CHAPTER 3. DISTURBANCE AND FOREST 

 HEALTH IN WASHINGTON 



WASHINGTON COAST RANGE 

 (M242A),WESTERN CASCADES 

 (M242B),AND PUGETTROUGH 



(242A) 



Ecology 



Washington Coast Range— The Washing- 

 ton Coast Range extends from the Olympic 

 Mountains in the north southwards into Or- 

 egon. The Olympics, in the center of the Olym- 

 pic Peninsula, are unusually high, with eleva- 

 tions up to 8,000 feet; many of the major peaks 

 have active glaciers. Most other peaks are be- 

 low 4,000 feet. Flat, coastal lowlands are ex- 

 tensive in some areas. Dunes and bogs are 

 frequent along the coast, interspersed with 

 headlands of more resistant rock. 



Douglas-fir, western hemlock. Pacific silver 

 fir, and western redcedar predominate on the 

 higher mountain slopes. Forests of the lower 

 slopes and the coastal fog belt are dominated 

 by Sitka spruce and western hemilock. Pre- 

 cipitation is heaviest from November to April 

 and averages 60 to 240 inches annually, some 

 of the highest rainfall in the state. Severe win- 

 ter storms cause landslides and windthrow. 

 Stand-replacing fires burn at irregular inter- 

 vals of 90 to 250 years. 



The Puget Trough— The Puget Trough is 

 the northern extension of Oregon's Willamette 

 Valley. In the north, glacial activity has shaped 

 the land and influenced soil composition. Ele- 

 vation ranges from sea level to 2,000 feet. The 

 dominant vegetation in this region is western 

 redcedar, western hemlock, and Douglas-fir. 

 Riparian species include cottonwood, willow, 

 red alder, and bigleaf maple. Precipitation av- 

 erages less than in the Coast Range, from 25 

 to 60 inches, although intense winter storms 

 caused flooding at frequent intervals before 

 dams were built. 



Fires were commonly set by American Indi- 

 ans, trappers, hunters, and settlers. Early fires 

 created and maintained prairies that stretched — 

 intermingled with forests — from Tacoma to the 

 Columbia River. Today, many of the original 

 prairies have converted to forests. 



The Western Cascades — The western Cas- 

 cades region consists of steep mountain slopes, 

 highly dissected by large rivers. Elevation 

 ranges from near sea level at the Columbia 

 River to higher than 14,000 feet at the peaks 

 of the Cascade Range, although most of the 

 region is between 2,000 and 7,000 feet. Low 

 and mid elevations of the western Cascades are 

 dominated by Douglas-fir and western hem- 

 lock, with western redcedar, bigleaf maple, and 

 red alder common in drainage bottoms. As 

 elevation increases, mountain hemlock, sub- 

 alpine fir. Pacific silver fir, noble fir, and En- 

 gelmann spruce increase in abundance. West- 

 ern white pine is a minor stand component, 

 and whitebark pine is common along the crest. 



Precipitation ranges from 50 to 150 inches, 

 falling as rain and snow during October to 

 June. Summers are relatively dry. Fire peri- 

 odicity is extremely variable, ranging from de- 

 cades to centuries for major stand-replacing 

 fires. Volcanos erupt periodically. 



Washington — 45 



