NDVI-based trends change detection of surface greenness in Sichuan

In recent years, Sichuan Province has taken strong measures to protect green space. Revealing change characteristics of surface greenness will help to understand the ecological status of surface vegetation and provide a basis for ecological management. Normalized Difference Vegetation Index (NDVI) is produced by satellites to quantify surface greenness. To detect trends of surface greenness in Sichuan, FengYun-3D (FY-3D) mersi-ii monthly NDVI from January 2020 to December 2023 are utilized. Linear trend fitting and coefficient of variation analysis showed that the annual average NDVI increased from 2020 to 2023 in most areas. The slope of the annual average NDVI trend reached 0.0195 per year. Further, significant increasing trends of seasonal average NDVI appeared with rates of 0.0274, 0.0048, 0.0242 and 0.022 per year in four seasons. Annual and seasonal average NDVI increased in most plateaus and north-eastern Sichuan except summer. In north-western Sichuan, NDVI decreased all the time. In summer, most regions showed decreasing trends.