Part I Introduction
Chapter 1 Introduction to Wetland Plants
I. Wetlands and Wetland Plants..................................................4
II. What Is a Wetland Plant?.....................................................5
III. Types of Wetland Plants .....................................................7
A. Emergent Plants......................................................7
B. Submerged Plants....................................................12
C. Floating-Leaved Plants................................................13
D. Floating Plants.......................................................14
IV. Wetland Plant Distribution..................................................16
V. The Evolution of Wetland Plants .............................................17
A. Changes in Angiosperm Classification and Phylogeny....................17
B. Evolutionary Processes in Wetland Plants................................20
VI. Threats to Wetland Plant Species ............................................20
A. Hydrologic Alterations................................................21
B. Exotic Species ........................................................21
C. Impacts of Global Change .............................................22
D. Threatened and Endangered Species ...................................23
Summary....................................................................27
Chapter 2 Wetland Plant Communities
I. Wetland Plant Habitats ......................................................29
II. Wetland Definitions and Functions ...........................................29
A. Ecological Definition .................................................30
B. Legal Definitions .....................................................30
1. U.S. Army Corps of Engineers' Definition.........................30
2. U.S. Fish and Wildlife Classification of Wetlands...................31
3. International Definition ........................................31
C. Functions of Wetlands ................................................32
1. Hydrology....................................................32
a. Groundwater Supply ....................................33
b. Flood Control...........................................33
c. Erosion and Shoreline Damage Reduction ..................33
2. Biogeochemistry ...............................................33
3. Habitat .......................................................34
a. Wildlife and Fish Habitat.................................34
b. Plant Habitat...........................................34
III. Broad Types of Wetland Plant Communities...................................34
A. Marshes............................................................36
1. Coastal Marshes ...............................................36
a. Salt Marshes ............................................36
b. Tidal Freshwater Marshes................................39
2. Inland Marshes................................................39
a. Lacustrine Marshes ......................................41
b. Riverine Marshes .......................................42
c. Depressional Marshes....................................42
B. Forested Wetlands ....................................................44
1. Coastal Forested Wetlands: Mangrove Swamps ....................44
2. Inland Forested Wetlands .......................................48
a. Southern Bottomland Hardwood..........................48
b. Northeastern Floodplain .................................49
c. Western Riparian Zones..................................50
d. Cypress Swamps........................................51
C. Peatlands ...........................................................52
Summary....................................................................59
Chapter 3 The Physical Environment of Wetland Plants
I. An Introduction to the Wetland Environment...................................61
II. The Hydrology of Wetlands .................................................61
A. Hydroperiod and the Hydrologic Budget................................62
1. Transpiration and Evaporation ..................................64
2. Measuring Transpiration and Evaporation ........................65
B. The Effects of Hydrology on Wetland Plant Communities..................67
1. Hydrology and Primary Productivity ............................67
2. Hydrologic Controls on Wetland Plant Distribution ................69
3. The Effects of Water Level Fluctuation on Wetland Plant Diversity . . . .70
4. Riparian Wetland Vegetation and Stream Flow.....................72
C. Hydrological and Mineral Interactions and Their Effect on Species
Distribution .....................................................72
III. Growth Conditions in Wetlands .............................................74
A. Anaerobic Sediments .................................................74
1. Reduced Forms of Elements .....................................75
a. Nitrogen ...............................................75
b. Manganese .............................................76
c. Iron .................................................77
d. Sulfur .................................................77
e. Carbon.................................................78
2. Nutrient Availability under Reduced Conditions...................78
3. The Presence of Toxins under Reduced Conditions .................79
B. Substrate Conditions in Saltwater Wetlands ..............................79
C. Substrate Conditions in Nutrient-Poor Peatlands .........................80
D. Growth Conditions for Submerged Plants ...............................81
1. Light Availability ..............................................81
2. Carbon Dioxide Availability.....................................83
Summary....................................................................83
Part II Wetland Plants: Adaptations and Reproduction
Chapter 4 Adaptations to Growth Conditions in Wetlands
I. Introduction ...............................................................87
A. Aerobic Respiration and Anaerobic Metabolism..........................87
B. Upland Plant Responses to Flooding....................................88
II. Adaptations to Hypoxia and Anoxia..........................................88
