Conservation Evidence strives to be as useful to conservationists as possible. Please take our survey to help the team improve our resource.

Providing evidence to improve practice

Action: Cover peatland with organic mulch (after planting) Peatland Conservation

Key messages

Read our guidance on Key messages before continuing

  • Twelve studies evaluated the effects, on peatland vegetation, of adding organic mulch after planting peatland plants. Nine studies were in bogs (one being restored as a fen). Two studies were in fens. One was in a tropical peat swamp.
  • Germination (1 study): One replicated, controlled, before-and-after study in a bog in Germany found that mulching after sowing seeds increased germination rates for two species (a grass and a shrub), but had no effect on three other herb species.
  • Survival (3 studies): Two replicated, paired, controlled studies in a fen in Sweden and a bog in the USA reported that mulching increased survival of planted vegetation (mosses or sedges). One replicated, paired, controlled study in Indonesia reported that mulching with oil palm fruits reduced survival of planted peat swamp tree seedlings.
  • Growth (1 study): One replicated, randomized, paired, controlled, before-and-after study in a fen in the USA reported that mulching increased growth of transplanted sedges.
  • Cover (9 studies): Six studies (including four replicated, randomized, paired, controlled, before-and-after) in bogs in Canada and the USA and a fen in Sweden found that mulching after planting increased vegetation cover (specifically total vegetation, total mosses/bryophytes, Sphagnum mosses or vascular plants after 1–3 growing seasons). Three replicated, randomized, paired, controlled, before-and-after studies in degraded bogs in Canada found that mulching after planting had no effect on vegetation cover (Sphagnum mosses or fen-characteristic plants).

Supporting evidence from individual studies

1 

A replicated, randomized, paired, controlled, before-and-after study in 1995–1996 in a historically mined raised bog in Quebec, Canada (Price et al. 1998) found that mulching plots sown with Sphagnum-dominated vegetation fragments increased Sphagnum moss cover. After 1–2 growing seasons, plots mulched with straw after adding the vegetation fragments had significantly higher Sphagnum cover (1–5%) than plots that were not mulched (<0.5%). In May 1995, 24 bare peat plots (15 x 15 m, in three blocks of eight) were sown with vegetation fragments (mostly Sphagnum moss) from the surface of a nearby bog. Twelve of the plots (four random plots/block) were mulched with straw after sowing (2,250 kg/ha). All plots had been rewetted, and the surface of some was roughened. In June and September 1996, Sphagnum cover was estimated in 36–72 quadrats/plot, each 25 x 25 cm.

2 

A replicated, controlled, before-and-after study in 1993–1995 in a historically mined raised bog in Germany (Sliva & Pfadenhauer 1999) found that mulching plots sown with herb or shrub seeds increased germination for two of five species. For purple moor grass Molinia caerulea and heather Calluna vulgaris, mulched plots contained more seedlings after 1–2 years than unmulched plots (25–45 vs 1–8 seedlings/400 cm2). For three other herb species, mulched and unmulched plots contained a similar number of seedlings (0–10 vs 0–8 seedlings/400 cm2). In autumn 1993, seeds of five plant species were spread onto 1 m2 plots of bare rewetted peat (10 plots/species, 40–48 seeds/400 cm2). Five plots/species were mulched with leaves or heather branches, whilst five were not mulched. Mulch was removed and seedlings counted in summer 1994 (two plots/treatment) and 1995 (three plots/treatment).

3 

A replicated, paired, controlled study in 1999–2000 in a degraded peat swamp in Malaysia (Ismail et al. 2001) reported that mulching with oil palm fruits reduced the survival of planted tree seedlings. No statistical tests were carried out. After 14 months, 50% of mulched seedlings had survived, compared to 83% of seedlings that were not mulched. The mulch attracted wild boars (which damaged the seedlings) and produced a hot vapour (which may have dried the seedlings). In June 1999, thirty-six plots in a degraded, open peat swamp were planted with peat swamp trees (16 seedlings/plot). There were three pairs of plots for each of six tree species. Eighteen plots (one plot/pair) were mulched with fresh oil palm fruit skins. The other plots were not mulched. All plots were cleared of vegetation before planting and the planting holes were fertilized. Survival was recorded in August 2000.

