Microbial traits dictate soil neromass accumulation coefficient: A global synthesis

The accumulation of microbial necromass carbon has drawn mounting attention due to the slow decomposition. However, it remains unclear what determines the microbial necromass carbon accumulation via reiterated community turnover on large spatial scales. This study aimed to explore the characteristics of soil necromass carbon accumulation in terrestrial ecosystems. A dataset was compiled with 993 observations on the coefficient of microbial carbon accumulation in the equilibrium from 82 peer-reviewed papers. The linear mixed-effect models and structural equation models were used to ascertain the controlling factors of NAC on a global scale. The average NAC was higher in croplands (28.2) and forests (26.8) than that in grasslands (21.1). Although the edaphic factors seemingly affect the NAC whereby the NAC lowered in soils with high levels of pH and clay content on a global scale, the biotic factors, particularly for the living microorganism abundance and microbial biomass nitrogen content, were the pivotal drivers of NAC that accounted for approximately 42.5% of the geographic variances in NAC. More organic carbon was likely to be preserved in soil with a higher NAC regardless of ecosystem types. Novel findings on the overriding controls from the living microorganism abundance and microbial biomass nitrogen in driving NAC raise an urgent need for viable strategies in manipulating microbial characteristics for carbon sequestrations.