Balsam fir on Isle Royale: Effects of moose herbivory and population density
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Authors: T. A. Brandner, R. O. Peterson, and K. L. Risenhoover
Date: 1990
Journal: Ecology
Volume: 71
Number: 1
Pages: 155-164
Summary of Methods: Moose (Alces alces) herbivory was assessed in relation to population parameters of both Balsam fir (Abies balsamea) and moose populations on Isle Royale National Park, Michigan (47° 55' N, 89° 00' W). Nine study sites were selected from four zones with varying moose densities (absent, low, medium and high) and four zones of fir densities (absent, low, medium and high). The sites missing both moose and fir were excluded. All vegetation sampling was conducted from May through mid-July of 1985. Browse damage was classified in four categories: 0=unbrowsed; 1=side branches browsed only; 2=apically browsed once; 3=apical leader browsed twice or more.
Article Summary / Main Points: Both moose and balsam fir densities were significant determinants of the impact of moose on fir growth and population structure. Foraging damage to balsam fir was greatest where moose density was high and/or fir density was low. Fir density appeared more important in determining forage impact in this study. Continuing canopy losses and lack of recruitment in some areas, due to intensive herbivory by moose, will greatly reduce the fir component of the canopy. Long-lived, browse-tolerant fir will persist on Isle Royale, but may never again produce the dominant forests of the past.
Vegetation Types: Riparian and Wetlands
MLRA Ecoregions: 93B Superior Stony and Rocky Loamy Plains and Hills, Eastern Part
Agrovoc Control Words: Riparian zones Browse plants Wildlife
Article Review Type: Refereed
Article Type: Experimental Research
Keywords: balsam fir, abies balsamea, moose, alces alces, boreal, browsing, conifer, foraging, herbivory, isle royale national park
Annotation: This study shows the important relationship between wildlife density and woody browse. It is important to remember that during this study moose populations varied greatly from year to year, as moose density may still be a very important factor.
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