noticeable
channels. Water level increases, however, were minimal for the community as
a whole, increasing only from a mean of 8.4 ± 3.8 cm in fall 1974 to 11.6 ±
4.8 cm in 1975.
Within the designated area of major impact (transects 18 to 30), the
high surface flow rates resulting from high groundwater discharge within the
CAREX LAC1STRIS community have kept most of It from freezing since winter
1974 to l'.)75. Those portions of the community located near the dike (0 to
100 m from the dike) experienced, in addition, the widest range of
temperature changes (-4°C to +26°C) and the greatest seasonal displacement
of temperature patterns. After 1975, mean substrate ten.oerature in the
CAREX LACUSTRIS community tended at the time of vegetation sampling to be
lower in sunnier and higher in fall than other communities. Stations located
at greater distances were subjec"; to high groundwater discharge but
generally lower and somewhat attenuated temperature patterns resulting from
longer time lags in movement of water from the cooling 2ake through
subsurface materials and consequently greater dissipation of the heat
content of the water.
In general, portions of the community occurring south of transect 30
were located in areas underlain by thicker peat deposits (Figure 13)
(Andrews 1976). Discharge rates here, although comparatively higher than In
the surrounding CAREX STRICTA and SPIRAEA communities, presumably were lower
than rates north of transect 30. Temperature changes and increases in
surface flow rates were consequently more gradual and less pronounced than
In the CAREX LACUSTRIS community lying north of transect 30. Nonetheless,
flow rates were sufficient to cause late freezing and early thawing over
much of the area by 1975 to 1976. Altered temperature patterns have
increased in areal extent since then.
CAREX STRICTA Community--
Plant communities dominated by the tussocks of C* Btrista were widely
distributed prior to disturbance (Figure 3). They became subject to a wide
range of spatial and temporal variation in disturbance patterns depending on
factors previously discussed. However, interpretation of results for the
CAREX STRICTA community differs from that for all other communities, except
LOWLAND SHRUBS and TREES. The CAREX STRICTA community is the only community
with a major proportion of the sampling stations located north of transect
30, within 150 m of the west dike but outside the designated area of major
Impact, i.e., between transects 1 and 17, This means that for Che CAREX
37
-------
STRICT* community, results from the entire sampling ar-aa (transects 1 to 40)
are influenced strongly by impacts similar to those described previously for
transects 18 to 30.
The morphology of 6'. Btficta mediated the extent to which plant
populations experienced water flow and heat effects. The tops of most
tussocks remained elevated above the vater, despite the 8 to 10 cm depth
increase. This diminished the effects of temperature and surface water flow
for plants growing on top of the tussocks. Only plants growing in
depressions between tussocks experienced the full effect of change.
EMERGENT Community—
Prior to disturbance the major portion of the EERGENT community was
located in an area of moderate to high groundv;ater discharge, > 200 m from
the west dike and at the lowest range of elevation. Initial water depths
(X «« 16.5 and 20.0 cm for summer and fall, respectively) were greater than
for all other communities. In general, the community experienced maximum
water level increases (A = +24 cm, /1974 to 1975 for transects 1 to 40) and
minimal temperature effects. Except for the edge of the community bordering
the TRANSITION community where a major flow channel developed, the area
remained frozen in winter. Fewer temperature anomalies were recorded here
than in the CAREX STRICTA, CAREX LACUSTRIS, or TRANSITION communities.
However, the small portion of the community located within the area of major
impact and close to the west dike experienced maximum temperature changes
and winter open water conditions in addition to a water depth increase of
18.6 cm.
TRANSITION Community—
The TRANSITION community was located in a zone of high groundwater
discharge approximately 100 to 250 m from the west dike (Figure 3).
Topographically the community was In an area between the SEDGE MEADOW
communities and the EMERGENT community. Following perturbation the area
became the major channel for surface water movement from the wetland to the
Wisconsin River. The high velocity of water moving into and through the
area has kept much of the community in open water each winter since 1975.
However, tempratures did not change markedly because of attenuation with
distance from the dike. Mean temperatures at the time of vegetation
sampling tended to be somewhat warmer in summer and somewhat cooler in fall
than in other communities, i.e., temperatures were altered slightly but
remained in phase with normal temperature patterns. Water levels increased
no more than average (A » +10.8 cm, 1974 to 1975 for transects 1 to 40).
SPIRAEA Coamunity—
The shrub 5. alba was prominent in two distinct contiguous zones. The
smaller of the two occurred entirely within the area of major impact and
probably experienced some departure from normal temperature patterns by
spring 1975. Changes were not evident in temperatures recorded at the time
of vegetation sampling until summer 1976, likely because of small sample
size in 1975 (n <_ 6). The larger area of S. alba was located south of
38
-------
transect 37, nostly at > 200 in from, the west dike. Tercper.iture changes here
were minimal.
Changes in water flow were, negligible for each are^. Both were snow
covered through the winters 1974 to 1975, 1975 to 1976, and 1976 to 1977.
However, it is reasonable to assume that the substrate within the area of
najor impact did not remain frozen throughout the winters 1975 to 1976 and
197(i to 1977.
Because S. alba tended to occur on slightly elevated "islands" in the
meadow/marsh, it is assumed that water level Increases were minimal.
However, 1974 data do not provide a large enough sample to say definitely
what water levels in the SPIRAEIA community had been. Field observations
made in 1974 indicate that the community usually had no water standing above
the surface after June before leakage frora the cooling lake changed
discharge patterns in 1975. Since that time water has beon _>_ 10 cm deep.
LOWLAND SHRUBS end TREES Community—
Areas dominated by a mix of lowland shrubs and trees also tended to
occur on soaewhat elevated "islands" or "ridges" in the meadow/marsh.
Although data is minimal for 1974, it is reasonable to assume that f.his
community rarely had standing water except at times of flooding. Since
1975, average water depth at time of vegetation sampling was _>^ 10 on.
Surface water flow tends to move around these areas and the community
freezes at least at the surface in winter. Temperature changes—as with
other communities—have been most pronounced in portions of the community
located near the dike.
Plant Populations and Community Responses
Vegetation response associated with leakage of water from the cooling
lake was rapid. Significant departures frora normal shooi: emergence patterns
and extensive mortality of dominant perennial species occurred within 1 yr
of station operation. Rapid invasion of newly opened habitat by annuals and
the spread of tolerant, more hydrophytic perennial species followed. Entire
populations of plants wore depleted and replaced by other species. Some
areas remain completely unvegetated. Species diversity and equitability
decreased overall in spite of increases in species number.
In general, effects on the vegetation occurred first in the area
between transects 18 and 30 where proximity to the eooli.ii}> lake and high
groundwater flow rates coincided. Trends observed here spread to other
areas of the wetland by 1977 and indicate the probable response pattern for
the entire wetland given predicted, long-term thermal alterations (Andrews
I978b). Field observations and sampling data are used below to describe and
quantify the patterns of population responses and community dynamics from
1974 through 1977.
Field Observations of Phenological Change—
Notable departures from normal patterns of shoot emergence and growth
39
-------
first occurred In October 1975, ^ 6 months after the GO.I a station began
operation. At that time, unusually late growth and flowering of S.
latifolia and T, latifclia were noted in localized areas within 25 ra of the
cooling lake's west dike. Color infrared aerial photographs taken on 5
November 1975 indicated active photosynthesis by L. minor up to 200 m away
from the west dike (Wynn 1979).
Plant mortality and altered shoot emergence patterns were extensive and
obvious by spring 1976 within 200 ra of the dike between transects 18 and
30. A large proportion of the ar.ja, which previously 'as densely vegetated,
contained only sparsely scattered live shoots of perennial plants by late
May. Areas of C* lo.custr*is with dense standing dead material showed no live
shoots or only stunted, sparsely scattered clumps. Entire areas of
overwintering and spring emergent shoots of C, fVBtrata. died back by June.
T. latifolia. shoots failed to emerge or emerged late. Numerous forbs
(filentha arveneie, Lyeimachia thyreiflora, and Potentilla paluetrie) emerged,
but their growth was stunted. Some localized mortality of Carex lasiocarpa
and C, aanadeneis also was noted, as was chlorosis and/or poor growth for
many species.
Fall 1976 shoot emergence and senescence patterns also changed. S.
latifolia, T. latifolia, and C. stricta remained green irto late October.
Fall-eraerging shoots of C* lac-ustr-is were reduced in number but were teller
than normal over-wintering shoots. Shoots of T. latifolia, which normally
are formed in the fall but do not emerge until spring, emerged throughout
the fall and into the winter within 50 m of the dike. Most of the emergent
shoots were chlorotic and did not exceed 60 on in heighi'..
By 1977 similar patterns of altered phenology and extensive plant
mortality were evident within 150 m of the dike through rajch of the entire
study area (transects 1 to 40). V.ie phenological changes evident in spring
and fall revealed trends of change in the vegetation otherwise obscured by
apparently "healthy" summer growth. Individual responses signaled
population responses.
Population Responses to Perturbation—
Species response to impact varied according to three factors: 1. life
history characteristics of the species, 2. the location of the species in
the marsh relative to areas of major water temperature changes and Increased
groundwater discharge from the cooling lake, and 3. the community type in
which the species occurred. The population responses of 12 abundant species
are discussed for the area of major impact (transects 18 to 30) and the
entire meadow/marsh.
The average number of shoots per quadrat is used as an indicator of
species response. Summer or fall data are given in the figures, depending
on the phenology of the species under consideration. In general, the
sampling date that expressed the maximum shoot density of the species, e.g.,
after shoot emergence or before senescence, is discussed.
-------
Responses in the area of major impact—The five species—C. lacHGtris,
(.'• etmta, C. roetrata, ~C~.canadensie, and T. latifolia:—are relatively
long-lived, rhizoraatous perennials. T. latifolia generally tolerates deeper
water than the other four species. It often occurs in dense monotypic
stands, and reproduces vigorously by both vegetative spreading (Fiala 1971)
and by seeds. It generally grows to a greater height than the other four
species. C. lacuetris and C. rostratj. are Loth found at intermediate water
depths and may form relatively dense, even stands by producing new shoots
from buried rhizomes (Bernard 1975 and 1976). C. etricta differs from the
two previous sedges in Its tussock growth habit (Costello 1936). The
tussocks, formed of tough, fibrous roots and rhizomes, generally elevate the
shoot bases above the water surface. C. canad&neie has a relatively fine,
but equally fibrous, root system compared to the sedges and appears to be
best adapted to continually damp but not saturated Boll c.ondtt5r>ns (Mueller—
Dombois and Sims 1966). It sometimes occurs as a co-dominant with C.
stricta ir. Wisconsin marshes, growing between the tussocks (Stout 1912,
Costello 1936). Costello (1936) found that C. eanadensie was an important
competitor with C. etrinta, generally outcompeting the tussock sedge in the
drier portions of sedge meadows. However, Stout (1912), in a sr.udy of a wet
meadow in Dane County, Wis., found that C. canadensie exceeded C. stricta in
density and dry weight In the wettest part of the sedge neadow, while C.
etricta was dominant in. somewhat drier portions. The reason for these
contradictory results i^ not clear but may relate to fluctuating water
depths rather than average water depths.
Of these five long-lived, rhizoraatous species only T» latifolia
exhibited a consistent increase in shoot density in the area of najor impact
between 1974 an£ 1977 (I'igure 14). T. latifolia was present in mensurable
•numbers in only the EMERGENT community in 1974. By 1977, its shoot density
had increased more than three-fold in that community. In addition, in 1976
and 1977, T. latifolia appeared in low densities in the TRANSITION
community, indicating it may have been increasing in area and density after
impact.
In sharp contrast to the response of 7*. latifolia, ۥ lacustris and C.
roetrata declined in shoot density in all communities between 1974 and 1977
(Figure 15, Figure 16). In the CAREX LAC'JSTRIS community, C. lacustrie
dropped in shoot density from 12.6 stems/quadrat in 1974 to 2.8
stems/quadrat in 1977. In the four other community types, C. lacustris
shoot density fell to < 1 stem/quadrat (Figure 15).
C. roetrata, preseut in fewer communities in 1974 than C. lacv.etr-ie,
showed a similar response pattern (Figure 16). In the TRANSITION community,
where C. rostrata reached its highest initial density (^ 7.8 stems/quadrat),
it was virtually eliminated by 1977. It also appeared to be eliminated from
the SPIRAEA and CAREX LACUSTRIS communities. However, by 1977 in the
EMERGENT community, C. rosti\ita was still present at > 50% of its original
shoot density, despite a sharp decline in 1975. The greater average
distance of the EMERGENT community from the west dike may account for this
response.
41
-------
3.5-
3.0-
3
-------
14
12-
•f 10-
Z 8'
o
o
o
t»
E
9
C
5»74 197it97» 1977
CAREX LACUSTRIS
U74 19?51976 1977
CAftfX STRICTA
1974 18*5 1S?t 1977
EMERGENT
1974 197S 1976 1977
TRANSITION
1974 197S 1976 1977
SPIRAEA
Figure 15. Carcx lacvstris. Changes from fall 197A to fall 1977 in mean
number of shoots per quadrat (0.25 n)2) within five wetland
planr communities in the area of major impact.
-------
10-
I
2-
1974 19751976 197?
CAREX LACUSTRIS
197) 1975 1976 1977
CAREX STRICTA
1974 197S 1976 19'7
EMERGENT
974 1975 1976 1977
TRANSITION
ISM 1975 1)76 1977
SPIRAEA
Figure 16. Car-ex >\5Si->'ata. Changes from fall 1974 to fall 1977 in mean
number of shoots per quadrat (0.25 m ) within five wetland
plant communities in the area of major impact.
-------
C. str>icta and C. caiiad&risie exhibited remarkably similar treads in
shoot density over the 4-yr period (Figure 17, Figure 18). la general, the
shoot density of both species increased in 197,5 and 1976, and declined
sharply in 1977, except in the SPIRAEA conrounity where both species
sustained an increase in shoot density through 1977.
A change of some interest, which is not evident from Figure 17 and
Figure 18, Is the change in summer: fall shoot density ratios between 1974
and 1977 for C. etricta and ?. ca.nadensi.6. In 1974 for C, canadeneie , and
In 1975 and 1976 for C- etri;ta and C. canadeneia, the fall shoot density
exceeded the summer shoot density in all communities with three exceptions
(C. canadensis, SPIRAEA community, and 1976, EMERGKMT community; C. etriata
1976, SPIRAEA community). The average summer: fall shoot ratios for C.
canadeneis for 1974, 1975, and 1976 were 0.35, 0.46, and 0.86,
respectively. In 1977, the sunnner:fall shoot ratio switched to 1.94. For
C. etriata, the 1975 and 1976 summer: fall shoot ratios were 0.33 and 0.80,
respectively. By 1977, the ratio was 1.19. Tn 197', the summer shoot
density exceeded the fall shoot density in four of five communities for the
two species. The exception was the TRANSITION connvmlty for C. etricta and
the SPIRAEA community for C. canadansie •.
The perennial species — Sagittarf.a latifolia am! Epilobiuw
are short-or medium-lived. S. latifolia. is a short-lived, broad-leaved
perennial usually occurring in somewhat deeper water than (7. 6tr
-------
40-
«OO-
20
E
I^txixHy-i
1974 197S1976 1977
CAREX LACUSTRIS
1974 I97SI9761977
CAREX STRICTA
1974 197S 1976 1977
EMERGENT
:»74 19)."- 1976 1977
TRANSITION
1974 -.97519/6 1977
SPIRAEA
Figure 17. Carex strict.a. Changes from fall 1974 to fall 1977 in mean
number o; shoots per quadrat (0.25 ra ) witiiin five wetland
plant communities in the area of major impact.
-------
35H
30-
25-
3
IT
I
c
15-
10-
5-
1974 197*197* 1977
CAREX LACUSTFIIS
1974 197S1976 <977
CAREX STRICTA
1974 IS.'5 Uri. 1977
EMERGENT
1974 197» 1976 1977
TRANSITION
1974 1975 1976 197 7
SPIRAEA
Figure 18. Calamagrostis camderisis. Changes from fall 1974 to fall 1977
in mean number of shoots per quadrat (0.25 m-) within five
wetland plant communities for the area of major impact.
