Carbon forms and fluxes in different land use systems

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To increase carbon (C) storage in the soil is important for mitigating the rapidly changing global climate. Afforestation of marginal agricultural land is considered a viable option for increasing soil C storage. However, the effects of land use change, afforestation in particular, on soil C dynamics are complex and poorly understood. In this research we will study four different land use systems, agricultural, grassland, forest plantation and native forests in the grassland-forest transition zone across western Canada. I will 1) investigate the effect of land use change on the emission of carbon dioxide (both by soil microbial organisms and by roots), methane and nitrous oxide, and their resulting global warming potential in each land use system; 2) evaluate the relative contribution of winter soil greenhouse gas (GHG) emissions to annual emissions and how that is affected by land use change, to help understand the total annual GHG fluxes of the different land use systems; 3) evaluate the effects of land use change on soil organic C forms, including low molecular weight organic acids, and C distribution in the subsoil; and 4) relate soil organic C form to soil C stability. This study will provide a full accounting of all three trace GHGs and on year-round rates of GHG emissions in different land use systems and will thus provide the much needed data for the calculation of national inventories of GHG emissions, as country-specific methodologies are needed to account for the impact of regional climate and land use on GHG emissions. Such data will help determine the emission factor for each land use system, allowing governments to adjust policies that will promote those land use systems that provide greater environmental services. The potential benefit of afforestation for climate change mitigation through increased C sequestration and C stability across the region will be studied. This study will thus provide novel information on the mechanisms of soil organic C stabilization and the mechanisms underlying the effects of land use change on GHG emissions. This research will eventually have implications for international treaty negotiations on climate change.