Boreal Owl (Aegolius funereus) and Northern Saw-whet Owl (Aegolius acadicus) breeding records in managed boreal forests

During the 2016 breeding season we monitored 169 nest boxes suitable for Boreal Owl (Aegolius funereus) and Northern Saw-whet Owl (Aegolius acadicus) in high-latitude (>55°N) boreal forests of northwestern Alberta affected by partial logging. Despite the large number of boxes deployed, the number of boxes used by Boreal and Northern Saw-whet Owls was small. Boreal Owls used nest boxes (n = 4) in conifer-dominated stands with three being in uncut blocks and the other in a 50% green tree retention cut-block. In contrast, Northern Saw-whet Owls used boxes (n = 4) in a broader range of cover types, breeding in boxes placed in stands with at least 20% post-harvest tree retention. Although both species successfully bred in the same landscape, Boreal Owls produced fewer eggs (mean = 2.5) and raised fewer young (mean = 0.5) than Northern Saw-whet Owls (5 and 2.25, respectively). Furthermore, our observed Boreal Owl egg production was lower than has been found for the same species nesting in nest boxes in different regions or forest types. In contrast, breeding parameters of Northern Saw-whet Owls were similar to that found in nest boxes in the eastern boreal region of Canada and in the southern part of its range.

Ecosystem Management of Eastern Canadian Boreal Forests: Potential Impacts on Wind Damage

Research Highlights: Windthrow can interfere significantly with ecosystem management practices. In some cases, their goal could still be reached but this may prove more complex in other cases, like the partial cutting of old-growth stands. In situations where windthrow is common without any human intervention, the use of partial cutting to maintain some stand structures may lead to a feedback loop leading to additional windthrow. Background and Objectives: Forest ecosystem management using natural disturbances as a template has become the management paradigm in many regions. Most of the time, the focus is on fire regime and effects. However, windthrow can be common in some places or can interfere with practices implemented in an ecosystem management strategy. This paper looks at interactions between ecosystem management and windthrow. Materials and Methods: The paper builds on three case studies looking at various elements that could be part of ecosystem management strategies. The first one looks at the impact of green tree retention, while the second one looks at the impact of reducing the size and dispersing clearcuts, and the last one examines the impact of a range of cutting practices in irregular old-growth stands. Results: Green tree retention leads to increased windthrow, especially when applied within mature even-aged stands. Reducing the size of clearcuts and dispersing them over the landscape also involves substantial windthrow along edges. Partial cutting in old-growth stands can lead to relatively high mortality, but part of it is not necessarily related to wind since it occurs as standing dead trees. Differences in the amount of damage with tree size and species have been found and could be used to reduce wind damage. Conclusions: Approaches to minimize wind damage in ecosystem management can be designed using existing knowledge. However, using windthrow as a template to design management strategies would prove more complex.

Green-tree retention and recovery of an old-forest specialist, the southern red-backed vole (Myodes gapperi), 20 years after harvest

Context Populations of many mammalian species are reduced as a result of clearcutting, despite the concurrent objectives of wood production and conservation of mammal diversity on cutover forest land. To help ameliorate this decline, green-tree retention (GTR) leaves large live trees after harvest to provide mature forest habitat and increase structural diversity of the regenerating stand. Aims To test the hypotheses (H) that, at 20 years after harvest, (H1) abundance, reproduction and survival of the southern red-backed vole (Myodes gapperi), as well as (H2) abundance and species diversity of the forest-floor small mammal community, would increase with the basal area (BA) and density of residual trees after harvest. Methods Small mammals were live-trapped in 2015–16 in replicated clearcut, dispersed retention, aggregated retention, patch cut and uncut forest sites in mixed forests of Douglas fir (Pseudotsuga menziesii var. glauca) and lodgepole pine (Pinus contorta Dougl. var. latifolia) in southern British Columbia, Canada. Key results Mean BA and density of overstory coniferous trees were significantly different at 20 years post-harvest, being higher on patch cut and uncut forest sites than on the clearcut and GTR sites. M. gapperi populations were significantly greater in aggregated retention and uncut forest sites than in the other sites, but demographic parameters were similar among sites, and therefore H1 was partly supported. Mean total abundance of small mammals differed significantly among sites, with the highest overall numbers occurring in the aggregated retention (16.2), clearcut (13.6) and uncut forest sites (11.9). Mean species richness and diversity were highest in the GTR and clearcut sites. Thus, H2 was not supported. Conclusions Recovery of M. gapperi in aggregated retention sites with 10m2 ha–1 BA of residual trees, as a group, occurred at 20 years post-harvest. Implications Aggregated retention of residual trees should help provide some habitat to conserve forest mammals on harvest openings, but successional development up to 20 years post-harvest may be required.