Impacts of land use change and vegetation greening on gross primary productivity in the Yangtze River Basin from a water-carbon coupling perspective

The global terrestrial ecosystem environment is undergoing significant changes. Among them, vegetation greenness (VG) and land use/cover changes (LUCC) and their impacts are particularly prominent. This has a significant impact on the gross primary productivity (GPP) of ecosystems. In order to reveal the relationship between GPP and key coupling elements on a large spatial and temporal scale, this study simulated and validated the GPP of the Yangtze River Basin (YRB) from 1983−2020 based on improved water-carbon coupling model. In addition, we quantitatively analyzed the evolutionary characteristics of VG, LUCC and GPP over the past four decades. The effects of VG and LUCC on GPP were also evaluated. The results showed that the VG in the YRB showed a significant upward trend, with a total increase of 25.57%. The enhancement in VG, largely driven by climatic factors, was associated with an additional 1.92% increase in GPP compared to a low-greening baseline scenario. The LUCC primarily characterized by the expansion of forests and impervious surfaces and the shrinkage of farmland, shrubs and grasslands. The area of change accounted for 13.88% of the total watershed area (about 251200 km2). Simulations isolating the effect of LUCC suggested a potential 0.84% decrease in GPP. The comprehensive analysis revealed that the positive effect associated with vegetation greening outweighed the negative effect associated with LUCC in our simulations. This is consistent with the net increase in GPP (growth rate of 0.76 g C m−2 yr−1) observed in the baseline simulation that incorporated both dynamic drivers. This study deepens the knowledge of the coupling relationship between LUCC, VG and GPP from the hydrological perspective, It provides an important scientific basis for the sustainable management of the watershed.