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

了解森林对空气污染的反应至关重要，因为它影响清洁水、木材生产和碳储存。比较地球不同地区的森林将有助于我们了解这种反应是统一的还是区域性的。本项目比较了美国东部和中国东部温带落叶森林的森林响应。这两个国家在空气污染方面有着截然相反的历史和轨迹。当工业革命开始时，美国的空气污染以酸沉积的形式迅速增加，一直处于高水平，直到1970年颁布《清洁空气法》，污染才急剧下降。在同一时期，中国的空气污染水平一直很低，直到最近污染水平上升到历史最高水平。在一项利用树木年轮和碳同位素的初步研究中，在西弗吉尼亚州的东部红杉中发现了一个重要的同位素信号，表明这些树木正在从空气污染中恢复过来。然而，这种观察仅限于来自单一树种的单一物种。该项目将通过在阿巴拉契亚地区南部、中部和北部的样带上使用额外的树种来确定这种反应的广泛性和普遍性。中国的类似样带将用于比较来自相似属的树木的同位素特征和生长，这些树木目前正在经历相反的酸沉积变化模式。如果得到广泛应用，这项研究的结果将对北半球许多森林的碳储存和循环产生重要影响，特别是那些污染源下风的森林。了解这种复杂性将提供关于森林对酸性污染和大气二氧化碳动态变化的总体脆弱性和复原力的急需信息。为了扩大拟议研究的社会影响，数据将提供给政策制定者、联邦土地管理者、建模者和其他可能从研究结果中受益的科学家。这些活动将被纳入针对高中生和成年人的有效学习活动中，以便更深入地了解有效的政府政策（如《清洁空气法》）与森林生态系统健康之间的联系。此外，该项目将为研究生和本科生提供培训，特别是那些来自科学教育和研究中代表性不足的社会方面的学生。

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.