Effects of stem density of residual trees and season of cleaning on the performance of aspen regeneration 5 y post-treatment: the density of aspen regeneration (A, B); percent reduction in density between 2004 and 2008 (C, D); and maximum height of aspen regeneration (E, F). Bars represent the least square means; error bars represent the 95% confidence interval of the mean values. Different letters indicate significant differences according to Tukey’s multiple comparison test (p < 0.05); lowercase letters represent comparisons for Lac La Biche (LLB) and uppercase letters for Peace River (PR).