Hydrologic gradients and topsoil additions affect soil properties of Virginia created wetlands

As the role of soil properties in the development of created wetlands (CWs) has not received adequate attention in regulatory or scientific communities, this study was conducted to evaluate the development of soil properties in 11 CWs in Virginia ranging from 4 to 16 yr since creation. Six of the 11 sites received at least 15 cm of topsoil (TS) while the other five sites received no topsoil (No TS). Cores collected from wet, intermediate, and dry positions at each site were analyzed for moisture, bulk density (Db), soil organic matter (SOM), texture, water-holding capacity (WHC), P sorption index (PSI), and microbial biomass C (MBC). Both positions along the hydrologic gradient and topsoil status were hypothesized to be significant factors in explaining the variability of the measured soil properties. Soil moisture decreased significantly while Db increased significantly from wet to dry zones. Moisture, WHC, and PSI were all significantly elevated in certain zones of TS compared with No TS sites. Soil organic matter had significant Spearman correlations with all other measured soil properties, revealing that this parameter was an important indictor of soil quality. In addition, sites with high mean moisture, SOM, and PSI values all received TS; conversely, the site with the lowest mean moisture and SOM content did not receive TS. Thus, amending CW soils with TS appeared to be an effective strategy for increasing soil moisture, WHC, and PSI. Whenever possible, practices such as TS or organic amendments should be employed, especially if wetland creation involves excavation into subsoils with low SOM and high Db.

Duke Scholars

Author Curtis J. Richardson Environmental Sciences and Policy