日益增加的大气氮沉降深刻影响陆地生态系统土壤磷循环。尤其对于生态环境脆弱的西南喀斯特生态系统，氮沉降驱动的土壤磷转化及磷有效性的变化可能对该地区退化生态系统恢复进程和关键生态功能产生深远影响，然而目前关于该地区土壤磷循环对氮沉降的响应及其机制的认识非常有限。针对这一问题，本项目以喀斯特地区分布面积最大的灌丛生态系统为研究对象，基于模拟氮沉降控制试验，通过长期定位观测，明确氮沉降对土壤磷组分及磷有效性的影响；结合培养实验，分析土壤磷转化主要指标的变化，探明磷转化过程对氮沉降的响应；结合磷脂脂肪酸方法和高通量测序等实验手段，分析土壤理化性质、酶活性、磷转化相关基因丰度和土壤微生物群落结构等指标，阐明氮沉降背景下土壤磷转化和有效性的主要影响因素，揭示氮沉降影响土壤磷转化的作用机制。研究结果有助于预测和评估喀斯特生态系统土壤磷素供应能力的变化，为该地区植被恢复管理和生态保护决策提供科学依据。

Soil phosphorus cycle of terrestrial ecosystems are deeply affected by the increasing atmospheric nitrogen deposition. The transformation and availability of soil phosphorus effected by nitrogen deposition might deeply affect the process of degraded ecosystems restoration and some important ecological functions, especially on the ecologically fragile regions in karst ecosystem in southeast of China. However, the mechanisms of the soil phosphorus cycle under the background of elevated atmospheric nitrogen deposition are not clear. The main proposes for this project can be summarized such that: (1) We will conduct a simulated nitrogen deposition control experiment and long term monitoring to study transformation and availability of soil phosphorus in the shrub ecosystem, which is the largest ecosystem in karst regions of China. (2) We attempt to monitor the major indicators which are represented soil phosphorus transformations using soil incubation experiment, and then combine with the results of (1) to explain the effect of nitrogen deposition on phosphorus transformation process. (3) Soil physicochemical properties, enzymatic activity, gene abundance and soil microbial community structure related to phosphorus transformation will be measured by using PLFA, high-throughput sequencing, etc., which will be used to determine the controlling factors of soil phosphorus dynamics, and then to reveal the mechanisms underlying the impacts of nitrogen deposition on phosphorus transformation of karst shrub ecosystems. The results will be useful for estimating the soil phosphorus supply and availability in karst ecosystems, and providing scientific supports for vegetation restoration management and policy making on eco-environmental protection to degraded ecosystems.