-------
6-
s 5
T>
S «
o
|
3-
c
i 2
1-
X
1974 19751976 1977
CAREX LACUSTRIS
1974 1975 1976 1977
CAflfX SWICTA
1974 197S 197S 1977
EMERGENT
1974 1975 1976 1977
TRANSITION
1974 197} 1976 1977
SPIRAEA
Figure 19. Sagittaria l&tifolia. Changes from summer 1974 to summer 1977
in mean number of shoots per quadrat (0.25 m^) within five
wetland plant communities in the area of major impact.
-------
The response of S. coloration is shown in Figure 20. Throughout most of
the meadow/marsh complex, E, coloration was rare or only occasionally present
in 1974 and 1975. Prior to impact, it was represented best in the SPIRAEA
community on sites slightly elevated and drier than other portions of the
raarsh. By 1977, in the SPIRAEA and OAREX LACUSTRIS communities, £'.
coloratura increased from a relatively minor species to an average shoot
density of ^ ** stems/quadrat. Its increase in the CAREX LACUSTRIS community
probably results from a decrease, in the C> lacuetrie population, combined
with exposed floating portions of the peat mat, which together provided open
space suitable for colonization by E. coloration seeds. The observed
increase in the SPIRAEA community may be due to increased light availability
on peat exposed below dying Spiraea shrubs.
The annual species—Bidsr.s cerr.ua and Pilsa pier.ila—are capable of
proliferating rapidly by seed in the raeadow/raarsh environment. However,
they differ in germination and light requirements. P. pwnila is a thin-
stemraed, often delicate, shade-tolerant species. It is often found as a
dense group of small plants on the tops of C- etricta tussocks, overtopped
and shaded by the stems and leaves of the sedge. P. pumila appears to
germinate well under cool., moist conditions.
In contrast, B. cerrrun requires an open, sunny site and high soil
temperatures for seed germination, such as is found on exposed mud flats and
floating peat. 3. cernua is a tall, coarse-branched plant that often
overtops the sedges ir. the fall after they have begun to brown.
In 1974, Piled, was present in moderate densities (3 to 12
stems/quadrat) in thre-j of the five community types; it was rare or absent
in the other two. By 1977, its shoot density increased dramatically in the
three communities whera it was originally present in moderate numbers.
Pilea reached a remarkably high density of 144 stems/quadrat in the SPIRAEA
community in 1977 (Figure 21).
Prior to impact, I', cernua was not present in measurable numbers in any
of the five communities (Figure 22). In 1976 and 1977, B. cernua shoot
density increased suddenly in the CAP.EX LACUSTRIS and CAREX STRICTA
communities from near 0 to ^ 5 and 13 stems/quadrat, respectively. In the
SPIRAEA community, a smaller increase was noted for 1976 and 1977. Low
densities of B. cernua also were noted in the TRANSITION and EMERGENT
communities by 1977.
Although these two annual species differ markedly in germination and
light requirements, locally large increases in shoot density in both species
were measured. This indicates that the impact of water level, flow, and
temperature changes in the area of major impact has been severe enough to
create opportunities for colonization and invasion by annuals, as well as
seed-dispersed perennials, like E. coloration, in a previously closed, mature
community. The responses of these three species, along with other indicator
species such as L. minor (discussed later), can be used to characterize the
magnitude of the changes in physical and vegetational aspects of the
meadow/marsh.
49
-------
c
«H
w
•O
3
1 3-
E
c
•i
2
1-
X
«^ •
X
197J I97S1976 19.'7
CAREX LACUSTRIS
197« 197S197& 197'
CAREX STRICTA
197J 197S 1976 1977
EMERGENT
1974 1975 1S7H977
TRANSITION
!$:•« 19: 1976 1977
SPIRAEA
Figure 20. Epilobiun colorctum. Changes from fall 197A to fall l'.)77 in
mean number of shoots per quadrat (0.25 tn2) within five wetland
plant communities in the area of major impact.
50
-------
144 3
30-
•
•o
a
cr
= 20
o
2 15
Z 10
5-
X
X
19/4 197519/6 1877
CAKE* LACUSTFUS
1974 1975 1976 1477
CAREX STRIC1A
1974 197S 1976 19?:
EMERGENT
1974 197S 19'6 1977
TRANSITION
1974 197S 1976 19> 7
SPIRAEA
Figure 21. Pilea pumilo. Changes from summer 1974 to summer 1977 in mean
number of shoots per quadrat (0.25 m2) within five wetland
plant communities in the area of raa j _>r impact.
51
-------
14-
12-
£ 10-
•5
s
9
4-
2-
'.974 19751976 1J77
CAREX LACUSTftIS
IV'« 1975 1976 1977
CAREX STRICTA
1974 1975 1976 19/7
EMERGENT
1974 1975 IS7C 1!>77
TRANSITION
1974 1975 1976 1977
SPIRAEA
Figure 22. Bidens cernua. Changes from summer 1974 to suraner 1977 in mean
number of shoots per quadrat (0.25 m2) within five wetland
plant communities in the area of major impact.
52
-------
Responses over entire iriarsh—Data for species responses over the entire
marsh (transects 1 to 40) average information from the severely- and less-
impacted areas of the marsh, Thus, for most species, population changes
between 197-'* and 1977 in. the whole marsh show similar, but less pronounced,
trends in shoot density than the area of major impact. However, in some
cases, somewhat different trends are apparent in data for the entire
sampling area. For certain species—S. eurycarpivn and 5. alba—the major
portion of the population was located originally almost entirely outside
transects 18 to 30. For these species, particularly S. eurycafpum, the data
from the entire area are especially informative.
Of the long-lived Carex spp., Carex rostrata formed a disproportion-
ately large part of the total population in communities outside transects 18
to 30 prior to impact. In 1974, the average shoot density of C. r\}strata in
the TRANSITION and EMERGENT communities was 2 to 4 times greater for the
whole marsh than for transects 18 to 30 (Figure 23). However, the final
shoot densities of C* rosi.ra.ta. for the whole marsh data in 1977 were nearly
as low as those recorded in the area of major impact. Thus, for C-
roetratat the decline in shoot density averaged over the whole marsh was as
great or greater than the decline observed in transects 18 to 30.
Carex striata also showed somewhat different trends between the two
data sets. Shoot density of C* etricta averaged over the whole marsh
(Figure 24) in 1974 was substantially higher in at least two communities
than in the corresponding community types in transects 18 to 30. In the
CAREX STftlCTA community, shoot density for the whole marsh was 100% higher
than in transects 18 to 30, while in the CAREX LACUSTRIS community, shoot
density was > 70 stems/quadrat for the whole marsh compared to 3
stems/quadrat in the area of major impact. T,-.ese high 1974 values for the
whole marsh, when compared to 1977 values, indicate net decrease in shoot
density of C, etviata in two communities, namely, CAREX LACUSTRIS ard CAREX
STRICTA types. This is a reversal of the trends shown for C. etricta in
these two communities in the area of major impact (Figure 17). In addition,
C* etricta remained at jv 10 stems/quadrat in the TRANSITION community from
1974 to 1977 in the whole marsh data, rather than decreasing as shown for
transects 18 to 30. The variability may reflect the comparatively small
sample size in transects 18 to 30 for 1974 and 1975 (n = 8).
In contrast to the preceding two sedge species, C. lacuetriB shoot
density did not differ markedly between the area of major impact and the
whole marsh (Figure 25). As expected, the only noticeable difference is
that C> lacustris shoot density does not drop quite as low tn the whole
marsh as it does in the area of major impact, e.g., it remains slightly > 1
stem/quadrat instead of being virtually eliminated.
For the whole marsh, 2*. latifolia responded In a manner similar to that
of the major impact area (Figure 26). Shoot density was marginally lover in
the whole marsh, and the increase for each successive year after impact was
lower compared to that shown in Figure 14. That is, general trends were the
same but lagged each other in time.
-------
16-
14-
ii "
3
S 10J
o
r 8^
f
3
C
c 6H
4-
19 M 19:119/6 19;;
CARCX LACUSTRIS
I97J W"S-9:S I9.T
CAREX STR/CM
19*4 IS'S 1976 19'7
EMERGENT
I9'4 I9'S 1976 1977
TRANSITION
i9/« 1975 1976 1977
SPIRAEA
Figure 23. Carex rostrata. Changes from fall 1974 to fall 1977 in mean
number of shoots per quadrat (0.25 m2) within five wetland
plant communities for the entire sampling area.
-------
t97S *9*6 1977
CAREX LACUSTRIS
1S7J 1975 1976 1977
CAREX STRICTA
1»74 1975 1J76 1977
EMERGENT
97S 197t 1977
TRANSITION
1974 I»7S 1976 1977
SPIRAEA
Figure 2A. Carex stficta. Changes from fall 1974 to fell 1977 in mean
number of shoots per quadrat (0.25 m^) within five wetland
plant communities for the entire sampling area.
55
-------
X
x
K^3
XX
CAREX LACUSTRIS
19711976 '977
STRICTA
EMERGENT
H7< ,97515761977
TRANSITION
1S74 1975 1976 1977
SPlXAEA
Figure 25. Carcx Za.?:«sirts. Changes from fall 197A to fall 1977 in mean
number of shoots per quadrat (0.25 m^) within five wetland
plant coanunities for the entire sampling area.
56
-------
a
a
«r
I
3
C
e
2.5-
2.0-
1.5
1.0-
05-
1974 19^519:* i9.v
197J HJi 19/6 1977
CARf X STRICTA
1VM 197S 1976 19'7
EMERGENT
1974 I97> 1976197'
TRANSITION
197419751976 1977
SPIRAEA
Figure 26. 7^;^.'. latifolia. Changes from fall 1974 to fall 1977 tn mean
number of shoots per quadrat (0.25 m ) within five wetland
plant cominunities for the entire sampling area.
57
-------
The response of C. canadensie differed only slightly for the two data
sets. The overall shoot density in the whole marsh (Figure 27) generally
fluctuated less than in the area of major impact for all years. This is
Hkely a function of smaller sample size for transects 18 to 30.
Of the sediura- or short-lived perennials, E. coloratura responded in the
same manner in the entire marsh as it did in the area of major impact.
However, as expected for an invading species, shoot densities w-are slightly
higher In the -area of major impact.
5. eurycarpum is a deep water emergent species. It often occurs with
T. latifolia but in less dense stands. Because of its tolerance of deep
water, Sparganium might be expected to be favored over the sedges with an
increase in water depth. However, it is not aggressive enough to compete
well with the densely growing and rapidly spreading ". iatifolia*
Although Sp^iftjam.icn did occur locally in the area of major impact, a
disproportionately large part of the population occurred outside transects
18 to 30. Prior to disturbance, it was confined largely to two community
types—the ElERGtNT and TRANSITION communities (Figure 28). It appeared in
very low densities in the other communities by 1976 and 1977. s. Eurycarpun
exhibited a small net Increase in shoot density in the TRANSITION community,
but decreased in shoot density in the EMERGENT type,
S. alba is a shrub species that generally occurs on topographically
higher- and better-drained sites than the CAREX STRICTA community. Usually,
a clump of Sp7"-Tvzea stems will shade the ground surface, reducing the types
and densities of understory species. Because the presence of S:>iraea
identified a site as belonging to the SPJ'\ASA community, almost all the
individuals of Spimca counted were confined to the SPIRAEA corcr.-.unity.
In both the area of major impact and the marsh as a whole, shoot
density of S. alba increased for 2 yr after impact, peaking in 1976, and
then decreased in 1977. In the area of major impact, shoot density was 2.3
stems/quadrat in 1974, rose to 7.4 in 1976, and decreased to 1.6 in 1977.
For the whole marsh, shoot densities changed from 1.2 to 5.9 to 2.7
stems/quadrat for the same years. In both cases, the decrease in 1977
probably opened up substantial colonization space on the comparatively less-
saturated substrate for numerous opportunistic species, like P. pumila and
E, coloration.
L. mi-noTf is a floating aquatic plant in which the tiny individual
plants are blown across the surface of the water by the wind. Many hundreds
of individual plants may accumulate in a square meter of water surface,
especially where the wind has blown them in among the stalks of the emergent
species. Because of its floating habit and nearly ubiquitous presence on
still, open water, the presence of moderate to large numbers of Lerma. can be
used as an indication of the amount of open water in a community.
Figure 29 shows the estimated shoot density of L, minor over the whole
marsh. A consistent general fend toward higher densities of Lernna In 1977
compared to 1974 was observed for all community types. This is the expected
58
-------
20-|
XI
S is
o
a
10-
5-
1974 t»7S197« 1977
CAREX LACUSTRIS
1974 197S 197fc 1977
sr«?/cw
197J 18'5 197S 1977
EMERGENT
If' I97S 1976 1977
TRANSITION
1974 \97S UTt 1877
SPIRAEA
Figure 27. Cal&nagrostis ccoizdensis. Changes from fall,1974 to fall 1977
In mean number of shoots per quadrat (0.25 m~) within five
wetland plant cocmunities for the entire sampling area.
59
-------
S
s-
4-
1 *
c
H
1»74 197S 197* 19>7
CARfX LACUSTRIS
1)74 197S 1976 197?
sraiCTA
1974 197S 19761977
EMERGENT
1974 197S 19/61977
TRANSITION
1»7« W7S1976 1977
SPIRAEA
Figure 28. Sparganium eurycarpum. Changes from fall 1974 to fall 1977 in
mean nuniber of shoots per quadrat (0.25 ra2) within five wetland
plant communities for the entire sampling area.
60
-------
60-,
5 50-
S «
-------
result of an Increased area of. open water In the meadow/marsh community due
to the combination of Increased water depth and high mortality of dominant
rooted species.
Species response In the area of major impact cannot be compared with
that in the enilre marsh for species reaching maximum density In surcmer. In
1976 and 1977, sunnier data were collected only for transects 18 to 30.
Thus, a full comparison of su.nmer data for the two areas through 1976 and
1977 Is not possible for 3. l-zti.folia, B. cernua, or P. pumila. Fall data
cannot be used for Pag-Cttaria because It dies back comparatively early and
decomposes rapidly (Lindsley at al. 1976). Although the decomposition is
less complete, the same Is true for P. purrila and 3. cerniia. Field
observations Indicate that densities of Bidene and Pi-lea increased In the
entire narsh from 197'i to 1977, but to a lesser extent than in tho area of
major impact.
Community Responses to Perturbation—
Four measures were used to assess the response of wetland plant
communities on the Columbia site to water level and heat stress:
1. If Is mean number of species per quadrat,
2. S Is total number of species for all quadrats sampled.
S and S are measures of species richness.
n
where
3. H' - - E p In p (1)
i-1
H' Is the Shannon-Wiener diversity Index (Peet 1975) combining
species richness and the distribution of abundances of
Individual! In the different species, and
Pl Is the proportion of total number of individuals contributed
by species 1.
H' U>
™ " ( •) \
IZJ
H« In S
max
where
J is the distribution of abundances In terms of their evenness
or equitabillty and is the opposite of.dominance; if J Is
low, dominance Is high, and H' x is the maximum value of
H' for the given number of species (S) (Plelou 1975)
1> was computed using the entire set of count data for the 50 x 50 m grid
which varies in number of saaples from year to year. However, S, H', and J,
which vary with sample number (Peet 1975), were computed on uniform subsets
of the data In order to allow comparisons to be made from year to year.
Five subsets of equal sample number were selected randomly from the entire
set of count data for each community for each sampling period. S, H*, and J
were computed for each random set. The individual values were used to
62
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calculate mean values---S*, H*, and J*—defined as the arithmetic mean of S,
H', and J for the five random sels. Sample numbers for the full data set
and the five random sons for each community and sanpling period are shown in
Table 3. Each measure was computed for each community for all sampling
periods for the area of major Impact and the entire sampling area.
A fifth measure, tlie proportion of fiuadrats containing no rooted vege-
tation, was calculated for- the area of major impact. It is based on all
data and considers all communities together. The proportion is the ratio of
quadrats containing no rooted vegetation to the total number of quadrats
sampled. A similar measure using the proportion of quadrats containing only
annual vegetation also was calculated.
Results of community-level measures of wetland response to leakage from
the Columbia cooling .lake show significant, o'oarigoi. occurring In the struc-
ture of the plant communities. Diversity (!!*) and equilability (J*)
decreased overall fro:n 1974 to 1977. Species richness usually decreased
initially but showed a net gain froi:i summer 1974 to suririer 1977 for most
communities. Major decreases occurred in all values by summer 1975 and were
similar throughout the sampling arey. Subsequent responses varied for the
two different sar.iplin;;; areas, from community to community, and for summer
and fall, sampling periods. The greatest magnitudes; of change tendod to be—
but were not always confined to—the designated area of major impact.
