Network tracking forest’s CO2 transfer

EDITORS: Color slides of the AmeriFlux tower currently in operation at Oak Ridge National Laboratory are available on request.

ANN ARBOR—A 100-year-old stand of trees at the University of Michigan Biological Station will soon begin helping scientists learn more about global climate change and its impact on northern Michigan forests.

The U-M’s 10,000-acre Biological Station, located near Pellston, Mich., is one of 24 North American sites selected by the U.S. Department of Energy to be part of its AmeriFlux network. State-of-the-art sensing instruments located on towers at these sites will measure the amount of carbon dioxide exchanged between the local ecosystem and the atmosphere. Instrument readings will be recorded about 10 times per second, 24 hours a day for several years.

“Legislators and policy makers want scientists to predict what’s going to happen in the future as people continue to burn coal, oil and other fossil fuels which pump more carbon dioxide into the atmosphere,” said James A. Teeri, director of the Biological Station and U-M professor of biology. “No one can make valid predictions now, because we don’t know enough about how carbon dioxide cycles through the global ecosystem. AmeriFlux will begin to give us the information we need to answer these important questions.”

Scientists know that the concentration of carbon dioxide in the atmosphere has climbed from 280 parts per million (ppm) in 1750 to today’s level of about 360 ppm. The level of CO2 in the atmosphere started to increase when people began widespread burning of fossil fuels during the Industrial Revolution. Most scientists believe that the 1 degree C. rise in average global temperature recorded over this same time period has been caused, in part, by carbon dioxide and other “greenhouse gases” from fossil fuel emissions. These greenhouse gases trap heat in Earth’s atmosphere and prevent it from radiating back out into space.

Scientists also know that growing plants take in carbon dioxide during photosynthesis. What no one knows, however, is how much CO2 is stored in the world’s plants and soils, how much additional storage capacity is available and what will happen to all that carbon dioxide when plants die and decay.

“The ability to make direct, instantaneous measurements of CO2 exchange between the forest and atmosphere is the first step toward answering these questions,” Teeri said. “It will allow us to see how CO2 exchange is affected by changes in precipitation, temperature, land use, carbon dioxide concentration and levels of air pollution on a daily basis.”

At the U-M Biological Station, construction of a 153-foot AmeriFlux tower will begin this May in the middle of an undisturbed stand of hardwoods—mostly aspen, red maple and red oak with some white pine. Sensing instruments will be installed at various levels on the tower from above the forest canopy to ground level. Beginning in July 1998, scientists at the Biological Station will begin collecting data from the instruments and recording the data on a computer system.

“The Biological Station was selected for the network because it is located on the boundary between the hardwood forests and the boreal [spruce] forests of North America,” Teeri said. “As climate change occurs in the future, there may well be some major biological responses occurring at this forest boundary.” Currently there are about 24 AmeriFlux towers in operation or under construction in North America (map available on request), and Teeri said the network is likely to expand in the next few years. Towers currently in operation are located at Harvard Forest in Massachusetts; Manitoba, Canada; northern Alaska; the Oak Ridge National Laboratory in Tennessee and several other locations. A multi-site data archive to store and analyze information from all AmeriFlux sites will be developed and managed by the Carbon Dioxide Information and Analysis Center (CDIAC) at the Oak Ridge National Laboratory.

Research support for the AmeriFlux network comes from the U.S. Department of Energy, Office of Biological and Environmental Research (National Institute for Global Environmental Change and Terrestrial Carbon Processes) and other sources—including NSF, NOAA, USDA and NASA. For more information, see the AmeriFlux website at http://www.esd.ornl.gov/programs/NIGEC/.

Biological StationU.S. Department of EnergyJames A. TeeriCarbon Dioxide Information and Analysis CenterOffice of Biological and Environmental ResearchU-M News and Information ServicesUniversity of Michigan