EGU21-16102
https://doi.org/10.5194/egusphere-egu21-16102
EGU General Assembly 2021
© Author(s) 2021. This work is distributed under
the Creative Commons Attribution 4.0 License.

Canopy structure and stress induced changes in chlorophyll fluorescence – a mesocosm experiment

Albin Hammerle1, Mirco Migliavacca2, Felix Spielmann1, Javier Pacheco-Labrador2, and Georg Wohlfahrt1
Albin Hammerle et al.
  • 1University of Innsbruck, Ecology, Innsbruck, Austria (albin.hammerle@uibk.ac.at)
  • 2Max Planck Institute for Biogeochemistry, Department Biogeochemical Integration

Solar radiation absorbed by chlorophyll in plants is either used for photosynthesis, dissipated as heat or is re-emitted as fluorescence at a slightly higher wavelength. Sun induced chlorophyll fluorescence (SIF) has thus the potential to act as a sensitive indicator for early stress detection in ecosystems. SIF signals at the top of the canopy are however influenced by canopy structure and not only by plant physiology, due to light scattering and (re)absorption.

In this study we present the first results of a mesocosm experiment on the effect of drought stress on chlorophyll fluorescence in two plant stands differing in their canopy structure. In total we investigated 24 plots of planophile (Trifolium repens) and erectophile (Lolium perenne) plant stands. 12 plots acted as a control plots, while the remaining 12 plots underwent a progressively intensifying drought stress treatment. During the course of the experiment regular measurements of SIF using a passive spectrometer system were conducted. Furthermore, active chlorophyll fluorescence measurements with a multiplexed field spectrometer system were used to derive the maximum PSII efficiency (Fvm) and non-photochemical quenching (NPQ). Ancillary measurements included meteorological, leaf physiological, soil water and canopy structure variables.

The drought treatment led to a relatively stronger decrease in NDVI and a relatively higher increase in PRI in the Trifolium repens stand, which also experienced a more pronounced increase in NPQ, especially during hot days. For both stands surface temperatures were clearly higher in the treatment groups, with a larger effect in the Trifolium stand. SIF-yield (SIF/aPAR) did remain more or less constant or increased slightly for the control groups. In both stands it dropped towards the end of the experiment for both treatment groups at very low soil water content levels, about at the same time when the active chlorophyll fluorescence measurements started to indicate persistent reductions in Fvm. The relative decrease in SIF and SIF-yield for the treatment groups was not significantly different between the two stands.

How to cite: Hammerle, A., Migliavacca, M., Spielmann, F., Pacheco-Labrador, J., and Wohlfahrt, G.: Canopy structure and stress induced changes in chlorophyll fluorescence – a mesocosm experiment, EGU General Assembly 2021, online, 19–30 Apr 2021, EGU21-16102, https://doi.org/10.5194/egusphere-egu21-16102, 2021.

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