Changes following perturbation in species richness (S and S*), equlta-
billty (J*), and diversity (H*) are discussed by community type. The CA3XX
LIC'JSTRIS, CAREX STK1CTA, C-IEKCENT, and TRANSITION' communities are compared
for each of four data sets:
1. Transects 18 to 30 (summer set) cover the designated area of raajor
impact for t.ie summers or 1974 to 1977.
2. Transects 18 to 30 (fall set) cover the area of major impact for
falls of 197* to 1977.
3. Transects 1 co 40 (summer set) Include data for the entire sampling
area for 1974 and 1975.
4. Transects 1 Co 40 (fall set) include data for the entire sampling
area for falls of 1974 through 1977.
Within the area of major impact, sample size for the CAREX STRICTA and
EMERGENT communities was small (8 and 10, respectively); results are inter-
preted accordingly and in light of additional information provided by
results from the larger data set (transects 1 to 40). The SPIRAEA and
LOWLAND SHRUBS and TREES communities are discussed separately because of
small sample size in most data jets. Sample size is consistently large
enough for trend analysis from 1974 through 1977 only for the fall data set
for transects 1 to 40. Additional information on the SPIRAEA community is
provided by a small data set (n - 10) for transects 1 to 40 for summers 1974
and 1975. Results from the four data sets are summarized in Figures 31 to
34 and Tables A-l to A-4 ot Appendix A.
63.
-------
TABLE 3. SAMPLE NUMBERS FOR THE FULL DATA SET AND UNIFORM RANDOM
SUBSETS FOR EACH COMMUNITY3 AND SAMPLING PERIOD
Sampling
period
Communities for
transects 18 to 30
B C D E
Communities for
transects 1 to 40
Summer 1974
Summer 1975
Summer 1976
Summer 1977
Fall 1974
Fall 1975
Fall 1976
Fall 1977
FULL DATA SET
16
17
28
28
8 16
8 14
18 26
18 24
10
18
20
22
2
6
8
8
10 10 10 10 6
22 12 12 10 8
22 15 16 18 8
28 17 24 19 8
2
2
10
10
4
7
8
9
40
55
26
48
42
76
46
56
38
91
55
99
40
38
32
38
40
69
26
44
26
30
32
51
UNIFORM RANDOM SUBSETS
10
16
16
20
19
26
6
14
27
64
39
63
Summer 1974-77
Fall 1974-77
16
10
8 14
1C 10
10
10
2
6
2
4
40
26
46
38
38
32
26
26
10
If
6
27
aA Is Carex lacuetrie, B is Carex etricta, C is Emergent, D is Transition,
E is Spiraea, and F is Lowland Trees and Shrubs.
64
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CAHKX LACUSTRIS conmuntty—Tht- pattern of response fr.r tho CARSX
LACUSTRIS community in the designated area of major impact, was one of major
decreases in all values followed hy significant increases in all values
after a period of little to moderate change (Figure 30). Prior to distur-
bance, the CAREX LACiiSTFtIS coramun.vty had higher values for species richness
(S~ = 5.38), species number (S* = 26), and diversity (II* = 2.36) than any .
other community in the area of major impact:. It__also had the highest values
for species number (S* = 31), species richness (S " 7.46), and diversity (H*
= 2.18), as well as for equitabilily (J* = 0.63) in 1977, i.e., two £ull
years after the generating station began operation. In rhe case of S and
S*, 1977 values were higher than 1974 values.
Between summer 1974 and sunnier 1977 the CAREX LACUSTRIS community
experienced marked decrease and marked increase in community measures. From
1974 to 1975, the community lost a greater number of sper.ies (AS = -1.8,
S* = -7.6) than any other community. At the same time, diversity (11*)
dropped dramatically (AH* = 0.68) and n shift toward gre.-iter dominance
occurred, as evidenced by a drop in J* of 0.14. F.quitabllity continued to
drop through summer 1976. Diversity, however, increased slightly (AH* =
+0_.pl), apparently as a result of the moderate increase in species richness
(As a 0.88) and species number (AS* = 4.4). Frowi summer 1976 to summer 1977
Species richness and species number in t.he CAREX LACUSTdTS community shoved
the greatest change seen in these measures in any community for any sampling
year^ increases of 2.5 and 8.0 for S and S*, respectively. With 1977 values
for S and S* exceeding 1974 values, diversity (H* *• 0.63) returned to within
0.09 of its pre-treatraent value. Equitability, likewise, returned to near
its 1974 value.
Fall data for the designer .id area of imjor impact show essentially the
same trends for community-level measures as the summer d;-.ta (Figure 31). A
notable exception for the fall data is a reversal in the direction of change
shown from summer 1975 to summer ".976. Fall values for species richness
(S), species number (S*), and diversity (H*) fell fro;n H:75 to 1976; equi-
tability (J*), on the other hand, increased. Fall 1976 to 1977 changes in
richness and diversity were in the same direction as summer 1976 to 1977
trends but the increases were less dramatic. Equitability (J*) remained at
its 1976 vaxue, 0.09 below its pre-treatment value.
Data analyzed for the area of major impact (Figures 30 and 31) show
somewhat different patterns of response than the data sets (3 and 4 earlier)
for the Carex lacuetris community taken over the entire sampling area
(transects 1 to 40) (Figures 32 and 33). Differences appear in direction
and magnitude of change, the overall pattern suggesting that before summer
1976 the area north of transect 30 was responding to different types or
magnitudes of disturbance than the area south of transect 30.
Summer values of S*, H*, and J* for the entire marsh dropped from 1974
to 1975, as they did in the area of major impact. However, the magnitude of
the decreases were less. Given the contribution from the area of major
impact to these measures for the entire srea, they likely decreased very
little. Equitability had dropped considerably within the area of major
Impact from 1974 to 1975, but changed little for the entire sampling area.
65
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48-
40-
| ~36"
S 24-
^
E 16-1
ft
2.6-
2.0-
>i
C
$ 1.0-
0
no
£ 1.
-------
46-i
o 24-
5
° 16i
2.6-
2.0-
I
5 1.0
0.0
1.0-,
0.0
n
m
1»7« 1»75 1976 1977
CAREX LACUSTRIS
<974 1975 1976 1977
CAREX STRICTA
1974 197» 1976 19V7
EMERGENT
1974 197S 1076 1977
TRANSITION
Figure 31. Community measures before (1974) and following disturbance
(1975 to 1977) for four wetland plant communities. Data
presented are fall data for the area of major impact.
(S and S are measures of species richness; H' is the
Shannon-Weiner diversity index; J is distribution of
abundance in terms of equitability.)
67
-------
48-|
"40-
32-
24 •
16-
8'
0
s-
00
2.8
2.0
itr
0.0
1.0-;
o.o
m
1974 1975 I97» 1977
CAREX LACUSTRIS
n ;
1S74 1975 1978 1977
CARES, STRICTA
m
\
-
1974 1975 1976 1977 1974 '975 1976 1577 1974 1975 1970 1977
EMERGENT TRANSITION SPIRAEA
Figure 32. Community measures before (1974) .nnd following disturbance (1975 to 1977) for six wetland _
plant communities. Data presented are summer data for the entire sampling area. (S and S
are measures of species richness; H1 is the Shannon-Weiner diversity index; J is
distribution of abundances in terms of equltability.)
-------
48
40-
32-
I iH
e-
/ xV. V7
at
3JO
x
"5
5
5 10
0.0
Ul
OJO
1974 197} 1976 197V
CAREX LACUSTRIS
dm irrm ]iTn-i iFTTri |[TTn llhm
1974 IS75 Hf6 1K77
C4REX SrftfCTVt
t«74 1975 H76 l» 7
EMERGENTS
U74 H7S ;9'6 1977
TRANSITION
1)74 197S 19/6 1977
SPIRAEA
1971 197b 1976 197 T
LOWLAND SHRUBS
en-1 TREES
Figure 33. Community neasures before (197A) and following disturbance (1975 to 1977) for six wetland
plant communities. Daca presented are f,.j.l data for the entire sampling area. (S and S
are measures of species richness; I!1 is the Shannon-'vetner diversity index; J is
; distribution of abundances in terms of equitabil.ity.)
-------
This suggests that south of transect 30 cquitabi. li ry actually increased
from 1974 to 1975.
In the case of fall data for 1974 to 1975, the direction of change in
S\ 11*, and J* is reversed fro!n that for transects IS to 30. The magnitude
of increase Iti these measures over the- entire sampling sroa was as great as
the raagni tude of the decrease in Che area of najor impact, ilowever, for S*
the direction and oiagnitude cf change were similar.
After 1975, data collected outside the area or Major Impact exist o;ily
for fall. Tt shows that differences in the pattern-; of respoi.se for the two
sampling areas were not as great after 1975 as they were from 1974 to 197;-.
The overall pattern suggests that community level effects spread from 197? .
to 1977 over a greater and greater portion of the area south of transect.
30. Tron 1975 to 1976 only the direction of change, in J* and the magnitude
.of the decrease in il* differ between the two sampling areas. AM values
dropped moderately — except for J* for the area of major impact and U* for
the entire sampling a re a- -which increased. Diversity Jioppod almost twice
as nuch as H* for the area of major impact. Apparently, although decreases
In species number (S*) occurred immediately, significant shifts toward
greater dominance were delayed lor 1 yr in th« CAftSX. LACJSTtilS community
south of transect 30.
Diversity In the entire sanpling area continued to drop from fall 197o
to fall 1977, while in the area of major impact diversity reversed direction
and b-!gan to increase. Furthermore, J* continued r.o doc.lirie for the entire
campling area, whereas in tfu area of najor irap/ict ic re::ia.'ne
-------
Trends in the fall 'data (Figure 31, Figure- 33) frora 1974 co 1977 in the
area of major impact, were largely the opposite of those for the CARSX
LACUSTRrS community. In general, values increased froia 1974 to 1975 and
dropped from 1975 to 1977 to well below their 1974 values. W:ith the excep-
tion of species number (S*), which fluctuated widely over the entire sar.i-
pling area, trends for the entire sampling area were similar t:t of lower
magnitude than fall changes ir. the area of major impact.
EMERGENT community—The greatest net change occurred in the EMERGENT
community. Changes were immediate, generally of greater magnitude than
changes elsewhere, and nearly uniform in direction (Figures 30 to 33).
Values for all community measures decreased_consistently from 1974 to 1977.
The only exceptions were species richness (S) which increased frora 1970 to
1977, and species number (S*), which climbed after 1975 in the area of major
impact. Otherwise, patterns of response were rer.Mrkably similar for the
entire sampling are.-, and the are* of major impact.
Prior to disturbance^ the EMERCF.NT community liad lower sun:ner values in
both sampling areas for S, II*, and J* than an> other community. From 1.974
to 1977, the EMEV.CEr.'T community showed the greatest net change in diversity
(AH* = -1.10) am? i?",'.:ilabililv (iJ* = -0.35) seen in any community. By
1977, surame^ values for all measures were lower than in any other community
in the area of ma jor i.npact the greatest decrease occurred f roa 1074 to
1975.
Fall p?ttorr.-K were similar but the decreases were more uniformly dis-
tributed from year to year. The values of S*, I!*, and J* decreased to a
greater exee-.it i n the area of najor impact than in the cut Ire iaarsh.
TRANS 1TION comnunity— Liko the EMERGENT community, changes in the
TRANSITION community follow similar overall patterns for the os-.tire marsh
aiid the area of major impact (Figure 30, Figure 33). Prior to disturbance,
the TRANSITION community, considered over the entire sampling area, had the
lowest value for species number (S* » 26), but the highest value for equi-
tability (J* •» 0.78). Following disturbance, summer values decreased from
1974 through 1976 for all measures. From 1976 to 1977, species number (S*)
toso to above its 1974 value; diversity (H*) and equitability (J*) befean to
Increase but remained well below 1974 values.
*
Fall data do not show the 1976 to 1977 change in direction of response.
Most values continued to decline through 1977. The exception was species
number (S*). which_increased dracatlcally in the entire sampling ?roa.
Species richness (S), which usually paralleled species number (S*), followed
H* and J* in continued decline through fall 1977.
Although the overall pattern !s similar for both sampling areas,
notable differences occurred in the magnitude of the response. Initial
decreases seen in the summer dcta from 1974 to 1975 were—except for species
number (S*)—somewhat greater for the entire marsh than for the area of
oajor impact. However, differences seen in the fall.data show greater
change In the aree of major impact. Greater net decreases in all values
except S* occurred from fall 1974 to fall 1977 In the area of major Impact.
71
-------
Decreases from \.\ll 1970 to f.ill 1977 in speci.?s richness (S), diversity
(II*), and eqvii tabil ity (J*) also were greater in tho designated area of
major Impact.
SPIRAEA and LOWLAND SHKL'BS and TiU'.^S comnimii I i^s—The- restricted data
avai lable f"or"T»7e~5>/.T'/15.-! ,m^ LOWLAND TFiIf|TBS~and"' TKKKS communities (Figure
32, Figure 33) show net decreases frou fall H7-i to fall 1977 in all
measures for both communities. As in oilier comnunltles, significant changes
occurred by 1975. Species nunber (S*) increased in the LOWLAXU SlIKUBt; nnd
TRF.ES community from 1974 to 1975. All other values decreased in both
communities.
After 1975, fall values for diversity ('!*) declined continuously in
both communities. Species richness (S) decreased each year for the 'LOvJLAND
SHRUBS and TRKES community. Other fall value? increased and decreased.
Only species richness in tho SPIKnEA community returned by 1977 to near its
1974 value.
Changes In Vegetative Cover—
In addition to major shifts In dominance and diversity patterns in eacn
plant community, a continuing trend of decreasing vegetative cover occurr-.d
in the Columbia wetlands from 197-i to 1177. Open water and exposed mudfi.-ts
replaced the previously closed and densely vegetated perennial plant coir.rau-
nitit".« over an increasing portion of the study area (Figure 34). Annuals
colonized some of the habitat opened by the removal of perennial species,
but large areas remained unvegotated. By 1977, 19^ of the ^uadrats sampled
in tho area of major impact had no rooted veyi'f-U ion. Another 2Z contained
only annual vegetation (Figure 35).
OlSC'JSSIOrJ ANIl CONCLUSIONS
Changes in plant population numbers, vegetative cover, species rich-
ness, diversity, and equitabllity such as those seen in all wet land commu-
nities on the Columbia site reflect" major changes in the composition and
structure of the plant cornmuntties. The trends toward a greater abundance
of hydrophytic species and decreasing vegetative covvr follow the expected
pattern for wetlands subject to Increased and/or more constant water levels
(Weller and Fredrickson 1974, Van der Valk and Davis 197«b). The predomi-
nant trend of decreasing diversity from 197A to 1977 also follows an
expected trend. However, the year-to-year and specific community patterns.
of response shown in the diversity data did not follow a singSe trend and
were not readily' interpret.ihie. As data for the different cooraunities
reveal, no uniform raonotonlc relationship existed between disturbance and
species diverslty-neither species richness nor distribution of their
abundances. Disturbance ^Hd not simply increase or decrease plant diver-
sity. Species richness (S and S*), diversity (H*), and equitability (J*)
all decreased in most cases, but increased in others, and frequently did
both during the period froa 1974 to 1977 in the Columbia wetlands as the
spatial distribution and intensity of the disturbance Increased.
72
-------
Are* 07 temperature
• *| Area 08 temperature
MWD 8 3* 5.4cm Area 07
Jan Feb Mar Apr May Jur J il Aug Sep Ocl Nov Dec Jon Feb Mar Apr May Jun
1977 „ 1978
Date
Figure 34. Temperature patterns in the substrate and mean water levels
(+ s.d.) at control sites for Typl-ia 'iatifolia (Area 07) and
Carer laaustri.s (Area 08).
73
-------
20-
Q.
o
f 15
•o
o
o-
2 10
o
*> re J
j Percent cl quadrat* with no rooted vegetation
^^^^^r^H
1 Percent of quadrate with only annual vegetation
1974-
Wlriter
Winter
•1975-
-1976—
Winter
Winter
1977-
Figure 35. Changes in vegetative cover from 1974 to 1977.
