Abstract

Soil microbes play a pivotal role in the Earth’s carbon cycle, yet not all microbial carbon processing functions the same way. A comprehensive global meta-analysis by Sun et al. (2025) reveals that soil microorganisms utilize carbon through two fundamentally different pathways—exogenous (external carbon inputs, such as plant litter) and endogenous (internal soil carbon reserves)—and that these pathways respond differently to environmental pressures.