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Commercial Thinning


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Commercial thinning is an intermediate harvest in immature stands, where trees have reached merchantable size, and all or part of the felled trees are extracted for useful products. As practised in British Columbia, commercial thinning is generally part of a clearcut silvicultural system. As such, the intent of commercial thinning is a partial harvest, not regeneration.

The traditional objectives of commercial thinning are to:

  • obtain wood volume or revenue earlier than the final harvest
  • improve the growth of residual trees
  • improve the quality of the stand by removing dead, diseased and deformed trees
  • capture some of the production that would otherwise be lost to mortality
  • obtain certain species and size classes for specialty products

In British Columbia, increased flexibility of wood flow at the forest level is a primary goal. Commercial thinning likely only provides marginal increases in the cumulative merchantable volume available from a stand over a rotation. However, commercial thinning can provide flexibility by redistributing harvest over time, thereby cushioning the effects of timber supply shortfalls caused by age-class imbalances in the timber supply. Commercial thinning can also provide harvest volume while meeting visual quality objectives and adjacency constraints.

Several commercial thinning experimental projects (EP´s) have been established by the BC Ministry of Forests, Research Branch in coastal and interior forests. Growth and yield data from commercial thinning experiments is a vital source of data for the calibration and validation of stand growth prediction models.


Experimental Projects - Coast

EP Title # Inst. Year Establ.
364 Commercial Thinning Experiment : North Arm Forest (Cowichan Lake) 1 1950
365 Thinning study in Douglas fir at Cowichan Lake Research Station 1 1950
388 Commercial Thinning in Western Hemlock 1 1952
418 Correlated Curve Trend Studies in Coastal Douglas-fir 1 1952
469 Thinning Experiment in Douglas-fir 1 1955
499 Practical Demonstration of Thinning and Pruning on a Farm Woodlot 1 1954
554 Correlated Curve Trends Thinning Experiments in Douglas fir 2 1959 - 1966


Experimental Projects - Interior

EP Title # Inst. Year Establ.
1184 The effect of commercial thinning on the growth and yield of interior Douglas-fir 1 1994


Commercial Thinning Publications

Joergensen, C. 1952. A commercial thinning experiment in Douglas-fir. B.C. Ministry of Forests, Victoria. Research Note 22.

Johnstone, W.D. 1997. The effect of commercial thinning on the growth and yield of lodgepole pine. In Proc. of a Commercial Thinning Workshop, October 17-18, 1996, Whitecourt, Alta. FERIC Special Report SR-122. pp. 13-23.

Omule, S.A.Y. 1988. Growth and yield 35 years after commercially thinning 50-year-old Douglas-fir. B.C. Ministry of Forests, Victoria. FRDA Report 21.

Omule, S.A.Y. 1989. Growth and yield 32 years after commercially thinning 56-year-old western hemlock. B.C. Ministry of Forests, Victoria. FRDA Report 29.

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Last Modified: 2007 APR 20.  Ministry contact: Frank van Thienen