Terrain Ruggedness and Caribou Forage Availability during Snowmelt on the Arctic Coastal Plain, Alaska
This paper reports a close link between terrain ruggedness and forage availability for caribou during snowmelt. Indices of terrain ruggedness based on contour characteristics from topographical maps were related to field measures of cover, biomass, and live/dead ratio of graminoids within the Kuparuk Oilfield, Alaska. Terrain ruggedness was found to be the most significant factor affecting forage availability during snowmelt within the study area. Terrain ruggedness was positively correlated to 1) graminoid cover within wet, moist and dry herbaceous tundra, 2) cover of four individual graminoid species, 3) height of Salix planifolia, 4) amount of Eriophorum vaginatum flowers, and 5) live/dead ratio of plant material during early and late snowmelt. The live/dead ratio of plant material varied among vegetation types during snowmelt, causing rugged areas to have sprouting green plant material available for forage throughout this period. While annual differences in snow depths and snowmelt will affect forage availability in a given year, indices of terrain ruggedness combined with vegetation maps can substantially improve our understanding of how forage availability for caribou may vary across the landscape during snowmelt.
Key words: Alaska, caribou forage, spring, topography, vegetation