18 A Study of the Vegetation of 
slopes of the higher mountains, such as Gold Hill and Cedar 
Mountain. More usually Douglas fir is mixed with yellow pine, 
it being only slightly less xerophytic than the latter. Such mix- 
tures of pine and Douglas fir frequently occupy large areas, the 
dominance of the latter indicating more mesophytic conditions 
(Fig. 25). 
The Larix-Abies associes forms the chief forests of the region. 
The western larch, Larix occidentalis, being more xerophytic than 
the white fir, Abies grandis, is usually the first tree to appear 
in the Pseudotsuga consocies. Mixed forests of Douglas fir and 
larch are not infrequent. These often show relict pines and in- 
vading white firs. Such exposed situations as Kamiak Moun- 
tain and Tekoa Mountains are especially representative (Figs. 37 
and 46). 
Likewise, large areas of sheltered mountain slopes are charac- 
terized by Larix and Abies in nearly equal abundance, with a 
considerable admixture of Douglas fir on the drier slopes and 
the appearance of cedar, Thuja plicata, in the moist ravines (Figs. 
26 and 27). Finally, in the deep ravines and most sheltered situa- 
tions, the giant cedar, representing the climax community of the 
region, appears. Often it forms pure stands over local areas, 
the low light intensity excluding other trees (Fig. 28). But more 
frequently it forms a mictium with the white fir and larch, Abies 
being the last to drop out. 
Each stage in forest succession is characterized by its particu- 
lar group of shrubs and herbaceous vegetation. The story of 
succession from one stage to the next is largely a story of in- 
creasing water content and of decreasing light. 
Perhaps this brief survey, together with a glance at the map 
(Fig. 1), will enable the reader to grasp the general vegetational 
regions. Following is an outline of the units of vegetation and 
their subdivisions in the order of their development. 
The developmental basis for the analysis of vegetation as set 
forth by Clements (2) is adopted here. Such a basis includes 
physiognomy, floristics, and habitat. For those who are not 
familiar with this basis of classification a few words of explana- 
tion may not be amiss. 
18 
