Soil texture and organic carbon molecular composition are the main factors affectingsoil organic carbon mineralization and microbial carbon accumulation efficiency

The mineralization and accumulation of soil organic carbon (SOC) are key processes of the soil carbon cycle, and their relative changes directly influence the soil carbon balance. Exploring the main factors influencing SOC mineralization and accumulation may provide a theoretical reference for the study of the carbon cycle. This study conducted an incubation experiment with forest and grassland topsoil with different soil textures. The main factors affecting the SOC mineralization potential and microbial carbon accumulation efficiency (CAE) were determined by analyzing the soil properties, microbial biomass, microbial extracellular enzymes, lignin phenols, amino sugars, and the δ¹³C values of amino sugars. The results showed that: i) the mineralization potential of organic carbon decreased with an increase in the relative proportion of microbial-derived carbon and ii) a higher clay content led to lower SOC mineralization potential by directly suppressing microbial activity and indirectly leading to the formation of stable mineral-associated organic matter. Moreover, a higher clay content slowed down the turnover of microbes, thus inhibiting the continuous accumulation of microbial residues and reducing microbial CAE. The results of this study demonstrate the important effects of soil texture and SOC molecular composition on SOC mineralization and microbial CAE, and offer new ideas to elucidate the mechanisms influencing soil carbon dynamics, which is of great value for understanding the soil carbon budget.