Transplant or replace blocks of vegetation: freshwater marshes

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

Study locations

Key messages

  • Four studies evaluated the effects, on vegetation, of transplanting or replacing blocks of freshwater marsh vegetation. Three studies were in the USA. One study was in the UK.

VEGETATION COMMUNITY

  • Community composition (1 study): One replicated, paired, controlled study in rewetted marshes in the USA found that plots of transplanted marsh vegetation contained a plant community characteristic of wetter conditions than plots without transplants after one growing season – but not after two.
  • Overall richness/diversity (2 studies): One replicated, before-and-after study in the UK reported that plant species richness within transplanted freshwater marsh vegetation was similar before transplanting and six years later. There was a temporary increase in richness after one year. One replicated, paired, controlled study in rewetted freshwater marshes in the USA found that plots of transplanted marsh vegetation contained more wetland plant species than plots without transplants after one growing season – but that there was no significant difference after two.

VEGETATION ABUNDANCE

  • Overall abundance (1 study): One replicated, paired, controlled study in rewetted freshwater marshes in the USA found that plots of transplanted marsh vegetation had greater cover of wetland plants than plots without transplants, after 1–2 growing seasons.
  • Individual species abundance (2 studies): One replicated, site comparison study in a wet prairie in the USA found that after three growing seasons, the density of prairie cordgrass Spartina pectinata stems was lower in transplanted sods than in pristine or source prairies. One before-and-after study of transplanted freshwater marsh vegetation in the UK reported changes in the frequency of individual plant species from before to six years after transplanting.

VEGETATION STRUCTURE

  • Height (1 study): One replicated, site comparison study in a wet prairie in the USA found that after three growing seasons, prairie cordgrass Spartina pectinata was shorter in transplanted sods than in pristine or source prairies.
  • Diameter/perimeter/area (2 studies): Two studies (one replicated) in wet prairies in the USA found that the average area of small transplanted sods (≤0.28 m2 initial size) increased over 3–4 growing seasons. One of the studies transplanted larger sods (0.65 m2 initial size) and reported that their average area decreased over 3–4 growing seasons.

OTHER

  • Survival (2 studies): Two studies (one replicated) in wet prairies in the USA reported ≥90% survival of transplanted sods of wet prairie vegetation after 3–4 growing seasons.

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 before-and-after study in 1980–1986 of a patch of freshwater marsh vegetation in England, UK (Worthington & Helliwell 1987) reported that transplanting vegetation from one site to another (then grazing, cutting and pulling up weeds) had little long-term effect on plant species richness. Unless specified, statistical significance was not assessed. The vegetation contained 54 species before transplanting and 49 species six years after. Thirty-six species were present both before and after transplanting. Small-scale richness was significantly higher one year after transplanting (16 species/m2) than before (11 species/m2), but returned to approximately 11 species/m2 after six years. The most frequently recorded species before intervention were clustered dock Rumex conglomeratus (in 100% of quadrats), creeping buttercup Ranunculus repens (92%) and yellow iris Iris pseudacorus (75%). The most frequently recorded species after intervention were tufted grass Holcus lanatus (92%) and yellow iris (83%). Methods: In late 1980, around 1.5 ha of marsh vegetation (along with 2.8 ha of other vegetation) was transplanted from one site earmarked for gravel mining. The new site, 400 m away, was excavated to suitable elevations, then 6-m2 blocks of vegetation and soil were transplanted. Post-transplant management involved annual grazing, pulling up docks Rumex spp. and intermittent cutting. Pumps maintained a high water table. The marsh vegetation was surveyed in twelve 1-m2 quadrats before (October 1980) and after (October 1981 and 1986) intervention.

    Study and other actions tested
  2. A replicated, paired, controlled study in 1992–1993 in five freshwater marshes undergoing restoration in New York State, USA (Brown & Bedford 1997) found that plots of transplanted marsh vegetation contained a more wetland-characteristic plant community, with more and greater cover of wetland species, than plots without transplants for up to two growing seasons. After one growing season, transplanted plots contained a plant community more characteristic of wetland conditions than plots without transplants (data reported as a wetland indicator index). The transplanted plots also contained more and greater cover of wetland plant species (3.7 species/plot; 50% cover) than plots without transplants (2.0 species/plot; 19% cover). After two growing seasons, the transplanted plots still had greater cover of wetland plants (99%) than plots without transplants (54%), but the other metrics did not significantly differ between treatments (e.g. 5.1 vs 2.8 wetland plant species/plot). Methods: In May 1992, thirty 0.25-m2 plots were established across five recently rewetted sites (drained for ≥40 years previously). In 15 plots (three plots/site), 15 cm of topsoil was removed and replaced with sods of soil and vegetation from nearby remnant marshes. The other 15 plots (three plots/site) were left undisturbed. Plant species and cover were recorded in autumn 1992 and 1993.

    Study and other actions tested
  3. A study in 1994–1997 in a floodplain wet prairie in Kansas, USA (Fraser & Kindscher 2001) reported >90% survival of transplanted wetland vegetation sods after four growing seasons, and found that the area of surviving sods increased. After four growing seasons, 97 of 107 transplanted sods were still alive. Two sods were confirmed as dead. The other eight sods were not relocated. Surviving sods dominated by prairie cordgrass Spartina pectinata covered 1.6 m2 on average and surviving sods dominated by spikerush Eleocharis macrostachya covered 26 m2 on average. All sods were 0.28 m2 when transplanted. For both species, the final area of sods was affected by elevation/moisture levels (see original paper). Methods: In spring 1994, sods of perennial wet prairie vegetation were cut from a wet prairie using a mechanical tree spade. The sods were placed in a newly created wet prairie site, with similar soils to the donor site, within one hour. Survival of all sods, and the area of 27 cordgrass-dominated and 18 spikerush-dominated sods, were monitored each October between 1994 and 1997.

    Study and other actions tested
  4. A replicated, site comparison study in 1999–2001 in a floodplain wet prairie in Kansas, USA (Fraser & Kindscher 2005) reported 90% survival of transplanted prairie cordgrass Spartina pectinata sods over three growing seasons, found that smaller sods increased in size and area, and found that transplanted cordgrass was shorter and less dense than in reference prairies. Sixty plots were planted with 1–20 cordgrass sods, with a total area of about 0.65 m2/plot. After three growing seasons, 90% of all transplanted cordgrass sods contained at least one living stem (range 73–100% for different initial sod sizes and planting elevations). The total area of prairie cordgrass had increased in plots planted with small sods (to 3.6 m2/plot) or medium sods (to 1.0 m2/plot) but had decreased in plots planted with one large sod (to 0.4 m2/plot). This reflected changes in the average size of individual sods (see original paper for data). After three growing seasons, prairie cordgrass was shorter and less dense in planted sods (127 cm tall; 91 stems/m2) than in pristine or source prairies (184–192 cm tall; 257–303 stems/m2). Methods: In June 1999, five-hundred cordgrass sods were transplanted from roadside areas to a recently restored wet prairie (historically farmed, sown with mixed prairie seeds in April 1999). Twenty 400-m2 plots were planted with each sod number/size combination (twenty 0.03-m2 sods; four 0.17-m2 sods; or one 0.65-m2 sod). Plots had varying elevations (moisture levels). Sods were monitored in September 1999, 2000 and 2001. Cordgrass height and density were also surveyed in nearby pristine wet prairies and source roadside prairies.

    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.

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Marsh and Swamp Conservation

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Marsh and Swamp Conservation
Marsh and Swamp Conservation

Marsh and Swamp Conservation - Published 2021

Marsh and Swamp Synopsis

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