Different responses of soil hydrolases and oxidases to extreme drought in an alpine peatland on the Qinghai-Tibet Plateau, China

Abstract

Extracellular enzyme activities (EEA) in soils play a pivotal role in ecosystem processes, such as organic carbon (C) decomposition or nitrogen (N) and phosphorus (P) mineralization. Thus, EEA measurements can provide insights into the rates of ecosystem-level processes in peatlands, which will experience more frequent extreme droughts in the future. In the present study, the activities of seven hydrolases and two oxidases involved in the acquisition of C, N, and P were measured in response to simulated extreme drought events during the summer. The combined results of three consecutive years showed that the β-1,4-glucosidase and β-1,4-xylosidase involved in mediating labile-C decomposition increased by 102.63% and 100.63%, respectively. In contrast, the oxidases involved in mediating recalcitrant-C decomposition showed a non-significant decreasing trend, indicating that extreme drought significantly increased the decomposition of cellulose in peatlands. The C-acquisition enzyme, C:P -acquisition enzyme, and N:P-acquisition enzyme activities increased, on average, by 78.45%, 51.57%, and 36.57%, respectively, under extreme drought, impacting the rates of microbial growth and organic matter depolymerization. In addition, the results showed that changes in the C-acquisition enzyme were correlated with shifts in the soil water content, whereas soil oxidases were correlated with soil total C and N contents. Overall, the soil total C content explained 41.9% of the variation in EEA and ecoenzymatic stoichiometry. These results provide an improved understanding of hydrolase and oxidase activities in response to extreme drought events, thereby facilitating the prediction of long-term C dynamics in peatlands.