Action: Use cutting/mowing to control problematic herbaceous plants
Key messagesRead our guidance on Key messages before continuing
- Four studies evaluated the effects on peatland vegetation of cutting/mowing problematic herbaceous plants. Three studies were in fens or fen meadows and one was in a bog. N.B. Cutting/mowing in historically disturbed peatlands is considered as a separate action.
- Plant community composition (3 studies): Two replicated, randomized, paired, controlled, before-and-after studies in rich fens in Sweden found that mowing typically had no significant effect on the overall plant community composition. One controlled study in a fen meadow in the UK reported that mown plots developed different plant communities to unmown plots.
- Characteristic plants (1 study): One replicated, randomized, paired, controlled, before-and-after study in a fen in Sweden found that mown plots contained more fen-characteristic plant species than unmown plots, although their cover did not differ significantly between treatments.
- Vegetation cover (2 studies): Of two replicated, randomized, paired, controlled, before-and-after studies in rich fens in Sweden, one found that mowing had no effect on vascular plant or bryophyte cover over five years. The other reported that mowing typically increased Sphagnum moss cover and reduced purple moor grass cover, but had mixed effects on cover of other plant species.
- Growth (1 study): One replicated, controlled, before-and-after study in a bog in Estonia found that clipping competing vegetation did not affect Sphagnum moss growth.
Cutting or mowing is the removal of above-ground parts of herbaceous plants or young trees/shrubs. Roots are left in place. Mowing and cutting can be broad tools affecting all plants in a community, so are often used to manage succession (development of plant communities over time). Cuttings may be removed from the site or left in place to rot down. Note that this choice will affect nutrients, temperature and light within the peatland, in turn determining which plant species can grow (Weltzin et al. 2005).
Caution: Mowing with heavy machinery could damage the peatland surface and vegetation. Cutting by hand or with specialized vehicles might cause less damage.
Key peatland types where this action may be appropriate: bogs, fens/fen meadows, tropical peat swamps.
Related actions: cutting/mowing to control herbaceous plants as part of a traditional disturbance regime; remove plant litter as part of/to compensate for loss of a traditional disturbance regime; change season of cutting/mowing; use low impact vehicles or harvesting techniques.
Weltzin J.F., Keller J.K., Bridgham S.D., Pastor J., Allen P.B. & Chen J. (2005) Litter controls plant community composition in a northern fen. Oikos, 110, 537–546.
Supporting evidence from individual studies
A controlled study in 1927–1940 in a fen meadow in England, UK (Godwin 1941) reported that repeated cutting changed the composition of the plant community. These results were not tested for statistical significance. After 12 years, a plot cut every year had a plant community dominated by purple moor grass Molinia caerulea with abundant carnation sedge Carex panicea (data reported as abundance categories). Sawtooth sedge Cladium mariscus biomass decreased over time (from 490 g/m2 after one cut to 50 g/m2 after 12 cuts). In an uncut plot, sawtooth sedge remained the most abundant plant species (data reported as abundance categories). Additional plots cut every two, three or four years developed plant communities intermediate between the annually cut and uncut plots. In 1927, five 20 x 20 m plots were established in a fen meadow dominated by sawtooth sedge. Four plots were scythed in October: one every year, one every two years, one every three years and one every four years. Cuttings were removed. The other plot was left uncut. Vegetation cover was visually estimated in 1940. Above-ground vegetation biomass was estimated every year, by drying and weighing cuttings from 1 m2 of each plot.
A replicated, controlled, before-and-after study in 2003–2006 in a raised bog in Estonia (Robroek et al. 2009) found that clipping competing plants did not significantly affect growth of Magellan’s bog moss Sphagnum magellanicum (data not reported). In six plots dominated by Magellan’s bog moss, vascular plants were clipped flush to the moss surface every May and September. Plants were not clipped in the six other plots. The height increase of Magellan’s bog moss was measured each summer.
A replicated, randomized, paired, controlled, before-and-after study in 2002–2005 in two degraded rich fens in Sweden (Mälson et al. 2010) reported that repeated mowing altered the plant community composition, reduced cover of purple moor grass Molinia caerulea and increased overall cover of Sphagnum moss. The cover results were not tested for statistical significance. Mowing altered the development of the overall plant community over three years, although only significantly so in one fen (data reported as a graphical analysis). In three of four comparisons, mown plots had lower cover than unmown plots of purple moor grass (mown: 1–37%; not mown: 2–50%) but higher overall cover of Sphagnum moss (mown: 2–41%; not mown: 1–28%). However, cover of individual Sphagnum species showed mixed responses to mowing amongst sites or other treatments applied to plots. The same was true for sedges Carex spp., common cottongrass Eriophorum angustifolium and common reed Phragmites australis. In autumn 2002, sixty-four 2.5 x 2.5 m plots were established (in four blocks of 16) across two degraded fens. Thirty-two plots (eight random plots/block) were mown every autumn between 2003 and 2005. Cuttings were removed. The other plots were not mown. Additionally, trees had been removed from all plots and some plots had been rewetted or dug over. In 2002 (before intervention) and 2005, cover of every plant species was estimated in one 0.25 m2 quadrat/plot.
A replicated, randomized, paired, controlled, before-and-after study in 1996–2001 in a degraded rich fen in Sweden (Sundberg 2011) found that mown and unmown plots maintained a similar overall plant community and vegetation cover, but that mown plots developed greater plant species richness. The overall plant community composition changed over five years, but in a similar way in mown and unmown plots (data reported as a graphical analysis). Likewise, vegetation cover increased by similar amounts, from similar initial values, in mown and unmown plots. This was true for vascular plants, fen-characteristic plants, bryophytes, six of eight Carex sedge species, common cottongrass Eriophorum angustifolium, purple moor grass Molinia arundinacea and common reed Phragmites australis. After five years, mown plots contained more vascular plant species than unmown plots (26 vs 18 species/m2) and more fen-characteristic plant species (14 vs 10 species/m2). Before mowing, species richness was similar in all plots (vascular: 15; fen-characteristic: 7–8). In 1996, nine pairs of 9 m2 plots were established in a degraded fen. Every August until 2001 vegetation was cut by hand (and cuttings removed) in one random plot/pair. The other plots were not cut. All plots had been cleared of trees and shrubs and were grazed every summer (approximately 50 cows/ha). In 1996 (before mowing) and 2001, cover of every plant species was estimated in one 1 m2 quadrat/plot.
- Godwin H. (1941) Studies in the ecology of Wicken Fen: IV. Crop-taking experiments. Journal of Ecology, 29, 83-106
- Robroek B.J.M., van Ruijven J., Schouten M.G.C., Breeuwer A., Crushell P.H., Berendse F. & Limpens J. (2009) Sphagnum reintroduction in degraded peatlands: the effects of aggregation, species identity and water table. Basic and Applied Ecology, 10, 697-706
- Mälson K., Sundberg S. & Rydin H. (2010) Peat disturbance, mowing, and ditch blocking as tools in rich fen restoration. Restoration Ecology, 18, 469-478
- Sundberg S. (2011) Quick target vegetation recovery after restorative shrub removal and mowing in a calcareous fen. Restoration Ecology, 20, 331-338