DISSERTATION RESEARCH: Combined Effects of Elevated NO2, O3, and CO2 on Plant Growth and Productivity

本研究的目的是确定几种可能在下个世纪急剧增加的大气气体[二氧化碳（CO2）、二氧化氮（NO2）和臭氧（O3）]对糖枫、东铁杉、颤杨和红橡树幼苗的叶片生理和整体生长的单一和联合影响。树木熏蒸时使用升高的（40ppb）或环境NO2，升高的（560ppm）或环境CO2，升高的（100 ppb）或环境O3，并在有或没有额外土壤施肥的原生土壤中生长。幼苗生长和叶片生理性能（如光合作用、气孔导度）将被连续测量，在实验结束时，每个物种的总生长将被测量，并归因于暴露于污染熏蒸的差异。人类活动已经引起了大气化学成分的变化：CO2、NO2和O3的浓度已经增加，预计将来还会继续增加。植物既通过改变生理过程受到这些气体的影响，又有能力从大气中清除气体，在某些情况下，还能将这些气体中的碳和氮吸收到生物质中。因此，这项实验的结果将增加我们对未来大气中植物生产力的理解，植物如何改变大气中气体的水平，并有助于更准确地确定树木和生态系统的碳储存潜力。

The objectives of this study are to determine the single and combined effects of several atmospheric gases likely to increase dramatically in the next century [carbon dioxide (CO2), nitrogen dioxide (NO2), and ozone (O3)] on the leaf physiology and overall growth of sugar maple, eastern hemlock, trembling aspen, and red oak seedlings. The trees are fumigated with elevated (40ppb) or ambient NO2, elevated (560ppm) or ambient CO2, elevated (100 ppb) or ambient O3, and grown in native soil with or without additional soil fertilization. Seedling growth and leaf physiological performance (e.g., photosynthesis, stomatal conductance) will be measured continuously and, at the end of the experiment, total growth of each species will be measured and differences attributed to the exposure to pollution fumigation.Human activities have induced changes in the chemical composition of the atmosphere: the concentrations of CO2, NO2, and O3 have increased and are expected to continue increasing in the future. Plants are both impacted by these gases by altering physiological processes and have the ability to remove gases from the atmosphere and, in some cases, incorporate the carbon and nitrogen from these gases into biomass. Therefore, results from this experiment will increase our understanding of plant productivity in a future atmosphere, how plants may alter the level of gases in the atmosphere, and help to generate a more accurate determination of the carbon-storage potential of trees and ecosystems.