-------
The data for Individual plant populations considered together with the
results for measures of community response suggest that differences in
diversity patterns observed between coranumities, and between the area of
major imp.-ict and the entire sampling area, can be explained by two factors:
1. The spatial and tenpor.il patterns of disturbance, and 2. the comparative
sensitivity of dominant plant species to disturbance (Harper I?'(j9, Lubchenco
1978, Caswell 1978). Whore disturbance was of, the type to wlil«:h dominant
species wero sensitive, diversity and equltability Increased a:' new or
competitively inferior species colonized or spread to space made available
by the decline of previously dominant populations. Diversity and equlta-
bility decreased where one or two dominant species were favored by the
disturbance.
Changing diversity patterns paralleled changing temporal and spatial
patterns of disturbance. From 1974 to 1975, tho entire ares was subject to
the same disturbance, i.e., permanently elevated water levels and increased
groundwater discharge. All communities in both sampling areas responded
similarly. Species richness, diversity, and e^uitability dropped in all
comnunities. This appears to be the result of density decreases in some
dominants, tho removal of some non-dbninant species by flooding, and the
concomitant and dramatic increase of I,, "finer* in newly-available open water
areas. The greater magnitude of the decrease in the area of major impact
for the CA3ZX i.ACUSTHIS a;id JAZZX ^TKICTA communities may reflect the
generally higher discharge rates and lower topographic position of these
communities north of transect 30.
After spring 1975, disturbance patterns became more complex as an
increasing area of the raarsh experienced temperature changes. Significant
changes in temperature were localised at first, spread only gradually, and
have not yet readied equilibrium. In general, the CAHEX LACLIS7RIS and CA.-.EX
STftlCTA communities were subject to more heat stress earlier bi.cause they
tended to he located no.irer the dike than the major portions of the
TRANSITION and EMEKCEf.'T communities. Both the TRANSITION' and LMEKCENT
communities, however, were subject to low-level temperature changes
resulting from high groundwater discharge and surface water flow. Surface
water froze later in wintsr and thawed earlier in spring. Major flow
channels remained open throughout the year.
After 1975, diversity patterns anong comnunities became more complex.
Each community responded differently. Species richness usually increased
but diversity and equltabllity decreased In some communities and increased
In others. It is believed that differences In diversity patterns can be
accounted for by the differential"behavior of a community's dominant species
responding to different types and magnitudes of disturbance.
Plant population data show that dominant species were not equally
sensitive to flooding, heat stress, or increased surface water flow. Sons
species such as ۥ lacuetrne and C. rostmta, were extremely sensitive,
declining rapidly and dramatically in all communities. Other perennial
species, such as C* etricta and Calama^roetie canadeneis, responded more
slowly, decreasing only after 1976. T* latifolia, on the other hand,
75
-------
increased continuously in the EMERGENT conniunlty and invaded all other
corimunl t ies ..
The population data also show that dominant species differed among
communities in their abundance and distribution. All of the above-
mentioned species wore abundant prior to disturbance. All except C.
r>osti\ita and 7". lati folia were widely distributed. However, C. rostrata
was abundant in only the TRANSITION and EMEKGF.NT communities. T.
latifolia was restricted for the most part to the EMERGENT community. In
the CAREX LACUSTRIS community, C- lacuBti'ie was co-dotni nant with C*
stricta. C. stricta clearly dsrainated the CAHSX STRICT* community. The
TRANSITION cor-munity had no single dominant. C. canadcnsis and 'C. stricta
were nearly equal in relative abundance withC. poetrnta and C. lacuetrie
only slightly less abundant. The EMERGENT community- -though locally
dominated by 7". Zati.foZia--contained large relative abundances of C?.
roatrata and C*
Cnraraunlties dominated by sensitive species exhibited different
temporal trends than did those communities in which dominant species were
tolerant of the stress or favored by it. In the CARl\ LACUSTRIS and CAtiEX
STRICTA communities, species richness, diversity, and equitability
increased after 1975, more so in the CAREX LACUSTRIS community than the
CAREX STRICTA community. The increases coincided with the decline of C.
lacustrie , which was eliminated fror.i both communities by 1977. The slight
differences in the magnitude of the response appear to be related to the
greater sensitivity of C. lacustvis and its greater abundance in the CAREX
LACUSTRIS comrmilty compared with the greater tolerarcc o f C. etricta. and
its dominance in the CAREX iX"i\ICTA cc'-xiunity . More habitat was made
available for new or expanding species by the proportionately greater
decrease in populations of C. lacxetrie in the CARSX LACVSTR'S community.
Species richness, diversity, a-.id equitability in that community all
increased to near or above 197't values.
In contrast, diversity declined further and equir.ability remained low
in the EMERGENT community after 1975, despite Incre^sus in species number.
Two tolerant species, £. minor and T. latifolia., increased continuously
through 1977, while other species declined in abundance. Diversity and
equitability decreased as disturbance increased the relative dominance of
Lernna and Typha,
The pattern of response in the TRANSITION corariunlty followed the fate
of sensitive and tolerant dominant species. Species number, diversity,
and equitabiiity declined less rapidly from 197;'; to 1975 than other
communities due to the balancing of increases and decreases among the
dominants depending on their sensitivity to flooding «nd high surface
water flow. Major decreases In diversity and equitability occurred from'
1975 to 1976 as L. minor became exceedingly dominant. Diversity increased
after 1976 following the decline of C. lasuetrie and C. roetrata. The
addition of a number of species to the community — us colonization space
became available with the decline in dominant species — accounted for the
increase.
76
-------
The ecological stgnlficancc of community patterns of response Is not
evident from the diversity data alone. Do uniform relationship was
observed between diversity and intensity of disturbance. The different
diversity measures sometimes varied independently and showed decreases and
increases with disturbance. Decreasing values in the EMUIUIE'JT community
did not correspond to a greater degree of disturbance than in the S£L)GE
MEADOW communities. Increasing diversity values in the SEDGE MEADOW
communities after 1975 did not indicate a recovery process or return to
pre-impact composition or structure. Examination of the population and
community data showed that return of diversity values to near or above
pre-impact values paralleled the continuing decline of dominant perennial
sedges and their replacement by annuals or short-lived perennials as the
magnitude and spatic.l scale of disturbance increased.
Considered together, the Columbia population and community data sets
show that increases in diversity under non-equillbrlun conditions may
represent continuing disturbance rather than recovery of the system or
"advance" In successional stage brought about by establishment or comf--.-ti-
tlve interactions of long-lived perennials. Diversity measures oust be
interpreted in light of population data and the behavior of dorainnnt
species. Diversity theory is not sufficiently well-developed for non-
equilibriuir. connunllies for vegetation changes to be evaluated on the
basis of diversity -oeasures alone (Caswell 1978, Green 1979).
77
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SECTION 4
SEASONAL CHANGES III PHENOLOGY AND CARBOHYDRATE KES-iRVF.S OF
TYPHA LATIFOLIA AMD CARKX LACUSTRIS IWULATUWS SUUJECT TO
ALTERED TEMPERATURE AND FLOODING PATTERNS
INTRODUCTION
The wetland plant st"dy of th«* Colunhi.i Proji-ct was nndert aken to
monitor vegetation changes associated with leakage from tho cooling lake of
the Columbia Electric Generating Station. Results of the monitoring program
showed significant vegetation changes within 1 yr of Colu.-nbia station
operation (section 3, Bedford 1977). However, freshwater wetlands in the
upper Midwest may undergo natural shifts in species composition and
structure without being subject to human-induced envtronnciUal. influences
(Bedford et al. 1974, Van der Valk and Davis I973b, We 11or and Fredricl;son
1974).
The research goals for this study had to go beyond documenting the
resultant changes in communities to understanding hou exogenous disturbances
affected the actual process of change. Such studies are essential if field
techniques are to be developed for determining In advance of facilities'
development the probable effects of waste heat and ulev.ited groundwal.er
levels on wetland plant, communities. The principal research objectives
included determination of:
1. Causal mechanisms potentially relating vtj.et.itIon changes t<;
environmental variables that could be associated with leakage from
the cooling lake.
2. The magnitude of effect resulting from known levels and combina-
tions of environmental factors produced by leakage from the cooling
lake.
3. Ecologically based criteria by which significant Impact to wetland
plant communities could be recognized, monitored, and predicted in
the field at the species level, given particular factor levels lor
the environmental variables.
Meeting these objectives required characterizing the sequential field
behavior of individual species responding to stress, i.e., identifying the
various stages and associated mechanisms in the course of population
response for individual species.
78
-------
This paper reports the seasonal response of Typha lc.tifolia and Carex
populations to nslld heat, and water stress as measured by monthly
data on shoot number, height, and chlorosis. It examines alterations in
plant phenology and corresponding changes in amounts of carbohydrate stored
in or depleted from rhizomes, shoots, and shoot bases as the causes of
population decline.
The mechanisms controlling population dynamics of perennial rhizoraatous
species were hypothesized to be heat-induced variations in plant phenology
and plant metabolism. It was thought that vegetation changes related to
waste heat would be exhibited by variations In temperature-regulated
phenomena: 1. Metabolic processes, such as photosynthesis, respiration, and
translocation of photosynthate; .'ind 2. plant phenology, such as timing of
shoot emergence, growth, and dieback.
Specifically, it was hypothesized that winter grouridwater temperatures
in excess of those normally prevailing during periods of winter dormancy for
Wisconsin wetland plants would result in: 1. Exhaustion of energy reserves
stored in underground organs and over-wintering shoots of dominant perennial
plants; 2. altered timing of shoot emergence, growth, and dieback; and
3. subsequent population decline.
Perennial wetland plants of northern latitudes generally follow a cycle
of accumulation of photosynthetic products during the growing season, high
levels of storage (with some depletions) during winter dormancy, followed by
rapid translocation and depletion of stored energy reserves during spring
growth. Temperatures out of phase with normal cycles o! plant growth alter
temporal patterns of plant growth, and the storage or depletion of reserve
materials. Wetland species such as cattail (Typha spp.) allocate a large
percentage of their bioroass production to over-winter reserves of non-
structural carbohydrates stored la rhizomes (Gustafson 1976). The
importance of these reserves for early spring growth has been shown for
Typha by McNaughton (1974), Llnde at al. (1976), and Gustafson (1976) and
postulated for Carex rostrata by Bernard (1974). Bernard and Bernard (1973)
further stressed the considerable significance of winter bloraass in wetland
ecosystems. Heat-induced high rates of winter respiration or winter shoot
emergence depletes the energy supply required for spring shoot emergence and
growth, thus reducing shoot number and causing population decline.
METHODS .
Selection of Species
Two species (T. latifolia and C. lacuetrie) were selected for study on
the basis of field observations of species response, data from semi-annual'
vegetation sampling (section 3, Bedford 1977), a review of literature
pertaining to the autecology of species dominant In the Columbia wetlands,
and field studies of measurement techniques to determine feasibility for use
with a particular species.
On 1 April 1976, qualitative field observations were Initiated to
characterize seasonal behavioral responses of individual plant species in
79
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localized areas subject '-.o temperature changes. During twice-weekly field
Inspections phonological data (e.g., onset of shoot emergence, flowering,
1 raiting, and dieback) and obvious changes IP plant vigor (e.g., chlorosis
or loss of turgor) were noted. Observations were used to determine key
field characteristics of species response to altered temperature and
indentify sensitive species e.xnibiting cl<>ar and obvious field signs of
stress. . . .
Data from the 1974 and 1975 semi-annual vegetation sampling were used
to determine which spec.tes were of sufficient importance in the Columbia
wetland communities to affect significantly the course of community
response. Criteria for selection included dominance in a single community
or abundance in more than a single community.. . .
A review of the literature was undertaken to: i. Ascertain the
importance of particular species in wetland systems, and 2. obtain
information on the autecology and potential physiological response of
specific wetland plants to changes in water temperature, water levels, and
surface flow patterns. Existing information on life history and phenology
of undisturbed populations was of particular .interest. This could be used
as a guide in experimental design and as a standard against which to
evaluate species respon-.e on rhe Columbia site (Bedford et al. 1976 for
Carex spp., Bedford 197'J for Typha}.
Having made a preliminary selection on the basis of the above criteria,
small-scale field studies were conducted to determine the feasibility of
using those species for the proposed approach. The study site and nearby
wetlands were reconnoltured to locate control and treatment stands of
similar density and of adequate area to permit repeated sampling of species
aeeting this crtteila. The rhizomes of six were excavated and washed to
determine collecting and washing time, as well as the possibility of
separating rhizomes fron other plant parts and dead organic matter.
Feasibility criteria included:
1. Existence of a control population located off-site with stand
density similar to on-site population stands,
•)
2. All stands of 25 m minimum area,
3. Rhizomes, shoots, and shoot bases readily identifiable and
separable from orher plant parts,
4. Cumulative collecting time for all stands < 7 days under winter
conditions, < 3 days for October conditions, and < 2 days for May
conditions,
5. Hashing time for each sample < 4 h.
Location of Sampling Sites
As is usually the cade when working under field conditions, an ideal
statistical design with simultaneous controls on all variables was not
80
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possible. Ideally, sampling sit.es should be selected to cover tlie possible-
range and combinations of environmental factors. However, the number and
spatial distribution of adequate Tjpha and Carex stands constrained the
n^nber of available sites. .No site was subject to. temperature increases
without the associated continuous saturation or flooding of the sotl
surface. Control sites were'subject to neither change. Further, .-it the
tine of site selection, fine-scale infornation on the temporal and spatial
•distribution of .disturbance factors was not available. Therefore, a
combination of available hroad-scale information and actual field responses
.o.f Typha and Cavex as indicators of environmental conditions was used .to
select sites that represented what was. believed to be the existing, range" of
mean water levels and temperature increases on the Columbia site. Distance
from the west dike of the cooling lake and winter ice conditions also were
•used'as indicators of temperature patterns. In.general, temperature
increases attenuated with -increasing distance from tho dike. The location
of sampling sites and characteristics known at the time of selection are
summarized in Table 4 for five Carez sites and five Typha sites, including
controls. •. •
Plant Phenology
Shoot number, height, and chlorosis were selected on the basis of 197o
field observations as obvious field characteristics that could bo easily
measured at several sites on a repeated basis. Measures ot each of these
characteristics were recorded monthly in 15 random 0.2 m circular «juadrar.s
at each of five sites for Typha and four for C. lacueti+ie frou Februar to
October 1977 and from March to July 197S. A fifth site was added for: C.
lacustvis in September 1977 and used only for pli.enoLogic.il data. All live
shoots were counted. Height was measured as distance from the so:1 surface
to the tip of the longest leaf. Chlorosis was determined qualitatively in
three broad categories: 1. Most shoots retaining color, < W.', chlorosis
evident; 2. most shoots retaining none color, 40 to 80^ chlorosis jvidL>nt;
3. most shoots retaining little to no color, > 80/i chlorosis evident.
Carbohydrate Reserves
All rhizomes, r.hoot~ bases, and new shoots within four 0.07 ra"" quadrats
were collected at each of the same five "T'jpha sites and four Car-fix sites in
January, May, and October 1977, and January 197S. Time of sampling was
determined using Bernard's life history data on C. lasuetr*is (Bernard and
MacDonald 1974, Bernard 1975, Bernard and Bernard 1977, Bernard and Solsky
1977) and the work of Custafson (1976) and Linde et al. (1976) on T'jpha
phenology and carbohydrate reserves. Saopiing was scheduled to coincide
with mid-winter carbohydrate storage (January), during spring shoot
emergence and growth (late May), and just after the onset of dormancy, when
reserves should be at a maximum value (late October). A chain saw was used
to obtain frozen samples and a metal cover for non-frozen samples. Frozen
samples were returned to the laboratory, thawed at room temperature, and
washed to remove soil and extraneous plant debris. Non-frozen samples were
washed Immediately on site or transported in ice chests containing dry ice
to the laboratory for washing. All identifiable rhizomes, shoots, and shoot
bases or parts thereof were retained intact after washing. These were
81
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TABLE 4. LOCATION A.ND CHARACTERISTICS OF SAMPLING SITES
Sampling
area
01
02
"03
04
05
06
07C
08C
09
10
Distance from
Species3 west dike (m)
C.
jr»
\* *
T.
T.
T.
T.
T.
C.
C.
C.
lacuetrie
lacuetvie
latifolia
latifolia
latifolia
latifolia
latifolia
lacuetris
lacuetrie
lacuetris
50
50
25
350
325
150
off-site
off-site
25
50
Mid-winter Temperature
condition increase
F
0
0
F
0
0
F
K
0
F
Moderate
Moderate
Maximum
Mi.iiraum
Minimum
Moderate
None
Hone
Maximum
Mi niraum
Mean water
level (cm)
< 10
< 10
< 10
10 to 20
10 to 20
10 to 20
< 10
< 10
10 to 20
< 10
a(7. lacuetria is Carex lc.cuetri.6, T. latifolia Is Typlia l^tifolia.
