Variation in soil organic carbon across elevation gradient in mountainous Gilgit-Baltistan, northern Pakistan

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.