Wang B., Ao D., Liang C., Buckeridge K., Liu C., Yang Y., Li Y., Li H., Wen Z., An S.
Soil and Tillage Research, vol. 258, art. no. 107042, 2026
Microbial necromass constitutes a major and stable component of soil organic carbon (SOC) in terrestrial ecosystems. However, despite plant-derived inputs largely regulate substrate quality and soil organic matter (SOM) carbon to nitrogen (C/N) ratios and shape the composition of living microbial communities, fundamental differences in resource acquisition, death pathways, and residue chemistry between fungi and bacteria decouple living biomass from necromass accumulation. Whether fungal and bacterial necromass are subject to same SOM C/N constraints across ecosystems remains an open question. Here, we combined 1600 global SOM and microbial necromass records from global ecosystems (C/N: 3.8–58) through meta-analysis and 768 field measurement samples from Loess Plateau, spanning croplands, biocrusts, grasslands, shrublands, and forests (C/N: 6–72), representing diverse SOM qualities. We found both fungal and bacterial necromass C increased with rising SOM C/N ratios, and the consistency of this pattern from the Loess Plateau to the global scale underscores a universal role of SOM C/N control in shaping microbial necromass C. Fungal necromass C increased with increasing SOM C/N ratios, reflecting fungi advantage in processing complex organic matter under relatively N-poor conditions. Its accumulation was strongly associated with SOC, total N, and particulate organic C, reinforcing its contribution to SOC accumulation. Conversely, bacterial necromass C responded primarily to dissolved N and microbial biomass C, pointing to distinct, resource-dependent pathways of microbial necromass accumulation across microbial groups. Despite increases in microbial necromass C content and SOM C/N ratios, necromass accumulation coefficient declined, suggesting that N limitation accelerates microbial necromass recycling for biomass production and constrains net storage. Overall, by revealing the dual mechanism of necromass production driven by plant-mediated SOM complexity and necromass reutilization regulated by N availability, this work provides critical insights into the stoichiometric C/N controls shaping microbial necromass dynamics, offering a foundation for strategies to optimize nutrient management and enhance SOC sequestration in future ecosystems.
