Trees killed by a forest fire in Kootenay National Park, B.C., will release carbon as they decompose
With carbon molecules composing up to 50 percent of their dry weight, trees play an important role in the carbon cycle. Globally, it is estimated that forests remove approximately one third of fossil fuel emissions from the atmosphere each year.
New research is examining the carbon dynamics of Canada's managed forests, which make up 2.3 million km2 of the country’s estimated 3.5 million km2 total forest area. Managed forests take several forms, and include forests managed for sustainable harvest of wood fibre or wood-based bioenergy, lands under protection from natural disturbances, and protected areas that are managed to conserve ecological values.
Natural Resources Canada (NRCan) researchers set out to determine if Canada’s managed forests are taking up more carbon than they release and to identify key drivers of net carbon flows. To accomplish this, they developed a system that uses carbon data from tree biomass, litter, dead wood and soil to help quantify forest carbon stocks and flows.
Together with data about fires, insect outbreaks and management activity, the Carbon Budget Model of the Canadian Forest Sector (CBM-CFS3) estimates carbon absorption and release.
The results show that on average Canada’s managed forests are taking up more carbon than they release. However, many factors affect the carbon uptake or release by managed forests year to year.
Managed Forests are Active Carbon Sinks
Carbon is removed from the atmosphere by growing forests and emitted back into the atmosphere by plant respiration, decomposition and fire
The results show high variability in carbon flows from year to year, which are largely the result of natural factors. Fire has an immediate and significant impact, releasing an annual average of 23 million tonnes of carbon. In comparison, pests have slower and longer impacts, as the trees they kill release carbon into the atmosphere slowly over time through decomposition.
Why Count Carbon?
The estimates produced by NRCan can be used by forest managers to plan and make decisions that could help mitigate climate change. They also help Canada to meet its international reporting obligations on carbon emissions to the United Nations Framework on Climate Change.
“Canada has ten percent of the world’s forests,” says Graham Stinson, a physical scientist for the Canadian Forest Service and the lead author of the study. “As stewards of these forests, we have an international responsibility to understand and report how our forests interact with the atmosphere. This will help us to anticipate how things might change in the future and better manage our own impacts.”
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