Analysis of longleaf pine sandhill vegetation in northwest Florida

Between June 1994 and May 1995, we measured plant species densities, species richness, tree basal area, and soil chemistry in thirty, 81-ha sandhill plots at Eglin Air Force Base, Florida. Comparisons were made between three sandhill types: (1) fire-suppressed, (2) burned with bluestem (Andropogon spp. and Schizachyrium spp.) dominance, and (3) burned with wiregrass (Aristida beyrichiana) dominance. Species assemblages for each sandhill condition are discussed. Species richness and densities of forbs, clonal shrubs, and graminoids were highest in burned and wiregrass-dominant plots. Fire-suppressed plots harbored lower stem densities of herbaceous and woody groundcover species, but their floristic composition was similar to that of burned plots. The majority of fire-suppressed plots were more floristically similar to the burned and bluestem-dominant sandhills. Soil chemistry did not correlate strongly with observed vegetation patterns, but there is evidence that soil texture influences species assemblages within sandhill communities. Whereas fire frequency appears to have its greatest effect on vegetation structure and relative dominance of certain species or life-forms, plant species richness, and species composition appear to be largely determined by edaphic variation and soil disturbance histories.