The study, performed by researchers at the Department of Energy's Oak Ridge National Laboratory and 10 other institutions in the United States and Europe, revealed a strong relationship between productivity of forest plots in the current atmosphere and productivity in plots experimentally enriched with carbon dioxide.

"The median response indicated a 23 percent increase in productivity in the future atmosphere," said ORNL's Rich Norby, lead author of the paper to be published Dec. 13 in the Proceedings of the National Academy of Sciences. "What was especially surprising to the research team was the consistency of the response across a wide range of productivity."

Researchers analyzed data from four experiments in which young forest stands were exposed for multiple years to an atmosphere with a carbon dioxide concentration predicted to occur in the middle of this century. The experiments were conducted in a deciduous forest in Tennessee, a pine forest in North Carolina, a young hardwood stand in Wisconsin and a high-productivity poplar plantation in Italy.

The team calculated net primary productivity the annual fixation of carbon by green plants into organic matter for each of the sites from data on wood, leaf and fine-root production. The results proved surprising.

"When we got together to analyze these data, we expected to spend our time explaining the differences between sites," said Norby, a member of ORNL's Environmental Sciences Division. "We were really surprised and excited when all of the data fell neatly onto a single line."

More detailed analysis of the data revealed the mechanisms of the forest productivity response. In forest stands with a relatively low amount of leaf area, the respo
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Contact: Ron Walli
wallira@ornl.gov
865-576-0226
DOE/Oak Ridge National Laboratory
8-Dec-2005