Using dendroisotopes in North America and Asia to examine how temperate forests respond to changes in acid deposition

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Understanding the response of forests to air pollution is critical as it affects clean water, timber production and carbon storage. Comparing forests in different parts of the earth will help us understand if the response is uniform or regionally specific. This project compares forest responses in the temperate deciduous forest in the eastern United States and in eastern China. These two countries have opposite histories and trajectories of air pollution. When the Industrial Revolution began, air pollution in the form of acid deposition increased rapidly in the U.S. and was at high levels until the Clean Air Act was enacted in 1970 when the pollution dropped dramatically. Over the same time period, China has had low levels of air pollution until relatively recently as pollution levels have increased to historic highs. In a preliminary study using tree rings and carbon isotopes, an important isotopic signal was found in Eastern red cedars in the West Virginia that indicated these trees are now recovering from air pollution. This observation, however, is limited to a single species from a single stand of trees. This project will determine how wide-spread and universal this response is by using additional tree species along a transect stretching across the southern, central, and northern Appalachian region. Similar transects in China will be used to compare the isotopic signatures and growth of trees from similar genera that are currently undergoing opposite patterns of change in acid deposition. If widespread, results from this study will have important implications for carbon storage and cycling in many northern hemisphere forests, especially those downwind from pollution sources. Understanding such complexities will provide much needed information on the overall vulnerability and resilience of forests to dynamic changes in acidic pollution and atmospheric CO2. To broaden the societal impact of the proposed research, data will be made available to inform policy makers, federal land managers, modelers, and other scientists who may benefit from the results. Activities will be incorporated into effective learning activities for high school students and adults to provide a deeper understanding of the link between effective government policies (such as the Clean Air Act) and the health of forest ecosystems. Further, this project will provide training for graduate students and undergraduates, particularly those from facets of society that are underrepresented in science education and research.