Canadian Forest Service Publications
Effects of precommercial thinning on the forest value chain in northwestern New Brunswick: Part 3 – Incidence of root and butt decay. 2013. Warren, G.R.; Baines, P.; Plamondon, J.; Pitt, D.G. The Forestry Chronicle 89(4):464–473.
Issued by: Atlantic Forestry Centre
Catalog ID: 35338
Availability: PDF (request by e-mail)
The Green River precommercial thinning(PCT)trials were established between 1959 and 1961 in naturally regenerating balsam fir (Abies balsamea [L.] Mill.)-dominated stands an average of eight years after overstory removal. Three nominal spacings of 4 ft (1.2 m), 6 ft (1.8 m) and 8 ft (2.4 m) were compared to an unthinned control in six replicate blocks. In the fall of2008, following completion of the ninth sequential evaluation of the study's 48 permanent sample plots, three of the six replicates were clearcut harvested; butt rot data were collected immediately afterwards. To date, forest management research and goals have focused on the benefits of PCT, such as increased tree size and merchantable volume, shorter rotation ages, and better stem form and uniformity. Comparatively little attention has been placed on negative aspects of PCT, such as the incidence and development of root and butt rots, and their impact on fibre yields and wood product values. Results from the Green River study provide evidence that PCT may increase the incidence of butt rot in balsam fir, with incidence proportional to thinning intensity (p < 0.01). We also observed incidence and volume of butt rot to increase with stem diameter (p < 0.05). The experiment suggests that factors such as stand age at time of thinning, and age at the time of harvest are important considerations when it comes to mitigating the impacts of butt rot through forest management.
Plain Language Summary
Precommercial thinning has been generally viewed as a positive silvicultural practice, but little attention has been given to potential negative aspects, such as the development of root and butt rots, and their impact on fiber yields and wood product values. These effects were examined using data from balsam fir stands (thinned to 4 ft., 6 ft. and 8 ft. spacings) in northwestern New Brunswick that were established between 1959 and 1961 and harvested in 2008. Results show that precommercial thinning may increase the incidence of butt rot in balsam fir, with incidence proportional to thinning intensity. Incidence and volume of butt rot were also observed to increase with stem diameter. However, actual volume losses due to root and butt rot were not found to be large enough to significantly detract from the increased merchantable volumes produced by thinning. The experiment suggests that factors such as stand age at time of thinning and age at the time of harvest are important considerations when attempting to minimize the impacts of thinning on losses due to decay.