Given Their Respiration Patterns, Boreal Forests No Refuge From Climate Change

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In the late 1990s, a Canadian and American team of forest scientists went into the woods in northern Manitoba to do something never been done before. They wanted to measure carbon going into -- and out of -- a living forest, to learn how effectively the forest was sucking carbon dioxide out of the atmosphere and storing it. That's called being a "carbon sink." They chose an area that belongs to the boreal forest -- the northern forest dominated by black spruce that is Canada's most widespread, and still most untouched forest.

What they found in the BOREAS study surprised many. The team made 22,000 hours of intensive measurements of the soil, the surface of the ground, and all the way up through the 120-year-old forest past the canopy to open air. They learned carbon goes both ways. From late May through July, new growth made the spruce forest "inhale" one to one and a half grams of carbon per square metre of forest per day. In August and September, the hottest, driest period, the rate of carbon dioxide movement fell to about zero.

But in the late summer and fall, the forest "exhaled" carbon back into the atmosphere at a rate of a little less than one gram per square metre per day, as warmer soil allowed soil bacteria to digest organic matter and release carbon dioxide. This fell to a much lower rate through the winter. Overall, in three of the four years they measured, the forest was putting slightly more carbon into the air than it took out -- a bad thing, if we want forests to store this material. The fourth year, the balance tilted the other way: The forest sucked out and stored carbon -- but not a lot of it.

"Forests on average certainly exchange a lot of carbon with the atmosphere," team leader Steve Wofsy of Harvard University said in an interview. "So if you want to say: 'Do they remove a lot of carbon from the atmosphere?' -- yeah, sure they do. Do they put back a lot? Sure, they do that, too."

EDIT

http://www.canada.com/ottawacitizen/news/arts/story.html?id=e01a36f4-0256-4613-b584-46e25d9407ae&k=5468

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