  The physiographic provinces are areas of land form. The form of the land has a considerable effect on the temperature, humidity, drainage, weathering, soil, and other non-organic features that combine to produce the various life-zones and influence the distribution of mammals. One might therefore expect a close correlation of mammalian distributional areas with physiographic provinces. Although there is a correlation, it is not exact because the distribution of mammals is influenced also by certain other factors. Among these are historical factors and isolation by geographic barriers. Fig. 3. Mammalian distributional areas of Washington. A. Western Washington. B. Cascade Mountains. C. Northeastern Washington. D. Blue Mountains. E. Southeastern Washington. F. Yakima Valley. G. Columbian Plateau. The Cascade Mountains Province of Culver includes the Yakima Valley Area. This province contains two completely different mammalian distributional areas. The higher mountains possess a boreal, alpine fauna; the Cascade Range itself is called the Cascade Area The land west of the Cascades is separated into three physiographic provinces, the Puget Sound, Willapa Hills, and Olympic Mountains Province. The differences between the mammalian faunas of the Puget Sound and Willapa Hills provinces are slight. The Olympic Mountains possess a few species not found in the lower areas. The similarities of the faunas of the three provinces far outnumber their differences, and it seems best to consider them subdivisions of one distributional area. Fig. 4. Cascade Mountains in Chelan National Forest, looking southwest at Straight Ridge; Cataract Creek (Methow watershed) at left. (Forest Service photo. No. 4260.) The Okanogan Highland Province extends, from a physiographic point of view, west of the Okanogan River Valley. This valley, however, is a fairly efficient barrier to mammals. Thus the part of the state east of the Okanogan Valley and north of the east-west flow of the Spokane and Columbia rivers may be called the Northeastern Washington Distributional Area. The Columbia Lava Province includes the land both north and south of the Snake River. Since the Snake River serves as a barrier to some species, it seems better to term the area north of the Snake River the Columbian Plateau Area and that to the south the Southeastern Washington Distributional Area. The Blue Mountains Province and the Blue Mountains Distributional Area are the same. Fig. 5. Yakima Park (or Sunrise Park), elevation 6,000 feet, Mount Rainier, August 29, 1932. (Photo by 116th Photo Section, Washington National Guard, No. 014-36A-116.) Fig. 6. Columbia River at Hunters Ferry, Stevens County, Washington, April 15, 1940. (Fish and Wildlife Service photo by Victor B. Scheffer. No. 932.) Fig. 7. Blue Mountains, Umatilla National Forest, Washington, looking north-northeast across Al Williams Ridge to Tucannon River; 1933. (Forest Service photo, No. 4437.)
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