Department of Biology, Microbial Ecology Group, Lund University, Ecology Building, 223 62 Lund, Sweden.
Centre for Environmental and Climate Research (CEC), Lund University, Ecology Building, 223 62 Lund, Sweden.
Environ Microbiol. 2017 Dec;19(12):5117-5129. doi: 10.1111/1462-2920.13990. Epub 2017 Dec 1.
Soil organic matter (SOM) constitutes the largest terrestrial C pool. An emerging, untested, view is that oxidation and depolymerization of SOM by microorganisms promote the formation of SOM-mineral associations that is critical for SOM stabilization. To test this hypothesis, we performed laboratory-scale experiments involving one ectomycorrhizal and one saprotrophic fungus that represent the two major functional groups of microbial decomposers in the boreal forest soils. Fungal decomposition enhanced the retention of SOM on goethite, partly because of oxidative modifications of organic matter (OM) by the fungi. Moreover, both fungi secreted substantial amounts (> 10% new biomass C) of aromatic metabolites that also contributed to an enhanced mineral retention of OM. Our study demonstrates that soil fungi can form mineral-stabilized SOM not only by oxidative conversion of the SOM but also by synthesizing mineral surface-reactive metabolites. Metabolites produced by fungal decomposers can play a yet overlooked role in the formation and stabilization of SOM.
土壤有机质（SOM）构成了最大的陆地碳库。一种新兴的未经检验的观点认为，微生物对 SOM 的氧化和解聚促进了 SOM-矿物结合体的形成，这对 SOM 的稳定至关重要。为了验证这一假设，我们进行了实验室规模的实验，涉及一种外生菌根真菌和一种腐生真菌，它们代表了北方森林土壤中微生物分解者的两个主要功能群。真菌分解增强了 SOM 在针铁矿上的保留，部分原因是真菌对有机物（OM）的氧化修饰。此外，两种真菌都分泌了大量（> 10%新生物量 C）的芳香代谢物，这也有助于增强 OM 的矿物保留。我们的研究表明，土壤真菌不仅可以通过 SOM 的氧化转化形成矿物稳定的 SOM，还可以通过合成矿物表面反应性代谢物来形成。真菌分解者产生的代谢物可以在 SOM 的形成和稳定中发挥尚未被忽视的作用。
