Study on spatiotemporal variations of NDVI and driving factors during the vegetation growth peak period in Sichuan-Tibet Interface, Southwest China

Introduction The vegetation at the Sichuan-Tibet Interface (STI) in China serves as a core element in maintaining the ecological barrier function of the Qinghai-Tibet Plateau, playing a crucial role in safeguarding the ecological service functions of Southwest China. Methods Based on normalized difference vegetation index (NDVI) data in August between 2001 and 2023, this study investigates the spatiotemporal variations in vegetation coverage during the peak growth period across adjacent administrative boundaries (STI-Tibet and STI-Sichuan), analyzes the time-lag effects of major climatic factors on it with Pearson’s correlation, and explores the driving factors by dream optimization algorithm-random forest model and Optimal parameter geographic detector. Results The research has found that the average NDVI value in STI regions was between 0.6 and 0.8 with a growth rate of 0.009 per decade, and 68.41% of areas showed higher mean NDVI from 2012–2023 compared to 2001–2011. STI-Sichuan displays higher proportions of both medium-low and high vegetation coverage and lower proportions of middle-high vegetation coverage compared to STI-Tibet, but STI-Sichuan showed higher proportions of non-significant increase, significant increase, and extremely significant increase compared to STI-Tibet. The NDVI shift in STI-Sichuan occurred approximately 2 years earlier than in STI-Tibet, with greater magnitude and coverage. NDVI response lags to growing-season temperature, precipitation, and solar radiation are 2 months, 1 month, and immediate, respectively. Elevation significantly impacts NDVI across both regions; however, temperature exerts greater influence in STI-Sichuan, while precipitation predominantly affects STI-Tibet. Dual-factor interactions generally enhance explanatory power, reflected by increased q -values. Discussion These findings provide valuable insights for transboundary vegetation management and conservation. Further research could encompass a broader range of ecological elements, and formulate targeted ecological restoration strategies.