HR: 15:25h
AN: C33A-08    [Abstracts]
TI: Snow-mediated Ptarmigan Browsing Controls Shrub Expansion in Arctic Alaska
AU: * Tape, K
EM: kentape@hotmail.com
AF: Institute of Arctic Biology University of Alaska, Fairbanks, Koyukuk Drive, Fairbanks, AK 99775, United States
AU: Lord, R
EM: ftrel@uaf.edu
AF: Institute of Arctic Biology University of Alaska, Fairbanks, Koyukuk Drive, Fairbanks, AK 99775, United States
AU: Bret-Harte, S
EM: ffsmb@uaf.edu
AF: Institute of Arctic Biology University of Alaska, Fairbanks, Koyukuk Drive, Fairbanks, AK 99775, United States
AB: Large, late-winter ptarmigan migrations heavily impact the patch, shrub, and branch morphology of shrubs that remain above the snow surface. Ptarmigan browsing on arctic shrubs was assessed in the vicinity of Toolik Lake, on the Arctic Slope of Alaska, by counting the fraction of browsed versus total bud locations on Salix alaxensis, Salix pulchra, Salix lanata, and Betula nana. Data were collected in early May 2007, at maximum snow depth, after the bulk of the ptarmigan migration had passed through the area. In an area of large shrubs, half of the buds were browsed by ptarmigan. Three percent of the buds that were buried beneath the snow were browsed, 97 percent of the buds that were within 25 cm of the maximum snow level were browsed, and 46 percent of the buds above that height were browsed. In other areas, where all the shrubs were buried by snow at the height of the migration, 35 percent of the buds were browsed. These data were qualitatively extrapolated by observation westward to the Nanushuk River and eastward to the Jago River, about 250 km across a series of north-flowing rivers with headwaters in the Brooks Range. Ptarmigan hedging shrub patches, and shrub expansion under a warmer climate, are competing forces mediated by snow distribution. The outcome of these competing forces varies spatially, and can be inferred by examining the morphology of shrub patches, individuals, and branches.
DE: 0736 Snow (1827, 1863)
DE: 1632 Land cover change
DE: 1637 Regional climate change
SC: Cryosphere [C]
MN: 2007 Fall Meeting