Trembling Aspen Stand Response 15 Years after Windthrow, Salvage Harvesting, and Forest Renewal

Abstract

Windthrow is a common occurrence in boreal forests, affecting wood supply and presenting regeneration challenges for forest managers. Salvage harvesting is often conducted afterwards to extract valuable wood and improve access for forest renewal activities. Research efforts, however, are generally limited to the effects of windthrow and salvage harvesting in the first few years following disturbance. In 2006, a catastrophic wind event occurred in a trembling aspen (Populus tremuloides Michx.) forest in northeastern Ontario. A field study was established with a range of silvicultural treatments from leaving after windthrow (W) to forest renewal treatments including windrow site preparation, planting, and herbicide release (WSPR). While the results of first 5-year assessment have been reported, the objective of the current study was to reassess treatment effects at 15 years post-disturbance, a stage of stand development that is more indicative of future forest conditions. Compared to the results of the earlier assessment, the 15-year assessment indicated that standing dead wood (snags) declined, whereas coarse downed wood did not change substantially over time. Post-disturbance salvage harvesting improved aspen regeneration in terms of density, stocking, and growth, but substantially reduced the proportion of conifers relative to windthrow only. Thus, salvage harvesting helped to sustain aspen composition, compared to other treatment options that increased proportions of pine and spruce trees from W to windthrow and salvage harvesting combined with windrow site preparation and planting (WSP), and from WSP to WSPR.