SPATIAL VARIABILITY OF DENITRIFICATION POTENTIAL AND RELATED SOIL PROPERTIES IN CREATED, RESTORED, AND PAIRED NATURAL WETLANDS

To gain a better understanding of the spatial patterns of denitrification potential and related soil properties in created (CW), restored (RW), and natural wetlands (NWs), four CW/RW-NW pairs in North Carolina, USA were sampled. These site pairs spanned a range of hydrogeomorphic (HGM) settings common in the Coastal Plain. It was hypothesized that denitrification enzyme activities (DEAs) and related soil properties of CW/RWs would have less spatial variability than DEAs and soil properties of NWs, as prior land-use and mitigation activities tend to homogenize soil properties. Cochran's C tests indicated that variances were significantly lower in CW/RWs than in NWs for most soil properties, and that for nitrate (NO3-N), variances were significantly lower in CW/RWs across all HGM settings. Interpolated maps of the soil properties revealed homogeneous distributions of NO3-N across the CW/RW plots compared to much more heterogeneous distributions of NO3-N across the NW plots. Multiple stepwise regressions confirmed that either NO3-N or soluble organic carbon were significant predictors of the DEA at each plot. Interpolated maps of predicted DEA generally showed similar patterns to those of NO3-N. While some nitrate and DEA hotspots were observed in the CW/RWs, more were present in the NWs. These results indicated that spatial distributions of soil chemical properties and DEAs were considerably different in CW/RWs than in paired NWs. This is the first study to document such differences, suggesting that CWs and RWs with homogeneous soil chemical distributions may not develop the full range of soil biogeochemical processes that occur in NWs.