Damage to residual trees by four mechanized harvest systems operating in small-diameter, mixed-conifer forests on steep slopes in northeastern Washington: a case study
2002
Camp, A.
Dense stands of small-diameter timber present unique challenges for land managers. In the inland West, trees in high-density stands often grow slowly and may be at risk to insects, diseases, and catastrophic fires. In 1996, the U.S. Congress recognized a need to address forest health issues and stimulate local resource-based economies in northeastern Washington. Funds were provided for "implementation and evaluation of controlled silvicultural treatment in designated, fire-generated, overstocked, small-diameter stands" (U.S. Congress House Report 104-625). As part of this Congressionally mandated research effort, four harvest units, each thinned to a 20 ft spacing using different harvesting technologies, were surveyed for damage prior to and following commercial thinning. Comparisons were made among the systems tested to assess damage to the residual stand. Overall incidence of wounds, incidence of wounds in different size and severity classes, and wound locations were compared. Each system performed better when judged by some criteria than by others. In general, cut-to-length processing caused less damage to the residual stand than whole-tree harvest; skyline yarding was less damaging than forwarder yarding. Some of the damage may have been a function of the silvicultural prescription and season of harvest. Appropriate silvicultural prescriptions and harvesting technologies can reduce wounding to acceptable levels.
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