Carbon under Canadian forests- why soils matter

Forests occupy about 40% of Canada, with managed forests totalling 225 million hectares. While Canadian forests have historically acted as an essential carbon sink for Canada, intensifying disturbances have drastically decreased the carbon sink provided by trees. However, most carbon is found belowground in Canadian forests, with forest floors and mineral soils containing more than three times the amount of carbon stored in trees. About 28,800 million tonnes of carbon are sequestered in mineral soils of Canadian forests alone, corresponding to 10% of stocks found in forest soils globally. Even slight variations in these extensive carbon stocks can have a profound impact not only on the carbon balance of Canadian forests but also on the global carbon cycle. Despite their importance, there is still great uncertainty about the mechanisms controlling soil carbon persistence in Canadian forests.

Our research project aims to address this major knowledge gap by quantifying soil carbon formation and persistence across the major forested ecozones of Canada. We have established a nationwide network of experimental sites to compare key soil types under different tree species representative of Canadian-managed forests. We will measure the decadal sensitivity of soil carbon to environmental shifts, including global change, harvesting and fire. We will clarify the linkages between carbon persistence and soil biodiversity. Overall, this research project will establish the foundational scientific knowledge required to improve current predictions of soil carbon response to environmental shifts in Canadian forests. This will, in turn, allow for a meaningful inclusion of forest soil carbon in Canadian climate policies, including global commitments under the United Nations Framework Convention on Climate Change.