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Providing evidence to improve practice

Action: Remove competing vegetation to allow tree establishment in clearcut areas Terrestrial Mammal Conservation

Key messages

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  • Three studies evaluated the effects on mammals of removing competing vegetation to allow tree establishment in clearcut areas. Two studies were in Canada and one was in the USA.




  • Use (3 studies): One of three studies (including two controlled studies and one site comparison study), in the USA and Canada, found that where competing vegetation was removed to allow tree establishment in clearcut areas, American martens used the areas more. One study found mixed results for moose and one found no increase in site use by snowshoe hares.

Supporting evidence from individual studies


A randomized, controlled, before-and-after study in 1991–1993 in a coniferous forest in Maine, USA (Eschholz et al. 1996) found that moose Alces alces did not use herbidice-treated forest clearcuts more than untreated clearcuts 1–2 years after treatment but foraging and sleeping signs were more numerous on treated than untreated clearcuts 7–11 years after treatment. Moose track quantity was similar between plots in the year before herbicide application (treatment plots: 0.07 track groups/ha; untreated: 0.08). One to two years after treatment, there were no significant differences in total number of track groups (treated: 1.6–3.0/km; untreated: 2.6–5.1), pellet groups (treated: 0.1–0.2/km; untreated: 0.2–0.4) or moose beds (treated: 0.03–0.05/km; untreated: 0.13–0.26), but there were fewer foraging tracks in treated plots (treated: 0.4 track groups/km; untreated: 1.0 tracks/km). After 7–11 years, there were more foraging tracks in treated (2.1–4.3/km) than untreated (1.1–1.8) plots and more moose beds (treated: 0.35–0.55/km; untreated: 0.12–0.31). There were no differences between treatments for total track groups (treated: 5.3–7.7/km; untreated: 3.4–4.2) or pellet groups (treated: 0.8–0.9/km; untreated: 0.4–0.5). Six of 12 clearcuts (18–89 ha), harvested 4.5–8.5 years previously, were herbicide-treated in August 1991. Six of 11 different clearcuts (21–73 ha) were glyphosate-treated 7–10 years before sampling. Treated plots in this second group averaged 19 years post-felling and, untreated plots, 16 years. Across all 23 plots, groups of moose foraging tracks and all tracks, moose beds and faecal pellet clumps were counted 5–7 times/year in January–March of 1992 and 1993, along 2-m-wide transects, 3–7 days after snowfall.


A replicated, controlled study in 1991–1996 of a coniferous forest in Québec, Canada (de Bellefeuille et al. 2001) found that, up to nine years after clearcutting, snowshoe hares Lepus americanus were not more numerous in replanted areas where competing vegetation had been removed than in naturally regenerating clearcuts. Data were not fully reported, nor were results of statistical analyses. However, hares seldom used removal plots. Only 5% of vegetation removal plots contained hare faecal pellets during any one survey and no preference for removal plots over those regenerating naturally was identified. Twenty-five sites (6–9 ha) were studied. Ten were clearcut in 1987, replanted in spring 1990, and competing vegetation removed in August 1992. In five sites vegetation was removed using brushsaws, and five using herbicide solution. Fifteen naturally regenerated sites, clearcut between 1987 and 1989, were controls. Hare faecal pellets were counted and cleared in 1 × 5-m plots, in June and September, 1991–1996.


A replicated, site comparison study in 2001–2002 of boreal forest stands in Ontario, Canada (Thompson et al. 2008) found that stands subject to herbicide treatment and tree planting after logging were used more by American martens Martes americana than were naturally regenerating stands. The effects of herbicide and planting were not separated in the study. Radio-tracked martens made greater use of herbicide-treated and planted stands than they did of naturally regenerating stands (data not presented). However, the live-capture rate of martens in herbicide-treated and planted stands (5.6 martens/100 trap nights) was not significantly different to that in regenerating stands (1.9 martens/100 trap nights). Stands were all 35–45 years old and located in a 600-km2 forestry area. Forest stands were either herbicide-treated and planted following logging or were left to regenerate naturally after logging. Martens were live-trapped in 2003–2007, and monitored subsequently by radio-tracking.

Referenced papers

Please cite as:

Littlewood, N.A., Rocha, R., Smith, R.K., Martin, P.A., Lockhart, S.L., Schoonover, R.F., Wilman, E., Bladon, A.J., Sainsbury, K.A., Pimm S. and Sutherland, W.J. (2020) Terrestrial Mammal Conservation: Global Evidence for the Effects of Interventions for terrestrial mammals excluding bats and primates. Synopses of Conservation Evidence Series. University of Cambridge, Cambridge, UK.