Plant responses to elevational gradients of O(3) exposures in Virginia.

In Shenandoah National Park, O(3) monitoring data were characterized and attempts were made to relate O(3) concentration levels to visible foliar injury observed for five plant species surveyed. Foliar injury for three species increased with elevation. The 24-h monthly mean O(3) concentrations tended to increase with elevation; however, the number of elevated hourly occurrences did not. Although the frequency of high hourly O(3) concentrations did not consistently increase with elevation, O(3) exposures in the park may have been high enough to provoke an effect that may have been enhanced by vegetation sensitivities that differed as a function of altitude.