Abstract Arbuscular mycorrhizal fungi (AMF), common symbiotic root-associated soil biota, play a key role in maintaining ecosystem function and stability. However, how AMF are affected by livestock grazing in grassland ecosystem is variable, and this uncertainty in mycorrhizal responses to grazing is mainly due to the context-dependent nature of the AMF symbiosis association. The effects of grazing on AMF are through grazing-induced changes in the environment experienced by the mycorrhizal fungi and this includes both plant and soil-related factors. Here, we introduce a conceptual framework that highlights potential drivers and mechanistic pathways through which long-term grazing impacts AMF. We focus on known drivers of AMF abundance and diversity that are expected to be influenced by grazing including plant above-ground biomass and diversity, nutrient availability (soil available nitrogen and phosphorus) and edaphic properties (soil organic carbon, soil pH, soil bulk density and soil moisture). Given that the identity and relative importance of each of these drivers may differ across different ecosystems, the application of our framework of potential environmental drivers allows us to generalize, organize and help formulate hypotheses for testing the impact of various grazing management approaches on AMF. We also argue the herbivory-AMF relationship can be moderated by climate, seasonality and topography. We reviewed the current state of knowledge of livestock grazing impacts on AMF and discussed some of the reasons behind conflicting results among empirical studies. We also provide suggestions for future research aimed at improving experimental design to unravel underlying mechanisms determining the impacts of grazing on AMF.

中文翻译：

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放牧对草地丛枝菌根真菌影响的环境驱动因素

摘要 丛枝菌根真菌（AMF）是一种常见的与根相关的共生土壤生物群，在维持生态系统功能和稳定性方面发挥着关键作用。然而，草地生态系统中牲畜放牧对 AMF 的影响是可变的，这种菌根对放牧反应的不确定性主要是由于 AMF 共生关联的环境依赖性。放牧对 AMF 的影响是通过菌根真菌经历的放牧引起的环境变化，这包括植物和土壤相关因素。在这里，我们引入了一个概念框架，突出了长期放牧影响 AMF 的潜在驱动因素和机制途径。我们关注预计会受到放牧影响的 AMF 丰度和多样性的已知驱动因素，包括植物地上生物量和多样性，养分有效性（土壤有效氮和磷）和土壤特性（土壤有机碳、土壤 pH 值、土壤容重和土壤水分）。鉴于这些驱动因素中的每一个的特性和相对重要性在不同的生态系统中可能不同，我们潜在环境驱动因素框架的应用使我们能够概括、组织和帮助制定假设，以测试各种放牧管理方法对 AMF 的影响。我们还认为，食草动物与 AMF 的关系可以通过气候、季节性和地形来调节。我们回顾了目前关于牲畜放牧对 AMF 影响的知识状态，并讨论了实证研究结果相互矛盾的一些原因。