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Ecological Framework of Canada
Ecoregions of Canada


This ecoregion, like most of the dry interior ecoregions of southern British Columbia, lies within the rain shadow of the Cascade Mountains to the west. The ecoregion is composed of long, rounded ridges of moderate relief and deep, wide valleys often occupied by large elongated lakes. This is one of the hottest and driest ecoregions in Canada. The climate is characterized by very warm to hot, dry summers and moderately cool winters with relatively little snowfall.  Summer drought, promoted by very warm temperatures, is the primary factor promoting the development of grassland vegetation below 700 m asl in valley bottoms. The mean annual temperature for the major valleys of the ecoregion is approximately 7.5°C with a summer mean of 16.5°C and a winter mean of -1.5°C. The mean annual precipitation ranges from 250 mm in the very dry valleys to 300-400 mm on the plateau surface. The climate varies with elevation and topography. Forest cover ranges from lodgepole pine with trembling aspen, white spruce, and Douglas-fir on the plateau to Douglas-fir and pine grass at moderate mid-slope elevations. Valley bottoms are covered by a parkland of scattered ponderosa pine in a matrix of bluebunch wheat grass and sagebrush and at lowest elevations by sagebrush, bluebunch wheat grass, blue grass and June-grass. Gray Luvisols and Eutric Brunisolic soils form on the common colluvial, morainal, and lacustrine deposits. Dark Gray, Dark Brown and Brown Chernozemic soils are usually associated with low-elevation valley bottoms such as along the Okanagan River. A wide range of representative wildlife includes California bighorn sheep, mule and white-tailed deer, black bear, cougar, coyote, bobcat, badger, blue grouse, and California quail (introduced). A number of southern species indigenous to the Great Basin of the western United States extend into this ecoregion including the pallid bat, sage thrasher and burrowing owl.  Reptiles include the western painted turtle, western rattlesnake, and western yellow-bellied racer, while amphibians include the Great Basin spadefoot toad, tiger salamander and western toad. Land use pressures are high in the valleys. Along with an increasing residential population and urban land uses, grazing, irrigated forage production, fruit orchards, water-oriented recreation, and tourism are common. Woodland grazing and some forestry take place at higher elevations. Approximately 40 000 ha of farmland occur in this ecoregion. The main communities are Oliver and Osoyoos. The population of the ecoregion is approximately 23 000.

This ecoregion is part of the Montane Cordillera ecozone.