Shifts in plant ecological strategies drive divergent soil organic carbon stock in alpine ecosystems

Abstract Soil organic carbon (SOC) stock in alpine ecosystems is fundamentally governed by the tension between plant‐mediated carbon supply and its subsequent transformation by soil microbes. In alpine ecosystems, climate warming is reshaping community trait composition, driving a transition from stress‐tolerant to more acquisitive and competitive strategies. While these shifts are known to have profound implications for SOC dynamics, the mechanistic pathways by which different plant strategies influence SOC remain poorly understood. In this study, we investigated how trait‐based shifts in plant community strategies influence SOC stock across a broad elevational and geographical gradient on seven mountains in China. We classified plant communities based on their functional traits into competitors (C‐strategy) and stress‐tolerators (S‐strategy) groups. We combined Bayesian mixed‐effects models and piecewise structural equation modelling (SEM) to disentangle the direct and indirect effects of plants, soil properties, microbial biomass and extracellular enzyme on SOC stock. Our results revealed significant differences in SOC stock between the two strategies, with C‐strategy communities exhibiting higher SOC levels than S‐strategy communities. In S‐strategy communities, which are characterized by traits like high leaf dry matter content, the stock of SOC was dominated by soil microbes (56.2%) over plants (40.4%). In contrast, in C‐strategy communities, with traits favouring high‐specific leaf area (SLA) and tall height, the effects of plants on SOC (56.1%) were more than two times greater than those of microbes (26.1%), a disparity likely driven by the higher temperature sensitivity of plants compared to soil microbes. These findings highlight SOC stocks are predominantly shaped by plant strategies, with distinct mechanisms linked to their functional traits and carbon input pathways in alpine ecosystems. Synthesis . By demonstrating that different plant strategies drive diametrically opposed carbon regulation pathways, our study provides a mechanistic framework linking plant functional traits to ecosystem carbon regulation in alpine ecosystems. These insights highlight how climate‐driven shifts in trait composition can restructure carbon cycling processes, offering new perspectives for trait‐based prediction of ecosystem responses under global change.