Canadian Forest Service Publications
Partial harvesting in old-growth boreal forests and the preservation of animal diversity from ants to woodland caribou. 2011. Fortin, D.; Hébert, C.; Légaré, J.-P.; Courbin, N.; Swiston, K.; Hodson, J.; LeBlanc, M.-L.; Dussault, C.; Pothier, D.; Ruel, J.-C.; Couturier, S. Chapter 4, pp. 115-136, in E.B. Wallace, ed. Woodlands: Ecology, Management and Conservation, Nova Science Publishers, Inc., Hauppauge, NY, USA.
Available from: Laurentian Forestry Centre
Catalog ID: 32909
Current forest management must maintain biodiversity, an objective that has led to the rapid development of new forestry practices in recent years. However, empirical evaluation of the impact that these practices have on biodiversity has not kept the same pace. For example, small merchantable stems are now frequently protected during the harvest of old-growth boreal forests in eastern Canada. This silvicultural pratice (referred to as CPPTM in Québec) ends up protecting all stems with a diameter at breast height of 9-15 cm, and is therefore expected to maintain some of the irregular attributes of old-growth forest structure. Whether or not this approach is sufficient to maintain local biodiversity remains unclear. We evaluated the short-term impact of CPPTM harvesting mostly 2-3 years after logging, on a broad range of animal species differing largely in size and resource requirements. more specifically, we estimated the abundance, occurrence or local intensity of habitat use by ants, beetles, forest birds, snowshoe hare (Lepus americanus), moose (Alces alces) and woodland caribou (Rangifer tarandus caribou) in a boreal ecosystem. The 19,000 km2 study region is dominated by more than 270 year old stands with irregular structure mostly comprised of black spruce (Picea mariana) and balsam fir (Abies balsamea). Harvesting by CPPTM caused a 75-85% reduction in tree basal area. This decrease was sufficient to alter animal assemblages of all taxonomic groups. Ants and beetles associated with open areas were more abundant in CPPTM sites than in uncut stands. Conversely, species associated with mature forests were much lower in CPPTM than in uncut stands. Most birds associated with late-successional habitats were also less likely to be observed in CPPTM sites than in uncut stands. Snowshoe hares significantly decreased their use of harvested stands following CPPTM. Woodland caribou displayed a strong avoidance for CPPTM sites, while moose did not display any such aversion. CPPTM thus alters species assemblages, potentially reshaping trophic interactions with consequences for wildlife conservation. For example, moose did not avoid CPPTM cuts as much as they avoided stands that were harvested more intensively. Wolves that generally focus their hunting on moose might become attracted to CPPTM cuts, which could result in a higher concentration or even in a numerical response of wolves. At a regional scale, the outcome might lead to an increase in a local predation risk for woodland caribou, a threatened species. While CPPTM could still be useful in an ecosystem-based management context, our study shows that the protection of small merchantable stems is often insufficient for the short-terme maintenance of species composition which characterizes old-growth boreal forests.
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