Residual white spruce growth responses following partial cutting treatments in boreal mixedwoods
The boreal mixedwood forests of the Abitibi region of Quebec are often characterized by a canopy of trembling aspen with shade tolerant species such as white spruce and balsam fir in the subcanopy. In many cases, harvesting has converted complex mixedwoods into simpler, even aged forests. Due to the differences in regeneration and tree growth, the white spruce is often of small merchantable size classes when the trembling aspen is ready for harvesting. Partial cutting is a harvesting method where only some canopy trees are removed while others are retained in various proportions as residual trees. This remaining forest cover can maintain vital ecosystem services and meet silvicultural objectives such as increased timber production. It is thought that by removing some overstorey competition via partial cutting, the residual trees will experience an increase in growth rate. The purpose of this project is to evaluate the growth responses of residual white spruce trees in mixedwood stands where four different proportions of trembling aspen were removed by partial cutting ten years ago. Few studies have evaluated longer term growth responses of residual trees in trembling aspen-white spruce mixedwood stands. It is essential to determine the effectiveness of partial cutting treatments in terms of growth response, since it will likely only be considered successful on an ecosystem and economic basis if the growth responses of residual trees are positive.