OAK RIDGE, Tenn. -- Researchers at the Department of Energy's (DOE) Oak Ridge National Laboratory (ORNL) are simulating the environment of the future by releasing controlled amounts of carbon dioxide into the atmosphere over a small patch of sweetgum trees.
The simulation experiment is confined to a small area on the ORNL Reservation and is designed to answer one of the trickiest questions in our understanding of global warming: just how will forests and ecosystems react to increased carbon dioxide (CO2) in the environment?
This small-scale experiment is not an environmental risk because CO2 is a naturally occurring gas in the atmosphere, and elevated levels are within ranges beneficial to plants.
Atmospheric concentrations of CO2 and other gases that influence the Earth's climate through the "greenhouse effect" are increasing. According to the latest report of the Intergovernmental Panel on Climate Change, the balance of evidence now suggests a discernible human influence on global climate.
Nevertheless, many uncertainties remain, particularly about the role that forests play in taking up and storing excess carbon dioxide produced by the burning of fossil fuels.
Researchers have learned that many of the important responses to increased CO2 occur below ground, but they have never before been able to test their ideas in a forest -- until now.
The National Science Foundation has awarded a three-year, $1.2 million grant to a team of laboratory researchers to conduct free-air CO2 enrichment (FACE) studies of a closed-canopy deciduous forest, an extension of earlier studies that examined the responses of individual trees in growth chambers.
"Over the past 15 years we have learned a great deal about how individual small trees respond to increased CO2 concentrations," said Rich Norby, leader of the project. "It is now time to make the critical leap to measuring the response of a complete forest ecosystem."
Archaeologists several hundred years from now may wonder if they have stumbled upon a 20th century Stonehenge on the Oak Ridge Reservation. In the middle of a sweetgum stand along the Clinch River, aluminum towers have been built on concrete slabs arranged in three circles of 12, with each circle measuring 25 meters in diameter.
Rising above the forest canopy, the towers are part of the facility where the researchers will study the effects of ecological and global change.
When the facility is completed, CO2 will be released from the towers to enrich the atmosphere within the circles, exposing the sweetgum trees to conditions that are expected to prevail in the next century. By noting the changes in the trees and soil, researchers from ORNL's Environmental Sciences Division will gain insight into the complex biological and physical interactions that govern how a forest ecosystem responds to changes in the atmosphere.
DOE considers these FACE facilities to be critical in addressing the challenge of global change.
The study will provide important data for testing computer models of forest response. Physiological responses of the trees, including photosynthesis, respiration, transpiration and biochemical changes, will also be assessed.
Development of the FACE facility has been supported by the ORNL Director's Research and Development Fund. Its operation will be supported by DOE's Office of Health and Environmental Research and is an important DOE contribution to the U.S. Global Change Research Program.
The ORNL researchers expect the new facility to attract many colleagues from around the world. In fact, researchers from several institutions, including the Desert Research Institute in Reno, Nev., the University of Colorado, University of South Carolina, University of Illinois, Texas Tech University, West Virginia University and Kalamazoo College, have already expressed interest in conducting research at the facility.
ORNL, one of DOE's multiprogram national research and development facilities, is managed by Lockheed Martin Energy Research Corporation.
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