12 NOKTH AMERICAN FAUNA [No. 55 



over 1,000 feet in vertical extent. The Arctic- Alpine Zone, of very 

 limited extent, caps most of the highest peaks well above all timber 

 growth and includes the dwarf alpine vegetation and a very few 

 species of birds and mammals. 



Tables 1 to 8 (pp. 31 to 53) show the life-zone distribution of the 

 mammals, reptiles, birds, and plants of the State. 



UPPER SONORAN ZONE 



The western arid division of the transcontinental Upper Austral 

 Zone covers most of the Columbia and Snake River Valleys of 

 eastern Oregon, and about half of the higher sagebrush plains area of 

 the State east of the Cascade Range. This part of the zone, with a 

 very limited rainfall and fairly uniform climate, can be treated as a 

 part of the arid Upper Sonoran, with many of the characteristics of 

 the Great Basin area, although the Columbia River Valley with 

 slightly more rainfall shows some peculiarities of note and a part of 

 it could be treated as belonging to the semiarid subdivision of the 

 zone. 



West of the Cascades limited areas of the zone are found in the 

 upper Rogue and central Umpqua Valleys. There is a narrow strip 

 along the Klamath River on the southern border of the State, and 

 east of the range a limited area occurs near the Klamath Lakes. 

 These semiarid valleys are marked by plants, birds, and mammals 

 that range mainly in northern California and clearly belong to the 

 California Valley subdivision of the zone. 



SEMIARID DIVISION OF UPPER SONORAN ZONE 



In the California Valley division of Upper Sonoran Zone in the 

 Umpqua, Rogue, and Klamath River Valleys the base level is low, 

 about 500, 1,200, and 2,000 feet, respectively. Only a narrow upper 

 edge of the zone shows in these valleys ; in the Umpqua Valley over 

 the flats and warm slopes in the Roseburg section, east of the Coast 

 Ranges, from 500 up to 1,000 feet; in the Grants Pass and Ashland 

 part of the Rogue River Valley on the open bottoms and warm slopes 

 from about 1,200 to 2,000 feet; and in the Klamath River Valley 

 from about 2,000 to 3,000 feet on the warm exposures. This is below 

 the Klamath Canyon which cuts off the zone from its higher and 

 more arid division around the Klamath Lakes. In all of these valleys 

 the Upper Sonoran elements are largely mixed and blended with 

 Transition species from higher levels, as inevitably occurs in so nar- 

 row a zone border, but still with sufficient character to indicate im- 

 portant climatic conditions favorable to southern species as well as 

 some of the less hardy crops. 



In these valleys are found the California jack rabbit, Rogue River 

 kangaroo rat, brown-footed wood rat, California meadow mouse, 

 white-toothed pocket gopher, gray fox, ringtail, Pacific pale bat, and 

 such birds as the valley quail, long-tailed jay, brown towhee, house 

 finch, bush tit, and long-tailed chat. 



The plants that indicate the zone in these valleys are found mainly 

 on the warm slopes and open flat country, while on cool or shaded 



