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.