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Unlocking Mechanisms for Soil Organic Matter Accumulation: Carbon Use Efficiency and Microbial Necromass as the Keys
Global Change Biology ( IF 10.8 ) Pub Date : 2025-01-18 , DOI: 10.1111/gcb.70033
Yang Yang, Anna Gunina, Huan Cheng, Liangxu Liu, Baorong Wang, Yanxing Dou, Yunqiang Wang, Chao Liang, Shaoshan An, Scott X. Chang

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 18O‐H2O 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 microbial necromass, whereas CUE explains MAOC dynamics. Our findings highlight the insufficiency of relying solely on microbial carbon use efficiency (CUE) to predict bulk SOC storage. Instead, we propose that CUE and microbial necromass should be used together to explain SOC dynamics, each influencing distinct C pools.

中文翻译:


土壤有机质积累的解锁机制:碳利用效率和微生物坏死量是关键



土壤微生物将植物来源的 C(碳)转化为颗粒有机 C (POC) 和矿物相关 C (MAOC) 库。虽然微生物碳利用效率 (CUE) 在当前的生物地球化学模型中被广泛认为是土壤有机碳 (SOC) 储存的关键预测指标,但大规模的经验证据有限。在这项研究中,我们提出并实验测试了 POC 和 MAOC 池形成的两个预测因子:微生物坏死量(使用氨基糖作为代理)和 CUE(通过 18O-H2O 方法)。在黄土高原上,包括农田、草地、灌木丛和森林生态系统,沿 900 km 的气候样带进行了土壤采样(0-10 和 10-20 cm 深度),以确保土壤母质的均匀性。我们发现最高的 POC 和 MAOC 积累发生在 5°C 和 10°C 之间的 MAT 或 MAP 在 300 和 500 mm 之间的区域。微生物坏死量 C 与 POC 的相关性比 MAOC 更正 (p < 0.05),表明与 MAOC 池相比,微生物残留可能更强烈地改善 POC 池。随机森林和线性回归分析表明,POC 随着真菌坏死量 C 的增加而增加,而细菌坏死量 C 驱动 MAOC。微生物 CUE 与 MAOC 偶联 (p < 0.05),但与 POC 和 SOC 解偶联 (p > 0.05)。由于缺乏粘土保护,POC 具有更快的周转率,这可能导致微生物坏死体的快速周转,从而使它们与 CUE 脱钩。从这个意义上说,SOC 积累是由微生物坏死量驱动的,而 CUE 解释了 MAOC 动力学。我们的研究结果强调了仅依靠微生物碳利用效率 (CUE) 来预测大量 SOC 储存的不足。 相反,我们建议 CUE 和微生物坏死量应该一起使用来解释 SOC 动力学,每个都影响不同的 C 池。
更新日期:2025-01-18
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