GROWTH AND NUTRITION OF QUERCUS-RUBRA L SEEDLINGS AND MATURE TREES AFTER 3 SEASONS OF OZONE EXPOSURE

Seedling growth and nutritional status have been shown to be sensitive to ozone, but the influence of multi-season ozone exposure on mature tree growth and nutrition has not been examined. To determine if seedl ings and mature trees were similarly affected by ozone exposure, growt h and nutrient concentrations in northern red oak (Quercus rubra L.) 4 -year-old seedlings and 32-year-old mature trees were examined after t reatment with subambient, ambient and twice ambient concentrations of ozone for three growing seasons. SUMOO values summed over the three gr owing seasons were 147, 255 and 507 ppm-h, respectively, for the subam bient, ambient and twice ambient exposures. For mature trees, no influ ence of ozone treatment on lower stem diameter growth, stem growth wit hin the mid-canopy and foliar biomass was observed Seedling height was increased by ozone, but biomass and diameter were unaffected A reduct ion in the specific leaf weight of leaves in response to ozone coincid ent with the loss of recurrent flushing was observed in seedlings. Ozo ne exposure reduced foliar nitrogen concentrations and increased woody tissue nutrient concentrations in seedlings and mature trees at the e nd of the third growing season. These results suggest an influence of ozone on retranslocation processes in seedlings and mature trees.