Abstract: Soil temperature and moisture conditions on the Tibetan Plateau have changed significantly over the past 50 years. Many previous studies have focused on the effects of either temperature or moisture changes on microbial communities on the Tibetan Plateau,and relatively few studies have investigated the combined effects of increased temperature and water on the diversity and composition of microbial communities in the context of grazing. In this study,we investigated the responses of soil bacterial community composition,diversity and functional taxa to warming,snow increase and grazing and their interactions in a typical alpine meadow ecosystem of Namtso on the Tibetan Plateau using an in situ controlled experiment of warming and snow increase coupled with grazing. The results showed that warming,snowing and grazing and their interactions did not significantly affect the overall diversity and composition of soil bacteria;snowing and grazing significantly affected the abundance of bacterial communities;warming,snowing and grazing changed the relative abundance of plant populations and microbial parts of populations;and both warming,snowing and grazing reduced the abundance of a wide range of bacterial functional taxa. Bacterial diversity,composition and relative abundance on the Tibetan Plateau are not likely to change dramatically in a short period of time under a warming and humidifying climate trend.

Key words: Warming, Snow increase, Grazing, Microbial communities, Alpine meadow

摘要： 近50年来青藏高原的土壤温度、水分条件发生显著改变。前期许多研究关注了温度或水分变化对青藏高原微生物群落的影响，对于放牧背景下增温增水对微生物群落多样性和组成的耦合影响研究相对较少。本研究在青藏高原纳木错典型高寒草甸生态系统展开，采用增温增雪耦合放牧的原位控制实验，研究了土壤细菌群落组成、多样性和功能类群对增温、增雪和放牧及其交互作用的响应。结果表明，增温增雪和放牧及其交互作用对土壤细菌整体的多样性和组成没有显著的影响，增雪放牧显著影响了细菌群落的丰富度；增温、增雪和放牧改变了植物种群和微生物部分种群的相对丰度；增温增雪和放牧都降低了多种细菌功能类群的数量。在气候暖湿化的趋势下，青藏高原细菌多样性、组成和相对丰度不会在短时间内发生巨大的改变。

关键词: 增温, 增雪, 放牧, 微生物群落, 高寒草甸