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Providing evidence to improve practice

Action: Directly plant peatland trees/shrubs Peatland Conservation

Key messages

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  • Eleven studies evaluated the effects, on peatland vegetation, of planting trees/shrubs to restore or create forested/shrubby peatland. Seven studies were in tropical peat swamps, three in bogs and one in a fen.
  • Survival (10 studies): Eight studies (seven replicated) in peat swamp forests in Thailand, Malaysia and Indonesia and bogs in Canada reported that the majority of planted trees/shrubs survived over periods between 10 weeks and 13 years. Species with <50% survival included Dacryodes, poplar and katok. One replicated study in a fen in the USA reported that most planted willow cuttings died within two years. One study in a peat swamp forest in Indonesia reported <5% survival of planted trees after five months, following unusually deep flooding.
  • Growth (5 studies): Four studies (including two replicated, before-and-after) in peat swamp forests in Thailand, Indonesia and Malaysia reported that planted trees grew. One replicated before-and-after study in bogs in Canada reported that planted shrubs grew.

Supporting evidence from individual studies

1 

A replicated study in 1992–1994 in a historically mined fen in Colorado, USA (Cooper & MacDonald 2000) reported that 12–33% of planted willow Salix spp. cuttings survived over two years. Four species were planted. Survival of myrtle-leaf willow Salix myrtillifolia was 33%, mountain willow Salix monticola 26%, hoary willow Salix candida 13% and barren ground willow Salix brachycarpa 12%. In June 1992, four plots (myrtle-leaf willow) or 27 plots (all other species) were planted with 10–20 fresh cuttings of each species. Plots were 0.5 x 0.5 m, contained a “few” centimetres of surface peat, had variable water levels and had been cleared of existing vegetation. Cuttings were woody stems approximately 30 cm long. Approximately 20 cm was buried below the soil surface. Half the leaves were removed prior to planting. Survival was recorded in August 1994.

2 

A study in 1988–1997 in a degraded peat swamp in Thailand (Nuyim 2000) reported that 22–97% of planted trees survived for four years or more, and that surviving trees grew. No statistical tests were carried out. For 22 of 28 planted species, at least 50% of planted trees survived for at least four years. Survival was highest for milkwood Alstonia spathulata and Ixora grandifolia (97% after four years) and lowest for Dacryodes sp. (22% after four years). For 13 species, survival rates over nine years were also reported and were similar to those after five and half years (within 2%). For 15 species, growth rates were reported. These species all grew, from 35–120 cm tall one year after planting to 110–340 cm tall four years after planting. Trees (number not reported) were planted into the degraded peat swamp in 1988 (13 species) or 1993 (15 species). Survival and height were recorded up to nine years after planting.

3 

A replicated study in 1999–2000 in a degraded peat swamp in Malaysia (Ismail et al. 2001) reported that 50–92% of planted tree seedlings survived over 14 months. No statistical tests were carried out. Of the six planted species, survival was highest for Ganua motleyana (92%) and lowest for Calophyllum ferrugineum (56%). Of four different planting techniques used, three supported high survival rates (82–83%, averaged across species). The fourth technique, adding oil palm fruits as mulch, supported lower survival (50%, averaged across species). In June 1999, tree seedlings were planted into 72 plots (12 plots/species) in a degraded, open peat swamp. Three plots/species were planted using each technique: mulching with oil palm fruit, planting additional nurse trees, adding topsoil or no additional intervention. In all plots, 16 seedlings were planted 3 m apart. Existing vegetation was cleared and fertilizer was added to the planting holes. Survival was recorded in August 2000.

4 

A replicated study in 1990–2002 in four historically mined bogs in eastern Canada (Bussières et al. 2008) reported that 9–100% of planted tree saplings survived over 1–13 years. Five species were planted. Jack pine Pinus banksiana survival was 100% after two years. Tamarack Larix laricina survival was 52–100% over 1–9 years. Black spruce Picea mariana survival was 65–94% over 1–13 years. Red maple Acer rubrum survival was 72% after three years. Poplar Populus spp. survival was 9% after three years. Between 1990 and 2001, tree saplings were planted into bare peat, in single species blocks (1,600–2,500 stems/ha), in up to four separate bogs. Additional management (e.g. soil preparation, fertilization, planting density) differed between sites (see original paper). In 2002, survival of saplings (18–360/species/bog) was recorded in quadrats distributed evenly across the planted blocks.

5 

A replicated study in 2004–2005 in a historically mined bog in Quebec, Canada (Caisse et al. 2008) reported that 81% of planted tamarack Larix laricina seedlings and 55% of planted black spruce Picea mariana seedlings survived over 16 months. Additional fertilized seedlings had higher survival: 92–98% for tamarack and 58–87% for black spruce. In June 2004, seedlings were planted 3 m apart into drained, bare peat. For each species, three plots of 50 seedlings were fertilized, but three plots of 900 seedlings were not. Survival was checked after two growing seasons in October 2005.

