PARENT SESSION
Poster Session 34: Herbivory
Thursday, August 11, 5:00 PM - 6:30 PM, Exhibit Hall 220 A-E, Level 2, Palais des congrès de Montréal
Impacts of white-tailed deer on deciduous forest floor vegetation at the northern periphery of it's range in North America.
Collard, Amélie*,1, Lapointe, Line1, Côté, Steeve1, Crête, Michel2, Ouellet, Jean-Pierre3, 1 Université Laval, Sainte-Foy, Québec, Canada2 Société de la faune et des parcs du Québec, Québec, Québec, Canada3 Université du Québec à Rimouski, Rimouski, Québec, Canada
ABSTRACT- White-tailed deer (Odocoileus virginianus) densities increased dramatically in North America over the past century. Many studies have reported significant negative impacts of deer on forest floor vegetation, but very few have been conducted at the northern limit of it's range where deer densities increased at an exceptional rate since the early 80's. Our objective was to examine the impacts of deer on deciduous forest understory vegetation in southern Quebec. We predicted that deer influence deciduous forest floor vegetation and specific richness by affecting plant growth, reproduction and survival of certain understory species. The data were collected in 2004 on 6 sites in southern Quebec where deer densities reach up to 7 to 30 deer/km2. One 625m2 exclosure were established on each site in 1998. Aerial part biomass and plant height, reproductive status and survival rate were measured in each exclosure and control site for four herbaceous species, Trillium erectum, Arisaema atrorubens, Erythronium americanum and Maianthemum canadense. Plant height, plant leaf number and diameter were measured on three woody species at the juvenile stage, Acer saccharum, Fraxinus americana and Prunus virginiana. We also measured species richness and density in the exclosures. We could not detect differences in plant size for any of the three woody species even after 6 years of deer exclusion. Differences in size were not constant in herbaceous species except for Trillium erectum which showed a significant increase in size, and more frequent flowering and fruit production following deer exclusion. Some explanations will be put forward to explain this apparent lack of impact including the resilience of some of the woody species, the potential disappearance of the very sensitive species and the overall slow recovery of plants under shaded conditions. These results will give valuable insight on the impact of deer on forest floor vegetation at the northern limit of deer range in North America.
Key words: plant-herbivore interactions, species richness, browsing, herbivory