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.                                   .

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     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.

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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

-------
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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'/ '
1 	 i ^ -
•^ -t^ ^ l^i^^^^ ***^*^
B
T 80-
70-

T 60-

\ I 50 "
N
i
T lT 30'
i
1 20-
^S*
10-
	 0 .

S'F1
1977

E 80-

T 70-
| 60-
j * - 5.J
Is r,"
lj :
t^
J. w
1C
i T '
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1



F IS ' F 1 S' F 1 S' F 1
1974 1975 1976 1977

F

T
l
• !
I T T
,lA L
i ' \L^1
l^tff
• •
  F'S'F'S'F'S'F'
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

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     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

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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

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                                                            \
        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

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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

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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

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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

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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.

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      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

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  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.

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     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.

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  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.

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   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.

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      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

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                                                                                 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

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   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

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     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

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                                       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

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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

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      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

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   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

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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.

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      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-

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   46-i
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  2.6-
  2.0-
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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
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                  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
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      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
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     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

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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

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                                                 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

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  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.

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     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

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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

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     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

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     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

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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

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15-1
ID-

S'
0.
"

o 15
§10-
Is-
3> n .
C?
•o
8
3
2 15
s.10.
CU 0*
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Area
t03
•
w _ 	
i i i
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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

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-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 /
\ /
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"\ /
\ /
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

-------
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
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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

-------
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

-------

15

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5
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M 	 _
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Jan Feb Mir Apr May Jun Jut Aug Stp Oct Nov Dec Jan Feb Mar Api May Jun Jul
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.
          O)
          '5
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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

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    3CH
 to
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~  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

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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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O
tr
o
o
o>

O
9)
350-

325-

300-

275-

250-

225-

200-

175-

150-

125-

100-


 75-

 so-

 25-
               .	• 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-

  100-

   90-


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   70-

01 60-
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   30-

   20-

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O	Q Aral 08
O	O Ar«i 01
^	^7 Ar«» 02
ft—O Ar«« 09
A	A Ar«a 10
       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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I

8*
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                                                  TV
                                                 If
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                          ,«,  V/
                          /   ^   */ '
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M      \ /    /
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             /
            /
                 -V	D
          Fob  ' Mar  '  Apr  """Jmy  '  Jun  '  Jui   '  Aua  '  Sep  '  Ocl  *

                                   1977
 Figure 47.  Seasonal changes  in Carex  lacustris shoots  exhibiting
              >80% chlorosis.
                                     106

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  A.
         0-5 B-10 lt-15 16-20 21-2526-30 31-35 36-40
                                                        120n
                                                        100-
                                                         80-
                                                         60-
                                                         40-
                                                         20-
B.
                      [   | Norm«l

                      JX\1 40-80% Chlorotlc

                      £~~l > >0% Chlorotlc
                                                                0-5  6-10 11-15 16-20 21-25 26-3031-35 36-40
                              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.

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     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

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   40'



8  3S~
n

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   20-1




~  IS
Area 10-14  September 1977
                   ~

                                                    ~
        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
   40-
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   15-
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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).

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                                                                                        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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iti
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    •1
                                                                                       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).

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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

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            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

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                                                                          I

                                                                          1  r
                                                                          •  t
Figure 52.  Typha latifolia in 1977 invading areas of the Columbia marsh

            which Carex previously dominated.
                                     114

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Figure 53.  Decline of  Carex  lacustris population  in  Area  01
            between April  1976  (A) anM April  1978  (B).
                             115

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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
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                                                 ^•k
                                               ->*»K
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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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                                     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

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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

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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

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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

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                             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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