4 

A replicated, randomized, paired, controlled, before-and-after study in 1994–1996 in a historically mined bog in Quebec, Canada (Rochefort et al. 2003) reported that mulching plots sown with vegetation fragments increased vegetation cover. These results were not tested for statistical significance. After three growing seasons, total vegetation cover was 17–24% in mulched plots but 3–5% in unmulched plots. This included Sphagnum moss (mulched: 0–7%; unmulched: <1%), other moss (mulched: 2–13%; unmulched: 1–2%) and vascular plants (mulched: 4–15%; unmulched: 1–4%). In early 1994, mixed plant material was collected from a natural bog and spread onto 12 pairs of plots (each 3 x 15 m) of bare rewetted peat. Then, one random plot in each pair was mulched with straw (1,500 kg/ha). The other plots were not mulched. In 1994 and 1996, vegetation cover was estimated within quadrats in each plot (details not reported).

5 

A replicated, paired, controlled, before-and-after study in 1994–1996 in a historically mined bog in Quebec, Canada (Rochefort et al. 2003) found that amongst plots sown with vegetation fragments, mulching with straw increased total vegetation and moss cover, but shrub root mulch had no effect. After three growing seasons, plots mulched with straw had significantly higher cover than unmulched plots of total vegetation (mulched: 20%; unmulched: 3%), Sphagnum moss (mulched: 1%; unmulched: 0%) and other moss (mulched: 16%; unmulched: 2%). Cover of vascular plants was similar (<1%) in mulched and unmulched plots. In contrast, all vegetation groups had similar cover in plots covered with shrub roots and the unmulched plots (total: 4%; Sphagnum moss: <1%; other moss: 3%; vascular plants: <1%). In spring 1994, plant material was scraped from the surface of a natural bog and spread onto plots of bare rewetted peat. There were nine 9 m2 plots, arranged in three blocks of three. One plot/block was then covered with a straw mulch (1,500 kg/ha), one loosely covered with shrub roots (20% cover) and one left uncovered. Vegetation cover was estimated in 1994 and 1996 (details not reported).

6 

A replicated, randomized, paired, controlled, before-and-after study in 1997–1999 in a historically mined bog in Minnesota, USA (Rochefort et al. 2003) found that mulching plots sown with vegetation fragments increased total vegetation and Sphagnum moss cover. After two growing seasons, mulched plots had significantly greater cover than unmulched plots of total vegetation (54–77% vs 1–3%) and Sphagnum moss (51–73% vs <1%). Mulched and unmulched plots had similar cover of other mosses (<1%) and vascular plants (1–3%). In 1997–1998, vegetation was scraped from the surface of natural bogs and spread onto plots of bare peat. There were forty-eight 1.5 x 1.5 m plots, arranged in six blocks of eight. Four random plots/block were mulched with straw (3,000 kg/ha). The other plots were not mulched. Four plots/block were also planted with sedges Carex oligosperma before adding vegetation fragments. In October 1999, vegetation cover was visually estimated in four 25 x 25 cm quadrats/plot.

7 

A replicated, controlled, before-and-after study in 1993–1996 in a historically mined bog in Quebec, Canada (Rochefort et al. 2003) reported that mulching plots sown with vegetation fragments increased vegetation cover. These results were not tested for statistical significance. After three growing seasons, plots mulched with straw had total vegetation cover of 3–11% (vs 2% in unmulched plots), total moss cover of 2–6% (unmulched: <1%), Sphagnum moss cover of 1–4% (unmulched: <1%) and vascular plant cover of 1–2% (unmulched: <1%). Amongst mulched plots, vegetation cover (of all groups) was higher when more mulch was added. However, cover was similar in plots mulched in autumn or spring (see original paper). In autumn 1993, vegetation was scraped from the surface of a natural bog and spread onto a ploughed, bare peat site. Within this site, 10 x 10 m plots were mulched with straw immediately or in the following spring: 750, 1,500 or 3,000 kg/ha (number of plots not reported). Some additional plots were not mulched. In autumn 1996, vegetation cover was visually estimated in fourteen 25 x 25 cm quadrats/plot.

8 

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 plots sown with vegetation fragments 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 (13–15 species) than unmulched plots (10–12 species). Fen plant cover did not differ between mulched (21–30%) and unmulched plots (23–32%). Mulching had similar effects in additional plots that were not sown with vegetation fragments (see intervention Add organic mulch without planting). In spring 2001, soil and vegetation from nearby moss or grass-dominated fens was spread onto thirty-six 5 x 5 m plots (arranged in three equal blocks). Eighteen plots (six 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. In August 2002, cover of every plant species was estimated in ten 30 x 30 cm quadrats/plot.

