Abstract: Microbial necromass is an important component of the stable organic carbon pool in soil. The proposal of the soil “microbial carbon pump” concept has further emphasized the significance of microbial necromass turnover in soils and its critical role in soil carbon accumulation. Therefore, the exploration of the turnover process and underlying mechanism of carbon derived from microbial necromass is helpful to understanding the formation and transformation mechanism of soil organic carbon. Here, we review the research progress on the turnover of carbon derived from bacterial and fungal necromass, and discuss the influence of the chemical characteristics and cell size of bacteria and fungi and the biological and abiotic factors of the soil on the turnover of microbial necromass derived carbon. We proposed that the internal factors such as differences in the composition of bacterial and fungal necromass and the external factors such as climatic factors may affect the turnover process of microbial necromass carbon by regulating the activity and metabolic capacity of microorganisms. Furthermore, we identify the potential research directions and challenges in the future, emphasizing that the importance of studying of the mechanism of the microbial derived carbon turnover process, integrating climate factors and practical application requirements, while correlating the growth efficiency and chemical composition of microorganisms with the impact on the turnover of microbial necromass carbon. It is crucial to pay attention to the protection function of soil minerals, further elucidate the contribution and stabilization mechanism of microbial necromass carbon to soil carbon, promoting the green and sustainable development of soil health.

Key words: soil organic carbon, microbial carbon pump, microbial necromass carbon, soil microorganism, mineral protection