Research in the Ward Lab focuses on understanding how changes in atmospheric carbon dioxide concentrations affect plant physiology. My part of this research looks specifically at how changes in atmospheric CO₂ concentrations since the Last Glacial Maximum have affect tree physiology. To address this, I am comparing juniper fossils from the Rancho La Brea tar pits in southern California and kauri fossils from peat bogs in New Zealand to their modern counterparts currently growing in each area. By studying plants that lived in these past climates, we can develop a clearer understanding of how plants responded to past global changes in the environment that were driven by natural cycles. This will also allow us to improve our predictions of how plants and ecosystems will respond to future global changes in climate variables caused by human activity.      Using stable isotope techniques, we can compare the ratio of intercellular to atmospheric CO₂ concentration (called c_i /c_a) of ice age and modern trees to see how these values have responded to climate changes since the last glaciation. Changes in c_i /c_a reflect changes in stomatal regulation and photosynthetic capacity. Lower intercellular CO₂ concentrations (c_i) would predict lower levels of growth in ice age trees compared to modern trees. Our paleo tree samples come from two locations. Juniper fossils have been donated by the Page Museum of Natural History curator Dr. John Harris and range in age from 15-50,000 years old. Kauri fossils have been provided by Ancientwood, Ltd. president Robert Tiesberg and range in age from 45-55,000 years old (or perhaps older, as these dates push the limits of ¹⁴C dating). In both locations, ancient specimens are well preserved, as can be seen in the photos on this page.

     In addition to the ice age tree project, we also have a collection of Pleistocene Era packrat middens. This collection contains over 350 specimens, which range from the northern United States to southern Mexico and Baja California. The remnant plant and animal material contained within the middens will provide insight into variation in the environment (such as changing rainfall and levels of atmospheric carbon dioxide) and its effect on plants throughout the Pleistocene. Using this collection, we can also address other research topics, including the evolution and spread of C₄ grasses, the variation in diets of Pleistocene Era grazing mammals (such as bison), and even perhaps the prevalence of parasites and disease on packrats.