9 

A replicated, randomized, paired, controlled, before-and-after study in 2004–2005 in a degraded fen in Sweden (Mälson & Rydin 2007) reported that mulching with sedge litter increased survival and growth of planted moss fragments, but only when plots were not limed. These results are not based on tests of statistical significance. Amongst unlimed plots, moss survival after one growing season was higher in mulched plots (13% of plots contained live moss) than in unmulched plots (4%). Moss cover after two growing seasons was higher in mulched plots (3–7%) than unmulched plots (≤1%). However, amongst limed plots, mulching had no effect on survival (mulched: 62%; unmulched: 60%) or growth (mulched: 13–24%; unmulched: 8–28%). In June 2004, fragments of four fen-characteristic moss species were added (16 fragments of a single species in 9 cm2 subplots) to 16 plots (625 cm2) of bare rewetted peat. Eight plots were then sparsely mulched with sedge Carex lasiocarpa litter. The other eight plots were not mulched. Eight plots were also limed before planting. Moss survival was assessed after one growing season and moss cover visually estimated after two.

10 

A replicated, paired, controlled, before-and-after study in 2007–2010 in three degraded fens in Colorado, USA (Chimner 2011) found that mulching increased survival and growth of transplanted water sedge Carex aquatilis, and survival of sown moss fragments. For transplanted sedges, survival over three years was higher in mulched plots than in unmulched plots (55 vs 35%). The same was true for growth (30–82 vs 7–81 stems/plot). No moss survived on unmulched plots. Under mulch, Russow’s bogmoss Sphagnum russowii survived in one of three sites reaching 19% cover after three years. Under mulch, haircap moss Polytrichum strictum survived in all three sites reaching 3–11% cover after three years. In July 2007, thirty-six plots were established (in six blocks of six) on bare peat. Twelve plots (two plots/block) received each planting treatment: sedges (18 single stems/plot), mosses (mixed Sphagnum and haircap moss fragments; 4.4 L/plot) or sedges and mosses. Half of the plots were mulched with straw (immediately) and shredded aspen (after one year). The other plots were not mulched. In summer 2010, sedge survival, sedge stem number and moss cover were recorded.

11 

A replicated, randomized, paired, controlled, before-and-after study in 2007–2010 in two historically disturbed bogs in Ontario, Canada (Corson & Campbell 2013) found that mulching plots sown with Sphagnum moss fragments had no effect on bryophyte cover. After three years, Sphagnum cover did not differ significantly between treatments (sedge mulch: 33%; coconut mulch: 42%; straw mulch: 52%; no mulch: 38%). There was also no difference in total bryophyte cover between treatments (mulch: 66–76%; no mulch: 68%). In August 2007, fragments of rusty bog moss Sphagnum fuscum and flat-topped bog moss Sphagnum fallax were spread onto 24 bare peat plots (each 2 x 2 m, arranged in six blocks of four). Six plots (one random plot/block) received each mulch treatment: none, sedge cuttings, coconut fibre or straw. All plots were also fertilized with rock phosphate. In August 2010, moss cover was estimated in six random 12.5 x 12.5 cm subplots within each plot.

12 

A replicated, randomized, paired, controlled, before-and-after study in 2007–2010 in two historically disturbed bogs in Ontario, Canada (Corson & Campbell 2013) found that mulching plots sown with Sphagnum moss fragments had no effect on bryophyte cover. After three years, Sphagnum cover did not significantly differ between mulched plots (9–17%) and unmulched plots (3–7%). There was also no difference in total bryophyte cover between mulched plots (29–51%) and unmulched plots (24–31%). In May 2007, fragments of rusty bog moss Sphagnum fuscum and flat-topped bog moss Sphagnum fallax were spread onto 24 bare peat plots (each 1 m2, arranged in four blocks of six). Twelve plots (three random plots/block) were then mulched with straw. The other 12 plots were not mulched. All plots were fertilized with rock phosphate. In August 2010, moss cover was estimated in six random 12.5 x 12.5 cm subplots within each plot.

Referenced papers

Please cite as:

Taylor N.G., Grillas P. & Sutherland W.J. (2018) Peatland Conservation. Pages 329-392 in: W.J. Sutherland, L.V. Dicks, N. Ockendon, S.O. Petrovan & R.K. Smith (eds) What Works in Conservation 2018. Open Book Publishers, Cambridge, UK.