We studied the effect of high ozone (O3) concentration (110-490 nmol mol-1) on regenerating aspen (Populus tremuloides) and maple (Acer saccharum) trees at an open-air O3 pollution experiment near Rhinelander WI USA. This study is the first of its kind to examine the effects of acute O3 exposure on aspen and maple sprouts after the parent trees, which were grown under elevated O3 and/or CO2 for 12 years, were harvested. Acute O3 damage was not uniform within the crowns of aspen suckers; it was most severe in the mature, fully expanded photosynthesizing leaves. Young expanding leaves showed no visible signs of acute O3 damage contrary to expectations. Stomatal conductance played a primary role in the severity of acute O3 damage as it directly controlled O3 uptake. Maple sprouts, which had lower stomatal conductance, smaller stomatal aperture, higher stomatal density and larger leaf surface area, were tolerant of acute O3 exposure. Moreover, elevated CO2 did not ameliorate the adverse effects of acute O3 dose on aspen and maple sprouts, in contrast to its ability to counteract the effects of long-term chronic exposure to lower O3 levels.
Darbah, Joseph N.T.; Jones, Wendy S.; Burton, Andrew J.; Nagy, John; Kubiske, Mark E. 2011. Acute O3 damage on first year coppice sprouts of aspen and maple sprouts in an open-air experiment. Journal of Environmental Monitoring. 13: 2436-2442.