Impacts of anthropogenic nitrogen input and land use change on gross primary productivity in the Dongting Lake basin of China

Abstract Anthropogenic activities enhance atmospheric reactive nitrogen emission and deposition, leading to changes in gross primary productivity (GPP) by affecting vegetation species composition, growth conditions and soil properties. This study investigated the impacts of anthropogenic nitrogen input (ANI), land use and land cover changes (LULCC), and climate change on GPP using the Community Land Model 5.0 in the Dongting Lake Basin (DLB) from 1990 to 2020. The results indicated an overall upward trend in GPP, with annual values ranging from 1.3 to 1.6 kg·C·m –2 ·yr –1 , with higher levels in mountainous area. The promotional effect of ANI on GPP was significant; however, after ANI began to decline in 2010, GPP did not decrease correspondingly due to the buffering effect of mineral nitrogen in the soil. Overall, ANI had a positive influence on GPP in the DLB, whereas LULCC effects were mostly negative. The effects of LULCC on GPP varied across basins; cropland expansion generally inhibited GPP, while shrub expansion enhanced it. Multiple regression analysis identified shortwave radiation (53.5%) and precipitation (38%) as the primary climatic drivers of GPP variability. This study provided valuable insights for formulating policies related to balancing ecological sustainability and economic development.