Abstract: Atmospheric nitrogen deposition and resin tapping alter tree growth and metabolism, with consequences on soil nutrient cycling and enzyme activities. Soil enzymes and enzymatic stoichiometry can reveal soil carbon and nitrogen cycling and the nutrient limitation of microbial growth and metabolic processes. However, the responses of soil enzymes and enzymatic stoichiometry to nitrogen addition and resin tapping of slash pine (Pinus elliottii) plantation in subtropical area are still unclear. In this study, a field experiment was conducted to examine the effects of three nitrogen addition levels (CK: 0 kg N·hm^-2·a^-1; LN: 50 kg N·hm^-2·a^-1; HN: 100 kg N·hm^-2·a^-1) and resin tapping (RT, resin tapping; NRT, no resin tapping) on the activities of soil hydrolytic enzyme, oxidat6ion enzyme, and their stoichiometry in a slash pine plantation. Resin tapping significantly decreased soil pH, total phosphorus (TP) content and microbial biomass carbon (MBC), while significantly increased dissolved organic carbon (DOC) content. Nitrogen addition significantly reduced soil TP and DOC contents. Nitrogen addition and RT interactively affected the contents of dissolved organic nitrogen (DON) and ammonium nitrogen (NH₄⁺-N). Resin tapping significantly decreased the activity of soil catalase (CAT) and the ratio of soil sucrase/acid phosphatase (E_C/P), but significantly increased the activity of soil acid phosphatase (ACP). HN addition significantly suppressed soil urease (URE) activity in NRT stands, while LN addition significantly promoted CAT activity in RT stands. In the NRT stands, N addition significantly decreased soil E_N/P, while HN addition significantly increased soil E_C/N. Results of redundancy analysis showed that changes in soil enzyme activity and enzymatic stoichiometry were mainly driven by the variations of soil TP and DOC content under N addition. In conclusion, N addition exacerbated soil microbial C and P limitation, and N addition and resin tapping changed soil C, N and P cycling in slash pine plantations.

Key words: nitrogen addition, resin tapping, enzyme activity, enzymatic stoichiometry, slash pine plantation.