## 4 Results
### Future Projection of GPP Changes under Different Scenarios  
(1) Projected temporal patterns of annual and seasonal GPP  
The projected GPP changes spanning 2014 to 2100 in the Yangtze River Basin are shown in Figure 12. It is evident that substantial disparities exist in the future alterations of the Yangtze River Basin under different climate model scenarios. Among them, GPP shows an increasing trend and then a decreasing trend under the SSP1-2.6 scenario, while GPP shows a continuous increasing trend under other scenarios, and the growth amplitude is SSP5-8.5 \(>\) SSP3-7.0 \(>\) SSP2-4.5. From the perspective of different seasons, the slope of GPP growth in spring is the highest, followed by autumn, and the lowest in winter. Due to the rapid growth of GPP in spring, GPP in spring will be higher than that in summer around 2050 under the SSP2-4.5, SSP3-7.0, and SSP5-8.5 scenarios. It is evident that the growth rate of GPP exhibits variations across different stages in the future, thus necessitating a division of the future into three distinct phases: S1 stage from 2014 to 2040, S2 stage from 2041 to 2070, and S3 stage from 2071 to 2100. From the slope changes of different  
Figure 11: The contribution of elevated CO\({}_{2}\) (eCO\({}_{2}\)), TEMP, PREC, and SRAD to GPP in different seasons. seasons in different stages (Figure 13), it can be seen that GPP growth is predominantly concentrated during spring and autumn across various scenarios, with spring displaying the most pronounced growth trend. And the growth trend in winter is the smallest. Under the SSP1-2.6 scenario, the growth trend of GPP in S1 stage is the most pronounced, with 1.77 gCm\({}^{-2}\)mon\({}^{-1}\)a\({}^{-1}\) in spring, 0.82 gCm\({}^{-2}\)mon\({}^{-1}\)a\({}^{-1}\) in summer, 1.06 gCm\({}^{-2}\)mon\({}^{-1}\)a\({}^{-1}\) in autumn, and 0.42 gCm\({}^{-2}\)mon\({}^{-1}\)a\({}^{-1}\) in winter; the growth trend of GPP in the S2 stage has decreased to a certain extent, but it still maintains a relatively low increase trend, with 0.40 gCm\({}^{-2}\)mon\({}^{-1}\)a\({}^{-1}\) in spring, 0.16 gCm\({}^{-2}\)mon\({}^{-1}\)a\({}^{-1}\) in summer, 0.22 gCm\({}^{-2}\)mon\({}^{-1}\)a\({}^{-1}\) in autumn, and 0.14 gCm\({}^{-2}\)mon\({}^{-1}\)a\({}^{-1}\) in winter; during the S3 stage, GPP showed a downward trend, with \(-\)0.58 gCm\({}^{-2}\)mon\({}^{-1}\)a\({}^{-1}\) in spring, \(-\)0.29 gCm\({}^{-2}\)mon\({}^{-1}\)a\({}^{-1}\) in summer, \(-\)0.36 gCm\({}^{-2}\)mon\({}^{-1}\)a\({}^{-1}\) in autumn, and \(-\)0.13 gCm\({}^{-2}\)mon\({}^{-1}\)a\({}^{-1}\) in winter. Under the SSP2-4.5 scenario, the trend of GPP changes in S1 and S2 stages is basically similar, with 1.93 and 2.00 gCm\({}^{-2}\)mon\({}^{-1}\)a\({}^{-1}\) in spring, 0.89 and 0.92 gCm\({}^{-2}\)mon\({}^{-1}\)a\({}^{-1}\) in summer, 1.37 and 1.34 gCm\({}^{-2}\)mon\({}^{-1}\)a\({}^{-1}\) in autumn, and 0.45 and 0.48 gCm\({}^{-2}\)mon\({}^{-1}\)a\({}^{-1}\) in winter, respectively; the growth trend of GPP in S3 stage has decreased to a certain extent, with 0.83 gCm\({}^{-2}\)mon\({}^{-1}\)a\({}^{-1}\) in spring, 0.43 gCm\({}^{-2}\)mon\({}^{-1}\)a\({}^{-1}\) in summer, 0.53 gCm\({}^{-2}\)mon\({}^{-1}\)a\({}^{-1}\) in autumn, and 0.23 gCm\({}^{-2}\)mon\({}^{-1}\)a\({}^{-1}\) in winter. Under the SSP3-7.0 scenario, the GPP growth trend from S1 to S3 stages continues to increase, with values of 2.39, 3.56, and 4.73 gCm\({}^{-2}\)mon\({}^{-1}\)a\({}^{-1}\) in spring, 0.97, 1.53, and 2.07 gCm\({}^{-2}\)mon\({}^{-1}\)a\({}^{-1}\) in summer, 1.47, 2.35, and 3.10 gCm\({}^{-2}\)mon\({}^{-1}\)a\({}^{-1}\) in autumn, and 0.58, 0.82, and 1.06 gCm\({}^{-2}\)mon\({}^{-1}\)a\({}^{-1}\) in winter, respectively.