Grant: Discovery Grants Program - Individual

The boreal forest, the world's largest land biome, is characterized by a high density and diversity of freshwater ecosystems. Those water bodies form a complex aquatic network that constantly interacts with the boreal forest. However, research in terrestrial and aquatic ecology have been traditionally kept separated because of scientist specialization. This separation of disciplines has left knowledge gaps regarding lake-forest interactions, exchanges that are nevertheless essential to the overall functioning of the boreal biome. Among the aquatic-terrestrial interactions, the impacts of natural terrestrial disturbances on lake carbon cycle and food webs are particularly ill understood. Insect outbreaks cause significant tree mortality and represent a major disturbance in temperate and boreal forests. They are however part of the forest natural cycle and contribute to shaping their structure and functioning. Defoliators such as the spruce budworm (Choristoneura fumiferana) may affect large area of boreal forest and transform tree biomass in animal biomass and frass containing more easily accessible carbon and nutrients than when stored in coniferous needles. This new inputs have the potential of decreasing (light attenuation) or increasing (with nutrients) aquatic primary and secondary production, modifying the entire lake nutrient and carbon cycle. Despite their significance, the fate and impacts of this new processed terrestrial biomass in aquatic ecosystems is largely unknown. The long-term objective of my research program is to contribute to the boreal landscape ecology providing new knowledge on the role of natural terrestrial disturbances in aquatic environments. During the next five years, I propose to 1) Determine the composition and quantity of t-OM from insect outbreaks into boreal lakes and evaluate its consequences on the aquatic carbon cycle, 2) Evaluate the effect of terrestrial organic matter inputs from insect outbreaks on the dynamic of microorganism communities and 3) Estimate the terrestrial organic matter transfer from insect outbreaks to aquatic food webs via the calculation of aquatic consumer allochthony and its influence on their growth, reproduction and nutritional quality. This research program aims to contribute to the next change of paradigm about the aquatic ecosystem concept as integrated components of the boreal forest and not as isolated ecosystems. It will help building a more accurate estimation of the carbon cycle of lakes with the effects of natural disturbances taken into account. Novel methods will be used to better estimate carbon fluxes such as invertebrate growth estimation with enzymatic method or quantitative estimation of carbon fluxes from terrestrial origin with Bayesian modeling. In a long-term perspective, this research will also help to include aquatic ecosystems in the sustainable management of forests, a critical action required in Canada to tackle the challenge of the ongoing climate change.