Grazing is known to affect soil microbial communities, nutrient cycling, and forage quantity and quality over time. However, a paucity of information exists for the immediate changes in the soil physicochemical and microbial environment in response to different grazing strategies. Soil microbes drive nutrient cycling and are involved in plant-soil-microbe relationships, making them potentially vulnerable to plant-driven changes in the soil environment caused by grazing. To test the hypothesis that variable grazing intensities modulate immediate effects on the soil microbial community, we conducted a grazing trial of three management approaches; high-intensity, short-duration grazing (HDG), low-intensity, medium-duration grazing (LDG), and no grazing (NG). Soil and vegetation samples were collected before grazing and 24h, 1 week, and 4 weeks after HDG grazing ended. Soil labile carbon (C) and nitrogen (N) pools, vegetation biomass, and soil microbial diversity and functional traits were determined, including extracellular enzymatic assays and high-throughput sequencing of the bacterial 16S rRNA and fungal ITS2 regions. We found that labile soil C and inorganic N increased following LDG grazing while C-cycling extracellular enzymatic activities increased in response to HDG grazing but both total extracellular enzymatic activity profiles and soil abiotic profiles were mostly affected by temporal fluxes. The soil fungal community composition was strongly affected by the interaction of sampling time and grazing treatment, while the soil bacterial community composition was largely affected by sampling time with a lesser impact from grazing treatment. We identified several key fungal taxa that may influence immediate responses to grazing and modulate plant-soil-microbe interactions. There was strong evidence of temporal influences on soil biogeochemical variables and the soil microbiome, even within our narrow sampling scheme. Our results indicate that the soil ecosystem is dynamic and responsive to different grazing strategies within very short time scales, showing the need for further research to understand plant-soil-microbe interactions and how these feedback mechanisms can inform sustainable land management.

众所周知，随着时间的推移，放牧会影响土壤微生物群落、养分循环以及草料的数量和质量。然而，关于土壤物理化学和微生物环境因不同放牧策略而发生的直接变化的信息很少。土壤微生物驱动养分循环并参与植物-土壤-微生物关系，使它们可能容易受到放牧引起的植物驱动的土壤环境变化的影响。为了验证可变放牧强度调节对土壤微生物群落的直接影响的假设，我们对三种管理方法进行了放牧试验；高强度、短时间放牧 (HDG)、低强度、中等时间放牧 (LDG) 和无放牧 (NG)。土壤和植被样品在放牧前和放牧后 24 小时、1 周、HDG 放牧结束后 4 周。确定了土壤不稳定碳 (C) 和氮 (N) 库、植被生物量以及土壤微生物多样性和功能性状，包括细菌 16S rRNA 和真菌 ITS2 区域的细胞外酶促测定和高通量测序。我们发现，随着 LDG 放牧，不稳定的土壤 C 和无机 N 增加，而 C 循环细胞外酶活性随着 HDG 放牧而增加，但总细胞外酶活性概况和土壤非生物概况主要受时间通量的影响。土壤真菌群落组成受采样时间和放牧处理相互作用的强烈影响，而土壤细菌群落组成受采样时间的影响很大，而放牧处理的影响较小。我们确定了几个可能影响对放牧的即时反应和调节植物-土壤-微生物相互作用的关键真菌类群。有强有力的证据表明时间对土壤生物地球化学变量和土壤微生物组有影响，即使在我们的狭窄抽样方案中也是如此。我们的结果表明，土壤生态系统是动态的，并且在很短的时间内对不同的放牧策略做出反应，表明需要进一步研究以了解植物-土壤-微生物的相互作用以及这些反馈机制如何为可持续土地管理提供信息。