Department of Biology, Utah State University, Logan, UT, 84322, USA.
Department of Forest Resources, University of Minnesota, Saint Paul, MN, 55108, USA.
Nat Commun. 2023 Aug 16;14(1):4962. doi: 10.1038/s41467-023-40768-y.
Modern conceptual models of soil organic carbon (SOC) cycling focus heavily on the microbe-mineral interactions that regulate C stabilization. However, the formation of 'stable' (i.e. slowly cycling) soil organic matter, which consists mainly of microbial residues associated with mineral surfaces, is inextricably linked to C loss through microbial respiration. Therefore, what is the net impact of microbial metabolism on the total quantity of C held in the soil? To address this question, we constructed artificial root-soil systems to identify controls on C cycling across the plant-microbe-mineral continuum, simultaneously quantifying the formation of mineral-associated C and SOC losses to respiration. Here we show that root exudates and minerals interacted to regulate these processes: while roots stimulated respiratory C losses and depleted mineral-associated C pools in low-activity clays, root exudates triggered formation of stable C in high-activity clays. Moreover, we observed a positive correlation between the formation of mineral-associated C and respiration. This suggests that the growth of slow-cycling C pools comes at the expense of C loss from the system.
现代土壤有机碳（SOC）循环概念模型主要侧重于调节 C 稳定的微生物-矿物相互作用。然而，由与矿物表面相关联的微生物残体组成的“稳定的”（即缓慢循环的）土壤有机质的形成与通过微生物呼吸的 C 损失密切相关。因此，微生物代谢对土壤中总碳含量的净影响是什么？为了解决这个问题，我们构建了人工根-土系统，以确定植物-微生物-矿物连续体上的 C 循环控制因素，同时定量测定与矿物相关的 C 的形成和 SOC 损失到呼吸作用。在这里，我们表明根分泌物和矿物质相互作用来调节这些过程：虽然根刺激呼吸作用导致 C 损失，并使低活性粘土层中与矿物相关的 C 库枯竭，但根分泌物在高活性粘土层中触发了稳定的 C 的形成。此外，我们观察到与矿物相关的 C 的形成与呼吸作用之间存在正相关关系。这表明，缓慢循环 C 库的生长是以系统中 C 损失为代价的。
