Ozone injury symptoms on vegetation in an Alpine valley, North Italy

In recent years multidisciplinary surveys examining the impact of pollutants on forest ecosystems have been carried out in the Valtellina (Northern Italy, Alpine region). A large part of the activity of these surveys has involved the study of ozone and its distribution in the area, development of the exceedances maps (AOT40) and their validation by means of field observation of visible foliar symptoms in the indigenous and sensitive forest vegetation. The present paper reports the results of a field survey carried out in 1998 on the visible symptoms expressed by several native species (trees, shrubs and herbs). A non-systematic grid of 81 plots was assessed throughout the valley. Due to the high variability of the physical (altitude, slope, exposure, etc.) and vegetational (species assemblage, tree age, forest structure) features, the comparability among the plots was found to be very weak, so only the presence or absence of leaf injuries was assessed. Results do not show any correlation between the distribution of foliar symptoms in Valtellina and ozone levels. Rather, leaf injuries follow the same distribution of environmental modifying factors (such as depth and moisture of the soil) and tree sensitivity. © 2003 Elsevier Science Ltd. All rights reserved.