Canadian Forest Service Publications

The impact of early precommercial thinning of dense jack pine (Pinus banksiana Lamb.) stands on the mortality of thinned stems. 2014. Splawinski, T.B.; Gauthier, S.; Bergeron, Y.; Greene, D.F. For. Chron. 90:371-377.

Year: 2014

Issued by: Laurentian Forestry Centre

Catalog ID: 35711

Language: English

Availability: PDF (request by e-mail)

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Precommercial thinning of jack pine (Pinus banksiana) stands is a common silvicultural method to control stand density and growth in managed boreal forest stands. If employed too early, vigorous conifer re-growth can reduce the radial growth and potential yield of residual trees, thus requiring additional costly thinning treatments and extended rotation period. We examine thinned jack pine re-growth proportion as a function of remaining branch whorls on the stump of cut stems, and of thinning height following fire and salvage. Four salvaged and precommercially thinned stands in two forest fires that occurred in 1995 in the Abitibi-Temiscamingue region of Quebec were sampled. Significant relationships were identified between the number of branch whorls remaining on individual stems following precommercial thinning and the mortality proportion, and between the number of branch whorls remaining on individual stems following precommercial thinning and mean stump height. We suggest that precommercial thinning in dense jack pine stands be applied between 7 and 10 years following establishment at between 10 cm and 13 cm stump height. In addition, we identify various indicators that foresters can use on-site to better plan thinning operations.

Plain Language Summary

This study demonstrates that pre commercial thinning in jack pine stands where fire or salvage cutting has occurred should be done when the stands are between 7 and 10 years of age.

If the thinning is done before the stand is 7 years old, jack pine stems whose lower branches are still alive continue to develop. From these branches, the tree can develop up to four additional stems after the thinning operation. Therefore, rather than being reduced to promote the growth of residual trees, density increases considerably.

If the thinning is done after the stand is 7 years old, the lower branches begin to die from lack of light and cannot continue to grow. The researchers also recommend cutting trees between 10 and 13 cm above the ground so as to eliminate lower branches.
Pre commercial thinning is a common silvicultural treatment performed to control density and promote the growth of forest stands.