Livestock grazing is a popular land-use activity for grasslands. Over grazing and trampling of livestock impairs ecosystem function by changing vegetation growth, soil nutrients, and soil bacterial communities. However, information regarding the characteristics of those allied with above- and belowground of grazing-resistant host plant species under different grazers and grazing practices in grassland ecosystems is limited. We examined the impact of single-species grazing of yak only (YG), sheep only (SG), and mixed grazing in the ratio of yak to sheep of 1:2 (MG (1:2)), 1:4 (MG (1:4)), and 1:6 (MG (1:6)) on plant growth, soil properties, and soil microbial communities. Plant biomass and soil properties were measured in each treatment, and soil microbial communities in the rhizosphere soil of Medicago ruthenica were analyzed by high-throughput sequencing of the 16 S rRNA gene. The results showed that shoot height, root length, and plant FW (fresh weight) and DW (dry weight) of M. ruthenica under single-species grazing decreased by 5.60 %, 3.30 %, 11.34 % and 9.82 %, respectively; under mixed-species grazing decreased by 35.65 %, 29.68 %, 52.35 % and 55.60 %, respectively, compared to CK (no grazing). Mixed-species grazing decreased soil UR (urease), SC (sucrase), and ACP (acid phosphatase) activities by decreasing soil NH₄⁺-N, increasing soil NO₃⁻-N and soil SOC (soil organic carbon), compared to CK. Grazing further affected core phyla and genera of rhizosphere bacterial communities, such as Bacteroidota, Rubrobacter, and Gaiella under different grazers and grazing practices by altering soil properties. The interaction of soil bacteria under YG was more sensitive than that under SG, and the interaction of soil bacteria under mixed-species grazing was more sensitive than that under single-species grazing. According to Functional Annotation of Prokaryotic Taxa (FAPROTAX) analysis associated with N cycling, and the relative abundance of the rhizosphere bacteria with the functions of nitrogen respiration and nitrite denitrification under MG (1:2), MG (1:4), and MG (1:6) were increased by 40.75 %, 34.74 %, 32.31 %, 40.86 %, 36.17 %, and 48.11 %, respectively, compared to CK. This study demonstrates that the mechanism by which different grazers and grazing practices affect soil bacterial communities and associated soil properties in the rhizosphere soil of the legume forage species M. ruthenica will contribute to the understanding how beneficial microbes interact efficiently with grazing-tolerant plant species under different grazing practices.

放牧是一种流行的草原土地利用活动。过度放牧和践踏牲畜会改变植被生长、土壤养分和土壤细菌群落，从而损害生态系统功能。然而，关于在草原生态系统中不同食草动物和放牧方式下与地上和地下抗牧寄主植物物种相关的特征的信息是有限的。我们检查了单独放牧牦牛 (YG)、纯绵羊 (SG) 和混合放牧对牦牛与绵羊比例为 1:2 (MG (1:2))、1:4 (MG) 的影响(1:4)) 和 1:6 (MG (1:6)) 对植物生长、土壤特性和土壤微生物群落的影响. 在每个处理中测量植物生物量和土壤特性，并通过 16 S rRNA 基因的高通量测序分析紫花苜蓿根际土壤中的土壤微生物群落。结果表明，单种放牧下，红花紫檀与 CK（无放牧）相比，混种放牧分别降低了 35.65%、29.68%、52.35% 和 55.60%。混合放牧通过减少土壤 NH₄⁺-N 和增加土壤 NO₃⁻-N 和土壤 SOC（土壤有机碳），与 CK 相比。放牧进一步影响了根际细菌群落的核心门和属，例如拟杆菌门、红杆菌属和盖氏菌属通过改变土壤特性在不同的放牧者和放牧方式下。YG下土壤细菌的相互作用比SG下更敏感，混合放牧下土壤细菌的相互作用比单一放牧下更敏感。根据 Functional Annotation of Prokaryotic Taxa (FAPROTAX) 分析与 N 循环相关，以及在 MG（1:2）、MG（1:4）和 MG 下具有氮呼吸和亚硝酸盐反硝化功能的根际细菌的相对丰度(1:6) 与 CK 相比分别增加了 40.75%、34.74%、32.31%、40.86%、36.17% 和 48.11%。这项研究表明，不同的放牧者和放牧方式影响土壤细菌群落和相关土壤特性的机制豆科牧草物种M. ruthenica将有助于了解有益微生物在不同放牧方式下如何与耐牧植物物种有效相互作用。