ORBITAL CHLOROPHYLL FLUORESCENCE AS A PROXY FOR PHOTOSYNTHESIS SEASONALITY AND STRESS AT THE CAATINGA

Chlorophyll a fluorescence is emitted from photosynthesizing plants with peaks at the red and far-red frequency regions, and it relates directly to photosynthesis yield and stress. Recent developments in remote sensing allow us to estimate Sun-induced fluorescence (SIF) from plants on the Earth’s surface. In this study, we have used SIF from the GOME-2 orbital instrument to characterize the usual seasonal variation of fluorescence and to study vegetation responses to anomalous droughts. Results show that GOME-2 SIF at both frequencies responded consistently to temperature and precipitation variations observed, and document a near halving of emissions in response to a drought observed there from 2012 to 2016. SIF was positively correlated to EVI, NDVI and GPP but correlations were influenced by vegetation structure and temporal aspects pertaining to each variable.