DISSERTATION RESEARCH: Phytolith Undulation Index: Developing a new proxy for tracking habitat openness in the Eocene-Miocene of Gran Barranca, Argentina

这项研究的目的是开发一种新的方法来确定植被是开放的（例如草原）还是封闭的（森林）在化石记录中从二氧化硅填充的植物细胞的形状称为植硅体。 叶子表皮细胞的形状取决于叶子在发育时接受多少阳光。 生长在荫蔽森林地面上的植物比生长在阳光充足的植物有更多的波状表皮细胞。 一些植物的表皮细胞在化石记录中以硅铸件的形式保存下来。 这项研究将开发一种方法来计算植被开放度（叶面积指数-LAI）从波动的表皮植硅体是如何，通过检查从现代土壤中收集的植硅体从开放和封闭的植被（稀树草原多层雨林）。我们将利用这种数学关系从化石植物岩中解释数百万年前植被的开放程度。具体来说，我们将研究在始新世-中新世（4200 - 1800万年前）期间，阿根廷巴塔哥尼亚的植被开放度如何随着全球气候的变化和频繁的火山爆发而变化。我们还将比较我们的植被开放记录与化石哺乳动物的记录，以测试食草动物是否通过牙齿的进化变化（增加冠高）来适应日益开放的景观。叶面积指数测量在现代生态学研究和气候模拟中具有重要意义。 有一种从化石记录中估计LAI的方法可以让科学家了解古代植被的结构，并允许现代和古代植被之间进行更直接的比较，这对于研究环境如何随时间变化至关重要。 这项研究为本科生提供了参与研究的机会，为教育和研究提供了在线资源，并将通过博物馆展览向公众开放。

This study aims to develop a new method for determining whether vegetation was open (for example steppe) or closed (forest) in the fossil record from the shape of silica-filled plant cells called phytoliths. The shape of epidermal cells in leaves depends on how much sunlight a leaf receives when it develops. Plants growing on shaded forest floors have more undulated, or wavy epidermal cells than plants growing in full sun. Epidermal cells from some plants are preserved as silica casts in the fossil record. This study will develop a way to calculate mathematically vegetation openness (measured as Leaf Area Index-LAI) from how undulated epidermal phytoliths are, by examining phytoliths collected from modern soils from open and closed vegetation (savanna to multi-tiered rainforest). We will use this mathematical relationship to interpret from fossil phytoliths how open vegetation was millions of years ago. Specifically, we will look at how vegetation openness changed with shifts in global climate and frequent volcanic eruptions in Patagonia, Argentina during the Eocene-Miocene (42-18 million years ago). We will also compare our record of vegetation openness with the record of fossil mammals to test whether plant-eating animals were adapting to increasingly open landscapes through evolutionary changes in their teeth (increasing crown height). LAI measurements are important in modern ecological studies and in climate modeling. Having a method for estimating LAI from the fossil record allows scientists to understand the structure of ancient vegetation, and permits more direct comparisons between modern and ancient vegetation, which is vital for investigating how environments have changed over time. This study offers opportunities for undergraduates to become involved in research, provides online resources for education and research and will be accessible for the public through museum exhibitions.