Use herbicide to maintain or restore disturbance: freshwater swamps

How is the evidence assessed?
  • Effectiveness
    not assessed
  • Certainty
    not assessed
  • Harms
    not assessed

Study locations

Key messages

  • One study evaluated the effects, on vegetation, of using herbicide to maintain or restore disturbance in freshwater swamps. The study was in the USA.

VEGETATION COMMUNITY

 

VEGETATION ABUNDANCE

  • Herb abundance (1 study): One replicated, randomized, controlled, before-and-after, site comparison study of freshwater swamps in the USA found that applying herbicide to woody vegetation (after cutting it) had no significant effect on herbaceous ground cover one year later: there were similar changes in treated and untreated swamps.

VEGETATION STRUCTURE

  • Basal area (1 study): One replicated, randomized, controlled, before-and-after, site comparison study of freshwater swamps in the USA found that applying herbicide to woody vegetation (after cutting it) had no significant effect on the basal area of woody vegetation one year later: there were similar changes in treated and untreated swamps.
  • Canopy cover (1 study): The same study found that applying herbicide to woody vegetation (after cutting it) reduced canopy cover – to similar levels as in high-quality swamps after one year.

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

  1. A replicated, randomized, controlled, before-and-after, site comparison study in 2009–2011 of 19 ephemeral freshwater swamps in Florida, USA (Gorman et al. 2013) found that cutting and applying herbicide to midstory vegetation reduced canopy cover one year later, but had no significant effect on ground cover or basal area. One year before intervention, treated swamps had higher canopy cover (55%) than untreated high-quality swamps (36%). One year after intervention, canopy cover in treated swamps had declined to 41%: not significantly different from the 37% cover in high-quality swamps. In untreated low-quality swamps, canopy cover was 49–54%. Other vegetation metrics showed statistically similar responses over time (one year before vs one year after intervention) in both treated and untreated swamps. This was true for herbaceous ground cover (treated: 23% vs 17%; high-quality: 48% vs 37%; low-quality: 22% vs 19%) and the basal area of woody vegetation (treated: 14% vs 12%; high-quality: 10% vs 9%; low-quality: 16% vs 15%). Methods: In August–September 2010, excessive woody vegetation – that had grown following suppression of dry season fires – was removed from eight swamps (<6 ha). Midstory vegetation (<12.7 cm trunk diameter) was cut and removed, then herbicide (triclopyr) was applied to stumps. Note that this study evaluates the combined effect of cutting and applying herbicide. Vegetation was not treated in seven additional overgrown swamps (“low-quality habitat” for wildlife) or in four additional swamps without a dense midstory (“high-quality habitat” for wildlife). Vegetation was surveyed in each swamp in autumn 2009 and 2011. Canopy cover included the midstory and overstory. Herb cover was estimated in one 0.1-m2 quadrat/swamp.

    Study and other actions tested
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?

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Marsh and Swamp Conservation

This Action forms part of the Action Synopsis:

Marsh and Swamp Conservation
Marsh and Swamp Conservation

Marsh and Swamp Conservation - Published 2021

Marsh and Swamp Synopsis

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