Patterns and determinants of soil microbial residues from tropical to boreal forests

Soil carbon (C) stabilization has become an important topic in recent years in the context of global climate change. Increasing evidence suggests that microbial residues represent a significant fraction of persistent soil C pools. However, patterns and determinants of soil microbial residues across different biomes remain poorly understood. Here, by combining field investigations from tropical to boreal forests in eastern China with a meta-analysis across global forest biomes, we assessed how biotic and abiotic factors governed the geographic pattern of soil microbial residues indicated by amino sugars. We found that microbial residue concentrations in soils increased significantly from tropical to boreal forests in China and across the globe, which was mainly driven by temperature and soil nitrogen (N). Compared with bacterial residues, fungal residues preferentially accumulated at high latitudes. However, a significant negative relationship existed between soil C/N ratio and total residue-C/SOC in all examined forest soils, indicating a greater contribution of microbial residue-C to SOC in tropical forests than in boreal forests. These findings demonstrate that climate and soil play an important role in microbial-mediated soil C stabilization from boreal to tropical forests.