Camille Steenrod

M.S. Candidate, Southern Illinois University

2022 Conference Travel Grant Type 2

Effects of Layered Legacies of Disturbances on Marsh Transgression in the Northern Gulf of Mexico

Sea levels are rising due to climate change. The persistence of marshes will ultimately be determined by the ability of marshes to keep pace with sea level rise. However, frequent disturbances, such as prescribed fire and hurricanes, are acting in combination with sea level rise to impact these vulnerable coastal ecosystems. This study addresses the effects of the layered legacies of disturbances (including 31 hurricanes/tropical storms and four prescribed burns from 2004 to 2021) on community composition in a marsh along the northern Gulf of Mexico over a 70 cm elevation gradient (-10 cm to 50 cm). It was hypothesized that community composition would change over time from 2004 to 2021, and that there would be compositional differences along the elevation gradient in 2021. Both hypotheses were supported: almost all combinations of plots across all elevation zones were significantly different from one another, and all elevation zones were significantly different from one another in 2021. These compositional changes demonstrate that vegetation communities along the Gulf Coast are primarily driven by the tidal regime and storm surges, and that the community is responding to the disturbances impacting this area. Fires are likely to have reduced woody species and discouraged regeneration, while hurricanes are likely to have uprooted trees and stressed vegetation through storm surge inundation and extreme precipitation and flooding. These compositional changes suggest that the species in lower elevations are migrating upslope as sea level rises, however, more studies on how each species’ abundances are changing through time are needed.