Climate Change Accelerates Microbial Biomass Accumulation in Soils

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Abstract Soil microbial biomass (SMB) and stoichiometric ratios of carbon and nutrients in microorganisms are crucial to predict biogeochemical and nutrient cycling in terrestrial ecosystems, particularly under global change. Using SMB data from 1,288 studies in China, we mapped the distribution of microbial biomass carbon (MBC), nitrogen (MBN), and phosphorus (MBP) and their stoichiometric ratios using the random forest model. The stocks of MBC, MBN, and MBP in the topsoil (0–30 cm) were (mean with 25% and 75% quantiles), , and Tg, respectively; the corresponding stocks in the subsoil (30–100 cm) were Tg C, Tg N, and Tg P, respectively. The mean MBC/MBN, MBC/MBP, and MBN/MBP ratios in the topsoil were estimated to be 10, 29, and 3.9, respectively, and the corresponding ratios in the subsoil were 8.6, 19, and 2.5, respectively. Soil physico‐chemical properties (pH and moisture) are the main direct drivers of SMB and their stoichiometric ratios, while climate (temperature) indirectly affects SMB. Climate indirectly affects SMB by altering soil moisture and substrate availability, the physico‐chemical properties directly shape SMB content through habitat and resource constraints. The Coupled Model Intercomparison Project Phase 6 demonstrated that SMB stocks will increase until 2,100. Under the Shared Socioeconomic Pathway 5–8.5, SMB stocks increased, especially in the topsoil. Our study clarified SMB stocks and microbial stoichiometric ratios for soils up to 1.0 m depth and revealed the main drivers. We assessed SMB density and microbial stoichiometric ratios, compiled databases across climatic regions, and provided recommendations for regional C, N, and P management.

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