130 DOUGLAS FIR 



greater. In fact within its boundaries occurs the heaviest 

 measured rainfall in the United States, 100 inches in 12 months. 



The growing season is relatively long as compared with locali- 

 ties of the same latitude in the eastern part of the United States. 

 This is because the Pacific Coast climate is much modified by the 

 warm moist winds from the ocean. Hence there are no months 

 at Seattle when the mean temperature is below freezing. Taking 

 the type as a whole in the United States from northern CaHfornia 

 to the Canadian line the growing season is approximately six 

 months long. Temperatures too cold for tree growth are rare 

 from April thru September. 



As explained above this type is most abundant on the middle 

 slopes of the western side of the Cascade Range. This includes 

 the headwaters of the Illinois and Rogue rivers, the entire course 

 of the Umpdua, and the upper reaches of the Willamette and its 

 tributaries in Oregon. Between the States of Oregon and 

 Washington the Columbia River cuts thru the Cascade Range at 

 right angles but has very little effect on the distribution of the 

 type. Its northern tributary, the Cowlitz River, however, is 

 entirely within the type and the same applies to the other princi- 

 pal rivers of western Washington, the Chehalis, the Queniult, 

 the Skagit, and the Nooksak. All of these are characterized by 

 short, steep courses, with an abundance of water. 



As might be inferred from the steep to moderate slopes which 

 the type occupies the soil is fairly deep but yet not free from 

 outcrops and loose rocks. In origin it is partly glacial and in 

 Oregon and California residual or volcanic. 



While Douglas fir is the dominant species in the type it has 

 many associates on the sites which it does not possess the special 

 ability to preempt. For example, in the river bottoms in the 

 interior and along the seashore red cedar, Sitka spruce and 

 Lawson cypress share the ground with it. This is called the fir 

 cedar subtype. On the drier lower slopes above the shore line 

 and river bottom the fir is preeminent. Here it finds the deep, 

 loose soil, the long growing season and abundant rainfaJl which 

 it requires to reach its maximum development. Higher up, that 

 is, extending from 3000 to 4000 feet above sea level to 6000 or 



