中文摘要：

以分布于青藏高原东北缘的优势乔木祁连圆柏为研究对象,分析了叶片δ13C值变化及其与树高、土壤含水量、降雨量和叶片碳氮含量的关系.研究结果表明：研究区祁连圆柏叶片δ13C值的变化范围为-28.58‰～-23.95‰,平均值为-25.66‰,变化幅度为4.63‰,而同一生境不同个体之间的变化幅度为2.69‰和2.93‰,说明祁连圆柏叶片δ13C值的变化是植物自身遗传特性与环境因子共同作用的结果.叶片δ13C值与树高呈明显的负相关关系（p〈0.01）,并且这种关系不随采样位点的不同而改变;与叶片C和N含量不相关,而与土壤含水量和年平均降水量显著负相关（p〈0.001）.

英文摘要：

The foliar stable carbon isotopic composition（ δ13C） of Sabina przewalskii Kom.,a dominant tree population on the northeast Tibetan Plateau,and its correlation with foliar carbon and nitrogen contents,tree height,precipitation and soil moisture are examined. The results showthat δ13C values range from- 28. 58‰ to- 23. 95‰,with an average of- 25. 66‰. The individual variation range of δ13C value,respectively,is2. 69‰ and 2. 93‰ in two homogenous habitats,which indicates that the variation of foliar δ13C is determined by both botanical genetic character and environmental factors. The correlation of δ13C with tree height is strongly negative（ p 〈0. 01）,and the negative correlation do not vary with sample sites. Foliar δ13C do not correlate with foliar nitrogen and carbon contents. The correlations of δ13C with soil moisture and precipitation are remarkably negative（ p 〈0. 001）.