[Effect of nitrogen and phosphorus addition on soil enzyme activities: A meta-analysis]

We conducted a meta-analysis to analyze the effects of nitrogen (N) and combined N and phosphorus (N+P) addition on soil enzyme activities, which being involved in soil carbon (C), N, and P cycles as well as oxidative processes. Nitrogen addition significantly increased the activities of soil C acquisition enzymes, N acquisition enzymes, and P acquisition enzymes by 6.9%, 5.6% and 10.7%, respectively, while the enhancement was much stronger under N+P treatment with 13.4%, 37.4% and 13.3%, respectively. In contrast, both N addition and N+P addition decreased the activities of oxidative enzymes by 6.1% and 0.4%, respectively. The effect sizes of N and N+P addition on soil enzyme activities varied with ecosystem types, N fertilizer types, N addition rates, and the duration of fertilization experiments. Our results suggested that the changes in soil microbes and their enzymes under increasing N deposition and P addition would have profound impacts on soil biogeochemical processes and functions.