Physically remove problematic plants: brackish/salt marshes
Overall effectiveness category Unknown effectiveness (limited evidence)
Number of studies: 1
Background information and definitions
This action considers complete physical removal of problematic plants, i.e. pulling up or digging up entire plants, or scraping living vegetation from the marsh surface. Removal may be targeted to individual organisms, or applied to the whole plant community. The most appropriate removal method will depend on the species to be removed, and the site conditions (e.g. Tobias et al. 2016).
If plants are completely removed, including roots where applicable, immediate regrowth will be prevented (although long-term recolonization from the seed bank or from neighbouring sites is possible). For some species, disposing of the problem plants off-site may help to prevent regrowth, but disposal should be done carefully to avoid causing an invasion elsewhere (Stevens et al. 1997).
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: Remove surface soil/sediment, including any plants on it.
Stevens K.J., Peterson R.L. & Stephenson G.R. (1997) Vegetative propagation and the tissues involved in lateral spread of Lythrum salicaria. Aquatic Botany, 56, 11–24.
Tobias V.D., Block G. & Laca E.A. (2016) Controlling perennial pepperweed (Lepidium latifolium) in a brackish tidal marsh. Wetlands Ecology and Management, 24, 411–418.
Supporting evidence from individual studies
A replicated, randomized, paired, controlled, before-and-after study in 2005–2007 in three brackish and salt marshes invaded by pepperweed Lepidium latifolium in California, USA (Boyer & Burdick 2010) found that physically removing pepperweed before spraying herbicide increased native plant cover more than spraying alone. Averaged over the two years following intervention, cleared/sprayed plots had greater cover of native plants (year one: 26–124%; year two: 33–195%) than plots that were only sprayed (year one: 10–67%; year two: 19–113%). In contrast, cleared/sprayed plots had lower pepperweed cover (year one: 0–14%; year two: 5–44%) than plots that were only sprayed (year one: 2–60%; year two: 25–88%). Before intervention, plots destined for each treatment had statistically similar cover of native plants (10–33%) and pepperweed (90–100%). For data on the cover of other individual plant species, see original paper. Methods: In April 2005, five sets of 2 x 2 m plots were established each of three pepperweed-invaded marshes. In each set, there was one replicate where pepperweed was removed (including roots to 20 cm depth) before spraying regrowth with herbicide (1.25% glyphosate), and one replicate that was only sprayed with herbicide. Treatments were randomly allocated to plots. Vegetation cover was measured before (April 2005) and quarterly for two years after (April 2007) intervention, in 1-m2 quadrats.Study and other actions tested