Heatwave breaks down the linearity between sun‐induced fluorescence and gross primary production

Summary Sun‐induced fluorescence in the far‐red region (SIF) is increasingly used as a remote and proximal‐sensing tool capable of tracking vegetation gross primary production (GPP). However, the use of SIF to probe changes in GPP is challenged during extreme climatic events, such as heatwaves. Here...

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Published in:The New phytologist 2022-03, Vol.233 (6), p.2415-2428
Main Authors: Martini, David, Sakowska, Karolina, Wohlfahrt, Georg, Pacheco‐Labrador, Javier, van der Tol, Christiaan, Porcar‐Castell, Albert, Magney, Troy S., Carrara, Arnaud, Colombo, Roberto, El‐Madany, Tarek S., Gonzalez‐Cascon, Rosario, Martín, María Pilar, Julitta, Tommaso, Moreno, Gerardo, Rascher, Uwe, Reichstein, Markus, Rossini, Micol, Migliavacca, Mirco
Format: Article
Language:English
Subjects:
Canopies
Canopy
Chlorophyll - analysis
Ecosystem
Energy dissipation
Energy exchange
Environmental Monitoring - methods
Evergreen trees
extreme events
Extreme heat
Fluorescence
gross primary production (GPP)
Heat stress
Heat tolerance
heatwave
Heatwaves
Light intensity
Luminous intensity
nonphotochemical quenching
Photosynthesis
Plant cover
Primary production
Pulse amplitude modulation
Radiative transfer
Remote sensing
Saturation
Seasons
sun‐induced fluorescence
Tracking
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Summary:Summary Sun‐induced fluorescence in the far‐red region (SIF) is increasingly used as a remote and proximal‐sensing tool capable of tracking vegetation gross primary production (GPP). However, the use of SIF to probe changes in GPP is challenged during extreme climatic events, such as heatwaves. Here, we examined how the 2018 European heatwave (HW) affected the GPP–SIF relationship in evergreen broadleaved trees with a relatively invariant canopy structure. To do so, we combined canopy‐scale SIF measurements, GPP estimated from an eddy covariance tower, and active pulse amplitude modulation fluorescence. The HW caused an inversion of the photosynthesis–fluorescence relationship at both the canopy and leaf scales. The highly nonlinear relationship was strongly shaped by nonphotochemical quenching (NPQ), that is, a dissipation mechanism to protect from the adverse effects of high light intensity. During the extreme heat stress, plants experienced a saturation of NPQ, causing a change in the allocation of energy dissipation pathways towards SIF. Our results show the complex modulation of the NPQ–SIF–GPP relationship at an extreme level of heat stress, which is not completely represented in state‐of‐the‐art coupled radiative transfer and photosynthesis models.
ISSN:0028-646X
1469-8137
1469-8137
DOI:10.1111/nph.17920