Measuring the effect of a prescribed burn on nitrification-coupled denitrification in a restored Chesapeake Bay tidal marsh

Abstract

Prescribed burning is a management practice used in tidal marshes of the Mid-Atlantic United States to improve habitat for wildlife. The impact of burning on tidal marsh biogeochemical processes, especially coupled nitrification-denitrification, has not been characterized. This study investigated the effect of burning on nitrification coupled denitrification in a restored tidal marsh on Poplar Island, Maryland, United States. A prescribed burn was completed in March 2024 to remove overwintering habitat for stem-boring insects. Soil-water exchange of gases and nutrients and soil pore water nutrients were measured before and after the prescribed burn. A nitrate addition experiment was conducted to explore the importance of dissimilatory nitrate reduction to ammonium. Soil-water exchange did not respond to burning, though strong interannual variation in denitrification was detected, with high rates measured in July 2023. The nitrate addition experiment revealed an increase in ammonium production, indicating the presence of the DNRA pathway in Poplar’s marshes.