Recovery of a Louisiana Barrier Island Marsh Plant Community Following Extensive Hurricane-Induced Overwash

Abstract

The Isles Dernieres barrier island chain provides the front line of protection for the Lower Terrebonne Estuary, Louisiana. Landfall of Hurricane Andrew on August 26, 1992 resulted in overwash of most of this island chain, thereby accelerating the erosional processes and altering the plant communities of the islands. Four zones were identified by the depth of overwash sands received (from > 50 cm to < 10 cm) to examine the factors affecting the colonization of vegetation following overwash. Within each zone a permanent transect and thirty permanent plots were established and sampled four times over two years for biotic and abiotic variables. A total of 32 plant species was identified, 30 of which were located in the zone with the highest loadings of sand. Over time this zone also had the greatest increases in species richness. The most important survivor and early colonizer of the high zone overwash was Spartina alterniflora. However, over time Spartina patens became dominant. The other zones, receiving moderate to no sand deposits, differed greatly. The few species present in these zones (<7) were indicative of high salt marsh and salt pan habitats and were dominated by Spartina alterniflora throughout the study. Using multivariate analyses, biotic and abiotic variables were correlated. The soil variables representative of topographical elevation and soil salinity influenced plant community zonations on the Isles Dernieres. Soil fertility and herbivory were not dominant factors affecting vegetation establishment. Backbarrier mars h areas that received the greatest san d loadings are now characterized by dune and swale plant species, while areas that received low sand loadings are returning to a marsh community .