Regeneration of Populus nine years after variable retention harvest in boreal mixedwood forests

Partial harvesting in boreal mixedwoods: A case for planned heterogeneity in industrial silvicultural prescriptions

“…related to these two factors (Pothier and Prévost, 2002;Frey et al, 2003), we believe that manipulation of relative basal area removal in partial cuts can be used to influence subsequent aspen regeneration, especially where initial aspen basal area is high. Gradowski et al (2010) reached a similar conclusion in their study of variable retention harvesting in the boreal mixedwoods of Alberta, Canada. Beyond this, the mean transition probabilities observed in this study reveal an antagonistic dualistic relationship between balsam fir and trembling aspen in southern boreal mixedwoods.…”

“…Based on previous experimental trials (Prévost and Pothier, 2003;Brais et al, 2004;Man et al, 2008;Prévost et al, 2010), we hypothesized that, even in an industrial context, an increase in the proportion of basal area removed would be likely to stimulate trembling aspen and, potentially, white birch regeneration, since both are shade intolerant species. We also postulated that the basal area of aspen before treatment would be positively correlated with the post-cut recruitment of the same species (Gradowski et al, 2010). Since previous studies have reported a negative relationship between coniferous cover and aspen regeneration (Calder et al, 2011;Smith et al, 2011), we hypothesized that abundant advance growth of balsam fir would have a negative effect on the recruitment of aspen suckers after treatment.…”

Early vegetation control for the regeneration of a single-cohort, intimate mixture of white spruce and aspen on upland boreal sites – 10thyear update

“…On the upland sites of the boreal forest, clearcutting is widely used to emulate fire in initiating stand renewal (Lieffers and Beck 1994). Following clearcut harvest, aspen frequently regenerates from root suckering with little or no subsequent silvicultural intervention (Lieffers et al 2003); stocking and density depend on the basal area, distribution and vigour of aspen in the parent stand, and the homogeneity of site conditions across the harvested area (Frey et al 2003, Gradkowski et al 2010. Relatively pure stands (i.e., > 80% of stand basal area to a single species) of spruce or pine may also be established on these sites through seeding or planting, followed by vegetation management when needed to reduce competition from aspen, tall shrubs, and herbaceous vegetation.…”

Effects of pre- and post-harvest spray with glyphosate and partial cutting on growth and quality of aspen regeneration in a boreal mixedwood forest

“…This system has been extensively tested across boreal forests (Prévost and Pothier, 2003;Brais et al, 2004;Haeussler et al, 2007;Man et al, 2008Man et al, , 2009Gradowski et al, 2010). In general, both sucker density and size decrease with increasing retention of overstory canopy (Frey et al, 2003;Prévost and Pothier, 2003;Brais et al, 2004).…”

“…In general, both sucker density and size decrease with increasing retention of overstory canopy (Frey et al, 2003;Prévost and Pothier, 2003;Brais et al, 2004). Comparatively, sucker density is more related to the amount of residual aspen, while their growth is more dependent on total residual canopy (Peterson and Peterson, 1992;Frey et al, 2003;Gradowski et al, 2010). In a partial cut with alternating harvest and leave strips (Comeau et al, 2005), the density and size of aspen suckers increases with the width of harvest strips (Groot et al, 2009;Lennie et al, 2009) until at least one tree height from the edge of leave strips (Groot et al, 2009), at which point regeneration is exposed to full sun.…”