Soil microbial communities drive ecosystem processes, and technological advances have led to an unprecedented understanding of these communities. Yet microbes are only one constituent of soil communities. Understanding how soil microbes will respond to changes in the trophic levels of soil food webs, particularly in combination with inputs of labile carbon resources, is vital for a complete picture of belowground dynamics. Here we manipulate the trophic levels of soil communities, creating a microbe treatment, a microbivore treatment, and two predator treatments that test between consumptive and non-consumptive effects. We then exposed these communities to glucose additions that simulate either the rhizosphere or bulk soil. We found that trophic levels, with and without glucose addition, lead to shifts in microbial community composition and function. Specifically, we observed that the presence of increasing trophic levels led to distinct bacterial communities compared to treatments containing only microbes, and the presence of the predator led to the most distinct shifts compared to the microbe treatment. Not surprisingly, soil respiration was greater in the rhizosphere compared to the bulk soil with the microbe treatment exhibiting greater and lesser respiration compared to the other treatments in the rhizosphere versus the bulk soil, respectively. However, the similarity in respiration between treatments was driven by different underlying processes where the presence of the predator leads to increased microbial biomass and microbial efficiency. In fact, trophic levels, compared to the availability of labile carbon, had a greater influence on microbial efficiency. This suggests that trophic levels of soil communities should be considered when attempting to understand the effect of soil microbial communities on ecosystem processes.

土壤微生物群落驱动着生态系统的进程，技术的进步使人们对这些群落有了前所未有的了解。然而微生物只是土壤群落的一种成分。了解土壤微生物如何响应土壤食物网的营养水平变化，特别是结合不稳定的碳资源的输入，对于全面了解地下动态至关重要。在这里，我们操纵土壤群落的营养水平，创建了一种微生物处理，一种微生物食草动物处理以及两种在捕食性和非食用性之间进行测试的捕食性处理。然后，我们将这些群落暴露于模拟根际或块状土壤的葡萄糖添加中。我们发现，无论是否添加葡萄糖，营养水平 导致微生物群落组成和功能发生变化。具体而言，我们观察到与仅含有微生物的处理相比，营养水平升高的存在导致了不同的细菌群落，与微生物处理相比，捕食者的存在导致了最明显的转变。毫不奇怪，与块状土壤相比，根际土壤呼吸更大，微生物处理与根际土壤相比，与其他处理相比，根际土壤呼吸更大或更小。但是，处理之间的呼吸相似性是由不同的潜在过程驱动的，其中捕食者的存在导致微生物生物量和微生物效率增加。实际上，与不稳定碳的可用性相比，营养水平 对微生物效率影响更大。这表明，在试图了解土壤微生物群落对生态系统过程的影响时，应考虑土壤群落的营养水平。