CNR ExploRA

Articolo in rivista, 2023, ENG, 10.1016/j.scitotenv.2023.166149

Detection and attribution of an anomaly in terrestrial photosynthesis in Europe during the COVID-19 lockdown

Angela Che Ing Tang, Christophe R Flechard, Nicola Arriga, Dario Papale, Paul C Stoy, Nina Buchmann, Matthias Cuntz, John Douros, Silvano Fares, Alexander Knohl, Ladislav ?igut, Guillaume Simioni, Renske Timmermans, Thomas Grünwald, Andreas Ibrom, Benjamin Loubet, Ivan Mammarella, Luca Belelli Marchesini, Mats Nilsson, Matthias Peichl, Corinna Rebmann, Marius Schmidt, Christian Bernhofer, Daniel Berveiller, Edoardo Cremonese, Tarek S El-Madany, Mana Gharun, Damiano Gianelle, Lukas Hörtnagl, Marilyn Roland, Andrej Varlagin, Zheng Fu, Bernard Heinesch, Ivan Janssens, Natalia Kowalska, Ji?í Du?ek, Giacomo Gerosa, Meelis Mölder, Eeva-Stiina Tuittila, Denis Loustau

ISPA, Bordeaux Sciences Agro, INRAE, Villenave d'Ornon, France b Department of Environmental Sciences, University of Toledo, Toledo, OH, USA c UMR SAS, INRAE, Institut Agro, Rennes, France d Joint Research Centre, European Commission, Ispra, Italy e University of Tuscia DIBAF, Viterbo, Italy f EuroMediterranean Center on Climate Change, CMCC IAFES, Viterbo, Italy g Department of Biological Systems Engineering, University of Wisconsin-Madison, Madison, WI, USA h Department of Environmental Systems Science, ETH Zurich, Zurich, Switzerland i Universit´e de Lorraine, AgroParisTech, INRAE, UMR Silva, Nancy, France j Royal Netherlands Meteorological Institute (KNMI), De Bilt, The Netherlands k National Research Council of Italy, Institute for Agriculture and Forestry Systems in the Mediterranean, Naples, Italy l Bioclimatology, University of Gottingen, ¨ Gottingen, ¨ Germany m Department of Matter and Energy Fluxes, Global Change Research Institute of the Czech Academy of Sciences, Brno, Czech Republic n URFM, INRAE, Avignon, France o Climate Air and Sustainability Unit, Netherlands Organisation for Applied Scientific Research (TNO), Utrecht, The Netherlands p Faculty of Environmental Sciences, Institute of Hydrology and Meteorology, Technische Universitat ¨ Dresden, Tharandt, Germany q Technical University of Denmark (DTU), DTU-Sustain, Kgs. Lyngby, Denmark r UMR ECOSYS, AgroParisTech, INRAE, Universit´e Paris-Saclay, Thiverval-Grignon, France s Institute for Atmospheric and Earth System Research/Physics, University of Helsinki, Helsinki, Finland t Research and Innovation Centre, Fondazione Edmund Mach, San Michele all'Adige, Italy u Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, Umeå, Sweden v Department of Computational Hydrosystems, Helmholtz Centre for Environmental Research - UFZ, Leipzig, Germany w Institute of Bio- and Geosciences: Agrosphere (IBG-3), Jülich Research Centre, Jülich, Germany x Universit´e Paris-Saclay, CNRS, AgroParisTech, Ecologie Syst´ematique et Evolution, Orsay, France y Environmental Protection Agency of Aosta Valley - Climate Change Unit, Saint-Christophe, Italy z Max Planck Institute for Biogeochemistry, Department of Biogeochemical Integration, Jena, Germany aa Faculty of Geosciences, University of Münster, Münster, Germany ab Department of Biology, University of Antwerp, Wilrijk, Belgium ac A.N. Severtsov Institute of Ecology and Evolution, Russian Academy of Sciences, Moscow, Russia ad Laboratoire des Sciences du Climat et de l'Environnement, LSCE/IPSL, CEA-CNRS-UVSQ, Universit´e Paris-Saclay, Gif-sur-Yvette, France ae TERRA Teaching and Research Centre, University of Liege, Gembloux, Belgium af Universita ` Cattolica del Sacro Cuore, Brescia, Italy ag Department of Physical Geography and Ecosystem Science, Lund University, Lund, Sweden ah School of Forest Sciences, University of Eastern Finland, Joensuu, Finland

Carbon dioxide (CO2) uptake by plant photosynthesis, referred to as gross primary production (GPP) at the ecosystem level, is sensitive to environmental factors, including pollutant exposure, pollutant uptake, and changes in the scattering of solar shortwave irradiance (SWin) - the energy source for photosynthesis. The 2020 spring lockdown due to COVID-19 resulted in improved air quality and atmospheric transparency, providing a unique opportunity to assess the impact of air pollutants on terrestrial ecosystem functioning. However, detecting these effects can be challenging as GPP is influenced by other meteorological drivers and management practices. Based on data collected from 44 European ecosystem-scale CO2 flux monitoring stations, we observed significant changes in spring GPP at 34 sites during 2020 compared to 2015-2019. Among these, 14 sites showed an increase in GPP associated with higher SWin, 10 sites had lower GPP linked to atmospheric and soil dryness, and seven sites were subjected to management practices. The remaining three sites exhibited varying dynamics, with one experiencing colder and rainier weather resulting in lower GPP, and two showing higher GPP associated with earlier spring melts. Analysis using the regional atmospheric chemical transport model (LOTOS-EUROS) indicated that the ozone (O3) concentration remained relatively unchanged at the research sites, making it unlikely that O3 exposure was the dominant factor driving the primary production anomaly. In contrast, SWin increased by 9.4 % at 36 sites, suggesting enhanced GPP possibly due to reduced aerosol optical depth and cloudiness. Our findings indicate that air pollution and cloudiness may weaken the terrestrial carbon sink by up to 16 %. Accurate and continuous ground-based observations are crucial for detecting and attributing subtle changes in terrestrial ecosystem functioning in response to environmental and anthropogenic drivers.

Science of the total environment 903 (166149)