A. Structural Adaptations ................................................88
1. Aerenchyma ..................................................88
a. Aerenchyma Formation..................................89
b. Aerenchyma Function...................................91
2. Root Adaptations ..............................................91
a. Adventitious Roots ......................................91
b. Shallow Rooting........................................93
c. Pneumatophores ........................................93
d. Prop Roots and Drop Roots...............................95
3. Stem Adaptations..............................................95
a. Rapid Underwater Shoot Extension........................95
b. Hypertrophy...........................................96
c. Stem Buoyancy.........................................96
4. Gas Transport Mechanisms in Wetland Plants......................97
a. Passive Molecular Diffusion..............................97
b. Pressurized Ventilation..................................97
c. Underwater Gas Exchange..............................101
d. Venturi-Induced Convection.............................101
5. Radial Oxygen Loss ...........................................102
6. Avoidance of Anoxia in Time and Space..........................104
7. Development of Carbohydrate Storage Structures .................104
B. Metabolic Processes..................................................104
1. Anaerobic Metabolism and the Pasteur Effect.....................106
2. Hypotheses Concerning Metabolic Responses to Anaerobiosis ......106
a. McManmon and Crawford's Hypotheses..................106
b. Davies' Hypothesis.....................................108
3. Other Metabolic Responses to Anoxia ...........................109
III. Adaptations in Saltwater Wetlands ..........................................110
A. Adaptations to High Salt Concentrations...............................110
1. Water Acquisition.............................................110
2. Salt Avoidance................................................111
a. Exclusion..............................................111
b. Secretion ..............................................111
c. Shedding..............................................113
d. Succulence............................................113
B. Adaptations to High Sulfide Levels....................................113
IV. Adaptations to Limited Nutrients...........................................114
A. Mychorrhizal Associations...........................................114
B. Nitrogen Fixation....................................................116
C. Carnivory..........................................................117
1. Habitat and Range of Carnivorous Plants ........................117
2. Types of Traps................................................118
a. Pitfall Trap............................................118
b. Lobster Pot Trap.......................................119
c. Passive Adhesive Trap..................................120
d. Active Adhesive Trap...................................122
e. Bladder Trap...........................................123
f. Snap-Trap.............................................124
3. Benefits and Costs of Carnivory .................................126
D. Nutrient Translocation...............................................126
E. Evergreen Leaves....................................................127
V. Adaptations to Submergence ................................................127
A. Submerged Plant Adaptations to Limited Light .........................127
B. Submerged Plant Adaptations to Limited Carbon Dioxide................129
1. Use of Bicarbonate ............................................129
2. Aquatic Acid Metabolism ......................................130
3. Lacunal Transport .............................................131
4. Sediment-Derived CO2 ........................................131
C. Adaptations to Fluctuating Water Levels...............................131
VI. Adaptations to Herbivory .................................................134
A. Chemical Defenses..................................................135
B. Structural Defenses..................................................135
VII. Adaptations to Water Shortages ...........................................136
Summary ...................................................................138
Case Studies ................................................................139
4.A. Factors Controlling the Growth Form of Spartina alterniflora.............139
4.B. Carnivory in Sarracenia purpurea (Northern Pitcher Plant) ..............142
Chapter 5 Reproduction of Wetland Angiosperms
I. Introduction ..............................................................147
A. A Brief Review of Floral Structures Involved in Reproduction.............147
B. Challenges to Sexual Reproduction in Wetland Habitats..................148
II. Sexual Reproduction of Wetland Angiosperms................................150
A. Pollination Mechanisms .............................................150
1. Insect Pollination .............................................150
2. Wind Pollination .............................................152
3. Water Pollination .............................................154
a. Planes of Water Pollination ..............................155
b. Hydrophilous Pollen Adaptations ........................162
c. Hydrophilous Stigma Adaptations........................163
d. The Evolution of Hydrophily............................164
4. Self-Pollination ...............................................166
B. Fruits and Seeds ....................................................167
1. Types of Fruits Produced by Wetland Plants......................167
2. Seed and Fruit Dispersal.......................................171
3. Seed Dormancy and Germination...............................173
C. Seedling Adaptations................................................175
1. Seedling Dispersal and Establishment ...........................175
2. Vivipary.....................................................176
III. Asexual Reproduction in Wetland Angiosperms ..............................177
