( A Duke University study has found that ...)High carbon dioxide levels spur Southern pines to grow more needles

A Duke University study has found that maturing stands of pines exposed to the higher levels of carbon dioxide expected by mid-century produce more needles than those absorbing today's levels of the gas, even under drought conditions. However, the study also found that lack of soil nutrients may impose limitations in many forests.

Duke graduate student Heather McCarthy will describe results she obtained from a futuristic open-air experimental forest site at 8 a.m. Eastern Time on Thursday, Aug. 11, 2005 during the 2005 annual meeting of the Ecological Society of America in Montreal.

Her work was supported by the United States Department of Energy and the U.S. Department of Agriculture's Forest Service.

McCarthy, who has just competed her fifth year as a doctoral student in environmental studies at Duke's Nicholas School of the Environment and Earth Sciences, analyzed 10 years of pine needle data collected at the Free-Air Carbon Dioxide Enrichment (FACE) experiment in Duke Forest, a near-campus research reserve.

At FACE, some stands of fast-growing loblolly lines are being exposed to the higher levels of CO2 expected by 2050 due to human activities such as fossil fuel burning. Other stands are left as untreated controls for comparison. The elevated carbon dioxide is delivered from rings of towers in the open air setting of a Southern forest ecosystem.

McCarthy found that, over the most recent six years of the FACE experiment, the pines receiving elevated CO2 had on average about 17 percent more needles than untreated pines. Higher needle percentages in trees receiving the gas were recorded even during years when forest soils were driest -- when both treated and untreated trees suffered dryness-related needle losses and less leaf growth.

"This would imply that, even under drought conditions, there would probably be an enhancement with elevated CO2," McCarthy said in an interview.

Her analysis singled out the last
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Source:Duke University

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