Graduation Year

1987

Document Type

Thesis

Degree

M.S.

Degree Name

Master of Science (M.S.)

Department

Biology

Degree Granting Department

Biology

Major Professor

Bruce C. Cowell

Committee Member

Clinton J. Dawes

Committee Member

Earl D. McCoy

Abstract

Grass-sedge marshes in west-central Florida were studied to determine the abundances and distributions of herbaceous angiosperms. Cluster analysis, reciprocal averaging, and a biotic boundaries technique were used to analyze the relationship between community composition and depth within the marsh. Shallow areas were dominated by Rhynchospora filifolia, Dichanthelium sabulorum, and Rhynchospora cephalantha. Abundances of the species fluctuated seasonally and varied between marshes. Deep areas of individual marshes differed markedly from shallow areas and from each other. A deep, well-drained marsh supported a monospecific stand of Juncus repens, while a less deep, but poorly drained marsh had a community dominated by Pontederia cordata. Similarities within marshes decreased when water levels were high. The importance of a depth gradient increased in December when conditions were wet and standing water was present in the marshes. Biotic boundaries within the marshes corresponded with water levels. Water level and drainage patterns explained up to 74% of the variation in the community in Marsh 3 and 41% of the variation in Marsh 4. In the shallow marshes no floristic gradients were detected.

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