Data from comparing the relative importance of microbial residue production versus mineral preservation in MAOC dynamics over long timescales

The accrual of mineral-associated organic carbon (MAOC) is one of the key mechanisms promoting the long-term sequestration of atmospheric CO2 into soil organic carbon (SOC). Both microbial residue production and mineral preservation are vital for MAOC accumulation. However, their relative importance and interactive effects remain unclear, hampering our ability to understand how to effectively increase this important pool of persistent SOC. Here by analyzing MAOC content and composition in tandem with soil mineral and microbial attributes along a weathering gradient on a volcanic soil sequence (290 years to 2.1 million years ago), we find that MAOC content increases with increasing weathering states, accompanied by increasing microbial contribution to MAOC. In contrast to short-term studies where microbial residue production predominantly influences MAOC accumulation, weathering-enhanced mineral preservation capacity overrides microbial residue production in governing MAOC accumulation in the long term by increasing reactive minerals. Furthermore, mineral attributes have a strong interactive effect with microbial traits on MAOC accumulation and composition, likely by enhancing the accumulation efficiency of microbial residues via affecting the microbial community composition. Our findings highlight mineral weathering may effectively boost persistent SOC pools in synergy with microbial conversion.

矿物结合态有机碳（mineral-associated organic carbon, MAOC）的积累是驱动大气CO₂长期固存为土壤有机碳（soil organic carbon, SOC）的关键机制之一。微生物残体生产与矿物固持均对MAOC的积累至关重要，然而二者的相对重要性及交互效应尚不明确，这阻碍了我们理解如何有效提升这一重要持久性SOC库的能力。本研究通过分析形成年限为290年至210万年前的火山土序列沿风化梯度分布的MAOC含量与组成，并结合土壤矿物与微生物属性展开研究，结果发现MAOC含量随风化程度提升而增加，同时微生物对MAOC的贡献亦随之升高；与短期研究中微生物残体生产主导MAOC积累的结论不同，长期尺度下，风化增强的矿物固持能力通过增加活性矿物含量，在调控MAOC积累的过程中占据主导地位，其效应超越了微生物残体生产的作用。此外，矿物属性与微生物性状对MAOC的积累与组成存在显著交互效应，其潜在机制可能是通过改变微生物群落组成，提升了微生物残体的积累效率。本研究结果表明，矿物风化可与微生物转化协同作用，有效提升持久性SOC库储量。