## 5 Conclusions  
Quantifying the response of different carbon fluxes to environmental factors in cold temperate forest terrestrial ecosystems is extremely important to understand the ecosystem carbon fluxes under climate change. In this study, the response of GPP and NEP to environmental changes was investigated in the normal humid cold temperate climate of the Koppen-Geiger climate zone in 14 ENF ecosystems, where continuous observations were available for at least ten years. The conclusions are as follows:  
1. There were substantial differences in the effects of environmental factors on GPP and NEP at different sites, with thirteen sites displaying synchronous increases in GPP and NEP over time, of which six had significant positive correlations between GPP and NEP. One site exhibited a decoupling of GPP and NEP with a negative correlation. There were consistent trends in both GPP and NEP when temperature and precipitation had significantly opposite trends and when temperature had a significantly positive correlation with VPD across annual and seasonal scales. Conversely, a decoupling of GPP and NEP occurred when VPD\({}_{\text{MAM}}\) was significantly negatively correlated with both TA\({}_{\text{MAM}}\) and SW\({}_{\text{MAM}}\) and when TA\({}_{\text{JJA}}\) was negatively correlated with both SW\({}_{\text{JJA}}\) and VPD\({}_{\text{JJA}}\). In addition, the responses of GPP and NEP to changes in environmental factors differed significantly across seasons.
2. At forest sites with consistent trends in GPP and NEP, annual, spring, and summer temperatures had significant positive correlations with GPP and RE, while at the forest site where GPP and NEP were decoupled, environmental factors had a stronger effect on RE.
3. At the forest sites where the trends in GPP and NEP were consistent, the contribution of temperature to carbon fluxes was much greater than that of other environmental factors, and spring and autumn temperatures contributed more than 50% to GPP and NEP. Autumn temperatures contributed significantly more to NEP than to GPP and RE.
* At the forest site where GPP was decoupled from NEP, annual and summer VPD had a large contribution to GPP, accounting for 60% of the effect of all environmental factors. Additionally, spring radiation and summer precipitation dominated the contribution to NEP, promoting carbon sequestration.  
Conceptualization, L.L., M.J. and X.L.; funding acquisition, L.L. and X.L.; methodology, L.L., M.J. and X.L.; software, M.J.; data curation, M.J.; formal analysis, L.L. and M.J.; writing--original draft preparation, M.J.; writing--review and editing, L.L. and X.L. All authors have read and agreed to the published version of the manuscript.  
This research was funded by the National Key Research and Development Program of China (2022 YFF1301900) and the National Natural Science Foundation of China (42425001).  
The Koppen-Geiger climate zone is available at [[https://hanchen.org/koppen/](https://hanchen.org/koppen/)]([https://hanchen.org/koppen/](https://hanchen.org/koppen/)), accessed on 7 May 2022. The environmental factors and three carbon flux datasets are available at [[https://fluxnet.org/](https://fluxnet.org/)]([https://fluxnet.org/](https://fluxnet.org/)), accessed on 11 March 2023, [[https://www.icos-cp.eu/](https://www.icos-cp.eu/)]([https://www.icos-cp.eu/](https://www.icos-cp.eu/)), accessed on 11 March 2023, and [[https://ameriflux.lbl.gov/](https://ameriflux.lbl.gov/)]([https://ameriflux.lbl.gov/](https://ameriflux.lbl.gov/)), accessed on 13 March 2023, as described in the text.  
The authors sincerely thank the organizations and individuals who generously provided the free datasets used in this research.  
The authors declare no conflicts of interest.