Soil organic matter (SOM) and the carbon and nutrients therein drive
fundamental submicron- to global-scale biogeochemical processes and
influence carbon-climate feedbacks. Consensus is emerging that microbial
materials are an important constituent of stable SOM, and new
conceptual and quantitative SOM models are rapidly incorporating this
view. However, direct evidence demonstrating that microbial residues
account for the chemistry, stability and abundance of SOM is still
lacking. Further, emerging models emphasize the stabilization of
microbial-derived SOM by abiotic mechanisms, while the effects of
microbial physiology on microbial residue production remain unclear.
Here we provide the first direct evidence that soil microbes produce
chemically diverse, stable SOM. We show that SOM accumulation is driven
by distinct microbial communities more so than clay mineralogy, where
microbial-derived SOM accumulation is greatest in soils with higher
fungal abundances and more efficient microbial biomass production.