Soil organic carbon stocks (SOCS) play a critical role in mitigating atmospheric CO2 and enhancing ecosystem resilience, yet their controls in high-mountain environments remain insufficiently constrained. Using an integrated framework combining field sampling, remote sensing, machine learning, and multi-source environmental datasets, this study quantifies SOCS variability along elevation gradients across the climatically diverse region of Gilgit-Baltistan, northern Pakistan. Results reveal three dominant patterns. First, SOCS distribution is jointly regulated by elevation and climate, with humid mid-to-high altitudes functioning as net carbon sinks, whereas lower-elevation semi-humid and semi-arid regions exhibit persistent SOCS declines. This spatial-altitudinal coupling highlights the sensitivity of mountain SOCS to aridity across both vertical and horizontal landscapes. Second, climatic drivers exert contrasting effects: precipitation enhances SOCS accumulation in humid zones by promoting vegetation productivity, while rising temperatures in semi-humid and semi-arid belts accelerate carbon losses through enhanced decomposition. Third, vegetation-soil interactions amplify sequestration potential along elevation gradients. Grasslands developed on loamy soils at mid-to-high elevations store significantly higher SOCS than other land use-soil combinations, while carbon stocks decline sharply with soil depth, reflecting the vertical constraints imposed by shallow mountain soils. Together, these findings demonstrate that SOCS dynamics in fragile high-mountain ecosystems emerge from the interaction of elevation, climate variability, vegetation cover, and soil properties. Recognizing this multidimensional control is essential for designing zone-specific management strategies that enhance carbon sequestration, reduce vulnerability to climate change, and support regional contributions to global climate mitigation and sustainable development goals.