engleski

How high are ozone concentrations in Mediterranean forest ecosystems?

Ozone is strong oxidative air pollutant produced in photochemical reaction by precursor compounds (CH4, CO, NOx, VOC) at high temperatures and sunlight. This air pollutant is the most damaging to forests among other air pollutants. Ground- level ozone is of particular concern for forest ecosystems in Mediterranean region. The reason is that regional road traffic and industrial emissions combined with high temperatures and sunlight in Mediterranean region result in higher ozone concentrations than in other European regions. The aim was to measure ozone concentrations and determines whether these concentrations represent threat to Mediterranean forest ecosystems in Croatia. Ozone concentrations were measured with passive Ogawa samplers in four forest ecosystems in two regions: Quercus ilex and Quercus pubescens forests in Istria, Pinus halepensis and Pinus nigra forests in Dalmatia. From measured data, two different ozone metrics for forest protection were calculated ; accumulated ozone exposure (AOT40) and phytotoxic stomatal ozone fluxes (PODY) with an hourly threshold of uptake (Y) to represent the detoxification capacity of trees used for forest protection. Measured ozone concentrations were high on all four plots and were close to or reached 100 ppb recommended as an upper plausible limit for passive monitoring measurements at forest sites. Higher average concentrations were measured in Istria than in Dalmatia. The values of the calculated metrics based on accumulated exposure (AOT40) were higher than limit for forest protection. The highest values for PODY metrics were found in Dalmatian plot and the lowest values were found on Istrian plot. RFA analyses underlined that the most important predictors affecting tree growth of Q. pubescens and Q. ilex were AOT40 and for P. nigra plot was PODY. Ozone concentrations were high enough to cause symptoms indicative of oxidative stress found on ground- level plants in the oak forest in Istria but not on main forest species. Acknowledgement: This work has been fully supported by Croatian Science Foundation under the project IP-06-2016-3337.

A0T40. ozone metrics, Pinus forests, PODY, Quercus forests

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