Date of Award

1992

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Biological Sciences

First Advisor

James B. Grace

Abstract

The disturbances of herbivory, simulated "eat-outs" (clipping and removal of above-ground biomass), and burning were examined for their effect on total biomass, individual species abundance, and species richness in several different marsh communities. Herbivory significantly reduced the total community biomass of all the marshes studied. Simulated "eat-outs" reduced the total biomass of the freshwater marsh but had no persistent effect on the total biomass of either the oligohaline or mesohaline marshes of the Pearl River. Both the oligohaline and the mesohaline marshes were able to recover from a removal of above-ground biomass (simulated "eat-out") within two years. The freshwater marsh was unable to recover in this period of time. Fire reduced the total biomass of the only community in which it was studied, the oligohaline marshes of Little Lake. The disturbances of herbivory, simulated "eat-outs", and fire affected the abundances of several species. Herbivory reduced the abundance of Panicum virgatum and Aster subulatus in the freshwater marsh, increased the abundance of Panicum virgatum and Vigna luteola in the oligohaline marsh of the Pearl River, and decreased the abundance of Spartina patens and Scirpus olneyi but increased the abundance of two annual sedge species, Cyperus flavescens and Cyperus odorata in the oligohaline marshes of Little Lake. Simulated "eat-outs" reduced the abundance of Spartina cynosuroides and Panicum virgatum in the freshwater marsh, reduced the abundance of Panicum virgatum but increased that of Sagittaria lancifolia in the Pearl River oligohaline marsh, and decreased the abundance of Spartina alterniflora in the mesohaline marsh. The other disturbance studied, fire, reduced the abundance of Spartina patens and Bacopa monnieri but did not cause any species to increase in abundance. None of the communities studied underwent any change in species richness in response to any of the disturbances studied. Clearly, the disturbances of herbivory, simulated "eat-outs", and fire reduced the biomass of the communities studied and altered the relationships of the species within the communities although species richness was unaffected.

Pages

152

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