title: An epidemiological assessment of stomatal ozone flux-based critical levels for visible ozone injury in Southern European forests.
abstract: Southern forests are at the highest ozone (O3) risk in Europe where ground-level O3 is a pressing sanitary problem for ecosystem health. Exposure-based standards for protecting vegetation are not representative of actual field conditions. A biologically-sound stomatal flux-based standard has been proposed, although critical levels for protection still need to be validated. This innovative epidemiological assessment of forest responses to O3 was carried out in 54 plots in Southeastern France and Northwestern Italy in 2012 and 2013. Three O3 indices, namely the accumulated exposure AOT40, and the accumulated stomatal flux with and without an hourly threshold of uptake (POD1 and POD0) were compared. Stomatal O3 fluxes were modeled (DO3SE) and correlated to measured forest-response indicators, i.e. crown defoliation, crown discoloration and visible foliar O3 injury. Soil water content, a key variable affecting the severity of visible foliar O3 injury, was included in DO3SE. Based on flux-effect relationships, we developed species-specific flux-based critical levels (CLef) for forest protection against visible O3 injury. For O3 sensitive conifers, CLef of 19 mmol m(-2) for Pinus cembra (high O3 sensitivity) and 32 mmol m(-2) for Pinus halepensis (moderate O3 sensitivity) were calculated. For broadleaved species, we obtained a CLef of 25 mmol m(-2) for Fagus sylvatica (moderate O3 sensitivity) and of 19 mmol m(-2) for Fraxinus excelsior (high O3 sensitivity). We showed that an assessment based on PODY and on real plant symptoms is more appropriated than the concentration-based method. Indeed, POD0 was better correlated with visible foliar O3 injury than AOT40, whereas AOT40 was better correlated with crown discoloration and defoliation (aspecific indicators). To avoid an underestimation of the real O3 uptake, we recommend the use of POD0 calculated for hours with a non-null global radiation over the 24-h O3 accumulation window.
authors.affiliation: ACRI-HE, 260 route du Pin Montard, BP 234, 06904 Sophia Antipolis cedex, France. Electronic address: pierre.sicard@acri-he.fr.
authors.forename: Pierre
authors.initials: P
authors.lastname: Sicard
authors.affiliation: ENEA (Italian National Agency for New Technologies, Energy and Sustainable Economic Development), 76, Lungotevere Thaon de Revel, Rome, Italy.
authors.forename: Alessandra
authors.initials: A
authors.lastname: De Marco
authors.affiliation: GIEFS (Groupe International d'Etudes des Forêts Sud-européennes), 60, Avenue des Hespérides, 06300 Nice, France.
authors.forename: Laurence
authors.initials: L
authors.lastname: Dalstein-Richier
authors.affiliation: IPLA (Istituto per le Piante da Legno e l'Ambiente), Corso Casale 476, 10132 Turin, Italy.
authors.forename: Francesco
authors.initials: F
authors.lastname: Tagliaferro
authors.affiliation: ACRI-HE, 260 route du Pin Montard, BP 234, 06904 Sophia Antipolis cedex, France.
authors.forename: Camille
authors.initials: C
authors.lastname: Renou
authors.affiliation: IPSP-CNR (Consiglio Nazionale delle Ricerche - Istituto per la Protezione Sostenibile delle Piante), Via Madonna del Piano 10, 50019 Sesto Fiorentino (Florence), Italy.
authors.forename: Elena
authors.initials: E
authors.lastname: Paoletti
mesh_terms: D000393:Air Pollutants / Q000032:analysis* / Q000378:metabolism; D004784:Environmental Monitoring / Q000379:methods*; D029964:Fagus / Q000737:chemistry / Q000378:metabolism; D065928:Forests; D005602:France; D007558:Italy; D008956:Models, Chemical; D010126:Ozone / Q000032:analysis* / Q000378:metabolism; D054046:Plant Stomata / Q000737:chemistry / Q000378:metabolism*
chemical_list: D000393:Air Pollutants; D010126:Ozone
keywords: Critical levels; Epidemiology; Ozone; POD; Stomatal flux-based; Visible injury