A. Structures and Mechanisms of Cloning.................................178
1. Shoot Fragments..............................................178
2. Modified Buds ...............................................180
a. Turions...............................................180
b. Pseudoviviparous Buds ................................182
c. Gemmiparous Buds....................................183
3. Modified Stems...............................................183
a. Layers................................................183
b. Runners..............................................184
c. Stolons ...............................................184
d. Rhizomes.............................................184
e. Stem Tubers...........................................184
4. Modified Shoot Bases..........................................185
a. Bulbs ................................................185
b. Corms................................................185
5. Modified Roots...............................................185
a. Creeping Roots........................................185
b. Tap Roots.............................................185
c. Root Tubers............................................185
B. Occurrence and Success of Cloning among Wetland Plants................186
Summary...................................................................188
Part III Wetland Plant Communities: Function, Dynamics, Disturbance
Chapter 6 The Primary Productivity of Wetland Plants
I. Introduction ..............................................................191
A. Definition of Terms..................................................191
1. Standing Crop................................................191
2. Biomass .....................................................192
3. Peak Biomass.................................................193
4. Primary Production ...........................................193
5. Respiration ..................................................194
6. Primary Productivity..........................................195
a. Gross Primary Productivity.............................195
b. Net Primary Productivity...............................195
7. Turnover.....................................................195
8. P/B Ratio....................................................196
B. Reasons for Measuring Wetland Primary Productivity....................196
1. To Quantify an Ecosystem Function .............................196
2. To Make Comparisons within a Wetland.........................196
3. To Make Comparisons among Wetlands .........................197
4. To Determine Forcing Functions and Limiting Factors of Primary Productivity....................................................197
II. Methods for the Measurement of Primary Productivity in Wetlands..............197
A. Phytoplankton......................................................199
1. Dissolved Oxygen Concentration ...............................199
a. Diurnal Dissolved Oxygen Method.......................199
b. Light Bottle/Dark Bottle Dissolved Oxygen Method........200
2. Carbon Assimilation: The 14C Method ...........................201
B. Periphyton ......................................................... 202
C. Submerged Macrophytes.............................................204
1. Biomass .....................................................204
2. Oxygen Production ...........................................204
3. Carbon Assimilation ..........................................205
D. Emergent Macrophytes..............................................205
1. Aboveground Biomass of Emergent Plants .......................205
a. The Peak Biomass Method ..............................210
b. The Milner and Hughes Method.........................211
c. The Valiela et al. Method................................212
d. The Smalley Method...................................213
e. The Wiegert and Evans Method..........................213
f. The Lomnicki et al. Method.............................215
g. The Allen Curve Method................................216
h. The Summed Shoot Maximum Method ...................219
2. Belowground Biomass of Emergent Wetland Plants ................219
a. Harvest Method........................................220
b. Decomposition Method .................................220
E. Floating and Floating-Leaved Plants...................................220
F. Trees ...............................................................221
1. Measures of Dimension Analysis................................221
a. Diameter at Breast Height ...............................221
b. Height................................................222
2. Parameters Based on Dimension Analysis ........................222
a. Basal Area.............................................222
b. Basal Area Increment ...................................223
3. Calculations of NPP of Trees....................................223
a. Stem Production .......................................223
b. Leaf Production........................................224
c. Branch Production......................................224
d. Root Production.......................................224
4. Community Primary Productivity of Forested Wetlands ............225
G. Shrubs.............................................................225
H. Moss ..............................................................226
Summary ...................................................................227
Case Studies ................................................................228
6.A. Salt Marsh Productivity: The Effect of Hydrological Alterations in Three
Sites in San Diego County, California..............................228
6.B. Mangrove Productivity: Laguna de Terminos, Mexico...................230
6.C. Peatland Productivity: Forested Bogs of Northern Minnesota............232
Chapter 7 Community Dynamics in Wetlands
I. An Introduction to Community Dynamics ....................................237
II. Ecological Succession......................................................237
A. Holistic and Individualistic Approaches to Ecological Succession..........238
B. The Replacement of Species...........................................239
C. Developing and Mature Ecosystems...................................240
