Forest Investment Account (FIA) - Forest Science Program
FIA Project Y051266

    Coastal Stand Management Growth and Yield Field Experiments [2005 Project Description Only]
Imprint: Victoria, B.C. : B.C. Ministry of Forests, 2005
Subject: Forest Investment Account (FIA), Trees, Growth, Pruning, British Columbia, Wood, Quality
Series: Forest Investment Account (FIA) - Forest Science Program
Pruning can increase stand value by increasing the proportion of high-value knot-free (clear) wood and, in the case of western redcedar, by reducing butt swelling and fluting. Cedar bough harvesting and essential oil production may offset the cost of pruning and fertilizing cedar stands (pruning for bough production is essentially cost-free for licensees) and improve wood quality of the resulting stands. A pruning trial was initiated in a 14 year-old western redcedar stand on northern Vancouver Island in 1993 to investigate the effects of pruning severity on tree growth, epicormic branching and occlusion of pruning scars. This report describes the findings of this trial eight years after its establishment and discusses the opportunity for cedar oil production from green foliage pruning. Significant differences in initial tree size confounded the determination of pruning severity on tree growth. Covariate analysis was used to adjust least-square means for initial tree size and to determine treatment effects net of initial size differences. Pruning at the severest level of crown removal along 60% of the stem consistently resulted in significantly reduced dbh, height and volume growth over the experimental period. Pruning at moderate severities of 20% and 30% either did not reduce growth or slightly increased growth compared to unpruned controls. Pruning at 40% and 50% removal resulted in a slight loss of growth (2.4 dm3 loss per stem over eight years) compared to unpruned controls. Pruning treatments did not affect whole-stem taper (height/diameter ratio). Number and vigour of epicormic branches declined between 1997 and 2001. By 2001 epicormic branches in both pruned and unpruned treatments were generally of poor vigour. There tended to be more epicormic branches at pruning severities of 40% and above. Pruning scars were occluded in over 99% of pruned trees by 2001. On northern Vancouver Island, close to 15,000 litres of cedar leaf oil with a thujone concentration of 87% and higher, were produced over a 6 year period between 1998 to 2003. Factors that may limit the success of this opportunity are future market prices as determined by what may be decreasing demand and increasing supply of cedar oil.
Louise de Montigny.
Related projects:  FSP_Y062266FSP_Y073266
Contact: de Montigny, Louise, (250) 387-3295,

Updated August 16, 2010 

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