Afforestation in arid regions is a widely promoted strategy for enhancing soil organic carbon (SOC) storage and mitigating climate change. However, how the trade-offs among Y-A-S strategies dictate the non-linear trajectory of SOC accumulation over decades in hyper-arid ecosystems remains poorly understood. Here, SOC dynamics and microbial regulatory processes were examined across a chronosequence of poplar plantations (7, 12, and 22 years) at two soil depths (0-30 cm and 30-60 cm) along the periphery of the Taklimakan Desert. SOC accumulation exhibited a non-linear trajectory: rapid increases occurred during early to mid afforestation (7-12 years), with SOC rising by 41.6-70.5% in topsoil and 23.9-52.3% in subsoil, followed by pronounced slowing and stabilization from 12 to 22 years, particularly in deeper layers. These patterns were closely associated with shifts in microbial life-history strategies. Afforestation improved soil conditions, including increased total nitrogen and reduced pH and electrical conductivity, driving a coordinated microbial reorganization characterized by enhanced growth-yield (Y) and resource-acquisition (A) strategies and a decline in stress-tolerant (S) strategies. This coupled shift in soil resources and microbial strategies fostered sustained SOC accumulation. Notably, the abundance of key Y-A-S taxa strategies peaked around 12 years, suggesting a critical ecological turning point toward stabilization of the soil and microbial community. This finding indicates that targeted nutrient management during this pivotal stage may optimize carbon sequestration in arid afforestation systems. Overall, this study underscores the importance of integrating microbial life-history strategies into managing belowground carbon dynamics in arid ecosystems.