Vegetation boundary changes on the Tibetan Plateau from 2001 to 2020

Vegetation dynamics on the Tibetan Plateau are critical indicators of regional ecological conservation efforts. Quantifying the spatiotemporal patterns of vegetation boundary changes and their climatic drivers is essential for assessing structural and functional changes in alpine ecosystems.Using MODIS NDVI data (1km resolution) and meteorological data from 2001 to 2020, weconductedtrend and correlation analyses to examine the variation trends inNDVI values, vegetation boundaries, and coverage areas across different grades on the Tibetan Plateau, as well as their climatic driving factors. The results indicate the following: 1) Over the past two decades, growing season NDVI values on the Tibetan Plateau have shown a significant increasing trend (P < 0.01), with a growth rate of 0.011 per 10 years, approximately double the rate observed since 1982.2) The continuous increase in minimum temperature has reduced the constraints on temperate vegetation in alpine regions, causing vegetation boundaries on the Tibetan Plateau to shift westward and northward. During this boundary migration process, significant changes occurred in vegetation coverage areas. Low and moderate vegetation coverage areas contracted at rates of 3 424.30 and 1 197.70 km²·a⁻¹, respectively, while moderate-low, moderate-high, and high vegetation coverage areas expanded at rates of 2 048.45, 2 406.49, and 1 008.69 km²·a⁻¹, respectively. 3) Climate change has influenced both NDVI values and vegetation coverage areas on the Tibetan Plateau. The expansion of moderate-low, moderate-high, and high vegetation coverage areas was primarily driven by three factors during both growing and non-growing seasons: increased mean temperature, elevated minimum temperature, and enhanced precipitation. The expansion of moderate-low and moderate-high vegetation coverage areas encroached upon low and moderate vegetation coverage areas, resulting in the contraction of the latter.