Cover peatland with something other than mulch (after planting)
Overall effectiveness category Likely to be beneficial
Number of studies: 8
Background information and definitions
Introduced peatland vegetation may be killed by hot, dry and bright conditions on bare peat surfaces (e.g. Harley et al. 1989; Sagot & Rochefort 1996). Covers (e.g. plastic sheets, fleece or geojute fibre mats) can physically stabilize the peat surface, maintain more constant temperatures and humidity, and offer some shading. This creates a more hospitable environment for establishment and growth of introduced vegetation (Price et al. 1998).
This section considers covers that may be placed on peatlands as sheets to control light and/or moisture levels. The precise effect may vary depending on the material and the height above the peatland. We use the term mesh to describe all net-like covers with lots of small holes, used primarily to shade the peatland surface. This includes shade screens, shade cloths, gauze and netting.
Key peatland types where this action may be appropriate: bogs, fens/fen meadows, tropical peat swamps.
Harley P.C., Tenhunen J.D., Murray K.J. & Beyers J. (1989) Irradiance and temperature effects on photosynthesis of tussock tundra Sphagnum mosses from the foothills of the Philip Smith Mountains, Alaska. Oecologia, 79, 251–259.
Price J., Rochefort L. & Quinty F. (1998) Energy and moisture considerations on cutover peatlands: surface microtopography, mulch cover and Sphagnum regeneration. Ecological Engineering, 10, 293–312.
Sagot C. & Rochefort L. (1996) Tolérance des sphaignes à la dessiccation (Tolerance of Sphagnum mosses to desiccation; in French). Crytogamie, Bryology-Lichénologie, 17, 171–183.
Supporting evidence from individual studies
A replicated, randomized, controlled, before-and-after study in a greenhouse in Switzerland (Buttler et al. 1998) found that planted Sphagnum moss grew longer, thinner shoots in pots covered with plastic sheets or mesh than in uncovered pots. Over 16 weeks, Sphagnum increased in length significantly more in covered pots (plastic sheet: <10–90 mm; plastic mesh: 6–68 mm; uncovered: 3–46 mm increase). However, neither cover significantly affected Sphagnum mass growth (sheet: 0.8–5.5; mesh: 0.1–2.2; uncovered: 0.3–4.2 proportional increase). In May (year not reported), 90 pots of peat were planted with flat-topped bog moss Sphagnum fallax: twelve 3 cm fragments/pot. Thirty pots were then covered with clear green plastic (with 1 cm diameter holes covering about 5% of the surface area), 30 were shaded with plastic mesh (blocking 80% of incoming light), and 30 left uncovered. All pots were kept in random positions in a greenhouse with controlled temperature, humidity, light and water. After 16 weeks, length and dry mass of all moss fragments were measured.Study and other actions tested
A replicated, randomized, paired, controlled, before-and-after study in 1993–1994 in a historically mined bog in Quebec, Canada (Rochefort & Bastien 1998) found that amongst plots sown with Sphagnum-dominated vegetation fragments, those shaded with plastic mesh contained more Sphagnum moss shoots than those covered with transparent plastic sheets or not covered. After two growing seasons, there were significantly more Sphagnum shoots in plots covered with plastic mesh (140–510/m2) than plots covered with plastic sheets (10–30/m2) or uncovered plots (65–70/m2). Further, the number of Sphagnum shoots increased over the second growing season in shaded plots, but decreased in the other plots. Covers had a similar effect on all focal Sphagnum species. In spring 1993, twelve plots (three blocks of four) of slightly drained bare peat were sown with vegetation fragments (mostly Sphagnum moss; 250 fragments/m2). In each plot, subplots received fragments dominated by one of five single Sphagnum species. Three plots (one random plot/block) received each cover treatment: no cover, AgrinetTM 40% plastic mesh, AgrinetTM 60% plastic mesh, or a transparent polythene sheet (with 3 cm diameter holes cut 30 cm apart). Covers were 15–20 cm above the bog surface. In autumn 1993 and 1994, Sphagnum shoots were counted in ten 30 x 30 cm quadrats/plot.Study and other actions tested
A replicated, controlled, before-and-after study in 1993–1995 in a historically mined raised bog in Germany (Sliva & Pfadenhauer 1999) reported that covering plots with fleece or fibre mats did not affect germination of three of five sown species but increased germination of the other two. These results are not based on tests of statistical significance. For three herb species, there were a similar number of seedlings after 1–2 years in covered plots (0–11 seedlings/400 cm2) and uncovered plots (0–10 seedlings/400 cm2). In contrast, for one herb and one shrub species, there were 14–27 seedlings/400 cm2 in covered plots but only 1–8 seedlings/400 cm2 in uncovered plots. Fleece and fibre mat had similar effects on seedling number (see original paper). Covers had no effect on germination in additional plots that were not sown (see intervention Cover peatland without planting). In autumn 1993, seeds of five plant species were spread onto 1 m2 plots of bare rewetted peat (15 plots/species; 40–48 seeds/400 cm2). Five plots/species were covered with synthetic fleece, five with wide-meshed jute fibre mat, and five were not covered. Covers were removed and seedlings counted in summer 1994 (two plots/treatment) and 1995 (three plots/treatment).Study and other actions tested
