Fungal Necromass Carbon Dominates Global Soil Organic Carbon Storage

ABSTRACT Soil organic carbon (C) is derived primarily from plant and microbial necromass; however, the global distribution and contribution of different necromass inputs to soil C storage remain unclear. We conducted a global meta‐analysis encompassing 2410 observations from 249 microbial necromass studies and 786 observations from 72 plant residue studies. The results showed that the content of microbial‐derived C (10.63 ± 0.39 g C kg−1 soil) exceeded that of plant‐derived C (lignin phenol carbon (LPC), 5.63 ± 0.45 g C kg−1 soil), across the 0–100 cm soil profile, with fungal necromass carbon (FNC; 7.24 ± 0.21 g C kg−1) contributing the most to soil C—a pattern consistently observed across all depths. In addition, in the topsoil (0–20 cm), forests (9.39 ± 1.22 g C kg−1) and grasslands (9.73 ± 1.74 g C kg−1) showed significantly higher LPC contents than croplands and wetlands; therefore, cropland expansion significantly reduces microbial‐ and plant‐derived carbon stocks in topsoil. Global FNC, BNC, and LPC stocks were estimated to be 211 Pg (95% CI: 156–270 Pg), 71 Pg (95% CI: 59–88 Pg) and 168 Pg (95% CI: 151–186 Pg) in topsoil, respectively. Lower soil pH and mean annual temperature were associated with higher FNC, BNC, and LPC contents, particularly in high‐latitude regions like North America. These results demonstrate that microbial necromass, rather than plant residues, dominates soil C storage globally. These findings highlight the need for management strategies that address both land‐use change and rising temperatures to protect microbial and plant C pools.