Vegetation change east of the Cascades in ponderosa pine forests. At lower elevations in eastern 

 Oregon and Washington, open, parklike stands of ponderosa pine were common before 1 900 (left). 

 Frequent, low-intensity fires kept fuels low and killed most seedlings and thin-barked firs, allowing the 

 pine to grow large and dominate. Fire suppression over the last 50 years changed these stands to 

 dense mixtures of ponderosa pine, Douglas-fir, and true fir (right). Plant and animal diversity 

 increased. Fires are now infrequent and more severe. Changes in species and over<rowding 

 have increased susceptibility of these stands to bark beetles and defoliating insects. 



Artwork by Beverly Swanson. 



Vegetation change east of the Cascades in mixed conifer forests. Mixed stands of Douglas-fir; 

 true fir; ponderosa, lodgepole, and white pines; and western larch are common in eastern Oregon 

 and Washington, particularly at middle and high elevations. Before the turn of the century (left), 

 disturbance by fire, insects, and disease was variable, creating mosaics of forest and openings. 

 Fire suppression over the last 50 years has led to increased forest density with more fuels, insect 

 outbreaks, and diseases (right). Fires are now more intense and destructive; homes built in or near 



forests are at increased risk. Artwork by Beverly Swansor\. 



looper, a pest of old-growth hemlock stands 

 that once killed trees on huge tracts of for- 

 est, now has much less host material avail- 

 able and is much less damaging. Injury to 

 dense young trees caused by bear and bark 

 beetles is increasingly common. On sites 

 once dominated by pine, outbreaks of insects 



that consume Douglas-fir and true fir foli- 

 age, and damage by root diseases and dwarf 

 mistletoes have increased in frequency and 

 severity. In some areas, fires are much more 

 devastating than before because of high fuel 

 loads. 



Overview — 10 



