Impacts of long-term air pollution on trees through analysis of tree ring chemistry
Human activities release atmospheric pollutants that can impact tree growth and health. Some changes in the atmosphere have positive impacts on plants including carbon dioxide and nitrogen deposition. Other atmospheric pollutants have negative impacts on plants including sulfur dioxide and ozone. The total net effects from air pollution in natural ecosystems are not well understood. Improving understanding of these effects is important, both for management of natural areas and in quantifying the impacts of human activity on natural ecosystems. Trees in temperate regions have distinct annual growth patterns that allow for the measurement of physical properties of wood from each year of growth. Of particular use are long-lived trees that can provide a long-term record of environmental conditions experienced by the tree. This study will analyze chemical properties of tree rings from Quercus spp. in the Chicago, Illinois region to provide a record of environmental conditions from pre-industrial times through the present. In particular, the carbon isotope composition of wood is useful as a proxy for exposure to environmental stress. Several recent studies have demonstrated changes in tree-ring carbon isotopic composition with exposure to industrial pollutants. We will analyze changes in isotopic composition in trees proximate to an urban region where trees have experienced long-term exposure to high concentrations of atmospheric pollutants. Results will demonstrate the effects of industrial pollutants on tree physiology and document recovery from environmental stressors with the reduction of emissions in recent decades due to environmental legislation, as has been shown in other ecosystems.