Soil Resources, Department of Environmental Systems Science, ETH Zurich, Zurich, Switzerland.
Centre for Microbiology and Environmental Systems Science, University of Vienna, Vienna, Austria.
Glob Chang Biol. 2024 Aug;30(8):e17465. doi: 10.1111/gcb.17465.
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.
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）上，仍未解决以下问题：（i）特定的环境属性（例如气候、地质、土壤类型）或（ii）微生物群落组成是否直接驱动关键微生物特性和功能。为了解决这一知识空白，我们使用了智利地理气候梯度上的 33 个草原表土（0-10cm）。首先，我们在有利的标准化条件下将土壤孵育了 1 周，并定量测定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、生长速率以及碳利用效率（CUE）。其次，我们对土壤的气候和物理化学特性以及细菌和真菌群落组成进行了特征描述。然后，我们应用回归分析来研究所测量的微生物特性和功能与环境设定与微生物群落组成之间的关联强度。结果表明，环境属性（主要是土壤有机质的含量）决定了 MBC 在梯度上的分布模式，而 MBC 反过来又解释了微生物呼吸和生长速率。然而，归一化后的微生物呼吸和生长速率（即比呼吸和生长）与微生物群落组成的相关性大于环境属性。值得注意的是，特定呼吸和生长都遵循不同的趋势，与微生物群落的不同部分相关，这反过来又对微生物 CUE 产生了强烈影响。我们得出结论，即使在宏观尺度上，CUE 也是微生物代谢生理上分离的方面的结果，而这部分又由微生物群落组成决定。环境设定和微生物群落组成会影响不同的微生物特性和功能，因此在考虑宏观尺度 SOC 动态时，这两个因素都需要考虑在内。
