Vegetation, Peat Elevation and Peat Depth on Two Tree Islands in Water Conservation Area 3-A

Abstract

<p>Vegetation (species composition and cover abundance) and peat and bedrock elevations were sampled along multiple transects across the head, near tail and far tail of two tree islands (designated the North Island and South Island) in Water Conservation Area 3-A. The heads of both islands are underlain by topographic highs in the bedrock. The peat layer was thinnest on the heads and much thicker on the near tail and far tail. The thinner peat layer on the heads of tree islands suggests that there is a mechanism that limits the maximum elevation of a tree island. Altogether 84 and 51 species were found on North Island and South Island, respectively. The results of an agglomerative hierarchical cluster analysis indicated that there were 9 and 7 plant assemblages on North Island and South Island, respectively. Although sometimes dominated by different species, the 7 assemblages on South Island had ecologically equivalent counterparts on North Island. Three plant assemblages (dry forest, wet forest, forest-fem) dominated by trees and shrubs (Chrysolalanus icaco (coco plum), Myrica cerifera (wax myrtle), Salix caroliniana (Carolina willow), and Schinus terebinthiflolius (Brazilianpepper)) were found primarily on the heads of the islands, which had the highest peat and bedrock elevations, and sometimes on the adjacent near tail. Sawgrass (Cladiumjamaicense) dominated plant assemblages (sparse sawgrass, dense sawgrass, decadent sawgrass, sawgrass-cattail) and wet prairie (Eleocharis cellulosa Torr. and Panicum hemitomon Schult.) were found at lower peat elevations and slough assemblages (Bacopa caroliniana, Eleocharis cellulosa, Nymphaea odorata, Utricularia purpurea) were found at the lowest peat elevations. There generally was no clear-cut relationship between bedrock or peat elevations and the distribution of the various sawgrass and wet prairie assemblages.</p>