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Scientists to Assess Effects of Ozone Carbon Dioxide on Trees A worker tests the operation of a carbon dioxide dispersal system near Rhinelander, Wisconsin.

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multidisciplinary team of 17 scientists is building an experimental facility near Rhinelander, Wisconsin, to test the effects of combined ozone and carbon dioxide on forest stands.    "The rise in atmospheric carbon dioxide concentrations is expected to have profound effects on forest vegetation, including changes in the responses of trees to environmental stresses," says project leader David Karnosky, a geneticist in the School of Forestry and Wood Products at Michigan Technological University. Karnosky, along with Jud Isebrands of the Forest Service, George Hendrey of the Brookhaven National Laboratory, and Kurt Pregitzer of Michigan Tech, comprise a steering committee that is spearheading the project. Scientists from the University of Michigan, University of Wisconsin, and University of Minnesota-Duluth are also participating in the study.    Karnosky, a Michigan SAF member, says that in the future many forests will be exposed to increased atmospheric carbon dioxide in conjunction with other pollutants. One of the most important of these is tropospheric ozone, which is increasing globally at a rate of one to two percent a year.    "While it is known that increasing carbon dioxide increases plant growth, elevated ozone levels have just the opposite effect, decreasing photosynthesis and thereby limiting plant growth," he say. "That's why it's so important for us to find out how trees will respond to increasing amounts of both of these elements in the natural environment."    Until now, the majority of experiments with carbon dioxide and/or ozone have been short-term studies conducted in controlled indoor chambers, greenhouses, or open-top chambers in the field, according to Karnosky.    "There is a recognized urgent need for

long-term, forest community-level carbon dioxide and ozone exposure studies under more realistic conditions, and a more holistic approach that includes integrated studies of forest productivity and community dynamics," says Pregitzer. "The system we're constructing at Rhinelander, Wisconsin, offers an opportunity to study such relationships."    The "system" under construction at Rhinelander will be the largest free air carbon dioxide exposure system in the world. It will include 12 ring-shaped test plots 30 meters in diameter. Each ring will be planted with aspen throughout, with one-third of each ring having maple mixed with the aspen and one-third of each ring having maple mixed with the aspen and one-third having birch mixed with the aspen. More information is needed on these species because aspen, birch, and maple make up about 70 percent of the pulpwood harvested in the Great Lakes states. Carbon dioxide and ozone will be dispersed into the planted test plots through vertical vented pipes located on the upwind side of the plots. This arrangement will allow the gases to be blown into the plots in a way that will best simulate natural conditions.    The study is being funded by grants from the Department of Energy totaling more than $1 million and a $251,000 equipment grant from the National Science Foundation. The Forest Service Global Change Program has also contributed more than $400,000 to the project. For more information, contact Karnosky at (906) 487-2898; e-mail: karnosky@mtu.edu.

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