Recovery Plan for the Northern Spotted Owl - DRAFT

Disases(Douglas-fir tussock moth and spruce budworm) which tend to attack Douglasfirand true firs could not easily build up in areas with frequent natural fireregimes because succession to the shade tolerant Douglas-fir and true firs didnot proceed and stands were typically dominated by pine species. On thewestern edge of the subregion, where fires are less frequent, and Douglas-firand true firs were more dominant, insect populations were historically higher.Douglas-fir beetle, fir engraver beetle, and Cooley spruce gall aphid populationswere generally low in areas with high fire freqency. Frequent fires also keptpopulations of mountain pine beetle, red turpentine beetle, and pine engraverbeetles at low levels because tree density was low and trees were under relativelylow stress. In areas with less frequent fires beetle populations wouldhave been larger.Like insects, diseases in this area also acted as an agent of stabilization innatural forests. Root diseases such as Annalarta probably removed stressedpines. Phellus weirli and H. annosum incidences were also lower because oflower populations of susceptible Douglas-fir and true firs. More root diseasesprobably occurred on the western than eastern edge of the subregion.Dwarf mistletoe infections were also lower in areas with frequent fires andslightly higher in areas with lower fire frequency. Natural rust populationswere lower and white pine blister rust was absent. Foliage diseases also wouldhave been low. Decay fungi would have been present, but pines tend to haveless butt rot and bole decay than later successional species such as Douglas-firand true firs. In older stands butt rots and decay fungi would increase inimportance.B. Management Effects on StandsAn extensive summary of forest health problems created by management (orlack of it) over this century is contained in the Blue Mountains Forest HealthReport "New Perspectives in Forest Health" (Gast et al. 1991). Although thisreport was prepared for two national forests east of the East Cascades subregion,as defined in this report, its summary of management impacts is applicableto this subregion. The report has garnered wide regional publicity.Fires were once common in the subregion, but effective fire suppression hasallowed the development under an overstory of larch, ponderosa pine, andDouglas-fir a thick understory of shade-tolerant grand fir (Figure F. 10). Firehazard increases, and fires which were once likely to be benign understory firesof low severity become high severity stand-replacement fires. High severityfires did occur in these low severity regimes (see Figure 3) but not at the scalethey now do. Where protection is successful, the moisture stress experiencedby the dense overstocked stands encourages spruce budworm attacks on thefirs. Although seldom fatal, such attacks weaken trees over several years andincrease the probability of successful attacks by bark beetles or root rots. TheBlue Mountains report recommended a large increase in prescribedunderburning to remove vulnerable species and reduce fire hazards (Gast et al.1991).With the exception of increased windthrow potential around edges of clear-cut,management has had little effect on wind in the East Cascades subregion.467