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Providing evidence to improve practice

Individual study: Thinning of young Douglas-fir forests decreases density of northern flying squirrels in the Oregon Cascades

Published source details

Manning T., Hagar J.C. & McComb B.C. (2012) Thinning of young Douglas-fir forests decreases density of northern flying squirrels in the Oregon Cascades. Forest Ecology and Management, 264, 115-124


This study is summarised as evidence for the intervention(s) shown on the right. The icon shows which synopsis it is relevant to.

Thin trees within forest Terrestrial Mammal Conservation

A replicated, controlled study in 2007–2008 of a Douglas-fir Pseudotsuga menziessi forest in Oregon, USA (Manning et al. 2012) found that, 11–13 years after thinning, northern flying squirrels Glaucomys sabrinus were not more numerous in thinned than in unthinned stands. Flying squirrel density was lower in thinned (0.4 squirrels/ha) than unthinned (2.0/ha) stands. Among thinned stands, there were more flying squirrels in those that were lightly thinned with gaps (0.5/ha) than in heavily thinned stands (0.2/ha). The numbers in lightly thinned stands without gaps (0.4/ha) did not differ significantly from that in lightly thinned stands with gaps. Treatments were applied to 16 stands (15–53 ha), in four blocks (2.5–21 km apart), of 55–65-year-old forest, in 1994–1997. In each block, treatments were heavy thinning (to 125–137 trees/ha), light thinning (250–275 trees/ha), light thinning with gaps (as light thinning but also with 20% of the stand harvested leaving 0.2-ha gaps) and unthinned. Flying squirrels were surveyed using 100 traps/stand for four nights and three days, between late September and late November, in 2007 and 2008.

(Summarised by Nick Littlewood)