中文摘要：

氮沉降是全球变化研究的热点问题之一。以内蒙古呼伦贝尔草甸草原优势种羊草为研究对象，分析不同氮化合物和不同剂量氮添加对羊草叶片叶绿素和叶氮含量的影响。结果表明：硝酸铵和硫酸铵两种氮素化合物对叶绿素和叶氮含量的影响没有显著差异；在两种氮添加均显著增加了羊草叶片叶绿素和叶氮含量，且随着氮浓度的增加，叶绿素和叶氮含量呈单峰模式；在两种化合物添加处理下，羊草叶绿素和叶氮含量之间呈显著正相关关系。

英文摘要：

Nitrogen deposition is one of the hot issues of global change research. In order to study the response of plant photosynthesis to different nitrogen compounds deposition, taking the dominated species of Leymus chinensis in meadow steppe in Hulunbuir as the research object, this research analyzed the effect of different nitrogen compounds and different doses of nitrogen added on leaf chlorophyll and leaf nitrogen content of L. chinensis. The results showed that the effects of nitrogen addition on leaf chlorophyll and leaf nitrogen content between ammonium ni- trate and ammonium sulfate were not significant. Both of the two nitrogen compounds addition were significantly increased the leaf chlorophyll and leaf nitrogen content of L. chinensis. The leaf chlorophyll and leaf nitrogen content were in unimodal pattern with the increase of nitrogen doses. There was significantly positive correlation between leaf chlorophyll and leaf nitrogen con- tent of L. chinensis in both ammonium nitrate and ammonium sulfate addition.