Iron (Fe) oxides regulate soil organic carbon (C) content via balancing C processes of stabilization and mineralization. However, abiotic and biotic mechanisms are involved in stabilization (e.g., by adsorption and/or co-precipitation) and decomposition (e.g., by shifting the microbial community) of paddy soil rich in iron oxides remains poorly understood. We examined the mineralization and stabilization of maize-straw-derived C (δ¹³C = 5000‰), soil priming effects (PE), and soil microbial community structure in four paddy soils, along with Fe oxide concentrations gradient ranging from 13.7 to 55.8 g kg⁻¹ soil (Fe-13, Fe-25, Fe-42, and Fe-55). The paddy soil with the highest Fe content (Fe-55) stabilized 20.5 mg ¹³C kg⁻¹ soil of the maize-straw-derived C, being significantly greater (P < 0.05) than Fe-13 (5 mg ¹³C kg⁻¹ soil). The high C:Fe molar ratio of Fe-55 suggests the main pathway of stabilizing the maize-straw-derived C via co-precipitation as Fe-OM. Larger stabilization in Fe-55 led to less CO₂ emission from maize and SOM, e.g., Fe-55 had 12–16% lower straw mineralization and 8–11% lower PE than Fe-13 during the first 7 days of incubation. Random forest analysis further revealed that Proteobacteria and Actinobacteria (the keystone species, i.e., Gaiella) gave the largest contribution to maize-straw mineralization and PE, while microbial diversity and some microorganisms featured with filamentous hyphae contributed to C stabilization. This study confirmed that the concentration of Fe oxide in paddy soils plays a central role in C sequestration via biotic and abiotic processes, including i) modulation of microbial community diversity and composition, especially the abundance of fungi and Actinobacteria, and ii) physicochemical stabilization of maize-straw-derived C through the formation of Fe-OM complexes via co-precipitation.

铁 (Fe) 氧化物通过平衡碳稳定和矿化过程来调节土壤有机碳 (C) 含量。然而，对富含氧化铁的水稻土的稳定（例如，通过吸附和/或共沉淀）和分解（例如，通过改变微生物群落）所涉及的非生物和生物机制仍然知之甚少。我们研究了四种稻田中玉米秸秆来源的 C (δ ¹³ C = 5000‰)、土壤启动效应 (PE) 和土壤微生物群落结构的矿化和稳定性，以及从 13.7 到 55.8 的 Fe 氧化物浓度梯度g kg ^-1土壤（Fe-13、Fe-25、Fe-42 和 Fe-55）。Fe含量最高的水稻土（Fe-55）稳定了20.5 mg ¹³ C kg ^-1玉米秸秆衍生的 C 的土壤，显着大于 ( P  < 0.05) Fe-13 (5 mg ¹³ C kg ^-1土壤)。Fe-55 的高 C:Fe 摩尔比表明通过共沉淀作为 Fe-OM 来稳定玉米秸秆来源的 C 的主要途径。Fe-55 中更大的稳定性导致玉米和 SOM 的CO ₂排放量减少，例如，在孵化的前 7 天，Fe-55 的秸秆矿化和 PE 比 Fe-13 低 12-16% 和 8-11%。随机森林分析进一步揭示了变形菌和放线菌（关键物种，即盖氏菌属）) 对玉米秸秆矿化和 PE 的贡献最大，而微生物多样性和一些以丝状菌丝为特征的微生物对 C 稳定做出了贡献。该研究证实，水稻土中氧化铁的浓度在通过生物和非生物过程固碳中起着核心作用，包括 i) 调节微生物群落多样性和组成，尤其是真菌和放线菌的丰度，以及 ii) 的物理化学稳定性玉米秸秆衍生的 C 通过共沉淀形成 Fe-OM 复合物。