The circular areas in the photo are the FACE experiment test plots. Researchers pump in elevted levels of ozone and carbon dioxide to determine the effects on trees. The trees of the future may be much more vulnerable to a variety of pests, say scientists studying greenhouse gases in northern Wisconsin forests. Their work was published this year in the journal Nature. Researchers in the Aspen FACE (Free-Air Carbon dioxide Enrichment) Experiment, led by scientists at Michigan Tech and the U.S. Forest Service, have been measuring the effects of elevated levels two greenhouse gases, carbon dioxide and ozone, on aspen forest ecosystems. While the trees seem to do relatively well in a carbon dioxide-rich atmosphere, ozone is another story. Trees (Populous tremuloides—or trembling aspen) growing in an ozone-enriched atmosphere have been hit much harder by their traditional enemies: forest tent caterpillars, aphids and the rust fungus Melampsora. “This has been a surprise,” said FACE director David Karnosky of Michigan Tech’s School of Forest Resources and Environmental Science. “Our experiment was never meant to look at pest occurrence. But it became obvious that the greenhouse gases were affecting the abundance of pests.” Aphids thrive in high-ozone air and populations of the tiny insects’ traditional predators—such as ladybugs and spiders—plummeted. The number of aphids increased about five-fold in plots with elevated ozone, while the number of aphid predators was cut in half. In plots with elevated levels of both carbon dioxide and ozone, the aphid population tripled, while the number of natural enemies increased slightly, mitigating the aphids’ effect on the aspen. Studies have shed some light on why the aspen growing in ozone-rich air were turning into so much bug salad: their leaves seem to be undergoing fundamental changes. “Ozone alters the surface waxes,” said Kevin Percy, a research scientist with Natural Resources Canada—Canadian Forest Service. Melampsora infection in the control and CO2-enriched plots was about the same, but increased about 400 percent in the O3 plots and doubled in the plots with extra CO2 and O3. The number of forest tent caterpillars increased by about one-third in the O3 plots and actually decreased slightly in the CO2 plots and the plots with extra CO2 and ozone. The Aspen FACE Experiment, which involves 11 institutions and 28 researchers, is funded jointly by the Department of Energy’s Office of Biological and Environmental Research, the National Science Foundation, the U.S. Forest Service Global Change Program, the U.S. Forest Service North Central Research Station, Michigan Tech, the USDA National Research Initiative Program, Brookhaven National Laboratory and Natural Resources Canada. The FACE system was designed by George Hendrey and his Brookhaven National Lab team. Professor Kurt Pregitzer, another FACE Experiment researcher from Michigan Tech, calls Aspen FACE “a window into the future.” “We’re beginning to understand how the changing atmosphere of the Earth is going to impact forests and the interactions that control the growth of trees, the cycling of energy and nutrients, and the movement of water through ecosystems,” he said. “This particular paper points out how important understanding the interactions among plants and insects are in controlling forest growth and forest health. “We have a lot to learn.” Photo (right): Kurt Pregitzer participates in the FACE project and is an expert in the cycling of carbon as it relates to below-ground processes. Ozone | Times Square | Concrete | Archaeologists | Computing | Manipulating Light | SmartZone | Enterprise Program Michigan Tech Research 2003 Michigan Technological University 1400 Townsend Drive Houghton, MI 49931-1295 906-487-3043 Fax: 906-487-2245