Communautés végétales et interactions plante-herbivore : comment l'espèce, la qualité nutritive et la répartition spatiale des plantes environnantes influencent le broutement par les grands herbivores

Authors: Champagne, Émilie
Advisor: Tremblay, Jean-PierreCôté, Steeve D.
Abstract: Plant-herbivore trophic interactions can be indirect, such as when the consumption of a plant by an herbivore is influenced by the presence of a neighbouring plant. The influence of neighbouring plants on herbivores’ selection has been described in studies of foraging but also in studies of associational effects between plants. Because of their parallel evolution, some common theme in the studies of animal foraging has been seldom addressed in the understanding of associational effects among plants. The general objective of this thesis is to understand the indirect effects of vegetation communities on plant use by large herbivores, in the context of factors affecting foraging. First, I investigated at which distance a neighbouring plant can influence herbivores’ selection, because foraging is a spatially hierarchical process. By a meta-analysis, I uncovered that neighbouring plant can influence the use of other plant species by large herbivores up to hundreds square metres. By a study of associational effects on Anticosti Island (Québec, Canada), I also demonstrated that neighbouring plants can increase or decrease browsing by white-tailed deer on balsam fir, depending on the scale considered. Second, I tested the relative contribution on associational effects of factors susceptible to influence foraging by herbivores. For example, the nutritional quality of neighbouring plants increased browsing on firs. Moreover, the relative abundance of plants in the community can generate associational effect: in the Outaouais region (Québec, Canada), white pines were less browsed in diversified plots where the relative abundance of preferred species was lower. My thesis supports the importance of incorporating an animal perspective, which takes into account the objectives and constraints on herbivores foraging choices, in the study of associational effects. Moreover, it offers promising research perspective, like including plant intraspecific variability in functional traits, such as nutritional value, and considering associational effects at multiple spatial scales. This work improves our understanding of indirect trophic interactions, by demonstrating the influence of factors such as resource abundance on these interactions. It also proposes a mechanism, foraging processes of herbivores, which paves the way to a generalization of associational effects in different systems.
Document Type: Thèse de doctorat
Issue Date: 2017
Open Access Date: 24 April 2018
Grantor: Université Laval
Collection:Thèses et mémoires

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