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

这项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、铁杉、颤杨和红橡树幼苗的叶片生理和整体生长的单一和综合影响。这些树木用高浓度(40ppb)或周围NO2、高浓度(560ppm)或周围二氧化碳、高浓度(100 Ppb)或周围臭氧进行熏蒸，并在有或没有额外土壤肥料的情况下生长在原生土壤中。将连续测量幼苗生长和叶片的生理表现(如光合作用、气孔导度)，并在实验结束时测量每个物种的总生长，并将差异归因于污染熏蒸的暴露。人类活动已导致大气化学成分的变化：二氧化碳、NO2和臭氧的浓度已经增加，预计未来还将继续增加。植物通过改变生理过程受到这些气体的影响，并有能力从大气中去除气体，在某些情况下，将这些气体中的碳和氮并入生物质中。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了解，了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.