Canada’s boreal forests are known to help moderate the effects of climate change, absorbing and storing much more carbon dioxide from the atmosphere than they release. However, this balance seems to be shifting and Holly Deighton is working to understand why.
A biology PhD candidate in ecology and evolution, Deighton is studying how the soils of the boreal forest store carbon over long periods of time.
“Historically boreal forests have been regarded as a carbon sink, that is, taking in more carbon than they release,” said Deighton.
“But with increasing temperatures due to climate change and harvesting, the boreal forest seems to be shifting from a carbon sink to a carbon source, and we think that it could be a significant source of carbon being released into the atmosphere, especially in the next 100 years.”
Roughly 75 per cent of Canada’s forests are classified as boreal forest, and Canada has approximately 28 per cent of world’s boreal forest according to Natural Resources Canada.
If the forests begin to release more carbon than they store, warming can increase which would lead to even more carbon being released, creating a positive feedback loop.
“Roughly one third of the world’s terrestrial carbon stores are in the boreal forest, and with climate change as well as harvesting we risk losing a lot of the carbon that is stored both below and above ground,” said Deighton.
She goes on to explain that when trees are removed via harvesting the effect on soils can be significant.
“The soil temperature might rise, you might lose moisture, you might get different microbial communities due to those changes, which can lead to higher rates of decomposition and potentially significant losses of carbon in the soils. We know if you lose carbon in the soils, and it goes into the atmosphere, it contributes to that positive feedback loop.”
Deighton is conducting field work in Canada’s boreal forest at three sites set up by the Ontario Ministry of Northern Development, Natural Resources, and Forestry that she will have access to throughout the duration of her project.
This past summer she visited the sites at Sioux Lookout and Timmins. Next summer she is hoping to visit those sites as well as one in Kapuskasing.
Deighton said what makes the sites especially interesting and useful is that together, they present five different levels of silviculture intensity.
Silviculture is the attempt to control the growth, composition, and quality of forests and is especially important in the timber industry.
“Also, all three of these sites have different soil textures, with sands at Sioux Lookout, clays at Timmins, and silts at Kapuskasing,” said Deighton.
“I am looking at how much soil carbon is stored at each of these sites that vary in soil texture, under various silviculture intensities. I am also looking at how carbon is utilized by microbial communities at these sites.”
Microbial communities are groups of microorganisms that share a common living space. Deighton said that the novel part of her project is seeing how microbial communities are utilizing carbon across different soil textures.
“We hypothesize that microbial communities will differ across sites, and clay soils will be able to store more carbon than soils with less class such as silty soils or sandy soils,” says Deighton.
According to Deighton, most of the terrestrial carbon in boreal forests is stored underground, and if it gets released it could prove costly.
“The soils aspect of carbon research is critical, as there’s still so much we don’t understand,” Deighton said. “Determining how much carbon is stored in the forest floor and how that process works could prove vital in the fight against climate change.”