Action: Irrigate peatland (without planting)
Key messagesRead our guidance on Key messages before continuing
- Two studies evaluated the effects of irrigation (without planting) on peatland vegetation. One study was in a bog and one was in a fen.
- Vegetation cover (2 studies): One replicated, paired, controlled, before-and-after study in a bog in Canada found that irrigation increased the number of Sphagnum moss shoots present after one growing season, but had no effect after two. One before-and-after study in Germany reported that an irrigated fen was colonized by wetland- and fen-characteristic herbs, whilst cover of dryland grasses decreased.
To avoid desiccation of vegetation on the surface of peatlands, irrigation systems such as sprinklers could be used (Rochefort & Bastien 1998). Water could be recirculated from drainage ditches or ponds on the peatland. Irrigation would maintain a damp peat surface. Irrigation can be expensive so may be best used as a short-term intervention to kick-start restoration.
Caution: A suitable water source, with the right level of nutrients and acidity/alkalinity, must be chosen to avoid altering chemical conditions on the peatland (Lamers et al. 2002). For example, bogs should only be irrigated with water stored on the bog, not ground water. Taking water for irrigation might reduce water levels in neighbouring wetlands.
Key peatland types where this action may be appropriate: bogs, fens/fen meadows, tropical peat swamps.
Lamers L.P., Smolders A.J.P. & Roelofs J.G.M. (2002) The restoration of fens in the Netherlands. Hydrobiologia, 478, 107–130.
Rochefort L. & Bastien D.F. (1998) Réintroduction de sphaignes dans une tourbière exploitée: évaluation de divers moyens de protection contre la dessiccation (Reintroduction of Sphagnum to an exploited bog: evaluation of various methods for protection against desiccation; in French). Écoscience, 5, 117–127.
Supporting evidence from individual studies
A replicated, paired, controlled, before-and-after study in 1993–1994 in a historically mined bog in Quebec, Canada (Rochefort & Bastien 1998) found that irrigated plots contained more Sphagnum moss shoots than unirrigated plots after one growing season, but a similar number of Sphagnum shoots after two. After one growing season there were more Sphagnum shoots in irrigated plots (210 shoots/m2) than plots that were not irrigated (75 shoots/m2). However, after two growing seasons the number of moss shoots did not significantly differ between treatments (irrigated: 80; not irrigated: 50 shoots/m2). In spring 1993, three pairs of plots were established on slightly drained, bare peat. Three plots (one plot/pair) were irrigated during the summer, using sprinklers and water stored on the bog. The other plots were not irrigated. In autumn 1993 and 1994, all Sphagnum shoots were counted in forty 30 x 30 cm quadrats/plot.
A before-and-after study in 1996–1998 in a degraded fen in Germany (Richert et al. 2000) reported that irrigated plots developed cover of wetland- and fen-characteristic herbs at the expense of dry grassland species. All data were reported as graphical analyses and the results were not tested for statistical significance. Over two years of irrigation, cover of fen-characteristic forbs increased. The same was true for cover of wetland-characteristic species like cattail Typha latifolia and common rush Juncus effusus. Meanwhile, cover of dry grassland species such as tall fescue Festuca arundinacea decreased. No colonisation by sedges Carex spp. or common reed Phragmites australis was observed. Within the irrigated fen, plant communities differed between drier areas (high water table but never flooded) and wetter areas (sometimes flooded). In 1996, the surface of a drained fen was irrigated with lake water. Vegetation cover was recorded before irrigation (1996) and after one or two years or irrigation (1997, 1998) in four representative 16 m2 plots.
- Rochefort L. & Bastien D.F. (1998) Reintroduction of Sphagnum to an exploited bog: evaluation of various methods for protection against desiccation. Écoscience, 5, 117-127
- Richert M., Dietrich O., Koppisch D. & Roth S. (2000) The influence of rewetting on vegetation development and decomposition in a degraded fen. Restoration Ecology, 8, 186-195