Soil Change Influenced by Wetlands Reserve Program in Louisiana, USA: A Chronosequence Approach

Abstract

Wetlands have many valued ecological functions, yet the impact of the Wetlands Reserve Program (WRP) on soil change, such as carbon dynamics, still remains controversial. Soils from four WRP age classes (8, 12, 15, and 18 yr) and adjacent croplands in St. Landry Parish, Louisiana, USA were sampled by fixed depth (0–10, 10–20, 20–30, and 30–40 cm). Soil physiochemical properties such as bulk density (Db), pH, soil organic matter (SOM), total carbon (TC), total nitrogen (TN), and sand, silt, and clay content were analyzed. Results showed that returning cropland to wetland significantly increased porosity and lowered soil pH. Slight changes in soil texture from silty clay to clay were also noted, but may be a feature of soil spatial variability rather than differences imposed by land use. Linear relationships existed between 0 and 40 cm for content of SOM, TC, or TN and WRP age (P < 0.05), illustrating WRP could benefit carbon and nitrogen sequestration. Sequestration rates of SOM, TC, and TN were 0.305, 0.095, and 0.004 kg m–2 yr–1, respectively. Significant correlation relationships existed among most of these soil properties, suggesting human activities such as wetland restoration may trigger co-dynamics of properties in the soil system. These findings highlight the potential of WRP in climate change mitigation, and give some suggestions for better soil management in this restoration program. Peer Reviewed Papers