E-mail : stephane.boudreau@bio.ulaval.ca

Caribou activity and its impact on vegetation ground cover of spruce lichen woodlands in Québec-Labrador
Supervisor : Serge Payette 


The population of the George River caribou herd grew from the end of the 1950s to the middle of the 1980s, and then becoming somewhat stable at about 700,000 individuals. The increased number of caribou had a considerable impact on the ground vegetation of spruce lichen woodlands. The objectives of this research are: i. to determine the spatial trends in the activity of the George River caribou herd, ii. to evaluate the impact of caribou on groundcover and lichen succession, and iii. to evaluate the performance of Cladina stellaris during the first few years of regrowth following the decline in caribou activity. An analysis of trampling scars caused by caribou hooves on conifer roots from 31 lichen woodlands indicated that there were two major patterns in caribou activity between 1975 and 1999. A major increase in the activity of the George River caribou herd occurred from 1975 to 1989, which corresponded to the demographic increase of the herd as shown by several aerial inventories. However, the herd activity was reduced considerably between 1989 and 1999 and corresponded likely to a decline of the population size. The hypothesis that the decline is attributed to a geographic displacement of the herd outside of the study area was considered invalid due to data pinpointing the location of caribou wearing satellite collars. Ground vegetation of spruce lichen woodlands, consisting of a continuous lichen carpet dominated by Cladina stellaris, can be destroyed by caribou browsing and trampling causing the underlying litter and mineral soil to be exposed. Degradation of the lichen cover initiates a return to early successional stages by creating favorable conditions for the establishment of early successional species. The performance of C. stellaris during the first few years of vegetation recovery was associated with severity of caribou disturbance.


Boudreau, S., Payette, S., 2004. Caribou-induced changes in species dominance of lichen woodlands: an analysis of plant remains. American Journal of Botany, 91: 422-429.

Boudreau, S., Payette, S., 2004. Growth performance of Cladina stellaris following caribou disturbance in subarctic Québec. Écoscience, 11: 347-355.

Payette, S., Boudreau, S., Morneau, C., Pitre, N., 2004. Long-term interactions between migratory caribou, wildfires and Nunavik hunters inferred from tree rings. Ambio, 33: 482-486.

Boudreau, S., Payette, S., Morneau, C., Couturier, S., 2003. George River caribou herd as revealed by tree-ring analysis. Arctic, Antarctic, and Alpine Research, 35: 187-195.