Action: Use grazing to maintain or restore disturbance
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- Four studies evaluated the effects, on peatland vegetation, of using grazing to maintain or restore disturbance. All four studies were in fens or fen meadows. N.B. Grazing in peatlands with no history of disturbance is considered as a separate action.
- Plant community composition (1 study): One replicated, paired, site comparison study in Germany found that the overall plant community composition differed between grazed and mown fen meadows.
- Characteristic plants (3 studies): One replicated, paired, controlled study in Germany reported that the abundance of bog/fen-characteristic plants was similar in grazed and ungrazed fen meadows. One replicated before-and-after study in a fen in the UK reported that cover of fen-characteristic mosses did not change after grazers were introduced. One replicated, paired, site comparison study, also in Germany, found that grazed fen meadows contained fewer fen-characteristic plant species than mown meadows.
- Herb cover (2 studies): Two before-and-after studies in fens in the UK reported that grazing increased cover of some herb groups (cottongrasses, sedges or all grass-like plants). One of the studies found that grazing reduced purple moor grass cover, but the other found that grazing typically had no effect.
- Moss cover (2 studies): One replicated before-and-after study in a fen in the UK reported that cover of fen-characteristic mosses did not change after grazers were introduced. One controlled, before-and-after study in a fen in the UK found that grazing reduced Sphagnum moss cover.
- Tree/shrub cover (2 studies): Of two before-and-after studies in fens in the UK, one found that grazing reduced shrub cover but the other found that grazing typically had no effect on shrub cover.
- Overall plant richness/diversity (3 studies): Of two before-and-after studies in fens in the UK, one found that plant species richness increased after grazing was reinstated but the other reported that there was typically no effect. One replicated, paired, site comparison study in Germany found that grazed fen meadows contained fewer plant species than mown meadows.
Regular disturbance may maintain vegetation in a desirable, semi-natural state – particularly in fen meadows and some fens (Middleton 2012). Disturbance can clear dominant plants such as trees and shrubs, maintain light availability and control nutrient levels. This can favour a plant community rich in plant species and/or peatland characteristic species. Therefore, conservationists may sometimes want to actively maintain or restore disturbance. Grazing by large vertebrates (e.g. sheep or cows) could be one way to do this.
Grazing itself may be the disturbance that has been reduced. Some peatlands have been historically grazed, usually at low intensities. Over the last 60 years many have been abandoned, especially those in remote areas (Middleton et al. 2006).
Caution: Disturbance is not desirable on all peatlands. Fen meadows and some fens may benefit from disturbance, but many other fens, bogs and peat swamps will not. Careful management of grazing (e.g. species used, density, timing) may be necessary.
Related actions: use grazing to control problematic plants whose growth is not attributed to loss of traditional management; reduce intensity of grazing; change type of livestock; change season/timing of grazing.
Middleton B., Holsten B. & van Diggelen R. (2006) Biodiversity management of fens and fen meadows by grazing, cutting and burning. Applied Vegetation Science, 9, 307–316.
Middleton B.A. (2012) Rediscovering traditional vegetation management in preserves: trading experiences between cultures and continents. Biological Conservation, 158, 750–760.
Supporting evidence from individual studies
A replicated, paired, site comparison study in 32 fen meadows in Germany (Stammel et al. 2003) found that grazed meadows contained a significantly different plant community with fewer species than mown meadows, but there was no difference in vegetation height or biomass. Meadows grazed or mown for at least 10 years had different overall plant communities (data reported as a graphical analysis). Grazed meadows contained fewer plant species than mown meadows, per meadow (71 vs 79) and per 25 m2 plot (43 vs 51), and fewer fen-characteristic plant species (18 vs 19 species/plot). Meadows did not differ significantly in vegetation height (grazed: 19; mown: 24 cm) or above-ground biomass (grazed: 954; mown: 1,103 g/m2). Of the 32 studied meadows, 16 were open to cattle (<0.5/ha) each summer and 16 were mown each autumn. In August (year not reported), cover of every plant species was recorded in 25 m2 plots: 58 across the grazed meadows and 51 across the mown meadows. Vegetation height was measured at three points in each meadow. Biomass was cut from three 25 x 25 cm quadrats then dried and weighed.
