This study challenges the long-held assumption that soil microorganisms are the primary drivers of soil organic carbon (SOC) dynamics. The researchers tested the hypothesis that high-quality (fast-decomposing) plant litter promotes microbial carbon use efficiency, leading to more mineral stabilization of microbial necromass and thus greater SOC accumulation. Using both experimental microcosms and field observations across six eastern US forests, they found that microbial growth, efficiency, and turnover were negatively related to mineral-associated SOC. Stimulation of microbial growth by high-quality litter actually enhanced SOC decomposition, offsetting the positive effect on SOC stabilization. The authors conclude that microbial necromass production is not the primary driver of SOC persistence in temperate forests, and other factors such as alternative SOC formation pathways, priming effects, and soil abiotic properties are crucial.

Matthew E. Craig, Kevin M. Geyer, Kaitlyn V. Beidler, Edward R. Brzostek, Serita D. Frey, A. Stuart Grandy, Chao Liang, Richard P. Phillips