A replicated, paired, controlled, before-and-after study in 1994–1996 in a historically mined bog in Quebec, Canada (Rochefort et al. 2003) reported that shading plots sown with vegetation fragments had no effect on vegetation cover. These results are not based on tests of statistical significance. Plots were initially rewetted bare peat. After three growing seasons, shaded and unshaded plots both had 3–4% total vegetation cover, <1% Sphagnum moss cover, 2% other moss cover and <1% vascular plant cover. In spring 1994, the moss layer was scraped from the surface of a natural bog and spread onto three pairs of bare peat plots (each 9 m2). Then, one plot in each pair was shaded with plastic mesh (AgrinetTM 57%). The other plots were not shaded. In 1994 and 1996, vegetation cover was estimated in each plot (details not reported).Study and other actions tested
A replicated, randomized, paired, controlled, before-and-after study in 2004–2005 in a degraded fen in Sweden (Mälson & Rydin 2007) reported that shading plots with plastic mesh increased survival and spread of planted moss fragments. These results are not based on tests of statistical significance. After one growing season, moss survival was 48–93% in shaded plots but only 4–60% in unshaded plots. After two growing seasons the pattern was similar: moss survival was 5–34% in shaded plots but <1–28% in unshaded plots. 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 shaded with plastic horticultural mesh (blocking 15% of incoming light). The other eight plots were not shaded. Some plots were also limed before planting. Moss survival was assessed after one growing season. Moss cover was visually estimated after two growing seasons.Study and other actions tested
A replicated, randomized, controlled, before-and-after study in a degraded fen in Sweden (Mälson & Rydin 2007) found that shading trays with plastic mesh reduced growth of one of two planted moss species, but did not affect growth of the other. After four months, shoots of intermediate hook moss Scorpidium cossonii were lighter in shaded trays (5–10 mg dry mass) than in unshaded trays (7–14 mg). In contrast, the mass of starry feather moss Campylium stellatum shoots was similar in shaded (4–5 mg) and unshaded trays (3–6 mg). When planted, shoots weighed approximately 1 mg. Six 33 x 33 cm trays of limed peat were set up, floating in a drainage ditch. Three of the trays were shaded with plastic mesh (blocking 45% of incoming light). Each tray was planted with 32 random fragments of each moss species, in single-species clusters. A subsample of fragments was dried and weighed before planting. After four months, all planted fragments were collected, rinsed, dried and weighed.Study and other actions tested
A replicated, paired, before-and-after study in 2003–2007 in a fire-damaged bog in Australia (Whinam et al. 2010) reported that amongst plots planted with sods of Sphagnum moss, those shaded with a horizontal plastic mesh developed greater Sphagnum cover than those shaded by a vertical mesh. These results were not tested for statistical significance. Immediately before planting, Sphagnum cover was 3% on average. Forty months after planting, horizontally shaded plots had 21% Sphagnum cover, compared to 11% in vertically shaded plots. In January 2003, the focal bog was burned by a wild fire. In October 2003, five pairs of plots (3 x 15 m) were planted with sods (20 x 20 x 30 cm) of mixed Sphagnum moss species. All sods were fertilized. In each pair, one plot was covered with plastic mesh (blocking 70% of incoming light) and one was shaded with a vertical mesh fence (1.6 m high). Sphagnum cover was estimated in 0.25 m2 quadrats: five in the bog in October 2003, and 1–2/plot in March 2007.Study and other actions tested
A replicated, randomized, controlled, before-and-after study in 2011 in a nursery in Indonesia (Rusmana et al. 2014) reported that shading with plastic mesh typically had no effect on survival of planted tree seedlings, but that shaded seedlings grew taller and thinner than unshaded seedlings. These results are not based on tests of statistical significance. Shading had no effect on survival to four months for 10 of 20 species (100% whether shaded or not) but increased survival for 8 of 20 species (shaded: 80–100%; full sun: 60–90%). Shaded seedlings typically grew taller (18 of 19 species) but had thinner stems (12 of 19 species) than seedlings grown in full sun (see original paper for data). In August 2011, 10 random seedlings per species received each shade treatment: 75%, 50% or none (full sun). Seedlings were grown in pots from seed or transplanted from the wild. Shade was created with one or two layers of plastic mesh, each layer blocking 50% of incoming light. Measurements were taken before (August) and after four months of shading (December).Study and other actions tested
Referenced paperRusmana ., Rachmanadi D., Santosa P.B., Yuwati T.W. & Graham L.L.B. (2014) Response of peat swamp forest species to light intensity. Pages 2-14 in: F.R.U. Banjarbu, . FORDA & L.L.B. Graham (eds.) Tropical Peat Swamp Forest Silviculture in Central Kalimantan. Kalimantan Forests and Climate Partnership, Indonesia.