Abstract: To clarify the effects of different grazing intensities on the plant community structure， species diversity， and population niche characteristics in desert steppe， reveal the laws of community species replacement and the niche response mechanisms of dominant species， and provide a theoretical basis for scientific grazing management， this study set up four different grazing treatments to analyze changes in community species composition， diversity， and niche characteristics. The results showed that with the increase of grazing intensity， the community species shifted from perennial forbs and shrubs/subshrubs to perennial grasses； grazing significantly reduced the total aboveground biomass of the community and the biomass of various functional groups， and the Shannon-Wiener index， Simpson index， and species richness index. Stipa breviflora， Cleistogenes songorica， and Convolvulus ammannii maintained a wide niche breadth under all grazing treatments， and the niche overlap among species with high niche breadth was generally high， with the niche overlap between Stipa breviflora and Cleistogenes songorica reaching the highest under the heavy grazing treatment. The study indicated that grazing significantly affected the structure of desert steppe communities by altering the resource competition relationships among species. Therefore， grazing intensity should be controlled in desert steppe management to maintain ecosystem stability.

Key words: Desert grassland, Important value, Functional groups, Niche width, Niche overlap

摘要： 为明确不同放牧强度对荒漠草原植物群落结构、物种多样性及种群生态位特征的调控效应，揭示群落物种替代规律与优势种生态位响应机制，提供科学放牧管理理论依据，本研究设置4个不同的放牧处理，分析群落物种组成、多样性、生态位特征的变化。结果显示，随放牧强度的增加，群落物种由多年生杂类草、灌木/半灌木向多年生禾草转变；放牧显著降低群落总地上生物量及各类功能群生物量，同时显著降低 Shannon-Wiener指数、Simpson指数及物种丰富度指数；短花针茅（Stipa breviflora）、无芒隐子草（Cleistogenes songorica）、银灰旋花（Convolvulus ammannii）在各放牧处理下均保持较大生态位宽度，且生态位宽度较高的物种间重叠度普遍较高，其中短花针茅与无芒隐子草的生态位重叠度在 HG下达到最高。放牧通过改变物种间资源竞争关系，显著影响荒漠草原群落结构，因此在荒漠草原管理中应控制放牧强度，以维持生态系统稳定。

关键词: 荒漠草原, 重要值, 功能群, 生态位宽度, 生态位重叠