Abstract: In order to explore the effects of altitude variations on soil nutrient and stoichiometric characteristics of alpine steppe,five alpine gradients (2 512,3 005,3 490,3 977 and 4 493 m) were selected for sampling in the southern part of Qinghai Province,and the above ground biomass,plant community characteristics and soil properties were measured. The results showed that with the increase of altitude,the Shannon index of plant community increased,and the soil bulk density firstly increased and then decreased. The contents of C,N and P ranges were 11.33 to 71.66 g·kg^-1,0.71 to 4.47 g·kg^-1 and 0.30 to 1.05 g·kg^-1 respectively. The contents of C and N increased firstly and then decreased,and P content kept increasing. The ranges of C/N,C/P and N/P were 13.65 to 21.35,39.37 to 90.58 and 2.88 to 4.24,respectively. And the highest values occurred at 3490 m. Correlation and principal component analysis showed that there was a significant positive correlation between altitude and N and P contents (P<0.01),and a significant negative correlation with N/P (P<0.01). The productivity of alpine steppe in the research area was mainly affected by soil N content.

Key words: Three-River Headwaters region, Alpine steppe, Altitude, Soil nutrient, Stoichiometry

摘要： 为探究海拔变化对高寒草原土壤养分及化学计量特征的影响，本试验在青海省南部三江源区选取了5个海拔梯度（2 512，3 005，3 490，3 977和4 493 m）的高寒草原样地，对各样地地上生物量、植物群落特征及不同土层土壤理化性质进行分析。结果表明：在该研究区随着海拔的升高，植物Shannon指数增加，土壤容重先上升后下降；土壤中碳、氮、磷含量变化范围分别是：11.33~71.66 g·kg^-1，0.71~4.47 g·kg^-1，0.30~1.05 g·kg^-1；土壤的碳、氮含量先增后降，磷呈上升趋势；土壤中C/N，C/P，N/P范围分别为13.65~21.35，39.37~90.58，2.88~4.24，均随海拔的增加先升后降，在海拔3 490 m处达到最高。相关性和主成分分析表明，海拔与土壤中氮和磷含量呈现极显著正相关（P<0.01），和N/P呈现极显著负相关（P<0.01）。研究区高寒草原植物生产力主要受氮素的影响。

关键词: 三江源区, 高寒草原, 海拔, 土壤养分, 化学计量特征