A hydrogeologic-landscapes framework for depressional-wetland vegetation in the Southeastern Coastal Plain, USA
Numerous wetland depressions occur across the U.S. Atlantic Coastal Plain, a region of complex physiography spanning a landward-to-seaward elevation gradient. Coastal Plain depressional wetlands are noted for supporting a diversity of plant communities that provide important faunal habitats. Because these "isolated" wetlands are vulnerable to degradation and loss on private lands, protected and managed public lands have become important refugia for their conservation. A practical system of vegetation types and vegetation-dynamics models can aid in developing management or restoration strategies for these conserved wetlands. The concept of hydrogeologic landscapes provides a useful model framework because landform, soils, and topographic position can influence not only depression form and hydropattern, but also ecological drivers of vegetation change such as drought, fire, and land-use. In the Lower Coastal Plain of South Carolina, USA, a hydrogeologic-landscapes approach was used to examine relationships between wetland vegetation and depression attributes such as size, soil type, and hydroperiod. The Lower Coastal Plain data were also combined with a similar Upper Coastal Plain study to provide a synthetic analysis of region-wide patterns. These studies identified a consistent set of wetland vegetation types that differed in landscape-associated depression attributes. Wetland types also differed in occurrence across sub-regions, owing in part to contrasting histories of land-use and wetland disturbance. The findings were used to develop conceptual state-change models that link wetland vegetation to depression hydropatterns and other ecological drivers in different landscape settings.