Mediterranean forests own distinct characteristics resulting from climate, soil, and vegetation that affect soil microbial communities' assembly and their associated functions. We initiated a multi-scalar analysis of environmental drivers of soil functioning to (1) identify pertinent factorial scales and (2) determine the relative importance of soil, vegetation, and geoclimate influences in shaping soil microbial functions across the French Mediterranean forests. Soil samples (0-15 cm) were collected from 60 forest sites and soil physicochemical and microbiological properties were assessed across different factorial scales i.e., bioclimates, slope exposures, and forest stands. Patterns in microbial catabolic potential (i.e., extracellular enzymes and microbial respiration) and carbon (C) source utilization (i.e., catabolic-level physiological profiling) were partitioned between vegetation cover, soil characteristics, and geoclimate components. Our results reveal that the catabolic potential of soil microbes was strongly influenced by the forest stands and mainly relied on ammonium and nitrate contents. In contrast, variation in C source utilization was mainly explained by vegetation cover. Soil metabolic capacities of microorganisms and resulting C dynamics were largely constrained by climate parameters, which suggests potentially important consequences for soil C storage. Our study revealed diverse structuration patterns between the catabolic potential and the carbon source utilization of soil microbial communities, and gives insights into the underlying mechanisms of soil microbial functioning in Mediterranean forests.

中文翻译：

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地中海森林土壤中微生物功能的环境驱动因素。

由于气候，土壤和植被影响土壤微生物群落的组装及其相关功能，地中海森林具有鲜明的特征。我们对土壤功能的环境驱动因素进行了多尺度分析，以（1）确定相关的因子尺度，（2）确定土壤，植被和地球气候影响对整个法国地中海森林土壤微生物功能形成的相对重要性。从60个森林地点收集了土壤样品（0-15厘米），并评估了不同因子尺度上的土壤理化和微生物特性，例如生物气候，斜坡暴露和林分。微生物分解代谢潜能（即细胞外酶和微生物呼吸）和碳（C）源利用（即，分解代谢水平的生理分布）在植被覆盖率，土壤特征和地球气候成分之间进行划分。我们的结果表明，土壤微生物的分解代谢潜能受林分的强烈影响，并且主要依赖于铵和硝酸盐含量。相反，碳源利用的变化主要由植被覆盖率解释。土壤微生物的新陈代谢能力和由此产生的碳动力学很大程度上受到气候参数的限制，这暗示着土壤碳储存的潜在重要后果。我们的研究揭示了分解代谢潜能与土壤微生物群落碳源利用之间的多种结构模式，并深入了解了地中海森林土壤微生物功能的潜在机制。