UO team helps show peatlands may hold on to carbon

Carbon accumulating deep in peat around the world may be less likely to be released into the air by global warming than originally thought, according to new findings by a research team that included UO contributors.

The research — published online Dec. 13 in the journal Nature Communications — is viewed, for now, as good news. The study was the first to explore under natural field conditions what happens to deeply buried carbon when it warms under impending climate change.

Roughly a third of the world's carbon is stored in northern peatlands. That's the equivalent to all of the carbon dioxide currently in the atmosphere. Peatlands are often 6 to 9 feet deep — some are deeper — and contain carbon that is thousands of years old that has been stored under cold, permanently waterlogged conditions.

"The major conclusion of this study is that the vast reservoir of carbon stored deeply in northern peatlands, especially those without permafrost, is relatively insensitive to even large increases in temperature for over a year," said co-author Scott Bridgham, a UO professor of biology and director of the Institute of Ecology and Evolution.

"This is of vast importance because if increasing temperatures mineralized that peat carbon as carbon dioxide and methane then this would be a major natural feedback to warming generated by human activity," he said.

The research was done in northern Minnesota as part of the Oak Ridge National Laboratories’ Spruce and Peatland Response Under Climatic and Environmental Change experiment, also known as SPRUCE. Additional work was done in labs at collaborating institutions.

"A large unknown in the scientific community has been whether or not climate change would stimulate the breakdown of carbon stored at depth in peatlands," said Anya Hopple, a UO doctoral student working with Bridgham. "We collected peat samples from multiple depths and incubated them at the UO at temperatures similar to those used to manipulate the SPRUCE site. This enabled us to see how depth-specific carbon dioxide and methane production rates changed in response to increasing temperatures."

Rachel Wilson, a postdoctoral scientist in the Department of Earth, Ocean and Atmospheric Sciences at Florida State University and a co-lead author on the paper with Hopple, said surface peat responded to experimental warming but peat below a depth of 2 feet, which was deposited thousands of years ago, was insensitive to warming.

The findings, Bridgham cautioned, reflect just one year of the scheduled 10-year SPRUCE experiment.

"Methane, in particular, is a very potent greenhouse gas," he said. "Other ecosystem feedbacks may become important in greenhouse gas emissions. For example, a recent paper just published by our colleagues showed in other northern Minnesota peatlands that long-term changes in precipitation can drive easily decomposable recent carbon deep into the peatland profile where microbes can convert it into methane."

That paper, led by Paul Glaser of the University of Minnesota, Twin Cities, was published online Nov. 3 in the journal Global Biogeochemical Cycles.

For the project detailed in Nature Communictions, the Oak Ridge team built 10 environmental chambers 29 feet in diameter and 21 feet tall to enclose the entire peat column and vegetation of the wetlands. Only the peat was warmed in a stepped response up to 16 degrees Fahrenheit above ambient to encompass the extremes of predicted climate change.

In the future, the scientists will look at how peatlands respond to heightened carbon dioxide levels combined with the warming of both the soil and vegetation. Peat is a highly organic material found in marsh or damp regions around the world but is particularly prevalent in northern wetlands.

"The SPRUCE project is so exciting and novel, because it represents a new phase of experimental manipulation," Hopple said. "As a young scientist, it’s extremely motivating to see the high level of science that can be achieved through effective funding and collaboration among a community of excellent scientists."

Laurel Pfeifer-Meister, a research associate in the UO Institute of Ecology and Evolution, also was a co-author on the paper.

The U.S. Department of Energy funded the research. Other contributing institutions were the U.S. Department of Agriculture, Chapman University, Georgia Tech University, Lawrence Livermore National Laboratory, Pacific Northwest National Laboratory and U.S. Forest Service.