Abstract: Livestock grazing is the dominant use way of alpine grasslands in the Tibetan Plateau,and has important impact on grassland ecosystems. However,the integrated response patterns of microbial biomass to grazing intensity in the Tibetan Plateau remains unclear. Therefore,this paper quantified the changes of organic carbon,total nitrogen content and microbial biomass in the surface soil (0~10 cm) of alpine grasslands in the Tibetan Plateau with different grazing intensities using Meta-analysis. The results showed that heavy grazing significantly reduced soil organic carbon,total nitrogen,microbial biomass carbon and microbial biomass nitrogen contents by 24.5%,16.0%,29.3% and 24.7%,respectively;and heavy grazing reduced the biomass of bacteria,fungi and actinomycetes. In addition,linear mixed-effects model analysis showed that soil microbial biomass carbon and soil microbial biomass nitrogen content were positively correlated with soil organic carbon and total nitrogen content under heavy grazing intensity. In conclusion,heavy grazing had significant negative effects on soil nutrients and microbial biomass in alpine grasslands of the Tibetan Plateau,and low grazing pressure should be adopted in order to maintain grassland plant diversity and ecosystem function.

Key words: Qinghai-Tibetan Plateau, Grazing intensity, Soil microbial biomass, Meta-analysis

摘要： 家畜放牧是青藏高原高寒草地最主要的利用方式，对草地生态系统具有重要影响。然而青藏高原微生物生物量对放牧强度的综合响应模式仍不清楚。因此，本文采用Meta分析方法，对青藏高原高寒草地不同放牧强度表层土壤(0~10 cm)有机碳、全氮含量及微生物生物量变化进行了定量分析。结果表明，重度放牧显著降低了土壤有机碳、全氮、微生物生物量碳和微生物生物量氮含量，降幅分别为24.5%，16.0%，29.3%和24.7%；且重度放牧降低了细菌、真菌和放线菌的生物量。此外，线性混合效应模型分析表明，土壤微生物生物量碳和土壤微生物生物量氮含量在重度放牧强度下与土壤有机碳和全氮含量呈正相关关系。综上，重度放牧对青藏高原高寒草地土壤养分和微生物生物量具有显著的负效应，为维持草地植物多样性和生态系统功能，应保持较低的放牧压力。

关键词: 青藏高原, 放牧强度, 土壤微生物生物量, Meta分析