土壤微生物是土壤有机质（SOM）分解的驱动者，随着大气氮（N）沉降增加，南方森林土壤酸化、磷（P）限制作用更加明显，这些环境因子改变对微生物分解SOM功能影响机制还不清楚。本研究选择亚热带杉木林，2011年建成长期定位控制试验，设置对照（CK）、模拟N沉降（N1、N2：50、100 kg N ha-1 a-1）、外源P输入(P，50 kg P ha-1 a-1)、NP同时输入(N1P、N2P：50或100 kg N ha-1 a-1+50 kg P ha-1 a-1)处理，结合室内不同温度梯度培养试验，利用酶动力学、分子生物学技术，探讨SOM分解关键微生物酶活性、功能基因丰度与种群多样性、以及SOM矿化对N、P响应机制。研究结果可为预测未来大气N沉降增加背景下微生物分解SOM的功能提供数据支持，为制订杉木林管理措施提供科学依据。

Soil microorganism is the driver of soil organic matter decomposition. With the increase of atmospheric nitrogen (N) deposition, soil acidity and phosphorus (P) limitation problems in Chinese fir ecosystems are worse in red soil area of southern China. However, it is not clear how microbial functions of soil organic matter decomposition respond to N and P additions in subtropical plantations till now. In this proposal, the Chinese fir (Cunninghamia lanceolata) ecosystem is selected in the Qianyanzhou Forest Experimental Station, in Jiangxi Province, South China (26°44′52″N, 115°04′13″E). Six different treatments as follows: control (CK), low N addition (N1: 50 kg N ha-1 a-1), high N addition (N2: 100 kg N ha-1 a-1), P addition (P: 50 kg P ha-1 a-1), low N and P addition (N1+P: 50 kg N ha-1 a-1+50 kg P ha-1 a-1) and high N and P addition (N2+P: 100 kg N ha-1 a-1+50 kg P ha-1 a-1) were established in 2011. Soil organic matter decomposition enzyme activities, their kinetics, functional gene abundance and microbial diversity of the field samples will be analyzed using enzyme kinetics, molecular biology techniques. Temperature sensitivity of soil organic carbon decomposition and their enzyme kinetics of the field samples will also be analyzed in different temperature incubation chamber in laboratory. The effect mechanism of N and P addition on soil organic matter decomposition will be evaluated. The research results will help to predict the microbial mechanism of soil organic matter decomposition under increasing atmospheric N deposition conditions. Furthermore, it will also help to make reasonable practices for Chinese fir plantations management in the future N deposition conditions.