F is frozen, 0 is open water.
cControl sites.
82
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wrapped in aluminum foil, submersed for several minutes in liquid nitrogen
to stop metabolic activity, and stored au < 0°C,
Prior to laboratory analysis, samples were thawed at tootr temperature,
dried for at least 48 h in a forced-air oven at 70°C, weighed, and ground In
a Wiley mill. The modified Weinmann method of Smith (1969) was used to
quantify total nonstructural carbohydrates.
Environmental Factors
Water depth, surface water temperature, and substrate temperature at
each quadrat sampled were recorded for shoot counts and carbohydrate
reserves. Water temperatures were taken 15 era below the water surface or
just above the soil surface if water depth was < 15 cm. Substrate
temperatures were taken 15 cm below the soil surtace. Both temperatures
were measured using .a glass mercury .thermometer or a Reotemp, Inc. 60 cc.
metalprobe thermometer.
Snow and Litter Remova) Experiment^
A snow and litter retJioval experiment was conducted in the winter of
1977 to 1978 in order to determine the,effects of exposure on overwintering
shoots of £'• lacuetris. Fifteen 0.2 m quadrats were randomly selected in
fall 1977 at a control site and permanently parked with wooden stakes. All
detached litter was removed from the quadrats by hand; all standing dead
vegetation was clipped to an even height of 50 cm above the soil surface.
Clipping closer to the soil surface would have reraoved or damaged live fall
shoots. Shoot number, height, and condition were recorded for each
permanent quadrat and for 15 randomly selected control quadrat* in the same
area. Snow was removed regularly, although not necessarily immediately,
from the permanent quadrats throughout the winter. Removal was conducted by
hand and with a soft brush to prevent physical damage to the shoots.
Measures of shoot number, height, and condition were repeated in late A.prf,i
for the 15 permanent quadrats and 15 randomly selected control quadrate
within the same area.
RESULTS
Selection of Species
Common cattail (T. latifolia} and the coro-non sawgrass or lake se-Jf.e (£.
tacu&trie) were selected for individual population study on the basis of
species field response, species importance within the study area and in
other wetland systems, and on the basis of feasibility. Results of field
observations, literature surveys, and feasibility studies are discussed
below.
Both species exhibited immediate and obvious response to leakage front
the cooling J.ake. A T. latifolia. stand within 25 m of the cooling lake dlV
remained green for several weeks after hard frcst in fall 1975. Field
observations in spring 1976 revealed that spring shoots failed to emerce wr
emerged sparsely. By raid-summer the stand appeared to have recovered,
83
-------
However, mature plants remained green Into early November, long after hard
frosts. New shoots emerged in October. Many of these exhibited extreme
chlorosis but retained turgor. Shoots of C. lacuetrie failed to emerge or
emerged sparsely in spring 1976 in areas where it had been abundant the
previous fall.
Both 3". latifolia and C. lacustrne are important species in the study
area and in wetlands in general. IT. latifolia is one of the most common and
widely distributed wetland plants in the northern hemisphere (McNaughton
1974, Sculthorpe 1967, Fassett 1957). Although not widely distributed in
the study area, it dominated localized areac where it did occur. By 1977,
Typha had increased in abundance and distribution except within 50 m of the
cooling lake. C* lacuetrie was abundant in five of six wetland communities
on the Columbia site prior to impact. By 1976, it had been virtually
eliminated in extensive sections of all communities. C. lacuetrie is common
in wetlands of the prairie pothole regions (Steward and Kantrud 1972), the
norcheast (Bernard and MacDonald 1974), and the upper Midwest (Bedford
et al. 1974, Swink 1974).
Both species are large, rhizomatous perennial species known to have
large winter ctanding crops (Bernard and Bernard 1977, Gustafson 1976). The
large size of rhizomes made collection and sorting of below-ground material
feasible.
Both specie:; have been studied extensively (Bernard and Gorhara 1978,
Midair et al. 1073 and 1976, Gustafson 1976). Data were available on life
history cycle, including seasonal patterns of shoot emergence, growth, and
below- and above-ground biomass (Bernard 1975, Bernard and Bernard 1977,
Bernard and MacDonald 1974, Bernard and Solsky 1977, Dykyjova et al. 1972,
Fiala 1971, Gustafson 1976, Jervis 1969, Linde et al. 1976, McNaughton
1974). Additional information on seasonal * ' .irns of carbohydrate storage
and shoot phenology for Wisconsin populati was available for T. latifolia
(Gustafson 1976, Linde et al. 1976).
Typha latifolic.
Environmental Factors—
Sampling sites for T» latifolia. covered a range of temperature and
water level conditions. Temperatures in the rooting zone at the control
site followed an expected seasonal pattern of winter freezing, spring and
summer wanning, a fall cooling (Figure 35). Substrate temperature patterns
for sites west of the cooling lake varied in magnitude and seasonal
distribution with distance from the lake. In general, magnitude and
temporal patterns of temperature changes were attenuated with Increasing
distance from tha lake. Water levels were continuously above the surface
and fluctuated < 6 cm at all sites, but differed in mean value. Mean water
level at the control site was 8.3 ± 5.4 cm (s.d.).
Area 03, located within 25 m of the west dike, exhibited the greatest
temperature increase and departure from normal seasonal temperature patterns
(Figure 36). Mean substrate temperature in January was ^15°C, i.e., 15°C
84
-------
15-1
ID-
S'
0.
"
o 15
§10-
Is-
3> n .
C?
•o
8
3
2 15
s.10.
CU 0*
«5 3 "
o>
S
15
ID-
S'
0.
5
Area
t03
•
w _
i i i
• • • - • - I
04
17 ± 5.2cm
MI t «a H
1 ' ' Br ^ ^ ' ' ' II ' • T . T -1 ..
05
20- 4cm
Ii
i^_I 1 S! 5 _
-n^ ^•^^•g
06
17. §1 3.5cm j
MM 9 mm H H H
• •-Pi ^il I mm m
J»n Feb Mar Apr May Jun Jul A'ug Sep Oct Nov Dec Jan Feb M«r Apr May Jun Jul
1977 _.t_ 1978
20
•10
r20
" E
-10 «
»-
0^
Q.
0)
•u
0)
-20 n
. ?
CO
s
r20
•
•10
.
n
Figure 36. Temperature patterns in the substrate and mean water levels
(+s.d.) for Typha latifolia sites. Note that temperature is
represented as degrees above or below control site values.
85
-------
above control site temperature. Late April substrate temperature fell to
below control site temperature. Temperatures rose in late summer and fall
to exceed control site temperatures by 11 to 17°C. Mean water level was 8.3
± 4.0 cm (s.d.).
Area 04, located "o 350 m from the west dike, unexpectedly showed some
temperature alterations (Figure 36). The site remained frozen throughout
the winter but had late spring substrate temperatures 6.8°C above control
site temperatures. Mean water level was 17.0 ± '5.2 cir (s.d.).
Although located % 325 ra from the west dike, Area 05 did not freeze in
winter 1977 (Figure 36). High water flow kept the area open. Except for
winter open water conditions, temperature patterns in Area 05 were similar
to those in Area 04. Mean water level was 20.0 -t 4.0 cm (s.d.).
Area 06, %150 m west of the dike, experienced almost continuous slight
temperature elevation (Figure 36). The area had open water conditions in
January and early March, but substrate temperatures were < 2°C above control
site freezing temperatures. The greatest temperature increase (^ 5°C above
control) occurred in early May. Mean water level was 17.8 ± 3.5 cm
(s.d.). Rapid water movement through the area wis evident throughout the
year.
Carbohydrate Reserves—
Undisturbed sequence-—Carbohydrate values in rhizomes of T. lat-ifolia
at the control site (Area 07) fell within expectud seasonal values for
undisturbed Wisconsin star.ds (Figure 37). The January 1977 mean at the
control site compared closely to values reported by Gustafson (1976) and
Linde et al. (1976) for south-central Wisconsin stands of 7*. latifolia at
the end and beginning of the growing season. Gustafson obtained mean values
for % TNC in cattail rhizomes of 45.Ot in early April and 40.6% in early
October. The October mean is the average of Gustafson's (1976) mean values
for 1973 .and 1974 rhizomes. Since rhizomes were not separated into age
classes, GUPtafson's values were averaged here and in Figures 37 and 38 for
comparative purposes. Linde et al. (1976) reported similar though somewhat
higher values for raid-April and late September. It was inferred that the
value obtained at the control site (43.8%) reflects normal over-winter
carbohydrate levels. The carbohydrate mean for the control site dropped as
expected during spring shoot growth and rose again by the beginning of
winter dormancy to a value (48.72) close to those reported by Gustafson
(1976) and Linde et al. (1976). The January 1978 nean for the control site
(31.6%) is considerably lower than the 1977 it.san, but well above seasonal
low values. An unusually high proportion of old rhizomes and low number of
Typha culms observed in the samples may explain the low value. Linde et al.
(1976) reported that the lowest TNC storage occurred in the distal portion
of old rhizomes, ^L 33% compared to the January 1978 value of ^ 32%. A
fourth sample was dropped from calculation of the mean because it contained
an unusually low biomass of rhizomes, > 95% of which were badly decayed.
The randomly placed quadrat had contained no aboveground Typha culms. The
control site initially and throughout the study had a lower density of
aboveground shoots than all other stands. The probability of a randomly
86
-------
60
SO
f>4°
5
•030
fi?
10-
O Aral 07 Control
• Area 03
. Llnde, e! al.data (1976)
. Gustafson date (1976)
\°
\
\
Jan F«b War Apr May Jun Jul Aug Sep ' Oct Nov ' Dec ' Jan
Date 1978
Figure 37. Seasonal changes in total nonstructural carbohydrates for the
Typha control site (Area 07) and Area 03 compared with values
reported in Linde et al. (1976) and Gustafson (1976).
87
-------
D Are* 07 Control A Are* 04
• Area 03 A Area OS
O Area 06 Gusiafson data
60i
50-
£
o>
•40
Z
20-
10
o
A
O
O
\
\ A
\ 1 '
\ / •
\ .x / o
/ *
\. /"
\ o /
\ /
» .
"\ /
\ /
o
1
Jan ' Feb ' Mar ' Apr ' May jun T Jul ' Aug n Scp ' Oc!^ ^ Jon ^
1978
Figure 38. Seasonal changes in total nonstructural carbohydrates for
the Typha control site (Area 07) and four other sites compared
with Gustafson (1976).
88
-------
placed quadrat falling between culms and the proximal portion of rhizor.es,
therefore, was higher than for other sites.
Response to waste heat la winter—Midwinter carbohydrate (Z TNC) values
for rhizomes of cattail plants subject to h'i'gh winter temperatures were
significantly lower than those for the control site (Figure 37). January
1977 TNC levels at *r. a 03, where mean substrate temperature was 15°C,
approached the lowest levels reported by Gustafson (1976) and Lino- et al.
(1976) for the entire growing season. Such low levels normally flu: reached
only during active growth when photosynthesis can compensate for rjspira-
tion.
Rhizomes of plants in Areas 05 and 06 experienced only mildly elevated
winter temperatures (1.4 and 1.8°C, respectively). January 1977 TNC levels
were correspondingly lower than values for the control site and Area 04,
which remained frozen. However, mean % TNC for both sites was well above
storage values at Area 03 (Figure 38).
The hypothesis that warn, winter temperatures result in low carbohydrate
reserves is supported by the overall seasonal pattern of carbohydrate:
storage in Area 03 (Figure 37), October levels did not support an alter-
native hypothesis that warm summer temperatures result in lov; winter
carbohydrate reserves by decreasing the sumiuc-r product ion: respiration
ratio. By late October,.rhizomes in Area 03 contained 38.64 TMC, just below
Custafson's (Iy76) value of 40.1% for toe sane time of year in an undis-
turbed stand. Under warm fall and winter teraperature-s (Figure 36), TNC
again dropped, this time to a mean of < (>/„ TN'C.
The 1978 winter data for Areas 04, 05, and 06 also point Co a direct
relationship between groundwater temperatures ana TNC deplection in T>
Ic.tifolia. By 1978, substrate temperatures at these sites were warmer than
1977 temperatures. January 1978 TN'C levels were correspondingly lower. The
greatest depletion (excluding Area 03) occurred at Are.- 06 where tempera-
tures were higher in fall and winter than at either Area 04 or 05. Although
winter 1978 substrate temperatures in Area 06 (X = 4.8°C) averaged only
3.0°C higher than 1977 values and < 2°C above Areas 04 and 05 in 1978, TOC
levels were significantly lower than 1977 values and 1978 levels for Area 04
and 05. Since winter carbohydrate depletion is probably a function of
cumulative temperature (Stewart and Bannister 1973), warmer temperatures iri
late fall after photosynthesis ceased and the early winter at Area 06 likely
account for the differences.
The TNC values in Typha shoot bases followed patterns similar to
rhizome patterns. The means and standard deviations for both are presented
in Appendix B-l.
Response to other changes in temperature—Temperature increases during
spring, summer, and fall, in the range observed at the sampling sites (1 to
13°C), apparently did not produce a negative effect overall on growing
season TNC balances or account for decreased plant size or population number
in 2". latifolia.. High Hay temperatures were correlated with significantly '
lower TNC levels than t'.iose at the control site, and plants at Columbia
89
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sites all had lower fall TNC values than the control site. However, three
of the four sites (Areas 03, 05 and 06) showed a greater net Increase from
May to October than the control site. All sites accumulated >^ 30% TNC In
rhizomes by October (Figure 38) despite elevated spring temperatures, low
spring TNC levels, and a range of temperature changes from May through
October 1977 (Kigure 36). Furthermore, Typha plants at Areas 04, 05, and 06
all attained apparently normal shoot height (Figure 39) and shoot density
(Figure 40) during the 1977 growing season. Only Area 03, which was subject
to winter temperatures J>_ 15°C, showed significantly reduced plant height and
number by June 1978. (See below for data on shoot height and number).
Differences between sites in fall TNC values did not relate directly to
fall groundwater temperatures. Differences may indicate the Interaction of
positive and negative effects of temperature on different plant processes at
different times of the growing season. Fall carbohydrate levels in rhizomes
represent a balance of photosynthesis, growth, respiration, and
translocation processes throughout the growing season and monthly data on
each of these varibles in lacking.
Responses to othor environmental factors—Water level was not found to
be a critical variable in Typha carbohydrate storage in the study area. T.
latifolia is a known hydrophytlc species which does well in shallow water
and under continuously flooded conditions (Linde et al. 1976, Sculthorpe
1967). Mean water level increases on the Columbia site were small ('MO
cm). Three of the sites had nearly equal mean water depths and the fourth
differed by only 10 cm. All values were within the favorable range for
cattail.
It cannot be concluded from the TNC data that winter open water without
increased temperature had a significant effect on carbohydrate storage in
Typha.. Area 05, which was in all other ways similar to Area 04, did not
have significantly different TNC levels except in October.
Plant Phenology—
Undisturbed sequence—Although formed below the soil surface, most
Typha shoots usually do not emerge above the surface until spring (Bernard
and Bernard 1977). £.fter initial shoot emergence in April to early May,
shoot numbers stay fairly constant through out 'the growing season (Gustafson
1976). Shoots elongate rapidly sometime during late April to late May,
after whicVi their height increases steadily through mid-July. Mean height
remains at or about this value until senescence (Gustafson 1976, Linde
et al. 1976). Typha shoots in the control area for this study generally
followed this pattern.
Response to waste heat in winter—Typha shoots emerged early in Area
03, where January and March temperatures were significantly above the frozen
conditions at the control site (Figure 36) (See Figure 48). Shoot density
decreased with onset of the growing season. Apparently *"he reported low
January carbohydrate levels were insufficient to support spring shoct
emergence and growth. By mid-May, the stand had not attaiaed & shoot
density comparable to the previous season's density, the control site, or
, . 90
-------
180
170-
160-
150
140
E 130
O
»• too
Gj
2
5
< 80
60'
40
20
Areo 03 O- -O
Areo 04 O—O
Areo OS &—&
Arer 06 9 V
Areo 07 D—D
• i -i ii | r. r | | • f • r JV^** J~"'" '*••*«——i*r.. • • n|'i mrrn
Feb Mar Apr May Jun Jul Aug Sep Oct Feb Mar ' Apr ' May Jun
4QVT — . -tO TO
1977
Date
1978
Figure 39. Average height (cm) of Typha latifolia shoots at control and
four other sites. Closed symbols show heights of newly emerged
shoots.
