## 4 Discussion
### Environmental Drivers of Carbon Flux Variability  
The correlation coefficients and SEM analysis of CH\({}_{4}\) flux, GPP, Reco, and NEE across the PYR and HK sites during storm surge events reveal distinct site-specific responses to environmental variables, highlighting the complex interactions between carbon fluxes and climatic variables in extreme conditions (Figures 6 and 7). NEE is primarily regulated by the direct effects of GPP and Reco [34; 35]. At both sites, the response patterns of NEE to TA, PPFD, VPD, and RH were generally consistent before and after the storm surge (Figures 8 and 9). The major differences observed during the storm surge period were primarily associated with the response curves of NEE to VPD and RH. Notably, at the PYR site, NEE exhibited an approximately linear response to TA during the storm surge. Previous research also has demonstrated a nonmonotonic relationship between air temperature (Ta) and ecosystem productivity, with an optimal temperature range of 25-30 \({}^{\circ}\)C that maximizes productivity, while deviations below or above this range result in diminished performance [36; 37]. Hydrological disturbances such as flooding have been shown to extend the upper limit of this optimal TA range by approximately 3 \({}^{\circ}\)C and concurrently raise the light saturation threshold of NEE [9]. Flooding events triggered by storms or hurricanes have been shown to cause a rapid and substantial increase in CO\({}_{2}\) efflux, often elevating emissions by a factor of 2 to 10 over short timescales [38]. The strong pre-storm correlations between NEE and factors such as LE, H, TA, PPFD, VPD, and RH suggest that NEE is tightly coupled with both energy fluxes and atmospheric drivers under normal conditions (Figure 6). However, the reduction in these correlations during the storm surge period indicates a decoupling of ecosystem carbon exchange from its typical environmental controls. This disruption likely reflects the dominance of abiotic stressors--such as waterlogging, salinity intrusion, and hypoxia--introduced by the storm surge, which can be attributed to both the suppression of ecosystem respiration under anoxic conditions and the restricted gas exchange caused by physical barriers during the storm surges [39; 40]. Recent findings suggest that flooding, through its influence on salinity dynamics, not only exerts direct effects on carbon and water fluxes but also alters the ecosystem's functional sensitivity to other environmental drivers, such as air temperature [41]. Figure 8: NEE response curves to (**a**) air temperature (TA), (**b**) photosynthetic photon flux density (PPFD), (**c**) vapor pressure deficit (VPD), and (**d**) relative humidity (RH) at the HK site. The red, blue, and yellow curves indicate the fitted trends corresponding to the pre-storm surge, during-storm surge, and post-storm surge periods, respectively. Figure 9: NEE response curves to (**a**) air temperature (TA), (**b**) photosynthetic photon flux density (PPFD), (**c**) vapor pressure deficit (VPD), and (**d**) relative humidity (RH) at the PYR site. The red, blue, and yellow curves indicate the fitted trends corresponding to the pre-storm surge, during-storm surge, and post-storm surge periods, respectively. During the storm surge, the direct effect of WTD on CH4 flux decreased at both sites, with the reduction reaching statistical significance at the PYR site (Figure 7, \(p<0.01\)). This attenuation of WTD control may be attributed to saturated soil conditions, where additional increases in water level no longer exert incremental influence on anaerobic processes. Under such inundated states, methanogenic activity is increasingly governed by thermal and substrate conditions, leading to a shift in dominant controls from hydrological to climatic variables [41]. Previous studies have also reported this pattern, wherein temperature becomes a stronger predictor of CH4 flux under prolonged flooding [42, 43].