高寒草甸土壤细菌群落多样性和共现性网络对牦牛觅食强度的响应

牦牛觅食行为是影响青藏高原高寒草甸生态系统的重要因素之一，主要通过采食、践踏和粪便沉积影响土壤生态系统。土壤细菌群落作为土壤生态系统中的重要组成部分，在物质循环和能量流动等方面发挥着关键作用。本文通过在高寒草甸对牦牛进行长期自由放牧处理，分析了不同觅食强度下的细菌群落组成及其共现性网络的变化，揭示了土壤细菌群落对牦牛觅食行为的响应特征。结果表明，细菌群落的优势菌门是变形菌门(Proteobacteria)(30.66%～33.38%)和放线菌门(Actinobacteria)(25.04%～28.99%),牦牛觅食显著增加了疣微菌门(Verrucomicrobia)(2.46～5.10%)和芽单胞菌门(Gemmatimonadetes)(1.91%～2.68%)的相对丰度。牦牛觅食行为主要通过改变土壤pH值显著影响土壤细菌群落beta多样性，共现性网络复杂度随着觅食强度增加而增加，疣微菌门相对丰度的增加显著降低了细菌群落beta多样性和网络复杂度。牦牛觅食行为能够改善细菌群落稳定性，表明适当的觅食强度能够改善脆弱的高寒草甸生态系统。

Response of Soil Bacterial Community Diversity and Co-occurrence Network to Foraging Intensity of Yaks in Alpine Meadow

Yak foraging behavior is one of the most important factors affecting the Tibetan Plateau alpine meadow ecosystem,mainly through foraging,trampling,and dung deposition affecting the soil ecosystem. As an important component of soil ecosystems,soil bacterial communities play key roles in material cycling and energy flow. However,the mechanisms of bacterial community diversity and interactions in response to yak grazing are unclear. In this study,we analyzed the changes in bacterial community composition and its co-occurrence networks under different foraging intensities by long-term free grazing treatment of yaks in alpine meadows,and revealed the characteristics of soil bacterial community response to yak foraging behavior. The results showed that the dominant phyla of the bacterial community were Proteobacteria (30.66%~33.38%) and Actinobacteria (25.04%~28.99%),yak foraging significantly increased the relative abundance of Verrucomicrobia (2.46%~5.10%) and Gemmatimonadetes (1.91%~2.68%). In addition,yak foraging behavior significantly affected soil bacterial community beta diversity mainly by changing soil pH value,co-occurrence network complexity increased with foraging intensity,and an increase in the relative abundance of the Verrucomicrobia significantly reduced bacterial community beta diversity and network complexity. Yak foraging behavior can improve bacterial community stability,suggesting that appropriate foraging intensity can improve fragile alpine meadow ecosystems.