Aspen groves that have been burned (left) can successfully regenerate by sprouting from roots of 

 burned, killed trees. Aspen declines and other species encroach v^ere fire is suppressed (right). 



Artwork by Beverfy Swanson. 



Cottonwood and aspen groves are disappearing. Two shade-intolerant hardwoods, 

 quaking aspen and black cottonwood, have declined as a result of cattle and sheep 

 grazing, an increase in big game, exclusion of natural fires, and encroachrrvent of conifers. 

 Regeneration of aspen requires fire to stimulate sprouting from roots and to eliminate 

 competition from conifers. Cottonwood depends on flooding to control competing vegeta- 

 tion and prepare suitable seed beds for regeneration; it also sprouts from roots after fire. 



These hardwoods are extremely important in riparian communities. They provide stream- 

 side stability, shading, water temperature regulation, and wUdlife habitat. Although not 

 abundant, quaking aspen is an important component of the eastern Oregon landscape. 

 Over the past century, the extent of aspen stands has declined in central Oregon alone by 

 about 50%. 



tral Oregon, an areawide infestation in the 

 1980s, covering more than 500,000 acres, 

 killed virtually all trees more than 8 inches in 

 diameter in pure stands of lodgepole. This out- 

 break ended in 1989, although some areas, on 

 about 50,000 acres along the Cascade Lakes 

 Highway near Bend, are still experiencing sig- 

 nificant mortality in lodgepole pine. 



In the Blue Mountains, the last major out- 

 break of mountain pine beetle was in the 

 1970s, affecting almost one million acres. Al- 

 though mountain pine beetle mortality has 

 decreased since the 1970s outbreak, lodgepole 

 stands will again stagnate and set the stage 

 for another beetle outbreak unless active man- 

 agement is initiated to control tree densities. 



Various Species 

 Some insects and diseases are of local or 

 diminishing importance. Root diseases 

 (annosus, black stain, and armiUaria) are locally 

 important on ponderosa pine in eastern Oregon. 

 Engelmann spruce, important in riparian 

 stands, is often infected by tomentosus root and 

 butt rot, which makes it susceptible to 

 windthrow and spruce beetle attacks after wind- 

 storms. The Douglas-fir tussock moth outbreak 

 that peaked in 1993, affecting 46,000 acres in 

 the Blue Mountains, subsided in 1995. Simi- 

 larly, the pandora moth outbreak on lodgepole 

 and ponderosa pine in central Oregon peaked 

 in 1994 and has collapsed in 1996. 



Oregon — 38 



