We investigated the impacts of 14-year continuous N addition on activities of arylsulfatase (AS) and phosphodiesterase (PDE), which catalyze soil organic sulfur (S) and phosphorus (P), respectively. The response of AS to N addition was compared with that of C- and N-acquiring enzymes, i.e., β-1,4-glucosidase (BG), β-D-cellobiohydrolase (CBH), β-1,4-Xylosidase (BX), β-1,4-N-acetyl-glucosaminnidase (NAG), and leucine amino peptidase (LAP). We also compared the impact of N addition on PDE activity with that on phosphomonoesterase (PME) activity. The results showed that N addition clearly decreased soil AS activity, whereas activities of C- and N-acquiring enzymes did not exhibit similar changes. The inconsistent response of AS activity with the enzymes was attributed to soil acidification induced by long-term N addition, which shifts the pH condition to a more optimal condition for AS activity and accelerates the accumulation of S in soils. The ratio of PME to PDE were significantly elevated by N addition, implying that the microbial and plant resource allocation to PME relative to PDE increased after N addition at our study site. The shift in resource allocation may have occurred because (i) the types of phosphatases secreted by biota shifted toward phosphatases that require one-step reaction to obtain P (such as PME) in the more-severely P-depleted condition, or (ii) soil acidification provided a more optimal condition for PDE than PME, which resulted in lower PDE production appearing as lower enzyme activity at the same pH condition in the laboratory. Overall, our results indicated different responses of exoenzyme activities to external N input. This highlights the importance of atmospheric N deposition on microbial activity and collateral C and nutrient dynamics in tropical natural forests.

我们调查了连续添加14年氮对芳基硫酸酯酶（AS）和磷酸二酯酶（PDE）的活性的影响，芳基硫酸酯酶和磷酸二酯酶分别催化土壤有机硫（S）和磷（P）。比较了AS对氮添加的响应与C和N获取酶的响应，即β-1,4-葡糖苷酶（BG），β-D-纤维二糖水解酶（CBH），β-1,4-木糖苷酶（ BX），β-1,4-N-乙酰基葡糖酰胺酶（NAG）和亮氨酸氨基肽酶（LAP）。我们还比较了添加氮对PDE活性和对磷酸单酯酶（PME）活性的影响。结果表明，氮的添加明显降低了土壤的AS活性，而获得C和N的酶的活性没有表现出相似的变化。酶对AS活性的不一致反应归因于长期添加氮导致土壤酸化，这将pH值条件改变为更适合AS活性的条件，并加速了S在土壤中的积累。添加氮显着提高了PME与PDE的比例，这意味着在我们的研究地点添加N后，相对于PDE，PME的微生物和植物资源分配增加了。资源分配的变化可能是由于（i）生物区系分泌的磷酸酶的类型向需要一步反应以在更严重的P耗尽条件下获得P（例如PME）的磷酸酶转变，或（ii）土壤酸化为PDE提供了比PME更理想的条件，这导致较低的PDE产生表现为在实验室中相同pH条件下酶活性较低。总体而言，我们的结果表明外切酶活性对外部氮输入的不同反应。