Effects of Volcanogenic SO2 on Leaf Stomata and Isotopic Composition of Vegetation on Hawaii

这项拟议研究的目的是详细研究夏威夷基拉韦厄火山持续喷发所释放的二氧化硫对植被的影响。具体地说，该项目将比较生长在火山羽流路径上的植物与岛上其他地区植物的气孔指数(由气孔数量与上皮细胞数量之比得出的比率)和叶片的碳同位素组成。这项研究将作为对这一假设的检验，即玄武岩火山喷发期间排放的二氧化硫对大气的负荷构成了对大气的重大干扰，导致叶片气孔数量和光合作用期间叶片对碳的分馏发生变化。这一假设挑战了当前的范式，即所有气孔指数的变化都可以用大气二氧化碳水平的变化来解释。这项为期一年的研究具有统计学意义的结果将允许设计一项严谨的多年实验研究，以量化二氧化硫暴露的影响。这项研究的更广泛影响与生物灭绝的机制有关。洪水玄武岩的大规模喷发被认为与几次大规模灭绝有关。该项目将有助于确定火山成因的二氧化硫是否在植物上留下了可识别的记录，可以从化石记录中识别出来。此外，这项建议还为直接参与数据收集和评估的本科生创造了研究经验。

It is the purpose of the proposed research to examine in detail the effects on vegetation of SO2 released by the ongoing eruption of Kilauea volcano on Hawaii. Specifically, this project will compare the stomatal index (a ratio derived from the number of stomata compared to the number of epithelial cells) and the carbon isotope composition of leaves on plants growing in the path of the volcanic plume with plants growing in other areas of the island. This research will serve as a test of the hypothesis that loading of the atmosphere by SO2 emitted during basaltic volcanic eruptions constitutes a significant disturbance of the atmosphere that causes changes in the number of leaf stomata and in the fractionation of carbon by leaves during photosynthesis. This hypothesis challenges the current paradigm that all variations in stomatal indices can be explained by variations in atmospheric CO2 levels. Statistically significant results of this one-year study will permit design of a rigorous multi-year experimental study to quantify the effects of SO2 exposure.The broader implications of this research relate to mechanisms of biotic extinction. Large eruptions of flood basalts have been linked to several episodes of mass extinction. This project will help to determine if volcanogenic SO2 leaves an identifiable record on vegetation that may be identified from the fossil record. Additionally, this proposal creates research experiences for undergraduate students who will be involved directly in the collection and evaluation of the data.