Ecosystem‐Dependent Responses of Microbial Necromass Carbon to Warming Are Governed by the Balance Between Necromass Formation and Decomposition

Abstract

Microbial necromass carbon (MNC) is increasingly recognized as a major contributor to persistent soil organic carbon (SOC), yet its response to climate warming and the underlying regulatory mechanisms remain poorly understood. Here, we conducted a global meta‐analysis to assess how total MNC, fungal necromass carbon (FNC), and bacterial necromass carbon (BNC) respond to warming and to identify the key drivers. Overall, warming had no significant net effect on total MNC, FNC, or BNC across all observations, although publication bias‐corrected analyses revealed a significant 8.6% increase in FNC. However, warming effects varied substantially among ecosystems, increasing MNC accumulation in permafrost (+25.4%), grassland (+8.2%), and cropland (+9.9%) soils, while decreasing it in forests (−12.4%) and showing no significant effect in wetlands. Warming effects were further influenced by warming method, soil depth, climatic conditions, and initial soil properties. Meta‐regression analyses showed that warming‐induced changes in microbial biomass were the strongest predictor of MNC responses, highlighting the central role of microbial growth and turnover in regulating necromass dynamics. Moreover, shifts in nutrient availability, soil pH, and extracellular enzyme activities significantly influenced the balance between necromass production and decomposition. Positive coupling between MNC and SOC responses suggests that microbial necromass formation represents an important mechanism linking microbial processes to soil carbon persistence under warming. Overall, our findings demonstrate that warming affects MNC by altering microbial traits and nutrient availability, thereby regulating the balance between necromass production and decomposition. Ecosystem‐specific conditions further determine the magnitude and direction of these responses. These findings highlight the need to incorporate microbial necromass dynamics into predictions of soil carbon‐climate feedbacks under future warming scenarios.