Journal Article

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

Moreno, Gerardo, Martini, David, Sakowska, Karolina, Martín, María Pilar, Magney, Troy S., Gonzalez-Cascon, Rosario, El-Madany, Tarek S., van der Tol, Christiaan, Rossini, Micol, Carrara, Arnaud, Rascher, Uwe, Julitta, Tommaso, Colombo, Roberto, Migliavacca, Mirco, Porcar-Castell, Albert, Wohlfahrt, Georg, Pacheco-Labrador, Javier, Reichstein, Markus

2022

Overview

• 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.

• Publisher: Wiley,Wiley Subscription Services, Inc
• Subject: Canopies / Canopy / Chlorophyll - analysis / Ecosystem / eddy covariance / Energy dissipation / Energy exchange / Environmental Monitoring - methods / Evergreen trees / extreme events / Extreme heat / Fluorescence / gross primary production (GPP) / gross primary productivity / Heat stress / Heat tolerance / Heat waves / heatwave / Heatwaves / leaves / Light intensity / Luminous intensity / nonphotochemical quenching / Photosynthesis / Plant cover / Primary production / Pulse amplitude modulation / Radiative transfer / Remote sensing / Saturation / Seasons / sun‐induced fluorescence / Tracking / vegetation