New exposure-based metric approach for evaluating O < inf> 3 risk to North American aspen forests

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The United States and Canada currently use exposure-based metrics to protect vegetation from O3. Using 5 years (1999-2003) of co-measured O3, 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 O3 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 M ha 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 O3, the growing season fourth-highest daily maximum 8-h average O3 concentration performed much better than growing season SUM06, AOT40 or maximum 1 h average O3 concentration metrics as a single indicator of aspen stem cross-sectional area growth. © 2006 Elsevier Ltd. All rights reserved.

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Environmental Pollution