B008-02
Downscaling of far-red sun-induced chlorophyll fluorescence from canopy to leaf scale using data from the airborne imaging spectrometer HyPlant

Monday, 7 December 2020: 07:04
Virtual
Bastian Siegmann1, Sergio Cogliati2, Alexander Damm3, David Herrera1, Laura Verena Junker-Frohn1, Thorsten Kraska4, Onno Muller1, Patrick Rademske1, Dirk Schuettemeyer5, Juan Quiros1 and Uwe Rascher1, (1)Forschungszentrum Jülich, IBG-2: Plant Sciences, Jülich, Germany, (2)University of Milano - Bicocca, Department of Earth and Environmental Sciences, Milan, Italy, (3)University of Zurich, Department of Geography, Zurich, Switzerland, (4)University of Bonn, Faculty of Agriculture, Bonn, Germany, (5)ESA-ESTEC, European Space Research and Technology Centre, Noordwijk, Netherlands
Recorded Presentation
Abstract:
The FLuorescence EXplorer (FLEX) of the European Space Agency (ESA) will be the first hyperspectral mission especially designed to monitor the photosynthetic activity of the terrestrial vegetation layer by using a completely novel technique measuring the sun-induced chlorophyll fluorescence (SIF) signal that originates from the core of the photosynthetic machinery. In preparation of the upcoming FLEX satellite mission, large campaigns, namely FLEXSense I and II, were conducted in 2018 and 2019 including representative study sites at several locations in middle and southern Europe.

As an example of the numerous FLEXSense campaign activities, the results of a field study are presented, which took place at the agricultural research station Campus Klein-Altendorf in Germany in the end of June 2018. In a period of four consecutive days from 26 to 29 June, the test site was recorded six times by the airborne imaging spectrometer HyPlant, with each three overflights before and three after local solar noon. The two sensor modules of HyPlant measure contiguous spectral information from 370 to 2500 nm, as well as highly-resolved spectral data in the O2-A and B absorption features which allows retrieving SIF at 760 and 687 nm.

The availability of such a unique dataset makes it possible for the first time to investigate the spatial differences in SIF of different crops (sugar beet, winter wheat and fruit trees) in the course of the day. Furthermore, the recently developed fluorescence correction vegetation index (FCVI) (Yang et al. 2020, RSE 240:111676) was applied to the HyPlant image data to correct for photosynthetic active radiation (PAR) absorption and scattering effects, which makes it possible to determine the SIF escape fraction (fesc) and thus to scale SIF760 from canopy to leaf level. Applying this approach reduces the influence of physical processes on far-red SIF and helps to better understand and interpret the physiological information content of the SIF signal.

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