Canadian Forest Service Publications
Effects of late commercial thinning at wide spacing on tree growth and lumber quality in jack pine (Pinus banksiana Lamb.) (Abstract only.) 2008. Duchesne, I.; Swift, D.E.; Turner, D.R., June 8-14, 2008, Koli, Finland. Natural Resources Canada, Canadian Forest Service, Canadian Wood Fibre Centre, Fredericton, N.B.
Issued by: Atlantic Forestry Centre
Catalog ID: 28791
Jack pine (Pinus banksiana Lamb.) has one of the widest distributions for a conifer across North America. Forests containing this species have great value for a variety of forest products. Commercial thinning has just recently become a more prevalent silvicultural prescription in naturally regenerated forests and plantations. Thus, little information is available on the long-term effects of intensified silvicultural management on tree growth and concurrent changes in wood properties of conifers in Canada. Commercial thinning, through modification of the spatial arrangement of trees, changes canopy light conditions, which influences tree crown development, tree growth and associated wood attributes. The aim of the study was to evaluate the long-term effects of late commercial thinning at wide spacing on tree growth, wood and lumber properties in a jack pine stand.
In the mid-1970's, a commercial thinning operation was conducted in a 40-year-old natural jack pine stand that originated from wildfires during the early 1930's. Although the harvesting method consisted of motor-manual and cable skidders, the harvest pattern simulates current mechanized harvest operations. Extraction trails were approximately 3 m wide, 20 m apart, parallel in orientation, and thus adhere to current commercial thinning regulations in New Brunswick and practices in eastern Canada. The spacing between the crop trees was approximately 2.7 x 2.7 m, removing approximately 50% of the basal area of the treated stand. Fifty percent basal area removal represents the maximum harvest intensity before wind throw concerns become apparent in New Brunswick.
A total of 85 trees, distributed across the DBH classes present, were sampled from the stand: 41 trees from the control area and 44 trees from thinned area. The logs were processed in a modern sawmill and the lumber produced was visually graded and tested for its bending stiffness (MOE) and strength (MOR). Results show that commercial thinning had a positive effect on lumber volume, lumber grade and lumber size recoveries. However, the bending properties and wood density of the lumber produced from the largest tree diameter classes (32 and 34-cm DBH) was lower in the commercially thinned area compared to the control area. The implication of these results on forest management decisions will be discussed.