Objective: (re)vegetate salt marshes with target vegetation
Definitions
● Corm = a swollen, underground stem base covered by scale-like leaves, capable of
producing new growth in suitable conditions.
● Seed bank = the natural storage of seeds in soil or sediment, which can be
dormant.
1. Description
Created or restored salt marshes may need a ‘helping hand’ if vegetation is not colonising naturally, or is colonising slowly. Target vegetation can be introduced by physically planting new plants, seeds or vegetation fragments, or by depositing plant material containing target species. Sites where active revegetation may be particularly useful include those with a depleted seed bank of target species (e.g. sites historically used for agriculture or created by placement of dredged material), those without a ready source of colonising vegetation (e.g. a long way from, or up-current of, existing salt marshes), and those susceptible to invasion by non-native species (which may readily colonise bare sediment but not sites with native vegetation cover; Tarsa et al. , 2022). Vegetation can also help salt marshes keep pace with rising sea levels (Davis et al. , 2017). Note that there are several options available to stimulate growth of salt marsh vegetation without directly introducing it, which are not addressed here. These include adding fertiliser, adding mulch, planting nurse plants (see Taylor et al., 2021) and reprofiling (see Cutts et al., 2024). Managing any cause of vegetation loss – from recreational activity to livestock grazing to pollution – can also help (Taylor et al., 2021). Many coastal habitats naturally have little or no vegetation and provide important resources for shorebirds and other wildlife in this state. Managers should avoid the temptation to revegetate these habitats. For example, in parts of the upper tidal flats on the Yellow Sea coast, China, sparsely vegetated alkaline flats (mostly Suaeda salsa ), rather than densely vegetated or completely unvegetated areas, provide nesting habitat for shorebirds such as Saunders's Gull Saundersilarus saundersi (David Melville, pers. comm.).
2. Evidence for effects on biodiversity
Vegetation : Planting seeds or whole plants has generally been shown to be successful for revegetating salt marshes (Taylor et al. , 2021). A global review of salt marsh restoration studies reported an average survival rate of 65% (range 0% to ≥95%) for planted and sown non -woody vegetation in 64 cases (Bayraktarov et al. , 2016). At a site in the Netherlands, adding a layer of driftline material, containing seeds and vegetative fragments of salt marsh species, increased the number of target species during the first four years. However, after six years,
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