title: New exposure-based metric approach for evaluating O(3) risk to North American aspen forests.
abstract: The United States and Canada currently use exposure-based metrics to protect vegetation from O(3). Using 5 years (1999-2003) of co-measured O(3), meteorology and growth response, we have developed exposure-based regression models that predict Populus tremuloides growth change within the North American ambient air quality context. The models comprised growing season fourth-highest daily maximum 8-h average O(3) concentration, growing degree days, and wind speed. They had high statistical significance, high goodness of fit, include 95% confidence intervals for tree growth change, and are simple to use. Averaged across a wide range of clonal sensitivity, historical 2001-2003 growth change over most of the 26 Mha P. tremuloides distribution was estimated to have ranged from no impact (0%) to strong negative impacts (-31%). With four aspen clones responding negatively (one responded positively) to O(3), the growing season fourth-highest daily maximum 8-h average O(3) concentration performed much better than growing season SUM06, AOT40 or maximum 1h average O(3) concentration metrics as a single indicator of aspen stem cross-sectional area growth.
authors.affiliation: Natural Resources Canada, Canadian Forest Service-Atlantic Forestry Centre, Fredericton, Canada. kpercy@nrcan.gc.ca
authors.forename: K E
authors.initials: KE
authors.lastname: Percy
authors.forename: M
authors.initials: M
authors.lastname: Nosal
authors.forename: W
authors.initials: W
authors.lastname: Heilman
authors.forename: T
authors.initials: T
authors.lastname: Dann
authors.forename: J
authors.initials: J
authors.lastname: Sober
authors.forename: A H
authors.initials: AH
authors.lastname: Legge
authors.forename: D F
authors.initials: DF
authors.lastname: Karnosky
mesh_terms: D000397:Air Pollution / Q000009:adverse effects; D004781:Environmental Exposure / Q000009:adverse effects; D004784:Environmental Monitoring / Q000379:methods; D015233:Models, Statistical; D009656:North America; D010083:Oxidants, Photochemical / Q000633:toxicity*; D010126:Ozone / Q000633:toxicity*; D032107:Populus / Q000187:drug effects / Q000254:growth & development*; D012044:Regression Analysis; D018570:Risk Assessment / Q000379:methods; D012621:Seasons; D035501:Uncertainty
chemical_list: D010083:Oxidants, Photochemical; D010126:Ozone