Visible Ozone Injury on Forest Trees in Great Smoky Mountains National Park, USA

Abstract

During the summer of 1991 ozone injury trend plots in Great Smoky Mountains National Park, USA, consisting of mature black cherry, sassafras and yellow-poplar were established near three ozone monitors, ranging in elevation from 597–1265 m. Beginning in mid-August 1991–1993, three exposed branches each from the upper- and mid- to lower-crown of each tree were collected and evaluated for ozone injury. Of the trees examined, 63%, 52% and 36% exhibited some amount of foliar injury in 1991, 1992 and 1993, respectively. Ozone injury across species was the greatest at Cove Mountain in all three years of the study. Overall, across sites and years, 11, 12 and 11% of all leaves examined exhibited visible injury for black cherry, sassafras and yellow-poplar, respectively. The percentage of injured leaves per branch was greater in the mid- to lower-canopy for black cherry, across all sites. Trees for each species that exhibited the greatest or least amounts of visible injury did so in all three years of the study, indicating a differential sensitivity within each species population. No significant ozone exposure-tree response relationships were observed with any variable tested. These data indicate that ozone concentrations are high enough to cause visible symptoms to selected trees within Great Smoky Mountains National Park, USA.