Use prescribed fire to control problematic plants: freshwater swamps

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

9%

Calculating overall effectiveness category

Background information and definitions

Prescribed burns can be used to manage problematic plants that may overgrow and outcompete desirable vegetation. By removing above-ground vegetation, fire can also be used to manage the physical vegetation structure (Flores et al. 2011). Prescribed burns may have only temporary effects: many plants can regrow from remaining stumps, roots or rhizomes (underground horizontal stems).

Potential benefits of management by prescribed burning should be weighed up against potential risks. For example, it can be difficult to control the intensity, duration and area of a prescribed burn: burning when the ground is wet and/or cold might be safer (Hackney & de la Cruz 1981). Burning can damage seed banks, and might produce apparently desirable changes in vegetation over the short term followed by a rapid return to a degraded state. Burning can also damage the physical habitat (e.g. by exposing sediments, increasing erosion and reducing accumulation of organic matter; McKee & Grace 2012) and may be harmful to animals like amphibians (Smith & Sutherland 2014) and birds (Flores et al. 2011).

The timing and duration of monitoring might be particularly important when evaluating the effects of this action. Burning might produce apparently desirable changes in vegetation over the short term, followed by a rapid return to a degraded state.

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

^{Flores C., Bounds D.L. & Ruby D.E. (2011) Does prescribed fire benefit wetland vegetation? Wetlands, 31, 35–44.}

^{Hackney C.T. & de la Cruz A.A. (1981) Effects of fire on brackish marsh communities: management implications. Wetlands, 1, 75–86.}

^{McKee K.L. & Grace J.B. (2012) Effects of Prescribed Burning on Marsh Elevation Change and the Risk of Wetland Loss. U.S. Geological Survey Open-File Report 2012-1031.}

^{Smith R.K. & Sutherland W.J. (2014) Amphibian Conservation: Global Evidence for the Effects of Interventions. Pelagic Publishing, Exeter, UK.}

Study locations

Key messages

One study evaluated the effects, on vegetation, of using prescribed fire to control problematic plants in freshwater swamps. The study was in the USA.

VEGETATION COMMUNITY

Overall richness/diversity (1 study): One replicated, randomized, controlled study aiming to restore a swamp in the USA found that burning canarygrass-invaded vegetation after spraying it with herbicide increased overall plant diversity, two growing seasons later, compared to spraying alone. However, burning had no significant effect on plant species richness.
Native/non-target richness/diversity (1 study): The same study found that burning canarygrass-invaded vegetation after spraying it with herbicide had no significant effect on native plant species richness, two growing seasons later, compared to spraying alone.

VEGETATION ABUNDANCE

Tree/shrub abundance (1 study): One replicated, randomized, controlled study aiming to restore a swamp in the USA found that burning canarygrass-invaded vegetation after spraying it with herbicide had no significant effect on the density of non-planted tree seedlings, two growing seasons later, compared to spraying alone.
Individual species abundance (1 study): The same study reported that burning canarygrass-invaded vegetation after spraying it with herbicide affected the abundance of some individual plant species two growing seasons later.

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, controlled study in 2002–2004 aiming to restore a swamp in a reed canarygrass Phalaris arundinacea stand in Wisconsin, USA (Hovick & Reinartz 2007) found that burning after spraying herbicide increased plant diversity more than spraying alone, but that burning had no additional effect on plant richness or the number of tree seedlings. After two growing seasons, the vegetation was more diverse in burned/sprayed plots than in plots that had only been sprayed (data reported as a diversity index). The treatments did not significantly differ in overall plant richness (burned/sprayed: 9.3; sprayed: 6.6 species/m²), native plant richness (burned/sprayed: 6.3; sprayed: 4.0 species/m²) or density of non-planted tree seedlings (burned/sprayed: 21; sprayed: 25 seedlings/m²). The study also reported differences between treatments in the abundance of individual plant species(statistical significance not assessed). For example, eastern willow herb Epilobium coloratum was more abundant in burned/sprayed plots (70% of quadrats; 10% cover) than sprayed plots (40% of quadrats; 6% cover). Reed canarygrass was less abundant in burned/sprayed plots (80% of quadrats; 34% cover) than sprayed plots (100% of quadrats; 73% cover). Methods: Twelve plots were established in a canarygrass-invaded wetland. All 12 plots were sprayed with herbicide (Roundup®) in November 2002, and planted with tree/shrub seedlings (roughly 1 seedling/m²) in spring 2003. Four random plots were also burned, before planting, in spring 2003. In August 2004, plant species and their cover were surveyed in ten 1-m² quadrats/treatment, ignoring planted trees/shrubs.
Study and other actions tested
Referenced paper
Hovick S.M. & Reinartz J.A. (2007) Restoring forest in wetlands dominated by reed canarygrass: the effects of pre-planting treatments on early survival of planted stock. Wetlands, 27, 24-39.

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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Use grazing to control problematic plants: brackish/saline swamps Action Link	No evidence found (no assessment)	0	Synopsis Link
Physically damage problematic plants: freshwater swamps Action Link	Unknown effectiveness (limited evidence)	2	Synopsis Link