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Pine forest thrives on high-CO2 diet.

A forest of the future grows in North Carolina. By pumping carbon dioxide (CO2 ) into a stand of loblolly pines, a team of ecologists is testing how mature trees will react to the increase in atmospheric greenhouse gases expected during the next century.

Results collected last summer show that the gassed-up pines boosted their rate of photosynthesis by 65 percent, compared to a nearby control plot, says David S. Ellsworth of Brookhaven National Laboratory in Upton, N.Y. Ellsworth reported the findings last week at a meeting of the Ecological Society of America in Snowbird, Utah.

The logistically complex study--which requires large towers for pumping the CO2 into the foliage--is the first to examine how mature trees in a forest will respond to air enriched with the gas. Previous experiments, although carried out on a much smaller scale, have shown similar increases in photosynthetic rate among small trees and crop plants growing in CO2 -enhanced air.

In the study, scientists from Brookhaven and from Duke University in Durham, N.C., boosted CO2 concentrations to 550 parts per million throughout a 0.4 hectare forest plot. Air today typically contains 355 parts per million, whereas CO2 values prior to the Industrial Revolution stood at 280 parts per million.

The scientists ran the experiment for just one season and thus did not test whether rates of photosynthesis for the forest would remain elevated under prolonged exposure to CO2. Previous studies have shown that certain plants acclimatize to the higher concentrations of the gas: Within 3 years, their photosynthetic rates fall back to those of control plants. In 1996, Ellsworth and his colleagues will start a long-term experiment to determine how the forest responds over 3 to 5 years.

The new results seem to suggest that pine forests may thrive in the atmosphere of the future. But Fakhri Bazzaz of Harvard University notes that the buildup of CO2 will produce both winners and losers in natural ecosystems.

Although most plants grow better with extra CO2, the ones most sensitive to the gas will tend to drive out the less responsive types, thereby winnowing the number of species present in forests. "The production of biomass, of plant material, will probably increase about 10 percent, but the biological diversity will be diminished," says Bazzaz.
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Title Annotation:carbon dioxide
Author:Monastersky, Richard
Publication:Science News
Article Type:Brief Article
Date:Aug 12, 1995
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