THE COAST FOREST CLIMAX. 



215 



'Priest River, Idaho. 



While the best expression of this formation is along the coast, it extends to 

 the Cascades and covers their western slopes in typical form. East of the 

 Cascade Mountains, it passes into a broad transition forest which reaches to 

 the western slopes of the main range of the Rocky Mountains in northern 

 Montana and southeastern British Columbia. In the Cascade Mountains 

 of central Oregon, it is replaced by the montane forest, and becomes more and 

 more restricted to the coastal belt from this point southward. In similar 

 manner, it is replaced in central British Columbia by the montane forest, 

 though the coastal belt remains somewhat broad as a result of the numerous 

 islands and inlets. 



In altitude, the Coast forest extends from the sea-level as far as 3,000 to 

 6,000 feet in the Coast ranges and the Cascades. On the interior ranges, it 

 reaches its upper limit at 5,000 feet or lower. 



Unity. — The treatment of the Coast climax as a distinct formation is 

 abundantly justified by the regular association of the major dominants from 

 Alaska to California and from Washington to Montana. As already indicated, 

 five of these occur in Alaska, and five also in California, three of these, Tsuga, 

 Thuja, and Picea, being common to both extremes. The number of dominants 

 with a wide lateral range is even greater. Those which range from the Coast 

 to Montana are Tsuga heterophylla, Thuja plicata, Abies grandis, Larix occi- 

 dentalis, Pinus monticola, Pseudotsuga mucronata, and Pinus contorta, while 

 Picea engelmanni and Pinus ponderosa extend as dominants from the Cas- 

 cades to Montana. While there is a 

 marked change in the rank of the 

 dominants as the Cascade Moun- 

 tains are passed, this is clearly con- 

 nected with the differentiation of 

 associations. The ecological char- 

 acter of the forest remains essen- 

 tially the same toward the limits 

 at the east, except where more or 

 less subclimax dominants, such as 

 Pinus ponderosa and P. contorta, 

 become controlling. 



Geographically, the ferest be- 

 longs to the Coast and tho Colum- 

 bia Basin. At the higher levels, 

 the latter, like the former, is a re- 

 gion of relatively high rainfall and 

 low evaporation. The tempera- 

 ture relations are less uniform from east to west at least, but this is reflected 

 in the mixing of the two climaxes and the differentiation of a transition com- 

 munity (fig. 10). 



Relationship and contacts. — As the last statement indicates, the closest 

 relationship of the Coast forest is with the montane climax. They resemble 

 each other much in the size and vigor of the dominants and in the luxuriance 

 of the forest itself. This is reflected by the important role of Pseudotsuga 

 mucronata in both and the significant occurrence of closely related Sequoia 



4 

 3 

 o 



1 



Ql I I I I I I I II I I I I 



Fig. 10. — Monthly and total rainfall for represent- 

 ative localities in the associations of the Coastal 

 forest. 



30 in. 



