Biodiversity and ecosystem function of U.S. Coastal Plain wetlands in different stages of succession

Background/Question/Methods

Throughout the southeastern U.S. Coastal Plain, wetlands formed by beaver activity frequently develop in valleys, and can represent dynamic features of stream networks.  Formation of these wetlands alters hydrology, driving changes in ecosystem structure and function across the landscape.  However, little quantitative data exists to describe the effects of wetland formation and subsequent drainage on biodiversity and ecosystem functions.  To examine these patterns for wetlands in the Oakmulgee District of the Talladega National Forest (TNF) in Alabama, we completed a synoptic survey of 12 wetlands, collecting data on plant community composition, biodiversity, and foliar chemistry (C:N) of dominant plant species.  We combined this research with long-term (20 years) data of hydrology, water chemistry, and vegetation from one beaver-formed wetland in the TNF to develop a conceptual model of wetland succession. 

Results/Conclusions

We developed a conceptual model of succession linked to changes in community composition that included (1) an aquatic stage dominated by floating-leaved species; (2) a wet meadow stage dominated by emergent species; (3) a shrub-forest stage; and (4) a riparian forest stage.  Surveys revealed communities comprised of different plant assemblages that corresponded to these four successional stages, including ponds dominated by Nymphaea odorata or Brasenia schreberi; wet meadows dominated by Juncus effusus, Sparganium americanum, or Woodwardia areolata; mixed emergent/shrub communities dominated by J. effusus and Acer rubrum or Alnus serrulata; and forested valleys dominated by Magnolia virginiana, Liquidambar styraciflua, or Quercus nigra.  Shifts in plant communities may contribute to changes in soil carbon (C) and nitrogen (N), as foliar chemistry varied among plants.  Such changes in biodiversity, community composition, and foliar chemistry in these wetlands over time may have landscape-level consequences by altering patterns of nutrient or material export from wetland patches in Coastal Plain stream networks.