## 3 Results
### Temporal Trends of Carbon Fluxes  
Under flooded conditions, the wetland ecosystem frequently oscillated between acting as a net carbon sink and a net carbon source, with daily NEE values ranging from \(-\)7.57 to 22.49 g C m\({}^{-2}\) d\({}^{-1}\) (mean = 0.40 g C m\({}^{-2}\) d\({}^{-1}\)) (Figure 3a). In contrast, gross primary production (GPP) exhibited a strong and recurring seasonal pattern (Figure 3b), with peak values typically observed during the warm growing months from May to August. The average daily GPP under flooded conditions was 4.06 g C m\({}^{-2}\) d\({}^{-1}\), with observed values ranging from 0.01 to 27.45 g C m\({}^{-2}\) d\({}^{-1}\). Ecosystem respiration (RE) followed a similarly pronounced seasonal cycle (Figure 3c), with higher rates during summer and early autumn. The average daily RE was 4.51 g C m\({}^{-2}\) d\({}^{-1}\), ranging from 0.01 to 29.78 g C m\({}^{-2}\) d\({}^{-1}\). Notably, flooded periods were associated with significantly lower RE.  
During non-flooded conditions, the system also displayed substantial carbon flux dynamics. The daily average NEE was 0.44 g C m\({}^{-2}\) d\({}^{-1}\), ranging from \(-\)9.19 to 21.31 g C m\({}^{-2}\) d\({}^{-1}\). The GPP during non-flooded periods was higher, averaging 6.54 g C m\({}^{-2}\) d\({}^{-1}\) and ranging from 0.01 to 31.44 g C m\({}^{-2}\) d\({}^{-1}\). Similarly, RE also increased under drier conditions, with an average daily value of 6.95 g C m\({}^{-2}\) d\({}^{-1}\) and a range of 0.32 to 32.03 g C m\({}^{-2}\) d\({}^{-1}\).  
Comparing flooded and non-flooded fluxes revealed that NEE values exhibited a higher variance during the flooded (\(-\)7.57 g C m\({}^{-2}\) d\({}^{-1}\) to 22.49 g C m\({}^{-2}\) d\({}^{-1}\)) than in non-flooded (\(-\)9.19 g C m\({}^{-2}\) d\({}^{-1}\) to 21.31 g C m\({}^{-2}\) d\({}^{-1}\)) periods (\(p\) < 0.01). GPP and RE both showed statistically significant increases under non-flooded conditions (\(p\) < 0.01). The daily average GPP (6.54 g C m\({}^{-2}\) d\({}^{-1}\)) during the non-flooded period was higher compared to the flooded period (4.06 g C m\({}^{-2}\) d\({}^{-1}\)). Similarly, a higher RE was observed during the flooded (6.95 g C m\({}^{-2}\) d\({}^{-1}\)) compared to the non-flooded period (4.51 g C m\({}^{-2}\) d\({}^{-1}\)).  
Non-flooded periods became increasingly rare after 2016. Prior to this shift, GPP and RE under flooded and non-flooded conditions were largely comparable, showing overlapping seasonal peaks and similar magnitudes. However, from 2015 onward, a clear divergence emerged: both GPP and RE became consistently higher during non-flooded periods, with RE in particular showing pronounced increases in both peak intensity and duration. This pattern suggests a potential regime shift in the wetland's carbon dynamics, likely driven by prolonged inundation and altered ecosystem processes.  
The sustained elevation of RE under non-flooded conditions--likely driven by enhanced microbial decomposition and root respiration due to increased oxygen availability--began to outpace GPP more frequently. As a result, NEE variability increased, and the wetland system increasingly functioned as a persistent net carbon source. This shift underscores the sensitivity of carbon cycling in wetland ecosystems to hydrological fluctuations and emphasizes the critical need for long-term monitoring of water regime dynamics, particularly in the face of climate variability and land-use changes.