## 3 Results
### Seasonal and Interannual Dynamics of Net CO\({}_{2}\) Exchange  
Figures 7-9 show the interannual dynamics of different components of CO\({}_{2}\) fluxes in the Momoge salt marsh from 2015 to 2017 and in 2021, where the NEE, GPP, and ecosystem respiration (Reco) are daily cumulative values (g CO\({}_{2}\cdot\)m\({}^{-2}\cdot\)d\({}^{-1}\)). The GPP and Reco were estimated using the NEE.  
Figure 5: Daily dynamics of net ecosystem carbon exchange in different months (2017).  
Figure 6: Daily dynamics of net ecosystem carbon exchange in different months (2021).  
During the study period, the NEE values illustrated the variations in carbon source/sink dynamics within the study area. Each year, the variation in carbon flux in the study area approximately followed a \"V\" shape. During the non-growing seasons, the carbon flux tended to be positive, indicating CO\({}_{2}\) emissions into the atmosphere. The Momoge salt marsh  
Figure 8: Total daily cumulative values of ecosystem respiration (RE).  
Figure 7: Total daily cumulative values of net ecosystem carbon exchange (NEE).  
Figure 9: Total daily cumulative values of the ecosystem’s total gross primary productivity (GPP).  
ecosystem acted as a CO\({}_{2}\) source. During the growing season, the carbon flux was predominantly negative, indicating the absorption of CO\({}_{2}\) from the atmosphere. The Momoge salt marsh functioned as a carbon sink during this period. Throughout the observation period, the average daily cumulative NEE value was approximately \(-1.03\) g CO\({}_{2}\cdot\)m\({}^{-2}\cdot\)d\({}^{-1}\). The numbers of days with negative carbon flux were 163, 202, 193, and 186 in 2015, 2016, 2017, and 2021, respectively. The proportion of negative carbon flux days was 51% for the entire observation period. During the high vegetation growth period in summer, the carbon flux values could be relatively high, even reaching positive values. This situation was typically observed during rainy or cloudy days between June and September. Due to the low PAR under such conditions, the NEE values generally tended to be small. With weaker vegetation photosynthesis and elevated temperatures, ecosystem respiration intensified, resulting in the wetland ecosystem acting as a carbon source.  
At the interannual scale, the monthly mean daily dynamics of NEE exhibited a characteristic \"V\"-shaped curve, showing significant variations across seasons. During the non-growing season, the overall fluctuations were relatively small, whereas during the growing season, the overall fluctuations were more pronounced.  
Reco encompasses both soil and plant respiration. During the non-growing season, the Reco values were relatively low but still positive, indicating the emission of CO\({}_{2}\) into the atmosphere. As temperatures rose, Reco gradually increased, reaching its peak during the summer months. During the study period, Reco values varied within the range of 0.002 g CO\({}_{2}\cdot\)m\({}^{-2}\cdot\)d\({}^{-1}\)-20.702 g CO\({}_{2}\cdot\)m\({}^{-2}\cdot\)d\({}^{-1}\), with a mean value of 3.08 g CO\({}_{2}\cdot\)m\({}^{-2}\cdot\)d\({}^{-1}\).  
The total GPP of the ecosystem exhibited a yearly \"V\"-shaped pattern. During the non-growing season, the GPP values were relatively low. In the early growing season, with the emergence of receds and the increase in leaf area, both the GPP and Reco started to rise. As the vegetation's physiological activities intensified and photosynthesis dominated respiration, the wetland ecosystem acted as a carbon sink. During the main growing period (June to September), the GPP and Reco grew gradually.