Conclusions

This study reports the BBC and FBC in main biomes and presents the first global maps of BBC and FBC in 0-30 cm topsoil. The global FBC and BBC were estimated to be 12.56 (6.64 ~ 16.42) Pg C and 4.34 (0.47 ~ 10.26) Pg C, respectively, in 0-30 cm topsoil. The FBC, BBC, and F:B ratio showed clear distribution patterns on a global scale. Significant trends were observed along meteorological parameters (MAP, MAT, ST, and SM), vegetation productivity (Croot and NPP), and edaphic properties (soil texture, bulk density, soil pH, SOC, TN, and C:N ratio). The FBC and BBC were primarily determined by edaphic properties including sol texture, soil pH, bulk density, and SOC, the F:B ratio was mostly driven by climatic variables, particularly MAP and MAT. The biogeographic patterns of BBC and FBC suggest that multiple mechanisms synergistically affect soil C and nutrient cycling globally. Our study creates a benchmark for explicit use of microbial distribution and its underlying mechanisms for predicting soil C and nutrient cycling and biosphere-atmosphere feedbacks in a changing climate.