358 FOEEST TREES OF THE PACIFIC SLOPE. 



Useful with other shrubby trees in forming thick, retentive cover on the sides 

 of mountain streams and on moist slopes otherwise devoid of woody growth. 



Longevity. — Not fully determined. Probably short-lived. Two trees, respec- 

 tively 3 and 6 inches in diameter, were 10 to 22 years old. 



RANGE. 



Rocky Mountains to Pacific States and British Columbia, at the north from sea level 

 to 4,000 feet, at the south from 5,000 to 7,000 feet. 



British Columbia. — To northern part on coast and in interior as far as Cache Creek. 

 On Vancouver Island in isolated patches. 



Washington. — Common east of Cascades below 4,000 feet, and west of Cascades only 

 occasional on arid prairies, such as Whidby Island and Yelm Prairie. Noted in Washing- 

 ton National Forest at 1.100 to 3,500 feet, east of Cascades locally at Wenache (Chelan 

 County), on west bank of Columbia from Priest Rapids to Sentinel Bluffs in Saddle 

 Mountains, in gorge of Umptanum Creek (Kittitas County), on west slope of Divide be- 

 tween Columbia and Yakima rivers, in Yakima Canyon, at North Yakima, and Sunnyside, 

 on Upper Columbia, in Spokane Valley, at Rock Lake (head of Palouse River), Pullman 

 and Wawawai (Whitman County), along Snake River east of Pasco (Franklin County), 

 and in Blue Mountains. 



Oregon. — Chiefly to the east of Cascades, but also in arid parts west of Cascades. 

 Noted on Columbia River from northeastern Wasco to L T matilla County, on John Day 

 River in Gilliam County, in Cascade (North) National Forest, in Goose Lake National 

 Forest, and in Blue Mountains. 



California. — Whole State, except on seaboard, chiefly in foothills, at the north up to 

 about 3,500 feet, and at the south at 5,000 to 7,000 feet. Noted in chaparral of Klamath, 

 Modoc, and Warner mountains National Forests; at Y'reka (2,635 feet) (Siskiyou 

 County), Mount Shasta on its south slope above McCloud Mill, near Sisson (3,500 feet) 

 and at south end of Shasta Valley (3,500 feet) (Siskiyou County), Sacramento Canyon at 

 Shasta Springs (2,538 feet) (Siskiyou County), southern Trinity Mountains east as far 

 as hill between Whiskeytown and town of Shasta (Shasta County), and also locally noted 

 near Lewiston and on Canyon Creek (Trinity County) ; in Sierras in Plumas, Diamond 

 Mountain, Lassen Peak, Yuba, Tahoe National Forests, in Stanislaus National Forest in 

 general at 2,500 to 4,000 feet, locally noted in canyon of South Fork of American River 

 at 4,000 feet and on north slope of Mokelumne River at 2,500 feet, Lake Tahoe National 

 Forest in T. 17 N., R. 13 E., and in Yosemite Valley ; west border of Sierra National For- 

 est on dry pine hills, locally noted near Havilah (Kern County) at 3,150 feet. In coast 

 ranges noted in Napa Mountains, in San Francisco County, on Oakland Hills, Mount 

 Hamilton, in chaparral of Monterey National Forest in watershed of Nacimiento River, 

 in Santa Barbara National Forest in watersheds of Santa Maria, Santa Ynez, and Piru- 

 Sespe rivers, and in San Rafael Mountains, also in San Antonio and San Bernardino moun- 

 tains in upper portion of chaparral belt and in pine belt, in San Jacinto Mountains, at 

 5,000 to 7,000 feet on Fuller's Ridge and in Onstatt Valley, and in Laguna Mountains 

 at Campbell's ranch (5,500 feet), about 15 miles north of Mexican boundary. 



The distribution in the Rocky Mountain region will be described in a future 

 publication. 



OCCURRENCE. 



Lowest mountain slopes, ridges, benches, and borders of streams (most common), can- 

 yon bottoms ; less frequent on dry hill slopes. Usually in fresh or moist, rich gravelly or 

 rocky soils where it is largest ; shrubby in dry, poor soils. Forms dense thickets of pure 

 growth ; often more or less scattered, singly or in clumps, with Douglas fir, red and 

 mountain alders, aspen, black cottonwood, mountain maple, western serviceberry, bitter 

 cherry, chinquapin brush, and occasionally yellow pine. 



Climatic Conditions. — Similar to those of red alder and aspen. 



Tolerance. — Undetermined, but apparently intolerant of shade at any time, as shown 

 by its slender stems and small crown in dense stands, where it struggles for top light. 



Reproduction. — Very abundant seeder nearly every year. Seedlings plentiful in moist 

 litter, and advancing rapidly in old burns among willow-weed and low herbage. 



