Evidence for potential impacts of ozone on Pinus cembra L. at mountain sites in Europe: An overview

We summarize what is known about the impact of ozone (O3) on Pinus cembra in the timberline ecotone of the central European Alps and the Carpathian Mountains. In the central European Alps exposure to ambient and two-fold ambient O3 throughout one growing season did neither cause any visible injury nor affect the photosynthetic machinery and biochemical parameters in current to 1-year-old needles. By contrast, in the southern French Alps and in the Carpathians 1-year-old needles of Pinus cembra trees showed visual symptoms similar to those observed in O3 stressed pine stands in southern California. For the southern French Alps the observed symptoms could clearly be attributed O3 and differences in O3 uptake seems to be the likely key factor for explaining the observed decline. For the Carpathians however, other reasons such as drought may not be excluded in eliciting the observed symptoms. Thus, the action of O3 has always to be evaluated in concert with other environmental impacts, determining the treeʹs sensitivity to stress.