Minimizing effects from, defoliators. Factors that favor survival of western spruce 

 budworm, Douglas fir tussock moth, and hemlock looper include stands with a predomi- 

 nance of host species, mature stands with large crowns and many nutritious reproductive 

 buds, and a multilayered canopy with host species in both the overstory and understory. 

 We recommend the following actions to unprove stand and host tree resistance to defoliators: 



• Maintain a diversity of serai forest stages with mixed host and nonhost species. 



• Where feasible, convert mixed stands of Douglas fir, true fir, and associated 

 species threatened by defoliators to stands composed primarily ofponderosa pine, 

 western white pine, and smaller proportions of western larch and Douglas-fir. 



• Maintain or manage for reasonable stocking density. 



• Maintain or manage for low vertical diversity. 



WEST OF THE CASCADES 



Healthy or not? — ^Natural forests in west- 

 ern Oregon and Washington have been reduced 

 and fragmented by urbanization and logging 

 in the last half-century. Widespread harvest 

 and replanting have reduced diversity of spe- 

 cies and structure in many areas. But, unlike 

 in east-side forests, changes in natural distur- 

 bance regimes are neither as widespread nor 

 as dramatic. The continued good health of 

 west- side forests is, however, still threatened 

 by the following changes: 



• Incidence emd damage by native forest patho- 

 gens, particularly root diseases, have in- 

 creased because of past forest management 

 practices. 



• Introductions of exotic pests have risen dra- 

 matically over the past century with increased 

 commerce, travel, and new people moving to 

 the Northwest. 



• Air pollution has worsened in the Willamette 

 Valley and Puget Sound areas with increased 

 population and industry. Ozone and other 

 pollutants can damage forests near and far 

 from pollutant sources. 



• Periods of drought have contributed to sus- 

 ceptibility of trees to attacks by insects and 

 pathogens. 



• Stresses on urban trees from air pollution, 

 mechanical injury, and poor maintenance, 

 have increased in many cities and towns. 



• Fire, wind, and disease are hazards to trees, 

 people, and homes in the urban-forest inter- 

 face. 



Solutions — Improving forest health in west- 

 em Oregon and Washington can be approached 

 from two directions: maximizing forest manage- 

 ment options and minimizing urban impacts. 



In forested areas on the west side, resource 

 managers and land owners have several options 

 for managing their forests to achieve long-term 

 forest health. Although restoration efforts over 

 large areas are not usually called for, changes 

 at a smaller scale can be beneficial. Some strat- 

 egies for forest health improvement in western 

 Oregon and Washington include the following: 



• Shift stands from single species to multiple 

 species to reduce insect outbreaks and prolif- 

 eration of diseases. Tradeoffs between maxi- 

 mizing timber production (traditionally with 

 even-aged, single-species plantations) and 

 minimizing insect and disease damage must 

 be examined. 



• Replant harvested or restored areas with seed- 

 lings grown from local seed sources or use 

 natural regeneration. Severity of diseases such 

 as Swiss needle cast is much less when trees 

 are adapted to the site. 



• Maintain a mosaic or mix of species and age 

 classes, preventing the whole landscape from 

 being dominated by uniform, highly suscep- 

 tible stands. 



The Future— 82 



