Abstract: Based on the genomic amplification technology,the effects of six mixingpatterns of yak and Tibetan sheep grazing on the structure of soil microbial community were analyzed,and the differences in vegetation,soil and soil microorganism under the same grazing intensity and different grazing modes were analyzed in combination with the physical and chemical indexes of vegetation and soil. The results showed that grazing significantly reduced the aboveground biomass of vegetation,in which legume biomass decreased by 90.9%,and there was no difference in aboveground and underground biomass and coverage between different grazing methods. The contents of soil organic matter,total nitrogen and total phosphorus increased under the mixed grazing of yak and sheep,but decreased under the single grazing of yak or sheep. The Shannon index,Simpson index and Pielou index of soil fungi were not affected by different grazing methods. The chao1 index and Shannon index of bacteria increased under the single grazing of yak,while the Shannon index of bacteria decreased under the single grazing and mixed grazing of sheep;the diversity index of bacteria decreased significantly under the grazing of yak and sheep. The proportion of basidiomycetes in fungi was studied,and different grazing patterns had little effect on the horizontal abundance of basidiomycetes. The results of this study showed that under the same grazing intensity,different grazing patterns of yak and sheep had little effect on the grassland vegetation index,but significantly changed the soil nutrient content,the community composition of soil bacteria and fungi. Compared with single grazing of yak and sheep,mixed grazing of yak and sheep helped to improve the soil carbon,nitrogen and phosphorus content.

Key words: Grazing, Alpine grassland, Aboveground biomass of vegetation, Diversity of microbial community structure, Soil nutrients

摘要： 为探究牦牛、藏羊六种不同组合放牧对土壤微生物群落结构的影响，本试验选择青藏高原高寒草原为研究对象，基于基因组扩增子技术，分析相同放牧强度不同放牧方式下植被、土壤以及土壤微生物的差异。研究结果显示，放牧显著降低植被地上生物量，其中豆科生物量降幅达到90.9%，放牧对植被地下生物量以及盖度影响较小。土壤有机质、全氮、全磷含量在牛、羊混合放牧下增加，在牛、羊单牧下降低；各放牧方式对土壤真菌Shannon指数、Simpson指数和pielou指数均没有显著影响，单牛放牧增加真菌Chao1指数和细菌的Shannon指数，而单羊放牧和混合放牧均降低细菌多样性指数；放牧显著降低了真菌担子菌门比例，不同放牧方式对细菌门水平丰度影响不大。本研究结果表明相同放牧强度下，不同牛、羊放牧组合对草地植被指标的影响差异不大，但显著改变了土壤养分含量、土壤细菌和真菌的群落组成，相比牛、羊单牧，牛羊混合放牧有助于提高土壤碳氮磷含量。

关键词: 放牧, 高寒草原, 植被地上生物量, 微生物群落结构多样性, 土壤养分