WIDTH AND OXYGEN ISOTOPE COMPOSITION OF TREE RINGS AS A PROXY FOR RECENT SOUTHERN INDIANA CLIMATE

As anthropogenic climate change becomes a topic of increasing scientific discussion and political debate, accurate paleoclimate records acquires further significance. Much of the work to date has been focused on areas of low population and high climate sensitivity (i.e. high latitude and altitude regions) to avoid complicating signals such as changing land use. Meanwhile, less climate sensitive, high population regions (e.g. Midwest U.S.) have been partly neglected. Locating archives of past climates in such areas can be difficult, but not impossible.

Trees contain many proxies for past climate. Annual outward growth produces internal rings that are distinguishable from the previous year and contain important physical and chemical information. The rings provide many clues that help uncover the history of past conditions --- ring width, ring density, and chemical information including stable isotopes of oxygen, hydrogen, and carbon--- each of which are a consequence of climate parameters such as precipitation, humidity, and temperature.

In the spring of 2004, a collaborative effort between IU geologists and ISU geographers was initiated. Cores from 33 tree and 9 cross sections from 2 species (Quercas robur and Lirodendron tulipifera) were colleceted at the Lilly-Dickey Preserve. The site was chosen for its relatively abundant old growth for the region, enabling the record to be extended to the past 120 years. Paleoclimate analysis is underway using ring thickness and d¹⁸O of cellulose.