Potential for carbon sequestration in Canadian forests and agroecosystems

The potential for carbon (C) sequestration was examined in selected Canadian forest settings and prairie agroecosystems under several management scenarios. A simple C budget model was developed to quantitatively examine C sequestration potential in living biomass of forest ecosystems, in associated forest-product C pools, and in displaced fossil-fuel C. A review of previous studies was conducted to examine C sequestration potential in prairie agroecosystems. In the forest settings examined, our work suggests that substantial C sequestration opportunities can be realized in the short term through the establishment of protected forest-C reserves. Where stands can be effectively protected from natural disturbance, peak levels of biomass C storage can exceed that under alternative management strategies for 200 years or more. In settings where it is not feasible to maintain protected forest-C reserves, C sequestration opportunities can be realized through maximum sustained yield management with harvested biomass put towards the displacement of fossil fuels. Because there is a finite capacity for C storage in protected forest-C reserves, harvesting forest biomass and using it to displace the use of fossil fuels, either directly through the production of biofuels or indirectly through the production of long-lived forest products that displace the use of energy-intensive materials such as steel or concrete, can provide the greatest opportunity to mitigate greenhouse gas emissions in the long term. In Canadian prairie agroecosystems, modest C sequestration can be realized while enhancing soil fertility and improving the efficiency of crop production. This can be done in situations where soil organic C can be enhanced without reliance upon ongoing inputs of nitrogen fertilizer, or where the use of fossil fuels in agriculture can be reduced. More substantial C offsets can be generated through the production of dedicated energy crops to displace the use of fossil fuels. Where afforestation or reconstruction of native prairie ecosystems on previously cultivated land is possible, this represents the greatest opportunity to sequester C on a per unit-area basis. However, these last two strategies involve the removal of land from crop production, and so they are not applicable on as wide a scale as some other C sequestration options which only involve modifications to current agricultural practices.