Climate-driven land cover change and altitudinal shifts in the Aksu region of the Tianshan mountains from 1985 to 2020.

The Tianshan Mountains serve as a critical freshwater reservoir in Central Asia's arid region, playing a key role in regional ecological and economic development. To assess the response of the Tianshan Mountains to climate change, this study analyzes the spatiotemporal dynamics and altitudinal differentiation of land cover using land use transition matrices and annual change rate analysis to assess vegetation shifts under climate variability in the Aksu section of the Tianshan Mountains based on 30-m resolution land cover datasets from 1985, 2005, and 2020 integrated with climate data trends. By focusing on a 35-year period, this research captures significant climate variability and its influence on vegetation and land cover transitions. Notable changes were recorded, with forest areas expanding by 320.5 km due to increased temperatures and precipitation, grasslands decreasing by 1110.7 km, and snow/ice increasing by 242.8 km over the study period. Grasslands decreased, with much of this area transitioning to forests and snow/ice. These findings underscore the dual climatic influences of "warming" and "wetting", and the upward shifts in land cover boundaries. These findings distinguish the warming effect that promoted forest expansion from the wetting effect that enhanced snow/ice coverage, underscoring the climatic dual role in shaping high-altitude ecosystems. Innovative applications of land use transition matrices and altitudinal zonation analysis provide a quantitative foundation for understanding climate-induced vegetation shifts. Altitudinal zonation in the Aksu region above 2300 m exhibited a distinct pattern, transitioning from grassland at lower elevations to forest-grassland mosaics, bare land, and finally snow/ice at the highest elevations. These changes highlight the dominant role of climate variability in driving land cover changes over the study period. Furthermore, these findings underscore the ecological implications of grassland loss and forest encroachment. These findings offer critical insights for ecological conservation and sustainable resource management in arid mountain ecosystems.