276 THE STUDY OF PLANT COMMUNITIES • Chapter X 



fore, largely by the timber-line pines and patches of lodgepole 

 pine. The montane and foothill zones extend to high altitudes, and 

 the vegetation is poorly developed. Finns jeffreyi is the important 

 species of the montane zone in which the open forest has little 

 resemblance to that of the west slope. The woodland forest is 

 practically absent. Although pifion- juniper occurs as a major zone 

 on the next ranges across the valley, it is not found on the east 

 slope of the Sierra except where an occasional high spur extends 

 eastward. The scrub zone is sometimes made up of oak and moun- 

 tain mahogany as in the Rockies, but is more often represented by 

 species from the desert below (Artemisia, Purshia, Chrysotham- 

 nus, etc.), which, especially on areas of disturbance or fire, may be 

 found high up in the montane zone as well as on the lower slopes. 



Pacific Conifer Forest.— This area parallels the coast from north- 

 ern tree limits in Alaska southward to central California. Coastal 

 mountain ranges with varying altitudes are included throughout 

 its length. The climate, tempered by the Pacific Ocean, is mild 

 and without extremes. Although Alaskan winters are cold, subzero 

 temperatures are uncommon along the coast. Southward, tempera- 

 tures are progressively less severe until, in Oregon and California, 

 frosts are rare. Precipitation is adequate to heavy (30 to 150 

 inches), and the humidity is always high, producing an extremely 

 favorable P/E ratio. The southern part is winter-wet with no 

 snow; here fog compensates for the summer drought. Northward, 

 the summer dry season shortens until, in Alaska, there is none. 

 Northward, too, there is an increase in the proportion of precipi- 

 tation falling as snow. In the higher mountains, it may be entirely 

 snow with falls as great as sixty to sixty-five feet a year. 



The coastal forest is primarily montane in character, although 

 ranging from sea level to altitudes of 5,000 feet. Only in the United 

 States, as in the Cascades, and for a short distance into British 

 Columbia does it include a subalpine forest. Here it is well de- 

 veloped, but the dominants are derived from the Rockies (Abies 

 lasiocarpa), the Sierra (Tsnga mertensiana) , as well as the coastal 

 forest (Abies amabilis, A. nobilis). Northward, the zone becomes 

 fragmentary or disappears entirely. 



Species of the coastal forest are most fully represented in the 

 general vicinity of Puget Sound, and the best development of the 



