The response of soil microbial necromass carbon to global change: A global meta-analysis

Abstract

Soil organic carbon (SOC) is the largest carbon pool of terrestrial ecosystems and it is vulnerable to global change. As an important component of SOC, soil microbial necromass carbon (MNC) largely determines the dynamics of SOC. However, the response of MNC to global change on a global scale is not well understood. Here, we conducted a meta-analysis to assess the global response of MNC to warming, altered precipitation, nutrient addition, and elevated CO₂. Our results indicated that MNC was resistant to most global change factors. However, decreased precipitation reduced MNC by 6.79 % and fungal necromass carbon (FNC) by 8.99 %. In contrast, N addition had a favorable effect on MNC (+8.60 %), FNC (+7.61 %), and bacterial necromass carbon (BNC, +12.12 %). Additionally, initial environmental and experimental conditions affected the response of MNC to N addition. Notably, we found that MNC was more responsive in topsoil than in subsoil, which could account for the depth-dependent response of SOC. Furthermore, we found that the response of soil total nitrogen content and that of microbial biomass carbon mediated the MNC response to N addition. Overall, this study enhances our understanding of how MNC responds to global change on a global scale. In future studies, the response of MNC to global change in tropical/boreal regions, in long-term experiments, and in subsoils needs more attention.