Minnesota’s spruce-fir forest type
Products and Uses
White spruce and balsam fir are used mainly for pulpwood and small sawtimber. Spruce-fir stands provide habitat for grouse, songbirds, white-tailed deer, moose, and a variety of small mammals.
White spruce often forms pure stands but may be associated with black spruce, balsam fir, aspen, and paper birch. Stands that develop following a major disturbance such as fire, insect attack, or clearcutting will be even-aged. Since white spruce and balsam fir are shade tolerant, uneven-aged stands will develop over time if no disturbances occur.
White spruce and balsam fir grow on a wide variety of soils, but white spruce does best on welldrained loams and clays. Balsam fir grows best on moist, well-drained sandy loam. The spruce-fir cover type commonly is found on well-drained lowlands where there is less competition from hardwoods.
White spruce and balsam fir regularly produce good seed crops and often are regenerated by natural seeding. Almost any moist seedbed is adequate, but bare mineral soil with some shade is best. The spruce-fir type can be managed under the selection system, but a shelterwood cut or strip clearcut less than 6 chains wide is recommended to produce even-aged stands. These smaller cutting blocks, when surrounded by seed-producing trees, permit good seed dispersal and reduce windthrow of surrounding trees. They also produce an age-class mosaic less susceptible to a spruce budworm attack.
Range of white spruce.
If natural spruce regeneration is desired, expose mineral soil. Full-tree skidding usually will expose enough mineral soil for natural seeding unless the ground is frozen.
When planting white spruce seedlings, first remove heavy slash concentrations. Plant 600 to 1,000 seedlings per acre. Transplant stock is preferred, but because of its high cost, 3-0 seedlings or container-grown stock often are used. Balsam fir is not often planted because of low market demand and relative ease of regeneration by natural seeding.
Beginning at age 25 to 30, thin the stand every 15 to 20 years, to a basal area of about 90 square feet per acre. Follow the stocking chart for evenaged spruce-balsam fir stands in Appendix 0-7. White spruce may be grown on 80- to 120-year rotations for sawlogs. Harvest the balsam fir and aspen in the stand when they mature (age 60) to encourage spruce growth.
The spruce budworm is the major insect pest of the spruce-fir forest type. Budworm survives best on older trees. To minimize damage, manage fir on a 40- to 50-year rotation, keep large forest areas well diversified by age class, and maintain a high spruce and hardwood component. Insecticides may be warranted in areas where budworm attack is prolonged.
Heart rot and root rots are major diseases. They can be minimized by keeping budworm from killing the tops of trees (insecticides may be required) and avoiding scarring residual stems during intermediate cuttings.
Windthrow can be a serious condition, especially on wet, shallow soils. Minimize windthrow by maintaining a well-stocked, vigorous stand.
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