Biogeochemistry of Wetlands

Transcription

1 Institute of Food and Agricultural Sciences (IFAS) Biogeochemistry of Wetlands Si Science and da Applications Wetland Communities Wetland Biogeochemistry Laboratory Soil and Water Science Department University of Florida Instructor Mark Clark 6/22/2008 WBL 1 1 Wetland Community Types Topic Outline Brief History of Wetlands Functions and Values Ecological and Societal Definitions Environmental Forcing Functions Hydrarch Succession Prominent Wetland Community Types 6/22/2008 WBL 2 1

2 Wetland Community Types Learning Objectives Reflect andbroaden perspectives for the application of this course material. Introduce the concept of environmental forcing functions Introduce the concept of Hydrarch Succession - how forcing functions and community structure can change over time and space. Illustrate influence of environmental forcing functions and relate the role of biogeochemical processes. 6/22/2008 WBL 3 Historic Perspective Shortly afterwards began the muskegs, which mostly stood under water; these we had to cross for miles; think with what misery, every step up to our knees. The whole of this land of the Lapps was mostly muskeg, hinc vocavi styx. Never can the priest so describe hell, because it is no worse. Never have poets been able to picture styx so fowl. Since that is no fouler Carl Linnaeus, 1932 (noted taxonomist) 2

3 Historic Perspective [a] horrible desert, the foul damps ascend without ceasing, corrupt the air and render it unfit for respiration Never was Rum, that cordial of Life, found more necessary than in this Dirty Place. Colonel William Byrd III ( ) Historie of the Dividing Line Betwixt Virginia and North Carolina in The Westover Manuscripts, written , Petersburg, VA; E. and J. C. Ruffin, printers 1841, 143 pages s

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6 1780 s-1980 s EXTENT AND LOCATION OF ARTIFICIALLY DRAINED AGRICULTURAL LAND IN THE UNITED STATES, 1985 (Courtesy of U.S. Department of Agriculture Economic Research Service.) Frayer et al. estimated that 87 percent of the wetland losses from the mid-1950's to the mid-1970's were due to agricultural conversion. 6

7 Flood Control Waterfowl, Wildlife and Fisheries Habitat 7

8 Water Quality Water Supply 8

9 Non-Game Wildlife Habitat Vegetative Habitat 9

10 Age of Enlightenment The miracle of the light pours over the green and brown expanse of sawgrass and of water-shining and slow moving below, the grass and water that is the meaning and central fact of the Everglades of Florida Marjory Stonemena Douglas, The Everglades: River of Grass Functions vs. Values Values are associated with goods and services that wetlands provide. Functions are natural processes that exist regardless of their perceived value to society. Societal values of wetlands can change through time, function of wetlands do not change. Society does not value all wetland functions, however education, research, and public policy promote the linkages and influence the perceptions of value by society. 10

11 Wetland Values Water Quality Water Supply Habitat Food Web Connections Flood Control Recreation Education Archeological So What Exactly is a Wetland? 11

12 WETLAND DEFINITION "LAND OR AREAS (AS TIDAL FLATS OR SWAMPS) CONTAINING MUCH SOIL MOISTURE. Source: Webster's collegiate dictionary 6/22/2008 WBL 23 WETLAND DEFINITION "A WETLAND IS RECOGNIZED AS A SITE WHERE THE WATER-TABLE IS NEAR, AT, OR ABOVE THE SURFACE OF THE GROUND FOR AT LEAST SOME PORTION OF THE YEAR Source: Goodwin and Niering, Inland wetlands of the U. S., National Park Service 6/22/2008 WBL 24 12

13 WETLAND DEFINITION "...WETLANDS AS AREAS THAT ARE INUNDATED OR SATURATED BY SURFACE OR GROUND WATER AT A FREQUENCY AND DURATION SUFFICIENT TO SUPPORT - AND THAT UNDER NORMAL CIRCUMSTANCES DO SUPPORT - A PREVALANCE OF VEGETATION TYPICALLY ADAPTED FOR LIFE IN SATURATED SOIL CONDITIONS Source: President Carter, Executive Order, May 1977, as per U. S. Army Corps of Engineers 6/22/2008 WBL 25 WETLAND DEFINITION "...A WETLAND IS DESCRIBED AS..LAND WHERE WATER IS THE DOMINANT FACTOR DETERMINING THE NATURE OF DEVELOPMENT AND THE TYPES OF PLANT AND ANIMAL COMMUNITIES LIVING IN THE SOIL AND ON ITS SURFACE. "... THE SINGLE FEATURE THAT MOST WETLANDS SHARE IS SOIL THAT, AT LEAST PERIODICALLY,IS IS SATURATED WITH WATER." Source: U. S. Fish and Wildlife. Cowardin et al. 1977: Classification of wetlands and deep wateer habitats of the U. S., p 3. 6/22/2008 WBL 26 13

