Use cutting/mowing to control problematic herbaceous plants: brackish/salt marshes

Overall effectiveness category Unknown effectiveness (limited evidence)
Number of studies: 1
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How is the evidence assessed?

Effectiveness

33%
Certainty

30%
Harms

10%

Calculating overall effectiveness category

Background information and definitions

Cutting or mowing refers to 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, or targeted at specific problematic plants. Whilst cutting may not kill the targeted plants, it may weaken them and may provide desirable plants with an opportunity to grow and outcompete problematic plants. The cut plant material could be left on site or removed and used for construction or energy production, for example (Lishawa et al. 2015). Caution: Mowing with heavy machinery could damage wetland soil and vegetation. Cutting by hand or with specialized vehicles might cause less damage.

This action includes evidence for all forms of cutting/mowing to control problematic plants, but bear in mind that the effects might be highly dependent on how the cutting/mowing is carried out (e.g. extent, timing, frequency, duration, and whether cuttings are left in place or removed) and site conditions (e.g. nutrient availability and water levels) (Rolletschek et al. 2000; Weltzin et al. 2005; Russell & Kraaij 2008; Fogli et al. 2014).

For this action, “vegetation” refers to overall or non-target vegetation. Studies that only report responses of target problematic plants have not been summarized.

^{Fogli S., Brancaleoni L., Lambertini C. & Gerdol R. (2014) Mowing regime has different effects on reed stands in relation to habitat. Journal of Environmental Management, 134, 56–62.}

^{Lishawa S.C., Lawrence B.A., Albert D.A. & Tuchman N.C. (2015) Biomass harvest of invasive Typha promotes plant diversity in a Great Lakes coastal wetland. Restoration Ecology, 23, 228–237.}

^{Rolletschek H., Rolletschek A., Hartzendorf T. & Kohl J. (2000) Physiological consequences of mowing and burning of Phragmites australis stands for rhizome ventilation and amino acid metabolism. Wetlands Ecology and Management, 8, 425–433.}

^{Russell I.A. & Kraaij T. (2008) Effects of cutting Phragmites australis along an inundation gradient, with implications for managing reed encroachment in a South African estuarine lake system. Wetlands Ecology and Management, 16, 383–393.}

^{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.}

Study locations

Key messages

One study evaluated the effects, on vegetation, of cutting/mowing problematic herbaceous plants or small shrubs in brackish/salt marshes. The study was in the USA.

VEGETATION COMMUNITY

Overall richness/diversity (1 study): One replicated, randomized, paired, controlled study in a saltgrass-dominated marsh in the USA found that mown and unmown plots had similar overall plant species richness after one year.

VEGETATION ABUNDANCE

Overall abundance (1 study): One replicated, randomized, paired, controlled study in a saltgrass-dominated marsh in the USA found that mown and unmown plots had similar overall vegetation cover after one year.
Individual species abundance (1 study): The same study found that six dominant herb species, other than the species being controlled, had similar cover in mown and unmown plots after one year.

VEGETATION STRUCTURE

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, controlled study in 1992–1993 in an ephemeral brackish marsh dominated by saltgrass Distichlis spicata in California, USA (De Szalay & Resh 1997) found that mown and unmown plots had similar plant species richness, similar overall vegetation cover, and similar cover of dominant plant species. After one year, overall plant species richness did not significantly differ between mown plots (3.2 species/m²) and unmown plots (3.1 species/m²). The same was true for cover of vegetation overall (mown: 98%; unmown: >99%), saltgrass (mown: 93%; unmown: 99%) and each of six other dominant herb species (mown: 0–7%; unmown: 0–5%). However, mown plots did contain a greater density of saltgrass (4,070 stems/m²) than unmown plots (1,770 stems/m²). Density was not reported for the other six dominant herb species. Methods: Ten pairs of 100-m² plots were established in an impounded brackish marsh, managed for waterfowl (autumn/winter flooding with spring/summer drawdown) but dominated by saltgrass. In August–September 1992, ten plots were hand-mown (one plot/pair; 50 m²/plot). Cuttings were not removed. The other plots were not mown. In August 1993, vegetation was surveyed in two 1-m² quadrats/plot. Cover estimates included live and dead standing plants.
Study and other actions tested
Referenced paper
de Szalay F.A. & Resh V.H. (1997) Responses of wetland invertebrates and plants important in waterfowl diets to burning and mowing of emergent vegetation. Wetlands, 17, 149-156.

Please cite as:

Taylor N.G., Grillas P., Smith R.K. & Sutherland W.J. (2021) Marsh and Swamp Conservation: Global Evidence for the Effects of Interventions to Conserve Marsh and Swamp Vegetation. Conservation Evidence Series Synopses. University of Cambridge, Cambridge, UK.

Where has this evidence come from?

List of journals searched by synopsis

All the journals searched for all synopses

This Action forms part of the Action Synopsis:

Marsh and Swamp Conservation

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