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Silvicultural practices in the subalpine forests of the true fir-mountain hemlock type should be aimed at natural regeneration because artificial reproduction of these forests poses serious problems. They include a short and undependable planting season, heavy winterkill of planted seedlings, limited supply of suitable planting stock, and slow growth of planted seedlings. Reliance on natural regeneration permits bypassing, or at least minimizing, some of these obstacles.

Production of seed is usually not a problem. Most upperslope species produce good cone crops at intervals of about three years, and light to intermediate crops almost every year. Advance reproduction is frequently present and should be utilized whenever possible. An added advantage is that advance reproduction of most species responds favorably to release. However, presence of pathogens and insects will dictate to some extent preference for species and thus cutting procedures.

Experience with silvicultural systems in the true fir-mountain hemlock type has been limited mainly to clearcutting. Sometimes adequate natural regeneration was obtained, but frequently natural regeneration has failed, especially on large clearcuts and near the upper limits of continuous forests. Considering this record, clearcutting appears to be the least desirable choice unless advance regeneration is present and can be preserved during logging and slash disposal. If clearcutting becomes necessary because of terrain or stand conditions, clearcuts should be kept as small as possible. However, keeping clearcuts small does not necessarily ensure natural regeneration. For instance, small patch cuttings on gentle topography sometimes create frost pockets which will prevent establishment of seedlings.

Experience with partial cutting systems in the true fir-mountain hemlock type is very limited, and recommendations have to be based mainly on theoretical considerations. The choice between shelterwood and selection cutting will depend on species composition and health of the stand. The shelterwood system will be preferable when the more light-demanding species predominate. If the balance is toward more shade-tolerant species, then selection cutting becomes an additional option. Natural regeneration in unmanaged stands of this type commonly occurs in "gaps" created by mortality of individual overstory trees.

Preliminary guidelines for determining density of residual overstory of shelterwood in upper-slope fir-hemlock stands have been published. Density of the residual stand should be reduced to the minimum at which an acceptable amount of regeneration will be obtained so that removal of shelterwood will not significantly damage reproduction. Grand fir and mountain hemlock require a considerable amount of overstory protection for survival during the first two years after germination. To obtain satisfactory numbers of grand fir seedlings, basal area of the residual stand probably should be at least 80 sq. ft. per acre. Seedlings of mountain hemlock are even more sensitive to microclimatic extremes than grand fir and seem to require overstory densities in excess of 100 sq. ft. per acre.

Balsam wooly aphid is a serious insect pest on subalpine fir and Pacific silver fir which often kills or seriously damages these two species of fir. Effective control of the insect is presently impossible, and therefore regeneration of subalpine fir and Pacific silver fir should be discouraged. In stands which contain subalpine fir and Pacific silver fir, scarification and relatively low density of the shelterwood should be used to favor other species not susceptible to the balsam wooly aphid. For the central Cascades of Oregon, suggested densities of residual overstory are indicated in Table 6.

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