Aspen Bibliography


An approach for characterizing tropospheric ozone risk to forests

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Environmental Management





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The risk tropospheric ozone poses to forests in the United States is dependent on the variation in ozone ex- posure across the distribution of the forests in question and the various environmental and climate factors predominant in the region. All these factors have a spatial nature, and consequently an approach to characterization of ozone risk is presented that places ozone exposure–response func- tions for species as seedlings and model-simulated tree and stand responses in a spatial context using a geographical information systems (GIS). The GIS is used to aggregate factors considered important in a risk characterization, in- cluding: (1) estimated ozone exposures over forested re- gions, (2) measures of ozone effects on species’ and stand growth, and (3) spatially distributed environmental, genetic, and exposure influences on species’ response to ozone. The GIS-based risk characterization provides an estimation of the extent and magnitude of the potential ozone impact on forests. A preliminary risk characterization demonstrating this approach considered only the eastern United States and only the limited empirical data quantifying the effect of ozone exposures on forest tree species as seedlings. The area- weighted response of the annual seedling biomass loss formed the basis for a sensitivity ranking: sensitive—aspen and black cherry (14%–33% biomass loss over 50% of their distribution); moderately sensitive—tulip popular, loblolly pine, eastern white pine, and sugar maple (5%–13% bio- mass loss); insensitive—Virginia pine and red maple (0%–1% loss). In the future, the GIS-based risk characteriza- tion will include process-based model simulations of the three- to 5-year growth response of individual species as large trees with relevant environmental interactions and model simulated response of mixed stands. The interactive nature of GIS provides a tool to explore consequences of the range of climate conditions across a species’ distribution, forest management practices, changing ozone precursors, regulatory control strategies, and other factors influencing the spatial distribution of ozone over time as more informa- tion becomes available.