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Abstract Context Tree squirrels disappear when forests are clearcut. The American red squirrel (Tamiasciurus hudsonicus) and northern flying squirrel (Glaucomys sabrinus) may occupy retention forest patches on new clearcuts, but with conflicting results with respect to area, isolation, and edge effects of patches. Aims We tested the hypothesis that abundance, reproduction and body mass of T. hudsonicus and G. sabrinus populations would be greater in large than small patches of retention forest on new clearcuts. Methods We measured demographic responses of both sciurids from 2014 to 2016 in replicated (n = 4) treatments of four sizes (ha) of retention patches (means of 0.53, 1.50, 4.13 and 18.73) in south-central British Columbia, Canada. Key results Mean abundance of T. hudsonicus per sample line was similar among treatment sites, ranging from 0.7 to 1.7 (2014), 1.0 to 1.7 (2015) and 0.5 to 1.3 (2016). There was a positive linear relationship of mean abundance of red squirrels and increased basal area of conifers in the larger patches. Mean numbers of G. sabrinus were consistently highest in the 4.13 ha patch class in all years and appeared to decline over time in the other patches with fewest captures in the smallest patch size. There was a significant positive linear relationship between mean overall abundance of G. sabrinus and total density of overstorey trees. Conclusions Mean abundance, reproduction and body mass (red squirrels) of both sciurids were generally similar among patch sizes, and hence these results did not support the hypothesis. Implications Although our results were short-term, habitat quality was apparently sufficient to maintain the occurrence of T. hudsonicus across patch sizes ranging from 0.3 to 20.0 ha. Glaucomys sabrinus also occurred in several patches (13 of 16), albeit at low and variable numbers.

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.

Context A puzzling aspect of microtine population fluctuations is the damping out or collapsing of cycles over the last three decades, particularly in northern Europe. Occasional population fluctuations of Microtus may also have been damped out in temperate and boreal forests of the Pacific North-west of North America. One cause might be the presence of cattle (Bos taurus) grazing in forest habitats that offer summer forage. Aims We tested hypotheses (H) that abundance, population fluctuations, and demographic parameters of reproduction, recruitment and survival, of Microtus pennsylvanicus would be driven by understory plant productivity. Two predictions follow from this hypothesis: (H1) enhanced abundance and demography in fertilised stands, and (H2) reduced abundance and demography in stands with cattle grazing. Methods Study areas were located in 'grazed' and 'ungrazed' young forests in south-central British Columbia, Canada. Each study area had four replicate units of unfertilised and repeatedly fertilised stands. Herbaceous vegetation and meadow vole (M. pennsylvanicus) populations were sampled from 1993 to 2002. Key results Mean abundance of total herbs, grasses, and fireweed (Epilobium angustifolium) increased dramatically (8 to 34 times higher) with fertilisation in the ungrazed stands. Mean abundance of meadow voles was 3.1 to 8.5 times higher in the nutrient-enriched herbaceous vegetation in the ungrazed fertilised than grazed fertilised stands. Demographic variables also followed this pattern of abundance. Except for two years, mean abundance of meadow voles was similar between fertilised and unfertilised stands at the grazed area, with some degree of fluctuations generated in grazed stands. Thus, H1 and H2 were at least partly supported for M. pennsylvanicus in fertilised stands. Conclusions In high-quality habitats where cover and other attributes of vegetation are substantial enough to generate population increases and fluctuations of Microtus, grazing of vegetation by cattle or other livestock may indeed lead to potential collapse of fluctuations. Degree of grazing pressure would be crucial, but considering the widespread nature of grazing in the continuum of post-harvest forested sites in the Pacific North-west of North America, moderate to heavy grazing pressure is common. Implications Reductions in populations of microtines have serious consequences for predator communities and other ecological functions.

Context Southern red-backed voles (Myodes gapperi) disappear from clearcuts within the first year or two after harvest, at least in studies in coniferous and mixed forests of western North America. Post-harvest woody debris arranged in large piles and windrows supports populations of M. gapperi on clearcuts and may extend their persistence there. Aims To test the hypotheses (H) that for M. gapperi, (H1) population parameters of abundance, reproduction, and survival would be higher in windrow–forest than isolated windrow sites, and higher or similar to those in interior old forest sites; (H2) connectivity provided by windrow-forest structures will mitigate potential negative effects of clearcuts and abundance of M. gapperi will remain similar at the abrupt edge between forest and new clearcuts; and (H3) connectivity provided by windrow–forest structures will allow increased movements between both habitats. Methods Study areas were located in three forest ecological zones in southern British Columbia, Canada. Populations of M. gapperi were sampled from 2010 to 2012 in three types of habitats on new clearcuts: isolated windrows of woody debris, windrows attached to uncut old forest, and in uncut old forest. Key results Higher mean values of abundance and number of juvenile recruits of M. gapperi in the isolated windrow and windrow–forest sites than forest sites was contrary to our prediction for H1. In support of H2, we could not detect any differences in the mean number of captures among forest, edge and windrow sections of the windrow–forest sites, nor in the mean range length among the three habitat types. For H3, connectivity provided by windrow–forest structures may mitigate potential negative effects on abundance for M. gapperi at the abrupt edge between forest and new clearcuts. Conclusions and Implications Voles did not commonly move between the forest and windrow habitats, but did move readily within forest and within windrows. Substantial movement by M. gapperi within windrows suggested that this microtine will move along windrows and potentially use these paths of connectivity to cross clearcuts. If the prey base is present, windrow connectivity may enhance these open areas for small mustelids and other carnivores and help maintain abundance and diversity of some forest mammals on clearcuts.