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A COMPARISON OF CYPRESS ECOSYSTEMS
IN THE LANDSCAPE OF FLORIDA














By

Sandra L. Brown



















A DISSERTATION PRESENTED TO THE GRADUATE CGUJNCIL OF
THE UNIVERSITY OF F..".
IN PARTIAL FULFILLMENT OF TiiE REQUIR-MENTS FOR THE
DEGREE OF DCCTO(R 3F ?HILOSOPHY


UNIVERSITY OF FLORIiD

S97q














ACKNOWLEDGEMENTS


I am especially grateful to my major professor, H. T. Odum, for his

guidance, encouragement and insight; and to my supervisory committee:

S. Bayley, B. Capehart, K. Ewel, W. Huber and A. Lugo for their many

suggestions.

F. Wang advised on water modeling. S. Cowies gave initial instructions

on the use of the metabolism equipment. M. Kemp, J. Zucchetto, T. Dolan,

B. Walker, L. Shapiro, E. Flohrschutz, D. Hornbeck, R. Costanza and

M. Brown helped in the field. J. O'Conner, who was an undergraduate

assistant, helped with data collection and analysis of the metabolism

measurements. P. Straub, D. Mau and S. Neas helped with laboratory and

data analysis. J. Truelson contributed chlorophyll data from work done

on a summer project for high school students (Future Florida Scientists)

during 1976. Assistance with the tree core analyses was provided by

M. Burnett and M. Duever. Permission to work at Morningside Park Dome

and Prairie Creek was given by P. Weinrich and W. Halback respectively.

Finally, I am indebted to my friends and colleagues, especially J.

Nessel, P. Kangas and R. Costanza, for stimulating interchanges of ideas.

This research was supported by the RANN Division of the National

Science Foundation Grant ENV 73-07823A02 and The Rockefeller Foundation

Grant RF 76034 to the Center for Wetlands: Cypress Wetlands for Water

Management, Recycling and Conservation, H. T. Odum and K. C. Ewel,

principal investigators.









The land use map for the Green Swamp was prepared in collaboration

with R. Costanza and M. Brown. Research for the Green Swamp hydrologic

model was supported by the Florida Department of Administration, Division

of State Planning Contract #M74-30317: The Green Swamp Study: H. Merritt

and C. Kylstra, principal investigators through a subcontract to the

Center for Wetlands.















TABLE OF CONTENTS


Page


ACKNOWLEDGEMENTS ii

LIST OF TABLES viii

LIST OF FIGURES xv

ABSTRACT xxi

INTRODUCTION i

Physiological and Morphological Adaptations of
Wetland Species 2
Previous Studies of Forested Wetlands 6
Plan of Study and Objectives 12
Description of Study Sites 16
Cypress Wetlands 16
Green Swamp Region 27

METHODS 34

Field Measurements 34
Hydroperiod 34
Plant and Community Metabolism and
Evapotranspiration 35
Instrument Calibration 47
Data Reduction and Calculations 52
Forest Structure 62
Plant Biomass 63
Plant Surface Area Relationships 66
Chlorophyll Analyses 69
Plant Species Diversity 70
Litterfall 70
Tree Growth 71
Optical Density 72
Nutrient Analyses 77
Reproduction Potential o" Cypress 79
Regional Data 79
Land Use Mapping 79
Water Budget 80
Modeling and Simulation Methods S5









TABLE OF CONTENTS Continued


Page

RESULTS 95

Field Data 95
Hydroperiod 95
Metabolism, Transpiration and Evaporation of
Forest Components 98
Correlation of Transpiration Rates with
Saturation Deficits of Air 173
Effect of Air Speed on Metabolism 176
Forest Structure 188
Plant Biomass 202
Plant Surface Area Relationships 207
Chlorophyll Analyses 216
Plant Species Diversity 221
Litterfall 226
Tree Growth 232
Optical Density 239
Hemispherical Photographs 246
Nutrient Analyses 253
Reproduction Potential of Cypress 266
Regional Data 268
Land Use and Land Use Map 26
Water Budget Data 274
Simulation of Regional Water Model 285
Model Validation 285
Simulations 290

DISCUSSION 300

Comparison of Cypress Ecosystems 300
Dwarf Cypress 300
Cypress Domes 302
Floodplain Forest 306
Total Phosphorus Budgets 307
Forest Structure and Biomass 311
Forest Structure 311
Biomass 313
Organic Budgets 316
Gross Productivity and Respiration 316
Balance of Gains and Losses of Organic Carbcn 325
Community Efficiencies 331
Comparison of Metabolism with Other Forest Types 331
Adaptations of Chlorophyll for Maximizing
Photosynthesis 336
Duckweed Productivity 340
Annual Litterfall and Wood Production 341
Total Transpiration and Evaporation 344









TABLE OF CONTENTS Continued


Page

Adaptations for Water Conservation 348
Transpiration Rates 348
Morphological Adaptations 351
Role of Wetlands in the Landscape 355

APPENDIX A: KEY TO THE SYMBOLS USED IN THE MODELS 360

APPENDIX B: DESCRIPTION OF THE EXTRACTION PROCEDURE FOR
PHOSPHORUS ANALYSES OF SEDIMENTS AND
VEGETATION 362

APPENDIX C: LAND USE CLASSIFICATION 364

APPENDIX D: SUMMARY OF DATA USED TO CALCULATE AGGREGATED
CURVE NUMBERS (CN) FOR THE GREEN SWAMP 369

APPENDIX E: DIURNAL GRAPHS OF CARBON AND WATER EXCHANGE

APPENDIX F: SPATIAL ARRANGEMENT OF TREES IN THE VICINITY
OF THE METABOLISM EXPERIMENTS AND IDENTIFICA-
TION OF THE FOREST COMPONENTS ON WHICH THE
METABOLISM MEASUREMENTS WERE MADE 496

APPENDIX G: INDICES OF GROSS PHOTOSYNTHESIS AND 24-HOUR
RESPIRATION FOR CYPRESS, HARDWOOD AND
UNDERSTORY LEAVES 509

APPENDIX H: REGRESSION EQUATIONS FOR BRANCH AND TOTAL WOOD
BIOMASS AND HARVEST DATA FOR THE BIOMASS
REGRESSIONS 513

APPENDIX I: DISTRIBUTION OF LEAF BIOMASS IN THE FOREST
CANOPIES 523

APPENDIX J: BOLE AND BRANCH SURFACE AREA DATA FOR POND-
CYPRESS AND GUM TREES 526

APPENDIX K: MEAN RADIAL INCREMENTS FOR CYPRESS TREES FOR THE
5-YEAR PERIODS 1967-1971 AND 1972-1976 530

APPENDIX L: BRANCH BIOMASS ESTIMATES FOR CYPRESS AND
HARDWOOD TREES, AND PHOSPHORUS CONCENTRATION
IN BRANCHES 532

APPENDIX M: COLOR LAND USE MAP OF THE GREEN SWAMP
(PAINTED BY 3. BRASHOF AND L. ARRINGTON) 535









TABLE OF CONTENTS Continued


Page

APPENDIX N: CALCULATIONS FOR THE GREEN SWAMP HYDROLOGIC
MODEL, AND LISTING OF THE CSMP PROGRAM USED
FOR THE MODEL SIMULATION 537

APPENDIX 0: NOTES FOR PHOSPHORUS BUDGETS IN FIG. 61 546

APPENDIX P: NOTES FOR ORGANIC CARBON MODELS IN FIG. 62 552

LITERATURE CITED 555

BIOGRAPHICAL SKETCH 570














LIST OF TABLES


Table Paqe

1 Areas of cypress dome study sites. 24

2 Percentage of water drained by the rivers
originating from the Green Swamp. 31

3 Equations used to convert millivolt outputs from
the infrared analysis IRGA to carbon dioxide
concentrations. 51

4 Description and mathematical expressions for the
flows and storage of the hydrologic model for
the Green Swamp (Fig. 17). 88

5 Schedule of plant metabolism and evapotranspiration
measurements. 102

6 Photosynthesis during light period (NLP), respira-
tion during dark period (RDP) and their ratios
(P/R) of cypress leaves at different levels in
the forest canopy. 142

7 Mean photosynthesis (NLP), respiration (RDP) and
their ratios for canopy cypress leaves measured
by other investigators. 146

8 Photosynthesis (NLp), respiration (RDp) and their
ratios (P/R) for the hardwood leaves component
of the forests. 147

9 Summer measurements of respiration (R24) of cypress
and hardwood trunks. 150

10 Winter measurements of respiration (R24 of cypress
and hardwood trunks 152

11 Respiration (R24) of cypress knees measured during
both winter and summer months. 154

12 Photosynthesis (NLP, and respiration (RDP or Ra24)
rates of soil. water and duckweed surfaces
measured during the summer months. 157









LIST OF TABLES Continued


Table Page

13 Photosynthesis (NLp) and respiration (RDp or R24)
rates for water and duckweed surfaces measured
during the winter months. 160

14 Photosynthesis (NLP), respiration (RDP) and their
ratio (P/R) of understory species. 161

15 Transpiration rates of cypress leaves. 163

16 Transpiration rates of hardwood leaves. 166

17 Evaporation rates for soil water or duckweed
surfaces measured during the summer months. 168

18 Evaporation rates from water or duckweed surfaces
measured during the winter months. 170

19 Transpiration of understory species. 171

20 Mean height, DBH, stem density and basal area
for the tree component of the cypress forests. 191

21 Mean DBH, stem density and basal area and their
standard errors for cypress and hardwood trees
in deep and shallow zones. 196

22 Density of understory shrubs in the cypress
domes. 197

23 Complexity indices for cypress forests and
tropical forests. 198

24 Summary of regression equations used to estimate
leaf biomass. 203

25 Summary of regression equations used to estimate
total aboveground biomass of trees 204

26 Leaf biomass for cypress, hardwood and pine trees. 205

27 Total aboveground biomass for cypress, hardwood
and pine trees. 206

23 Ory weight to leaf area ratios and dry weight to
wet weight ratios for cypress leaves at different
levels of the canopy. 208









LIST OF TABLES Continued


Table Page

29 Dry weight to leaf area ratios and dry to wet
weight ratios for hardwood and shrub leaves. 209

30 Leaf area indices for cypress wetlands

31 Regression equations used to compute surface areas
of bole and branches for cypress and hardwood
trees. 213

32 Surface area indices for bole and branches of
cypress and hardwood trees. 214

33 Density of cypress knees expressed as number/m2
ground surface or number/m2 basal area of cypress
trees. 215

34 Mean chlorophyll-a content and chlorophyll-a/b
ratios for cypress leaves at three levels of the
canopy. 217

35 Mean chlorophyll-a content and chlorophyll-a/b
ratio for the hardwood and shrub species. 281

36 Chlorophyll-a content of leaves from other plant
communities. 220

37 Assimilation numbers for cypress and hardwood
leaves at different levels in the canopy. 222

38 Species diversity indices for the cypress swamps
and comparisons with other forest types. 225

39 Total annual litterfall for forested wetlands. 230

40 Mean age of cypress trees for deep, shallow
and combined deep and shallow zones. 233

41 Comparison of basal area increments between the
deep and shallow zones fcr the period 1972-1976. 237

42 Comparison of the mean annual basal area increments
of cypress for the periods 1967-1971 and 1972-1976. 237

43 Stem wood production. 238

44 Optical density of cypress forests measured during
the winter and summer months of 1976. 240









LIST OF TABLES Continued


Table Pag

45 Sky visibility indices of the cypress forest
canopies as measured by hemispherical photographs. 252

46 Total phosphorus (P) concentration and pH
measurements of surface water. 254

47 Organic matter, bulk density and total phosphorus
concentration in sediments. 256

48 Organic matter and phosphorus content of top 20 cm
of sediments on an area basis. 259

49 Total phosphorus concentration (mg/g dry weight) and
quantity of phosphorus (mg/m2 ground surface) in
litterfall. 261

50 Phosphorus concentration in leaves and wood for
cypress and hardwood species. 263

51 Phosphorus content of aboveground live tree biomass. 265

52 Reproductive potential of cypress trees. 267

53 Size (mass) of fallen cypress seeds. 269

54 Areas of the subsystems of the Green Swamp in
1973. 272

55 Estimated mean annual evapotranspiration for
terrestrial systems. 277

56 Estimated mean annual evapotranspiration for wetlands. 278

57 Effects of draining wetlands on available water. 298

58 Structural indices of several forest types. 312

59 Total aboveground biomass of forested wetlands
and upland forests. 314

50 Summary of balance between production, external
inputs and losses of carbon for cypress
ecosystems. 326

61 Community efficiency ratios for the cypress
ecosystems. 332









LIST OF TABLES Continued


Table Page

62 Community metabolism of cypress ecosystems and
other ecosystems. 333

63 Total chlorophyll-a content (g/r,2 ground surface)
and assimilation numbers (g/g'hr) of cypress
wetlands and other systems. 337

