Contrasting Response Mechanism and Ecological Stress of Net Primary Productivity in the Juncture Region of Semi-arid and Sub-humid — A case study from the Loess Plateau, China

Abstract Net Primary Productivity (NPP) is a crucial parameter for estimating the sustainability of the Earth’s carrying capacity in the terrestrial ecosystem process. With the intensification of global change, the overall function and structure of ecosystems in the Loess Plateau have changed to different extents. Based on long-time series images downloaded from the Google Earth Engine (GEE) and meteorological data, we introduced the deep regression models to process Hadoop and creatively proposed the ecological stress evaluation models from the perspective of vegetation productivity. The main research contents are as follows: (1) From 2000 to 2019, the annual NPP maintained a fluctuating increasing trend (with a value of 4.57 (g∙m 2 ·y –1 )). From the perspective of spatial distribution, the NPP gradually increased in the region from semi-arid to the sub-humid; (2) The annual temperature and annual Precipitation have the highest positive control effect on NPP change. Semi-arid regions are mainly controlled by precipitation, temperature, and other related factors, while sub-humid regions are mainly controlled by solar radiation and other factors. Finally, the main controlling factors of NPP change were different under different soil conditions; (3) Spatio-temporal pattern of NPP and ecological stress are approximately the same. The ecological stress effect is significantly different in ecological functional regions and land uses; (4) Predictive value of 2020–2030 shows that the growth of NPP slowed down compared with previous years, and the areas with extreme ecological stress in the study area continued to decrease. This study provided a new approach for the protection, restoration and governance of national land space eco-environment in the Loess Plateau. Which afford a valuable reference for further study on how to realize ecosystem restoration and protection in the juncture region of semi-arid and sub-humid.