Biogeochemical changes during early development of restored calcareous wetland soils

Preservation and restoration of wetlands is critical to maintain their key functional roles of improving water quality, carbon sequestration, and mitigation of greenhouse gas emissions. Restoration of former agricultural wetlands often requires severe measures including removal nutrient-enriched soil followed by natural succession involving changes in nutrient storages and transformations. The focus of this study was to assess changes in biogeochemical parameters during the early stages of soil development following complete soil removal in a calcareous subtropical wetland. Results indicated that significant changes occur in the first 16 years including increased soil depth, accumulation of organic matter, carbon (C), nitrogen (N), and phosphorus (P). Early development of soils showed a shift from initial N limitation towards a state of co-limitation by N and P after 16 years. Functional responses of these changes were determined by monitoring the microbe-driven processes (enzyme activities and soil oxygen demand) with respect to the nutrient changes. Soil β-glucosidase activity increased in the first few years and then declined with age of the soils. Alkaline phosphatase activity was inversely correlated to the P concentration in soils. When compared with an undisturbed reference site, these parameters indicate that N processes recover more rapidly than those of P and C, but functional attributes related to P limitation should begin to mimic restored conditions within the next century.