Unlocking Mechanisms for Soil Organic Matter Accumulation: Carbon Use Efficiency and Microbial Necromass as the Keys

作者：Yang Yang, Anna Gunina, Cheng Huan, Liangxu Liu, Baorong Wang, Yanxing Dou, Yunqiang Wang, Chao Liang, Shaoshan An, Scott X. Chang · 发表于：Global Change Biology · 年份：2025 · DOI：10.1111/gcb.70033 · 被引用次数：173 · 研究领域：Soil Carbon and Nitrogen Dynamics、Bioenergy crop production and management、Peatlands and Wetlands Ecology

ABSTRACT Soil microorganisms transform plant‐derived C (carbon) into particulate organic C (POC) and mineral‐associated C (MAOC) pools. While microbial carbon use efficiency (CUE) is widely recognized in current biogeochemical models as a key predictor of soil organic carbon (SOC) storage, large‐scale empirical evidence is limited. In this study, we proposed and experimentally tested two predictors of POC and MAOC pool formation: microbial necromass (using amino sugars as a proxy) and CUE (by 18 O‐H 2 O approach). Soil sampling (0–10 and 10–20 cm depth) was conducted along a climatic transect of 900 km on the Loess Plateau, including cropland, grassland, shrubland, and forest ecosystems, to ensure the homogeneous soil parent material. We found the highest POC and MAOC accumulation occurred in zones of MAT between 5°C and 10°C or MAP between 300 and 500 mm. Microbial necromass C was more positively related to POC than MAOC ( p < 0.05), suggesting that microbial residues may improve POC pool more strongly compared to MAOC pool. Random forest and linear regression analyses showed that POC increased with fungal necromass C, whereas bacterial necromass C drove MAOC. Microbial CUE was coupled with MAOC ( p < 0.05) but decoupled with POC and SOC ( p > 0.05). The POC have faster turnover rate due to the lack of clay protection, which may lead to the rapid turnover of microbial necromass and thus their decoupling from the CUE. In this sense, the SOC accumulation is driven by ...