Action: Create mounds or hollows (before planting)
- Three studies examined the effect, on peatland vegetation, of creating peat mounds or hollows before planting peatland plants. Two studies were in bogs. One was in a tropical peat swamp.
- Growth (1 study): One controlled study in a peat swamp in Thailand reported that trees planted into mounds of peat grew thicker stems than trees planted at ground level.
- Cover (2 studies): Two replicated, randomized, paired, controlled, before-and-after studies in bogs in Canada found that roughening the peat surface (by harrowing, ploughing, creating vehicle tracks or adding peat blocks) did not significantly affect cover of planted Sphagnum moss after 1–3 growing seasons.
Vegetation may struggle to colonize flat bare peat. It can be damaged by extreme heat, sunlight, strong winds or prolonged flooding. In temperate peatlands, roughening the peat surface (e.g. by ploughing, creating vehicle tracks, or adding peat blocks) could create lower sheltered, moist and shaded habitats that are more suitable for plant growth. These processes can also break up any hard crust or compress loose, dry peat. Although raised areas might be less suitable for peatland vegetation initially, the idea is that peatland vegetation can spread from the depressions once they have been colonized. In tropical peatlands, planting trees into mounds might improve their survival by reducing the duration of flooding and increasing oxygen supply to the roots (Wibisono et al. 2005). Mounds may naturally form in peat swamp forests from the roots of fallen trees.
Caution: Manipulating the peat surface may damage its physical structure. Repeated use of vehicles on soft, wet peat may be particularly damaging.
Related interventions: roughen peat surface without introducing vegetation; large scale reprofiling/relandscaping before planting.
Wibisono I.T.C., Siboro L. & Suryadiputra I.N.N. (2005) Panduan Rehabilitasi dan Teknik Silvikultur di Lahan Gambut (A Guide to Rehabilitation and Silvicultural Engineering on Peatlands; in Indonesian). Wetlands International Indonesia Programme & Wildlife Habitat Canada, Bogor.
Supporting evidence from individual studies
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 roughening the peat surface, before sowing Sphagnum-dominated vegetation fragments, had no effect on Sphagnum moss cover. After 1–2 growing seasons, roughened and smooth plots had similar cover of Sphagnum, when compared amongst mulched areas (roughened: 1.4–4.7%; smooth: 1.2–2.3%) or unmulched areas (roughened: 0.1–0.3%; smooth: 0.1–0.2%). In May 1995, twelve 15 x 30 m plots were established, in three blocks of four, on bare rewetted peat. Three plots (one random plot/block) received each roughening treatment: harrowing (5 cm deep), ploughing (20 cm deep), using bulldozer tracks to create trenches (1 m wide, 20 cm deep), or no intervention (smooth plots). Then, all plots were sown with vegetation fragments (mostly Sphagnum moss) from the surface of a nearby bog. Half of each plot was mulched with straw. In June and September 1996, Sphagnum cover was estimated in 36–72 quadrats/plot, each 25 x 25 cm.
A controlled study in a degraded peat swamp in Thailand (Nuyim 2000) reported that five tree species grew thicker stems when planted into mounds than when planted at ground level. The results were not tested for statistical significance. After three years and for all five planted species, trees planted into mounds had developed thicker stems (3–6 cm) than trees planted at ground level (2–3 cm). Mounds had a particularly strong effect on Syzygium pyrifolium stem thickness (mounded: 6 cm; ground level: 3 cm). In a degraded peat swamp, trees were either planted into mounds of peat (50 cm high, 70–90 cm circumference) or at ground level. After three years, the diameter of all trees was measured 10 cm above the peat surface. The year, number of trees and their initial size were not reported.
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 placing peat blocks on a peatland, before sowing Sphagnum moss, had no effect on bryophyte cover. After three years, Sphagnum cover did not differ significantly between plots with peat blocks (40%) or without (38%). There was also no difference in total bryophyte cover between plots with peat blocks (66%) or without (67%). In August 2007, six pairs of 2 x 2 m plots were established on bare peat, historically disturbed by vehicles or pipeline construction. Twenty-five bare peat blocks (10 x 12 x 20 cm) were evenly spaced on one random plot in each pair. Then, all plots received fresh fragments of rusty bog moss Sphagnum fuscum and flat-topped bog moss Sphagnum fallax, and 30 g/m2 rock phosphate fertilizer. In August 2010, moss cover was estimated in six random 12.5 x 12.5 cm subplots within each plot.
- 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
- Nuyim T. (2000) Whole aspect on nature and management of peat swamp forest in Thailand. Proceedings of the International Symposium on Tropical Peatlands, Bogor, Indonesia, 109-117.
- Corson A. & Campbell D. (2013) Testing protocols to restore disturbed Sphagnum-dominated peatlands in the Hudson Bay Lowland. Wetlands, 33, 291-299