SYLVICULTURE. 



This zone covers the major part of the forests of Oregon and 

 Washington and Xorthrn California. It is characterized by very 

 even annual temperature and high precipitations. The winter bald 

 Oaks are represented in Oregon by Quercus garryana (White Oak), 

 in Calif omia by Quercus Kellogii (Black Oak). Fraxinus Oregona, 

 Acer macrophyllum, Populus trichocarpa (Black Cottonwood, the 

 biggest Cottonwood of the world) occupy the bottom land along the 

 rivers; further Sorbus, Amelanchier, Crataegus, Prunus, Salix, Aes- 

 culus, Alnus, Acer, Platanus, Negundo, Betula. All of these latter 

 species unimportant commercially. 



In strict contrast with the Atlantic forest of the same zone, 

 the conifers rule in importance, foremost among them the Douglas 

 Fir (Pseudotsuga taxifolia) which stands temperature of 15 degrees 

 Faht. easily. Best development on west slope of Coast Range, In 

 the Rockies, it forms only summer shoots and short boles, owing 

 to shorter growing season and lack of atmospheric moisture. In 

 Colorado, Arizona, New Mexico occurs a gray variety. In the Sierras 

 it appears only as a dependent species. 



Pmus ponderosa (fellow Pine, Bull Pine). Height and timber 

 quality depend on proximity to Pacific Ocean. Optimum in Sierra 

 Nevada, where trees 300 feet high are frequently found. Very 

 heavy sap-wood. Name ponderosa undeserved. No tree of the 

 United States occupies a larger territory or shows greater adapta- 

 bility. 



Chamaecyparis lawsoniana (Port Orford Cedar) occupied only a 

 very small territory close to the Pacific Coast. Does not ascend 

 mountains to over 1,500 feet. Heavy shade bearer, splendid repro- 

 duction. 



Thuja plicata (Red Cedar of the West) up to 170 feet high. 

 Rare in California. Best development in Oregon and Washington 

 and Northern Idaho, where it occupies only the moister coves. Boles 

 very tapering; shade bearing; thin bark. 



Libocedrus decurrens (White Cedar. Bastard Cedar) on west 

 slope ol the Sierras at medium elevations, where the tree is mixed 

 with Abies concolor, Yellow and Sugar Pine. Regeneration easy, 

 often in places previously occupied by the Pines. 



Pinus lambertiana (Sugar Pine), a White Pine since it has five 

 needles in a sheath. Specific gravity even less than that of Eastern 

 White Pine (Pinus strobus). The biggest Pine of the world. Very 

 large cones. Optimum in Sierras at 5,000 feet elevation; occurs 

 often with Sequoia. Libocedrus, Abies concolor, Yellow Pine, Pinus 

 Jeffreyi. -Ihe latter, a very close relative to ponderosa and distin- 

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