EASTERN CASCADES (M242C) AND 

 OKANOGAN HIGHLANDS (M333A) 



Ecology 

 Eastern Cascades — The eastern Cascades 

 region in Washington consists of the eastern 

 slopes of the Cascade Range, which extends 

 north into Canada and south into Oregon. 

 Elevation ranges from near sea level at the 

 Columbia River to more than 10,000 feet in the 

 high mountain peaks. Precipitation patterns 

 are the key force for determining vegetation in 



Annosus root disease fungus produces spores that infect stumps; 

 the disease spreads from infected stumps to live trees by root- 

 to-root contact. 



the eastern Cascades. At high elevations that 

 receive more rain and snow, true fir, moun- 

 tain hemlock, and Douglas-fir forests predomi- 

 nate. At lower elevations, where moisture is 

 sparse, ponderosa and lodgepole pines grow. 

 Lodgepole pine is common on dry sites with 

 poor soils. Local areas of whitebark pine, white 

 pine, Engelmann spruce, and aspen are also 

 found in the eastern Cascades. Fire periodic- 

 ity is extremely variable. In the pine forests at 

 lower elevations, fire occurred at 10- to 15-year 

 intervals before fire suppression. Fire was less 

 frequent at higher elevations. 



Okanogan Highlands — ^The Okanogan 

 highlands are characterized by moderate 

 slopes and broad, rounded summits. Several 

 north-south rivers flow in this region, includ- 

 ing the Columbia, Okanogan, Colville, and 

 Pend Oreille Rivers. Vegetation patterns in the 

 Okanogan highlands are strongly influenced 

 by the east-west precipitation gradient. Pre- 

 cipitation averages 30 to 60 inches per year, 

 mostly as snow. Although ponderosa pine can 

 be found growing in pure stands, it is more 

 often found growing with other species in 

 mixed stands, including Douglas-fir, grand fir, 

 western larch, and lodgepole pine as major as- 

 sociates. At higher elevations, 

 Douglas-fir and true fir forests 

 predominate. Historical fire re- 

 gimes ranged from frequent, low- 

 intensity fires to infrequent, 

 high-intensity fires. 



Mixed Conifers 

 Root diseases continue to 

 increase in eastern Washing- 

 ton — ^Laminated root rot is wide- 

 spread throughout eastern 

 Washington forests. The disease 

 is increasingly common in the 

 mixed conifer stands of north- 

 eastern Washington, where 

 Douglas-fir and grand fir are 

 much more abundant in stands 

 once dominated by ponderosa 

 pine and western larch. Pine and 

 larch tend to be more tolerant of 

 the disease. 



Washington — 53 



