Apply fertilizer to trees

Overall effectiveness category Unknown effectiveness (limited evidence)
Number of studies: 3
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How is the evidence assessed?

Effectiveness

30%
Certainty

30%
Harms

0%

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Background information and definitions

Chemical fertilizers (nitrogen, phosphorus and potassium) are frequently applied to newly planted or regenerating trees. They increase soil fertility and may, therefore, enhance tree growth and nutritional content of foliage available to browsing herbivores. This could increase use of such areas by herbivores, leading to enhanced survival or abundance of these species.

Study locations

Key messages

Three studies evaluated the effects on mammals of applying fertilizer to trees. All three studies were in Canada.

COMMUNITY RESPONSE (0 STUDIES)

POPULATION RESPONSE (0 STUDIES)

BEHAVIOUR (3 STUDIES)

Use (3 studies): One of three replicated studies (including one controlled study and two site comparison studies), in Canada, found that thinned forest stands to which fertilizer was applied were used more by snowshoe hares in winter but not in summer over the short-term. The other studies found that forest stands to which fertilizer was applied were not more used by snowshoe hares in the longer term or by mule deer or moose.

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, site comparison study in 1999–2003, in two pine forest sites in British Columbia, Canada (Sullivan et al. 2006, same experimental set-up as Sullivan et al. 2006 and Sullivan et al. 2010) found that applying fertilizer to thinned stands of lodgepole pines Pinus contorta did not increase their use by mule deer Odocoileus hemionus or moose Alces alces. Mule deer use of stands did not differ significantly between fertilized and unfertilized stands in summer (fertilized: 185–700 faecal pellet groups/ha; unfertilized: 5–276) or winter (fertilized: 392–472 faecal pellet groups/ha; unfertilized: 111–261). Similarly, for moose, there was no significant difference in stand use in summer (fertilized: 13–87 faecal pellet groups/ha; unfertilized: 3–31) or winter (fertilized: 29–90 faecal pellet groups/ha; unfertilized: 21–66). Across the two sites, six forest stands in total were felled in 1978–1982 and lodgepole pine then regenerated naturally. The stands were thinned in 1993 (to 1,000 stems/ha). Three stands were then fertilized six times in 1994–2003. Faecal pellet groups were counted over two-week periods, five times in May and four times in October, in 1999–2003, in 55–145 plots/stands (plots were circles of 1.3 m radius).
Study and other actions tested
Referenced paper
Sullivan T.P., Sullivan D.S., Lindgren P.M.F. & Ransome D.B. (2006) Influence of repeated fertilization on forest ecosystems: relative habitat use by mule deer and moose. Canadian Journal of Forest Research, 36, 1395-1406.
A replicated, controlled study, in 1999–2003, of three lodgepole pine Pinus contorta forests in British Columbia, Canada (Sullivan et al. 2006, same experimental set-up as Sullivan et al. 2006 and Sullivan et al. 2010) found that adding fertilizer to thinned forest stands increased their use by snowshoe hares Lepus americanus in winter but not in summer. In winter, the average density of hare faecal pellets across fertilized stands (7,000–62,000/ha) was higher than that across unfertilized stands (1,400–28,000/ha). In summer, there was no significant difference in the density of hare faecal pellets between fertilized stands (800–21,000/ha) and unfertilized stands (600–11,000/ha). Within each of three site, blocks of commercially grown lodgepole pines were thinned to 2,000, 1,000, 500 and 250 stems/ha in 1993. Half of each stand was fertilized five times in 1994–2003. Hare faecal pellets on 5-m² permanent plots were counted in summer (May–September) and winter (October–April) 1999–2003.
Study and other actions tested
Referenced paper
Sullivan T.P., Sullivan D.S., Lindgren P.M.F. & Ransome D.B. (2006) Influence of repeated fertilization on forest ecosystems: relative habitat use by snowshoe hares (Lepus americanus). Canadian Journal of Forest Research, 36, 2080-2089.
A replicated, site comparison study in 2003–2008 of two lodgepole pine Pinus contorta forests in British Colombia, Canada (Sullivan et al. 2010; same experimental set-up as Sulliavn et al. 2006 and Sulliavn et al. 2006) found that repeated fertilization of thinned forest stands did not increase their use by snowshoe hares Lepus americanus, mule deer Odocoileus hemionus or moose Alces alces. Hare faecal pellet density and mule deer and moose pellet-group density did not differ between fertilized and unfertilized stands (data not presented). Naturally regenerated young lodgepole pine stands were studied at two sites. At each site, two stands were thinned, in 1993, to each of 2,000, 1,000, 500 and 250 stems/ha. Treatment stands were fertilized five times, in 1994–2003, using fertilizer blends which included 100–200 kg nitrogen/ha. Control stands were not fertilized. Mammal faecal pellets and pellet-groups were surveyed in 5-m² plots (55–145 plots/stand). Plots were cleared of pellets in autumn 2003. New pellets and pellet-groups were counted in spring 2008.
Study and other actions tested
Referenced paper
Sullivan T.P., Sullivan D.S., Lindgren P.M.F. & Ransome D.B. (2010) Long-term responses of mammalian herbivores to stand thinning and fertilization in young lodgepole pine (Pinus contorta var. latifolia) forest. Canadian Journal of Forest Research, 40, 2302-2312.

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

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This Action forms part of the Action Synopsis:

Terrestrial Mammal Conservation

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