64 Annual wood production of cypress wetlands and other
forest types.

65 Summer transpiration and evaporation rates of
cypress wetlands. 345

66 Transpiration ratios of cypress wetlands and other
vegetation types. 349


Appendix Tables

B-1 Extraction procedure for phosphorus in sediment
samples (0. Graetz, 1977, Soils Department,
University of Florida, personal communication). 362

B-1 Extraction procedure for phosphorus in plant litter
and vegetation (P. Straub, 1977, Center for
Wetlands, University of Florida, personal
communication). 362

C-1 Description of subsystems used for mapping. 364

0-1 Curve numbers for different land use on a given
soil type. 369

D-2 Estimtes of percent land use type on a given soil
type (R. Giovannelli, 1975, University of South
Florida, Tampa, personal communication). 370

F-1 Dimensions of trees in Dwarf Cypress plot. 497

F-2 Dimensions of trees in Austin Cary plot. 500

F-3 Dimensions of trees in Prairie Creek. 503

F-4 Dimensions of trees in Sewage Dome 2 plot. 507

G-1 Mean rates of photosynthesis (Pg)a and 24-hour
respiration (R24)b for cypress leaves at different
levels of the canopy. 509









LIST OF TABLES Continued


Appendix Table Page

G-2 Mean rates of gross photosynthesis (Pg)a and 24-
hour respiration (R24)b for the hardwood leaves. 510

G-3 Mean rates for gross photosynthesis (Pg)a and 24-
hour respiration (R24)b for the understory
components.

H-l Regression equations for estimating branch biomass of
cypress and hardwood trees. 513

H-2 Regression equations for estimating total wood
biomass of cypress and hardwood trees. 514

H-3 Harvest data for dwarf cypress (Flohrschutz, 1978). 515

H-4 Harvest data for pondcypress trees (Mitsch, 1975). 515

H-5 Harvest data for baldcypress trees (Duever, 1976,
Corkscrew Sanctuary, personal communication). 517

H-6 Harvest data for gum trees (Nyssa biflora). 518

H-7 Harvest data for pop ash trees (Fraxinus
caroliniana) (Burns, 1978). 519

H-8 Harvest data for wax myrtle (Myrica cerifera),
(Burns, 1978). 520

H-9 Harvest data for pine trees (Pinus elliotti)
(Duever, 1976, Corkscrew Sanctuary, personal
communication). 521

I-1 Leaf biomass distribution in the forest canopy. 523

J-1 Bole surface area estimates for pondcypress using
the conic surface area equation. 526

J-2 Branch area estimates for pondcypress using the
conic surface area equation. 527

J-3 Bolea and branch surface area estimates for gum
trees. 528

K-i Mean raodii incremernls for cypress zr~es for the
periods 1967-1971 and 1972-1976. 520









LIST OF TABLES CONTINUED


Appendix Table Page

L-1 Branch biomassa estimates for cypress and hard-
wood trees. 532

L-2 Phosphorus concentration in branches. 533

N-1 Rain gauge stations and their corresponding
Thiessen weight. 537

N-2 Conversion factors for changing the English system
of units to the metric system. 538

N-3 Source and calculations of storage and flows
for Fig. 56. 539

N-4 Rate coefficients for hydrologic model for the
Green Swamp. 542

N-5 CSMP program used for simulating the hydrologic
model for the Green Swamp. 543















LIST OF FIGURES


Figure Page

1 Aggregated model of a cypress ecosystem
showing major flows and storage of nutrients,
water and organic matter. 14

2 Map showing location of study sites in Alachua
County. 18

3 Map showing location of Dwarf Cypress study site
in Collier County. 20

4 Mean monthly rainfall for the period 1967-1976
for : (a) Gainesville, Alachua County; (b)
the average of Naples and Everglades weather
stations, Collier County. 22

5 Map of Florida showing location of the Green Swamp. 29

6 Geologic formations in the Green Swamp. 33

7 Major components and instruments used to measure
plant metabolism and water exchange. 37

8 Effect of flow rate of air on net photosynthesis
of cypress leaves. 40

9 Variation of carbon dioxide concentration in ambient
air over a 24-hour period. 43

10 An example of the IRGA output (mv) recorded on a
strip chart recorder (YSI), demonstrating the
switching sequence of the timer box. 46

11 Calibration curves for range 1 for the Beckman
model 864 IRGA. 49

12 Calibration curve used to transform the millivolt
output (my), from the dew point hygrometer, to
absolute humidity. 54









LIST OF FIGURES Continued


Figure Page

13 Definition of gross photosynthesis and respiration
pathways. 58

14 Variation of cypress leaf arrangement and size. 68

15 Pattern of cellular arrangement in tree cores. 74

16 Location of rainfall stations, stream gauges and
temperature stations in the Green Swamp. 83

17 Hydrologic model of the Green Swamp. 87
5/3
18 Relationship between DI (depth of surface water)
and streamflow at the Withlacoochee stream gauge
at Trilby. 92

19 Annual pattern of surface water levels. 97

20 Pattern of surface water levels for Prairie Creek
for the period Ocrober 1967-September 1977. 100

21 Daily course of environmental parameters during
metabolism measurements shown in Fig. 22. 104

22 Diurnal patterns of rates of uptake or release
of carbon and water for four components of
the Dwarf Cypress forest for the period May
27, 1977, midnight to midnight. 106

23 Daily course of environmental paratmeters during
metabolism measurements shown in Fig. 24. 108

24 Diurnal patterns of rates of uptake or release of
carbon and water for four components of Austin
Cary Dome for the period 0600 hrs September
12 to 0600 hrs September 13, 1976. 110

25 Daily course of environmental parameters for
metabolism measurements shown in Fig. 26. 112

26 Diurnal pattens of rates of uptake or release
of carbon and water for four components of
Austin Cary Dome for the period 1140 hrs
September 22 to -133 rrs September 23, 1976. 114

27 Daily course of environmental parameters for the
metabolism measurements shown in Fig. 23. 116









LIST OF FIGURES Continued


Figure Page

28 Diurnal patterns of rates of uptake or release
of carbon and water for four components of Austin
Cary Dome for the period 1300 hrs February
4 to 1300 hrs February 5, 1976. 118

29 Daily course of environmental parameters for the
metabolism measurements shown in Fig. 30. 120

30 Dirunal patterns of rates of uptake or release
of carbon and water for four components of
Prairie Creek forest for the period 1030 hrs
May 31 to 1030 hrs June 1, 1976. 122

31 Daily course of environmental parameters for the
metabolism measurements shown in Fig. 32. 125

32 Diurnal patterns of rates of uptake or release
of carbon and water for four components of
Prairie Creek forest for the period 1630 hrs
June 12 to 1630 hrs June 13, 1976. 127

33 Daily course of environmental parameters for the
metabolism measurements shown in Fig. 32. 129

34 Diurnal patterns of rates of uptake or release
of carbon and water for four components of
Sewage Dome 2 for the period midnight to
midnight February 4, 1976. 131

35 Daily course of environmental parameters for
metabolism measurements shown in Fig. 36. 133

36 Diurnal patterns of rates of uptake or release
of carbon and water for four components of
Sewage Dome during the period 1430 hrs July 4 to
1428 hrs July 5, 1976. 135

37 Daily course of environmental factors for
metabolism measurements shown in Fig. 38. 137

38 Diurnal patterns of uptake or release of carbon
and water for four components of Sewage Dome 2
during the period 2210 hrs July 14 to 2208 hrs
July 15, 1976. 139

39 Effect of saturation deficit on hourly transpira-
tion rates of cypress canopy leaves. 175


xvii









LIST OF FIGURES Continued


Figure Page

40 Relationship between mean hourly saturation deficit
and mean hourly transpiration rates for the
hardwood leaves. 178

41 Effect of air flow rate on net photosynthesis of
cypress leaves. 180

42 Effects of air speed, measured at 2.5 cm above
surface inside chamber, on: (a) transpiration
and (b) photosynthesis of the duckweed surface
at Sewage Dome 2. 183

43 Effect of air speed, measured at 2.5 cm above the
surface inside the chamber, on: (a) evaporation
and (b) carbon release from the open water surface. 185

44 Effect of air speed, measured at 2.5 cm above the
surface inside the chamber on the respiration
rate of soil at Prairie Creek. 187

45 Effect of air flow rate on the respiration of trunk
surfaces. 190

46 Relationship between size class and stem density of
cypress trees. 194

47 Absorption spectrum of chlorophyll for cypress leaves
at a height of 9.2 m from Austin Cary, September
13, 1976. 224

48 Annual pattern of total litterfall. 228

49 Relationship between optical density and total leaf
biomass. 243

50 Relationshio between estimated leaf biomass and leaf
litterfall for cypress and hardwood leaves. 245

51 Representative hemispherical photographs of cypress
wetlands. 248

52 A reduced copy of the land use map of the Green
Swamp in 1973. 271

53. Annual changes in rainfall and streamflow for years
1965-1974 for the Green Swamp. 276


-/ i i i









LIST OF FIGURES CONTINUED


Figure Page

54 Seasonal patterns of inputs and outputs of water
to the Green Swamp for 1965-1974. 281

55 Average annual water budget for the Green Swamp. 283

56 Hydrologic model for the Green Swamp showing values
for storage and flows of average 10-year con-
ditions (1965-1974). 287

57 Simulation of the hydrologic model for the Green
Swamp for the period 1967-1972. 289

58 Forcing functions used in simulations of the hydro-
logic model for the Green Swamp. 292

59 Simulation of the hydrologic model for the Green
Swamp. 294

60 Simulation of hydrologic model for the Green Swamp
with the initial conditions, 20 percent wetlands
drained and 40 percent wetlands drained. 296

61 Summary of total phosphorus budgets for cypress
wetlands. 309

62 Summary models of carbon flow and storage, for
summer months for cypress wetlands. 318

63 Summary diagram showing the relationship between
(a) total phosphorus inflow and gross productivity,
(b) total water inflow and gross productivity. 321

64 Summary models of carbon flows and storage, for
winter months, for cypress wetlands. 324

65 Relationship between saturation deficit and trans-
piration ratio for upper-canopy cypress leaves. 353


Appendix Figures

E-1 Diurnal curves of environmental parameters, and
rates of carbon and water uptake and release
E-121 for the major components of cypress wetlands. 373

F-1 Spatial arrangement of trees in the vicinity of
metabolism measurements at the Dwarf Cypress site. 496









LIST OF FIGURES Continued


Appendix Figures Page

F-2 Spatial arrangement of trees in the vicinity of
the metabolism measurements at Austin Cary Dome. 499

F-3 Spatial arrangement of trees in the vicinity of
the metabolism measurements at Prairie Creek. 502

F-4 Spatial arrangement of trees in the vicinity of
metabolism measurements at Sewage Dome 2. 506














Abstract of Dissertation Presented to the Graduate Council
of the University of Florida in Partial Fulfillment of the Requirements
for the Degree of Doctor of Philosophy



A COMPARISON OF CYPRESS ECOSYSTEMS
IN THE LANDSCAPE OF FLORIDA

by

Sandra L. Brown

August 1978

Chairman: H. T. Odum
Major Department: Environmental Engineering Sciences

The structure, metabolism, transpiration and growth rates of several

kinds of cypress ecosystems were measured and related to the quantities of

inflowing phosphorus and water. Adaptations of cypress trees were con-

sidered for their role in maintaining wetlands and affecting productivity

and water conservation of the regional landscape. A hydrologic model of

the Green Swamp in central Florida was developed and simulated under diff-

erent land use scenarios, from which the water savings capacity of the

wetlands was determined.

