## 5 Conclusions  
The focus of this study was on the characteristics of carbon dioxide fluxes during the growing season and their response to temperature in the grassland ecosystems of the Middle Tien Shan Mountains in Xinjiang. The grassland ecosystems acted as carbon sinks during the daytime from 6:00 to 18:00 and as carbon sources during the rest of the day. Due to the increase in solar altitude and solar radiation, the carbon dioxide flux of the grassland ecosystem changed most in June, July and August, with June and July showing significant carbon sinks. The soil temperature and air temperature at different depths were negatively correlated with NEE and positively correlated with GPP and Reco. The carbon sequestration capacity of the grassland ecosystems was strongest when the soil temperature was 25 \({}^{\circ}\)C.  
The GCFD data were compared and analyzed with the data from the Ulastai station. They show a high correlation and small errors compared to the measured value. This dataset is highly applicable in the Ulastai region and has consistent remote sensing spatial distribution. The GCFD dataset can clearly demonstrate the characteristic changes in carbon flux in the Tien Shan region, providing possibilities for the future application of GCFD data in other areas.  
This study only used the 2018 growing season eddy covariance data to explore the carbon flux balance. The carbon flux variation characteristics of grassland ecosystems during the non-growing season is worth further investigations. Additionally, this study only utilized site-specific data to reveal the influencing mechanisms of carbon flux in grassland ecosystems, which implies the need for further exploration of the influencing mechanisms of carbon flux in remote sensing space.  
Conceptualization, K.Z. and A.M.; methodology, K.Z. and Y.L.; software, Y.W.; validation, C.W. and M.S.; formal analysis, F.Y., C.Z. and W.H.; data curation, J.G. and A.A.; resources, A.M.; writing--original draft preparation, K.Z.; writing--review and editing, K.Z., A.M. and Y.L.; visualization, K.Z. All authors have read and agreed to the published version of the manuscript.  
This research was funded by the Special Project for the Construction of Innovation Environment in the Autonomous Region (PT2203), the Special Funds for Basic Scientific Research Business Expenses of Central-level Public Welfare Scientific Research Institutes (IDM2021005), the Scientific and Technological Innovation Team (Tien Shan Innovation Team) project (grant No. 2022 TSYCTD0007), the National Natural Science Foundation of China (grant No. 41875023), the S&T Development Fund of IDM (KJF202302), the Special Funds for Basic Scientific Research Business Expenses of Central-level Public Welfare Scientific Research Institutes (IDM2021001), and the Graduate Education Innovation Program of the Autonomous Region (XJ2023G032).  
The data used in this paper can be obtained from [PERSON]. ([EMAIL_ADDRESS]) upon request.  
The carbon flux data of the eddy covariance system were provided by the Urumqi Desert Meteorological Research Institute of the China Meteorological Administration. The GCFD dataset was provided by the National Tibetan Plateau Scientific Data Center.  
All authors declare no conflict of interest.