91
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O——O Area 03
O— —O Area 04
A A Area OS
-v Area 06
-Q Area 07
35
30
-2S
§20
£
M
O
a
So
O
a>
5-
Jan Feb 'Mar Apr May Jun' Jul Aug Sep Ocl ' Nov Dec JanTFeb 'Mar^Apr 'May ' JurT
1977 1978
Date
Figure 40. Seasonal changes In shoot density (mean number of shoots/
quadrat) for Tyyha Lain folia at control and four other sites.
92
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other sampling areas. Shoot number fluctuated throughout the growing season
but never exceeded .tha number of shoots present In early March. Although
the October rhizomes of these plants contained near normal TNC
concentrations, high winter temperatures reduced TNC levels to < 3% by
January 1978. Only a few shoots emerged late in May 1978. Shoot number
dropped to zero by the end of June.
Responses to other changes in temperature—Temperature increases of
< 10°C during the growing season did not result in extensive chlorosis,
reduced plant size, or shoot mortality in T. lat-ifolia. Elevated spring and
fall temperatures altered shoot phenology but did not reduce population
density significantly during the sampling period reported here (Figure
40). Shoots in Areas 04, 05, and 06 tended to gain height more quickly in
spring (Figure 39) and remain green later in fall (Figure 41) than did
shoots at the control site. Other phonological changes included early
spring shoot emergence and fall shoot emergence. In general, extensive
chlorosis did not oc-iur at these sites during the growing season. An
unexplained decrease in shoot number at Areas 04 and 06 and an unexplained
increase at Area 05 occurred from late June to mid-August (Figure 40).
Otherwise, changes i-i shoot emergence, growth, and loss of chlorophyll
generally were correlated with increased groundwater temperatures.
Typha shoots at all Columbia sampling sites remained greener longer in
fall than did control, site shoots. Significantly smaller proportions of
shoots at all Columbia sites were > 80% chlorotic by 15 October 1977 than at
the control area (Figure 41). Shoots closer to the west dike (Areas 03 and.
06) were somewhat le?s chlorotic than shoots > 300 m from the dike (Areas 04
and 05).
The data contain minimal information on the effects of mid-summer
temperature increases and below-normal temperatures. Significant changes in
summer groundwater temperatures occurred only at Area 03, where the effects
of high winter temperatures already were evident. High August temperatures
at Area 03 were correlated with a Irop in shoot number but the relationship
between the two events is not clear. Shoot number also dropped from July to
August at Areas 04 and 06 where temperature increases were minimal.
Below-normal groundwater temperatures occurred at some sites in late
April, early July, and mid-October 1977 and in late May and June 1978
(Figure 36). Changes were < 3°C and no relationship to shoot phenology
emerges from the present data analysis.
Response to other environmental factors—Changes in onset of shoot
emergence and delayed dieback in T. latifolia do not appear to be correlated
to water levels at the Columbia site. Different patterns of response were
observed in sites with essentially the same mean water depth and variation.
93
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60-1
50-
40-
30-
s
o
i
A
o
o
o 20
10-
Q Control
O Area 02
O Area 04
A Ana OS
V Area 06
10 15 20
Mean number of total shoots / m2
25
Figure 41. Typha latifolia shoots exhibiting >80% chlorosis on 15
October 1977 at control and four other sites.
9A
-------
Carex lasuetrie
Environmental Factors--
The range of conditions covered at the C. lacuetrn-e sampling sites was
more limited than at the Typha sites hecause of the distribution of C.
lacustrne stands of adequate density and sampling area. Because appropriate
stands were located near the cooling lake at distances ranging only from 25
to 50 m, all sites experienced temperature elevations in the range found at
only one Typha site; differences between sites were minor in terms of the
magnitude of these increases. Seasonal patterns, however, differed
substantially due to the combined effect of distance and variation between
sites in compostion and depth of subsurface materials. Because of the time
lag introduced by movement of cooling lake water through underlying peats
and clay of different depths, the time at which the rooting zone temperature
reached maximum varied between sites by as much as 5 months. The most
extreme differences between sites occurred in winter when substrate
temperatures ranged from 0 to 16°C. Seasonal temperatures at the control
site followed the expected pattern of winter freezing, spring and summer
warming, and fall cooling (Figure 35).
All sites except the control experienced the same approximate increase
in mean water level (10 cm) after the cooling lake wai filled in the winter
of 1974 to 1975. Although the r.ew mean level differed from site to site,
the range was < 13 cm and all sites west of the cooling lake were subject to
continuous soil saturation or flooding. Portions of the control site, with
a mean level of 2.8 ± 2.7 cm (s.d.), were not saturated in late summer.
Areas 01, 02, and 09 all experienced temperature elevations of similar
magnitude (Figure 42). Seasonal variation departed most markedly from
normal seasonal patterns at Area 09. Substrate temperatures in Area 09 were
highest in winter and lowest in mid-summer. Mean substrate temperature in
January 1977 was > 16°C above the control site's freezing conditions. July
and August temperatures were nearly 4°C below control site values. Mean
water depth also was greatest at Area 09 (X = 12.0 ± 5.2 cm (s.d.)).
Area 02 also exceeded control site substrate temperatures by ^ 16°C.
However, this value was not readied until May. January temperatures were
only slightly above freezing. Temperature and continuous surface water flow
kept the area from freezing throughout winter 1977. Mean winter level (9.6
± 2.6 cm (s.d.)) was lower than that at Area 09.
Seasonal temperature variation in Area 01 was similar to Area 02, but
the magnitudes of the temperature elevations were lower. Area 01 remained
frozen through winter 1977. Mean water level was 3.1 •£ 2.6 cm (s.d.).
Area 09 was located within 25 m of the west dike. Areas 01 and 02 were
^ 50 m from the dike and Ideated in the area of the marsh with the deepest
peat deposits (1 3 m). Area 09 was located in the are? of shallowest peat
deposits (< 1 m) (Andrews 1976).
95
-------
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1977 «_._ 1978
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Figure 42. Temperature patterns in the substrate and mean water levels
(+ s.d.) for Carex laoustris sites. Note that temperature is
represented as degrees above or below control site values.
96
-------
Site 10 was added after the sampling program began when the limited
range of conditions at sit<:s 01, 02, and 09 became apparent. It had been
excluded previously because of inadequate sampling area for repeated rhizome
collections. Substrate temperatures at area 10 showed only minor departures
from control, site temperatures. Mean water level was 6.9 ± 2.6 cm (s.d.).
It was located 60 m from the cooling lake.
Carbohydrate Reserves—
Undisturbed sequence—No data were available on seasonal carbohydrate
patterns for C1. lacuetr*is at the time the study began. Bernard's (1974)
biomass data for
-------
r.
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u
36-
30-
24-
18-
12-
6-
54-
48-
42-
36-
30-
24-
18
12-
6-
COHORT 1
COHORT » * COHORT J
B
OLD
NEW
May Jun Jul Aug Sep Oct Nov Dec
Month
Figv:.e ,J. Seasonal changes in percentage of total
ncmstructural carbohydrates (+ 1 S,E.
indicated by vertical lines) in above-ground
(A) and below-ground (B) tissues of Cares:
lacustris (from Roseff and Bernard 1979).
98
-------
3CH
to
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o
~ 20
or
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A—-n& Area 09 <25m from dike
O-—O Area 01 ~50mfrom dike
o o Area 02 ~50mfrom dike (winter flow)
a a Area 08 Control
JFMAMJJASONDJ
'77 '78
Figure AA. Seasonal changes in total nonstructural carbohydrates
in rhizomes of Carex laous^is at control and three other sites.
99
-------
non-carbohydrate bloraass In the samples, therefore, was greater; the
proportion of TNC in the total sample was lower.
Rhizome TNC data for the control site agreed with Roseff and Bernard's
(1979) data in showing spring drawd>wn and fall build-up of reserves.
Between May and October, TNC levels at the control site rose 18% to a high
of 31% in late October compared with an increase of 15.7% to an October high
of 45.4% for the New York population.
Seasonal carbohydrate levels in newly emerged « 50 cm) shoots at the
control site (see Figure B-2) varied little except in late Kay when
concentrations dropped to a low of 2.8%. January 1977 (11.9%), October
(11.6%), and January 1978 (11.4%) values were approximately equal.
TNC levels in aboveground tissues were measured only for newly emerged
shoots. Comparisons with Roseff and Bernard's (1979) data are limited,
therefore, to data for fall-emerging shoots. Shoots at the control site
maintained approximately the same concentration (11.6%) from Octot-oc to
January, as did the New York population (16%), b;.
-------
appear to be the direct result of temperature changes during the 1977
growing season fFigure 42). The TNC patterns and temperature patterns
during the 1977 growing season did not correspond to each other. Despite
the fact that May groundwater temperatures at all sites west of the cooling
lake were 7 to 16°C higher than at the control site. TNC levels were all
within 62 of each other and the control site value. Temperature patterns
from May to October 1977 were more similar between Areas 01 and 02 than
between Areas 02 and 09. The TNC patterns from May to October were more
similar between Areas 02 and 09 than between Areas 01 and 02.
On the bas'.s of TNC and phsnological data, the 1977 failure of C.
lacustrie to accumulate TNC In rhizomes and shoots seems to be the indirect
result of temperature effects during the 1976 growing season and during
winter 1976 to 1977 on abpvegrpund shoots. The overall sequence of response
suggests that reductions in aboveground photosynthetic material—e.g.,
number of individuals, size of individuals, and chlorophyll content—which
had already occurred by May 1977 and continued through October, were the
cause and not the result of low TNC levels in October 1977 and January 1978.
Postulations about the relationship between 1977 TNC patterns and
temperature changes during the 1977 growing season can be inferred only from
existing data. Monthly data on transpiration and photosynthesis rates are
lacking. It is possible that high transpiration rates induced by elevated
growing season temperatures exceeded photosynthetic capacity. However, the
similarity in response between Areas 02 and 09 and the lack of
correspondence between summer temperature patterns at these two sites da not
support this hypothesis.
Response to other environmental factors—It is not possible on the
basis of the short-term data collected to eliminate mean water level or
continuous saturation of the soil surface as the important variables
affecting carbohydrate levels in C- lacuGtr>is. Response to water level and
seasonal fluctuation patterns is likely to be delayed (Bernard 19.75, Mathiak
1971, Millar 1973) and act indirectly on carbohydrate levels.
It is inferred from the data that mean water level itself was not a
critical factor in determining carbohydrate storage and depletion. This
tentative conclusion is based on: 1. The two areas with most similar mean
water depth (Control, X = 2.8 ± 2.6 cm (s.d.) and Area 01, X = 3.1 ± 2.6 cm
(s.d.)) had widely divergent carbohydrate trends, and 2. TNC levels declined
across a range of water depths (X = 3.1 ± 2.6 cm (s.d.) to X - 12.0 ± 5.2 era
(s.d.)). Furthermore, water levels at the onset of sampling were at
equilibrium for 2 yr (Andrews and Anderson 1980).
Continuous soil saturation cannot be dismissed as a critical factor. •
All the Columbia sites were continuously saturated and, therefore, likely to
be anaerobic. The control site probably experienced at least some periods
when the soil was aerobic. The tolerance of C. lacustrte to continually
anaerobic sediments is not known. However, the persistence of (7. lacuetrie
in areas of the Columbia site that were saturated but not subject to either
winter open water or elevated temperatures leads to the conclusion that.
101
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continual saturation of the soil surface is not sufficient to produce the
marked population decline of C. lacuBtris scan at the sampling sites.
Plant Phenology—
. Undisturbed sequence—The life history strategy of C. lacustrie differs
markedly from that of T- lati-folia according to Bernard and MacDonald
(1974), Bernard (1975), Bernard and Bernard (1977), and Bernard and Solsky
(1977) on New York populations. C. lacustrie is unlike Typha in its
seasonal patterns of shoot emergence, its extensive mortality during the
growing season, and in the amount of living biomass aboveground in winter.
Most of a given season's population emerges in fall of the previous year.
These shoots overwinter, remaining < 50 era in height, resume growth in
April, and die in late autumn. Additional shoots may emerge in April and
early May or after 1 July. Shoots which emerge before 1 October grow > 50
cm in height and die by winter. Most shoots emerging after 1 October do not
grow > 50 cm and overwinter. However, as Bernard (1975) pointed out, "If
some of the new shoots emerge early and grow too large, they also will
die." How long shoots live depends on time of emergence.
Unlike the pattern shown for Typha, several different cohorts of C.
lactustris shoots are present at any given time. Shoots emerge almost
continuously throughout the growing season and considerable mortality occurs
during the growing season. Total shoot number varies substantially with
maximum total number reached in early fall. Since a substantial number of
these fall shoots overwinter, aboveground winter bioaass is higher
proportionately than that of Typha. whose shoots remain below tl:-2 ground and
emerge in spring (Bernard and Bernard 1977).
The sequence of shoot emergence and dieback observed at tlni control
site (Figure 45) Was similar to that reported by Bernard (1975) and Bernard
and MacDonald (1974) in showing a major period of shoot emergence in fall,
maximum shoot number in fall,' substantial overwinter survival of fall- .
emerging shoots, and high growing season mortality. The sequence differed
in showing two major periods of shoot emergence: one. in fall—as Bernard
(1975) reported—and another in May 1977 or April 1978. A greater
difference between the number of fall shoots and the number or early spring
shoots also was observed. This may be due to greater overwinter mortality
in Wisconsin populations than in New York populations or may be an artifact
of sampling dates and frequency. Bernard and MacDofiaid (1974) reported that
of 344 live shoots/m2 in late October of which %65% (225 shoots/m2) were
new shoots. The data in this study were comparable. Approximately 64% (149
shoots/m ) of the total shoots alive at the control site in mid-October (232
shoots/nj2) were new shoots. However, by 1 April 1978 only 94 new shoots/m2
were present. Bernard and MacDonald (1974) found 231 shoots/ra2 in late
January. In other words, they found little or no mortality between October
and January while at Columbia there was ^40% mortality. Since Bernard and
MacDonald (1974) did not report data for the following April, and since
reliable shoot counts from January to 1 April 1978 were not completed at
Columbia because of snow conditions, the reason for the greater mortality is
not known. However, in 1977, 45% mortality occurred from late January to
early March at the control site (Figure 45). This is cotsparablc to the
102
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350-
325-
300-
275-
250-
225-
200-
175-
150-
125-
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. • Bernard's 1972-73 data
D D Area 06 Control
• • Ar«a 01
A A Area 02
• • Bernard's 1972-73 data repeated
O CArea 09
10
' I).
.C*"~
Jan ' Feb'Mar ' Apr 'May' Jun ' Jul ' Aug ' Sep'Oct ' Nov ' Dec Jan ' Feb' Mar <
1977 ^ 1978
Date
Figure 45. Seasonal changes in mean nuiuber of shoots/quadrat for Carex
lacustris at mean control (Area 08) and three other sites
compared with Bernard and MacDonald (1974).
103
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October 1977 to April 1978 mortality rate and suggests that substantial
overwinter mortality occurs in undisturbed Wisconsin populations.
Response to waste heat in winter—A substantial decrease in shoot
number occured from late January to early March at the C. lacuetrie sites,
including the control. However, areas subject to elevated winter
temperatures (Areas 02 and 09) experienced greater proportional loss than
did the control area and Area 01 which were frozen in January and February
1977. By early March, the control site and Area 01 lost 45 and 40% of
shoots present at the end of January. Areas 02 and 09 lost 73 and 74%,
respectively. Despite more than 10°C "differences in January and February
substrate temperatures at these sites, proportional losses were nearly
equivalent.
Winter shoots tended to be somewhat taller at sites west of 'the cooling
lake than at the control site (Figure 46). Differences in height were
related reore closely than shoot number to substrate temperature.
Differences between the control and Areas 01 and 02 were insignificant in
late January when temperatures were similar. March shoot heights were
related directly to temperature; warmer sites contained taller shoots.