Water levels in cypress domes with small watersheds and natural

drainage patterns fluctuated widely, with the domes often drying down in

the summer. A cypress dome with a large watershed rarely dried down, and

water levels fluctuated less than the small watershed domes. Water levels

in cypress ecosystems that were affected by human activity were shallower,

and hydroperiods were reduced.

Mean phosphorus concentrations in surface waters ranged from 0.01-

5.86 ppm; the lower values were measured in Dwarf Cypress and the small

X/fi








watershed domes, and higher values were measured in the sewage-enriched

domes. Mean phosphorus content of the top 20 cm of sediments ranged

from 0.23-113.7 g P/m2. The lowest value was found in Dwarf Cypress,

and the highest values were found in a floodplain forest and a cypress

dome receiving runoff from a pasture. Total phosphorus content of above-

ground biomass ranged from 0.25-4.78 g/m2; the lowest value was found

for Dwarf Cypress.

Cypress domes were found to have high stem densities (2150-3951

stems/ha) and high basal areas (41.4-70.8 m2/ha). Dwarf Cypress also

had a high stem density (3000 stems/ha) but a low basal area (15.7 m-/ha),

whereas the floodplain forest (stem density of 1644 stems/ha, and basal

area of 32.5 m-/ha) was similar to upland forests.

High total aboveground biomass was found for cypress domes and a

floodplain forest (20.6-28.4 kg/m2), and leaf biomass accounted for

approximately 2 percent of the total. Total aboveground biomass for

Dwarf Cypress was low (3.6 kg/m2), and leaf biomass accounted for 4

percent of the total.

Stem wood production was found to correlate with site fertility.

High wood production was found for a sewage-enriched cypress dome (1060

g/m2.year) and a floodplain forest (1086 g/m2-year); intermediate values

of 335-541 g/m2.year were found for natural cypress domes, and a low value

of 44 g/m2.year was found for Dwarf Cypress.

Metabolism and transpiration rates were measured for Dwarf Cypress,

a large watershed cypress dome, a sewage-enriched cypress dome and a

floodplain forest. Gross primary productivity was shown to be related

to phosphorus and water inflows. Values of gross productivity

were 2.9 g C/m2.day for Dwa-f Cypress, 12.6 g C/m2-day for a large









watershed dome, 17.7 g C/m2.day for a sewage-enriched dome, and 26.0

g C/m2-day for a floodplain forest. Community respiration followed the

same pattern. Efficiency of gross productivity to total solar insolation

ranged from 0.57-5.47 percent, which correlated with site fertility.

Transpiration rates per unit area of leaf varied little from site

to site, but high leaf area indices at the more fertile sites produced

greater rates of total transpiration. These rates ranged from 1.3 mm/day

at Dwarf Cypress to 5.6 mm/day at the floodplain forest. Low trans-

piration to net productivity ratios were found (156.4-220.6 g H20/g carbo-

hydrate), that suggest that cypress ecosystems conserve water and increase

the hydroperiod.

Simulations of a hydrologic model for the Green Swamp, with varying

amounts of wetlands drained, showed that removal of 80 percent of the

wetlands reduced the available water to the region by 45 percent. It

was suggested that the wetlands were responsible for increasing the

available water by this amount. Water savings due to wetlands area were

9.6 x 104 acre-ft/year of water, which could potentially increase the

economic activity of the region by $5.5 x 107/year.















INTRODUCTION


An important general issue in ecology is understanding the way

flows of materials and energy in ecosystems develop organization and

processes. Important and relatively little known ecosystems are

forested wetlands. How is their organization related to water and

nutrients? What are the adaptations of dominant species to wetland

conditions? Under what conditions are wetlands productive? How are

waters processed and conserved? What trends develop in succession?

What role do swamps play in landscapes?

The purpose of this dissertation is to compare the structure,

metabolism, transpiration and growth rates of several kinds of cypress

wetlands and, with the help of energy systems concepts and models,

to relate adaptations to external conditions. Characteristics of

structure and function of cypress wetlands are used to consider theories

of ecosystem energetic.

Forested wetlands are an intermediate between terrestrial and

aquatic systems and are interesting examples of ecosystems that are

subject to varying water and nutrient regimes. Much of the Florida

landscape is comprised of cypress wetlands (from 0! to 15 percent of

the state (Odum, !977a)), from the nutrient-poor dwarf cypress swamps

to the fertile floodplain forests where baldcypress is codominant with

other swamp species. It has been suggested that swamps are among the

world's most productive ecosystems (Wharton, 1970; Lieth, 1975),





2


however, little is known about how productivity responds to environmental

factors. Wetlands are nature's water management systems (Wharton

et al., 1976; Odum and Ewel, 1977), filtering and storing water in

periods of excess for use by the region during periods of short supply.

Recognizing this role of wetlands in the landscape is of primary

importance to Florida, which has in the past drained many hectares of

these ecosystems.


Physiological and Morphological
Adaptations of Wetland Species


Plants living in saturated, often anaerobic, sediments are faced

with the problem of obtaining adequate oxygen supply for respiration

of the submersed tissues. It has been shown that oxygen from the

aerial parts of herbaceous bog plants diffuse down to the roots and

into the soil, producing an oxidized medium around the roots (Conway,

1940; Armstrong, 1964). Also, these plants have well-developed

lacunal systems and large intercellular spaces. Armstrong (1964)

found that the rate of oxygen diffusion from the plants was inversely

related to the oxygen potential in the sediments.

Armstrong and Boatman (1967) found that bog plants (Molinia sp.)

grow better where water is flowing than in stagnant water. This was

attributed to greater oxygen diffusion rates to greater depths (16-18

cm) in the flowing water area as compared to the stagnated area where

oxygen diffused only to depths of 6 cm.

Oxygen has also been shown to be transported to the root zone of

woody wetland shrubs such as wi lows and myrtles (Armstrong, 1968)

and wetland trees such as tupelos (Nyssa aquatica and N. biflora)

and green ash (Fraxinus nennsylvanica) (Hook and Brown, 1972).









Armstrong (1968) found that oxygen diffused into the bark directly

above the water surface; oxygen diffusion via the leaves was of minor

importance.

Hook and Brown (1972) found that openings in the cambium of flood-

tolerant trees are sufficient to permit free air exchange between the

internal tissues and the atmosphere; non-flood-tolerant species

(sycamore, sweetgum and yellow poplar) do not have this capability.

It has also been observed that tupelo seedlings subjected to continuous

flooding produce larger diameter lenticels with a greater absence of

closing layers than seedlings subjected to intermittent flooding

(Hook et al., i970a).

The pneumatophores of black mangroves and lenticels on prop

roots of red mangroves were shown to serve as aerating tissues for the

roots in the anaerobic sediments (Scholander et al., 1955). It was

also shown that when the tide covered these tissues, oxygen concen-

tration in the roots dropped but carbon dioxide concentration rose

very little. Plants that were not subjected to tidal action had some

diurnal variation, with the lowest oxygen concentrations in the roots

found during the daytime.

Cypress knees have interested scientists for many years. Mattoon

(1915) observed that knees occur mostly where water covers the surface

for extended periods of time, and that their heights often correspond

to the mean high water level. It was suggested that knees possibly

serve as aerating organs, though no definative proof was offered. It

was also suggested that the mechanical strength of knees serves to

stiffen and strengthen the roots to better anchor the tree.









Kramer et al. (1952) attempted to show that cypress knees do act

as aerating organs. They enclosed several knees in cans that were

made air tight at the water line and measured changes in carbon dioxide

and oxygen content of the air. Half of the knees were detached from

the tree. They found that within 24 hours 20 30 percent of the oxygen

was depleted. At first the detached knees consumed more oxygen than

the unattached, but as the experiment proceeded the oxygen demand fell

to practically zero. However, the changes in oxygen of the attached

knees were suggested to be attributed to respiration of the knee

itself due to the large area of cambial tissue. The authors concluded

that there was no evidence that cypress knees were aerating organs.

Carbon dioxide exchange of cypress knees was measured over 24-hour

periods using infrared gas analysis techniques (Cowles, 1975).

There were no trends in the diurnal measurements, but high rates of

carbon dioxide release were found. The carbon dioxide released from a

given area of knee was shown to be considerably greater than from the

same area of trunk surface. It was concluded that the knees possibly

did serve as gas exchange centers for the roots.

Hook et al. (1970b) grew tupelo seedlings under six different

flooding regimes: intermittent flooding with both stagnant and moving

water, continuous flooding with both stagnant and moving water, and

continuous surface saturation with both stagnant and moving water. The

tops were exposed to the natural environment. They found that survival

was almost 100 percent in all cases, but the seedlings growing under

the moving water conditions grew taller. Peak growth occurred several

weeks after the seedlings leafed out, then declined in all cases.

However, unlike seedlings in the moving water treatments, the stagnant









water seedlings never peaked again. This was explained by changes in

the root system. In all cases, the initial root systems deteriorated.

In the stagnant water conditions, the seedlings generally did not

develop new roots, but in the moving water conditions new "water"

roots developed which were capable of oxidizing the rhizosphere.

Although wetland plants have been shown to have adaptations to

transport oxygen to the root zone to facilitate aerobic respiration,

these adaptations do not always provide enough oxygen under extreme

flood conditions. In these cases anaerobic respiration results,

usually producing ethanol and lactic acid. Crawford (1967) and Hook

et al. (1972) found that flooding of non-tolerant species caused ethanol

to accumulate to toxic levels, whereas in flood-tolerant species

ethanol production did not reach toxic levels. It was suggested,

therefore, that species in which flooding increased ethanol to toxic

levels do not survive in wet areas. However, this did not explain how

flood-tolerant species avoid ethanol accumulation even under anaerobic

conditions.

Crawford and Tyler (1969) showed that woody and herbaceous species

that are tolerant to constant flooding accumulate malic acid, unlike

non-flood-tolerant species which accumulate succinic acid. Malic acid

can accumulate without harm to the plant. When aerobic conditions in

the root zone return, the malic acid is subsequently metabolized.

The ability of tree species to tolerate flooded conditions was

summarized by Hook and Brown (1973). They suggested that tolerance

of tree species to flooding is mainly dependent upon a combination of

root adaptations. These root adaptations include the ability of trees

to develop new secondary roots when flooded, and for these roots to









tolerate high concentrations of carbon dioxide, oxidize their rhizo-

sphere, and accelerate anaerobic respiration.


Previous Studies of Forested Wetlands


Cypress domes of Florida have intrigued many scientists. Kurz

(1933) studied the growth rings of trees in cypress domes and found

that the largest trees in the middle were the oldest and those

nearer the edge were younger and smaller. He found that tree mortality

in the deeper water was less than at the edge, which resulted in a

greater proportion of larger trees in the middle.

Vernon (1947) attributed the shape of cypress domes to a gradual

deepening of the basin due to rises in sea level. This deepening of

the dome would result in no germination in the deep water but progres-

sive success of germination towards the edge in the shallower waters.

Kurz and Wagner (1953), however, felt that the shape of the dome

was due to more favorable conditions for tree growth in the center pro-

ducing larger trees. The trees at the edge of the dome were stunted

due to more severe drought conditions and injury by fire.

