Soil extracellular enzyme activities and stoichiometric characteristics in a warm-temperate-subtropical mixed coniferous and broad-leaved forest under nitrogen addition and drought conditions.

We focused on soils from coniferous-broadleaf mixed forests in the transition zone between warm tempe-rate and subtropical climates. Based on a 9-year field manipulative experiment with factorial treatments of nitrogen addition (50 kg N·hm-2·a-1) and drought (50% precipitation reduction). Soil extracellular enzyme activities involved in carbon, nitrogen, and phosphorus cycling and their stoichiometric characteristics were determined. Results showed that nitrogen addition significantly increased the activity of soil β-glucosidase (βG), soil enzyme stoichiometric carbon-nitrogen ratio (EC:N) and soil enzyme stoichiometric carbon-phosphorus ratio (EC:P) by 113.1%, 158.5%, and 126.8%, respectively. Drought significantly reduced the activity of soil acid phosphatase (AP) by 69.3%, while EC:N and EC:P increased significantly by 125.9% and 133.0%. Nitrogen addition combined with drought treatment significantly increased soil βG activity and EC:P by 106.5% and 129.8%, respectively. Additionally, nitrogen addition combined with drought treatment significantly increased soil AP and β-N-acetylglucosaminidase (NAG) activities, whereas drought attenuated the positive effects of nitrogen addition on soil βG, EC:N, and EC:P. Soil cellulose hydrolase (CBH) activity was significantly positively correlated with soil water content. Soil βG activity was significantly positively correlated with dissolved organic carbon, nitrate, and ammonium. Soil AP activity was significantly positively correlated with ammonium. Soil NAG activity was significantly positively correlated with dissolved organic carbon and ammonium. In conclusion, nitrogen addition and drought interactively affected soil extracellular enzyme activities and their stoichiometric characteristics in a warm-temperate to subtropical mixed coniferous and broad-leaved forest, indicating that drought may alter the influence of nitrogen addition on soil microbial enzymatic strategies for nutrient acquisition.