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Southern Research Station Scientists Contribute to Understanding the Relationship Between Soil Fertility and Carbon Sequestration in North Carolina
Asheville,NC -- The results of a study discussed in an article in the May 24 research journal Nature indicate that elevated levels of atmospheric carbon dioxide may have more limited effect on forest growth than previously expected. The article describes experiments conducted at two sites in central North Carolina, one at Duke Forest near Raleigh and one at the USDA Forest Service's Southeast Tree Research and Education Site in Scotland County, NC. While many short-term studies have shown atmospheric carbon dioxide (a "greenhouse" gas) increases tree growth, the experiments reported in Nature showed that without additional nutrients, initial growth increases of mature loblolly pine trees leveled off after the first three years of exposure. In addition to nutrient limitations, growth responses were also sensitive to the availability of soil moisture. The presence of elevated levels of carbon dioxide alone, which is occurring due to global industrialization and land use changes, may not result in a long-term increase in the rate of tree growth. However, the results also suggest that forest fertilization, already a practice in Southern pine plantations, might become even more beneficial in a high carbon dioxide world.
The study is part of the effort to understand the relationship between forests, which often are limited to sites with low nutrient soils, and carbon sequestration, in order to estimate current and future global carbon budgets. Lead author of the article is Ram Oren, of the School of the Environment, Duke University; the ten co-authors include three Forest Service research scientists from the Southern Research Station: Kurt Johnsen and Chris Maier of Research Triangle Park, and Steve McNulty of Raleigh. The researchers determined that along a gradient of decreasing site fertility, nutrient amendments (nitrogen) would become increasingly necessary if forested ecosystems are to help reduce the rate at which atmospheric carbon dioxide concentrations increase.
The article appears in Nature, titled ÂSoil Fertility Limits Carbon Sequestration by Forest Ecosystems in CO2-enriched Atmosphere. Authors are Ram Oren, School of the Environment, Duke University; David Ellsworth, School of Natural Resources, University of Michigan in Ann Arbor and the Brookhaven National Laboratory in Upton, N.Y.; Kurt Johnsen and Chris Maier, USDA Forest Service Southern Research Station in Research Triangle Park, NC; Nathan Phillips, Department of Geography, Boston University; Karina Schafer, Heather McCarthy, Brent Ewers and Gabriel Katul, Duke; Steven McNulty, USDA Forest Service Southern Global Climate Change Program, Raleigh, NC.; Brent Ewers, University of Wisconsin at Madison; and George Hendrey of Brookhaven, who designed and engineered the Duke Forest site of the experiment.
The study was collaboratively funded by the USDA Forest Service; the US Department of Energy Office of Health and Environmental Research; the National Institute for Global Environmental Change, Southeast Regional Center at the University of Alabama; and the National Science FoundationÂs Multi-User Instrument Program.
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