Cover peatland with organic mulch (without planting)

Overall effectiveness category Unknown effectiveness (limited evidence)
Number of studies: 2
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How is the evidence assessed?

Effectiveness

40%
Certainty

30%
Harms

5%

Calculating overall effectiveness category

Background information and definitions

Peatland vegetation may be killed by hot, dry conditions on bare peat surfaces (e.g. Sagot & Rochefort 1996). Organic mulches (e.g. straw, grass cuttings or shrub roots) can be placed on the peatland surface to stabilize temperatures and humidity, and provide shade. This may create a more hospitable environment for establishment and growth of peatland vegetation (Good et al. 2009). Typically, mulch is applied sparsely enough that some light can still reach the peat surface. Caution: Mulches may contain seeds of undesirable plants. Sterilization before application can kill these.

This section considers the effect of adding mulch without adding living vegetation. The mulch is intended to help existing vegetation e.g. remnant moss patches, or seedlings that germinate from seeds already in the peat.

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

Related actions: cover peat with something other than mulch e.g. plastic sheets or shade cloths; add mulch after planting.

_{Good R., Wright G., Whinam J. & Hope G. (2009) Restoration of mires of the Australian Alps following the 2003 wildfires. Pages 353–362 in: S.G. Haberle, J. Stevenson & M. Prebble (eds.) Altered Ecologies: Fire, Climate and Human Influence on Terrestrial Landscapes. Terra Australis 32, Australian National University e-press, Canberra, Australia.}

_{Sagot C. & Rochefort L. (1996) Tolérance des sphaignes à la dessiccation (Tolerance of Sphagnum mosses to desiccation; in French). Cryptogamie, Bryology-Lichénologie, 17, 171–183.}

Study locations

Key messages

Two studies evaluated the effects, on peatland vegetation, of covering a peatland with organic mulch (without planting). Both studies were in bogs (but in one study, being restored as a fen).
Vegetation cover (2 studies): One replicated, randomized, paired, controlled, before-and-after study in a bog in Canada found that covering bare peat with straw mulch did not affect cover of fen-characteristic plants. One replicated, controlled, before-and-after study in a bog in Australia reported that plots mulched with straw had similar Sphagnum moss cover to unmulched plots.
Characteristic plants (1 study): One replicated, randomized, paired, controlled, before-and-after study in a bog in Canada found that covering bare peat with straw mulch increased the number of fen characteristic plants present, but did not affect their cover.

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, paired, controlled, before-and-after study in 2001–2002 in a historically mined bog in Quebec, Canada (Cobbaert et al. 2004) found that mulching with straw increased the number of fen-characteristic plant species but had no effect on fen-characteristic plant cover. Note that the aim of this study was to create a fen, as the post-mining peat chemistry was more like a fen than a bog. Before sowing, no vegetation was present. After two growing seasons, there were more plant species typical of local fens in mulched plots (8 species) than unmulched plots (5 species). Fen plant cover did not significantly differ between mulched (6%) and unmulched plots (10%). In spring 2001, eighteen 5 x 5 m plots were established, in three blocks of six. Nine plots (three random plots/block) were mulched with straw (1,500 kg/ha). The other plots were not mulched. All plots had previously been rewetted, raked and fertilised. None of these plots were sown. In August 2002, cover of every plant species was estimated in ten 30 x 30 cm quadrats/plot.
Study and other actions tested
Referenced paper
Cobbaert D., Rochefort L. & Price J.S. (2004) Experimental restoration of a fen plant community after peat mining. Applied Vegetation Science, 7, 209-220.
A replicated, controlled, before-and-after study in 2003–2007 in a fire-damaged bog in Australia (Whinam et al. 2010) reported that mulching with straw had no effect on Sphagnum moss cover. This result is not based on a test of statistical significance. After 40 months, Sphagnum cover was similar in straw-mulched (8.6%) and unmulched plots (7.8%). This followed fluctuations over the 40 months, when Sphagnum cover was sometimes higher in mulched than unmulched plots but sometimes lower. Immediately before shading, plots had approximately 3% Sphagnum cover. In January 2003, the focal bog was burned by a wild fire. In October 2003, five burned plots (3 x 15 m) were mulched with sterilized straw (2 tonnes/ha). Five additional plots were not mulched. Vegetation cover was recorded in 0.25 m²quadrats: five across the bog in October 2003, then one/plot every six months until March 2007.
Study and other actions tested
Referenced paper
Whinam J., Hope G., Good R. & Wright G. (2010) Post-fire experimental trials of vegetation restoration techniques in the peatlands of Namadgi (ACT) and Kosciuszko National Parks (NSW), Australia. Pages 363-379 in: Terra Australis 32. Australian National University e-press, Canberra.

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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