PARENT SESSION
Organized Oral Session 1: Understanding the impacts of oxidative stress in plants: From molecules to ecosystems
Organizer(s): HS Neufeld and N Grulke
Monday, August 8, 8:00 AM - 11:30 AM, Meeting Room 510a, Level 5, Palais des congrès de Montréal
A meta-analysis of elevated tropospheric O3 effects on tree physiology and biomass accumulation.
Wittig, Victoria*,1, Naidu, Shawna2, Karnosky, David3, Long, Stephen 1, 2, 1 Deparment of Plant Biology, Urbana, IL, USA2 Department of Crop Sciences, Urbana, IL, USA3 School of Forest Resources and Environmental Science, Houghton, MI, USA
ABSTRACT- Current projections of the rise in atmospheric carbon dioxide concentration assume significant buffering through uptake of carbon into the forests of the northern hemisphere. These projections fail to account for the fact that tropospheric ozone concentration ([O3]), is also rising and because of its phytoxicity, is likely to decrease carbon uptake. Although commonly viewed as a problem of large cities, high [O3] is impacting trees across many rural areas of the northern hemisphere. A further 45% increase in [O3] is predicted over this century, and by its end, most northern hemisphere forests will be subject to damaging concentrations. Despite a wealth of controlled-environment and field experiments examining photosynthetic carbon uptake by trees fumigated with elevated [O3], establishing the likely direction and magnitude of the response has been inhibited by the large variability in observations. In this project a comprehensive data base of more than 1000 primary research studies was established and intended to include all primary research conducted on trees exposed to ozone for last 30 plus years. Meta-analytic techniques were employed to establish the best estimate and statistical confidence limits of the impact of rising [O3] on tree function and future forest carbon uptake. Modification of the response by tree age, functional type and experimental design were also extracted. Results indicated that net photosynthesis (Anet) is decreased by 18% when exposed to the elevation of [O3] anticipated for the middle of this century, with no significant difference between functional type, duration of exposure or type of exposure chamber. The response of Anet to elevated [O3] exposure did vary significantly with the rooting volume, tree age and ozone concentration. The results show a very significant impact of rising [O3] more than sufficient to nullify any potential of northern hemisphere forests to continue as a net sink for increasing atmospheric CO2.
Key words: tropospheric ozone, meta-analysis, trees, global change