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

University Of Washington, Seattle WA

Investigators

Abstract

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.