Effects
of dominant species on vegetation change in Carolina bay wetlands following
a multi-year drought
John
M. Mulhouse
University of Georgia, Savannah River Ecology Laboratory, Drawer E, Aiken,
SC 29802
Diane De Steven*
USDA Forest Service, Southern Research Station, Center for Bottomland
Hardwoods Research,
P.O. Box 227, Stoneveille, MS 38776
Robert F. Lide
Northwest Florida Water Management District, 81 Water Management Dr.,
Havana, FL 32333
Rebecca R. Sharitz
University of Georgia, Savannah River Ecology Laboratory, Drawer E, Aiken,
SC 29802
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
*Author
for correspondence (Email: ddesteven@fs.fed.us; phone: 662-686-3602; fax;
662-686-3195)
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.
