CHESTNUT TREES: A new study suggests the fast-growing American chestnut tree soaks up a steady diet of carbon dioxide.
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The American chestnut tree, which towered over eastern U.S. forests before succumbing to a deadly fungus in the early 20th century, appears to be an excellent sponge for greenhouse gases, according to a new study.

If scientists can develop a fungus-resistant version of the tree, the chestnut could play a key role in the battle against climate change, Purdue University scientists say.

"Maintaining or increasing forest cover has been identified as an important way to slow climate change," said Douglass Jacobs, whose chestnut tree study appears in the June issue of Forest Ecology and Management.

In a study conducted at four sites in southwestern Wisconsin, the American chestnut grew much faster and larger than the black walnut and northern red oak, allowing it to soak up more carbon dioxide, the study found. The tree's higher carbon capacity makes it an ideal candidate for forest restoration projects and carbon offset schemes, particularly on marginal farmland in the Midwest.

"Generally, the faster a tree grows, the more carbon it is able to sequester," Jacobs said. "And when these trees are harvested and processed, the carbon can be stored in the hardwood products for decades, maybe longer."

The chestnut also compared favorably when cross-referenced to studies of quaking aspen, red pine and white pine.

The trees eventually absorb the same amount of carbon, but the fast-growing chestnut can store more carbon in a shorter amount of time, Jacobs said. The tree was found to carry up to three times the biomass of the others at various points in its growth cycle.

Moreover, the chestnut is a prime species for furniture and housing products, which allow it to store carbon for extended periods after harvest. By contrast, carbon stored in newsprint is stored for an average of six months, said Bryan Burhans, CEO of the American Chestnut Foundation in Asheville, N.C.

"It's simply taking atmospheric carbon and turning it into a compound that is stored in the tree," said Burhans, a biologist who was not part of the Purdue study. Chestnuts that are not harvested, he said, can live between 250 years and 300 years, compared to an oak's average lifespan of 100 years to 150 years.

Worldwide, trees store a sixth of the CO2 emitted each year, but they could be managed to store much more, scientists say.

A sweeping climate and energy bill passed by the House last week would create opportunities for investing in reforestation projects to offset carbon emissions. The legislation sponsored by Democrats Henry Waxman of California and Ed Markey of Massachusetts requires half of the 2 billion tons of carbon offsets allowed each year to be purchased in the United States.