Action: Fell trees in groups, leaving surrounding forest unharvested
Key messagesRead our guidance on Key messages before continuing
- Three studies evaluated the effects on mammals of felling trees in groups, leaving surrounding forest unharvested. Two studies were in Canada and one was in the UK.
COMMUNITY RESPONSE (0 STUDIES)
POPULATION RESPONSE (3 STUDIES)
- Abundance (2 studies): One of two replicated studies (including one controlled study and one site comparison study), in Canada, found that felling groups of trees within otherwise undisturbed stands increased the abundance of one of four small mammal species relative to clearcutting. The other study found that none of four small mammal species monitored showed abundance increases.
- Survival (1 study): A study in the UK found that when trees were felled in large groups with surrounding forest unaffected, there was less damage to artificial hazel dormouse nests than when trees were felled in small groups or thinned throughout.
BEHAVIOUR (0 STUDIES)
When timber harvesting or woodland management operations take place, trees may be clearfelled across a large area, thinned throughout the woodland or cut in patches, leaving surrounding forest unharvested. Felling in groups will produce a lower timber harvest than clearfelling but will leave more forest unaffected, which may help to sustain populations of some species. It will also affect less of the woodland area overall than does thinning of trees or selecting individual trees scattered throughout the forest to fell.
Supporting evidence from individual studies
A replicated, controlled study in 1994–1997 of Douglas-fir Pseudotsuga menziesii forest in British Colombia, Canada (Klenner et al. 2003) found that felling groups of trees within otherwise undisturbed stands increased southern red-backed vole Myodes gapperi abundance in some years relative to clearcutting but did not increase abundances of three other small mammal species. There were more southern red-backed voles in the third and fourth year after felling in group cut stands (7–14/stand) than in clearcuts (0.3–0.7/stand) but similar numbers between treatments in the first two years (group cut: 27–51/stand; clearcut: 13–34/stand). There were no differences between treatments for deer mouse Peromyscus maniculatus (group cut: 2–13/stand; clearcut: 6–21) or northwestern chipmunk Tamias amoenus (group cut: 1–8/stand; clearcut: 0.3–6/stand). There were fewer meadow voles Microtus pennsylvanicus in 20% group cut stands (1–3/stand) than in 50% group cut stands (0.8–4/stand) or clearcut stands (3–14/stand). Forest stands (20–25 ha) were partially harvested in winter 1993/94. Two each had 20% volume removed by cutting patches of 0.1–1.6 ha and 50% volume removed by cutting patches of 0.1–1.6 ha. Abundances across these stands were compared with that in two clearcuts of 1.6 ha. Small mammals were sampled by live-trapping at 2–4-week intervals, from May–October in 1994, 1995, and 1996 and from April–May 1997.
A replicated, site comparison study in 2006 in four forest sites in British Columbia, Canada (Ransome et al. 2009) found that harvesting trees in 1 ha blocks did not result in higher small mammal abundance compared to clearcutting large areas. The average number of red-backed voles Myodes gapperi caught in 1-ha cuts (19.0 individuals) was not significantly different to that caught in clearcuts (8.4 individuals). Numbers caught also did not differ significantly between felling types for dusky shrew Sorex monticolus (1-ha cuts: 34.0 individuals; clearcuts: 44.3 individuals), deer mouse Peromyscus maniculatus (1-ha cuts: 9.6 individuals; clearcuts: 11.6 individuals) or common shrew Sorex cinereus (1-ha cuts: 7.3; clearcuts: 7.0). A 1-ha area was harvested in each of four sites. These were compared with two large (>30 ha) clearcut areas. Trees were harvested in 1992–1993. Small mammals were live-trapped every three weeks in June–October 2006 (five sessions). Traps were operated for two nights and, if daytime temperatures were ≤25°C, the intervening day.
A study in 2003 of a forest in Worcestershire, UK (Trout et al. 2012) found that when trees were felled in large groups with surrounding forest unaffected, there was less damage to artificial hazel dormouse Muscardinus avellanarius nests than when trees were felled in small groups or thinned throughout. A lower proportion of artificial nests was damaged during large group felling (31%) than small group felling (62–66%) or thinning (73%). Non-native Corsican pines Pinus nigra were cleared from one third of the area of each of four plots (3 ha each) in a forest undergoing restoration to ancient woodland vegetation. Plot treatments, executed in late autumn/winter 2003, were clearance of small groups (12–14 trees) using chainsaws, clearance of small groups using a mechanised harvester, thinning throughout using a harvester and large group fells (c.0.4 ha each) using a harvester. Artificial dormouse nests comprised spheres of florists’ “oasis” (7–10 cm diameter) on the ground mimicking natural nests.
- Klenner W. & Sullivan T.P. (2003) Partial and clear-cut harvesting of high-elevation spruce-fir forests: Implications for small mammal communities. Canadian Journal of Forest Research, 33, 2283-2296
- Ransome D.B., Lindgren P.M.F., Waterhouse M.J., Armleder H.M. & Sullivan T.P. (2009) Small-mammal response to group-selection silvicultural systems in Engelmann spruce - subalpine fir forests 14 years postharvest. Canadian Journal of Forest Research, 39, 1698-1708
- Trout R.C., Brooks S.E., Rudlin P. & Neil J. (2012) The effects of restoring a conifer Plantation on an Ancient Woodland Site (PAWS) in the UK on the habitat and local population of the hazel dormouse (Muscardinus avellanarius). European Journal of Wildlife Research, 58, 635-643