Abstract: In order to understand the impact of degradation of alpine desert steppe in the southwestern part of Qinghai-Xizang Plateau on soil bacterial communities， we compared non-degraded and degraded grasslands by analyzing plant community characteristics， soil physicochemical factors， and bacterial community structure. The results demonstrated that the non-degraded grasslands exhibited significantly higher plant diversity than the degraded ones. Soil nutrients （including total nitrogen and organic carbon） markedly decreased in degraded grasslands， while pH and available manganese content increased， leading to reduced bacterial diversity. Moreover， bacterial co-occurrence networks in non-degraded grasslands showed greater complexity and tighter connectivity. Overall， the soil environmental factors accounted for 78% of the variation in bacterial communities， with total nitrogen and pH playing pivotal roles. Redundancy analysis （RDA） further revealed that bacterial β-diversity in non-degraded grasslands was positively correlated with total nitrogen but negatively with pH， whereas an opposite pattern emerged in degraded grasslands. These findings collectively indicate that alpine desert steppe degradation alters vegetation and soil properties， thereby restructuring bacterial communities， with soil factors （particularly total nitrogen， available manganese， pH， available copper， and available sulfur） serving as primary drivers.

Key words: Tibetan Plateau, Alpine desert steppe, Degenerate, Soil bacteria, Plant community, Soil physical and chemical factors

摘要： 为了解青藏高原西南部高寒荒漠草原退化对土壤细菌群落的影响，选择未退化草地和退化草地，调查植物群落特征、土壤理化因子及细菌群落结构，分析环境因子对土壤细菌群落组成及多样性的影响。结果表明：未退化草地的植物多样性显著高于退化草地，同时，退化草地的土壤养分（全氮、有机碳等）明显下降，而pH值和有效态锰含量则增加，导致细菌多样性降低，此外，未退化草地的细菌共现网络更复杂，连接关系更紧密。整体来看，土壤环境对细菌群落的影响占78%，其中全氮和pH值起关键作用。RDA分析进一步表明，未退化草地细菌β多样性与全氮等呈正相关，与pH值等呈负相关，而退化草地的情况则相反。综上，高寒荒漠草原退化影响植被和土壤，进而改变细菌群落，其中土壤因子作用更大，全氮、有效态锰、pH值、有效态铜、有效硫是主要驱动因子。

关键词: 青藏高原, 高寒荒漠草原, 退化, 土壤细菌, 植物群落, 土壤理化因子