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The SPRUCE research project is spread across seven acres in a natural spruce bog in northern Minnesota. Image credit: ORNL
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The open-topped enclosures—12 meters wide and 8 meters tall—sit over a corral bed that isolates the peatland. Image credit: ORNL
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Scott Bridgham of the University of Oregon (seated) and ORNL’s Natalie Griffiths collect peat pore water samples to evaluate dissolved organic carbon losses from warming. Image credit: ORNL
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ORNL’s Jana Phillips measures surface CO2 and CH4 exchange in the back of a typical SPRUCE enclosure. Image credit: ORNL
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The SPRUCE research project is spread across seven acres in a natural spruce bog in northern Minnesota. Image credit: ORNL
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The open-topped enclosures—12 meters wide and 8 meters tall—sit over a corral bed that isolates the peatland. Image credit: ORNL
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Scott Bridgham of the University of Oregon (seated) and ORNL’s Natalie Griffiths collect peat pore water samples to evaluate dissolved organic carbon losses from warming. Image credit: ORNL
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ORNL’s Jana Phillips measures surface CO2 and CH4 exchange in the back of a typical SPRUCE enclosure. Image credit: ORNL
A natural spruce bog in northern Minnesota contains more than 10,000 years of carbon accumulated from peatlands and may answer questions about how Earth will respond to predicted warming and increases in atmospheric carbon dioxide.
About seven acres of the raised bog is home to SPRUCE, which stands for Spruce and Peatland Responses Under Climatic and Environmental Change, a new Department of Energy experiment that will allow researchers to adjust air and soil temperatures and levels of carbon dioxide.
Ten open-topped 12-meter wide, 8-meter tall transparent enclosures are the
laboratories for the experiments to assess ecological responses. The enclosures, superimposed on a belowground corral that isolates the peatland, will host measurements of microbial communities, moss populations, various higher plant types and some animal groups.
“The SPRUCE experiment continues ORNL’s involvement in environmental change studies that are conducted in the real
world at scales relevant to an ecosystem’s stature, biodiversity and biogeochemistry,” said Paul Hanson, who leads the project and is a member of ORNL's Environmental Sciences Division and Climate Change Science Institute.
With the ability to control heating of the air and soil within the chambers down to two meters, scientists hope to gain an understanding of the possible effects of projected higher temperatures on vegetation and ecosystems.
While peatlands cover about 3 percent of Earth’s land surface, they contain up to 33 percent of the global soil carbon pool. Although that carbon dioxide has been trapped in the cold oxygen-poor environment for thousands of years, warming conditions threaten to see peatlands release large amounts of carbon dioxide and methane. This occurs through a combination of enhanced decomposition and aeration of surface peats.
“SPRUCE is the first experiment to test the combination of warming and elevated carbon dioxide on carbon-rich peatland ecosystems,” said Randy Kolka, team leader and research soil scientist with the U.S. Department of Agriculture Forest Service, a partner in the project.
“Peatlands contain a disproportionate amount of carbon compared to other ecosystems, and understanding their sensitivity to climate change will be critical to predict what happens to the balance between carbon stored in peatlands and the amount of carbon dioxide and methane in the atmosphere.”
The location in the peatlands on the Chippewa National Forest was carefully selected by a team led by Hanson, who worked with ORNL colleagues Stan Wullschleger and Rich Norby to formulate plans for SPRUCE. The group benefited from Norby’s experience designing and running the 12-year Free-Air CO2 Enrichment experiment, which examined the responses to elevated carbon dioxide levels in a stand of sweetgum trees a few miles from ORNL.
The SPRUCE project gives them a chance to expand on those findings as they conduct previously impossible experiments with other researchers from ORNL, the Forest Service, other DOE laboratories and universities.
The official launch of SPRUCE was celebrated with an August 2015 event attended by representatives from DOE, ORNL, the Forest Service and elected officials.
With design, construction and ceremony behind them, Hanson and colleagues are focusing on questions that cover ecosystem responses ranging from the microbe to landscape scale. Those questions include:
- Will deep belowground warming release 10,000 years of accumulated carbon from peatlands?
- Will these carbon releases be in the form of carbon dioxide or methane, which has 30 times the warming potential of carbon?
- Are peatland ecosystems and organisms vulnerable to atmospheric and climatic change? What changes are likely?
- Will ecosystem services such as regional water balance be compromised or enhanced by atmospheric climatic change?
“Answers to these questions will provide insights not only for small-scale processes but also for landscape-relevant water, carbon and energy fluxes for similar peatlands,” Hanson said. “Results will inform higher-order models of vegetation responses under various levels of climatic warming and associated end-of-the-century atmospheric change.”