Erosion effects of air pollution on needle surfaces

A scanning electron microscope was used to study the epicuticular wax of conifer needles from forests in the San Bernardino Mountains, California, the Austrian mountains near Graz and Finnish forests under local air pollution stress combined with the northern cold climate. The purpose of the study was to compare and define the role of needle erosion as a factor in tree damage, to compare the injury types in California and European countries and to characterize and further identify the possible role of 0₃ in needle injuries. In all cases in this preliminary study, there were chronic erosion effects in slightly stressed trees. The different sites where trees were studied, ranging from slightly polluted to heavily polluted areas characterized by different pollutant types, yielded a variety of erosion types. A new injury type related to insect and 0₃ effects in experimental and field studies was described. Additional research to confirm the results is needed.