Contents lists available at ScienceDirect Atmospheric Environment journal homepage: www.elsevier.com/locate/atmosenv Dose-response relationships for ozone effect on the growth of deciduous broadleaf oaks in mediterranean environment Riccardo Marzuoli a,* , Filippo Bussotti b , Vicent Calatayud c , Esperanza Calvo c , Rocío Alonso d , Victoria Bermejo d , Martina Pollastrini b , Robert Monga a,e , Giacomo Gerosa a a Dept. of Mathematics and Physics, Università Cattolica del Sacro Cuore, via Musei 41, Brescia, Italy b Dept. of Agri-Food Production and Environmental Sciences (DISPAA), Università degli Studi di Firenze, Piazzale delle Cascine 18, Firenze, Italy c Fundación CEAM, c/ Charles R. Darwin 14, Parque Tecnológico, 46980, Paterna, Valencia, Spain d Ecotoxicology of Air Pollution, CIEMAT, Avda. Complutense 40, Madrid, Spain e Département de Gestion des Ressources Naturelles Renouvelables, Université de Lubumbashi, Democratic Republic of the Congo ARTICLE INFO Keywords: Ozone Broadleaf deciduous oaks Biomass Phytotoxic ozone dose Mediterranean environment ABSTRACT This study presents a reanalysis of ozone (O 3 ) exposure experiments performed on deciduous broadleaf oak species in the Mediterranean region and a proposal of critical levels to improve the O 3 risk assessment in this area for these widely distributed forest species. Two experiments performed in Spain and Italy were considered, and the following 3 oak species were studied: Quercus pyrenaica, Q. faginea and Q. robur. All the experiments were performed with irrigated potted seedlings growing in Open-Top Chambers exposed to different O 3 levels (with charcoal-filtered air as the control treatment) for two consecutive growing seasons. The Phytotoxic Ozone Dose above an instantaneous threshold of 1 nmol O 3 m -2 s -1 (POD 1 ) was calculated by applying a Jarvis type model for the estimation of the stomatal conductance (g s ), and by adopting a big-leaf resistive scheme to account for the O 3 deposition on the vegetation. Two parameterisations were used for the g s multiplicative model: one species-specific based on the “local” g s measurements performed during each experiment, and the other “gen- eric” based on the “Deciduous Mediterranean broadleaf” parameterisation described in the Manual on Methodologies and Criteria for Mapping Critical Loads and Levels and Air Pollution Effects, Risks and Trends of the UN/ECE (CLRTAP, 2015). The two different parameterisations were used to derive dose-response functions and ozone critical levels for the biomass loss of the deciduous oak species. The dose-response functions for roots and total biomass were statistically significant, with both the parameterisations tested (p < 0.05). The O 3 critical levels obtained indicate that deciduous broadleaf oaks in Mediterranean environment could be more tolerant to O 3 than other European broadleaf species and that O 3 is more harmful to the below-ground biomass of the plants rather than the above-ground biomass. 1. Introduction Tropospheric ozone pollution is one of the major threats for forests in the Mediterranean region, because climatic conditions and anthro- pogenic emissions of O 3 precursors tend to facilitate its photochemical formation and persistence during the spring/summer period. As a consequence, O 3 levels in this area frequently exceed the target values established by the 2008/50/CE directive to protect vegetation (EEA, 2013; Cristofanelli and Bonasoni, 2009; Proietti et al., 2016). The negative effects of O 3 on the physiology and growth of several forest species have been well documented in the last several decades, and many studies have highlighted detrimental effects such as visible leaf injuries (Gerosa et al., 2008; Marzuoli et al., 2009; Feng et al., 2014), accelerated leaf senescence (Gielen et al., 2007), reductions in stomatal conductance (g s ) and photosynthesis (Wittig et al., 2007), and declines in productivity (Wittig et al., 2009; Li et al., 2017). Although these effects have been studied and characterized in controlled or semi-controlled experiments mostly performed with potted young trees, there is also evidence that O 3 can affect mature trees in field conditions (Matyssek et al., 2007; Karnosky et al., 2005; Braun et al., 2010, 2014). Moreover, some authors found that the physiological and growth responses to O 3 of potted woody plants do not significantly differ from those of field-grown plants (Oksanen, 2003a; Coleman et al., 1996), although the pot volume under some circum- stances can be an important modifying factor for plants response to abiotic stresses (Poorter et al., 2012). https://doi.org/10.1016/j.atmosenv.2018.07.053 Received 13 April 2018; Received in revised form 27 July 2018; Accepted 29 July 2018 * Corresponding author. E-mail address: riccardo.marzuoli@unicatt.it (R. Marzuoli). Atmospheric Environment 190 (2018) 331–341 Available online 30 July 2018 1352-2310/ © 2018 Elsevier Ltd. All rights reserved. T