## 4 Results
### Future Projection of GPP Changes under Different Scenarios
Under the SSP5-8.5 scenario, the growth trend of GPP from S1 to S3 stages continues to increase, and the growth amplitude is greater than that of the SSP3-7.0 scenario, with 2.64, 5.31, and 8.61 gCm\({}^{-2}\)mon\({}^{-1}\)a\({}^{-1}\) in spring, 1.16, 2.33, and 3.84 gCm\({}^{-2}\)mon\({}^{-1}\)a\({}^{-1}\) in summer, 1.71, 3.55, and 5.61 gCm\({}^{-2}\)mon\({}^{-1}\)a\({}^{-1}\) in autumn, and 0.62, 1.27, and 1.90 gCm\({}^{-2}\)mon\({}^{-1}\)a\({}^{-1}\) in winter, respectively. Figure 12: Projected future annual GPP (**a**) and seasonal GPP (**b**) changes in the Yangtze River Basin under different scenarios. (2)  
Projected spatial patterns of annual and seasonal GPP  
The annual average GPP in different seasons under different scenarios are as shown in Figure 14. Under SSP1-2.6 scenario, the following is shown: in spring, the area below 100 g\(\text{cm}^{-2}\text{mon}^{-1}\) accounts for about 25%, and most of them are concentrated in the Jinsha River, the area between 100-200 g\(\text{cm}^{-2}\text{mon}^{-1}\) accounts for about 45%, and the area above 200 g\(\text{cm}^{-2}\text{mon}^{-1}\) accounts for about 30%, most of which are concentrated in the Jialing River, the upper trunk stream, and the Hanjiang River. In summer, the area below 100 g\(\text{cm}^{-2}\text{mon}^{-1}\) accounts for about 10%; the area between 100 and 200 g\(\text{cm}^{-2}\text{mon}^{-1}\) accounts for about 50%, most of which are concentrated in the Poyang Lake and Dongtting Lake; the area above 200 g\(\text{cm}^{-2}\text{mon}^{-1}\) accounts for about 40%, most of which are concentrated in the Mintuo River, Jialing River, and Hanjiang River. In autumn, the area below 100 g\(\text{cm}^{-2}\text{mon}^{-1}\) accounts for about 25%, and most of them are concentrated in the Jinsha River; the area between 100-200 g\(\text{cm}^{-2}\text{mon}^{-1}\) accounts for about 55%, and the area above 200 g\(\text{cm}^{-2}\text{mon}^{-1}\) accounts for about 20%, most of which are concentrated in the southwest of the basin, the upper trunk stream, Dongting Lake, and Poyang Lake; in winter, 90% of areas have GPP below 100 g\(\text{cm}^{-2}\text{mon}^{-1}\), while areas with higher GPP are mainly distributed in the southern part. Under SSP2-4.5 scenario, the following is shown: in spring, the area below 100 g\(\text{cm}^{-2}\text{mon}^{-1}\) accounts for about 20%, and most of them are concentrated in the Jinsha River; the area between 100-200 g\(\text{cm}^{-2}\text{mon}^{-1}\) accounts for about 20%, and the area above 200 \(\text{cm}^{-2}\text{mon}^{-1}\) accounts for about 60%, which is mainly concentrated in the Jialing River, the upper trunk stream, and the Hanjiang River. In summer, the area below 100 g\(\text{cm}^{-2}\text{mon}^{-1}\) accounts for about 10%; the area between 100 and 200 g\(\text{cm}^{-2}\text{mon}^{-1}\) accounts for about 40%, mostly concentrated in the Poyang Lake and Dongting Lake, and the area above 200 g\(\text{cm}^{-2}\text{mon}^{-1}\) accounts for about 50%, mostly concentrated in the Mintuo River, Jialing River, and Han  
Figure 13: Slopes of seasonal GPP changes in the Yangtze River Basin under different scenarios. jiang River. In autumn, the area below 100 gCm\({}^{-2}\)mon\({}^{-1}\) accounts for about 20%, and most of them are concentrated in the Jinsha River; the area between 100-200 gCm\({}^{-2}\)mon\({}^{-1}\) accounts for about 30%, and the area above 200 gCm\({}^{-2}\)mon\({}^{-1}\) accounts for about 50%, and most of them are concentrated in the southwest of the basin, the upper trunk stream, Dongting Lake, and Poyang Lake; in winter, 85% of regions have GPP below 100 gCm\({}^{-2}\)mon\({}^{-1}\).