Monk and Brown (1965) characterized the floristics of 15 cypress

domes in Florida and found that pondcypress is the dominant canopy

species with pine sometimes codominant or very sparse. Black gum is

the dominant understory species. Seedlings and saplings of cypress and

gum are most common. Concentrations of minerals, organic matter and

clays in the sediments generally increase from edge to center of the

dome, whereas pH follows the reverse trend. They found that the major

tree species were distributed along these gradients. For example,

increased flooding and potassium and decreased calcium and pH increase

the importance of cypress.









Mixed hardwood swamps have received less attention. Monk (1966)

studied the effects of pH, flooding and mineral content of soil on

the composition of evergreen and deciduous mixed hardwood swamps. He

found that high pH, calcium content and depth of flooding produce

mixed deciduous forests, whereas low pH and soil minerals, and shallow

water levels produced evergreen forests (bayheads).

More recently, organic matter production and nutrient cycling in

forested wetlands have been the focus of attention. Net organic

matter production of northern forested wetlands was described by

Reiners (1972) for a cedar (Thuja occidentalis) swamp and fen forest

in Minnesota,and by Reader and Stewart (1972) for a black spruce bog

(Picea mairiana) in Canada. Total net production of these forests

ranged from 651 g/m2-year for the fen forest to 1014 g/m2 for the

cedar swamp. Reader and Stewart (1972) found that less than 10 per-

cent of the annual organic matter production accumulated as peat.

Wood accumulation and litterfall measurements were made of

cypress-tupelo floodplain forests in Illinois (Mitsch et al., 1977)

and in Louisiana (Conner, 1975). The forests in Louisiana produced

more litterfall and wood production than those in Illinois. Duckweed

production, however, was greater than litterfall and wood production

in the Illinois swamp as a result of the thin forest canopy and nutrient

rich waters (Mitsch et al., 1977).

Organic matter production and nutrient dynamics of the Okefenokee

Swamp in Georgia were described by Schlesinger (1976). Low organic
2
production was found (692 g/m2 year) and was attributed to low nutrient

inputs. It was suggested that high shrub production is maintained by

periodic fires and an open canopy. The peat deposits, to depths of









91.5 cm, were three times larger in mass than the aboveground forest.

Nutrient storage in the peat was also greater than in the aboveground

forest.

Nutrient cycling in floodplain forests has been studied by

Brinson (1977) and Mitsch et al. (1977), in natural and sewage-enriched

cypress domes by Deghi (1977), and in a sewage sewage-enriched cypress

strand by Nessel (1978). In all these studies, phosphorus was the

element of major concern. All of these ecosystems were found to

accumulate phosphorus mainly in the sediments.

Few metabolism measurements have been made in forested wetlands.

Cowles (1975) measured the seasonal photosynthesis and respiration

rates of various forest components in a sewage-enriched, severely

burnt cypress dome. He found that the average net photosynthesis for

the growing season was 2.4 g C/m2 ground surface-day, and night

respiration was 1.4 g C/m2 ground surface-day. Burnt cypress trunks

had respiration rates approximately five times greater than unburnt

trunks. Even when the duckweed on the surface of the water was

included, P/R ratio For this forest was less than one.

Burns (1978) measured photosynthesis and respiration rates in a

cypress strand in south Florida subjected to varying degrees of

drainage. He also characterized the biomass and structure of these

forests. He demonstrated that lowered water tables reduce forest

productivity and biomass in both roots and aboveground vegetation.

However, the amount of carbon fixed over the year was greater than in

more temperate forests.

An extensive review of the literature on forested wetlands in the

southeastern United States was compiled by Pool et al. (1972). Data









were assembled from over 200 sources and covered a wide range of

subjects, for example descriptive studies of swamps, effects of

fertilization on forest yields and adaptations of wetland species.

They suggested that forest productivity and diversity were directly

related to nutrient and water turnover and inversely related to

length of time flooded.

Wharton et al. (1976) mapped, described and classified the forested

wetlands of Florida. The classification scheme was based generally

on the degree of water flow, and 20 different types of forested wet-

lands were identified. Suggestions for the management and use of

swamps such as water conservation, flood control, treating wastes and

recreation were also discussed.

Forested wetlands occur throughout the tropics on both nonpeaty

and peaty soils (Richards, 1952). The former develop where water

supply is eutrophic and the latter under nutrient deficient conditions.

Although the peaty swamps are less extensive than the nonpeaty, the

former have been studied more. Peat swamps occur in Malaya, tropical

America and tropical Africa. These peat swamps are comparable to more

temperate peat bogs (Richards, 1952). They are very oligotrophic,

have low pH, and are drained by black water streams. Their water

supply is mainly from rainfall. Peat is thicker in the centers of

the swamps.

The more nutrient rich swamps are characterized by high stem

densities but have more open canopies and are dominated by one species

and thus have low diversity (Richards, 1952).

The ecology of peat swamp forests in the Far East has been

reviewed by Whitmore (1975). Hi found the ground surface of these









swamps is higher in the middle than at the edge, giving them a dome

shaped appearance. The only input of water is from rainfall. These

peat forests are comprised of concentric rings of varying vegetation

types, with the innermost vegetation being stunted and xeromorphic in

character. Many species in these forests have prominent pneumatophores.

A decrease in mineral nutrients, particularly phosphorus and

potassium, towards the center of these swamps was found (Whitmore,

1975). Tree density, biomass, height, and diversity decrease from

edge to center in these swamps possibly as a response to decreasing

nutrients (Whitmore, 1975).

A comparison of structure and mineral cycling of tropical forest

ecosystems, including a riverine swamp, was made by Golley et al.

(1975). They found that the swamp forest has a very high total biomass,

but the leaf biomass represented less than 1 percent of the total,

compared to about 5 percent for the other forests. Cycling of phos-

phorus was fast, and the largest amount was stored in biomass.

The value of wetlands to a region was recognized early by Viosca

(1928) for the wetlands of Louisiana. He assigned a monetary value of

$20.5 million to these Louisiana wetlands, based on harvest of wildlife

and fishing. Gates (1942), in describing the bogs of Michigan, stated

that the economic value of bogs was reduced when they were drained.

Undrained bogs act as reservoirs maintaining water levels in the sur-

rounding uplands and improving fish and wildlife production.

A southern river swamp was assigned a total value of $7.2 million

(for 620 acres) because of its wide range of uses (Wharton, 1970).

The largest economic value was assigned to education and public use

(69 percent) followed by improvement of water quality (15 percent)

and other miscellaneous uses such as groundwater storage and lumber.








The feasibility of using cypress domes for recycling secondarily

treated sewage effluent has been extensively studied by the Center

for Wetlands, University of Florida (Odum and Ewel, 1977). By dis-

posing of 10.6 million liters of effluent/day into 289 ha of cypress

domes the increase in energy flow in the natural system had the

capability of increasing the money flow in the local economy by

$58,000/year (Odum et al., 1975). The potential increase in economic

activity is brought about by activities that result from increased

production of cypress wood (harvesting, wood finishing and manufactur-

ing) and increased water recharge.

Using simulation models and water budget calculations, Littlejohn

(1977) found that reduction of wetlands in Collier County (southwest

Florida) reduced aquifer storage and stability of water regimes. He

suggested that if full development of this region included drainage

of swamps, water subsidies, from outside the region would be necessary.

He concluded that conservation of swamps should be an alternative

land use approach to water management and that use should be made of

nature's work rather than fossil-fuel driven technology.

The value of cypress wetlands in Collier County, Florida was deter-

mined by summing the energy inputs to the system (Burr, 1977). A

potential energy value of 25727 coal equivalents/mn year was assigned

to cypress wetlands in undrained conditions. A 68 percent reduction

in potential energy value was found for drained conditions. The

potential energy of water recharged to the aquifers, for undrained
wetlands, was 1493 coal equivalent year.
wetlands, was 14493 coal equivalents/m .year.









Plan of Study and Objectives


Figure 1 is a generalized model of a cypress ecosystem showing

major flows and storage of phosphorus, water and organic matter.

The model summarizes knowledge and hypotheses on wetlands structure

and function and was used as a means for planning the research. The

model was conceptualized using energy language (H.T. Odum, 1971;

Odum and Odum, 1976). The symbols used in this model are defined in

Appendix A. In the model, external inputs of water from rainfall and

surface runoff are shown transporting materials into the surface water

compartment. In some cypress ecosystems (floodplain forests, for

example) water flows through the system, exporting materials from both

the standing water and detrital pools. Surface waters are shown per-

colating downward, depositing materials in the sediments and transpor-

ting products of respiration and materials to the underlying sands and

clays. Water is transpired from the biotic components and evaporated

from the surface waters, driven by water vapor pressure gradients

(saturation deficit) between the leaf and water microclimate,and ambient

air masses. EvaDoration from the water surface is shown to be

influenced by the degree of shading produced by the canopy and tree stems.

Phosphorus is cycled through t;ie biota, taken up by the transoira-

tion stream, and incorporated into plant tissue. A portion of this

phosphorus is returned by litterfall and a portion remains stored in the

woody plant components. Microbial activity is shown to remineralize

phosphorus, making it available for plant uptake.

Photosynthesis is controlled by the amount of light available,

some of which is reflected from the top of the canopy and some of which




















Fig. 1. Aggregated model of a cypress ecosystem showing major flows of
storage of nutrients, water and organic matter.
P = total phosphorus
OM = organic matter
Pg = gross productivity











Wind ----
Tur bu-C0
lence -, -JI
(.Vj C02
Waler
Vapor

WATER
rlaeIun,r UFC
Roan


OP OM1







Frui Is
Reflection P~

H20 Wood


""""h' ~ o S oagrsP P




LEAVES

Roots P CO- Mcrbe
PLANTS SEI
MENTS Si



W a e ic o e









is absorbed by the canopy, reducing penetration to the lower levels of

vegetation. Chlorophyll is shown interacting with sunlight, producing

the chemical potential energy for carbon fixation. This chemical

potential energy interacts with carbon dioxide, phosphorus and water

in proportion to the leaf area to produce organic carbon (gross

productivity). Much of the gross productivity is respired directly.

Net productivity is accumulated in leaves, fruits, stems and roots.

This study measured the main structural features and processes

of many cypress ecosystems, including biomass, stem density, basal

area, and plant diversity to characterize the forest structure, and

chlorophyll, leaf area index and light patterns to characterize the

photosynthetic potential. Photosynthesis and respiration rates of

the major components were measured of four different examples of

cypress wetlands. Transpiration and evaporation from the forests

were also measured. Nutrient contents of the major storage and flows

in the system were determined using phosphorus as the indicator

element, and measurements were made of the hydroperiods to describe

the water regimes. A hydrologic model of the Green Swamp (used for the

regional analysis) was conceptualized, quantified and simulated under

different land use scenarios tc ascertain the water savings capacity of

forested wetlands.

Other questions evaluated were:

1) What is the range of gross productivity for cypress ecosystems

and what proportions of this productivity are allocated to

growth and maintenance?

2) How do the nutrient and water regimes influence the productivity

of cypress ecosystems?









3) Which structural and functional characteristics are similar

among cypress ecosystems and which environmental conditions

govern the similarities?

4) What range of evapotranspiration rates is typical for cypress

ecosystems and what factors influence these rates?

5) What effect does increased enrichment (through the application

of sewage effluent) have on the productivity, structure and

transpiration of a cypress dome?

6) What role do cypress ecosystems play in the landscape?


Description of Study Sites

Cypress Wetlands

The major study sites consisted of eight cypress domes and a

floodplain forest located in Alachua County (Fig. 2) and the dwarf

cypress stand located in Collier County (Fig. 3). The research site

located on property owned by Owens-Illinois, Inc., contained four

cypress domes: Burnt Sewage Dome (S-1), Sewage Dome 2 (S-2), Ground-

water Dome, and Owens-Illinois Dome. The first three domes listed

above were intensively studied as part of a research project at the

University of Florida's Center for Wetlands, to determine the

feasibility of using cypress domes for recycling secondarily treated

sewage effluent (Odum and Ewel, 1977).