Winter shoots at sites west of the cooling lake were significantly more
chlorotic than shoots at the control site (Figure 47). Like height, extent
of chlorosis was related directly to substrate temperature. Shoots at Area
09, which showed tlv; greatest departure from seasonal temperature patterns,
were significantly nore chlorotic than shoots at any other site. Early
March shoots were almost completely chlorotic. Shoots at the control site
exhibited only minor chlorosis. Shoots at Areas 01 and 02, where
temperatures were intermediate between the control and Area 09, showed
intermediate chlorosis.
The relationship between winter grojndwater temperatures, winter air
temperatures, shoot height, and chlorosis is not clear. Results of the snow
and litter removal experiment showed that winter exposure alone produced
extensive chlorosis in aboveground shoots. Winter exposure of shoots that
were rot subject to wlevated groundwater temperatures resulted in
slgnificaacly higher chlorosis than in nearby shoots protected by litter and
snow (Figure 48). Exposed shoots also tended to be taller. Of those shoots
that were expored, chlorosis was greater in the taller height classes.
Response to ether temperature changes—Departures from normal
phenological patterns continued to occur at sites west of the cooling lake
In spring, summer, and fall 1977. Shoot number increased from March to May
in Areas 01, 02, and 09 while remaining constant at the control site (Figure
45). Spring shoots tended to be taller and more chlorotic at sites west of
the cooling lake (Figures 46 and 47). From May to September shoot number
showed a net increase at the control site but dropped at all other sites.
Mature shoots in Areas 01, 02, and 09 were significantly shorter than shoots
at the control site (Figure 46).
104
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110-
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J«n ' Feb ' M«r Apr May ' Jun ' Jul ' Aug ' Sep ' Ocl ^
1977
Figure 46.
Date
1 Dec Jan Feb Mar Apr May Jun
1978
Seasonal changes in average height (cm) of Cayex lacustris
shoots at a control (Area 08) and three other sites. Closed
symbols show, heights of shoots _< 50 cm at time of sampling.
105
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1.0-1
Control
O Artd 01
A Arc* 02
O O Arc* 09
A A Aro« 10
03-
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1977
Figure 47. Seasonal changes in Carex lacustris shoots exhibiting
>80% chlorosis.
106
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120-
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Height of new shoots, cm
Figure 48. Number of Carex lacustris shoots exhibiting various degrees of chlorosis for
different size classes: (A) control area; (B) experimental area with snow and
litter removed.
-------
Fall shoots failed to emerge at all sites west of the cooling lake.
Remaining shoots were significantly more chlorotic than those at the control
site.
By winter 1977 it was clear that C. lacustr>is populations had collapsed
at all sampling sites west of the cpoling lake. Populations did not recover
the following spring.
In general, differences between sites In shoot number and height cannot
be explained on the basis of carbohydrate levels in rhizomes or shoots and
shoot bases. Only the failure of the fall 1977 cohort to emerge can be
correlated to TNC levels. Since the population was already severely
depleted by July 1977, it seems more likely that low October TNC levels were
the result rather than the cause of low shoot numbers.
The entire sequence of data indicates that winter conditions *lone do
not account for the decline of C, lacustr>ie. Instead of a sir.gle critical
response period related to carbohydrate reserves—as seen for T* lat'ifolia.—
C' lacuetrn.6 showed continuous departure from normal phenologies! 'patterns;
excessive winter mortality, increased spring emergence, summer decline in
shoot number, no fall shoot emergence, extremely high spring and fall
chlorosis, and taller new shoots but shorter mature shoots than at the
control site. However, the 1977 and 1978 data sees reveal only part of the
response sequence. Field observations and 1974 to 1977 survey dtita
indicated that population density had already been decreased whet: sampling
began in January 1977. Therefore, the effects of elevated spring, summer,
and fall groundwaler temperatures on a healthy population could not be
quantified.
Data from Area 10 contributed additional—though incomplete
information—on the potential effect of elevated groundwater temperatures on
fall shoots in an undepleted population. The size-class structure of the C*
lacuBtris population at Area 10 (Figures 49 and 50) indicates that minor
temperature changes can alter shoot emergence and growth patterns.
September and October substrate temperatures at Area 10 were only slightly
above control site values (Figure 42). A greater proportion of shoots at
Area 10 were in intermediate size classes (21 to 80 cm) and a smaller
proportion in shorter size classes (0 to 20 cm) than at the control site.
The average height in September of new shoots at Area 10 was 28.1 dt 25.1 cm
(s.d.) compared to 14.6 ± 18.9 cm (s.d.) at the control site. Total shoot
number in Area 10 dropped rather than increased from September to October.
Overwinter mortality was 16% higher than in the control area.
Data from Area 10—taken together with the 1975 increase in fall shoot
number observed in the area of major impact prior to the extreme drop in
1976 (Figure 15)—suggest that warmer than usual late summer and early fall
substrate temperatures may induce early emergence and growth of fall
shoots. Such alterations in normal phenological patterns could reduce
population numbers In three ways. As pointed out by Bernard (1975), shoot
life depends on time of emergence. If fall shoots that would otherwise
overwinter emerge early or grow too tall, thay die some time before
winter. Overwinter mortality may be somewhat higher for taller shoots
1C8
-------
40'
8 3S~
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Area 10-14 September 1977
~
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0 10 11 70 21-30 31 40 41 SO SI «0 (1 70 71 10 81 90 41 100 101 110 in 120 121 130 131 140 141 ISO 1S1 ir.0 161
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Area 08-11 September 1977
0 10 11 70 21 30 . 0 «1 SC SI (0 tl 70 71 10 II 90 91 'CO 101 110 11< 1JO 121 130 131 140 141 1SO 1S1 1M 1t1 179
Height of shoot, cm
Figure 49. The fall size-class structure of the Carex lam.3tris population at Area 10
compared to the control site (Area 01'.) populations (September 1977).
-------
Area 10-15 October 1977
0-10 11 20 21-10 31 40 <' SO 51 £0 61 70 71 >0 81 90 91 100 101 110 111 120 121 130 131 140 141 150 151 1(0 1ft 170
O
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Area 08 - 15 October 1977
hrrrri
0 10 11-20 21 30 31 40 41 50 SI «0 61 70 71 80 it 90 91 '00 IQt 110 111 120 12: 130 131 140 141 ISO
H-icht c? --f:oct , cm
<«0 Iti 170
Figure 50. The fall size-class structure of the Carex Lacuntris population at Area 10
compared to the control site (Area 08) populations (October 1977).
-------
exposed aboveground to winter air temperatures. Exposure-induced chlorosis
in overwintering shoots combined with high fall a:'.d winter mortality may
reduce the population's overall photosynthetic capacity to the point where
it is insufficient to support growth, carbohydrate build-up during the
growing season, or fall slioot emergence.
The response of C* Ic.suetriB cannot be attributed to a single critical
period or mechanism. Differences between C. lacv.strie sites in shoot number
cannot be explained on the basis of prevailing winter substrate tenpratt-res
or TNC levels in rhizomes and shoots. Although the data analysis is not
conclusive, it seems that population decline in C* lacuetris occurred as a
result of the combined effects of continuously altered timing of shoot
emergence and growth during the previous growing season (1976) and greater
than normal overwinter mortality.
Response to other environmental factors—Although increased water
levels, high surface water flow, and continous soil saturation probably
contributed to the decline of C* lamiBtris, the departures from undisturbed
seasonal patterns of shoot emergence, growth, and dteback seen at all
sampling sites cannot be attributed to these factors. Several pieces of
evidence from Areas 01, 02, 09, and 10 suggest this conclusion. Area 10
showed only minor changes in phenology and population density by spring 1978
despite a mean water depth (7.0 ± 2.6 cm (s.d.)) greater than that at Area
01 (3.1 ± 2.6 cm (s.d.)). Both sites were continuously saturated since
1975. Area 01 showed majcr phenological changes !.>y spring 1977. Area 01
and the control site differed by < 0.5 era in mean water depth and monthly
variation. Water levels al all sites were below levels at which 0.
lacustris is known to survive (Auclair et al. 1973, Stewart and Kantrud
1972, Bernard, personal communication). Harris and Marshall (1963) reported
that A yr of continuous flooding to depths of 15.2 cm were necessary to
eliminate three species of sedges, including C. Ic.custrie. C. laaustrie was
eliminated in 3 yr in < 4 cm of water at Area 01 snd < 10 cm at Area 02.
Finally, Area 01 was not subject to surface water flow but showed
phenological changes similar to those seen in areas of high surface flow.
Changes in water level and flow Hkely contributed to the decline of C.
lacuatris in three ways. First, in limited, deeper areas of the marsh such
as the emergent community, the small increase in mean level may have
exceeded the tolerance rsr.ga of the species. Second, higher water levels-
may have caused higher mortality during the growing season by increasing the
proportion of flowering shoots in the population. Bernard (1975) related
increased flowering to elevated water levels the previous year and reported
that "the amount of shoot mortality during the growing season depends to a
considerable extent on the number of shoots that flower." Third, increased
flow was sufficient in some parts of the marsh to prevent winter freezing
and to remove plant litter. Even without elevated groundwater temperatures
these factors could contribute to population decline by increasing exposure
of overwintering shoots. High surface flow also could alter phenological
patterns through earlier warming of the sediments in spring. Nonetheless,
the persistence of C* lacuetris in areas that did not experience elevated
grounduatp.r temperatures but that were subject to corstinous flooding cr
saturation of the soil surface eliminates water level and soil saturation as
111
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critical variables regulating the response of this species to leakage from
the Columbia cooling lake. The decline of C. lacustrns at Area 01—where no
surface flow occurred—eliminates surface flow as a single controlling
variable.
Data from Areas 01, 02, 09, and 10 did not permit the relative
contribution of hydrologic factors to be separated from the role of waste
heat in the collapse of C. Iacu6tr>-i>* populations. Increased substrate
temperatures, elevated water levels, and high surface water flow are
directly related to increased groundwater discharge and are not
independent. Near the cooling lake, where the heat has not dissipated,
these factors land to be interrelated. Areas 01, 02, 09, and 10 all were
located within 60 m of the west dike of the lake.
DISCUSSION AND CONCLUSIONS
T. latifolia and C. lasustrij fit the general hypothesis attributing
population decline to heat-induced variations in plant phenology and plant
metabolism, i?- lacuetr^Le did not fit the. specific hypothesis in regard to
tha regulating mechanism or sequence of response. Elevated temperature
patterns resulted in population decline through continuously altered shoot
phenology rather than through' winter depletion of carbohydrate reserves as
In T. latifolia. Furthermore, C. lacuetrie exhibited a greater sensitivity
to stress. The phenological data, population data, and field observations
showed that the magnitude of effect produced in C. lacuetrie by the various
levels of waste heat and elevated groundwater levels was greater than i'or
T. latifolia. Population data (section 3) showed an almost uniformly
negative response by C. lacuetrie but positive and negative responses by T.
latifolia. Typha exhibited a clear positive response to elevated water
levels, increasing its density where it had been abundant and expanding its
distribution substantially by 1977 (Figures 51 and 52). Adverse effects on
Typha were restricted to areas where temperature increases were > 7 to 16°C
and occurred in winter. Viable populations of C. laeuetfie persisted only
In areas where temperature increases were negligible throughout the year
(Figure 53).
Information on specific field signs of heat stress and general species
characteristics that may be useful indicators of potential sensitivity to
stress can be Inferred froa interspecific differences and. similarities
observed in the response patterns of C. lacuetrie and T. latifolia.
Similarities observed in the negative responses of both species identify
field charactersitics that can be used as specific signs for detecting and
monitoring heat stress ir. wetland plants. Interspecific differences in
regulating mechanisms, sequences, < lacuetri* and altered tiding of shoot
emergence In C. lacuetrie and T. latifolia. Comparisons between the two
112
-------
N Fioodplem Fotfsl
Nclh Knoll
4241 40 39V 38 J 3: 36 35 34 33 32 ~ 30 29 28 27 26 25 34
V/A Typha duttlbulion -1974
th«c -1877
lypb* invotion t \idtni
o> KtOlingt - 1977
LOWLAND TREES; onu SHRUBS
33 21 20 19 18 17 16 IS 14 U 12 It 10 9«76S 43? 1_
""^ ^~ Wt»i Dim "^ r~
Cooling Pond
Figure 51. Expanding distributions of Typha latlfolia between 1974
and 1977.
113
-------
I
1 r
• t
Figure 52. Typha latifolia in 1977 invading areas of the Columbia marsh
which Carex previously dominated.
114
-------
Figure 53. Decline of Carex lacustris population in Area 01
between April 1976 (A) anM April 1978 (B).
115
-------
species are con&traired by tho fact that sampling sites for Typha covered a
wider range of temperature changes than did Ca*v~ sites. Although seasonal
patterns differed ainong the Car^x sites, no sivu experienced a temperature
maximum < 14°C above the control site temperatures. Furthermore, the data
do not include measures of the seasonal redox st.uus of tho sediments. The
positive response of T^pha probably is related to its tolerance of anaerobic
conditions,
Phenological changes appear to be reliable indicators of heat stress
(Figure 54). Although changes in population density occurred throughout the
study area, phenologicdl changes were not observed outside the area affected
by altered temperature patterns. In areas receiving waste heat, individual
plants showed visible signs of stress before the population collapsed.
Where the species grew in dense stands, the symptoms were visible to the
naked eye at distances up to 300 n. In general, phenological changes baco.tie
evident 1 yr before population density was reduced and 2 yr before tho
population collapsed. Vadas et al. (I97b) reported similar changes for
Maine populations of Spar>t,ina al terni flora receiving waste heat.
Charactersitics of plants experiencing he»t stress that were observable
and easily measured in the field Included: 1. Unseasonable chlorosis,
2. reduced height of mature shoots, .3. increased height of new shoots, and
4. early or delayed shoot emergence at reduced density. Tlicsi' phonological
changes were evident in C* lacustriti throughout me year. Extensive
chlorosis did not occur i n T. lati-folia during tho growing season. In
general, phenological changes were r.ioro pronounceJ i:i C*
Different phonological changes, which did not lead to reduced popula-
tion density, were observed at -T'jp'ia. sites exper ien-i nr, lower temperature
increases and negligible, winter increases. They included: 1. F.arly spring
shoot emergence at previous densities, 2. rapid gain in shoot height during
spring elongation, and 3. delayed lost; of chlorophyll in fall. No negative
consequences to the populations were evident by June 197ii. Temperature
increases up to 7°C in spring, summer, and fall appeared merely to extend
the effective growing season for 71. luti folia . The data suggest a subsidy
effect rather than a stress (Odum et al. 1979).
The greater magnitude of effect observed in C- lac'ustric appears to be
related to itc particular life history characteristics. The following lines
of evidence available frora Bernard (1975) and Bernard and MacDonald (1974)
and the results of this study support such a hypothesis. First, a substan-
tial proportion of the population is in younger age classes at .nost times of
the year. Many .aquatic organisms have been shown to be more susceptible to
heat stress during early developmental stages. Second annual population
size in C* lacustris is dependent on shoot emergence the previous fall and
the overwinter survival of this cohort. Thus, a high proportion of the
population's biocass and carbohydrate reserve is above ground in winter
where it is susceptible to exposure If increases in temperature or water
flow rates prevent ice formation and snow cover or remove litter cover.
Third, the life span of an individual shoot depends on time of emergence and
fail Height. If members of the fall cohort emerge early or grow too tall as
a result of temperature changes they will r.ot survive the winter. Fourth,
116
-------
: ai
f ,. ., ^ 777 "r«*7T| £|t
«• • ; fcj**1
'•"• 4* >. '••/!'
-4*iMv- >y* '^^
riiilf'v -wwS-- v .v'^tf-- ».i A »J
I^$S
ffi^-=.;F*f
M
MSSȣ
„ '..J W
S-^-*:^!.-^1"
V
^•k
->*»K
;^?i»
-iHK.'»'^H «>,Kflf;
Figure 54. Areas of open water (A) and exposed mudflats (B) that have replaced the closed and densely
vegetated perennial plant communities (C).
-------
minor increases in temperature on the Columbia sice altered the timing and
growth of late summer- and f al l-eir,erging shoots. The net effect of these
characteristics appi-srs to be population that is sensitive to heat stress
throughout the year and if corroborated by the data. Unlike T> latifolia,
C. lacuetris showed visible signs of stress throughout the year. C.
roetrata—a species with similar life history characteristics (Pernard and
MacDonald 1974, Berr.ard 1977, Bernard and Solsky 1978)—showed a similar
response.
