Alternative silvicultural practices in irregular boreal forests: response of beetle assemblages

Abstract

In the process of implementing sustainable management in the eastern Canadian boreal forest, we tested two selection cutting methods and compared them with two widely used practices in the boreal forest: clearcutting with protection of the advanced growth and soils and irregular shelterwood cutting leaving small merchantable stems. We used old-growth irregular stands as references in comparing the impact of these silvicultural treatments on the diversity and abundance of beetles. Three groups were targeted: saproxylic flying beetles, epigaeic saproxylic beetles and epigaeic non-saproxylic beetles. A sampling design including 320 pitfall traps and 80 multidirectional flight-interception traps was deployed in 2007. A total of 26 906 beetles was captured including 407 taxa distributed among 52 families. We found that clearcutting with protection of the advanced growth and soils and irregular shelterwood cutting leaving small merchantable stems had a greater impact on beetle communities than both selection cuttings. Canopy opening as well as the presence of snags and downed woody debris appear as important attributes for several saproxylic and non-saproxylic species. Beetle communities in selection cuttings remained more similar to those found in controls; these silvicultural treatments are new tools to implement ecosystemic and sustainable management in irregular boreal forests.

Partial cutting in old-growth boreal stands: An integrated experiment

“…Cimon-Morin et al (2010a) found that, relative to uncut stands, all four treatments resulted in a decrease in basal area of snags. However, when snag abundance is expressed in terms of volume rather than basal area, Légaré et al (2011) found no reduction in snag abundance after selection cutting, but they detected a particularly strong decrease following CPRS (Table 3). The effect of the treatment on snags was only observed for the volume of recent snags.…”

“…Relative to uncut forests, selection cuts and CPPTM increased the richness of both epigaeic saproxylic and non-saproxylic epigaeic beetles (Table 5). Abundance of flying saproxylic beetles was reduced after CPRS and CPPTM (Table 6; Légaré et al 2011). Beetle species assemblages also differed among silvicultural treatments (Légaré et al 2011).…”

“…The effects of our silvicultural treatments on wildlife were assessed during the first three years after cutting by monitoring beetles, birds, small mammals, and Snowshoe Hare (Lepus americanus Erxleben) populations (Hodson et al 2010, Hodson 2011, Légaré et al 2011. Because these animals were studied in the main units without prior marking of trees to harvest, the results are informative about what could be expected in an operational context.…”

Abiotic and Biotic Soil Characteristics in Old Growth Forests and Thinned or Unthinned Mature Stands in Three Regions of Oregon

“…In ANCOVA without that site, OG had significantly higher mineralizable nitrogen than either mature stand (P = 0.015 for unthinned and 0.018 for thinned) (Table 2, Figure 5a). Because anaerobically mineralizable nitrogen largely reflects microbial biomass [18], we tested the hypothesis that differences between OG and mature stands were influenced by higher quality soil organic matter (SOM) in the former, a phenomenon seen in other studies (see discussion). We used two approaches, regression of AMN vs. SOM by stand type and ANCOVA of the ratio AMN/SOM.…”

“…In Alberta some litter dwelling beetle species have been shown to occur only in older forests [15,16]. But other studies have found that sensitive ground-dwelling beetles benefit from partial harvesting [17,18].…”