280 THE STUDY OF PLANT COMMUNITIES ' Chapter X 



sempervirens), which, in pure stands, closely follows the limits of 

 the fog belt 71 to below San Francisco and fades out southward. 



If the ranges of the principal species of the Puget Sound area 

 are mapped, they appear in the form of a peninsula extending east- 

 ward across northern Washington and southern British Columbia 

 and expanding north and south on the west slope of the Rockies. 85 

 The coastal dominants extending into this area are Tsuga hetero- 

 phylla, Thuja plicata, and Pseudotsuga, which occupy a zonal posi- 

 tion between the normal Douglas fir and spruce-fir zones of the 

 Rockies. Although the importance of hemlock and arborvitae de- 

 creases eastward and Douglas fir increases, the zone remains dis- 

 tinctive largely because of the species peculiar to the forests de- 

 veloping after fire. The two principal successional trees are western 

 larch (Larix occidejitalis), which is endemic to the peninsula area, 

 and western white pine (Finns monticola) , which grows more 

 abundantly here than anywhere else. The presence of Abies 

 grandis in association with these species indicates the coastal af- 

 finities. 



Daubenmire 85 points out that this eastward overflow of coastal 

 species marks an area in which steady winds blow inland from the 

 coast, following a well-developed storm track, and thereby extend 

 the coastal climate far inland. This theory is supported by the 

 superior development of the coastal species in the peninsula on 

 westward slopes at intermediate altitudes and their occurrence in 

 the Rockies only in the storm path and west of the continental 

 divide. 



Broad-Sclerophyll Formation.— As the name indicates, major 

 species in both associations of this formation have thick, hard, 

 evergreen leaves. One climax is dominated by trees and termed 

 broad-sclerophyll forest. The other is a shrub climax called chap- 

 arral. Both reach their best development on the coastal ranges of 

 southern California, but their ranges extend from southern Oregon 

 southward through the coast mountains, as well as through the 

 Sierra Nevada foothills, into Lower California. Several of the 

 species are found on the east slopes of the Sierra, and some appear 

 in the desert woodland zone on the lower slopes of the Rocky 

 Mountains. 



The climate of the sclerophyll region is mild-temperate to sub- 



