SREL Reprint #2905

Effects of dominant species on vegetation change in Carolina bay wetlands following a multi-year drought

John M. Mulhouse1, Diane De Steven2, Robert F. Lide3, and Rebecca R. Sharitz1

1University of Georgia, Savannah River Ecology Laboratory, Drawer E, Aiken, SC 29802
2USDA Forest Service, Southern Research Station, Center for Bottomland Hardwoods Research, P.O. Box 227, Stoneveille, MS 38776
3Northwest Florida Water Management District, 81 Water Management Dr., Havana, FL 32333

Abstract: Wetland vegetation is strongly dependent upon climate-influenced hydrologic conditions, and plant composition responds in generally consistent ways to droughts. However, the extent of species composition change during drought may be influenced by the pre-existing structure of wetland vegetation. We characterized the vegetation of ten herbaceous Carolina bay wetlands on the South Carolina Upper Coastal Plain during a period of average rainfall and again near the end of a four-year drought. We hypothesized that, as a group, bays dominated by less robust plant species (characteristic of open-water pond and depression meadow vegetation types) would show greater compositional change than bays dominated by dense, robust-form clonal graminoids (characteristic of grass and sedge marsh vegetation types). Aquatic species decreased during the drought in all wetlands, regardless of vegetation group. Compared to grass/sedge marshes, pond/meadow wetlands acquired more species, particularly non-wetland species, during the drought. Pond/meadow wetlands also had greater increases in the abundances of species that require unflooded conditions to establish. Prior to the drought, all wetlands were ponded almost continuously, but during the drought the pond/meadow wetlands had shorter and more variable hydroperiods than the grass/sedge marshes. Thus, vegetation change may be partly confounded with hydrologic conditions that provide greater opportunities for species recruitment in pond/meadow bays. The results suggest that Carolina bay vegetation dynamics may differ as a function of dominant vegetation and climate-driven variation in wetland hydrologic condition.

Keywords: Carolina bays, climate variation, depression wetlands, drought, plant colonization, succession, vegetation dynamics

SREL Reprint #2905

Mulhouse, J. M., D. De Steven, R. F. Lide, and R. R. Sharitz. 2005. Effects of dominant species on vegetation change in Carolina bay wetlands following a multi-year drought. Journal of the Torrey Botanical Society 132(3):411-420.

This information was provided by the University of Georgia's Savannah River Ecology Laboratory (srel.uga.edu).