Evaluating Western Hemlock Stem Characteristics in Terms of Lumber Value

Authors

  • Robert M. Kellogg
  • William G. Warren

Keywords:

Western hemlock (<i>Thuja occidentalis</i> (Raf.) Sarg.), stem characteristics, lumber value, taper, eccentricity, sweep, crook, SAWSIM

Abstract

Of those stem characteristics studied, taper had the greatest influence on value for trees of a particular diameter. This effect acts primarily through change in volume with change in height at a fixed diameter. A relatively small component of this value difference results from the geometric effect of taper on sawing recovery of logs with differing top and butt diameters. Consideration should be given to determining the heritability of this factor and the establishment of acceptable taper limits in plus-tree selection. The other stem characteristics of sweep, crook, and eccentricity have a statistically significant but relatively minor influence on tree value where value is based on green volume recovery. It has not been possible to assess the effect on product value of compression wood associated with these stem characteristics. Based on the volume recovery effects, only the most extreme conditions of sweep may have a sufficient negative effect on value to warrant consideration as a selection criterion. Natural variation in stem eccentricity and major-axis rotation does not have an important negative effect on tree value. Similar to sweep, significant reductions in stem value resulting from crook appear, at least under optimized bucking conditions, to occur only under the most severe crook conditions. These value reductions amount to about 1% at the extreme levels of crook. "Rule-of-thumb" bucking results in a general decrease in product value of about 3%, but the differential with magnitude of crook is still about 1%.

References

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Published

2007-06-27

Issue

Number 4 / October 1984

Section

Research Contributions

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