Introduce fragments of non-woody plants: brackish/saline wetlands

Overall effectiveness category Unknown effectiveness (limited evidence)
Number of studies: 3
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How is the evidence assessed?

Effectiveness

50%
Certainty

33%
Harms

3%

Calculating overall effectiveness category

Background information and definitions

This action involves introducing fragments of non-woody emergent plants to restore/create marshes or swamps. This includes unrooted cuttings, roots, tubers/bulbs/corms (underground storage organs), rhizomes (underground horizontal stems) or stolons/runners (above-ground horizontal stems). Vegetation fragments may be planted directly into the soil, or spread on the soil surface. Fragments may be obtained from plants raised in greenhouses/laboratories, or collected from natural sites (with potential damage to donor site; Laegdsgaard 2002).

Introduction of target vegetation might be useful in severely degraded or bare sites – which may lack remnant plants or seed banks to kick start revegetation with desirable species, and may be at risk of being taken over by undesirable species (Brown & Bedford 1997). It might also be useful in isolated wetlands, far from sources of marsh or swamp plant propagules. However, note that up-front costs can be high.

The effects of planting may be highly dependent on the environmental conditions in each study. Questions you might ask when interpreting the evidence include: Is the study site degraded? Where and when were fragments introduced? Was there any intervention to improve conditions before planting? What were the environmental conditions over the duration of the study?

The scope of this action does not include planting nurse plants; planting submerged or floating plants; planting to restore bogs, fens, fen meadows or peat swamp forests (see Taylor et al. 2018); or planting facultative wetland plants in upland sites. In contrast, the scope does include planting non-native species to conserve marshes or swamps – whilst acknowledging that this is often considered ethically unacceptable due to the risk of invasion (e.g. Ren et al. 2009).

^{Brown S.C. & Bedford B.L. (1997) Restoration of wetland vegetation with transplanted wetland soil: an experimental study. Wetlands, 17, 424–437.}

^{Laegdsgaard P. (2002) Recovery of small denuded patches of the dominant NSW coastal saltmarsh species (Sporobolus virginicus and Sarcocornia quinqueflora) and implications for restoration using donor sites. Ecological Management & Restoration, 3, 202–206.}

^{Ren H., Lu H., Shen W., Huang C., Guo Q., Li Z. & Jian S. (2009) Sonneratia apetala Buch.Ham in the mangrove ecosystems of China: an invasive species or restoration species? Ecological Engineering, 35, 1243–1248.}

^{Taylor N.G., Grillas P. & Sutherland W.J. (2018) Peatland Conservation: Global Evidence for the Effects of Interventions to Conserve Peatland Vegetation. Synopses of Conservation Evidence Series. University of Cambridge, Cambridge.}

Study locations

Key messages

Three studies evaluated the effects, on vegetation, of introducing fragments of emergent, non-woody plants to brackish/saline wetlands. Two studies were in one bog in Canada. One study was in China.

VEGETATION COMMUNITY

VEGETATION ABUNDANCE

Overall abundance (2 studies): Two replicated, paired, controlled, before-and-after studies in salt-contaminated bogs in Canada found that plots planted with rhizomes or sown with fragments of salt marsh herbs had similar overall vegetation biomass, after one year, to plots that had not been planted or sown.
Herb abundance (1 study): One replicated, paired, controlled, before-and-after studies in salt-contaminated bogs in Canada found that plots sown with fragments of salt marsh herbs had greater overall cover of the introduced species, after one year, to unsown plots. However, biomass of the introduced species did not significantly differ between sown and unsown plots.
Individual species abundance (2 studies): Two replicated studies (one also before-and-after) in brackish/saline wetlands in Canada and China simply quantified the abundance of herb species, over one year or growing season after planting herb fragments.

VEGETATION STRUCTURE

OTHER

Germination/emergence (1 study): One replicated study on a tidal flat in China reported that at least 25% of bulrush Scirpus mariqueter corms (bulb-like organs) produced shoots within the first growing season after planting.

