McInnes et al. examined the influence of moose (Alces alces) on aboveground biomass, production, and annual litterfall using four moose exclosures and paired browsing plots on Isle Royale, Michigan. In terms of species richness, moose browsing did not alter the number of plant species. The mean tree biomass was significantly greater in the exclosures than in browsed plots (230 and 150 Mg/ha). Every exclosure had more trees than corresponding browsed plots. The abundance of most species in the browsed plots and exclosures varied widely from site to site, only balsam fir (Abies balsamea) biomass differed significantly between the browsed and exclosure plots (2 vs. 24 Mg/ha). The mean shrub biomass of all exclosures, 1.9 Mg/ha, was less than in the browsed plots, 3.1 Mg/ha. There was no significant difference between shrub production in the exclosures, 0.4 Mg . ha-1 . yr-1, and browsed plots, 0.3 Mg.ha-1.yr-1, although shrub production differed greatly between stands. Browsing also had little effect on the amount of nutrients returned to the soil through litter-plus-herb material. Overall, moose removed from 0.01 to 20.6 kg.ha-1.yr-1 of plant material from the browsed plots, and these results indicate that the major effect of moose browsing on the Isle Royale boreal forest was an opening of the tree canopy. With this opening of the canopy, the herb layer became a greater portion of the community biomass.
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