Part III Direct Effects of Air Pollutants on Vegetation

Water, Air, and Soil Pollution

, Volume 85, Issue 3, pp 1317-1324

First online:

Are seedlings reasonable surrogates for trees? An analysis of ozone impacts on Quercus rubra

  • J. M. KellyAffiliated withTVA, Atmospheric Sciences
  • , L. SamuelsonAffiliated withSchool of Forestry, Auburn University
  • , G. EdwardsAffiliated withTVA, Atmospheric Sciences
  • , P. HansonAffiliated withEnvironmental Sciences Division, Oak Ridge National Laboratory
  • , D. KeltingAffiliated withCollege of Forestry and Wildlife Resources, Virginia Polytechnic Institute and State University
  • , A. MaysAffiliated withTVA, Atmospheric Sciences
  • , S. WullschlegerAffiliated withEnvironmental Sciences Division, Oak Ridge National Laboratory

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The appropriateness of using seedling responses to predict mature tree responses to ozone is questionable considering the long life span of trees. To determine if northern red oak (Quercus rubra L.) seedlings and mature trees respond similarly to ozone, 30-year-old trees and two-year-old seedlings were fumigated with subambient, ambient, and twice ambient concentrations of ozone for three growing seasons using an open-top chamber facility. Ozone reduced leaf physiological function of mature trees. However, stem diameter growth and leaf mass of mature trees were not significantly reduced by ozone. Photosynthesis in seedling leaves was slightly reduced by ozone, but seedling growth and biomass were unaffected. Mature tree fine-root biomass responded negatively to increasing ozone, while seedlings exhibited increases in biomass. Carbon retention was enhanced in leaves and branches of mature trees by ozone treatment, while seedlings were unresponsive. Differences in ozone uptake, recurrent flushing and carbon dynamics rather than microclimate may explain differences in ozone sensitivity between seedlings and mature trees. These results indicate that seedlings may not reflect the ozone sensitivity of larger more physiologically mature trees.

Key words

Northern Red Oak Open-Top Chambers Plant Stress Photosynthesis Carbon Allocation