Mountain maple and balsam fir early response to partial and clear-cut harvesting under aspen stands of northern Quebec

This study is a component of the Sylviculture et amenagement forestier ecosystemique project, which examines ecosystem-based forest management strategies in mixedwood boreal forests. Four harvesting treatments, one no-harvest, one clearcut, and two partial cuts ( 33% and 61% of basal area removed), were applied to even-aged aspen stands according to a complete block design. Mountain maple ( Acer spicatum Lamb.) and balsam fir ( Abies balsamea ( L.) Mill.) early response was examined to understand how they react to and interact with canopy opening. Only in clearcuts was maple's response ( increase in growth and density) sustained and significant. Balsam fir suffered from a very slight growth shock 1 year after harvesting in both clear-cut and two-thirds partial- cut treatments, but growth and vigour increased with canopy opening during the next 2 years. The first year following harvesting, balsam fir growth was negatively affected by understorey aspen and mountain maple. Our results show that the two-thirds partial harvesting treatment could speed up the conversion of pure aspen stands toward mixedwood.