Vegetational analysis and floristics of four communities in the Big Ball Hill region of Padre Island National Seashore

Vegetation of the Big Ball Hill region of Padre Island National Seashore wa s sampled using 100-m transect lines within each of four communities during four sampling periods in 1996 and 1997. Importance values of plant species and community richness, evenness, and diversity were determined. Seventy g enera and 83 species of flowering plants were identified. These occur in 33 families with the Poaceae (17 species), Asteraceae (11 species), Cyperacea e (8 species), and Fabaceae (6 species) most common. The Big Ball Hill flor a contains Flaveria brownii and Sporobolus tharpii, which are endemics of t he western Gulf barrier islands. Lycium carolinianum var, quadrifidum, repo rted only along bayshores in Texas, was found in the tidal flat community. Plant community structure was quantified and the following profile for the Big Ball Hill region is proposed: 1) a bare foreshore primarily due to huma n disturbance, 2) a backshore, with much bare ground often due to human dis turbance, vegetation dominated by Uniola paniculata, 3) a primary dune ridg e supporting Ipomoea imperati and U. paniculata as dominants on the windwar d side and U. paniculata, Heterotheca subaxillaris, and Paspalum monostachy um dominant on the leeward side, 4) a zone of secondary dunes or vegetated flats, or a mosaic of both with Schizachyrium scaparium var. littorale codo minant with P. monostachyum, and 5) a tidal Rat that is largely bare but wh ich supports typical halophytic vegetation including Blutaparon vermiculare , Limonium carolinianum, Machaeranthera phyllocephala. Monanthochloe littor alis, Salicornia virginica, and Sporobolus virginicus. Compared to results of earlier vegetation studies on the island, these communities are less div erse and appear to be recovering from previous overgrazing.