Spatial variability of soil properties in created, restored, and paired natural wetlands

To better understand patterns of spatial variability in soil properties of created wetlands (CWs), restored wetlands (RWs), and natural wetlands (NWs), we sampled four CW or RW-NW pairs in the Coastal Plain of North Carolina using a spatially explicit design. The site pairs spanned a range of hydrogeomorphic (HGM) settings common in the Coastal Plain. We hypothesized that: (i) spatial variability of soil properties in riverine wetlands would be structured along gradients running perpendicular to streams, while spatial variability of soil properties in nonriverine wetlands would be structured in patches related to local factors (microtopography, vegetation); and (ii) soil properties of CWs and RWs would exhibit less spatial variability than soil properties of NWs as prior land-use and mitigation activities tend to homogenize soil properties. Trend surface analysis revealed that even in plots selected for homogeneous topography, linear and nonlinear trends were present in CWs, RWs, and NWs across all subclasses. Moran's I analysis indicated that fine-scale variability for bulk density (Db), soil organic matter (SOM). and pH was more prevalent in NWs than in paired CWs or RWs. At certain sites, prior land-use and mitigation activities reduced spatial variability of soil properties such as sand content, while at other sites, they increased or had no effect on variability of soil properties such as SOM. Thus, patterns of variability were complex and differed among soil properties, sites, and HGM subclasses. A better understanding of this phenomenon will help us to incorporate appropriate variability into wetland mitigation design and construction, improving creation and restoration of functional wetlands.

Duke Scholars

Author Curtis J. Richardson Environmental Natural Science