It is well known that plant species differ in their sensitivity to
different kinds of disturbance. The results of this study suggest that
species tolerance or senstivtty is a consequence of the species life history
cycle and the timing, as well as the magnitude of the disturbance. The
characters!tic response to disturbance and the associated population
consequences of three broad life history "stragegies" (syndrones) have been
outlined by Grime (1977). Leith (1970), Bliss (1967), and Bernard and
Gorham (1978) have pointed out the importance of phenological character-
istics in determining species and community productivity. Erhlich and Holm
(1962) suggested tn.-.t species be grouped according to their ecological
requirements. Aru.n.il (Stearns 1977) and terrestrial plant ecologists
(Harper 1977) have conducted considerable research on life history charac-
teristics in equilibrium communities. Environmental biologists should
examine the concept of life history as a theoretical tool for predicting
species sensitivity to disturbance and assessing the probable effects on
wetland plant communities.
Previous studies (Harper 1969, Luhr.henco 1978) and the population and
toanunity data fron section 3 indicate '.hat exogenous disturbance affects
the process of vegetation change at the community level through the differ-
ential sensitivity of the dominant species. The results of this study
suggest the importance of phenology in species response. The likelihood of
predicting the response of dominant species would be enhanced by knowing the
key charactersitics of its life cycle. These should include life span, the
schedule of various; phenophases, seasonal distribution of biomass between
above- and below-ground parts, abilif/ to regenerate or colonize, and repro-
duction and mortality schedules. Grouping species with similar sets of life
history traits, especially temporal charactersitics, may identify meaningful
aggregate variables (Orians 1980) for environmental inpact assessment
between the level of the individual species and the coramunity.
118
-------
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vegetation dynamics of prairie glacial marshes. Ecology 59(2):322-335.
126
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Walker, B. H., and C. F. Wehrhahn. 1971. Relationships between derived
vegetation gradients and measured environmental variables in
Saskatchewan wetlands. Ecology 52:85-95.
Walker, D. 1970. Direction and rate in some British postglacial
hydroseres. pp. 117-139. In D. Walker and R. West (eds.) The
Vegetational History of the British Isles. Cambridge University Press,
Cambridge, England.
Wang, J. Y., and V. E. Sounii. 1957. The phytoclimate of Wisconsin. I. The
growing season. Research Report 1, Agricultural Experiment Station,
University of Wisconsin, Madison, Wisconsin. 22 p.
Wang, J. Y., and V. E. Soumi. 1958. The phytoclimate of Wisconsin.
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Environmental Protection Agency, Cincinnati, Ohio.
Weller, M. W., and L. H. Fredridcson. 1974. Avian ecology of a managed
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Wisconsin Department of Natural Resources. 1973. Final Environmental
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Wisconsin.
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Wynn, S. L. 1979. A comparison of data collection and analysis methods
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Ph.D. Thesis, University of Wisconsin, Madison, Wisconsin. 435 p.
Wynn, S. L., and R. W. Kiefer. 1977. Monitoring vegetation changes in
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127
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APPENDIX A
PLANT COMMUNITY DATA
Symbols used are defined as follows:
S is mean nunber of species per quadrat.
S is total number of species for all quadrats sampled:
S and S are neasares of species richness
n
H' - -I p In p (1)
where
H1 is the Shannon-Vjener diversity index (Feet 1975) combining
species richness and the distribution of abundances of
individuals in the different species, and
^ is the proportion of total number of individuals contributed by
species i
T = H* H' ...
J H1 In S (2)
max
where
J is the distribution of abundances in terms of their evenness or
equitability and is the opposite of dominance, if J is low,
dominance is high, and
Hlmax is the maximum value of H1 for the given number of species j(S)
(Pielou 1975).
128
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TABLE A-l. SUMMER DATA FOR FOUR PLANT COMilWUT.lKS BEFORE (1974) AND
FOLLOWING DISTURBANCE (1975 TO 1977) FOR AREA OK MAJOR IMPACT.
Sampling
period
1974
1975
1976
1977
1974 to 1977t
Community data including standard deviation
S S
CAREX LACi'STRIS COMMUNI
5.88 ± 2.06 26.00 ± 0.00
4.08 ± 1.20 18.40 *• 0.55
4.96 ± 2.08 22.80 ± 2.86
7.46 i 3.82 31.00 ± 3.39
+1.58 +5.00
H1
TV
2.36 ± 0.00
1.6S ± 0.01
1.70 ± 0.20
2.13 ± 0.08
-0.18
J
0.72 ± 0.00
0.58 ± 0.00
. 0.54 ± 0.00
0.63 i 0.00
-0.09
CARSX STRICTA COMMUNITY
1974
1975
1976
1977
1974 to 1977t
1974
1975
1976
1977
1974 to 1977t
1974
1975
1976
1977
1974 to 197 7t
5.00 ± 1.16 19.00 ± 0.00
4..7S -fc 2.26 18.00 ± 0.00
5.83 ± 3.02 18.80 ± 2.59
7.06 ± 1.98 21.60 ± 2.88
+2.06 +2.60
EMERGENT COMMUNITY
3.38 ± 1.50 18.20 ± 1.10
4.12 ± 1.36 11.00 ± 0.00
3.38 ± 1.20 12.60 ± 2.07
4.38 ± 1.97 14.00 ± 1.22
+1.00 -4.20
TRANSITION COMMUNITY
5.40 ± 2.22 - 15.00 ± 0.00
•i.05 ± 1.57 12.80 ± 2.59
4.20 ± 1.00 11.20 ± 0.84
5.09 ± 2.20 18.80 ± 2.28
-0.31 +3.80
2.20 ± 0.00
1.43 ± 0.00
1.61 ± 0.08
1.84 ± 0.16
-0.36
•
1.87 "± 0.09
0.89 ± 0.00
0.80 ± 0.08
0.77 ± 0.08
-1.10
2.06 ± 0.00
1.62 i 0.16
1.04 ± 0.10
1.38 ± 0.12
-0.68
0.75 ± 0.00
0.49 ± 0.00
0.55 ± 0.01
0.60 ± 0.06
-0.15
0.64 ± 0.02
0.37 ± 0.00
0.32 ± 0.03
0.29 ± 0.02
-0.35
0.76 ± 0.00
0.64 ± 0.05
0.43 ± 0.04
0.47 ± 0.03
-0.29
tNet change.
129
-------
TABLE A-2. ' FALL DATA FOR FOUR PLANT COMMUNITIES BEFORE (1974) *:;D FOLLOWING
DISTURBANCE (1975 TO 1977) FOR AREA OF MAJOR IMPACT
Sampling
period
Community data including standard deviation
S
S
H'
J
CAKEX LACVSTRIS COMMUNITY
1974
1975
1976
1977
1974 to 1977t
4.10 ± 2.02
4.86 ± 1.56
3.96 ± 1.70
4.14 ± 2.05
40.04
21.00 ± 0.00
16.80 ± 0.45
15.40 ± 2.30
19.80 ± 2.39
-1 .20
1.90 ± 0.00
1.51 ± 0.23
1.46. ± 0.12
1.57 ± 0.16
-0.33
0.62 ± 0.00
0.51 i- 0.04
0.53 ± 0.04
0.53 ± 0.04
-0.09
CAREX STRICTA COMMUNITY
1974
1975
1976
1977
1974 to 1977T
1974
1975
1976
1977
1974 to 197 7t
1974
1975
1976
1977
1974 to 1977T
4.90 ± 1.66
4.88 ± 2.45
4.00 ± 2.09
4.06 ± 2.07
-0.84
5.20 ± 1.81
4.15 ± 1.35
3.19 ± 1.13
3.17 ± 1.90
-2.03
5.00 ±2.11
4.64 ± 1.33
.4.09 ± l.Ji
3.10 ± 1.10
-1.90
16.00 ± 0.00
16.60 ± 1.52
13.40 ± 3.78
11.60 ± 1.82
-4.40
EMERGENT COMMUNITY
19.00 ± 0.00
14.40 ± 0.55
9.00 ± 1.58
5.20 ± 1.30
-13.80
TRANSITION COMMUNITY
12.00 ± 0.00
llcOO ± 0.00
8.60 ± 1.14
10.30 ± 1.92
-1.20
1.60 i 0.00
1.67 ± 0.06
1.25 ± 0.07
1.15 ± 0.08
-0.45
1.74 ± 0.00
1.29 ± 0.06
0.74 ± 0.13
0.41 ± 0.05
-1.53
1.70 ± 0.00
1.65 ± 0.00
1.15 ± 0.09
0.69 ± 0.15
-1.01
0.58 ± 0.00
0.60 ± 0.02
0.49 ± 0.05
0.47 ± 0.02
-0.11
0.66 ± 0.00
0.48 ± 0.02
0.34 ± 0.04
0.26 ± 0.06
-0.40
0.68 ± 0.00
0.69 ± 0.00
0.51 ± 0.08
0.29 ± 0.05
-0.39
•
tNet change.
130
-------
TABLF. A-3. SUMMER DATA FOR riVhl PLAJiT COM.ll"ilT Li;S B^FORC (1974) AND
FOLLOWING DISTURBANCE (1'J75 TO 1977) FOR UNTIRFC AREA
•
Sampl ing
period
S
Community data Including
S
standard
H1
deviation
J
CAREX LACVSTKJS COMJIUNITY
1974.
1975
1974
1975
1974
1975
5
4
5
4
3
3
.40 ±
.20 ±
.60 ±
.50 ±
.90 ±
.60 ±
1
L
1
1
1
I
.93
.51
f
\r
.74
.71
.49
.11
41.00 ± 0.00 -
29.20 ± 1.64
7AREX STRICT A COMMIT 1
46.00 ± 0.00
42.80 ± 1.79
EMERGENT COMJtUNITY
31.20 ± 0.80
16.00 ± 0.00
2.57
2.18
TY
2.66
2.22
2.23
1.12
± 0
± 0
± 0
± 0
± 0
± 0
.00
.05
.00
.03
.03
.00
0
0
0
0
0
0
.69
.65
.69
.59
.05
.40
dt 0.00
± 0.01
± 0.00
dt 0.01
± 0.01
± 0.00
TRANSITION1 COMMUNITY
1974
1975
1974
1975
5
3
6
4
.30 ±
.90 ±
.10 ±
.60 ±
1
1
2
1
.89
.40
.28
.63
26.00 ± 0.00
19.20 ± 2.77
SPIRAEA COMMUNITY
30.00 ± 0.00
20.80 ± 0.84
2.55
1.91
2.53
1-97
± 0
± 0
± 0
± 0
.00
.13
.00
.06
0
0
0
0
.78
.65
.74
.65
± 0.00
± 0.02
± 0.00
± c.oo
tNet change.
131
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TABLE A-4. FALL PATA FOR SIX PLAiiT COMMUNITIES BEFORE (1974) AN!) FOLLOWING
DISTURBANCE. (1975 TO 1977) FOR EN'TIRF. AREA
_— _____ — __ __-«—«— — — -.
Sampling
period
1974
1975
1976
1977
1974 to 1977t
1974- -
1975
1976
1977
1974 1:0 197 7t
1974
1975
1976
1977
1974 to 1977t
1974
1975
1976
1977
1974 to 197 7t
1974
1975
1976
1977
1974 to 1977t
1974
1975
1976
1977
1974 to 197 7t
Coraniunity data including standard deviation
S S .11 ''
CAHEX LACUSTHIS COMMUNITY
5.27 ± ?.01 34.00 ± 0.00 1.44 ± 0.00
5.14 ± 2.14 30.20 ± 3.11 1.95 ±0.12
3.88 ± 1.31 28.20 ± 1.92 1.72 ± 0.06
4.52 i 2.08 30.00 ± 1.53 1.66 1- 0.10
-0.75 -4.00 +0.22
CAREX STRICT A COMMUNITY
!».22 ± 1>&5 38.00 ± 0.00 1.83 i 0.00 -
4.72 ± 2.06 46.40 ± 5.94 1.92 ± 0.12
3.77 ± 1.47 23.20 ± 1.30 1.63 ± 0.04
3.87 ± 1.58 34.00 ± 2.74 1.50 ± 0.09
-1.35 -4.00 -0.33
EMERGENT COMMUNITY
i. 84 ±1.50 30.00 ± 0.00 2.03 ± 0.00
3.95 ± 1.24 21.40 ± 1.95 1.49 ± 0.07
3.24 ± 1.16 14.40 ± 0.55 1.27 ± 0.05
2.94 ± 1.32 14.20 ± 1.10 0.74 ± O.C7
-1.90 -15.80 -1.29
TRANSITION COMMUNITY
5.38 ± 1.92 18^00 ± O..QO 1.97 ± 0.00
4.89 ± 2.23 21.60 ± 0.55 1.88 ± 0.04
3.76 ± 1.45 16.00 ± 1.73 1.31 ± 0.04
3.51 ± 1.58 31.60 ± 1.67 1.29 ± 0.16
-1.87 +13.60 -0.68
SPIRAEA COMMUNITY
5.12 ± 2.36 28.00 ± 0.00 2.30 ± 0.00
4.04 ± 1.91 20.60 ± 1.52 1.99 ±0.02
4.58 ± 1.68 25.60 ± 1.67 1.72 i 0.04
5.00 ± 1.86 24.40 ± 2.07 1.76 ± 0.09
-0.12 -3.60 -0.54
LOWLAND SHRUBS AND TREES
5.44 ±1.67 37.00 ± 0.00 2. 12 ±0.00
4.35 ± i;62 41.40 ± 3.36 1.94 ± 0.20
3.93 ± 1.46 28.20 ± 0.84 1.84 ± 0.07
.3.84 ± 1.69 32.40 ± 3.78 1.73 ± 0.21
-1.60 -4.60 -- -0.39
- J
0.41 -t 0.00
0.57 ± 0.02
0.51 ±'0.02
0.49 ± 0.02
+0.08
0.50 ± 0.00 .
0.51 ± 0.02
0.50 ± 0.01
0.42 ± 0.02
-U.08
0.60 ± 0.00
0.49 ± 0.02
0.48 ± 0.02
0.28 ± 0.03
-0.32
0.68 ± 0.00
0.61 ± 0.02
0.47 ± 0.02
0.37 ± 0.05
-0.31
0.69 ± 0.00
0.66 ± 0.01
0.53 ± 0.02
0.55 ± 0.03
-0.14
0.55 ± 0.00 •
0.52 ±0.05 -
0.55 ± 0.02
0.50 ± 0.04
-0.09
tKet change.
132
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APPENDIX B
TOTAL NONSTRUCTURAL .CARBOHYDRATE CONTENT OF
TYPHA LATIFOLIA AND CAHEX LACUSTRIS
133
-------
60-i
2 50-
O)
J 40-
i
13
'* 20-
O
z 10-
Area u/-^onuoi 60
Ii ' 1
11 40"
•} i r
n '
i '
•
30-
' 20-
I
Area uj
IT
i
• ]• .
V I
T T
v I
Jan May Oct Jan . . Jon May Oct •. Jan •
1977 1978 1977 1878
60-
£ 50-
01
3 40-
| 30-
°_ 20-
0
JE -o-
A/eo 04 6o n
50-
I. .. T ..
I 11 L
a. -1-
.,0-
20-
T I ' JL. 10'
Area 05
T
T . . . I.T . .
i n
i ti
• T 1
^ :
.Jon May Oct J:n ' Jen May Oct Jon
1977 1S.'8 1977 1978
60-
. •• ..' '• ' . .£-50-
Ol
3 40-
£30-
5?
- 20-
- • O
Area 06
" . ' ^ -• Rhizomt*
T
J - Shoot*, bii«»
H .... 5i .T . ,'.-,.
i-
i
Jon . May OcS Jan
1977
Date
197e
Figure B-l. Total horistructural carbohydrates (%TNC + s.d.) H« rhizomes,
shoots, and shoot bases of Typha lat-ifolia at control (Area 07).
and four other sites.
134
-------
9 Rhlzomo
$ Shoott. baBot
Area 08 -Control
30-
20-
•o
* 1.
o
J-l
Jan May Oct Jan"
1977 1978
Area 01
30-i
20-
10
H
I
Jan May Oct Jan
1977 1978
Area 02
30-
£
O).
t 20-
•o
o 10-
z
y
I
J_
I,
I, I'
Area 09
Jan May Oct Jan
1977 . 1978
Date
30-i
20-
10
n
Jan May Oct Jan
1977 1«7B
Date
Figure B-2. Means and standard deviations for percent total
nonstructural carbohydrates in rhizomes and shoot bases
of-Carex lacustris at three sites and a control (Area 08).
135
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