Grazing alters the plant communities, soil properties, and habitat conditions of the alpine grassland. Arbuscular mycorrhizal fungi (AMF) are involved in the nutrient cycling of grassland ecosystems and form a mutual symbiosis with their host plants. Thus, AMF are sensitive to the impact of livestock grazing. However, the effects of grazing intensity on the AMF community composition and the association between AMF and environmental factors, such as soil physicochemical properties, enzyme activity, and glomalin-related soil proteins, remain unclear. Here, the response of the soil AMF community to grazing intensity gradients (i.e., light, moderate, and heavy grazing) was studied in an alpine grassland on the Qinghai-Tibet Plateau. The dominant AMF families included Glomeraceae, Gigasporaceae, Claroideoglomeraceae, Diversisporaceae, and Ambisporaceae. Significant shifts in the AMF community composition in response to grazing intensity were found in both surface and subsurface soils. Soil C/N ratio, plant diversity, soil compactness, chitinase activity, aboveground biomass, total N, soil moisture, and NO₃⁻–N significantly correlated with changes in the AMF community composition. Heavy grazing intensity was associated with the highest AMF alpha diversity, whereas moderate grazing intensity had the lowest AMF alpha diversity in both surface and subsurface soils. Grazing intensity, dominant plants, soil C and N concentrations, and soil compactness were significantly correlated with AMF diversity. These results demonstrated a significant response of the AMF community to grazing intensity, suggesting that plants increase their reliance on AMF symbioses with higher alpha diversity in the heavily degraded alpine grasslands of the Qinghai-Tibet Plateau.

中文翻译：

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高寒草地不同放牧强度下丛枝菌根真菌群落结构

放牧改变了高山草原的植物群落、土壤特性和栖息地条件。丛枝菌根真菌（AMF）参与草地生态系统的养分循环，并与其寄主植物形成共生关系。因此，AMF 对牲畜放牧的影响很敏感。然而，放牧强度对 AMF 群落组成的影响以及 AMF 与环境因素（如土壤理化特性、酶活性和与球藻蛋白相关的土壤蛋白质）之间的关联仍不清楚。在此，研究了青藏高原高寒草地土壤 AMF 群落对放牧强度梯度（即轻、中、重放牧）的响应。主要的 AMF 科包括 Glomeraceae、Gigasporaceae、Claroideoglomeraceae、Diversisporaceae 和 Ambisporaceae。在表层和地下土壤中都发现了 AMF 群落组成随放牧强度的显着变化。土壤 C/N 比、植物多样性、土壤紧实度、几丁质酶活性、地上生物量、全氮、土壤水分和 NO₃ ^- -N 与 AMF 群落组成的变化显着相关。重度放牧强度与最高的 AMF alpha 多样性相关，而中等放牧强度在表层和地下土壤中具有最低的 AMF alpha 多样性。放牧强度、优势植物、土壤 C 和 N 浓度以及土壤紧实度与 AMF 多样性显着相关。这些结果表明 AMF 群落对放牧强度的显着响应，表明植物增加了对 AMF 共生的依赖，在青藏高原严重退化的高山草原中具有更高的 α 多样性。