# Phenology and Seasonal Ecosystem Productivity in an Amazonian Floodplain Forest
## 4 Discussion  
The annual average pattern of ET and GPP suggests that free water is exerting an influence on the evaporative processes during the flooded period since the peak of ET observed in March, matched the flooding peak. Our analysis confirms the free water evaporation hypothesis reported by [PERSON] et al. [42] when observing higher values of ET during flood than during the dry season and lower GPP values [43]. This decoupled pattern of ET and GPP on the rainy-flooded period describes the forest dormancy probably due to anoxic conditions along the flooded months, as reported for Amazon flooded forests [34]. However, we observed the remaining high levels of GPP until March (one month after the flood started) and at the end of the flooded period (May), due to the shorter duration of the flooded period (or soil saturation) in higher terrain portions near the flux tower. Conversely, both ET and GPP decrease during the dry period as a result of soil moisture depletion, with the lowest values of ET occurring at the end of the dry season (September), and the lowest values of GPP recorded in August/September. ET and GPP recover during the early rainy season (October to January), with the highest seasonal carbon assimilation rates from 20.40 to 22.63 mmol CO\({}_{2}\) m\({}^{-2}\) s\({}^{-2}\)[43]. The same growth and carbon assimilation pattern were reported in the central Amazonian floodplain, which exhibited greater productivity during the terrestrial phase, reaching on average 20 mmol CO\({}_{2}\) m\({}^{-2}\) s\({}^{-2}\)[32] and the highest growth rates from September to November [34]. At other Amazonian sites, GPP is maximized during the early dry season as a result of increasing incident radiation and reduction of cloudiness, coupled with high levels of ET [8; 45], however, at the BAN site, GPP seasonality seems to be mainly governed by soil moisture which also regulates the canopy phenology. The phenology pattern described by EVI suggests that the new leaves flush synchronized with senescence, which can be used as a proxy of canopy changes [11]. These peaks occur when GPP is maximized, suggesting the coupling between new leaves and phenology of photosynthetic capacity. Instead of light availability, EVI at this site seems to be strongly governed by soil moisture/aeration, differing from the _terra firme_ forest [9]. However, over the flooded forests across the Amazon basin, a similar pattern is expected to occur as observed in this study, which is important for modeling carbon seasonality since approximately 14% of the basin is composed of flooded forests [28]. Nonetheless, phenology patterns obtained through satellite data in the central Amazon region should be interpreted carefully, since the flooding height is much higher than in this transitional area and assessments about the influence of flooding on vegetation indices should be considered. The EVI oscillation reflected the effect of soil moisture depletion at the end of the dry season, which reduced evapotranspiration and carbon assimilation rates, exhibiting the lowest peak in September. Thus, we highlight the potential of accurately monitoring of the floodplain forest phenology from spaceborne remote sensing, which described the carbon assimilation seasonality coupled with new leaves. Previous studies have suggested two or more months of lag between canopy greening and forest productivity at _terra firme_ forests [9; 25], which could be explained by leaf demography [11]. Although our results have shown one month of decoupling between EVI and GPP during the dry season (May-Sep), at a flooded site, this lag could be an effect of topography within the tower footprint where the early GPP response is from sub-footprint regions that are topographically higher and drien The EVI is characterizing the larger landscape response, where most forest area remains in likely anoxic conditions due to a longer period of inundation.