Physically remove problematic plants

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

Effectiveness

48%
Certainty

35%
Harms

12%

Calculating overall effectiveness category

Background information and definitions

This section considers complete physical removal of problematic plants i.e. pulling up or digging up entire plants, or scraping living vegetation from the peatland surface. By completely removing plants, including roots where applicable, immediate regrowth will be prevented (although long-term recolonization is possible).

Physical removal can precisely target individuals of problematic species. Alternatively, it can involve broad clearance of dominant vegetation that outcompetes desirable plants or changes the physical environment to an undesirable state (e.g. acidification and nutrient enrichment by moss carpets on fens; Bootsma et al. 2002).

Key peatland types where this action may be appropriate: bogs, fens/fen meadows, tropical peat swamps.

Related actions: remove or bury upper layer of peat or soil, which will also involve removal of existing plants.

_{Bootsma M.C., van den Broek T., Barendregt A. & Beltman B. (2002) Rehabilitation of acidified floating fens by addition of buffered surface water. Restoration Ecology, 10, 112–121.}

Study locations

Key messages

Three studies evaluated the effects on peatland vegetation of removing problematic plants. All three studies were in fens.
Characteristic plants (1 study): One replicated, randomized, controlled study in a fen in Ireland reported that cover of fen-characteristic plants increased after mossy vegetation was removed.
Herb cover (3 studies): Three replicated, controlled studies in fens in the Netherlands and Ireland reported mixed effects of moss removal on herb cover after 2–5 years. Results varied between species or between sites, and sometimes depended on other treatments applied to plots (i.e. drainage or isolation from the surrounding bog).
Moss cover (3 studies): One replicated, randomized, controlled study in a fen in Ireland reported that removing the moss carpet reduced total bryophyte and Sphagnum moss cover for three years. Two replicated, controlled, before-and-after studies in fens in the Netherlands reported that removing the moss carpet had no effect on moss cover (after 2–5 years) in wet plots, but reduced total moss and Sphagnum cover in drained plots.
Overall plant richness/diversity (1 study): One replicated, controlled, before-and-after study in a fen in the Netherlands reported that moss removal increased plant species richness, but only in a drained area.

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, controlled, before-and-after study in 1989–1993 in a degraded floating fen in the Netherlands (Beltman et al. 1996) reported that the effect of moss removal on vegetation cover after two years depended on whether plots were previously drained. These results were not tested for statistical significance. All plots were initially dominated by mosses (moss cover: 83–96%; herb cover: <1–2%). Of two drained plots, one cleared of moss developed herb cover after two years (moss cover: 0%; herb cover: 76%) whereas one from which moss was not removed remained dominated by mosses (total moss cover: 99%; Sphagnum cover: 64%; herb cover: 3%). In two undrained plots, moss removal had no effect on vegetation cover. Plots with and without moss removal developed similar vegetation cover (total mosses: 93–96%; Sphagnum: 53–62%; herbs: 1–3%). In 1991, the moss carpet was cleared from two 16 m² plots in an acidified, nutrient-enriched fen. Two adjacent plots were not cleared. One cleared and one uncleared plot were also drained (by a ditch dug in 1989). In 1991 (before moss removal) and 1993, vegetation cover was recorded in six 1 m²quadrats/plot.
Study and other actions tested
Referenced paper
Beltman B., van den Broek T., Bloemen S. & Witsel C. (1996) Effects of restoration measures on nutrient availability in a formerly nutrient-poor floating fen after acidification and eutrophication. Biological Conservation, 78, 271-277.
A replicated, controlled, before-and-after study in 1991–1996 in a degraded floating fen in the Netherlands (Bootsma et al. 2002) reported that moss removal consistently reduced cover of black sedge Carex nigra and common cottongrass Eriophorum angustifolium, but that the effect on plant species richness and Sphagnum moss cover depended on whether plots had been drained. These results were not tested for statistical significance. After five years, black sedge and common cottongrass were less abundant in plots cleared of moss (sedge: absent; cottongrass: in 21–60% of quadrats) than uncleared plots (sedge: in 11–20% of quadrats; cottongrass: in 61–100% of quadrats). In a drained area, moss removal increased the number of plant species/plot (removal: 32–43; non-removal: 22–36) and Sphagnum cover (removal: 61–100%; non-removal: 41–60%). However, in an undrained area, moss removal reduced the number of species/plot (removal: 14; non-removal: 16) and had no effect on Sphagnum cover (removal: 21–40%; non-removal: 21–40%). Before intervention, plots contained 16 species and had 21–40% Sphagnum cover. In January 1992, the thick moss carpet was cleared from six plots in an acidified, nutrient-enriched fen. Six adjacent plots were not cleared. Half of the plots were in an area drained of acidic surface water and half in an undrained area. Between 1991 and 1996, cover of every plant species was estimated in quadrats covering 6–8 m² of each plot.
Study and other actions tested
Referenced paper
Bootsma M. C., van den Broek T., Barendregt A. & Beltman T. (2002) Rehabilitation of acidified floating fens by addition of buffered surface water. Restoration Ecology, 10, 112-121.
A replicated, randomized, controlled study in 2003–2006 in a soak (fen-like part of a bog) in Ireland (Crushell et al. 2011) reported that plots cleared of floating vegetation developed low cover of open water plant communities (if completely isolated from the surrounding bog) or high cover of fen-characteristic species (if partially isolated). No statistical tests were carried out. Three years after vegetation removal, completely isolated plots had 35% vegetation cover, comprised entirely of aquatic herbs (bryophyte, cottongrass Eriophorum angustifolium and sedge Carex rostrata cover all 0%). In partially isolated plots, vegetation cover was 85% (including wetland herbs: 40%; all bryophytes: 70%; Sphagnum moss 11%; cottongrass: 3%; sedge: 4%). In control plots from which vegetation was not removed, vegetation cover was 100% (including wetland herbs: 50%; all bryophytes: 95%; Sphagnum moss: 13%; cottongrass 3%; sedge: 3%). In October 2003, six 4 x 4 m plots were established. Floating peat and vegetation were removed from four random plots, of which two were then partially isolated from the surrounding bog (with porous plastic membranes) and two completely isolated (with impermeable rubber membranes). Two plots were not manipulated. In July 2004–2006, cover of every plant species was estimated in each plot.
Study and other actions tested
Referenced paper
Crushell P.H., Smolders A.J.P., Schouten M.G.C., van Wirdum G. & Roelofs J.G.M. (2011) Restoration of a terrestrialized soak lake of an Irish raised bog: results of field experiments. Restoration Ecology, 19, 261-272.

Please cite as:

Taylor, N.G., Grillas, P. & Sutherland, W.J. (2020) Peatland Conservation. Pages 367-430 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:

Peatland Conservation

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Actions	Effectiveness	Studies	Category
Implement biosecurity measures to prevent introductions of problematic species Action Link	No evidence found (no assessment)	0	Synopsis Link
Use cutting to control problematic large trees/shrubs Action Link	Unknown effectiveness (limited evidence)	2	Synopsis Link
Use herbicide to control problematic plants Action Link	Unknown effectiveness (limited evidence)	1	Synopsis Link