雅鲁藏布江巨柏分布区植物群落特点、分布与环境解释

在植物群落和环境特征的野外调查观测基础上，通过双向指示种分析(TWINSPAN)聚类和典范对应分析(CCA)排序的方法，研究了巨柏(Cupressus gigantea)分布区植物群落分布及与环境的关系．结果表明:巨柏分布区植物群落结构简单，可分为3类，包括巨柏群落、巨柏-白莲蒿(Artemisia sacrorum)群落和高山松(Pinus densata)群落．CCA排序结果显示:第1排序轴与海拔和土壤含水量、密度、质地关系显著，主要反映水热和土壤条件的影响；第2排序轴与纬度、坡向和土壤磷含量、年降雨量、土壤全钾、土壤氮磷比相关，主要反映土壤营养、降水和光照条件的变化．影响该区域群落分布变化的主要原因是海拔和坡向变化造成的水热差异，以及土壤理化性质的不同．巨柏群落、巨柏-白莲蒿群落、高山松群落分布的主要海拔范围分别为3 000~3 400、>3 400~3 500、>3 500~3 600 m．研究结果为深入认识巨柏分布区的植物群落环境特征提供了科学参考，有助于更加有效地保护巨柏植物资源． 

Community characteristics,distribution and environment interpretation of Cupressus gigantea along Yarlung Zangbo River in Tibet

It is important to understand the dynamics of plant community and its response to environmental change．Cupressus gigantea is a national-level protected plant distributed from Milin county to Lang county along the Yarlung Zangbo River．Two-way indicator species analysis (TWINSPAN) clustering and Canonical Correspondence Analysis (CCA) ordination were used to study plant community distribution and its relationship with environment．Plant communities in C. gigantea distribution area showed a simple structure and could be divided into C. gigantea community, C. gigantea-Artemisia sacrorum community and Pinus densata community．Canonical Correspondence Analysis showed that the first axis was significantly related to elevation and soil water content, soil bulk density and soil texture, mainly reflecting influence of moisture and thermal conditions, and soil properties．The second axis was related to latitude, slope aspect, soil phosphorus content, annual precipitation, soil total potassium and soil nitrogen-phosphorus ratio, mainly reflecting changes in soil nutrients, precipitation and light conditions．Two determining factors for community distribution were: difference in moisture and thermal conditions induced by changes in elevation and slope aspect, difference in soil physical and chemical properties．The main distribution altitudinal ranges of C. gigantea community, C. gigantea-Artemisia sacrorum community and Pinus densata community were 3000-3400, >3400-3500 and >3500-3600 m, respectively．These data are important to understand environmental characteristics of plant communities in the distribution area of C. gigantea, and will help to protect plant resources of C. gigantea more effectively．