Remote sensing of photosynthetic light use efficiency of tropical ecosystems

Tropical ecosystems play major roles in the global carbon, water and energy cycles and, as a result, in global climate. The broad goal of this research is to monitor changes in plant physiological parameters, including status of pigments, and water use in connection with drought events in such ecosystems. Specifically, we focus on stress related changes in photosynthetic activity and monitoring of vegetation decline following major stress events by inferring light use efficiency (ε) from measurements of reflectance from the MODIS data. To address our objective, we inferred light use efficiency (ε) from measurements of reflectance from the MODIS data from 2000 to 2012. Our results showed clear seasonality of light use efficiency over tropical forests. Lower values of PRI were found during the driest months of the year (July, August and September). We also conducted an exploratory analysis to assess the potential climate variables that might drive the changes in photosynthetic activity in the Amazon. We were also able to demonstrate close links between changes in the Photochemical Reflectance Index temperature and precipitation.