Effects of moose browsing on vegetation and litter of the boreal forest, Isle Royale, Michigan, USA

Tree biomass was significantly greater (mean 230 vs. 150 Mg/ha), shrub biomass was significantly less (1.9 vs. 3.1 Mg/ha) and herb biomass was significantly less (0.2 vs. 0.8 Mg/ha) in exclosures than in browsed plots. Tree production was greater in exclosures than in browsed plots (7.9 vs. 5.0 Mg.ha^-1.yr^-1), but there was no difference in the production per unit biomass between exclosures and browsed plots. Shrub production in exclosures was similar to that of browsed plots (0.4 vs. 0.3 Mg.ha^-1.yr^-1). Litter production was greater in exclosures than in browsed plots (3.5 vs. 2.3 Mg.ha^-1.yr^-1), despite total vegetation biomass differences between paired plots. There was significantly greater herb litter produced in the browsed plots than in the exclosures (0.7 vs. 0.1 Mg.ha^-1.yr^-1). Alces alces browsing prevented saplings of preferred species from growing into the tree canopy, resulting in a forest with fewer canopy trees and a well-developed understory of shrubs and herbs. Browsing may also have altered the eventual balance of white spruce Picea glauca with balsam fir Abies balsamea, causing an increase in the former and a decrease in the latter. -from Authors