PARENT SESSION
Poster Session 2: Forest Ecology
Monday, August 8, 5:00 PM - 6:30 PM, Exhibit Hall 220 A-E, Level 2, Palais des congrès de Montréal

Do plants respond equally to browsing by overabundant moose?

McLaren, Brian¹, Hermanutz, Luise^*,2, Gosse, John³, Kasimos, Costa², Collet, Ben¹, ¹ Lakehead University, Thunder Bay, ON, Canada² Memorial University, St. John's, NL, Canada³ Terra Nova National Park, Glovertown, NL, Canada

ABSTRACT- Although large herbivores, such as moose, are ubiquitous across the global boreal biome, comprehensive species-specific comparisons of response to mammalian herbivory are lacking. Here we report on the relative growth responses of rare vs common tree and shrubs on the island of Newfoundland, after 6 years of exclosure from moose. Moose were introduced to the island 100 yrs ago and have reached densities of 0.5-2.5 per km², about 10 times higher than in situations with wolf predation. This study was carried out in balsam fir (Abies balsamea) dominated stands, where moose overabundance has resulted in periodic and sustained habitat deterioration. Thirteen plot pairs (control vs exclosed) were sampled from within Terra Nova National Park (8 sites; managed without logging and hunting) and surrounding Forest Management District (5 sites; managed for logging and hunting). Habitat quality was assessed as site richness based on number of woody species present. Faecal pellet group counts indicated that moose use was constant over the 6 years within the National Park, while moose number decreased in the hunted area. Regressions of height and basal diameter confirmed that plants within exclosures reverted to adult growth form within a few years, growing significantly greater in height than those plants in the unfenced control. Habitat quality mediated the response to herbivory, such that growth response was greater in rich than poor sites (Betula cordifolia/papyifera, Sorbus americana, Acer rubrum, A. spicatum, Amelanchier bartramiana, Viburnum edule, V. cassinoides). In addition to growth responses, moose appear to be important architects of biodiversity, as many of woody species were absent or much reduced outside the exclosure, especially within the National Park where moose density is sustained. The plant species studied indicate that response is independent of rareness, but mediated by the habitat quality.

Key words: herbivory, moose, boreal forest, biodiversity