Mean monthly rainfall patterns for the two areas from 1967-1976

are shown in Fig. 4 (data from U.S. Department of Commerce). Annual

rainfall for the two counties were comparable although the patterns

were somewhat different. Both areas received their major rainfall

during the months June to September in the form of convective storms,































Fig. 2. Map showing location of study sites in
Alachua County.

























FLORIDA


ALACHUA COUNTY


__






























Fig. 3. Map showing location of Dwarf Cypress
study site in Collier County.



















FLORIDA


i_ ~






























Fig. 4. Mean monthly rainfall for the period 1967-1976 (data
from the U.S. Department of Commerce) for:
(a) Gainesville, Alachua County;
(b) the average of Naples and Everglades weather
stations, Collier County.








although Collier County received more than Alachua County. Alachua

County, however, received more rainfall during the winter months as

a result of frontal weather systems.

Cypress domes. The areas of each cypress dome are given in

Table 1. The vegetation species found in the domes were similar.

Pondcypress (Taxodium distichum var. nutans) was the major canopy tree

species with black gum (Nyssa biflora) as the dominant subcanopy tree.

Other tree species sometimes present were slash pine (Pinus elliotti),

swamp red bay (Persea palustris) and sweet bay (Magnolia virginiana).

The major species present in the understory were fetterbush (Lyonia

lucida), wax myrtle (Myrica cerifera), gallberry (Ilex glabra),

Virginia willow (Itea virginica) and blueberry (Vaccinium ashei and

Vaccinium fuscatum). Ferns such as Virginian chainfern (Woodwardia

virginica) and grasses such as Panicum sp. were common on the forest

floor.

The Burnt Sewage Dome and Groundwater Dome were severely burned in

December, 1973. Most of the understory, hardwoods and pines were

destroyed in the fire. However, most of the cypress survived, although

badly fire scarred. Pumping of sewage effluent to the Burnt Sewage

Dome began in March, 1974, at a varied loading rate. A constant rate

of 2.5 cm/week was established in March, 1975. A similar pumping

schedule of groundwater was applied to the Groundwater Dome. Pumping

of effluent to Sewage Dome 2 began in March, 1975, at the rate of 2.5

cm/week.

Shortly after the effluent was applied to the two sewage domes an

extensive mat of duckweed (Lemna purpusila and Spirodela oligorhiza)

and water fern (Azolla carolinensis) formed. However, since the canopy









Table 1. Areas of cypress dome study sites.


Area
Cypress Dome ha

Morningside Park 1.00

Odum's 1.00

Owens-Illinois 0.93

Hague 0.15

Groundwater 0.69

Burnt Sewage Dome (S-1) 0.51

Sewage Dome 2 1.07

Austin Cary 4.50









at the Burnt Sewage Dome was more open, other species such as cattail

(Typha latifolia), rushes (Rynchospora glomerata) and dogfennel

(Eupatorium compositifolium) were found.

At the Groundwater Dome duckweed and water fern occurred in

patches. Bladderwort (Utricularia sp.) was common in the water column.

A berm was built around the perimeter of the Owens-Illinois Dome

as a result of site preparation approximately 15 years ago when pine

was planted in the surrounding land. This dome had few understory

herbaceous species, and swamp red bays were common.

The Hague Dome is located on land owned by the University of

Florida that has been operated by the Beef Unit division of the Animal

Science Department, Institute of Food and Agricultural Sciences, since

1965. During 1966 the pine trees surrounding this dome were logged

and the land cleared. Some burning occurred around the perimeter of

the dome at this time. Pasture grasses were planted in 1967; cattle

were brought in at this time. The source of nutrients to this dome

are runoff from the pastures, feed-pens, and fertilized and limed

crop fields. In addition to the species listed previously, buttonbush

(Cephalanthus occidentalis), Florida elder (Sambucus simosonii),

softrush (Juncus effusus) and poison-ivy (Rhus radicans) were also

common.

Morningside Park Dome is located in the Morningside Park Nature

Center operated by the city of Gainesville since 1964. A boardwalk

was constructed in this dome in 1971, with minimum disturbance, to

allow visitor access. The understory was aparse giving it an open

appearance. Odum's Dome (on private property owned by H.T. Odum)

was similar in appearance to Morningside Park Dome. However, in the









central pool at Odum's Dome an extensive rush mat (Juncus renens) was

found growing submersed in the water.

Austin Cary Dome is the largest and least disturbed of all the

domes. It is located in the university owned Austin Cary Memorial

Forest. Bladderwort was common in the water column; lizard's tail

(Saururus cernuus) was a common emergent.

Floodplain forest. The floodplain forest site is located east of

Gainesville bordering Prairie Creek, which drains out of Lake Newnan.

The dominant tree species were baldcypress (Taxodium distichum) and

pop ash (Fraxinus caroliniana) with minor species such as laurel oak

(Quercus laurifolia), sweet gum (Liquidamber styraciflua), red maple

(Acer rubrum) and willow (Salix caroliniana). Directly adjacent to

the stream is a natural levee on which the oaks and sweet gums were

found. The baldcypress and pop ash trees were found mostly behind the

levee, where the soil was saturated for the longest time. The most

common understory species were buttonbush and Florida elder. Vines,

such as poison-ivy and trumpet creeper (Campsis radicans), were also

present.

Dwarf cypress. The Dwarf Cypress site is part of a larger area

known as the Big Cypress, so called not for the size of the trees but

for its extent. Of all the plant communities in the Big Cypress, the

Dwarf Cypress community occupies the greatest area (Craighead, 1971).

The Dwarf Cypress community has been described as "scrubby, stunted

cypress growing in marsh-like, seasonally wet prairies" (Davis, 1943,p.5).

The soils supporting the Dwarf Cypress community consist of sand, marls

and clays (Vines and Maloney, 1976) of varying thicknesses. At the

site used for this study the sands were approximately 0.6 m deep lying








on top of limestone (Fiohrschutz, 1978). Fires are a common phenomenon

in the Big Cypress. Severe fires were recorded in the cypress areas

during 1962, 1965, 1971 and 1973 (Hoffstetter, 1973). However, in

the Dwarf Cypress the trees were rarely killed by the fires due to

insufficient flammable material for a hot fire (Craighead, 1971).

The dominant tree species was pondcypress (Taxodium distichum

var. nutans) which formed a very open canopy, often only 5 6 n

in height. Bromeliads such as the wild pineapple (Tillandsia fascicu-

lata) were abundant, growing on the trunks of the cypress. The under-

story consisted of wax myrtle, dahoon holly (Ilex cassine) and deer-

hider (Stylinqia sylvatica). The ground cover was very sparse, with

maidencane (Panicum hemitomen) dominating. This particular area of

dwarf cypress was invaded by pine (Pinus elliottii), perhaps a result

of lowered water levels due to the presence of drainage canals in

adjacent land (Golden Gate Estates).


Green Swamp Region

The Green Swamp is an area of approximately 22300 ha located in

central Florida between latitudes 28005' and 28035' and longitudes

81010' and 82040' (Fig. 5). It has a subtropical climate. The mean

yearly temperature is 22C with mean summer and winter temperatures

of 27C and 170C respectively. Average annual rainfall is approxi-

mately 130 cm, about 60 percent falling from June through September

as a result of convective storms.

Approximately two-thirds of the area was still in its natural

state in 1973 with half of this consisting of both forested wetlands

and marshes. The other third of the land was managed mainly for

agricultural uses.






























Fig. 5. Map of Florida showing location of the Green
Swamp (Pride et al., 1966).







29


















880 86 84e 60 BO






30 30

o/ \ o



92 O, a o

.4 E 28
'C0o H2ILLSBWCTJH U











0 50 I00 150 200 *" "
km

s8 6s' 84" 82" 8o0








Many of the wetlands in the Green Swamp are found in shallow

basins among the upland forests. The large area of wetlands coupled

with the gradual slope of the land (1 m in 4267 m in a northwest

direction) retain the water within the Green Swamp for eventual

percolation to the underlying aquifers. Of the three major poten-

tiometric highs in Florida, the Green Swamp high of 36.6 m above

mean sea level is the highest. It provides a major source of water

to central Florida.

The wetlands in the Green Swamp also serve as the headwaters for

five rivers as shown in Table 2. However, the Little Withlacoochee

and Withlacoochee Rivers drain the largest portion of the Green Swamp,

flowing out in a north-west direction.

The underlying strata of the Green Swamp are comprised of three

geologic units as shown in Fig. 6 (Pride et al., 1966). The upper

layer consists of sands and sandy clays (undifferentiated plastic

deposits) and forms the non-artesian or surface aquifer. It ranges

from approximately 30 m thick in the eastern portion of the swamp to

absent or very thin in the western portion. Underlying the surface

aquifer is a clay layer which acts as an aquiclude between the surface

and Floridan aquifers. This clay layer also varies in thickness,

being very thin to absent in the western region. Beneath the aquiclude

is the Floridan aquifer which consists of the Suwannee limestone, Ocala

limestone and Avon Park limestone. The average thickness of this

aquifer is 300 m.





31


Table 2. Percentage of water drained by the rivers originating
from the Green Swamp.a


River Percent Drained

Withlacoochee 67

Little Withlacoochee 16

Oklawaha 8

Hillsborough 5

Peace 4

aCalculated from data from U.S. Geologic Survey (USGS).






























Fig. 6. Geologic formations in the Green Swamp (Pride et al.,
1966).















METHODS


Methods include field measurements, regional analysis and

modeling.


Field Measurements

Hydroperiod

The fluctuation in water levels in the lowest point of the

cypress swamps was used to determine the hydroperiod. The water

levels were measured either by monthly (in many cases more often)

readings of a staff gauge or by continuous level recordings (Stevens

level recorder). The Prairie Creek site did not flood in the growing

season during the period of study. A survey of this site was made

to determine its elevation abcve mean sea level (MSL). Since

November 1976, the streamflow was partially controlled by a dam

(67.3 ft MSL), which was lowered in March 1976 to the present level

of 66.8 ft MSL. Using lake stage records (A. Bonnet, 1977, USGS,

personal communication), the hydroperiod over the last 10 years was

determined for Prairie Creek by assuming the swamp was flooded when

the lake stage was higher than the elevation of the dam (the eleva-

tion of the dam was 0.33-0.67 ft higher than the lowest point of the

steram bank). When the lake stage was higher than the dam, the depth

of water on the floodplain was calculated as the difference between

the lake stage and the lowest elevation of the swamp.









Plant and Community Metabolism and Evapotranspiration

Plant and community metabolism were measured by observing changes

in carbon dioxide with an infrared gas analyser (IRGA), as air flowed

through chambers enclosing various components of the system.

Evapotranspiration was measured by monitoring water vapor changes at

the same time. These gas changes, measured over 24-hour periods, were

translated into rates of carbon or water released or assimilated by

the various components of the system. Living components were maintained

in as close a natural state as possible. Environmental parameters

such as sunlight, temperature, and air flow which affect plant metabolism

were monitored closely and maintained similarly to those outside of

the chambers.

Figure 7 illustrates the setup of chambers, ducting, tubing and

the necessary instruments. The method involved enclosing part of the

community in a chamber through which ambient air was blown and the

chamber was run as an open system. Several chamber designs were used

depending upon the component to be measured. All the chambers were

constructed from 4 mil polyethylene ("Visqueen"). Spectral analysis

of this material shows that it attenuates radiation in the visible

range (400-700 nm) by about 10 percent (Cowles, 1975). However, in

the infrared range (> 700 nm) the material is highly transpatent

(Trickett and Goulden, 1958; Cowles, 1975). The leaf chambers were

cylindrical in shape, with intake and exhaust vents situated at op-

posite ends, and held semirigid by the flow of air through them.

