Abstract

Keywords

ozone, above-ground part of trees, Methods: open-field fumigation, open-field fumigation

Abstract

Tropospheric ozone (O3) may adversely affect tree growth, with critical levels for ozone being exceeded in many parts of Europe. However, unequivocal evidence for ozone-induced foliar injury on woody species under field conditions has only been found in a few places. Visible ozone injury appears to occur mainly in the Mediterranean Basin, which is also the area where the least amount of information is available on the sensitivity of individual species. Overall, the quantitative risk assessment of O3 impacts on mature trees and forests is vague at the European scale, as most knowledge derives from controlled O3 fumigations of young trees, growing in isolation in exposure chambers. Research suggests that risks exist, but these need to be validated for stand conditions. Ozone-caused changes in resource allocation rather than productivity appear to be crucial as they affect competitiveness and predisposition to parasite attack and eventually may lead to the loss of genetic diversity. ‘Free-air’ O3 fumigations in forest canopies may reveal processes that are susceptible to O3 stress under given stand conditions and provide a scientific basis towards quantitative risk assessment and realistic definitions of critical levels for ozone in forest ecosystems.

LWF Classification

Network: LWF, Category: ISI,