Soil extracellular enzyme stoichiometric ratios reveal microbial metabolism in response to resource limitation along altitudinal gradient

Microbial resource limitation and metabolic processes synergistically regulate soil carbon dynamics through multiple mechanisms. Elevation gradient shapes soil microbial resource limitation patterns, yet how microbial metabolic processes adapt to resource limitation along elevation gradient remains poorly understood. In this study, we collected soil samples at five altitudinal sites (860, 1230, 1360, 1510, and 1810 m), to analyze soil microbial resource limitation and metabolic activities. The results showed that elevation gradient significantly affected soil properties, enzyme activities, microbial biomass, and related stoichiometries (p < 0.05). With the increase in altitude, vector length (VL) decreased from 1.62 to 1.58, while vector angle (VA) increased from 25.47° to 33.02°, indicating microbial communities generally exhibited co-limitation by carbon and nitrogen, whereas the intensity of co-limitation alleviated with increasing altitude. This pattern was primarily attributed to adaptive stoichiometric adjustments of microbial extracellular enzymes involved in nutrient acquisition. Meanwhile, simulation models of microbial metabolic processes showed that both organic carbon decomposition rate (M) and microbial respiration rate (Rm) significantly increased with elevation (p < 0.05). Specifically, M rose from 11.66 % day⁻¹ to 16.18 % day⁻¹, and Rm increased from 251.46 mmol C m⁻³ day⁻¹ to 1089.71 mmol C m⁻³ day⁻¹. Random Forest results indicated soil enzyme stoichiometric ratios as major factors influencing soil microbial metabolism. Through integrating resource limitation theory with microbial metabolic simulation models, we have revealed the adaptive strategies of high-altitude microorganisms to enhance carbon turnover by alleviating resource limitation. This study provides a scientific foundation for predicting and managing forest ecosystems affected by resource limitations.