'262 FOREST TREES OF THE PACIFIC SLOPE. 



to the small size of the trees, too little of the wood is available for commer- 

 cial use. 



Its dense thickets bordering rocky canyon streams and in gulches are very 

 helpful conservers of the scanty water supply in its range. 



Longevity. — Records of the ages attained by large trees are not available. 

 Young stems indicate rapid height and diameter growth ; those from 3 to 6 

 inches in diameter are from 18 to 30 years old. Further investigation of lon- 

 gevity is desirable. 



RANGE. 



British Columbia and probably Yukon and southward into Colorado, possibly to 

 northern New Mexico, southern Utah, Nevada, and central California ; westward to east 

 side of Pacific coast and Cascade ranges of Canada, Washington, and Oregon; east side 

 of northern California coast mountains and east side of Sierras of central California ; 

 eastward to Upper Saskatchewan River in Alberta to such outlying ranges as Bear 

 Paw and mountains at head of Musselshell River, in Montana, to mountains of North 

 eastern Wyoming, to Black Hills, South Dakota, and to northwestern corner of Ne- 

 braska. Generally in valleys and canyons. In Washington and Oregon, at 1,600 to 

 4,500 feet elevation ; at 5,000 to 10,000 feet in California Sierras ; at 4,000 to 6,000 feet 

 in Idaho: at 3,000 to 6,500 feet in Montana; at 5,000 to 9,000 feet in Colorado. 



Western Canada. — Throughout British Columbia, from Upper Fraser and Peace 

 rivers, and probably farther north, southward and eastward over Continental Divide to 

 eastern Rocky Mountain foothills in Alberta ; extending eastward, also, down Saskatche- 

 wan River to Edmonton. Not detected west of Pacific coast mountains. Locally noted 

 on mountains east of McLeods Lake, on north Saskatchewan River from Edmonton to 

 Victoria ; on Columbia River from Golden City to Selkirk summit. 



Washington. — Generally distributed, but not common on streams throughout eastern 

 half of State, and usually at 1,600 to 4, 200 feet elevation. Westward to Okanogan 

 River, Columbia River, in its north and south course below the Great Bend and to Yak- 

 ima River ; possibly also to eastern foothills of Cascades ; northward to Okanogan 

 River and Colville Indian Reservation and probably into Canada, and southward to 

 Blue Mountains. Locally noted as follows: Conconully, in Okanogan River Valley; 

 Wenache, on Columbia River; Wenache Mountains; Coulee City (Douglas County) ; Co- 

 lumbia River Valley and divide between Columbia and Yakima River, also on banks of lat- 

 ter stream; Umptanum Creek (tributary the Yakima); Spokane; Hangman Creek 

 Spokane County ; Pullman, and at Almota, near Pullman, also at point 10 miles south- 

 west of Pullman; Touchet River and Waitsburg (Blue Mountains). 



Oregon. — Throughout eastern part, west to eastern foothills of Cascades. Cascade 

 (North) National Forest, but not widely distributed. Locally noted in Columbia River 

 and Deschutes River valleys in northern Wasco and Sherman counties, the Columbia 

 Valley in Gilliam, Morrow, and Umatilla counties, and John Day Valley in northern Gil- 

 liam County. 



California. — From Siskiyou to Humboldt County and eastward to Surprise Valley, 

 east of Warner Mountains; southward, chiefly on east slope of Sierras to near their 

 south end. About Mount Shasta only at south end of Shasta Valley (northwest of 

 mountain), at 3,000 to 4,000 feet elevation. On east side of Sierras, common on all moun- 

 tain streams at about 4,500 to 0,000 feet, particularly those on west side of Owens Val- 

 ley : south to 10 miles north of Walker Pass (northeastern Kern County), south limit : 

 locally noted near Mono Lake, on Rock Creek (Mono County), at 4,500 to 7,100 feet, and 

 near Lone Pine (Inyo County). West side of Sierras, detected only in head basin of 

 South Fork of Kings River above Simpson"s Meadow, and in canyon of Bubbs Creek 

 (head tributary South Fork of Kings River) below a point 2 miles from head. 



The detailed range of this birch east of the Pacific region will be dealt with 

 in a later bulletin. 



OCCURRENCE. 



Borders of lower mountain streams and canyons in moist, gravelly, and rocky soils. 

 Forms long lines and patches of pure (thicket) growth. 



Climatic Conditions. — Similar to those of mountain mahogany. 



Tolerance. — Requires full top light ; its own moderately dense side shade produces 

 very slender, long, clear stems. 



Reproduction. — Abundant seeder. Seed of medium high germination, but of transient 

 vit'lity. Seedlings abundant in moist or wet washed mineral soil. 



