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Forests need good soil to sequester more carbon

Forests need good soil to sequester more carbon

Forests need good soil to sequester more carbon
December 13, 2006

Soil nutrition is key to helping forests absorb more carbon under elevated CO2 conditions according to new research by scientists with the USDA Forest Service and Duke University.

“The researchers found that trees can only increase wood growth from elevated CO2 if there is enough leaf area to support that growth,” reported the Southern Research Station of the USDA Forest Service in a statement. “Leaf area, in turn, is limited by soil nutrition; without adequate soil nutrition, trees respond to elevated CO2 by transferring carbon below ground, then recycling it back to the atmospheric through respiration.”

Aerial view of free-air carbon dioxide enrichment (FACE) rings at Duke Forest, Durham, NC. Credit: Will Owens.

“With sufficient soil nutrition, forests increase their ability to tie up, or sequester carbon in woody biomass under increasing atmospheric CO2 concentrations,” said Kurt Johnsen, SRS researcher involved in the project. “With lower soil nutrition, forests still sequester carbon, but cannot take full advantage increasing CO2 levels. Due to land use history, many forests are deficient in soil nutrition, but forest management — including fertilizing with nitrogen — can greatly increase growth rate and wood growth responses to elevated atmospheric CO2.”

The results, published in two papers in The Proceedings of the National Academy of Science (PNAS), will help researchers better understand how trees respond to increasing atmospheric concentrations of carbon dioxide. Atmospheric carbon dioxide levels are presently at their highest levels in at least 650,000 years.

“Forests play a critical part in sequestering carbon, and may play a role in mitigating the elevated levels of carbon dioxide associated with climate change,” says Johnsen. “To predict how much forests can sequester, we need accurate ways to predict what happens to carbon within forest systems and how this partitioning is affected by environmental conditions.”

This article is based on a news release from the USDA Forest Service.

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