@article{8d1e5d44498c422b909b04adb4734a5f,
title = "Heatwave breaks down the linearity between sun-induced fluorescence and gross primary production",
abstract = "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.",
keywords = "ITC-ISI-JOURNAL-ARTICLE",
author = "David Martini and Karolina Sakowska and Georg Wohlfahrt and Javier Pacheco-Labrador and {van der Tol}, C. and Albert Porcar-Castell and Magney, {Troy S.} and Arnaud Carrara and Roberto Colombo and El-Madany, {Tarek S.} and Rosario Gonzalez-Cascon and Mart{\'i}n, {Mar{\'i}a Pilar} and Tommaso Julitta and Gerardo Moreno and Uwe Rascher and Markus Reichstein and Micol Rossini and Mirco Migliavacca",
note = "Funding Information: This project received funding from the European Union{\textquoteright}s Horizon 2020 research and innovation programme under the Marie Sk{\l}odowska‐Curie grant agreement nos. 721995 and 749323. The authors acknowledge the Alexander von Humboldt Foundation for supporting this research with the Max‐Planck Prize to Markus Reichstein. We also acknowledge the European Space Agency (ESA) in the frame of the FLEXSense campaign (ESA contract no. 4000125402/18/NL/NA) and the Photoproxy campaign (ESA contract no. 4000125731/19/NL/LF). MMigliavacca and GWohlfahrt acknowledge funding from the joint FWF‐DFG DACH project {\textquoteleft}Constraining terrestrial gross primary productivity by joint measurements of the carbonyl sulfide exchange and sun‐induced fluorescence{\textquoteright}. GWohlfahrt further acknowledges financial support by the AustroSIF project, which is funded by the FFG and BMK within the Austrian Space Applications Programme. Publisher Copyright: {\textcopyright} 2021 The Authors. New Phytologist {\textcopyright} 2021 New Phytologist Foundation",
year = "2022",
month = mar,
day = "1",
doi = "10.1111/nph.17920",
language = "English",
volume = "233",
pages = "2415--2428",
journal = "New phytologist",
issn = "0028-646X",
publisher = "Wiley-Blackwell",
number = "6",
}