Vegetation change west of the Cascades. Western Oregon and Washington have had large changes 

 in forest vegetation over the past century. Before European settlement (left), trees and tree species 

 were more numerous; valleys contained many hardwoods; snags were common; and abundant woody 

 material contributed to periodic widespread fires. In the last 100 years (right), much of the forest in 

 the Puget Sound area and Willamette Valley has been converted to cities, suburbs, and farms; on 

 slopes and mountains oflJie Coast and Cascade ranges, many forests are younger, less diverse, and 

 more fragmented as the result of years of timber harvesting and replanting. Artwork by Beverly Swanson. 



landslides). Disturbances west of the Cas- 

 cades — predominantly wind storms and 

 wildfire — rarely removed all large woody de- 

 bris. Fires usually burned during periods 

 of extremely dry weather, and generally sev- 

 eral fires were required to consume the 

 wood. Snags, large trees, and unburned 

 patches survived. Wide age ranges in natu- 

 ral Douglas-fir forests suggest slow 

 recolonization because seed sources were 

 absent after large disturbances. 



The activities of the increasingly intensi- 

 fied timber industry also disturbed the for- 

 ests, but they did not mimic the natural dis- 

 turbances. Today's commercial forests are 

 younger, artificially dominated by even-aged 

 Douglas-fir, have few snags and logs, and are 

 more fragmented than less intensively man- 

 aged forests or wilderness. Erosion and soil 

 loss are chronic problems associated with 

 roads and annual logging operations rather 

 than periodic problems associated with 

 natural fires. 



East of the Cascades, disturbances ranged 

 from frequent, mild, ground fires at low el- 

 evations to occasional, intense, stand-re- 

 placing fires at high elevations. The sup- 

 pression of fire took away an important 

 natural means for removing fuels and thin- 

 ning stands, leaving sites dense with tree 



cover, particularly at low elevations. Fire 

 suppression and the selective harvest of 

 large pines transformied many open, park- 

 like stands dominated by large pines, into 

 dense, overcrowded stands of predominantly 

 Douglas-fir and grand fir. Riparian areas 

 were altered by grazing and loss of beaver 

 and pool-stabilizing logs. Grazing also af- 

 fected fire intensity and frequency and, as a 

 result, understory species and stocking. 

 High-elevation forests with longer natural 

 fire frequencies have been less affected by 

 fire suppression than were stands at low el- 

 evations. 



The forested area in Oregon and Washing- 

 ton faces increasing pressure from human 

 populations. Road building, urban develop- 

 ment, agriculture, power lines, and reser- 

 voirs have all taken their toll on forested 

 acres. At the same time as worldwide de- 

 mand for forest products is increasing, de- 

 mand for beautiful tree-covered recreation 

 and home sites is also rising. Conflicting 

 management objectives for wood products, 

 attractive living spaces, and forested recre- 

 ation sites will require resolution or compro- 

 mise. 



The ecological effects of these forest 

 changes are reflected in changes in the dis- 

 turbances that forests experience. Hemlock 



Overview — 9 



