Remove understorey vegetation in forest

Overall effectiveness category Unlikely to be beneficial
Number of studies: 3
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How is the evidence assessed?

Effectiveness

10%
Certainty

50%
Harms

0%

Calculating overall effectiveness category

Background information and definitions

Through fire suppression, some forest areas have developed denser understorey vegetation than was the case under natural fire regimes. To reduce fuel loads and associated wildfire risk, understorey vegetation may be removed. Prescribed burning is one option for doing this, but the rapid habitat change that this causes, together with potential loss of food resources and shelter, could negatively impact forest floor mammals. This intervention, therefore, considers specifically manual or mechanical removal of understorey vegetation as an alternative to prescribed burning, and how this affects forest mammals.

Study locations

Key messages

Three studies evaluated the effects on mammals of removing understorey vegetation in forest. All three studies were in the USA.

COMMUNITY RESPONSE (0 STUDIES)

POPULATION RESPONSE (3 STUDIES)

Abundance (3 studies): Three replicated, randomized, controlled studies (two also before-and-after), in the USA, found that compared to prescribed burning, mechanically removing understorey vegetation growth in forests did not increase abundances of white-footed mice, shrews or four rodent species.

BEHAVIOUR (0 STUDIES)

About key messages

Key messages provide a descriptive index to studies we have found that test this intervention.

Studies are not directly comparable or of equal value. When making decisions based on this evidence, you should consider factors such as study size, study design, reported metrics and relevance of the study to your situation, rather than simply counting the number of studies that support a particular interpretation.

Supporting evidence from individual studies

A replicated, randomized, controlled, before-and-after study in 2001–2003 in North Carolina, USA (Greenberg et al. 2006) found that mechanically removing understorey vegetation in forest, to reduce fuel load and associated wildfire risk, did not increase white-footed mouse Peromyscus leucopus abundance compared to using prescribed fire. Mouse abundance increased across all treatments during the study, but the rate of increase in understorey removal plots (from 14 to 30 mice/plot) was not significantly different to that in prescribed burning plots (from 9 to 36 mice/plot). Plots (each >14 ha) were established in three blocks. In each block, understorey growth was mechanically felled in one plot in winter 2001–2002 and prescribed burning was carried out in a different plot in March 2003. Mice were live-trapped over 10 consecutive days and nights in July and August of 2001 (before management) and 2003 (after management).
Study and other actions tested
Referenced paper
Greenberg C.H., Otis D.L. & Waldrop T.A. (2006) Response of white-footed mice (Peromyscus leucopus) to fire and fire surrogate fuel reduction treatments in a southern Appalachian hardwood forest. Forest Ecology and Management, 234, 355-362.
A replicated, randomized, controlled study in 2003–2004 in North Carolina, USA (Greenberg et al. 2007) found that mechanically removing understorey vegetation in forest, to reduce fuel load and associated wildfire risk, did not increase shrew abundance compared to using prescribed fire. The number of shrews caught did not differ significantly between understorey removal plots and prescribed burning plots in the first year (understorey removal: 22 shrews/plot; burning: 15) or the second year (understorey removal: 7 shrews/plot; burning: 6) after treatments were applied. Plots (each >14 ha) were established in three blocks. Within each block, understorey growth was mechanically felled in one plot in winter 2001–2002 and prescribed burning was carried out in a different plot in March 2003. Shrews were surveyed using pitfall traps and drift fencing over 123 nights in 2003 and 125 nights in 2004.
Study and other actions tested
Referenced paper
Greenberg C.H., Miller S. & Waldrop T.A. (2007) Short-term response of shrews to prescribed fire and mechanical fuel reduction in a Southern Appalachian upland hardwood forest. Forest Ecology and Management, 243, 231-236.
A replicated, randomized, controlled, before-and-after study in 2001–2003 of a forest in California, USA (Amacher et al. 2008) found that mechanically removing understorey vegetation in forest, to reduce fuel load and associated wildfire risk, did not increase abundances of California ground squirrels Spermophilus beecheyi, long-eared chipmunks Tamias quadrimaculatus, brush mice Peromyscus boylii or deer mice Peromyscus maniculatus, compared to using prescribed burning. Changes in capture rates between before and after treatments did not differ significantly between understorey removal plots and fire plots for California ground squirrel (understorey removal: 2.6 to 11.0; fire: 4.2 to 7.6/100 trap nights), long-eared chipmunk (understorey removal: 0.7 to 2.4; fire: 0.7 to 1.7/100 trap nights) or brush mouse (understorey removal: 0.6 to 1.4; fire: 0.1 to 1.4/100 trap nights). Deer mouse abundance declined with understorey removal (from 2.0 to 1.2/100 trap nights) compared to an increase with fire (from 0.5 to 2.0/100 trap nights). Forests stands were 14–29 ha each. In four stands, 90% of understorey trees were removed in 2001–2002. Four different stands were burned in October–November 2002. Small mammals were live-trapped over nine consecutive days and nights in July–August of 2001 (pre-treatment) and 2003 (post-treatment).
Study and other actions tested
Referenced paper
Amacher A.J., Barrett R.H., Moghaddas J.J. & Stephens S.L. (2008) Preliminary effects of fire and mechanical fuel treatments on the abundance of small mammals in the mixed-conifer forest of the Sierra Nevada. Forest Ecology and Management, 255, 3193-3202.

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.

Where has this evidence come from?

List of journals searched by synopsis

All the journals searched for all synopses

This Action forms part of the Action Synopsis:

Terrestrial Mammal Conservation

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Remove mid-storey vegetation in forest Action Link	Likely to be beneficial	1	Synopsis Link