Estimation of NPP based on improved CASA model and analysis of its climatic factors in the Three Gorges Reservoir Area

Vegetation net primary production (NPP) can directly reflect the production ability of vegetation in natural environments, is an important indicator of ecosystem land surface conditions. The Three Gorges Reservoir Area (TGRA) has undergone a series of ecosystem problems in recent years. To reveal the spatiotemporal characteristics and of vegetation dynamics and its driving factors in the Three Gorges Reservoir Area, NPP is estimated based on the Carnegie–Ames–Stanford (CASA) approach model. The results indicate that 1) the total NPP in the Three Gorges Reservoir Area increased at a speed of 17.64 g C m-2 yr-2 from 2001 to 2020 and the multiyear average NPP was 785 g C m-2 yr-1. In terms of spatial distribution, it is mainly characterized by higher head and tail, lower belly and higher north than south of the Yangtze River. 2) NPP was significantly positively correlated with precipitation, temperature and solar radiation, with the strongest correlation with temperature and the weakest with precipitation. 3) The precipitation showed significant increasing trends while temperature and solar radiation decreased slightly. The increase in precipitation was the main climatic factor contributing to the increase in NPP.