中文摘要：

研究氮沉降对理解未来全球气候变化有着重要的意义。因此，在中国三江湿地开展了两年的氮沉降试验，测定小叶章湿地的光合特性，试图揭示氮沉降对小叶章湿地碳、水通量产生的影响。利用LI-6400一个封闭的光舍测定系统，通过计算CO2的变化量来确定净生态系统CO2交换量。试验结果表明，生长季导致净“碳汇”的产生。而且，低氮和高氮处理均促进生长季的净生态系统气体交换量（NEE）和生态系统水分利用效率（WUE）。在三江平原湿地，大气温度对调节生态系统碳交换以及气候变化的响应起着重要作用，氮沉降能在短期内迅速增加三江湿地的碳通量。但是。要预测长期氮沉降对生态系统造成的影响，我们还需要长期的野外监测。

英文摘要：

Understanding carbon fluxes responses to nitrogen deposition is critical for predicting the productivity and carbon sequestration potential of marsh ecosystems in the 21 ^st century. Measurements of photosynthetic characteristics were made in Ca- lamagrostis angustifolia growing under nitrogen deposition from 2009 to 2010. In situ diurnal net ecosystem CO2 exchange was meas- ured by determining the rise in CO2 in IRGA. The results for the 2 yr showed that gross ecosystem productivity （GEP） was higher than ecosystem respiration,leading to net carbon（C）sink （measured by NEE） over the growing season in the study site. Further- more,low nitrogen and high nitrogen addition all significantly stimulated growing - season NEE and WUE. It was indicated that air temperature played a major role in regulating ecosystem net C exchange and their responses to climatic change in Sanjiang Plain of northern China. We need long - term field studies to predict the long - term effects of N deposition on ecosystem processes.