When compared to grassy areas, Jackson's research group found the extra carbon saved in the wood of encroaching trees and shrubs at the wettest locations may be more than offset by the carbon lost from the underlying soil.

They made their deductions at six experimental field sites from eastern Texas to western New Mexico, where original species of grasses and invading species of woody vegetation could be directly compared.

"Assessments relying on carbon stored from woody plant invasions to balance emissions may therefore be incorrect," Jackson and four co-authors wrote in the Aug 8, 2002 edition of the journal Nature.

Jackson, an associate professor at Duke's Biology department and Nicholas School of the Environment and Earth Sciences, referred to an article in the June 22, 2001 issue of Science.

That Science report highlighted "woody encroachment" as one of two important factors for its estimate that the atmospheric carbon "sink" amounts of former carbon dioxide gas stored away in various natural repositories had been "relatively stable" in the United States for more than a decade.

Jackson and his colleagues set out to examine the carbon sink associated with woody plant encroachment in more detail.

Many scientists consider carbon dioxide from human activities a major contributor to global warming. Policy makers have hoped that growing more trees would help ameliorate the problem.

That's because some of the carbon from the carbon dioxide is incorporated into the plant material, where it remains until the plants die and decay. In the case of the wood in trees, that carbon may thus remain sequestered for centuries. In the case of
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Contact: Monte Basgall
monte.basgall@duke.edu
919-681-8057
Duke University
8-Aug-2002