They all had similar dimensions; the diameter and length were approxi-

mately 0.3 m and 0.6 m, respectively, giving a volume of about 5.2 x
-2. The trunk and knee chambers consisted of plastic sheaths
10 m The trunk and knee chambers consisted of plastic sheaths































Fig. 7. Major components and instruments used to
measure plant metabolism and water exchange.















ENVIRONMENTAL TO OTHER T
CHAMBER CHAMBERS

^\


- MIXING
BAG


DUCTING


TUBING


FLOWMETER


CENTRIFUGAL
BLOWER









enclosing some portion of the plant: about 1 m2 for the trunk and the

entire knee. Rectangular chambers of approximately 0.1 m2 were used

for the soil and water components. Whenever feasible, several 24-

hour records were made for each component with replications on the

same day and on different days.

Rapid air turnover maintained conditions inside the chambers like

those of the outside. The rate of carbon dioxide uptake by plants

enclosed in a chamber is related to the rate at which the air is

supplied. Several investigators (Decker, 1974; Wadsworth, 1959; Avery,

1966; Lugo, 1970; Odum et al., 1970b) found this rate of uptake to

vary hyperbolically with the air flow. At low air flows, the boundary

layer resistance is high, carbon dioxide becomes limiting, and uptake

is low (rising limb of hyperbola). At higher flow rates, the boundary

layer resistance is minimized and carbon dioxide uptake is regulated

by other limiting factors (the asymptote of the hyperbola). To insure

that the measured rates of carbon dioxide were not limited by insuf-

ficient air flew, the range of limiting flow rates was determined for

the leaf chambers. Figure 8 is an example of such a determination done

in situ. Air flow rates were measured with a hot-wire anemometer (Weath-

ermeasure) placed at a point one-third of the diameter from the edge

of the intake duct and multiplied by the cross-sectional area of the

duct to give the total quantity of air delivered in unit time. The

limiting flow rates were about 0.34 m3/min (equivalent to 6 turnovers/

min) or less. Whereas a high flow rate minimizes heat build up in

the chambers, it also decreases the difference in carbon dioxide con-

tent of the ambient and exhaust air streams, making it hard to separate

measurement from instrument "noise." It was found for this particular






























Fig. 8. Effect of flow rate of air on net photosynthesis of
cypress leaves. Measurements made during 1200-1230 hrs
June 8, 1976 at Prairie Creek.






40

















TURNOVERS / min.
5 10
I t


0 0.25 0.5
FLOW RATE, m3/min.


S

8
0


0 RANGE OF
MEASUREMENTS


0.0









IRGA and environmental condition that a flow rate of 0.45-0.55 m /min

(8-10 turnovers/min) was suitable. With this flow range, only chambers

in direct sunlight experienced any heating, and this was limited to

a maximum of 3C difference between ambient and exhaust flows during

the hottest part of the day. Respiration measurements for all species

of trunks were made with flow rates ranging from 0.19-0.29 m3/min.

Flows in this range were comparable to those measured outside the

chamber.

For the duckweed, soil and water surfaces, the air flow rates

inside the chamber were adjusted to the range of those measured

outside. Air speeds at 2.5 cm from the surface were 9-18 m/min

over the soil at the floodplain forest site and 9-15 m/min over the

surface of the water at the cypress domes.

The carbon dioxide concentration in the ambient air fluctuated

widely during diurnal runs, especially during the night when tempera-

ture inversions produced stagnated air masses. Figure 9 shows such a

diurnal variation of carbon dioxide content of the air, which occurred

frequently during the period of measurement. To partially alleviate

this problem, air was drawn from the more uniform air at the top of

the forest canopy when feasible. The air was then pumped to a mixing

bag that had a retention time of approximately 2.5 minutes and was

distributed to the chambers via 10 cm flexible ducting.

The air sampling system was made from 6 mm inside diameter flexible

plastic tubing (Tygon). Sestak, Catsky and Jarvis (1971) reject

plastic tubing such as Tygon as not suitable since it absorbs gasses

and is permeable to carbon dioxide. However, in open systems an

equilibrium between tube and air flow develops quickly. Characteristics































Fig. 9. Variation of carbon dioxide concentration in
ambient air over a 24-hour period. Measurements
were made during June 11-12, 1976 at Prairie
Creek.









were tested by flowing a standard gas (under a negative pressure)

through a short piece of Tygon tubing directly to the IRGA for 10

minutes and then flowing the standard gas through 15 m of the same

tubing, on the ground, for the same length of time. There was no

significant difference between the two means of the IRGA output

(84.2 my for short tubing and 84.8 my for the long tubing) under these

conditions. Under field conditions, where flexibility of the tubing

is important, the Tygon appears to be suitable.

Air was sampled from the intake and exhaust ports of the chambers

via the tygon tubing. These lines were constantly flushed with the

aid of a large vacuum pump. The system was designed to measure four

community components simultaneously. The chamber being sampled at a

given time was controlled by the timer box. The timer box consisted

of four two-way solenoids, programmable timer wheels and tubing with one-

way flow valves (to prevent contamination of sample streams). To

reduce errors in sampling, precautionary measures suggested by Brown

and Rosenberg (1968) were incorporated. An IRGA Beckman model 864 was

used to measure carbon dioxide concentrations. An IRGA Beckman model

215 was used while the 864 was being repaired. Sample gas was compared

to a fixed reference gas. Each chamber was sampled once an hour for

15 minutes: 8 minutes for the ambient air and 7 minutes for the exhaust

air (Fig. 10). Chart data were used to check the system; data used

in the calculations were taken from a digital printer output. Sample

air leaving the analyzer was passed through the dew point hygrometer

(EG and G International Inc., Model 880) to determine the water vapor

content of the air. There was no loss of water vapor in the analyzer





























Fig. 10. An example of the IRGA output (mv) recorded on
a strip chart recorder (YSI) demonstrating the
switching sequence of the timer box. Chambers
2 and 4 were recorded on a similar instrument.






































VS. REFERENCE GAS



VS. REFERENCE GAS










since the temperature of this instrument was hot enough to prevent

condensation.

Incoming solar radiation from 300-3500 nm was measured with

a temperature-compensated dome solarimeter (Lintronic) placed at the

top of the forest canopy. When it was not possible to place the

solarimeter above the canopy, measurements were made at the highest

point, and data for above-canopy insolation were obtained from stations

nearby (K. Heimburg, 1977, Center for Wetlands, personal communication).

Millivolt outputs from the IRGA, dew point hygrometer, and

solarimeter were recorded on a data acquisition digital recorder

(Esterline Angus D2020). Ambient air temperature was measured by

thermistors and recorded on a dual temperature strip chart recorder

(Rustrak) in degrees celsius. The temperature of the exhaust air for

the potentially "hottest" chamber was also recorded. Measurements

of the air flow to all chambers were made daily with the hot-wire

anemometer.


Instrument Calibration

To convert the millivolt outputs from the various instruments

calibration curves were used. The model 854 IRGA was equipped with

two ranges; range 1 was the least sensitive and range 2, the most

sensitive. For the early runs, range 1 was only used. To calibrate

this range several gases of known concentration (analyzed by supplier

to + 5 ppm of carbon dioxide in dry nitrogen) were passed through the

sample side of the analyzer and compared to a known gas ("zero" gas)

in the reference side and the millivolt outputs noted. This procedure

produced curves shown in Fig. 11. For later runs the more sensitive






























Fig. 11. Calibration curves for range 1 for the Beckman
model 864 IRGA. (a) Curve used for winter, 1976,
run at Sewage Dome 2. (b) Curve used for part
of summer, 1976, run at Prairie Creek.




































E




o
0

0
0


CO2 CONCENTRATION, ppm









range (range 2) of the analyzer was used. The calibration procedure

for this range was the same as that for range 1. However, there

was an added feature to this range. The 864 was factory equipped

with a board that made the output of range 2 linearly related to

the carbon dioxide concentration. Table 3 gives the calibration

equations developed for range 2 for the 864 IRGA. For the IRGA 215B,

range 3 was the most sensitive range. This analyzer was designed to

compare two sample streams of gas with each other. By flowing the

"zero" gas through the reference cell at a fast enough rate (about

20 cc/min) to overcome any diffusion from the outside, this analyzer

could be used to measure carbon dioxide exchanges by the same method

as the 864. The calibration procedure for this instrument was the

same as that described for the 864. The calibration equations for

range 3 are shonw in Table 3. As bottles of the "zero" gas were

emptied and replaced by others of different concentrations, it was

necessary to recalibrate the instruments.

Daily calibrations were also performed by flowing the "zero" gas

through both cells of the IRGA, adjusting the "zero" control to zero

millivolts. An upscale gas (which gave approximately i00 percent

full-scale reading) was introduced to the sample cell and compared to

the "zero" gas. Appropriate adjustments of the gain control on the

analyzer were made to insure that the output for this gas was the same

millivolt reading as that obtained during the initial calibration.

The dew point hygrometer was factory calibrated, producing a

curve that related millivolt output to dew point temperature in

degrees celsius. By using the Smithsonian Meterological Tables the

dew point temperature was converted to absolute humidity values








Table 3. Equations used to convert millivolt outputs from the infrared
gas analyser (IRGA) to carbon dioxide concentration. y is
the carbon dioxide concentration in ppm and x is the milli-
volt output.


IRGA
Model Date and Site Equation r

864 June, 1976-Prairie Creek y = 1.40(x) + 235.0 1.00

July, 1976-Sewage Dome 2

864 September, 1976-Austin Cary y = 1.78(x) + 253.0 1.00

215B September, 1976-Austin Cary y = 1.05(x) + 235.0 1.00

215B September, 1976-Austin Cary y = 0.88(x) + 287.7 1.00

864 February, 1977-Austin Cary y = X + 290.0 1.00

215B May, 1977-Dwarf Cypress y = 290.33e(0.0015)x 1.00
y = 290.70e(0.0022)x 1.00









expressed in units of g/m3. The calibration curve obtained is shown
2
in Fig. 12. An exponential model was fitted to the data giving an r

of 1.000.

The dome solarimeter was factory calibrated, and the millivolt

output was linearly related to the solar radiation (10.21 mv/langley

min- ).


Data Reduction and Calculations

To facilitate the task of analyzing the large number of diurnal

measurements, a computer program was formulated to convert the raw

carbon dioxide, water vapor, and temperature readings, all as

functions of time, to rates of assimilation or release of carbon and

water/hour. The millivolt outputs from the analyzer were converted

to carbon dioxide concentrations measured in ppm using the appropriate

calibration equation. The rate of carbon assimilation or release

was calculated from the following relationship (Brown and Rosenberg,

1968):

F x C x L[C021.
g C/hr = -x x[ (I1)
T

where

F = flow rate in m3/hr

C = a conversion factor calculated as follows:

C = 12g C/mole x 103 3/m3 x 273"K
22.4 z/mole x 106 ppm

= 0.14625 g C/m3"K-ppm at 1 atmosphere

T = ambient temperature in K

A[CO2] = change in CO2 concentration measured in ppm.






























Fig. 12. Calibration curve used to transform the millivolt
output (mv), from the dew point hygrometer, to
absolute humdiity. Factory calibration of the
instrument related the my output to dew point
temperature, which was converted to absolute
humidity using Smithsonian Meterological Tables.



























Y (g/m3) = 0.660 e(0093)mv


MILLIVOLT OUTPUT, my


I /









All calculations were made on the assumption that the atmospheric

pressure was constant at 1 atmosphere (1013.6 mb). Pressure in

Gainesville at approximately 150 ft MSL was about 1010 mb.

Water vapor also absorbs infrared radiation. Since the samples

were not dried before entering the analyzer and the instrument was

not equipped with optical filters, the true CO2 concentration in the

air would be somewhat less than that indicated by the IRGA. The

specifications provided by the instrument manufacturer indicated

that the interference due to water for model 864 is 15 ppm C02/2.5

mol % water, and for model 215B is 10.5 ppm C02/3.5 mol % water.

