Salvage logging and forest renewal affect early aspen stand structure after catastrophic wind

Abstract

Among the major natural disturbances that occur in the North American boreal forest, the effects of catastrophic wind are the least studied due to its infrequent occurrence, often in inaccessible areas, and lack of rapid research response. Most documented studies have been conducted in conifer or mixedwood forests and generally have not considered follow up forest renewal operations such as salvage logging followed by planting and tending. In 2006 after a severe wind disturbance in trembling aspen (Populus tremuloides Michx.) forest in northeastern Ontario, we established an operational study to investigate the effects of post-wind disturbance treatments on stand structure (residual live trees, snags, and downed wood) and early forest regeneration. The treatments were blowdown (B), blowdown followed by salvage logging (BS), blowdown followed by salvage logging, windrowing and planting (BSP), BSP followed by aerial spray (tending) with glyphosate 1year after planting (BSPT), and clearcut (C).The operational salvage logging removed about 55% of the 60 m3 ha−1 of the snags and 15% of the 390 m3 ha−1 of the coarse downed wood. The relatively low rate of salvage removal increased the abundance (density and stocking) of aspen regeneration and reduced moss cover, but did not affect average height of aspen suckers or the abundance (cover) of other vegetation types. The mechanical operations damaged much of the advanced growth of conifers (mostly black spruce and balsam fir (Abies balsamea (L.) Mill.) released by the wind. However, these stems were not sufficiently abundant to contribute significantly to the regenerating forest. Windrowing before planting slightly reduced the amount of area covered by downed wood, while the tending reduced broadleaf regeneration and the abundance of shrubs and increased conifer regeneration and the abundance of grasses. If the management objective is to renew aspen forests lost to catastrophic wind, salvage logging is a viable option to clear the site for regeneration. Forest renewal treatments, including planting and tending, are required when the management objective is conifer regeneration.