Empirical evaluations of reclamation success are critical for understanding the speed of ecosystem recovery and improving best practices. In this study, we provide a quantitative evaluation of the effectiveness of past (pre-1995) and current (2010) reclamation criteria in creating functioning forest ecosystems on former industrial sites in boreal Alberta, Canada. We compared ecological indicators of ecosystem recovery (vegetation structure and soil properties) on mineral surface leases (MSLs) certified to the pre-1995 or 2010 reclamation criteria with nearby reference areas recovering from harvest (CUT) or fire (FIRE) disturbances. Six CUT and FIRE sites were chosen to compare six 1995MSLs and five 2010MSLs. Averaging 8 years since reclamation, most of the 2010MSLs were characterized by many of the same vegetation structure and soil properties as the FIRE and CUT sites. The 1995MSLs tended to support more agronomic species, notably grasses and non-native forbs, and fewer shrubs, trees, and native forbs than CUT or FIRE sites. Sites with the greatest coverage of herbaceous species (native and non-native grasses as well as non-native forbs) were the most ecologically impaired sites, based on the extreme deviation from reference site conditions. Based on these results, 2010 reclamation criteria appear to be more effectively promoting ecosystem recovery on reclaimed industrial sites than the pre-1995 criteria. While this case study illustrated the potential benefits of straightforward changes to reclamation criteria in terms of including metrics around soil quality and conservation, woody stem requirements and native plant coverage, there is ultimately always room for improvement. For jurisdictions where the objective of the criteria is to restore a forest ecosystem, including criteria geared toward tree establishment would likely be of value in ensuring the speedy return to a forest canopy state. Adding criteria with measures of native plant species diversity may also be of utility as it is well understood that having plant diversity is also a beneficial metric in creating a more resilient vegetation community.
A significant portion of the harvested land base in western Canada is becoming old enough or entering a phase where thinning is a legitimate forest management option. A comprehensive review of the existing knowledge of commercial thinning (CT) treatments applied to pine and spruce-dominated stands in Alberta was conducted, with particular regard to the intensity, timing of interventions, method, and impacts on crop tree growth responses. Although the geographical focus of this review is Alberta, information on this topic is more complete in other areas of North America and Europe, where there is a long history of density management. In areas of eastern North America, our review revealed that CT from below, with tree removal levels from 27 to 43% of the basal area, could increase total merchantable wood produced from 11 to 60 m3 ha−1 over a rotation, depending on stand age and intensity of thinning. For Alberta conditions, and considering the risks, we conclude that commercial thinning basal area removal should be in the range of 25 to 40%, depending on a variety of factors such as species, wind firmness, and insect or disease incidence and risk. Thinning too aggressively and/or too late will increase the blowdown risk but the literature is fairly consistent in suggesting that live crown ratios should be >40% to maximize the chance of growth response and minimize the blowdown risk. In cases where stands are also threatened by stressors such as drought, wind, and insect or disease outbreaks, CT treatments likely offer the potential at limiting the overall risk, but localized knowledge and experience are critical. It is intended that the information presented may support ongoing and future research trials and growth and yield (G&Y) model development about potential CT treatments to apply and the likely results of practical application to commercial forestry.
A significant portion of the harvested land base in western Canada is becoming old enough or entering a phase where thinning is a legitimate option. A comprehensive review of the existing knowledge of commercial thinning (CT) treatments applied to pine and spruce-dominated stands in Alberta was conducted, with particular regard to the intensity, the timing of interventions, method and impacts on crop tree growth responses. Although the geographical focus of this review is Alberta, information on this topic is more complete in other areas of North America, and Europe, where there is a long history of density management. In areas of eastern North America, our review revealed that CT from below, with tree removal levels from 27 to 43% of the basal area could increase the merchantable wood volume from 11 to 60 m3 ha-1, depending on stand age and intensity of thinning. For Alberta conditions, and considering the risks, we conclude that commercial thinning basal area removal should be in the range of 25 to 40%, depending on a variety of factors such as species, wind firmness and insect or disease incidence and risk. Thinning too aggressively and/or too late will increase the blowdown risk but the literature is fairly consistent in suggesting that live crown ratios should be >40% to maximize the chance of growth response and minimize the blowdown risk. In cases where stands are also threatened by stressors such as drought, wind, and insect or disease outbreaks, CT treatments likely offer the potential at limiting the overall risk, but localized knowledge and experience are critical. It is intended that the information presented may support ongoing and future research trials and growth and yield (G&Y) model development with regard to potential CT treatments to apply and the likely results of practical application to commercial forestry.
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