Elevational dynamics of vegetation changes in response to climate change on the Tibetan plateau

Understanding long-term vegetation dynamics is essential for assessing ecosystem responses to climate change, particularly in ecologically sensitive regions like the Tibetan Plateau. While numerous studies have analyzed vegetation changes on the Tibetan Plateau from 1982 to 2015 using remote sensing data, most have been limited by insufficient temporal coverage and low-resolution datasets, constraining the accuracy of trend detection and driver analysis. To address this gap, we utilize a high-resolution Normalized Difference Vegetation Index (NDVI) dataset, generated by merging GIMMS and SPOT data via the Extended Observation Time (EOT) algorithm, to investigate vegetation trends, breakpoints, and their climatic drivers over 34 years, with a specific focus on elevation effects. Our results indicate a predominant greening trend, with NDVI increasing in 86% of the area and browning in 14%, and an average greening rate of 0.0012 per decade. However, this trend varies with elevation: greening is most pronounced below 1000 m, followed by 1000-2000 m and 3000-4000 m, while the weakest greening occurs at 2000-3000 m. Breakpoint analysis reveals major shifts around 1998, with 70.1% of vegetation experiencing abrupt changes between 1996 and 2000, and 59.4% showing their first breakpoint in 1998. The highest NDVI breakpoint rate (27%) is observed at 2000-3000 m. Additionally, we find that temperature exerts a stronger influence on NDVI dynamics than precipitation. These findings underscore the complex interactions between vegetation, elevation, and climate, emphasizing the need for enhanced ecological monitoring and conservation efforts. Future research should incorporate additional climatic variables and improved modeling techniques to refine our understanding of vegetation responses in this high-altitude environment.