Action: Remove plant litter to maintain or restore disturbance
- Two studies evaluated the effects on peatland vegetation of removing plant litter to maintain or restore disturbance. One study was in fen meadow and one was in a fen.
- Plant community composition (2 studies): Two replicated, controlled studies (one randomized, one paired, before-and-after) in a fen meadow in Germany and a fen in Czech Republic found that removing plant litter did not affect plant community composition.
- Vegetation cover (1 study): One replicated, paired, controlled, before-and-after study in a fen in the Czech Republic found that removing plant litter did not affect bryophyte or tall moor grass cover.
- Overall plant richness/diversity (2 studies): One replicated, randomized, controlled study in a fen meadow in Germany reported that removing plant litter increased plant species richness and diversity. However, one replicated, paired, controlled, before-and-after study in a fen in the Czech Republic found that removing litter did not affect vascular plant diversity.
Traditional management such as mowing, grazing and burning can prevent build up of plant litter (dead material). Some fens and fen meadows have been mown for hundreds of years to produce animal feed or bedding (Güsewell 2003). However, many historically cut peatlands have been abandoned over the past 60 years, especially those in remote areas (Middleton et al. 2006). Accumulation of litter may affect the growth of some or all plants by influencing temperature, light and nutrient availability (Weltzin et al. 2005). Litter also creates a physical barrier above growing seedlings and below any seeds that fall on top of it (Facelli & Pickett 1991).
Removing vegetation litter by hand may mimic some of the disturbance caused by traditional management. To be included as evidence in this section, studies must have examined the effect of litter removal alone (not, for example, the effect of removing litter from mown plots).
Caution: Disturbance is not desirable on all peatlands. Fen meadows and some fens may benefit from disturbance. Many other fens, bogs and peat swamps will not. In fact, accumulation of dead plant matter is fundamental to the process of peat formation.
Related action: prescribed burning, which will clear plant litter as part of its wider effects on peatland vegetation.
Facelli J.M. & Pickett S.T.A. (1991) Plant litter: its dynamics and effects on plant community structure. The Botanical Review, 57, 1–32.
Güsewell S. (2003) Management of Phragmites australis in Swiss fen meadows by mowing in early summer. Wetlands Ecology and Management, 11, 433–445.
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.
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 replicated, randomized, controlled study in 1996–1998 in a degraded fen meadow in Germany (Jensen & Meyer 2001) reported that plots cleared of plant litter had higher plant species richness and diversity than plots where litter was not removed, but that community composition was similar under both treatments. These results are not based on tests of statistical significance. Over three years, litter-removal plots contained 18–19 plant species vs 15–16 in non-removal plots. Plant diversity was also higher in litter-removal plots (data reported as a diversity index). The overall plant community composition was initially similar in all plots, then changed over time but in a similar way in litter-removal and non-removal plots (data reported as a graphical analysis). In 1996, ten 2 m2 plots were established in an abandoned fen meadow. In May 1996, 1997 and 1998, all dead plant material was removed from five random plots. Dead plant material was left in the other five plots. Cover of every plant species was estimated annually, after litter removal, in each plot.
A replicated, paired, controlled, before-and-after study in 2002–2007 in a degraded grassy fen in the Czech Republic (Hájkova et al. 2009) found that removing plant litter had no effect on community composition, richness of vascular plants, bryophyte cover or cover of dominant tall moor grass Molinia arundinacea. In plots where litter was removed, the overall plant community composition did not change significantly over five years (data reported as graphical analyses). There was also no change in richness of vascular plants (8–9 species/m2 across all years) and fen-characteristic vascular plants (data not reported), bryophyte cover (9–33% across all years) and moor grass cover (data not reported). These measures also remained stable in plots where litter was not removed. In May 2002, five pairs of 2.5 x 2.5 m plots were established in an abandoned fen, dominated by tall moor grass. Each May until 2007, dead plant litter was raked from one plot/pair. Plant litter was left in the other plots. Each year before litter removal, cover of every plant species was estimated in a 1 m2 quadrat in the centre of each plot.
- Jensen K. & Meyer C. (2001) Effects of light competition and litter on the performance of Viola palustris and on species composition and diversity of an abandoned fen meadow. Plant Ecology, 155, 169-181
- Hájkova P., Hájek M. & Kintrová K. (2009) How can we effectively restore species richness and natural composition of a Molinia invaded fen? Journal of Applied Ecology, 46, 417-425