So Ryan Kelly and Feng Sheng Hu, of the University of Illinois Urbana and colleagues looked at charcoal fragments in the lake sediments of the Yukon Flats area of Alaska to build up a picture of the pattern of fires and model the history of the last 10, years.
Rise in wildfires depletes forests’ carbon store
They report in Nature Climate Change that they found that fire frequency in one 2, kilometre band of the forest is higher now than at any time in the last centuries. It follows that global warming — as a consequence of the release of the greenhouse gas carbon dioxide from the prodigal combustion of fossil fuels by humankind — is making the forests more vulnerable.
And, in turn, the forests may be releasing more CO 2, thus fuelling more global warming. And, simultaneously, this region is warming up faster than any other parts of the world. Ecosystems adapt to change: there had been a rule-of-thumb assumption that as the Arctic warmed, forests would expand further north to absorb more of the newly-available carbon, and serve as a brake on climate change.
This may not be the case. The research paper puts the message with more than usual clarity.
We chose the area for this study because we thought it could be an early indicator of the future. This series of mega-fires created the ideal environment to study whether carbon stores are being combusted by these types of fires. We wanted to see whether the extreme fires tapped into these old-legacy carbon layers or whether they were still preserved in the ground.
For the study, published in the journal Nature , the research team collected soil samples from more than forest and wetland plots across the territory. They applied a novel radiocarbon dating approach to estimate the age of the carbon in the samples. The researchers found combustion of legacy carbon in nearly half of the samples taken from young forests less than 60 years old.
Climate Change & Boreal Forests
This carbon had escaped burning during the previous fire cycle but not during the record-setting fire season of This pattern could shift boreal forests into a new domain of carbon cycling, where they become a carbon source instead of a sink. As wildfires are expected to occur more frequently and burn more intensely, old carbon may be released to the atmosphere more often. Fire is one mechanism that can release that old carbon back to the atmosphere quickly where it can contribute to the greenhouse gas effect. She said the potential switch of the boreal forest from carbon storage to carbon source directly impacts global climate and is not well represented in global models.
Turetsky said this research is important both because of its scientific findings and because it involved stakeholders in tracking the effects of climate change in Canada. Materials provided by University of Guelph.
Note: Content may be edited for style and length. Science News. Story Source: Materials provided by University of Guelph.
Journal Reference : Xanthe J. Walker, Jennifer L.
Fire, Climate Change, and Carbon Cycling in the Boreal Forest | SpringerLink
Baltzer, Steven G. Cumming, Nicola J. Johnstone, Stefano Potter, Brendan M.