Spatial patterns of moose browsing, community structure, and nitrogen cycling in boreal landscapes

Annual consumption of browse by moose, soil nitrogen availability, and population structure of the tree community was measured at 100 points on grids in two replicate valleys on Isle Royale. N availability was elevated but extremely variable spatially and temporally where moose browsing was negligible, but low and spatially and temporally constant when moose browsing exceeded 2 g/m² per year. Small diameter aspen and paper birch were absent where moose browsing was high, but individuals of small diameters persist where moose browsing was negligible. In contrast, the abundance of balsam fir and white spruce increased with intensity of moose browsing. Geostatistical analyses show a range of spatial autocorrelation of 100-150 m for all properties. Kriged maps show patches of high moose browsing mirrored by patches of low N availability. Through selective browsing, moose can impose structure on boreal ecosystems and landscapes.