This relationship is linear up to these volume percent (A.W. Peterson,

1976, Beckman Instruments, personal communication).

Carbon released or assimilated was calculated from the difference

between the ambient and exhaust streams. When the community component

was not transpiring or evaporating, the water content of the two air

streams was equal. However, during the day the exhaust air contained

more water vapor. This extra water in the exhaust air caused photo-

synthesis to be underestimated and respiration to be overestimated.

On days when the saturation deficit was high and the plants were

transpiring, this effect produced photosynthetic rates that were 15-20

percent underestimated. As the interference due to water appeared

to be significant, all rates of change of carbon exchange were cor-

rected for this. The correction factor was calculated as follows:
mole H20
Equivalent carbon dioxide (ppm) = mole ai x 100 x I (2)

where

mole H(HE HA) g/m3
le H0(moe/m) 18 g/ole
2 18 g/m~ole









and HE = absolute humidity of exhaust air in g/m3

HA = absolute humidity of ambient air in g/m3


mole air (mole/m3) = 0 Z/m
22.4 t/mole x TK
273
T = ambient air temperature

I = interference factor = 15 ppm
2.5 mol. % H20 for the 864

10.5 ppm
3.5 mol. % H20 for the 215B

The equivalent carbon dioxide content was then converted to

carbon exchange rates according to Eq. 1 and added or subtracted to

the photosynthesis and respiration rates. A sample calculation for

the 864 showed that a difference in water content between the two air-

streams of 1.2 g/m3 at 250C (not an atypical difference) produced an

equivalent carbon dioxide value of 1 ppm.

The rates of carbon exchange, as calculated by Eq. 1, were

plotted to show the diurnal pattern of uptake and release of carbon

dioxide by the community components.

Figure 13a shows the flows of energy and materials believed to

be involved in photosynthesis and respiration. The respiration path-

way R1 represents an acceleration of respiration in response to

increased light, a phenomenon called photorespiration (Zelitch, 1971).

Respiration pathways R2, R3 and R4 occur throughout the total 24-hour

period. However, during the daytime period when sugars are being pro-

duced, these pathways are likely to be greater. An idealized diurnal

curve is shown in Fig. 13b illustrating some possible daytime respira-

tion rates. Patterns of respiration similar to curve (2) in Fig. 13b

























Fig. 13. Definition of gross photosynthesis and respiration
pathways.
(a) Pg = gross photosynthesis
R1 = photorespiration
R2 = dark respiration
R3 = respiration associated with the trans-
location and upgrading of sugars
R4 = maintenance respiration
R = total respiration
(b) Typical diurnal curve of photosynthesis and
respiration.
Curve (1) = daytime respiration,when assumed
to be equal to nighttime respiration.
Curve (2) = possible daytime respiration with
photorespiration included
(RI+R2+R3+Rj4)














(0)
CO2, H0 NUTRIENTS




4UGHT PI UGA
CH
-PHYL FR P OTO 0
-'/ ( RESPIRATIOfi




R






(b)

DAYTIME-

PHOTOSYNTHESIS /


RESPIRATION


COZ AND
H20









were obtained by Sollins (1970) from simulations of blue-green algal

mats and by Lake (1967) from electrical analogues of leaves.

Since photosynthesis and respiration occur simultaneously in

light, measurements of respiration alone are technically difficult.

Several attempts to measure daytime respiration were reviewed by

Sestak et al. (1971). For example, it has been observed that high

rates of carbon dioxide were released immediately following illumina-

tion and that these rates were higher than those measured in the

dark. The magnitude of these bursts has been used as an estimate of

daytime respiration.

During the daytime, gross photosynthesis (P ) is masked by res-

piratory metabolism; therefore, only net photosynthesis (NLP = Pg-R)

was measured. During the nighttime, respiration R2+R3+R4 was measured.

An index of gross productivity (photosynthesis) was estimated as

the sum of net photosynthesis and nighttime respiration (curve (1) in

Fig. 13b).

Using the idealized diurnal curve in Fig. 13b the following areas

are defined:

NP = area 1 = net daytime photosynthesis

RLp = area 2 = respiration measurement during the photoperiod

RDP = area 3 = respiration during dark period
R = area 4 = minimum estimate of daytime respiration

NLp = area (1-2) = (NP RLP) = net productivity during photoperiod

N24 = area 1 area (2+3) = NP (RD + RLp) = net productivity
during 24-houts.

R24 = area (3+4) = (RDP/# hr DP) x 24 = index of 24-hour
respiration

P = area (1+4) = N24 + R24 = index of gross primary productivity.
g









Respiration measured during the day usually occurred during the

early and late hours of daylight. During this time, photosynthesis

was probably occurring but respiration exceeded it. This situation

often occurred during thunderstorms when the light levels fell below

the plant's light compensation level.

Using the equation developed from the data plotted in Fig. 12,

the millivolt output from the dew point hygrometer was transformed

into absolute humidity. The evapotranspiration rate was calculated

as follows:

g H20/hr = FX(HE HA) (3)

where

F = flow rate in m3/hr

H = absolute humidity of exhaust air

HA = absolute humidity of ambient air.

These hourly rates were also plotted to show the daily course of

evapotranspiration.

To express the carbon and water exchange rates on a daily basis,

the areas under the curves were calculated by dividing them into

trapezoids and summing the areas of the trapezoids.

Since metabolic and evaporative processes are closely coupled to

climate, diurnal graphs of solar radiation, air temperature, relative

humidity, and air saturation deficit were plotted corresponding to the

carbon and water exchange diurnals. Temperature was measured directly.

Using the calibration relationship for the solarimeter, the millivolt

output was converted to units of kcal/m 2hr.

Relative humidity and saturation deficit were calculated by

developing a regression relating temperature (OC) to saturation vapor










pressure (e) in millibars (mb) using data from the Smithsonian

Meterological Tables. An exponential model gave the best fit, as

expected, where the main effect is described by the Clausius-Clapeyron

equation.

The following equation was developed:

es(mb) = 6.841 exp(0.0608)TC (r2 = 1.00) (4)
where
es = saturation vapor pressure

Saturation absolute humidity was calculated according to the gas

laws for the partial pressure due to vapor as (Beyers, 1974):

e x MW x 103 erg-cm-3.mb-1106 cm3m-3
S RxT
where
-3
WS = absolute humidity at saturation in g.m-3

MW = molecular weight water = 18 g'mole-

R = gas constant = 8.31 x 107 erg .K-1 mole-1

T = temperature in K.

Relative humidity and saturation deficit were calculated by the

following equations:

R = (PW/PS x 100) (6)

S = es(l-R)

where

R = relative humidity in %

PW = absolute humidity of ambient air in g'm-3

S = saturation deficit in mb









Forest Structure

Diameter, height and species of each woody plant at each study

area were determined. Basal area, tree density, and biomass were

calculated.

The cypress domes were visualized as having two zones: a deep

water zone and a shallow water zone. The dividing line between the

zones was a circle of approximately 30 m radius around the lowest point

of the dome, referred to as the center. For the three treated domes

at the Owens-Illinois site, live-tree maps, prepared by Center for

Wetlands staff, along with information on diameter at breast height

(DBH; measured at 1.37 m above ground surface), height and species

were used. At the Hague study site the small size of the dome enabled

all the trees to be measured. At the other domes, three randomly

located 10 x 10 plots were set out in each of the two zones. The

locations of these plots were determined by randomly choosing the

lower left-hand corner point of the plot, using the center of the

dome as the reference point. This was accomplished as follows:

1. For direction, the domes were further subdivided into eight

450 wedges, measured around the center of the dome, and

numbered 1-8. Using a random number generator a number

between 1-8 was generated.

2. For distance, a random number from 0-20 (this range varied

depending upon the width of the deep and shallow zone) was

generated.

These two numbers used together, therefore, located the corner point

of the plot. At the Austin Cary natural dome, a much larger dome,

four plots were set out in each of the zones. At the Prairie Creek









site, one 30 x 15 m plot was laid out representing about 80 percent

of the total floodplain on the private property, whose owner granted

me permission to work. For the Dwarf Cypress site one 10 x 10 m

plot was laid out, and additional information from four other 10 x 10

plots was obtained from Flohrschutz (1978). In each of the sample

plots all woody species were identified and DBH and height measured

for all individuals with a DBH greater than 3.5 cm. Individual

heights were measured with a clinometer.

The physiognomy of each forest was quantified by using a complexity

index devised by Holdridge et al. (1971). The complexity index

integrates four forest measurements (based on an area of 0.1 ha) as

follows:

C = basal area x tree density x tree species x average height (7)
1000
where all measurements are made on trees with a DBH greater than

10 cm.


Plant Biomass

Tree biomass and its components were estimated using allometric

relationships of wood, leaf and total biomass as functions of DBH

(Whittaker and Woodwell, 1967) (as compared to functions normally

expected for a model of volume related to length, e.g., volume pro-

portional to basal area and height). These functions were developed

by the least squares regression analysis. The regressions were then

applied to each individual tree in the sample lots to give a pre-

dicted biomass component. These components were then summed and

divided by the total area. Understory (shrubs and ferns) biomass

was estimated by harvesting 1 m2 quadrats.









Cypress tree biomass. Three forms of cypress were studied.

Regressions for pondcypress were developed from data from 10 trees

harvested from a cypress dome in Alachua County (Mitsch, 1975). For

the baldcypress trees, regressions were developed from data provided

by Duever (1976, Corkscrew Sanctuary, personal communication) for

seven trees located in the Corkscrew Sanctuary, Collier County,

Florida.

Dwarf cypress trees are often short and have a large diameter

but have very few leaves and little wood biomass. DBH as the only

independent variable would not account for these cases. Therefore,

the independent variable in the dwarf cypress regression was of the

form (basal area x height). Harvest data for this regression were

provided by Flohrschutz (1978) for seven trees harvested from the

Big Cypress area.

Other tree species biomass. Gum tree biomass estimates were

made from regressions developed from the harvest of five trees from

a swamp in Austin Cary Forest. The DBH of each tree was measured

and then cut as close to the ground as possible with a chain saw.

The biomass was separated into leaves, twigs (less than 1 cm diameter),

alive branches, dead branches,and bole. Wet weights were measured for

each category and subsamples were selected and dried at 65CC to con-

stant weight. The volume of the stump was calculated and its biomass

estimated using the density of wood calculated from the dry weight

and volume of samples of the boles.

Wood biomass for pop ash trees was calculated From a regression

developed from harvest data for eight ash trees from south Florida

(Burns, 1978).









To sample the understory biomass, including shrubs less than 2.5

cm DBH and ferns, a stratified sampling procedure was used. A 100

x 5 m transect was laid out across the dome and subdivided into 10 x

5 m plots. The 10 x 5 m plots were further subdivided into 50 x 1 m2

quadrats and assigned a number from 1-50. A random number from 1-50

was generated to locate a 1 m2 quadrat in each subplot for harvest.

The number of understory stems in the transect were also counted.

The biomass was divided into leaves by species, and woody components

and dried to constant weight at 650C.

Leaf biomass distribution. Metabolism measurements were made on

cypress leaves at different levels in the canopy. To extrapolate

these values to the ecosystem level, and estimate of the vertical

distribution of the leaf biomass was made. At Sewage Dome 2 a weighted

fishing line (Odum and Jordan, 1970; Benedict, 1976) was suspended

through the canopy from a tower which extended above the canopy. A

tally was made of the number of leaves that touched the line in a

given 0.3 m. For the understory species (shrubs and gum trees) in

the cypress domes, leaf metabolism was measured at the level where

the biomass appeared to be most dense.

At the Prairie Creek site the weighted fishing line method was

used to measure the distribution of the leaf biomass for the pop

ash trees only. For the cypress leaves at Prairie Creek, such measure-

ments were not feasible and the mean of the metabolic rates measured

at different levels was used. Data for the leaf distribution for the

dwarf cypress system were obtained from Flohrschutz (1978).









