Spatiotemporal characteristic of NDVI based on multisource remote sensing data in the Three Gorges reservoir area

Based on Advanced Very High Resolution Radiometer (AVHRR) and Moderate Resolution Imaging Spectroradiometer (MODIS) satellite sensor products, the normalized difference vegetation index (NDVI) time series from 1981 to 2020 was calculated. Sen's slope and gravity center methods were applied to assess the regional vegetation dynamic changes in terms of different land use types in the Three Gorges Reservoir Area (TGRA). The results indicate that 1) The multiyear average NDVI in the TGRA was between 0.31 and 0.97, and the average across the whole area was 0.79 with no significant change throughout the study period. 2) There were significant differences in the NDVI among the various Land use types, which generally manifested the order of forestland > grassland > farmland > unutilized land > construction land > water. 3) The spatial difference in NDVI was significant. The NDVI in the eastern part of the reservoir area was higher than that in the western part, which reveals a decreasing trend from the east to the west. 4) The center of gravity trajectory of the NDVI significantly fluctuated, generally showing leap characteristics along the east-west direction, and finally moved toward the central region.