A process-based model for assessing the impacts of reservoirs and forest harvesting on the carbon budget of aquatic aquatic ecosystems

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Human activities such as forest harvesting and reservoir impoundment have profoundly impacted the global carbon cycle and, in particular, the atmospheric carbon dioxide (CO2) emissions of land ecosystems. Reservoir impoundment leads to transient and permanent changes in the biogeochemical processes taking place in the water column and the sediments, while forest harvesting strongly modifies the fluxes of terrestrial organic matter (TOM) to aquatic ecosystems. As part of a collaborative effort with governmental partners (Environment Canada, Ministère du Développement Durable, de l'Environnement et des Parcs du Québec), we propose to exploit the latest advances in analytical organic biogeochemistry to develop a fine molecular understanding of (i) the factors responsible for the degradation or sequestration of TOM in aquatic systems, and (ii) the impact of forest harvesting and reservoir impoundment on these factors in terms of changes in the greenhouse gas (GHG) emissions budget at the watershed scale. To generalize our approach and verify our conclusions in aquatic ecosystems across the country, we will develop a new process-based model (Integrated Carbon Cycle Model - ICC model) linking the terrestrial and aquatic ecosystems. This model will use a short list of aquatic biogeochemical tracers to integrate (i) carbon dynamics in lakes or reservoirs, and (ii) modifications in TOM exports due to forest harvesting, to ultimately provide estimates of GHG emission budgets in these contrasting environments. The ultimate goal is to generate and transfer biogeochemical and modeling knowledge to our governmental partners to assist them in determining the long-term effects and significance of such disturbances in relation to anthropogenic GHG emissions or removals from aquatic ecosystems.