The seasonal development and yields of four major plant communities, of the important winter ranges of California bighorn sheep (Ovis canadensis californiana Douglas) in the Ashnola region, and their relation to basic climatic factors, were studied from May 1967 through December 1968. The four communities were: 1) Da bunch grass community dominated by Agropyron spicatum, 2) a sod grass community dominated by Poa pratensis, 3) a tree understory community dominated by Calamagrostis rubescens and 4) a half-shrub community dominated by Artemisia frigida. The climatic variables measured were: ambient air temperature, precipitation, including snow, evaporation and wind. Run-off, soil moisture and soil temperature were also measured. To reduce climatic variations between communities, all study sites were located at approximately the same elevation and were close to one another. Virtually all forage production in the four communities, in the growing seasons of both 1967 and 1958, occurred before the end of July. After this time, due to shattering, leaching and decay, decreases in herbage weights, ranging from 23 to 35 percent occurred by autumn, and further losses, ranging from 7 to 36 percent occurred over winter. The mean growth rates were essentially the same in the two years, but the cessation of growth two weeks earlier in 1968, resulted in lower production than in 1967. The dates spring growth commenced coincided closely with the dates that mean daily temperatures rose to 42 degrees Fahrenheit, whereas the dates growth ceased coincided closely with the dates that available soil water was exhausted. Both ambient air temperatures and soil temperatures remained favourable for growth until early autumn. The length of the growing season is the main factor determining net productivity of the Ashnola bighorn winter ranges; temperatures determine the beginning of the season and soil moisture deficits terminate the season. Moreover because the growing season is relatively short, climatic influences are important factors determining how much of the forage produced will remain potentially available for overwintering bighorn. / Land and Food Systems, Faculty of / Graduate

Habitat use by mule deer, particularly in relation to use by cattle and by California bighorn sheep on the bighorn winter-spring ranges of Flatiron Mountain was studied from January 1968 through November 1969. Observations were made of (1) food habits, (2) forage production and utilization, (3) the effect of spring and summer utilization on subsequent forage production and (4) spatial and temporal distribution of range use. The results indicate that competition for forage between the native ungulates, deer and sheep, is largely obviated by differential habitat use. This may point to long term evolutionary ecological niche specialization. Some competition for forage occurs for a short period in the early spring when both ungulate species seek succulent new grass, the supply of which is at first limited. Cattle use of the winter-spring ranges was excessive and the diets of cattle and the native ungulates are similar, with the exception that utilization of grass by deer was less. Range use by cattle contributed to intra-specific cattle-deer competition on the grasslands in the spring and cattle-bighorn competition on the grasslands during the winter. The study of spring range utilization indicated that deer use was not detrimental to the 1969 annual forage production in areas used by deer. Spring range utilization by bighorn or bighorn in combination with deer reduced the standing crop of forage produced on the Agropyron spicatum dominated winter-spring ranges. Sheep utilization on South Slope during the summer, when forage growth was declining, further reduced the amount of forage available to the wintering bighorn population. / Land and Food Systems, Faculty of / Graduate