Is recordbreaking season a vision of fires to come?
Part 2: How today's blazes help light tomorrow's fires
By Sonya Senkowsky
The deciduous trees making up the Alaska boreal forest include aspen and birch. In some places, especially in regions underlain by permafrost and covered by lichens and mosses, even mature trees may be merely scrub--scrawny, sparse, no more than several meters tall and only a few centimeters in diameter.
So how do such “Charlie Brown Christmas trees” make even a dent in global climate change?
The key lies beneath the pillowy mounds of mosses that carpet the forest floor. The soils below are the product of centuries of accumulated forest litter.
“Our research has shown that large amounts of organic soils can be burned during fires, releasing large amounts of carbon to the atmosphere,” Kasischke says.
“These organic soils form over hundreds to thousands of years, so when they burn, it’s going to take hundreds to thousands of years for them to reaccumulate—a far greater time period than the lifespan of the aboveground vegetation that exists through the next sequence of regrowth of the forest.”
Also a factor in this region, permanently frozen ground, or “permafrost,” can lie as close as 30-60 centimeters below the ground surface, especially where well insulated by moss or forest litter. Decomposition of accumulated organic materials is slowed by permafrost, which helps to keep the ground temperature low during even Alaska’s long summer days.
“Biologically based models ... assume that variations in soil and air temperature are proportional and don’t account for permafrost,” Kasischke says. With reduced insulation, permafrost layers could melt and the surrounding soil could become warmer, potentially resulting in years of additional net carbon loss.
Copyright 2004 AlaskaWriter LLC. Portions of this story were previously published in BioScience magazine, Vol. 51, No. 11. Editors: For permission to run this story in your publication, please contact firstname.lastname@example.org. Stories must run with the tagline: “For more science stories, see Alaska Science Outreach at http://www.alaskascienceoutreach.com.”