Juvenile Thinning

Terminology such as "juvenile thinning", "juvenile spacing", "spacing", and "precommercial thinning" generally refers to cuttings made in immature stands with the objective of reducing stand density in order to stimulate the growth of the remaining crop. Thinning affects the size and growth of individual trees and also the growth per unit area of the stand itself. The timing and intensity of juvenile thinning has large potential impacts on the amount, size, and value of timber harvested from managed forests and on biological and technical rotation lengths. By preventing, or alleviating, height repression, juvenile thinning in extremely dense stands may provide a more reliable estimate of site potential as represented by site index.

Several long-term experimental projects (EP´s) testing a variety of species and post-thinning regimes have been established by the BC Ministry of Forests, Research Branch in coastal and interior managed forests. The earliest thinning field experiments were established on Vancouver Island in 1929. Growth and yield data from thinning experiments is a vital source of data for treatment response predictions within managed stand growth prediction models. Older EP´s also provide data for checking a model´s long-term growth trends.


EP922 Installation 1 (Pl) unthinned control, age 22	EP922 Installation 1 (Pl) 1500 sph, age 22 - 15 years after thinning

Experimental Projects - Coast

EP	Title	# Inst.	Year Establ.
62 - 66	Sucessive Thinnings in a natural stand of Douglas fir	5	1929
204	Thinning and Pruning: Demonstration Plots	1	1931
205	Thinning and Pruning: Demonstration Plots	1	1931
283	Sucessive Thinnings in a natural stand of Douglas fir.	1	1929
368	The Adaptability of Tree Species to Forest Sites	1	1958
499	Practical Demonstration of Thinning and Pruning on a Farm Woodlot	1	1954
534	Spacing Trial of Douglas fir	1	1963
703	Extensive Studies of Fertlilizing and Thinning Coastal Douglas-fir and Western Hemlock	78	1971 - 1975
1097	Effects of Thinning and Fertilization on Growth and Yield of Coastal Sitka Spruce - Western Hemlock stands on the Queen Charlotte Islands	1	1991
1211	Callaghan Creek Squamish Forest District. Juvenile Spacing of Amabalis Fir in the Squamish Forest District. Amabalis fir and western hemlock.	1

Experimental Projects - Interior

EP	Title	# Inst.	Year Establ.
384/385	Thinning lodgepole pine in southeastern British Columbia	1	1952
511	Crop-tree thinning of western larch	1	1958
886.01d	Fertilizer x thinning interactions in lodgepole pine	1	1992
922	Juvenile-spacing trials in the BC interior	14	1982-1994
962	A comprehensive study to determine the effects of initial espacement and subsequent thinning on the growth and yield of lodgepole pine plantations	1	1987
1185	Effects of Sitka alder retention and removal on the growth of young lodgepole pine in the central interior of British Columbia	1	1995

Juvenile Thinning Publications

The National Research Council of Canada grants permission to individuals to download or print single copies of articles published by the NRC Research Press. Canadian Journal of Forest Research articles (starting with vol. 27) can be downloaded from the following website:
http://pubs.nrc-cnrc.gc.ca/cgi-bin/rp/rp2_vols_e?cjfr
B.C. Ministry of Forests publications can be downloaded from the following website:
http://www.for.gov.bc.ca/scripts/hfd/pubs/hfdcatalog/index.asp

Brockley, R.P. and P. Sanborn. 2003. Effects of Sitka alder on the growth and foliar nutrition of young lodgepole pine in the central interior of British Columbia. Can. J. For. Res. 33: 1761-1771. [PDF]

Brockley, R. and P. Sanborn. 2007. Assessing the effects of Sitka alder on the growth of young lodgepole pine in the central interior of British Columbia (SBSdw3): 9-year results. B.C. Ministry of Forests and Range, Victoria. Extension Note 79.

Johnstone, W.D. 1985. Thinning lodgepole pine. In Proc. Lodgepole Pine the Species and its Management, May 8-10, 1984, Spokane, WA, and May 14-16, 1984, Vancouver, B.C. D.M. Baumgartner et al. (editors). Washington State University, Cooperative Extension, Pullman, WA. pp. 251-260.

Johnstone, W.D. 2002. Thinning lodgepole pine in southeastern British Columbia (EP 384/385): 46-year results. B.C. Ministry of Forests, Victoria. Working Paper 63.

Johnstone, W.D. 2005. The effects of juvenile spacing on 7-year-old lodgepole pine in central British Columbia. West. J. Appl. For. 20: 160-166.

Johnstone, W.D. and D.M. Cole. 1988. Thinning lodgepole pine: a research review. In Proc. Future Forests of the Mountain West: a Stand Culture Symposium, September 29 - October 3, 1986, Missoula, Montana. W.C. Schmidt (editor). U.S. Dept. of Agriculture, Forest Service, Ogden, Utah. Gen. Tech. Rep. INT-243. pp. 160-164.

Johnstone, W.D. and F. J. van Thienen. 2004. A summary of early results from recent lodgepole pine thinning experiments in the British Columbia interior. B.C. Ministry of Forests, Victoria. Technical Report 016.

Johnstone, W.D., and F.J. van Thienen. 2006. A summary of 10- to 15-year results from Douglas-fir thinning experiments in the British Columbia interior. B.C. Ministry of Forests and Range, Victoria, B.C. Technical Report 027.

Omule, S.A.Y. 1985. Response of coastal Douglas-fir to pre-commercial thinning on a medium site in British Columbia. B.C. Ministry of Forests, Victoria. Research Note 100. (EP 554)

Sanborn, P., R. Brockley, and C. Preston. 2001. Effects of Sitka alder retention and removal on the growth of young lodgepole pine in the central interior of British Columbia. B.C. Ministry of Forests, Victoria. Working Paper 60.

Thompson, C.F. 1992. Crop-tree thinning of western larch in southeastern British Columbia: 30-year results. B.C. Ministry of Forests, Victoria. Research Note No. 110.

Warrick, G. 1948. Thinning and pruning of second-growth Douglas-fir in the coastal region of British Columbia. B.C. Ministry of Forests, Victoria. Research Note 13.

Warrick, G.C. 1979. Successive thinnings in a natural stand of Douglas-fir over a fifty year period. B.C. Ministry of Forests, Victoria. Research Note 87. (EPs 62-66, 283)

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