SPATIAL PATTERN IN BOREAL SHRUB COMMUNITIES - EFFECTS OF A PEAK IN HERBIVORE DENSITY

As part of a large-scale experiment on the dynamics of boreal forest c ommunities, we examined the effects of experimental manipulations on t he spatial pattern of two shrub species, Salix glauca and Betula gland ulosa, before and after the population peak of the herbivore Lepus ame ricanus, the snowshoe hare. Despite high rates of twig browsing during the peak, at most sites the basic characteristics of the spatial patt ern recovered quickly. Only where food addition and predator exclosure enhanced and prolonged thp hare density peak was there a sharp declin e in the intensity of spatial pattern of the preferred winter food pla nt Betula. The spatial pattern of these shrubs is resilient to normal changes in herbivory and may persist, therefore, for decades through s everal hare population cycles.