# Characteristics of Carbon Fluxes and Their Environmental Control in Chenhu Wetland, China
## 4 Conclusions  
The diurnal variation of CO\({}_{2}\) flux during the growing season of the Chenhu wetland ecosystem in 2022 exhibited considerable significance, characterized by substantial differences in the daily fluctuations of NEE throughout the month. The predominant trend was represented by a U-shaped curve, indicating CO\({}_{2}\) absorption during daylight hours followed by its release at night. Throughout the growing season, the wetland functioned as a carbon sink, whereas it transitioned to a carbon source during the non-growing season. The recorded range of NEE variation during the growing season spanned from \(-\)12.42 \(\pm\) 8.00 to 4.28 \(\pm\) 5.45 \(\mu\)molCO\({}_{2}\cdot\)m\({}^{-2}\cdot\)s\({}^{-1}\), with June demonstrating the longest average duration of carbon sink, lasting 11.5 h. In contrast, the duration of carbon sink was significantly shorter in January-February and December, during which the ecosystem predominantly exhibited carbon emissions throughout the day. The annual NEE, R\({}_{\rm eco}\), and GPP of the Chenhu wetland ecosystem were recorded at \(-\)21.20, 49.61, and 70.81 molCO\({}_{2}\cdot\)m\({}^{-2}\), respectively. Given the significant drought experienced in the Northern Hemisphere in 2022, it is imperative to implement more extensive monitoring efforts to obtain more precise measurements of CO\({}_{2}\) flux within the Chenhu wetland.  
During the growing season, daytime NEE was primarily influenced by PAR, consistent with the principles of the Michaelis-Menten light response model. VPD has been identified as a limiting factor affecting daytime net carbon exchange. An increase in VPD was found to  
Figure 9: Scatter plots of NEE against T\({}_{\rm a}\) of Chenhu wetland during the night in the growing season (**a**) and throughout the day in the non-growing season (**b**). The fitting results and correlation coefficients between NEE and T\({}_{\rm a}\) are also shown.  
reduce the sensitivity of daytime NEE to PAR. The optimal range for VPD was determined to be between 0.5 kPa and 1.5 kPa. In the non-growing season, the principal factors influencing net carbon exchange include RH, VPD, and T\({}_{\text{a}}\). The relationship between T\({}_{\text{a}}\) and NEE aligns with the principles established in the van't Hoff model. These findings enhance the understanding of CO\({}_{2}\) exchange dynamics within the lake-marsh wetland ecosystem in the middle reaches of the Yangtze River and contribute to the prediction of future responses of wetland ecosystems to changes in environmental factors.  
Conceptualization, Y.Z. and L.L.; methodology, W.W.; formal analysis, H.L. and P.L.; resources, P.L., L.L. and Y.Z.; writing--original draft preparation, Y.Z. and L.L.; writing--review and editing, Y.Z. and W.W.; project administration, H.L. and P.L. All authors have read and agreed to the published version of the manuscript.  
This research was funded by the Minsheng Geological Project of Hubei Geological Bureau (MSDZ202316, MSDZ202404).  
Data are available from the authors by request.  
The authors declare no conflicts of interest.