氮循环包括氮在生态系统各个组分间的迁移和转化的全部过程，具有整体性和复杂性。人类活动极大的增加了森林生态系统的氮输入，改变了系统原有的氮循环模式和进程。然而，目前的研究大多集中在氮循环的单一或局部过程，很难从生态系统水平上反映氮循环的整体变化，从而无法准确获知不断加剧的氮沉降在生态系统层面上对森林氮循环的影响。本课题拟以广东省鼎湖山南亚热带森林生态系统为研究对象，通过整合该地区已有研究结果，结合大样地定期调查，构建氮循环网络模型，利用生态网络分析（ENA）从整体和全局的视角揭示南亚热带森林生态系统氮循环特征，比较不同形态氮输入（铵态氮和硝态氮）对森林生态系统氮循环的影响。该研究有利于更好的认识南亚热带森林生态系统氮循环对氮沉降的响应机制，进而为制定合理有效的氮管理措施提供科学依据

The nitrogen cycle involves the movement of nitrogen among various components of the ecosystem, which is of integrity and complexity. Human activities have greatly increased the nitrogen input to forest ecosystems, which greatly alters the processes of the nitrogen cycle. However, current studies mostly focus on partial processes of the cycle, and provide little information about the changes of the nitrogen cycle at the system level. Thus, it is important to systematically integrate previous pieces of knowledge and investigate how the nitrogen cycle responds to nitrogen deposition as a whole. This project aims to develop nitrogen cycling network of southern subtropical forest ecosystem at Dinghushan, and uses Ecological Network Analysis (ENA), from a holistic perspective, to study system-wide properties of the nitrogen cycle, and the effects of nitrogen deposition on the nitrogen cycle. This project helps to understand the responses of nitrogen cycle to nitrogen deposition and provides scientific basis for making management policies.