Climatic Regulation of Microbial Carbon Metabolic Potential Across Desert Regions of China

ABSTRACT

Arid regions are an important component of the global terrestrial carbon pool, yet how soil microorganisms regulate carbon metabolism in these systems remains insufficiently understood. Here, we combined a natural climatic gradient across arid northwestern China with standardized carbon addition incubations to examine the spatial patterns and controls of soil microbial carbon metabolic potential. Basal respiration, respiration after carbon addition, microbial biomass, extracellular enzyme activities, and soil nutrients were measured to assess how hydrothermal conditions, soil carbon availability, and microbial attributes jointly regulate microbial carbon responses. Our results showed that desert soil microorganisms were strongly constrained by carbon scarcity. Carbon addition greatly stimulated microbial respiration, whereas DNA content increased only slightly, indicating that microbial responses to carbon inputs were mainly driven by rapid metabolic activation rather than short‐term biomass growth. Across the climatic gradient, microbial respiration and carbon metabolic potential were not controlled by temperature or precipitation alone. Instead, their spatial patterns were closely associated with soil organic carbon and microbial biomass, suggesting that substrate supply and microbial pool size are key constraints on microbial carbon responses in desert soils. Structural equation modeling further showed that climate‐related effects were mainly mediated by organic carbon availability, microbial biomass, and carbon‐acquiring enzyme activities. Overall, our findings indicate that microbial carbon metabolism in drylands is jointly regulated by hydrothermal background, resource limitation, microbial biomass, and enzyme activity. Incorporating these resource‐mediated microbial processes into ecosystem models may improve predictions of soil carbon dynamics in arid and semi‐arid regions.