## 6 Conclusions  
In this study, a new method for estimating GPP by coupling the LUE model and regression model is developed, and the model could perform well in GPP simulation in the Yangtze River Basin. The main conclusions are as follows: (1) GPP in the Yangtze River Basin shows a significant increase trend in the historical period. The elevated CO\({}_{2}\) dominates the change of GPP in the Yangtze River Basin. (2) The growth trend of GPP becomes more pronounced with the increase in CO\({}_{2}\) emissions from SSP1-2.6 to SSP5-8.5 scenarios. Under SSP1-2.6, the GPP shows a trend of first increasing and then decreasing, with a significant upward trend from 2014 to 2040, a slower growth rate from 2041 to 2020, and a decreasing trend from 2071 to 2100. Meanwhile, in other scenarios, there is an upward trend. Under SSP2-4.5, the growth trend is relatively obvious from 2014 to 2040 and 2041 to 2070, with a slowdown in growth from 2071 to 2100. In the other two scenarios, the growth trend of GPP is becoming larger and larger. (3) There are significant seasonal differences in the future changes of GPP in the Yangtze River Basin, with the greatest changes occurring in spring. Moreover, under the SSP2-4.5, SSP3-7.0, and SSP5-8.5 scenarios, the spring GPP may exceed the summer GPP, leading to an increased risk of future drought. The sub basins with large changes in GPP are concentrated in the Jialing River, Wujiang River, upper trunk stream, and Dongting Lake. The sub basins with small changes are the Jinsha River, Mintuo River, downstream main stream, and the Taihu Lake. The degree of change also increases with increasing CO\({}_{2}\) emissions under SSP1-2.6 to SSP5-8.5. (4) In general, the carbon sequestration capacity of the Yangtze River Basin will increase in the future, but under the SSP1-2.6 scenario, it is necessary to guard against the risk of declining carbon sequestration capacity in the future. At the same time, the carbon sequestration capacity of Poyang Lake and Dongting Lake may decline in summer, while the large increase in the productivity of upstream vegetation needs to guard against the impact on downstream water resources in the future.  
H.D.: Writing--original draft, review, and editing, investigation, visualization. J.W.: Formal analysis, investigation, methodology, writing--original draft. S.Z.: Conceptualization, methodology, writing--review and editing. J.X.: Conceptualization, writing--review and editing. All authors have read and agreed to the published version of the manuscript.  
This study was jointly supported by the Strategic Priority Research Program of the Chinese Academy of Sciences (No.XDA23040500), Youth Innovation Promotion Association, CAS (2021385), the Central Guidance on Local Science and Technology Development Fund of Chongqing City (No.2021000069) and the Chongqing Ph.D. Zhitongche Project (No. sl202100000783), the Hubei Provincial Natural Science Foundation of China (Grant Number: 2023 AFB782) and the Fundamental Research Funds for the Central Universities of South-Central Minzu University (Grant Number: CZQ23013).  
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.