Impact of Prescribed Burns on Marsh Surface Elevation: Big Branch Marsh, Louisiana

This study examines the impact of prescribed burning on marsh elevation by comparing relative surface elevation change between burned and unburned control marsh plots using a Surface Elevation Table (SET) at Big Branch Marsh National Wildlife Refuge in St. Tammany Parish, LA. This project was developed in conjunction with the U.S. Fish and Wildlife Service and serves as the foundation for a long-term program for evaluating the effects of burning on marsh surface elevation. Three years after the initial burn, results indicate there was no significant difference in surface elevation change between the island receiving the burn treatment and the unburned control island. However, immediately following the burn, elevation differences between the two islands were significant, with the burn plot registering a significant decrease in elevation. The results over the course of the study might have been different had the study area not been impacted by hurricanes Faye, Gustav and Ike less than 5 months after the burn, which deposited a large amount of sediment and erased this initial deficit. These results indicate that while prescribed burning should increase vegetation density, thus increasing organic matter accumulation and potential vertical accretion, the possibility exists that the burn event will create an elevation deficit too large for those gains to overcome. This study also demonstrates the importance of storm-derived sedimentation events in the Gulf Coast marshes.