Remove plant litter: freshwater marshes
Overall effectiveness category Unknown effectiveness (limited evidence)
Number of studies: 1
Background information and definitions
Accumulation of dead plant matter, or litter, can cause undesirable changes to marsh plant communities. Litter can affect temperature, light and nutrient availability (Weltzin et al. 2005) and act as a barrier to seedlings from below and seeds from above (Facelli & Pickett 1991). Litter removal may be necessary after abandonment or suppression of disturbance.
Caution: Litter accumulation is an important process in some wetlands, contributing organic matter to the soil. Where it is desirable to remove litter, removal by hand may cause less damage to soils and vegetation than using heavy machinery. Be aware that seeds of desirable plants may be removed along with the litter.
To be summarized as evidence for this action, studies must have examined the effect of litter removal alone (not, for example, the effect of removing litter from mown plots, or the combined effect of mowing and litter removal).
Related actions: Cut/mow herbaceous plants to maintain or restore disturbance and Use prescribed fire to maintain or restore disturbance, both of which could help to clear plant litter.
Facelli J.M. & Pickett S.T.A. (1991) Plant litter: its dynamics and effects on plant community structure. The Botanical Review, 57, 1–32.
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, paired, controlled study in 1992–1993 in five freshwater marshes undergoing restoration in New York State, USA (Brown & Bedford 1997) found that plots cleared of plant litter contained a more wetland-characteristic plant community and greater cover of wetland plant species than uncleared plots after one growing season, but that these effects disappeared after two growing seasons. After one growing season, cleared plots contained a plant community more characteristic of wetland conditions than uncleared plots (data reported as a wetland indicator index). Cleared plots also had greater total cover of wetland plants (cleared: 24%; uncleared: 19%). The number of wetland plant species did not significantly differ between treatments (cleared: 2.4; uncleared: 2.0 species/plot). After two growing seasons, all metrics were statistically similar under both treatments: community composition, wetland plant cover (cleared: 67%; uncleared: 54%) and wetland plant richness (cleared: 3.7; uncleared: 2.8 species/plot). Methods: In May 1992, twenty 0.25-m2 plots were established across five recently rewetted sites (drained for ≥40 years previously). In five plots (one plot/site), all surface litter and plant stems were removed. Litter was left in the other 15 plots (three plots/site). Plant species and cover were recorded in autumn 1992 and 1993.Study and other actions tested