Public thesis defense of Simon DE CANNIERE
"Remote sensing of drought stress with sun-induced chlorophyll fluorescence from canopy to global scale"
When: 24/08/2023 at 4 PM
Where: Ocean room - de Serres building LLN + TEAMS LINK
Chairman:
Prof. Marnik VANCLOOSTER
Supervisors:
Prof. François JONARD
Prof. Pierre DEFOURNY
Other jury members:
Prof. Xavier DRAYE
Prof. Harry VEREECKEN (FZ Jülich)
Ivan JANSSENS (Université d'Anvers)
Abstract
During droughts, plants have to make a trade-off between minimizing water loss and allowing CO2 uptake. This trade-off is regulated with the stomatal guard cells, the opening of which determines the joint gas exchange of CO2 and water with the atmosphere.
The decrease of the CO2 uptake slows down the entire photosynthetic machinery, causing various reactions at the level of the photosystem. Amidst these reactions, the decrease of the CO2 uptake changes the sun-induced chlorophyll fluorescence emission, making it an interesting signal for drought stress detection.
However, many questions arise regarding the translation of the physiological processes to remote-sensing data. This is where this thesis jumps in: by studying chlorophyll fluorescence at various scales, it makes a journey from the photosystems, over the leaf and plot scales, to the global scale. At the photosystem scale, there is a clear difference in the partitioning of absorbed energy between photosynthesis, non-photochemical quenching and fluorescence emission between stressed and unstressed plants. This sensitivity can serve as the backbone of the calibration for a stress module in a crop growth model, as SIF provides a measured basis of stress intensity. Such an approach improved spectacularly the estimations of the field-scale carbon and water fluxes during the Summer months. The sensitivity between the photosystem-level fluorescence emission and the stress intensity was also observable at the global scale through a combination of satellite data.
The precise nature of the SIF-stress relationship of a certain location was affected by the local isohydricity. The sensitivity of the fluorescence signal to stress conditions at both the local and global scale is promising in light of the upcoming FLuorescence EXplorer (FLEX) mission, scheduled for launch in 2025.
|
