Is the seasonal forest more vulnerable to drought effects in tropical Amazonia

Abstract:

Recent studies have found that the seasonal forests in semi-arid region are more susceptible to severe drought events and the persistent effect of these climate extremes can last for 2 to 4 years. However, the Amazonian forests, where the plant available water is often abundant, seasonal forests are considered more drought-tolerant as water deficits coincide with seasonal peaks of solar radiation. But the interactions between climate and anthropogenic changes have made the scenario of these forests in the “arc of deforestation” complicated. The tight coupling between extreme droughts and fire intensity can cause widespread fire-induced tree mortality across southeastern Amazon forests. The legacy effects of droughts, as well as the frequent revisit of these extremes in the recent decade (e.g. the 2005 and 2010 Amazon droughts) have made the projection of forest recovery unclear. In this study, we use satellite proxies of canopy structure, skin temperature and water content from observations of MODIS NIR reflectance, land surface temperature and QSCAT radar backscatter to define the seasonality in the Amazonian forests. It is further calibrated using the measurements of chlorophyll fluorescence from GOSAT, terrestrial water storage from GRACE, as well as the structural metrics from GLAS waveforms. We delineate the post-drought effects of Amazon forests using seasonality-derived phenological regions. The results are expected to have a better understanding of the inter-annual variation of forest seasonality under the influence of both climate extremes and human-induced changes.