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I strive to better understand the links between the biological components of ecosystems and their physical and chemical components. In concrete terms, I investigate how the building blocks of ecosystems, essential elements such as carbon, nitrogen and phosphorus, affect feeding interactions among species. For example, it has been shown that herbivores feeding on plants that are overly rich in carbon face deficits in other elements, such as nitrogen, and grow poorly. I strive to extend this multi-element vision of ecology, an approach called ecological stoichiometry, from the study of pairwise species interactions to the study of food webs, the whole set of species feeding on each other. In practice, I am involved in a project looking into the stoichiometric effects of reindeers on the mineralization of nitrogen by soil microbes in the arctic. I also study various plant-insect interactions in the field (leaf-eating insects on mountain birch trees) and in the lab, using willows, aspen (Populus tremula×tremuloides) and chrysomelid beetle species (Chrysomela tremulae and Phratora vittelinae). Concurrently, I explore how physical forces that act on each and everyone, such as gravity and drag, affect feeding interaction between species, and thus shape food webs. I collaborate with researchers at McGill University in Montréal, Canada, the University of Bath, in the UK, and the CNRS Experimental Ecology Station in Moulis, France, on a project that explicitly incorporates the effects of physical factors on the parameters driving trophic interactions. We have developed models of food webs as they emerge from species that interact according to these physical rules. My long-term goal is to come with a better understanding of the role of physico-chemical factors in shaping food webs and ecosystems, past, present and future.