Abstract: In order to reveal the response mechanisms of seasonal dynamics of species diversity to long-term grazing intensity in stipa breviflora desert steppe. This study took stipa breviflora desert steppe grassland in Siziwangqi Banner as the research object. From May to September 2018,species composition,plant height,coverage and density of desert steppe were observed,and the species diversity,richness and evenness were analyzed. This desert steppe was enclosed for 14 years (2004-2018) under different grazing treatments. The results showed that the Shannon-Wiener diversity index and Margalef richness index of species in the five observation control areas were significantly higher than those in moderate and severe grazing areas. The Shannon-Wiener diversity index and Margalef richness index of species in July and August were higher in the control and grazing treatments,and were smaller in June and September. Variation of Pielou evenness index of different grazing areas was in the order of HG > MG > LG > CK. The effects of month and grazing on species alpha diversity index of Stipa breviflora desert steppe reached a very significant level,and the effects of grazing treatment on species alpha diversity index were greater than that of month. In summary,the study shows that the effects of long-term and heavy grazing on species diversity of Stipa breviflora desert steppe were most obvious in June and September,and threatened the stability of the grassland ecosystem.

Key words: Grazing, Desert grassland, Species diversity

摘要： 为揭示短花针茅（Stipa breviflora）荒漠草原物种多样性季节性动态变化对长期放牧强度的响应机制，本研究以内蒙古四子王旗短花针茅荒漠草原为研究对象，2018年5月至9月对围封14年（2004-2018）不同放牧处理下的物种组成、植物高度、盖度和密度进行观测，并对物种多样性、丰富度和均匀度分析。结果表明：5次观测对照区物种Shannon-Wiener多样性指数、Margalef丰富度指数均显著大于中度放牧区和重度放牧区；所有处理均是7月和8月的物种Shannon-Wiener多样性指数、Margalef丰富度指数较高，6月和9月观测值较小；Pielou均匀度指数变化差异由大到小排序为：重度放牧区 > 中度放牧区 > 轻度放牧区 > 对照样地；月份和放牧对短花针茅荒漠草原物种α多样性指数影响均达到极显著水平，且放牧处理对物种α多样性指数影响效应大于月份。研究认为，长期重度放牧对短花针茅荒漠草原物种多样性的影响在6月和9月表现最为明显，且会威胁草地生态系统的稳定性。

关键词: 放牧, 荒漠草原, 物种多样性