Structure and composition of forest edges created by a spruce budworm outbreak and maintained by moose browsing in Cape Breton Highlands National Park

Abstract

Natural forest edges created by a severe spruce budworm outbreak in Cape Breton Highlands National Park, Nova Scotia, Canada, have been maintained three decades post-disturbance by moose browsing. My overall research objective was to determine the direct and indirect effects of edge creation on vegetation structure and composition. Trees, deadwood, and understorey plants were sampled along 120 m transects perpendicular to six forest edges. The spruce budworm-induced forest edges were characterized by narrow transition zones where canopy cover, stem density, and structural diversity were intermediate between the disturbed area and forest. Severe moose browsing appears to be preventing sapling growth and altering species composition, particularly on the insect disturbed side of the edge. If moose continue to maintain the forest edge, contrasts in vegetation structure and composition between the severely browsed disturbed area and adjacent intact forest could increase and ultimately alter forest edge function.