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Snow-mediated ptarmigan browsing and shrub expansion in arctic Alaska

TitleSnow-mediated ptarmigan browsing and shrub expansion in arctic Alaska
Publication TypeJournal Article
Year of Publication2010
AuthorsTape, KD, Lord, R, Marshall, H-P, Ruess, RW

Large, late-winter ptarmigan migrations heavily impact the shoot, plant, and patch architecture of shrubs thatremain above the snow surface. Ptarmigan browsing on arctic shrubs was assessed in the vicinity of Toolik Lake, on the northside of the Brooks Range in Alaska. Data were collected in early May 2007, at maximum snow depth, after the bulk of theptarmigan migration had passed through the area. In an area of tall shrubs, half of the buds on Salix alaxensis were browsedby ptarmigan. Three percent of the buds that were buried beneath the snow were browsed, 90% of the buds that were less than30 cm above the maximum snow level were browsed, and 45% of the buds above that height were browsed. Ptarmiganbrowsing was found to be a major height limiter for tall shrubs, thereby controlling shrub architecture by brooming stems atthe snow surface and inducing stump shoots. These results were qualitatively extrapolated by photographing shrub morphologyover a region approximately 300 km wide across a series of north-flowing arctic rivers with headwaters in the Brooks Range.Ptarmigan ‘‘hedging’’ of shrub patches, and shrub growth under a warmer climate, are opposing forces mediated bysnow distribution.

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