Change season/timing of cutting/mowing

Overall effectiveness category Unknown effectiveness (limited evidence)
Number of studies: 2
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How is the evidence assessed?

Effectiveness

50%
Certainty

25%
Harms

10%

Calculating overall effectiveness category

Background information and definitions

Studies in this section compare the effects of cutting/mowing at different times of year, given a fixed cutting frequency (i.e. number of cuts each year). Mowing could have different effects on peatland vegetation depending on the season in which it is done. For example, if an undesirable plant is only present above ground in some seasons, mowing must be done at the right time to damage this plant. The timing of cutting will also affect nutrient removal. Usually, more nutrients will be removed by cutting in summer or autumn: before the above-ground biomass of annual plants dies off and nutrients are stored in underground organs. In some peatlands, mowing has shifted from the traditional season (Rowell et al. 1985).

Key peatland types where this action may be appropriate: bogs, fens/fen meadows, tropical peat swamps.

_{Rowell T.A., Guarino L. & Harvey H.J. (1985) The experimental management of vegetation at Wicken Fen, Cambridgeshire. Journal of Applied Ecology, 22, 217–227.}

Study locations

Key messages

Two studies evaluated the effects on peatland vegetation of mowing or cutting in different seasons. One study was in a fen meadow and one was in a peatland with mixed vegetation.
Plant community composition (2 studies): One replicated, randomized, paired, before-and after study in a fen meadow in the UK reported that changes in plant community composition were typically similar in spring-, summer- and autumn-mown plots. However, one study in a peatland in the Netherlands reported that summer- and winter-mown areas developed cover of different plant community types.
Overall plant richness/diversity (1 study): One replicated, randomized, paired, before-and after study in a fen meadow in the UK found that plant species richness increased more, over two years, in summer-mown plots than spring- or autumn-mown plots.

About key messages

Key messages provide a descriptive index to studies we have found that test this intervention.

Studies are not directly comparable or of equal value. When making decisions based on this evidence, you should consider factors such as study size, study design, reported metrics and relevance of the study to your situation, rather than simply counting the number of studies that support a particular interpretation.

Supporting evidence from individual studies

A replicated, randomized, paired, before-and-after study in 1980–1982 in a fen meadow in England, UK (Rowell et al. 1985) reported that mowing in different seasons generally produced similar changes in plant community composition, but found that summer-mown plots experienced larger increases in plant species richness than spring- and autumn-mown plots. Over two years, changes in overall plant community composition were similar in spring-, summer- and autumn-mown plots in four of six cases. In one plant community, autumn-mown plots developed different plant communities to spring- and summer-mown plots (data reported as graphical analyses; results not tested for statistical significance). Species richness increased significantly more in summer-mown plots than spring- or autumn-mown plots in three of four cases (summer-mown: 0.8–1.4 extra species; spring-mown: 0.2–0.5 extra species; autumn-mown: 0.2–0.3 extra species/250 cm²). In 1980–1982, annual mowing treatments were randomly applied to four 25 m² plots in each of 10 blocks (situated in two different fen meadow community types). In each block, one plot was spring-mown (May), two were summer-mown (July) and one was autumn-mown (September). Cuttings were removed. Immediately before each mowing, vascular plant species were recorded in sixteen 250 cm²quadrats/plot.
Study and other actions tested
Referenced paper
Rowell T.A., Guarino L., & Harvey H.J. (1985) The experimental management of vegetation at Wicken Fen, Cambridgeshire. Journal of Applied Ecology, 22, 217-227.
A study in 1956–1989 in a historically mined peatland in the Netherlands (van Diggelen et al. 1996) reported that summer- and winter-mown areas developed different types of plant communities. No statistical tests were carried out. Initially, areas destined for each mowing regime contained similar vegetation types: 42–52% of the surface was covered by reedbeds, 28–30% by fen vegetation (mostly alkaline ‘rich’ fens), 20–25% by meadows and 0% by bogs. After approximately 30 years of mowing, summer-mown areas had developed into acidic poor fens (62%) and bogs (21%), with some reedbeds (14%). In contrast, winter-mown areas had mainly developed into reedbeds (68%) and poor fens (32%). In 1989, vegetation was mapped in 5 ha of summer-mown peatland and 30 ha of winter-mown peatland. This was compared to maps created in 1956. Vegetation was developing on pools created by historical peat extraction. By 1989 the peatland had been mown for approximately 30 years, but it was not clear whether the peatland was abandoned or mown before this.
Study and other actions tested
Referenced paper
Van Diggelen R., Molenaar W.J. & Kooijman A.M. (1996) Vegetation succession in a floating mire in relation to management and hydrology. Journal of Vegetation Science, 7, 809-820.

Please cite as:

Taylor, N.G., Grillas, P. & Sutherland, W.J. (2020) Peatland Conservation. Pages 367-430 in: W.J. Sutherland, L.V. Dicks, S.O. Petrovan & R.K. Smith (eds) What Works in Conservation 2020. Open Book Publishers, Cambridge, UK.

Where has this evidence come from?

List of journals searched by synopsis

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This Action forms part of the Action Synopsis:

Peatland Conservation

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