A replicated, paired, controlled study in 2001–2005 in a degraded fen meadow in Germany (Rasran et al. 2007) reported that grazing had no effect on the abundance of bog/fen-characteristic plants. This result is not based on a test of statistical significance. After five years, bog/fen-characteristic plants occurred in 0–3% of quadrats with 0–3% cover in both grazed and ungrazed plots. Variation between plots was related to topsoil stripping rather than grazing. In 2001, sixteen 6 x 6 m plots were established, in four blocks of four, in a drained, abandoned, nutrient-enriched fen meadow. Eight plots (two plots/block) were grazed by cattle (1.5 cattle/ha). The other eight plots were fenced to exclude cattle. None of these plots were sown with hay, but topsoil was stripped from four grazed and four ungrazed plots at the start of the experiment. Between 2002 and 2005, vegetation cover was estimated in 16 permanent 1 m2 quadrats/plot.
A replicated before-and-after study in 2011–2013 in a degraded fen in Wales, UK (Birch et al. 2015) found that grazing typically increased cover of grass-like plants but had no effect on other vegetation cover, diversity or structure. Cover of grasses/sedges/rushes significantly increased in two of three grazed plots (from 78–79% before grazing to 93–105% after 16–21 months of grazing). There was no significant change in two of three plots (but a decrease in the other) in purple moor grass Molinia caerulea cover, dwarf shrub cover, fen-characteristic moss cover, fen-characteristic herb cover, plant species richness, plant diversity or vegetation height. Three 10 x 10 m plots were established in an abandoned fen. From spring or summer 2012, each plot was grazed by cattle or ponies. Before grazing began (August 2011) and after 16–21 months (autumn 2013) measurements were taken in five 4 m2 quadrats/plot. Cover of every plant species was estimated, and vegetation height was measured, in the centre of each quadrat.
A controlled, before-and-after study in 2003–2012 in a historically grazed and recently burned fen in England, UK (Groome & Shaw 2015) found that grazing increased plant species richness, but reduced total vegetation cover and had mixed effects on cover of individual plant groups. Over nine years, grazed plots experienced a greater increase in plant species richness, but a smaller increase in total vegetation cover, than ungrazed plots (data not reported). For some vegetation, such as common cottongrass Eriophorum angustifolium and carnation sedge Carex panicea, cover increased more in grazed than ungrazed plots. For other vegetation, cover increased less in grazed plots. This included soft bog moss Sphagnum tenellum (data not reported), purple moor grass Molinia caerulea (before: 14–48%; grazed after: 14–43%; ungrazed after: 15–64%) and dwarf shrubs (before: 3–8%; grazed after: 22–37%; ungrazed after: 33–53%). In summer 2003, cover of every plant species was estimated in 174 permanent 1 m2 quadrats across the fen. From 2005, summer-autumn cattle grazing was reinstated (see original paper for details) except in three fenced exclosures. In 2010 and 2012, vegetation cover was re-surveyed in the quadrats (116 grazed, 58 ungrazed).
- Stammel B., Kiehl K. & Pfadenhauer J. (2003) Alternative management on fens, response of vegetation to grazing and mowing. Applied Vegetation Science, 6, 245-254
- Rasran L., Vogt K. & Jensen K. (2007) Effects of topsoil removal, seed transfer with plant material and moderate grazing on restoration of riparian fen grasslands. Applied Vegetation Science, 10, 451-460
- Birch K.S., Guest J.E., Shepherd S., Milner P., Jones P.S. & Hanson J. (2015) Responses of rich-fen Annex I and related habitats to restoration and management undertaken as part of the Anglesey & Lyn Fens LIFE Project. Technical Report No. 7. LIFE Project: Anglesey & Llyn Fens.
- Groome G.M. & Shaw P. (2015) Vegetation response to the reintroduction of cattle grazing on an English lowland valley mire and wet heath. Conservation Evidence, 12, 33-39