6 

A study in 2003–2004 in a fire-damaged peat swamp forest in Indonesia (van Eijk et al. 2010) reported that most planted tree seedlings survived over three months, but most had died after five months following flooding. Nine species of peat swamp trees were planted. After three months, 65–85% of seedlings had survived. However, after five months <5% of seedlings remained alive following unusually deep flooding. At this point, survival was highest for myrtle Eugenia sp. (27%) and red lauan Shorea pauciflora (13%). No Palaquium sp., Gluta wallichii or Dryera polyphylla seedlings survived the deep flooding. In November and December 2003, fourteen thousand tree seedlings were planted into individual mounds (30–50 cm tall) within a burned peat swamp. Most seedlings (94%) were Gonystylus bancanus, Palaquium sp., Gluta wallichii and Shorea pacuiflora. Survival was monitored in February and, for 10% of the planted mounds, in April 2004.

7 

A study in 2002–2006 in a logged peat swamp in Kalimantan, Indonesia (Turjaman et al. 2011) reported that 83% of planted red balau Shorea balangeran seedlings survived over 40 months. On average, these were 206 cm tall and had 27 cm diameter stems. Additional seedlings inoculated with root fungi had higher growth rates than the uninoculated seedlings with three of three fungal species (213–240 cm tall; 30–37 cm diameter), but higher survival (85%) in only one of three cases. In November 2002, 100 red balau seedlings were planted (1 m apart) into logged forest. Seedlings had been grown in sterilized peat in a nursery. One hundred seedlings inoculated with each of three fungal species were also planted for comparison. Seedling height, stem diameter and survival were measured 40 months after planting.

8 

A replicated before-and-after study in 2004–2008 three historically mined bogs in eastern Canada (Vander Kloet et al. 2012) reported that 63–100% of planted shrub clumps survived over four years, and that survivors had grown in diameter. Survival of bog cranberry Vaccinium oxycoccos was 100%, crowberry Empetrum spp. 83%, lingonberry Vaccinium vitis-ideae 71%, and mixed-species clumps (mostly Vaccinium berry species) 63%. Approximately 96% of surviving clumps showed positive growth (data not reported for single species). Amongst these, diameter increased by 50 cm/year for bog cranberry, 8 cm/year for crowberry, 22 cm/year for lingonberry and 7–8 cm/year for mixed clumps. Additionally, across all studied species, bigger clumps were more likely to survive (see original paper). In 2004, 916 clumps of shrub seedlings were planted, 1–2 m apart, along transects on wet peat. Initial clump diameter was recorded. Seedlings had been grown in a greenhouse from seeds in berries or scat fragments. In 2008, survival and final clump diameter were measured.

9 

A replicated before-and-after study in 2007–2009 in a peat swamp in Indonesia (Graham et al. 2013) reported that 75–91% of planted red balau Shorea balangeran and jelutong Dyera polyphylla survived over one year, and that  surviving trees had grown. Survival was not reported separately for the two planted species. After one year, planted seedlings of both species had increased in height (red balau by 4–11 cm; jelutong: by 2–4 cm) and diameter (both species by 0.6–2.7 mm). Amongst planted seedlings, growth (but not survival) differed between forest types. Seedlings grew significantly taller and thinner in closed forest vs open forest (see original paper). Inoculation with fungi had no significant effect on survival or growth (see intervention Add root-associated fungi before planting). In 2007 or 2008, nursery-reared seedlings (800 red balau and 700 jelutong) were planted in five forest types from natural/closed forest to degraded/open land. Between half and two-thirds of the seedlings had been inoculated with root fungi. After one year, all seedlings’ survival and growth were measured.

10 

A replicated before-and-after study in 2007 in a burned peat swamp forest in Sabah, Malaysia (Mojol et al. 2014) reported that two of three planted tree species survived and grew in height and diameter over 10 weeks. Of 15 planted geronggang Cratoxylum arborescens seedlings, 93% survived. For pulai Alstonia spathulata, survival was 87%. For katok Stemonurus scorpioides, survival was 0%. Geronggang seedlings increased in height by 24 cm and diameter by 2.8 mm. Pulai seedlings increased in height by 9 cm and diameter by 1.9 mm. In September 2007, three burned plots were planted with 45 seedlings (15 seedlings of each species, mixed together but 3 m apart). Survival, height and diameter of seedlings were measured over 10 weeks after planting.

11 

A study in peat swamps in Indonesia (Harun & Yuwati 2015) reported that planted jelutong trees (probably Dryera polyphylla, but not clearly reported) grew in height and diameter within a range of agroforestry systems. Over approximately six years after planting, tree height increased by 87–128 cm/year, and diameter increased by 1.6–2.2 cm/year. Trees (probably saplings, but not clearly reported) were planted in peat swamps between strips of crops, mixed with crops or amongst aquaculture operations. Tree diameter and height were measured between 64 and 78 months after planting.

Referenced papers

Please cite as:

Taylor N.G., Grillas P. & Sutherland W.J. (2019) Peatland Conservation. Pages 375-438 in: W.J. Sutherland, L.V. Dicks, N. Ockendon, S.O. Petrovan & R.K. Smith (eds) What Works in Conservation 2019. Open Book Publishers, Cambridge, UK.