9652675 Karnosky The greenhouse gases, carbon dioxide (CO2) and ozone (O3), are increasing globally and are closely tracking population growth. Little is known about how these two gases will impact forest communities, as, until now, studies with these gases were done in artificial environments created by exposure chambers. In this, project we are using a state-of-the-art Free-Air Carbon Dioxide Enrichment (FACE) facility to facilitate long-term exposures of regenerating forest stands to elevated CO2 and O3, alone and in combination. The facility is being constructed on United States Forest Service land near Rhinelander, Wisconsin. A multidisciplinary team of scientists will examine mechanisms and responses in trembling aspen (Populus tremuloides), sugar maple (Acer saccharum) and paper birch (Betula papyrifera) in various competitive combinations. Of particular interest are: (1) tree physiology, growth, survival, and productivity; (2) competitive interactions among genotypes and species; (3) tree and stand carbon and nitrogen allocation; (4) pest and stress tolerance as regulated by foliar defense compounds; and (5) carbon and nitrogen cycling and ecosystem carbon storage. Three replicate FACE rings are being established for a factorial combination of treatments (control, CO2, O3, CO2, + O3) in a randomized complete block design. Our research strategy will include parallel experimentation and modeling. Thus, response data from these treatment combinations will be used to parameterize and refine an existing whole-tree and stand level process model. Our experimental design will allow us to address specific hypotheses using species of contrasting life-histories, while also affording the largest possible scope of inference for model parameterization.
