Resilience of forested wetlands located in the southeastern United States:Demonstration of a soil perturbation index

This study examined the usefulness of soil organic matter (SOM), total orga nic carbon (TOC), total Kjeldahl nitrogen (TKN), and total phosphorus (TP) as indicators of resilience in forested wetlands located within southeast V irginia, USA. These data were also examined as standards for reference wetl ands before and after timber harvesting and for comparisons of mature and e arly successional stages. Results indicate that the wetland soils in this s tudy seem to be relatively resilient to perturbation. Soil total phosphorus was significantly greater in the 0- and 0.5-year stages than the 5-, 8-, a nd 11-year stages (p < 0.05). Although there were no significant difference s in SOM, TOC, and TKN levels before and after timber harvest or between ea rly and mature successional stages, there were consistent trends that may p rove beneficial in determining reference standards. A Soil Perturbation Ind ex was developed by combining all four parameters for soils collected in th e Chowan River watershed to determine extent of deviation from the biogeoch emical reference. Using the model developed in this study, biogeochemical f unctions decrease after harvesting, with the low point reached at approxima tely 8 to 9 years after human alteration. This index predicts that it would take 16-17 years for SOM, TOC, TKN, and TP to return to pre-harvest condit ions. Perturbation indices could be used for assessment of human impacts, r estoration projects, and mitigation of wetlands. We maintain that a Soil Pe rturbation Index can be one useful component of an index of biotic integrit y for wetland ecosystems.