Phragmites-fire feedbacks: the influence of fire and disturbance-altered hydrology on the abundance of Phragmites australis

Historical land-use conversion and drainage may increase the risk of high intensity, soil-consuming fires in peatlands. Severe fires may degrade ecosystem resilience through changes in hydrology and by removing remnant seed and bud banks. Lower ecosystem resilience leaves peatlands highly susceptible to species invasions from aggressive colonizing vegetation post-disturbance. In this work we aimed to address the impacts of smoldering fires on the abundance of the noxious Phragmites australis in a large fire scar at the Great Dismal Swamp National Wildlife Refuge (VA and NC, USA). Primarily, we wanted to observe the extent of the relationship between the altered hydrology of post-fire conditions and P. australis occurrence. We did so by leveraging high resolution satellite imagery, random forest models, LiDAR data, and water table observations. Our results suggest that P. australis is aided by a hydrologic regime generated, in part, from the combined effects of drainage and deep smoldering fires. Our findings emphasize the importance of hydrologic management post-disturbance for limiting P. australis invasion. Further, we highlight the potential for feedbacks between deep peat-consuming burns and P. australis invasions and spread in degraded peatlands.