2024 Abstracts

Diurnal Changes in Canopy Spectral Response to Drought Stress in an Amazon Forest


Anna Weber1,2* (anna_rene@berkeley.edu), Daisy Celestina Souza3, Adriano José Nogueira Lima3, Gilberto Pastorello2, Jeffrey Chambers1,2


1University of California–Berkeley, CA; 2Lawrence Berkeley National Laboratory, Berkeley, CA; 3National Institute of Amazonian Research, Manaus, Amazonas, Brazil



Near-infrared (NIR) reflectance, particularly with Landsat imagery data, has been used in the central Amazon as a gauge for forest regrowth. As the frequency of severe droughts in the Amazon is expected to increase, coupled with droughts being found as a factor of increasing tree mortality, it is important to find indicators of drought impacts on tropical rainforests that can be applied at broader scales. Combining remote sensing tools with field data, the team is looking for links between NIR reflectance in these forests during times of extreme drought. In October 2023, researchers collected diurnal, multispectral imagery over the course of 2 weeks in a central Amazon Forest. This occurred during a period of extreme El Niño-Southern Oscillation–related drought. The team collected this data at multiple points throughout the day to evaluate diel patterns. Targeting individual trees attached with sap flow sensors, researchers also delineated the crowns of over 70 rainforest canopy trees, spanning a diverse wood density gradient. Combining remote sensing tools with individual-specific sap flow data, the project is looking to elucidate spectral patterns based on functional group responses as NIR reflectance while drought stress increases. The team will then evaluate if these crown patterns can be scaled up to be applied at a broader ecosystem level.