III. Ecological Succession in Wetlands ..........................................241
A. Models of Succession in Wetlands.....................................241
1. Hydrarch Succession ..........................................241
2. Succession in Coastal Wetlands .................................246
3. The Environmental Sieve Model ................................248
B. The Role of Seed Banks in Wetland Succession...........................250
1. The Relationship of the Seed Bank to the Existing Plant Community .250
2. Factors Affecting Recruitment from the Seed Bank .................253
IV. Competition and Community Dynamics .....................................253
A. Intraspecific Competition ............................................254
B. Interspecific Competition .............................................255
1. Competition and Physiological Adaptations......................256
2. Competition and Life History Characteristics .....................257
3. Resource Availability and Competitive Outcome .................261
4. Light in Submerged Communities ...............................262
5. Light in Emergent Communities................................263
6. Competition and Salt Marsh Communities .......................263
C. Allelopathy......................................................... 265
V. The Role of Disturbance in Community Dynamics .............................266
A. Hydrologic Disturbances .............................................266
B. Severe Weather......................................................269
1. Floods .......................................................269
2. Hurricanes ...................................................270
C. Fire ...............................................................270
D. Biotic Disturbance...................................................271
E. Human-Induced Disturbance .........................................272
Summary...................................................................273
Case Studies ................................................................275
7.A. Successional Processes in Deltaic Lobes of the Mississippi River.........275
7.B. Eutrophication of the Florida Everglades: Changing the Balance of
Competition....................................................276
Chapter 8 Invasive Plants in Wetlands
I. Characterization of Invasive Plants ...........................................279
II. The Extent of Exotic Invasions in Wetland Communities ........................282
III. Implications of Invasive Plant Infestations in Wetlands ........................284
A. Changes in Community Structure .....................................284
B. Changes in Ecosystem Functions ......................................286
C. Effects on Human Endeavors .........................................287
IV. The Control of Invasive Plants in Wetlands ...................................288
A. Habitat Alterations..................................................288
1. Shading the Water's Surface....................................288
2. Shading the Sediment Surface ..................................289
3. Dredging Sediments...........................................289
4. Altering Hydrology ...........................................289
B. Mechanical Controls.................................................290
C. Chemical Controls...................................................294
D. Biological Controls..................................................296
1. Insects.......................................................297
2. Fish ........................................................298
3. Pathogens ....................................................298
4. Fungi ........................................................299
5. Other Organisms .............................................299
V. Case Studies of Invasive Plants in Wetland Communities .......................299
A. Myriophyllum spicatum (Eurasian Watermilfoil).........................299
1. Biology ......................................................299
2. Origin and Extent .............................................300
3. Effects in New Range ..........................................301
4. Control ......................................................301
5. The Natural Decline of Some Myriophyllum spicatum Populations . . .302
B. Hydrilla verticillata (Hydrilla).........................................303
1. Biology ......................................................303
2. Origin and Extent .............................................304
3. Effects in New Range ..........................................305
4. Control ......................................................305
C. Eichhornia crassipes (Water Hyacinth) ..................................306
1. Biology ......................................................306
2. Origin and Extent .............................................307
3. Effects in New Range..........................................308
4. Control ......................................................309
D. Lythrum salicaria (Purple Loosestrife) ..................................310
1. Biology ......................................................310
2. Origin and Extent .............................................310
3. Effects in New Range ..........................................312
4. Control ......................................................313
E. Phragmites australis (Common Reed)...................................313
1. Phragmites australis as an Invasive Species in North America........313
a. Biology ...............................................315
b. Origin and Extent ......................................315
c. Effects on the Habitat ...................................316
d. Control ...............................................317
2. Phragmites australis as a Declining Species in Europe...............317
a. Extent of the Problem ..................................317
b. Causes of the Decline ...................................319
c. Solutions to the Phragmites australis Decline................319
Summary...................................................................321
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