Flooding duration affects the temperature sensitivity of soil extracellular enzyme activities in a lakeshore wetland in Poyang Lake, China.

Extracellular enzymes play central roles in the biogeochemical cycles in wetland ecosystems. Their activities are strongly impacted by hydrothermal conditions. Under the ongoing global change, many studies reported the individual effects of flooding and warming on extracellular enzyme activities, however, few researches investigated their interactive effects. Therefore, the current study aims to determine the responses of extracellular enzyme activities to warming in wetland soils under divergent flooding regimes. We investigated the temperature sensitivity of seven extracellular enzymes related to carbon (α-glucosidase, AG; β-glucosidase, BG; cellobiohydrolase, CBH; β-xylosidase, XYL), nitrogen (β-N-acetyl -glucosaminidase, NAG; leucine aminopeptidase, LAP), and phosphorus (Phosphatase, PHOS) cycling along the flooding duration gradient in a lakeshore wetland of Poyang Lake, China. The Q value, calculated using a temperature gradient (10, 15, 20, 25, and 30 °C), was adopted to represent the temperature sensitivity. The average Q values of AG, BG, CBH, XYL, NAG, LAP, and PHOS in the lakeshore wetland were 2.75 ± 0.76, 2.91 ± 0.69, 3.34 ± 0.75, 3.01 ± 0.69, 3.02 ± 1.11, 2.21 ± 0.39, and 3.33 ± 0.72, respectively. The Q values of all the seven soil extracellular enzymes significantly and positively correlated with flooding duration. The Q values of NAG, AG and BG were more sensitive to the changes in flooding duration than other enzymes. The Q values of the carbon, nitrogen, and phosphorus-related enzymes were mainly determined by flooding duration, pH, clay, and substrate quality. Flooding duration was the most dominant driver for the Q of BG, XYL, NAG, LAP, and PHOS. In contrast, the Q values of AG and CBH were primarily affected by pH and clay content, respectively. This study indicated that flooding regime was a key factor regulating soil biogeochemical processes of wetland ecosystems under global warming.