Pre-Commercial Thinning Research

Terminology such as “pre-commercial thinning”, "juvenile spacing", and "spacing" generally refers to cuttings made in immature stands with the objective of reducing stand density in order to stimulate the growth of the remaining trees. 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 spacing 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 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.

Experimental Projects – Coast

 
Experimental Project # Title # Inst. Year Established
62-66 and 283 Successive Thinnings in a natural stand of Douglas fir 5 1929
204-205 Thinning and Pruning: Demonstration Plots 1 1931
418 Correlated curve trend (CCT) in young Douglas-fir 1 1952
469 Thinning experiment in Douglas-fir 1 1955
534 Spacing Trial of Douglas fir 1 1963
554 Correlated curve trend (CCT) thinning experiment in Douglas-fir 1 1959
703 Extensive Studies of Fertilizing and Thinning Coastal Douglas-fir and Western Hemlock 78 1971-1975
1065.01 Thinning and pruning Douglas-fir 3 1990-1991
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  
1258 Fertilization and thinning on a Douglas-fir ecosystem 1 1971

Experimental Projects – Interior

 
Experimental Project # Title # Inst. Year Established
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

Pre-commercial Thinning Publications

  • 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.
  • 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. Min. For. Range, Victoria, B.C. Exten. Note 79. 
  • Darling, L.M. and S.A.Y. Omule. 1989. Extensive studies of fertilizing and thinning coastal Douglas-fir and western hemlock: an establishment report. Can. For. Serv. and B.C. Min. For., Victoria, B.C. FRDA Rep. 054.
  • de Montigny, L. and S. Stearns-Smith. 2001. Pruning density and severity in coastal Douglas-fir: 8 year results. B.C. Min. For., Res. Br., Victoria, B.C. Exten. Note 56. 
  • de Montigny, L. and R.J. de Jong. 1998. Effects of thinning and fertilizing mixed western hemlock–Sitka spruce stands. B.C. Min. For., Res. Br., Victoria, B.C. Exten. Note 28., Res. Rep. 13.
  • de Montigny, L. and G. Nigh. 2007. Density frontiers for even-aged Douglas-fir and western hemlock stands in coastal British Columbia. For. Sci. 53(6):675–682.
  • de Montigny, L. and G. Nigh. 2014. Growth, mortality and damage in fast growing Douglas-fir stands in coastal British Columbia twenty years after heavy juvenile thinning and moderate pruning at age nine. N.W. Sci. 88(3):206–218.
  • de Montigny, L., S. Le Noble, and G. Nigh. 2019. Effects of precommercial thinning after 15 years on growth and yield of western hemlock/amabilis fir stands in coastal British Columbia. Prov. B.C., Victoria, B.C. Tech. Rep. 119. 
  • de Montigny, L., P. Asante, S. Le Noble, and G. Nigh. 2019. The economic implications of pre-commercial thinning treatments in mixed western hemlock and amabilis fir stands in coastal British Columbia under varying cost and benefit assumptions and minimum harvest criteria. Prov. B.C., Victoria, B.C. Tech. Rep. 124.
  • Johnstone, W.D. 1985. Thinning lodgepole pine. In: Proc. Lodgepole Pine: the Species and its Management, May 8–10, 1984, Spokane, Wash., and May 14–16, 1984, Vancouver, B.C. D.M. Baumgartner et al. (editors). Washington State Univ., Pullman, Wash., pp. 251–260. 
  • 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. Min. For., Res. Br., Victoria, B.C. Tech. Rep. 016. 
  • 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 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. Min. For. Range, Victoria, B.C. Tech. Rep. 027.
  • Johnstone, W.D. and F.J. van Thienen. 2011. The effects of precommerial thinning on the growth and yield of lodgepole pine: 25 year results. B.C. Min. For. Range, Victoria, B.C. Exten. Note 103.
  • 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 Symp., Sept. 29–Oct. 3, 1986, Missoula, Mont. W.C. Schmidt (editor). U.S. Dep. Agric. For. Serv., Ogden, Utah. Gen. Tech. Rep. INT-243, pp. 160–164. 
  • Omule, S.A.Y. 1984. Results from a correlated curve trend experiment on spacing and thinning of coastal Douglas-fir. B.C. Min. For., Inf. Serv. Br., Victoria, B.C. Res. Note 93.
  • Omule, S.A.Y. 1985. Response of coastal Douglas-fir to pre-commercial thinning on a medium site in British Columbia. B.C. Min. For., Inf. Serv. Br., Victoria, B.C. Res. Note 100.
  • Omule, S.A.Y. 1990. Net basal area response 9 years after fertilizing thinned and unthinned Douglas-fir. Can. For. Serv. and B.C. Min. For., Victoria, B.C. FRDA Rep. 097. 
  • Omule, S.A.Y. 1991. Basal area response nine years after fertilizing and thinning western hemlock. Can. For. Serv. and B.C. Min. For., Victoria, B.C. FRDA Rep. 137.
  • McWilliams, R.G. and G. Therien. 1996. Fertilization and thinning effects on a Douglas-fir ecosystem at Shawnigan Lake: 24-year growth response. Can. For. Serv. and B.C. Min. For., Victoria, B.C. FRDA Rep. 269. 
  • Reynolds, N. and L. de Montigny. 2015. A 20-year analysis of incremental silviculture in mixed western hemlock–Sitka spruce stands in the Coastal Western Hemlock biogeoclimatic zone. B.C. Min. For., Lands Nat. Resource Ops., Victoria, B.C. Exten. Note 114.
  • 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. Min. For., Victoria, B.C. Work. Pap. 60. 
  • Stone, J.N. 1994. Extensive studies of fertilizing and thinning coastal Douglas-fir and western hemlock: an installation report. Can. For. Serv. and B.C. Min. For., Victoria, B.C. FRDA Rep. 227.
  • Stone, J.N., A. MacKinnon, J.V. Parminter, and K.P. Lertzman. 1998. Coarse woody debris decomposition documented over 65 years on southern Vancouver Island. Can. J. For. Res. 28:788–793. 
  • Warrack, G. 1948. Thinning and pruning of second-growth Douglas-fir in the coastal region of British Columbia. B.C. Min. For., Victoria, B.C. Res. Note 13. 
  • Warrack, G.C. 1979. Successive thinnings in a natural stand of Douglas-fir over a fifty year period. B.C. Min. For., Victoria, B.C. Res. Note 87.