Plant Surface Area Relationships

Cypress leaf arrangement and size varies considerably depending

upon its position in the canopy and whether it is a pond- or bald-

cypress. Figure 14 illustrates the range of this variation. Both

appear to have compound leaves, whereas in fact each "leaflet" is a

needle growing from the current year's twig. The pondcypress sun

leaves, with needles appressed along the twig, appear to be single

needles. For measurement purposes a current twig plus its needles

was considered a leaf.

To determine leaf area to weight ratios for cypress leaves, fresh

samples from different heights in the canopy and at different study

sites were collected (the heights chosen were those where the size

and shape of leaf noticeably changed). The leaf area was determined

using an automatic area meter (Hayashi Denko Co., Ltd., model AAM-5).

Samples were dried at 60C for a minimum of 24 hours. All areas

are given as the projection of one side of the leaf. The leaf area

ratios for the hardwood species were similarly determined.

To apply the respiration rates measured by the gas exchange methods

to the community level, estimates of the surface area of tree bole and

branches were needed. Surface areas of both bole and branches were

computed as a conic surface (Whittaker and Woodwell, 1967). For pond-

cypress a regression relating surface area of bole to DBH was developed

from harvest data (Mitsch, 1975) and applied to all the trees measured

in the sample plots at each site.

Branch surface area for the pondcypress trees was determined by

estimating length and diameter (to 1 cm) of branches projecting out

from the main stem. The total surface area of these branches for each



















Fig. 14. Variation of cypress leaf arrangement and size.
(a) From Prairie Creek taken at a height of 14 m, June, 1976
(h) From Prairie Creek taken at a height of 10 m, June, 1976
(c) From Sewage Dome 2 taken at a height of 6 m, July, 1976
(d) From Sewage Dome 2 taken at a height of 17 m, July, 1976
(e) From Sewage Dome 2 taken at a height of 1.5 m, July, 1976


























BALDCYPRESS
SUN LEAVES


BALDCYPRESS
SHADE LEAVES


PONDCYPRESS
SUN LEAVES


PONDCYPRESS
SHADE LEAVES









tree was calculated and a regression developed relating this area to

the DBH of the tree.

For the baldcypress and dwarf cypress, the surface area of the

bole was calculated for all trees in the plots from measurements of

the diameter measured directly above the swell of the buttress and of

the height. Surface area estimates for the branches were made by

visually estimating the number of branches in a given size class and

length for each tree in the study plot.

The surface areas for the bole and branches for gum trees were

estimated from regressions relating measurements of harvested trees

to DBH. For the ash trees the surface area of the bole was calculated

directly from the measurements of diameter and height. The branch

distribution was assumed to be similar to that of the gum trees, so

the regression developed for gum branches was applied to the ash trees.

Respiration rates of cypress knees were expressed on a whole

knee basis. An estimate of knee density/unit area was made by

counting the number of knees in each plot and dividing by the total

area.


Chlorophyll Analyses

Analysis of the chlorophyll pigment was determined within 24-hours

of leaf collection to ensure little or no deterioration of the samples.

Known quantities of fresh leaf samples (about 1 g) were ground with

50 ml of 80 percent acetone to extract the chlorophyll. The acetone

solutions were immediately centrifuged or filtered and the optical

density (D) measured at 663 and 645 nm using a spectrophotometer

(Bausch and Lomb Spectronic 88). The concentrations of chlorophyll-a









and -b were calculated using Arnon's (1949) equations:

chl a (mg/1) = 12.70 (D663) 2.69 (D645) (8

chl b (mg/1) = 22.90 (D645) 4.68 (D663) (9)

Absorption spectra were obtained using a spectrophotometer

(Beckman DBG). From these spectra, Margalef ratios (Margalef, 1968)

were calculated from optical densities (D) as follows:

Margalef ratio = D430/D665 (10)


Plant Species Diversity

For purposes of this study, a species richness index (number of

species/1000 individuals) was used. This was measured by counting

between 500-1000 individuals and tallying the number of species

encountered. The individuals were counted as the dome was traversed

by radial paths from center to edge. At Prairie Creek all individuals

at the site were counted. When cumulative number of species is

plotted against the logarithm of the number of individuals, a straight

line usually results in the range 500-5000 species (Odum et al. 1960).

Therefore, when fewer than 1000 individuals were counted, an extrapo-

lation based on the semi-logarithmic graph of the number of species

and log of the number of individuals was made.

Litterfall

Litterfall was measured by placing 0.25 m2 litter boxes about 1

m above ground surface. Collections were made biweekly during the fall

months, when leaf fall was greatest, and monthly throughout the remainder

of the year. Litterfall was collected at Morningside Park dome, Odum's

dome, Owens-Illinois dome and Prairie Creek. In each of the domes five

litter boxes were randomly placed in the deep water zone and five in









the shallow water zone. At Prairie Creek five boxes were randomly

placed in the 30 x 15 m subplot. Litter collections were stored in a

cooler until they were sorted, usually no more than two days. The

litter was sorted into cypress leaves, hardwood leaves, pine needles

and cones, twigs and bark, cypress cones and seeds, and miscellaneous

small debris. Each component was dried to constant weight at 650C and

the dry weight determined.

Between collections, loss of litter from the baskets due to

processes such as decomposition and leaching probably occurred,

especially in the wet and warm summer months. However, the majority

of the litter fell in the dry months of November and December when

collections were made more frequently. Therefore any loss as a result

of these processes would be minimal.

Tree Growth

Cypress trees produce a readily discernable annual ring, the width

of which reflects that year's annual growth. These rings were used

to estimate annual increases in basal area of the trees and, using the

appropriate regression for wood biomass, annual increases in biomass.

A 25.4 cm increment borer with an inside diameter of 0.5 cm was

used to sample the trees; all cores were taken at approximately breast

height. Trees were sampled from both deep and shallow zones. The

extracted tree core was placed in a soda straw and stored for analysis.

A piece of dowling was hammered into the hole left by the borer to

protect the tree from invasion by insects.

Blocks of wood (approximately 7.5 x 20 x 2.5 cm) containing 4

parallel grooves made by a 4.75 mm router were prepared. The tree









cores were mounted in these grooves, with the xylem tracheids in a

vertical position, with the use of a plastic resin glue. The cores

were then sanded until even with the block surface and smoothly enough

so the individual cells could be clearly seen with the aid of a micro-

scope. The sanding sequence was as follows: coarse belt sander (40

grit); fine belt sander (80 grit); medium orbital sander (120 grit);

fine orbital sander (220 grit); hand sand(about 300 grit); and hand

sand (400 grit).

The cores were then analysed using a dissecting stereomicroscope

set at 40x. Measuring from the bark inward, the width of each ring

for the last 20 years was determined using an ocular micrometer. The

ages were also determined.

Cypress tree rings do not always produce an ideal one ring/year;

they may form a false ring or two rings may merge. False rings are

common in cypress and occur after the formation of latewood when more

favorable conditions for growth return (Kramer, 1964). Zahner (1963)

suggested that severe water stress during the growing season followed

by sufficient rainfall for resumption of growth was the cause of false

rings. A criterion was established to define a tree ring, which was

followed throughout the analysis. Figure 15 illustrates typical

examples of true and false rings. The criterion for a true ring was

that the springwood cell size be approximately the same as observed

visually, to the previous year.


Optical Density

An index describing the mass of vegetation in a forest can be

obtained optically (Odum et al., 1970c). The theory behind the






























Fig. 15. Pattern of cellular arrangement in tree cores.
(a) An idealized tree ring showing the gradual
reduction in cell size from the large cells of
the spring wood to the small cells of the late
summer wood.
(b) An example of a typical false ring pattern.
The cells in column 5 are larger than in the
proceeding column, but not as large as typical
spring wood cells shown in columns 1 and 7.






74







LATE SUMMER WOOD
SPRING WOOD/ ( SPRING WOOD








TO BARK



TRUE RING

(a)










7 6 5 43 2 1


FALSE RING
TRUE RING

(b)








operation of such instruments as spectrophotometers and colorimeters

can be applied to forests. As light penetrates a forest it is absorbed,

reflected and scattered by the leaves, branches and trunks. The

quantity of light reaching the forest floor can then be used to measure

the density of the vegetation.

A portable solar radiometer (Matrix Inc., Mark IV Sol-a-meter)

was used to measure light penetration. This instrument was equipped

with a percent transmission scale. The instrument was adjusted to

100 percent transmission in the full sunlight, and readings were then

taken inside the forest. Readings were taken at 0.5 m above ground

level (mean summer water levels) approximately every two paces as the

domes were traversed from edge to edge through the center, or on a

crisscross pattern at the other sites. A total of 60 readings was

made at each site during both the winter and summer.

During the measurement period, the amount of solar radiation

representing 100 percent varied as the altitude of the sun changed.

Certain precautions were made specifically to partially alleviate

this problem: measurements were taken near noon when the sun's

altitude changed the least, measurements were made on clear days, and

measurements were made as quickly as possible. At the end of the

measurement period the "100 percent full sunlight" was measured again

and in no case did it vary by more than 3 percent of the original value.

Since the optical density data were collected on different days and

at different times, the path length of light through the canopy varied.

For comparison, the measurements were standardized to a vertical path

(simulating the sun's position at the zenith) by the following equation:









Vertical = D cos e (11)

where Dvertical is the optical density computed for the vertical

path and e is the solar altitude (measured from the vertical plane).

Optical density was calculated as follows:

D = log T (12)

where D is opitcal density and T is the percent transmission.

The sensing device on the solar radiometer was a silicon cell

that was sensitive to radiation of wavelengths of approximately 360-

1140 nm. As this range of wavelengths overlaps into the infrared

range, any change in the spectral composition of the radiation

(especially in the infrared range) inside the forest could cause

the optical density to be underestimated. However, measurements of

the radiation spectrum inside and outside of Sewage Dome 2 during the

summer were compared, and Mitsch and Heimburg (1976, Center for Wetlands,

personal communication) found very little difference in the spectral

quality between the two sites. Also, Odum et al1970c) found that

forests acted as a neutral density filter for infrared more than for

visible radiation. Thus the silicon cells may be more suitable for

measuring biomass.

Several investigators (Evans and Coombe, 1959; Anderson, 1964;

Madgwick and Brumfield, 1969; Johnson, 1970) have used hemispherical

photographs to obtain an index of canopy closure and thus a measure of

light penetration. This approach measure radiation only in the photo-

graphically sensitive range. Anderson (1964) found that measurements

of the direct and diffuse light penetrating the forest using conven-

tional instruments correlated very well with the values obtained from









hemispherical photographs. Hemispherical photography produces a

distorted pattern of canopy gaps, which do, however, represent the

pattern flight available to objects (such as seedlings) on the forest

floor.

The hemispherical photographs were obtained using a Nikon camera,

with a 1800 "fish-eye" lens, mounted in a horizontal position on a

tripod. The photographswere taken at five representative stations at

each site during the summer. To produce a black and white negative

with shades of light and dark only, a high contrast film (Kodak

HC135 spectral sensitivity = 300-650nm, Kodak Technical Services) was

used. The negatives were enlarged approximately nine times to a

diameter of 13.4 cm on graphic arts high contrast film (Kodak

Kodalith film) and developed according to the accompanying instruc-

tions, producing a positive transparency.

As the levels of light in the forest were low, it was necessary

to set the camera aperture wide open and consequently to reduce the

depth of field. This tended to produce a blurred image along the

periphery of the photograph. Since the camera lens was focused on

the forest canopy, objects closer than this, such as the understory,

tended to be out of focus. To alleviate this problem the light pene-

tration index was defined as the percent of light passing through

a positive transparency in a 900 cone area (Johnson, 1970). The

light passing through the positive transparency was measured on

area meter.


Nutrient Analysis

The phosphorus contents of standing water, sediment, litter and

vegetation were measured. Samples of water were collected monthly (if