The effect of ozone on pine forests in South-Eastern France from 2017 to 2019

Abstract

In South-Eastern forests of France, risks linked to the effects of tropospheric ozone (O₃) are real; its annual impact has been observed specifically near the coastline and in high altitude mountains during the period 2017 − 2019. In this study, the risk assessment of O₃ pollutant was carried out using two approaches based on forest response indicators such as O₃ specific foliar visible injury and by stomatal O₃ flux. Phytotoxic O₃ dose values (POD₀) were obtained by the DO₃SE model. The model requires hourly O₃ concentration for POD₀ calculation. A modified approach that uses measurements from passive samplers (monthly average O₃ concentration) was tested for the calculation of POD₀ and test results showed good agreement with the POD₀ calculated using hourly O₃ data. In the model input file, the average O₃ concentration is used for POD₀, and this could be useful for POD₀ calculation when the active monitor is limited. In this study, a flux-based assessment provided better correlation with O₃ specific leaf injury, which is also species-specific. Foliar visible injury in response to O₃ indicates that Pinus cembra and Pinus halepensis are more affected and therefore more sensitive than Pinus sylvestris. The POD₀ and stomatal conductance (G _sto) seem to be induced by environmental factors, primarily rainfall and the soil water potential (ƒ_SWP). The correlation between the O₃ flux metric and environmental variables with forest response indicators by Spearman rank test confirms P. cembra as one of the most sensitive species to O₃.

Keywords

Ozone / Foliar visible injury / Phytotoxic ozone dose / Stomatal conductance / DO₃SE