Variations of dissimilatory nitrate reduction processes along reclamation chronosequences in Chongming Island, China

Conversion of coastal wetland to paddy soil can significantly affect soil biogeochemistry cycling. However, the impacts of coastal wetland reclamation on dissimilatory nitrate reduction processes and nitrogen fate remain poorly understood. In this study, the effects of coastal wetland reclamation on the rates and related functional gene abundances of dissimilatory nitrate reduction processes, N₂O emission, and the fate of reactive nitrogen were investigated in Chongming Island, China. Conversion of coastal wetland to paddy soil can significantly increase dissimilatory nitrate reduction rates. Denitrification was the dominant pathway contributing to the total nitrate reduction, while anammox and DNRA played an important role. Conversion of coastal wetland to paddy soil can significantly affect soil physicochemical characteristics and abundances of related functional genes, leading to the variations of nitrate reduction rates. Although the nitrate removal rates increased along the reclamation chronosequences, due to the intensive N fertilizer application and increased nitrification and ammonification rates, more reactive N can be exported in paddy soil than in wetland, and N₂O emission was stimulated significantly along reclamation chronosequences. This study can provide valuable insights into the mechanisms of reclamation influences on soil N recycling.