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

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