Pruning of lower branches of trees in plantations and in pre-commercially thinned stands can increase stand value by reducing the size of the knotty core, thereby increasing the amount and proportion of more valuable clear (knot free) wood. Dimensional lumber that is "clear" of knots and defects has historically commanded premium prices on world markets. Pruning may also improve log and lumber value by speeding the change from lower value juvenile wood to higher value mature wood, and by reducing stem taper
Pruning severity refers to the amount of live crown removed during the pruning operation. Tree growth may temporarily decline following live crown removal, and the magnitude of growth decline likely increases with pruning severity. Decisions regarding when to prune and how much live crown to remove must balance possible growth reductions with the desire to maximize the amount of clear wood production.
Pruning density refers to the relative number of trees pruned within a stand. Simple economics favours pruning only the crop trees that will survive until final harvest. However, pruning only some of the trees in a stand may put pruned trees at a growth disadvantage compared with unpruned trees, possibly even threatening their status as future crop trees.
Pruning is a very costly silvicultural treatment. The biological factors affecting the development of pruned stands must be thoroughly understood to ensure that the desired objectives are achieved and that investment returns are maximized. Experimental projects (EP's) testing a variety of pruning severities and densities have been established by the BC Ministry of Forests, Research Branch in coastal managed forests. The earliest pruning field experiment was established on Vancouver Island in 1930.
Experimental Projects - Coast
|Experimental Project #||Title||# Installation||Year Established|
|204-205||Thinning and Pruning: Demonstration Plots||1||1931|
|499||Practical Demonstration of Thinning and Pruning on a Farm Woodlot||1||1954|
|1065.01||Pruning young Coastal Douglas-fir||3||1990 - 1991|
|1065.02||Pruning Coastal western hemlock||3||1992|
|1065.03||Pruning western red cedar||1||1994|
|1065.04||Pruning Sitka Spruce||4||1994|
- 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., R. Negrave, and P.K. Ott. 2010. Effects of pruning severity on the growth of western redcedar after 12 years. In: A tale of two cedars. Int. Symp. on Western Redcedar and Yellow-cedar. C.A. Harrington (technical coordinator). U.S. Dep. Agric. For. Serv., Portland, Ore. Gen. Tech. Rep. PNW-GTR-828, pp. 103–108.
- de Montigny, L. and S. Stearns-Smith. 2001. Thinning and pruning coastal Douglas-fir near Chilliwack, B.C.: 8-year results. B.C. Min. For., Res. Br., Victoria, B.C. Exten. Note 56.
- de Montigny, L. and S. Stearns-Smith. 2001. Pruning density and severity in coastal western hemlock: 4 year results. B.C. Min. For., Res. Br., Victoria, B.C. Exten. Note 51.
- Finnis, J.M. 1953. Experimental pruning of Douglas-fir in British Columbia. B.C. Min. For., Victoria, B.C. Res. Note 24.
- Warrick, 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.