Productivity and Carrying Capacity of a Subarctic Sheep Winter Range

Estimates of range composition and net primary productivity for a 10-year period are presented for the semi-arid grasslands of Sheep Mountain, Kluane National Park, Yukon, the winter range of a Dall's sheep (Ovis dalli dalli) population. Estimates varied among plots, depending on altitude and aspect, as well as among years, according to rainfall during the growing season. Extremes were 29.1 g/sq m and 120.1 g/sq m. Over the 10-year assessment period, the vegetative composition did not change nor was there a grazing-related reduction in productivity. Winter range use by about 200 sheep was within the carrying capacity of the range. A 40% utilization rate of the winter range forage can evidently be sustained and provides a stocking rate of about 1.9 sheep-months/ha. A significant correlation is demonstrated between forage production of the winter range, lamb survival the following winter, and lamb production the following spring. This correlation indicates that a form of self-regulation of the sheep population is functioning.Key words: productivity of subarctic, semi-arid grasslands; Dall's sheep, carrying capacity, Kluane National Park, YukonMots clés: productivité dans les régions sub-arctiques, prairie semi-aride, mouflon de Dall, capacité de soutien, parc national Kluane, Yuko