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Shrub expansion in response to climate change has been reported in many circumpolar locations. Densification of the shrub layer in subarctic and arctic regions could be induced by temperature increase and acceleration of biogeochemical cycles, both associated to climate change. Herbivores also induce changes in vegetation by reducing productivity of browsed species. The intensity of this influence varies among plant species because browsers exert a high selection for favorite species in their diet. In Deception Bay, Nunavik, Quebec, in the summer range of migratory caribou (Rangifer tarandus L.) from Rivière-aux-feuilles herd (RAFH), climate change and browsing should drive shrub growth. Preliminary observations suggest that tea-leaf willow (Salix planifolia Pursh.) and dwarf birch (Betula glandulosa Michx.) stands have different dynamics, particularly because the former is less tolerant than the latter to caribou browsing. Thus, willows are few and moribund as oppose to birches, which are abundant.
This project aims to evaluate dynamics of two dwarf-shrub species occurring in the summer range of the caribou. To do so, we will estimate the response of birch to browsing pressure, and climate change induced temperature increase and acceleration of biogeochemical cycles. Furthermore, we will describe recent dynamics of tea-leaf willow and dwarf birch stands by measuring height, proportion of dead or moribund individual shrub shoots and individual radial growth.