Variation of soil enzyme activities and correlations with labile organic carbon fractions in different types of wetlands in the Sanjiang Plain, Northeast China

In the present study, we investigated soil dehydrogenase, amylase, invertase, and beta-glucosidase activities, microbial biomass carbon (MBC), dissolved organic carbon (DOC), easily oxidizable organic carbon (EOC), and soil organic carbon (SOC) in Calamagrostis angustifolia-dominated meadow wetland, constructed wetland, and four riparian wetlands located at Qinglong, Bielahong, Nongjiang, and Yalv Rivers' drainage basins in the Sanjiang Plain, Northeast China. The objective of our study was to test the effect of wetland type on soil enzyme activities and labile organic carbon (LOC) fractions. Our results showed that soil enzyme activities varied with wetland type. Among the selected wetland types, the riparian wetland in the Qinglong Valley had the highest soil amylase, invertase, and P-glucosidase activities, while C. angustifolia-dominated meadow wetland had the highest dehydrogenase activity. Moreover, wetland cultivation decreased soil dehydrogenase, amylase, invertase, and beta-glucosidase activities and MBC, DOC, EOC, as well as SOC contents. In addition, we observed positive correlations between soil dehydrogenase, amylase, invertase, and beta-glucosidase activities and MBC, as well as EOC and SOC. Meanwhile, soil dehydrogenase activity was positively correlated with DOC. Our results suggest that, soil enzyme activities play important roles in carbon cycling in wetland soil, and thus can be considered as biological indicators of soil quality in wetland ecosystems.