Commercial thinning of lodgepole pine in Alberta - 15-year growth response

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Millar Western Forest Products Ltd. operates two sawmills, a pulp mill, and associated woodlands operations near the community of Whitecourt in the Alberta foothills. There is an expected decrease in the short to mid-term timber supply in this region due to the impacts of fires and the mountain pine beetle outbreak. Commercial thinning is a potential option for increasing mid-term sawlog timber supply in these lodgepole pine forests by decreasing the time needed for individual trees to reach merchantable size. Commercial thinning will also produce merchantable timber immediately and potentially capture greater volume over the course of a rotation by harvesting the future mortality (i.e. capturing natural drain). However, there are many questions related to tree growth responses and mortality across different site types that must still be addressed before commercial thinning can be implemented operationally across the landscape. Millar Western operationally thinned 32 plots between 1996 and 2003 and has been remeasuring them along with unthinned control plots every five years. The purpose of this work is to quantify and explain the tree growth response (both individual tree and stand level) to commercial thinning in mature lodgepole pine stands of different ages and on different site types. The forest sector directly employs over 200,000 people in Canada and contributes $23 billion to the national economy. This important industry relies on a sustainable supply of growing wood fibre which is at risk of decreasing. Enhanced forest management practices, such as commercial thinning, offer a potential solution to this issue.