Understanding the formation and stabilization of soil organic carbon (SOC) is essential for predicting SOC dynamics. Traditionally, it was believed that SOC accumulates primarily through the selective retention of recalcitrant plant lignin components. However, an emerging hypothesis suggests that microbial necromass adsorbed onto mineral-associated soil fractions play a more significant role in promoting SOC formation. In this study, we tested the above hypothesis by investigating SOC content, particulate fraction (LF + POC) vs. mineral-associated fraction (MAOC), along with microbial necromass (amino sugars as biomarker) and plant lignin component (lignin phenols as biomarker) in the topsoil (0–20 cm) and subsoil (20–40 cm) across three successional stages: early coniferous forest, middle mixed forest and climax broadleaved forest in southern China. Results showed that SOC content increased with forest succession, accompanied by increasing contributions of MAOC in both soil layers. Interestingly, the contribution of microbial necromass to SOC increased throughout the succession only in the subsoil, whereas in the topsoil, it increased from the early to the middle stage, then slightly decreased at the climax stage. Additionally, the contributions of lignin phenols or LF + POC to SOC decreased in both soil layers with forest succession. A partial least squares path model further revealed that MAOC played a dominate role in governing SOC accumulation, driven by active mineral content combined with plant-derived dissolved organic matter in the topsoil and microbial necromass in the subsoil. Collectively, our findings suggest that plants and microorganisms contribute to SOC formation through interactions with minerals, unveiling an intricate interactive mechanism of plant–microbe-mineral continuum in SOC stabilization.

中文翻译：

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植物和微生物都通过矿物相互作用促进土壤有机质的形成：来自亚热带森林演替的证据


了解土壤有机碳 （SOC） 的形成和稳定对于预测土壤有机碳动态至关重要。传统上，人们认为 SOC 主要通过选择性保留顽固的植物木质素成分来积累。然而，一个新出现的假设表明，吸附在矿物相关土壤组分上的微生物坏死团在促进 SOC 形成方面起着更重要的作用。本研究通过研究华南早针叶林、中期混交林和顶端阔叶林三个演替阶段表土 （0–20 cm） 和底土 （20–40 cm） 的 SOC 含量、颗粒分数 （LF + POC） 与矿物相关分数 （MAOC） 以及微生物坏死质量（氨基糖作为生物标志物）和植物木质素成分（木质素酚作为生物标志物）来检验上述假设。结果表明，土壤有机碳含量随着森林演替而增加，同时 MAOC 在两个土层中的贡献也随之增加。有趣的是，微生物坏死量对 SOC 的贡献仅在底土中在整个演替过程中增加，而在表土中，微生物坏死量对 SOC 的贡献从早期到中期增加，然后在顶端阶段略有下降。此外，随着森林演替，木质素酚或 LF + POC 对 SOC 的贡献在两个土层中均呈下降趋势。偏最小二乘路径模型进一步揭示了 MAOC 在控制 SOC 积累方面起主导作用，其驱动力是活性矿物质含量与表土中植物来源的可溶有机物和底土中的微生物坏死量相结合。 总的来说，我们的研究结果表明，植物和微生物通过与矿物的相互作用促进了 SOC 的形成，揭示了 SOC 稳定中植物-微生物-矿物连续体的复杂交互机制。