Soil Physicochemical Conditions, Denitrification Rates, and nosZ Abundance in North Carolina Coastal Plain Restored Wetlands

Over the last century, North Carolina has seen a severe reduction in the percentage of wetlands and a rise in negative environmental impacts related to this loss. To counter these effects, efforts have been enacted to mitigate wetland loss and create new wetland areas. The objective of this study was to assess the impact of hydrological restoration at several sites in the North Carolina coastal plain. Nine sites were selected for study. Hydrologically restored wetlands were compared with natural wetlands and prior converted (PC) croplands (i.e., historic wetlands under agricultural production). Each site was analyzed along a relative wetness gradient, and physicochemical properties, denitrification enzyme activity, and N2O reductase gene (nosZ) abundances using real-time PCR were measured. Physicochemically, restoration resulted in significantly increased levels of total C as compared with PC cropland sites. Restored wetland sites also saw pH, soil moisture, P, and NO2- +NO3- approximate levels similar to those of natural wetlands. Denitrification enzyme activity rates varied based on relative wetness within individual sites, generally increasing with increasing soil moisture. However, denitrification tended to be lower in restored wetland sites relative to natural wetlands. Gene abundances of nosZ saw statistically significant decreases in restored wetland soils. In conclusion, although analysis of restored wetlands reveals clear changes in several physicochemical characteristics and significant decreases in nosZ gene abundances, restoration efforts appear to have not significantly affected the denitrification component of the N cycle.