中文摘要：

中国草地样带贯穿我国主要草原区域，具有规律性的草地类型转换和气候条件变化，探究其不同功能群植物氮磷含量随水热因子（温度和降水）的变化规律，对于揭示区域植物N、P元素特征对气候变化的响应机制具有重要意义。本文以中国草地样带为平台，共设置132个样地，采集329份植物叶片样品，基于生态化学计量学理论，对中国草地样带青藏高原高寒区域和内蒙古温性草原区域植物群落功能群组成（豆科、禾本科、莎草科、杂类草）进行N、P元素组分分析，揭示青藏高原高寒区域和内蒙古温性草原区域植物N、P元素含量随温度和降水的变化规律。结果显示：1）青藏高原高寒区域的植物N、P元素含量显著高于内蒙古温性草原区域；2）豆科植物N、P元素含量最高，禾草类植物N、P元素含量最低；3）总体上，随年降水量和年均温度变化，不同功能群中仅杂类草与莎草科植物叶片N、P元素含量变化显著。研究表明，物种组成会影响到草地植被N、P元素生态化学计量学特征，不同功能群植物N、P元素含量对温度和降水变化的响应不同，杂类草和莎草科植物元素含量对中国草地样带植物整体水平N、P元素含量随水热因子的变化规律有重要贡献。

英文摘要：

Traversing from Inner Mongolia to QinghaiTibet Plateau, China Grassland Transect （CGT） spans large climate gradients with main grassland types distributed. Elucidating the variation of N and P contents of different plant functional groups in terms of climatic factors （precipitation and temperature） is important to reveal the mechanisms of plant N and P contents in response to climate change. In this study, we divided CGT into two parts： the QinghaiTibet Plateau alpine region and the Inner Mongolia steppe region, then measured the nitrogen （N） and phosphorus （P） contents for 329 leaf samples collected at 132 sites along CGT. Based on the ecological stoichiometry theory, we aimed to explore the spatial patterns of N and P contents for different plant functional groups （legumes, grasses, sedges and forbs） in relation to the climatic factors. The results showed that, （1） the N and P contents of plants in QinghaiTibet Plateau alpine region were significantly higher than those in Inner Mongolia steppe region; （2） among different functional groups, legumes had the highest N and P contents and grasses had the lowest N and P contents; （3） in general, N and P contents of sedges and forbs significantly varied with mean annual precipitation and mean annual temperature. Our results also indicated that composition of plant community could affect the patterns of plant N∶P at community level. The correlations between N and P contents and climatic factors varied among plant functional groups, and forbs and sedges contributed mostly to the spatial pattern of communitylevel N and P contents with the changes in precipitation and temperature across the grassland transect.