Vegetation Composition Along Salinity Gradients at the Salt Plains National Wildlife Refuge, Alfalfa County, Oklahoma

Understanding the abundance and distribution of communities along environmental gradients provides insight into the understanding of the factors influencing community composition. Environmental gradients are useful in addressing questions concerning community composition due to their often sharply defined zonal communities. Few studies exist on vegetation community composition along salinity gradients of inland salt marshes. In this study, I characterized the vegetation community structure along salinity gradients at the Salt Plains National Wildlife Refuge (SPNWR), Alfalfa County, Oklahoma, quantified the salt tolerance of two dominants at SPNWR, Distichlis spicata and Sporobolus airoides, in the greenhouse, and quantified the germination ability of Distichlis spicata and Sporobolus airoides in a laboratory experiment. Species richness and percent cover of both Distichlis spicata and Sporobolus airoides increased with increasing distance from the salt flats. Greenhouse and germination experiments suggested that germination is more sensitive than growth to salinity stress. Overall, my findings suggest that physiological tolerance to high salinity, specifically ability to germinate at high salinity, limits distribution of vegetation along the margin of the salt flats.