## 4 Discussion
### How Do Trends in LST Differ Between EVI and NDVI Trends?  
In Figure 10, all three LST trendlines (\(p<0.001\)) show increasing LST, which is consistent with a gradual reduction in evaporative latent heat exchanges as areas of open water and surface soil saturation decrease, ground water tables deepen, and conditions become drier overall [101; 102]. Among the three trendlines (Figure 10), areas showing only NDVI greening (NDVI+ minus EVI+ green line) exhibited the lowest and fastest warming rate. The lower temperatures suggest that these areas of exclusive NDVI greening are associated with increased wetness, while the more rapid increase in warming suggests a drying trend, where regions of high moisture content (e.g., wetlands or areas of high water table) have undergone more rapid warming as they dry out. The NDVI response to this drying out of wetland and wetland-adjacent areas is likely a function of both the changes in surface moisture content having some influence on the NIR signal [122], as well as the ground cover vegetation response as saturation-tolerant vegetation in marsh areas is replaced with more dryland vegetation [8].  
In this northern deltaic wetland study area, positive EVI trends tend to primarily illustrate ecotonal expansions in areas of shrub and juvenile tree cover, while negative EVI trends may correctly indicate the potential for canopy losses, if not the precise locations. Meanwhile, spatial variations in NDVI trends appear sensitive to both changes in tall vegetation canopy height (Figure 5) and as has been found in other studies, temporal changes in ground surface moisture [123; 124; 125; 126].  
To synthesize these findings, Figure 11 presents a conceptual framework illustrating the complementary insights provided by VIs, LST and MNDWI. As surface moisture content decreases due to drying (e.g., reduced soil saturation), less energy is allocated to latent heat processes (evaporation), and land surface sensible heat content rises, leading to localized increases in LST. This warming is pronounced in areas undergoing transition from saturated or near-saturated conditions to dry, such as over short vegetation zones, where surface moisture content directly influences LST. Conversely, areas with consistent tree canopy cover are less affected, as the canopy masks variations in surface temperature. The conceptual model emphasizes that positive LST trends are primarily observable in open or short vegetation areas, where drying and warming processes are not obscured by dense canopy cover. NDVI and EVI are complimentary in this model, with NDVI indicating general vegetation greening (both short and tall vegetation) as well as an increased sensitivity to changing surface saturation, while EVI better represents ecosystem structural changes associated with woody ecotonal expansion, such as shrubification. Meanwhile, MNDWI tracks reductions in surface water extent, thus completing a conceptual remote sensing-based narrative of land surface and cover changes through time across northern wetland complexes, like the PAD.  
Figure 11: Conceptual framework illustrating the interconnected remote sensing-based land cover surface moisture changes represented by NDVI and EVI, LST, and MNDWI trends from time T1 to T2. As riparian surface saturation decreases, MNDWI presents negative trend slope at “a”. LST increases over short vegetation areas undergoing drying, “a” and “b”. NDVI + trends capture ground cover and canopy-level greening (“a”, “b”, and “c”) while also being sensitive to moisture changes (“a” or “b”). EVI + trends highlight the extent of woody ecotonal expansion, “c”.