14 WETLAND DEFINITION A wetland is an ecosystem that depends on constant or recurrent, shallow inundation or saturation at or near the surface of the substrate. The minimum essential characteristics of a wetland are recurrent, sustained inundation or saturation at or near the surface and the presence of physical, chemical, and biological features reflective of recurrent, sustained inundation or saturation Common diagnostic features of wetlands are hydric soils and hydrophytic vegetation. These features will be present except where specific physico-chemical, biotic, or anthropogenic factors have removed them or prevented their development. National Research Council, /22/2008 WBL 27 Is There More Than One Type of Wetland Community and if so Why? 14

15 Ecological and Geographical view of Wetlands Ecologically Wetlands have a mix of functions behaving both as uplands and as aquatic ecosystems that are often spatially and temporally dynamic. Geographically Wetlands form an ecotone (transition or gradient) between upland and aquatic ecosystems. 6/22/2008 WBL 29 15

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21 Wetland Forcing Functions wetland community Site Geomorphology Hydrology (Hydropattern) Site Climate External influence or pre-existing condition Hydrology-Principal Environmental Forcing Function Dictates oxygen availability Influences biogeochemical cycles Organism survival and selection Temperature regulation Transport of matter In part determines what kind of wetland develops. Hydrology is made up of several components each of which is influential on community structure and biogeochemical processes. 21

22 Hydropattern Duration Depth Wetland Community Structure and Biogeochemical Function Frequency Flow Timing or Season 22

23 ? Hydrology explains many community difference, but not all 23

24 Wetland Forcing Functions Hydrology (Hydropattern) Site Geomorphology Chemical and Physical Environment Biota Site Climate External influence or pre-existing condition Internal abiotic Occur in cool boreal zones with excessive moisture Typically occur as Fens (minerotrophic) Bogs (ombrotrophic) Poor fens (transitional) Northern Peatlands 24

25 Northern Peatlands Hydrology 0% 100% 33% Bogs, 67% Pocosins 67% 33% Fens, Riverine, Seeps Fringe 100% 0% 0% 33% 67% Surface Flow 100% Northern Peatlands Chemistry FENS BOGS POOR MODERATE- RICH EXTREME- RICH ph (5.5) (6.5) Alkalinity 0 0 or low moderate high Cations (Ca, Na, K, Mg) Sphagnum cation exchange system lowers ph in bogs, organic acids resulting from decomposition also lowers ph Low ph slows decomposition resulting in raised peatlands Productivity of fens is often greater than bogs, but sediment accretion rates are often lower. Low acidity in bogs reduces microbial activity C:N ratio is also high slowing decomposition 25

26 Tidal Marshlands Tidal Freshwater Marsh Tidal Salt Marsh Riparian Wetlands Nutrient Cycling Community has open nutrient cycles dominated by adjacent stream or river and runoff from upslope forest. High productivity and cycling of biomass Often act as nutrient transformers, assimilating inorganic forms of nutrients and exporting organic forms. 26

27 Salinity Salinity & Freeze Spatial and Temporal Scales of Environmental Forcing Functions Temporal Scale (years) Spatial Scale (meters 2 ) <1-3 < > Fast (1-10) Herbaceous vegetation regrowth to steady state biomass Non severe fires Hydropattern Water quality Intermediate (10-100) Residual impact of alligator activity (holes and nest mounds Woody vegetation regrowth to steady-stat t t biomass Sever fires Hurricanes Freezes Drought/Flood cycle Slow (>100) Soil Accretion to stable depth Microbedrock topography State of Sea level Macrobedrock topography (L. Gunderson, in Davis and Ogden, 1994) 27

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29 Wetland Forcing Functions Hydrology (Hydropattern) Site Geomorphology Chemical and Physical Environment Biota Site Climate External influence or pre-existing condition Internal abiotic Internal biotic Environmental Forcing Functions and Time (P. White, in Davis and Ogden, 1994) 29

30 Vegetative/Biogeochemical Change over Time Hydrarch Succession 30

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33 Can Hydrarch Succession Be Reversed? 33

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35 Putting the Pieces Together Biological adaptations provide potential establishment and persistence of species Establishment - Reproductive strategies Persistence - Morphological (inundation, drought, fire tolerance etc.). Environmental conditions (Forcing Functions) select among species. Greater the range in forcing functions, the greater the type of communities (as long as genetic diversity is available). Hydrarch Succession Change in community structure over time in response to changes in forcing functions. Summary of Learning Objectives Change in societal value of wetlands has been dramatic over the past 200 years. Wetlands, although aggregated legally as one, are ecologically very diverse. Environmental forcing functions ultimately determine the vegetative character of the community and in many respects its ecological function. Sediment accretion, characteristic of almost all wetlands, guarantees the magnitude and influence of certain forcing functions will change over time. Application of hydrologic and biogeochemical concepts are equally diverse and subject to dynamic change based on differences in biotic and abiotic factors over time and space. 35