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

本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。具体来说，该项目将比较生长在火山柱路径上的植物与生长在该岛其他地区的植物的气孔指数（气孔数量与上皮细胞数量的比值）和叶片的碳同位素组成。本研究将作为一个假设的检验，即在玄武岩火山喷发期间释放的SO2对大气的负荷构成了对大气的重大干扰，导致光合作用期间叶片气孔数量和叶片碳分馏的变化。这一假设挑战了目前的范式，即所有气孔指数的变化都可以通过大气CO2水平的变化来解释。这项为期一年的研究的统计显著结果将允许设计一项严格的多年实验研究，以量化二氧化硫暴露的影响。这项研究的更广泛的意义涉及到生物灭绝的机制。洪水玄武岩的大规模喷发与几次大灭绝事件有关。该项目将有助于确定火山成因二氧化硫是否会在植被上留下可识别的记录，这些记录可能会从化石记录中识别出来。此外，本提案为本科生创造了研究经验，他们将直接参与数据的收集和评估。

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.