Research

Modern climate change and the biosphere

I am interested in looking at changes in the carbon cycle, from atmospheric CO2 concentrations, sources, and sinks, through plant tissues, soil organic matter, and carbonate nodules. Given the direct link between water prevalence and a number of these products (plant productivity, formation of pedogenic carbonates, O-horizon development) I am also interested in how water availability comes into play. To look at these, I have been working with carbon isotope values of bulk leaf tissue of modern, historical and fossil leaves as well as bulk soil organic matter. Isotope fractionation and water use efficiency are directly linked by stomata (leaf pores which let in atmospheric carbon and let out water vapor), so changes in leaf stable isotope ecology of plants as well as subsequent soil organic matter can shed light on changes in plant physiology in relation to changes in atmospheric CO2. I am in the process of expanding to use Deuterium isotopes of bulk tissue and long chain hydrocarbons to more exactly estimate leaf water availability. I have focused on collecting modern and historical specimens from an expanse of parks and forests across the United States and China as well as from collections facilities such as herbaria and museums. My focus is on woody plants, especially conifers (Thuja, Pinus and Platycladus) with concurrent angiosperms (Populus) that are prevalent throughout the Cenozoic and late Mesozoic fossil record, and on soils.

Ancient hothouse environments

I am working with organic isotopes in southwest Wyoming (the greater Green River Basin) on Eocene floodplain and lacustrine sediments to look at how the carbon and water cycle functioned during extended warm periods in the past. This includes looking at carbon isotope variability across a landscape (>2km of collected paleosols) as well as looking at changes in organic isotope values preserved in bulk organic matter within sediments, fossils and charcoal over several million years within a well-preserved section that covers the Early Eocene Climatic Optimum.

My field sites include but are not limited to:

  • US Rocky Mountains/American Southwest
  • US and Canada Pacific Northwest
  • US and Canada Great Lakes Region
  • Central China (Sichuan region)