Denitrification in soils of hydrologically restored wetlands relative to natural and converted wetlands in the Mid-Atlantic coastal plain of the USA

In the last several decades, there has been considerable effort to protect and restore wetlands throughout the USA. These efforts have required significant investment of both private and public funds. Accordingly, it has become important to document the effectiveness of this protection and restoration. This study for the Mid-Atlantic Region (MIAR) Wetland Conservation Effects Assessment Project (CEAP) was part of the US Department of Agriculture CEAP. This study compared natural, converted, and hydrologically restored wetlands in the states of Delaware, Maryland, and Virginia. There were forty-eight total sites, and each site was sampled at 4 landscape elevations (wettest to driest) during a three year period. Here we report an assessment of soil denitrification conducted as one component of the MIAR Wetland-CEAP using denitrification enzyme activity (DEA). DEA values varied significantly with relative elevation and management DEA response to nitrate addition varied significantly with relative elevation and management. In stepwise regression, total C and moisture were the most influential physiochemical conditions for the converted and natural wetlands, respectively. Total C and Ca were the most important for the restored wetlands. Moreover, the percentage of denitrification as nitrous oxide and nosZ gene abundances, differed by relative elevation and management. In all aspects of DEA, the restored wetlands were more similar to the natural wetlands than to the converted wetland.