Use herbicides after tree planting

Overall effectiveness category Unlikely to be beneficial
Number of studies: 4
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How is the evidence assessed?

Effectiveness

58%
Certainty

45%
Harms

0%

Calculating overall effectiveness category

Background information and definitions

Herbicides can be used to eliminate competing understory vegetation and to help the establishment of planted trees.

Study locations

Key messages

Two of three studies (including two replicated, randomized, controlled studies) in Swedenand the USAfound that using herbicide increased the sizeof planted trees. One study found no effect on tree size.
One replicated, randomized, controlled study in Sweden found no effect of using herbicide on frost damage caused to planted Norway spruce seedlings.

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 study in 1992-1995 in boreal forest in Sweden (1) found that applying herbicide increased the biomass of English oak Quercus robur seedlings. Dry weight (g/seedling) of stems (herbicide: 1.25-1.75; untreated: 0.45-0.50) and leaves (herbicide: 0.95-1.20; untreated: 0.25-0.35) were lower in untreated than herbicide plots. Data were collected in 1995 in herbicide and untreated (control) plots (25 m²) established in summer 1992 in each of six clearcut and six shelterwood (12.5 m²/ha basal area retained) blocks (cut in 1990). All plots were planted with oak seedlings in November 1992.
Study and other actions tested
Referenced paper
Löf M., Gemmel P., Nilsson U. & Welander N. (1998) The influence of site preparation on growth in Quercus robur L. seedlings in a southern Sweden clear-cut and shelterwood. Forest Ecology and Management, 109, 241-249.
A replicated, randomized, controlled study in 1988-1995 in boreal forest in Sweden (2) found no effect of herbicide treatment on frost damage to planted Norway spruce Picea abies seedlings. The percentage of seedlings with frost injuries was similar between treatments (site 1: 6-13%; site 2: 30-43%). Five blocks of four herbicide (glyphosate emulsion applied directly to the leaves of the ground vegetation whenever necessary through 1989-1993) and four control plots (4 × 4 m) were established in 1988 in each of two sites. Data were collected in each plot two growing seasons after planting of spruce seedlings.
Study and other actions tested
Referenced paper
Langvall O., Nilsson U. & Örlander G. (2001) Frost damage to planted Norway spruce seedlings—influence of site preparation and seedling type. Forest Ecology and Management, 141, 223-235.
A replicated, randomized, controlled study in 1999-2002 in temperate broadleaf forest in Illinois, USA (3) found that herbicide treatments during reforestation planting increased seedlings stem volume. The stem volume index was higher in herbicide treatments before and after seedling emergence (135 and 115 cm³ respectively) than in control plots (50 cm³). Stem volume index was calculated in 2002 for 40 ash seedlings (planted in 1999) in each control, after emergence (glyphosate) and before emergence (sulfometuron methyl) herbicide treatments (18 × 30 m) replicated in four blocks. Treatments were applied in 1999.
Study and other actions tested
Referenced paper
Baer S.G. & Groninger J.W. (2004) Herbicide and tillage effects on volunteer vegetation composition and diversity during reforestation. Restoration Ecology, 12, 258-267.
A replicated, controlled study in 1998-2006 in temperate forest in Louisiana, USA (4) found no effect of herbicide treatment on the height and basal area of planted longleaf pine Pinus palustris trees. Total cover of understory vegetation was lower in herbicide plots (herbicide: 21%; control 68%). In comparison, longleaf pine height (herbicide: 9.0 m; control 9.1 m) and basal area/tree (herbicide: 12,000 cm²; control 11,600 cm²) were similar between treatments. Data were collected in 2006 in three herbicide (application of triclopyr herbicide without intentionally treating herbaceous plants and vine in 1999, 2001, 2003, and 2005) and three control plots (untreated since 1998) of 0.066 ha. Each plots was planted with 196 longleaf pine seedlings in 1993-1994.
Study and other actions tested
Referenced paper
Haywood J.D. (2009) Eight years of seasonal burning and herbicidal brush control influence sapling longleaf pine growth, understory vegetation, and the outcome of an ensuing wildfire. Forest Ecology and Management, 258, 295-305.

Please cite as:

Agra, H., Schowanek, S., Carmel, Y., Smith, R.K. & Ne’eman, G. (2020) Forest Conservation. Pages 323-366 in: W.J. Sutherland, L.V. Dicks, S.O. Petrovan & R.K. Smith (eds) What Works in Conservation 2020. Open Book Publishers, 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:

Forest Conservation

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