ABoVE Looks Below the Surface for Carbon Answers

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Tyler Gault, an undergraduate student at Northern Arizona University in Flagstaff, holds a cross section of tundra soil – moss, over slightly decayed moss, over more decayed moss. These layers can be hundreds or even thousands of years old. Credit: Walker/NAU

Tyler Gault, an undergraduate student at Northern Arizona University in Flagstaff, holds a cross section of tundra soil—moss, over slightly decayed moss, over more decayed moss. These layers can be hundreds or even thousands of years old. Researchers are studying whether ’legacy carbon’—carbon that has been stored in the soil for centuries—is being released into the atmosphere in recent, severe fires. Credit: Xanthe Walker/Northern Arizona University

by Kate Ramsayer / DENALI NATIONAL PARK, ALASKA /

A National Park Service helicopter lifted off Sunday morning, July 10, flying past dark clouds and green mountain slopes on a 20-minute trip deep into the Denali National Park wilderness. On board are researchers and lots of gear, from shovels to plot markers to food and water for a week. The destination: a plot of tundra charred by a wildfire in 2013. Ecologist Xanthe Walker and her crew will sample the remaining soil, looking to see if the fire burned through carbon that had been stored in the ground for centuries.

“The tundra’s not supposed to burn like that,” said Brian Howard, a PhD student at Northern Arizona University in Flagstaff.

“Which is why we want to study it,” said Walker, a postdoctoral researcher at the university.

Their study is part of the Arctic Boreal Vulnerability Experiment, or ABoVE, a NASA-funded, decade-long effort to go into the field in Alaska and Northwest Canada to answer questions about this key region.

“At its core, ABoVE is attempting a study of the vulnerability and resilience of ecosystems—and not just ecosystems, but society—to rapid environmental changes that are already taking place,” said Peter Griffith, ABoVE chief support scientist based at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “The Arctic and boreal region is a perfect laboratory to study climate change.”

Peter Griffith, Brian Howard and Xanthe Walker discuss field work in Denali National Park to study whether ’legacy carbon’ – carbon that has been stored in the soil for centuries – is being released into the atmosphere in recent, severe fires. Credit: Ramsayer/NASA

Peter Griffith, Brian Howard and Xanthe Walker discuss field work in Denali National Park. Credit: Kate Ramsayer/NASA

It’s not necessarily an easy laboratory to work in, though. Walker’s field site isn’t a flat, squishy moss terrain—there are knee-high mounds of tussock grass, sticking up over mucky burned soils. It was rainy a week or so ago when the group went to sample sites, and there is a rainy forecast for the week ahead.

“I love it, even in the rain,” Walker said. “You’re back in the field, actually seeing what you’re studying instead of seeing numbers on a computer screen.”

The computer screen will come in the fall, when she analyzes the measurements gathered this summer not just in Denali, but at similar sites farther north in Alaska as well as Canada’s Northwest Territories. Walker and the project’s principal investigator, Michelle Mack, are asking the question: As the climate gets warmer, and summers get hotter and drier, are fires in the tundra becoming more severe and releasing carbon long stored in the ground?

The tussock tundra soils in her Denali sites are basically layers of moss—live moss, on top of slightly decayed moss, on top of more decayed moss. This moss in varying stages of decay can be a foot deep in places. While fires decades ago might have just burned the top layers of moss, leaving the lower, often-frozen layers intact, Walker is testing whether more recent fires go deeper.

An unburned cross section of tundra soil shows the rich organic layers beneath the surface. Scientists are studying how a much carbon would be released by a severe fire. Credit: Walker/NAU

An unburned cross section of tundra soil shows the rich organic layers beneath the surface. Scientists are studying how much carbon would be released by a severe fire. Credit: Xanthe Walker/Northern Arizona University

“That’s an indication that the fires are releasing much more carbon into the atmosphere than they used to,” Walker said. To find out, she’s taking soil samples, wrapping them up in tin foil, packing them in one of the six coolers that will be full by the end of the week, and driving them back to the lab for radiocarbon dating.

Howard is also studying not just the soils, but also what’s growing back after a fire, from mosses and lichens to trees. In the early 2000s, the National Park Service did a survey of the 50 sites the team is studying, so they have records of what the site was like before the 2013 fire to compare with this summer’s data.

“What’s interesting about these plants is they weren’t the plants that were there before a fire came through,” Howard said. Burning up more soil, and a warming temperature, could mean different grass, shrub or tree species popping up in the Arctic tundra. That’s what he’s trying to find out.

In addition to looking at the soils, researchers in Denali are studying what plants grow back after a severe fire in the tundra – and whether those plants are different from what was there before. Credit: Walker/NAU

In addition to looking at the soils, researchers in Denali are studying what plants grow back after a severe fire in the tundra—and whether those plants are different from what was there before. Credit: Xanthe Walker/Northern Arizona University