A preliminary study of the response of red spruce to O sub(3) and SO sub(2)

• Published in: Tellus. Series B, Chemical and physical meteorology Chemical and physical meteorology, 1993-01, Vol.45B (1), p.40-52
• Main Authors: Ennis, CA, Smith, J, Lazrus, AL
• Format: Article
• Language: English
• Subjects: Picea rubens
• ISSN: 0280-6509

A laboratory branch chamber experiment determined the response of a young red spruce (Picea rubens ) sapling to ozone (O sub(3)) and sulfur dioxide (SO sub(2)). A treatment branch was exposed to concentrations of O sub(3) ( similar to 90 ppbv) and SO sub(2) ( similar to 15 ppbv) representative of the summertime maxima observed in the high elevation spruce-fir forests of the eastern United States. A control branch of the same age and comparable biomass received clean air only. Pollution exposure, lasting 78 days, consisted of 4 sequential stages designed to compare the tree's response to each individual pollutant with its response to the combination of SO sub(2) + O sub(3). The treatment branch exhibited distinctly different physiological responses to O sub(3) alone, SO sub(2) alone, and the SO sub(2) + O sub(3) combination. Ozone exposure in the 1st stage induced an increase in CO sub(2) assimilation (20% over 26 days, relative to the control branch) while transpiration and nighttime respiration were unaffected. Ozone uptake increased markedly during this stage. In the 16-day 2nd stage of exposure, the combination of SO sub(2) + O sub(3) induced a factor of similar to 2 decrease in CO sub(2) assimilation, transpiration and O sub(3) uptake within 1 week. In the 3rd stage, the removal of SO sub(2) resulted in the partial recovery of photosynthetic uptake and other gas fluxes. A final stage of exposure to SO sub(2) alone produced large day-to-day variations in CO sub(2) assimilation. The isoprene emission rate of the treatment branch declined relative to the control branch over the course of the entire experiment. The results of this preliminary experiment suggest that, singly and in combination, O sub(3) and SO sub(2) may disrupt physiological functions of red spruce.