土壤微生物特性和功能在土壤有机碳(SOC)动态中起着核心作用。然而,在宏观尺度(区域到全球),是否(i)特定的环境属性(例如,气候,地质学,土壤类型)或(ii)微生物群落组成直接驱动关键微生物性状和功能。为了解决这个知识差距,我们使用了智利地气候梯度中的33个草地表层土壤(0-10厘米)。首先,我们在有利的标准化条件下培养土壤1周,并量化了广泛的土壤微生物特性和功能,如微生物生物量碳(MBC),酶动力学,微生物呼吸,增长率和碳利用效率(CUE)。第二,我们表征了土壤的气候和理化性质以及细菌和真菌群落组成。然后,我们应用回归分析来研究所测量的微生物特征和功能与环境环境相对于微生物群落组成的关联程度。我们表明,环境属性(主要是土壤有机质的数量)决定了MBC沿梯度的模式,这反过来解释了微生物的呼吸和生长速率。然而,MBC的呼吸和生长正常化(即,特定的呼吸和生长)与微生物群落组成比环境属性更相关。值得注意的是,特定的呼吸和生长都遵循不同的趋势,并且与微生物群落的不同部分有关,这反过来又对微生物CUE产生了强烈的影响。我们得出结论,即使在宏观尺度上,CUE是微生物代谢的生理解耦方面的结果,这又部分由微生物群落组成决定。环境设置和微生物群落组成影响不同的微生物性状和功能,因此,这两个因素都需要在宏观SOC动力学的背景下考虑。
Soil microbial traits and functions play a central role in soil organic carbon (SOC) dynamics. However, at the macroscale (regional to global) it is still unresolved whether (i) specific environmental attributes (e.g., climate, geology, soil types) or (ii) microbial community composition drive key microbial traits and functions directly. To address this knowledge gap, we used 33 grassland topsoils (0-10 cm) from a geoclimatic gradient in Chile. First, we incubated the soils for 1 week in favorable standardized conditions and quantified a wide range of soil microbial traits and functions such as microbial biomass carbon (MBC), enzyme kinetics, microbial respiration, growth rates as well as carbon use efficiency (CUE). Second, we characterized climatic and physicochemical properties as well as bacterial and fungal community composition of the soils. We then applied regression analysis to investigate how strongly the measured microbial traits and functions were linked with the environmental setting versus microbial community composition. We show that environmental attributes (predominantly the amount of soil organic matter) determined patterns of MBC along the gradient, which in turn explained microbial respiration and growth rates. However, respiration and growth normalized for MBC (i.e., specific respiration and growth) were more linked to microbial community composition than environmental attributes. Notably, both specific respiration and growth followed distinct trends and were related to different parts of the microbial community, which in turn resulted in strong effects on microbial CUE. We conclude that even at the macroscale, CUE is the result of physiologically decoupled aspects of microbial metabolism, which in turn is partially determined by microbial community composition. The environmental setting and microbial community composition affect different microbial traits and functions, and therefore both factors need to be considered in the context of macroscale SOC dynamics.