根据青藏高原高寒草原生态系统中以降水量为主要驱动力的东西样带和以气温为主要驱动力的南北样带内植被土壤的实测数据,分析了这一区域植被碳密度的分布特征及其与气候因子之间的关系。结果表明,在南北样带内(北纬28°46′~31°40′),植被碳密度首先随纬度的增加而增加,当纬度达到约北纬30°16′处,植被碳密度达到最大值0.8731 kg.m-2,之后,则随纬度的增加而减少,植被碳密度总体上呈现出南北低、中间高的分布特征;在东西样带内(东经80°02′~91°50′),植被碳密度随经度的增加而增加,呈现出东高西低的分布特征。在南北样带内植被碳密度与年均降水量和年均气温之间的偏相关系数均达到极显著水平,而在东西样带内植被碳密度与年均降水量和年均气温之间的偏相关系数也均达到显著水平;在南北样带内植被碳密度先随年均气温和年均降水量的增加而增加,当年均气温达到约-1.5℃、年均降水量达到约497.0 mm时,植被碳密度达到最大值1.329 6 kg.m-2,之后,随年均气温和年均降水量的增加而减少;在东西样带内植被碳密度也先随年均气温和年均降水量的增加而增加,当年均气温达到约0.7℃、年均降水量达到约409.0 mm时,植被碳密度达到最大值1.208 3 kg.m-2,之后,随年均气温和年均降水量的增加而减少。研究结果显示,青藏高原高寒草原生态系统南北样带和东西样带内的植被碳密度分布均是年均气温和年均降水量综合作用的结果,且年均降水量的作用大于年均气温。

Taking vegetation of nineteen grassland types of four natural transects ( alpine grassland，alpine shrub and meadow，mountain semidesert and desert，mountain shrub steppe) in alpine steppe ecosystem in Tibetan Plateau as research objects，distribution characteristics of vegetation C / N value and its influence factors in alpine steppe ecosystem were studied by means of combining field investigation and laboratory analysis． The results show that the vegetation C / N value of alpine steppe ecosystem in Tibetan Plateau appears generally a tendency with lower in east and west parts and higher in the middle part of Tibetan Plateau，and a patch distribution pattern． There are obvious differences in C / N value of above-ground part and root among different natural transects and different grassland types，and C / N value in above-ground part is higher than that in root． Average C / N value in above-ground part of vegetation of nineteen grassland types is 34． 17 with coefficient of variation ( CV) of 35． 87% ，and that in root is 29.58 with CV of 40． 02% ． While that in above-ground part of vegetation of four natural transects is 31． 98 with CV of 13． 82% ，and that in root is 31． 86 with a CV of  6.92% ． Ｒegression analysis result shows that C / N value in above-ground part of vegetation has a significant positive correlation with above-ground part biomass，total N and total K contents in soil，and has a significant negative correlation with vegetation height; C / N value in root has a significant positive correlation with altitude and soil bulk density in 20－30 cm soil depth，and has a significant negative correlation with mean annual precipitation and mean annual evaporation． And these factors are the key environmental factors influencing vegetation C / N value of alpine steppe ecosystem in Tibetan Plateau． General，the influence of geographical，climatic and soil physical factors on vegetation C / N value of alpine steppe ecosystem in Tibetan Plateau is not significant，while that of vegetation and soil chemical factors is significant．