Use covers/barriers to control problematic plants: freshwater marshes

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

Effectiveness

40%
Certainty

30%
Harms

13%

Calculating overall effectiveness category

Background information and definitions

Covers such as plastic sheeting, fabric sheeting, wood chips or straw mulch could be used to control problematic plants. These may act as direct physical barriers, temporarily covering the ground or water surface to prevent seeds from settling and establishing. Barriers could also be used to modify environmental conditions to the detriment of problematic species. Shading or opaque screens can limit photosynthesis. In areas where the sun is strong, black plastic placed on the soil/sediment surface can increase temperatures to kill problematic plants and their seeds (a technique known as solarization; Katan & DeVay 1991). Covers can be anchored underwater, if necessary.

Caution: Covers will also affect, and may kill, desirable plant species. Temporary application, when a site is most vulnerable to invasion by problematic plants, could solve this problem. Covers may need to be punctured to allow gas to escape.

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

Related actions: Add surface mulch or Add cover other than mulch, primarily to benefit desirable plants rather than harm problematic plants; Add surface mulch to complement planting; Add cover other than mulch to complement planting.

^{Katan J. & DeVay J.E. (1991) Soil solarization: historical perspectives, principles, and uses. Pages 23–37 in: J. Katan and J.E. DeVay (eds.) Soil Solarization. Boca Raton, Florida.}

Study locations

Key messages

One study evaluated the effects, on vegetation, of using covers or barriers to control problematic plants in freshwater marshes. The study was in Canada.

VEGETATION COMMUNITY

VEGETATION ABUNDANCE

Overall abundance (1 study): One replicated, randomized, paired, controlled, before-and-after study in iris-invaded lakeshore marshes in Canada reported that covering plots with rubber sheeting after cutting back yellow iris Iris pseudacorus prevented most vegetation regrowth in an intermittently flooded marsh, but had no clear effect in a permanently flooded marsh.

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, before-and-after study in 2014–2015 in two lakeshore marshes cleared of yellow flag iris Iris pseudacorus in British Columbia, Canada (Tarasoff et al. 2016) reported that the effect of covering plots on recolonizing vegetation depended on the water level. Statistical significance was not assessed. Initially, all study plots were completely covered by invasive yellow flag iris. This was clipped to ground level. One year later, in the intermittently flooded marsh, covered plots had approximately 7% vegetation cover (yellow flag iris seedlings and broadleaf cattail Typha latifolia; species cover not quantified). In contrast, open plots had 100% cover of yellow flag iris. Meanwhile, in the permanently flooded marsh, both covered and open plots had approximately 5% vegetation cover (yellow flag iris seedlings and broadleaf cattail; species cover not quantified). Methods: Nine pairs of plots (approximately 1 m²) were established in iris-dominated marshes on the shores of two lakes. In June 2014, yellow flag iris was cut to 0–4 cm above the sediment in all plots. Cuttings were removed. Then, one random plot/pair was covered with an impermeable rubber sheet for 150 days. Vegetation cover was surveyed in July 2015.
Study and other actions tested
Referenced paper
Tarasoff C.S., Streichert K., Gardner W., Heise B., Church J. & Pypker T.G. (2016) Assessing benthic barriers vs. aggressive cutting as effective yellow flag iris (Iris pseudacorus) control mechanisms. Invasive Plant Science and Management, 9, 229-234.

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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