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, paired, controlled, before-and-after study in 2011–2012 in two salt-contaminated bogs in New Brunswick, Canada (Emond et al. 2016) found that plots planted with rhizomes of salt marsh herbs contained a similar overall vegetation biomass to unplanted plots. Plots were initially bare peat. After one year, total above-ground vegetation biomass did not significantly differ between plots planted with chaffy sedge Carex paleacea (150 g/m²), plots planted with prairie cordgrass Spartina pectinata (66 g/m²) and unplanted plots (122 g/m²). In the plots where it was planted, chaffy sedge biomass was 120 g/m² and it had 9–17% cover. In the plots where it was planted, prairie cordgrass biomass was 24 g/m², and it had 2–3% cover. Methods: In June 2011, forty-eight 9-m² plots were established across the two bogs, in four blocks of twelve. Plugs of rhizomes and soil (5 cm diameter) from an adjacent salt marsh were added to 32 of the plots (eight plots/block; four with sedge rhizomes and four with cordgrass rhizomes). Phosphorous fertilizer and lime were each applied to one plot per treatment. In July 2012, vegetation cover was recorded in the central 4 m² of each plot. Vegetation was cut from one 250-cm² quadrat/plot, then dried and weighed. This study shared part of the experimental set-up used in (2).
Study and other actions tested
Referenced paper
Emond C., Lapointe L., Hugron S. & Rochefort L. (2016) Reintroduction of salt marsh vegetation and phosphorus fertilisation improve plant colonisation on seawater-contaminated cutover bogs. Mires and Peat, 18, Article-17.
A replicated, paired, controlled, before-and-after study in 2011–2012 in two salt-contaminated bogs in New Brunswick, Canada (Emond et al. 2016) found that plots sown with salt marsh vegetation fragments developed greater cover of introduced herb species than unsown plots, but similar biomass of these species and vegetation overall. Before sowing, plots were bare peat. After one year, sown plots had greater cover of introduced herb species (i.e. the 15 species present at the donor site; 1–4%) than unsown plots (<1%). However, there was no significant difference between treatments in biomass of introduced species (sown: 12–14 g/m²; not sown: 0 g/m²) or vegetation overall (sown: 126–155 g/m²; not sown: 122 g/m²). Methods: In June 2011, forty-eight 9-m² plots were established across the two bogs, in four blocks of twelve. Vegetation fragments from an adjacent salt marsh were added to 32 of the plots (eight plots/block; four in July, four in August). Phosphorous fertilizer and lime were each applied to half of the plots. In July 2012, vegetation cover was recorded in the central 4 m² of each plot. Vegetation was cut from one 250-cm² quadrat/plot, then dried and weighed. This study shared part of the experimental set-up used in (1).
Study and other actions tested
Referenced paper
Emond C., Lapointe L., Hugron S. & Rochefort L. (2016) Reintroduction of salt marsh vegetation and phosphorus fertilisation improve plant colonisation on seawater-contaminated cutover bogs. Mires and Peat, 18, Article-17.
A replicated study in 2014 on a recently deposited tidal flat in eastern China (Hu et al. 2016) reported that planted bulrush Scirpus mariqueter corms (swollen underground stems, similar to bulbs) successfully emerged to produce above-ground parts. Over the first growing season after planting, the emergence rate of planted corms was at least 25–42% (depending on planting density, and based on the maximum number of seedlings observed at any one time). At the end of the growing season, planted areas contained 73–216 bulrush shoots/m². The final shoot density was significantly greater where more corms had been planted. Methods: In March–April 2014, field-collected bulrush corms were planted into a recent accumulation of intertidal sediment in the Yangtze estuary. Three 400-m² plots were each planted with a different density of corms: 15, 30 or 60 corms/m². Corms were planted 5 cm deep. Bulrush seedlings and shoots were counted twice each month until October, in ten 4-m² quadrats/plot.
Study and other actions tested
Referenced paper
Hu Z., Ma Q., Cao H., Zhang Z., Tang C., Zhang L. & Ge Z. (2016) A trial study on revegetation of the native Scirpus mariqueter population in the coastal wetland of the Yangtze Estuary. Ecological Science, 35, 1-7.

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

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This Action forms part of the Action Synopsis:

Marsh and Swamp Conservation

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