Create mounds or hollows before planting non-woody plants: brackish/saline wetlands

How is the evidence assessed?
  • Effectiveness
  • Certainty
  • Harms

Study locations

Key messages

  • One study evaluated the effects, on vegetation, of creating mounds or hollows in brackish/saline wetlands before planting emergent, non-woody plants. The study was in the USA.




  • Individual species abundance (1 study): One replicated, randomized, paired, controlled study in an estuarine salt marsh in the USA found that amongst plots sown/planted with dwarf saltwort Salicornia bigelovii, those that had been excavated into depressions had lower cover of dominant pickleweed Salicornia virginica – over the first growing season – than plots left at ground level.




  • Germination/emergence (1 study): One replicated, randomized, paired, controlled study in an estuarine salt marsh in the USA found that there were no more (sometimes fewer) dwarf saltwort Salicornia bigelovii seedlings in excavated depressions than in level plots, two months after sowing saltwort seeds.
  • Survival (1 study): The same study found that the survival rate of dwarf saltwort Salicornia bigelovii transplants was not greater (sometimes lower) in excavated depressions than in level plots.

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, paired, controlled study in 2006 in an estuarine salt marsh in California, USA (Varty & Zedler 2008) found that excavating depressions before sowing/planting dwarf saltwort Salicornia bigelovii did not increase saltwort seedling density or transplant survival, but did reduce density of the initially dominant succulent. Two months after sowing/planting, there were fewer dwarf saltwort seedlings in 10-cm depressions (3 seedlings/0.25 m2) than on level plots (10–14 seedlings/0.25 m2), with no significant difference between 5-cm depressions (9 seedlings/0.25 m2) and level plots. The same was true for survival of dwarf saltwort transplants after six months (10-cm depressions: <40%; 5-cm depressions: 70%; level plots: 70%). However, depressions had lower cover of pickleweed Salicornia virginica in 12 of 12 comparisons over the whole growing season (10-cm depressions: 41–59%; 5-cm depressions: 49–65%; level plots: 58–78%). Methods: In March 2006, dwarf saltwort was planted and sown into seventy-two 0.25-m2 plots (three sets of 24) on a pickleweed-dominated salt marsh. Four seedlings and 1.25 ml of seed were added to each plot. Thirty-six plots (12 random plots/set) had been lowered by 5 cm or 10 cm before planting, by removing subsurface sediment. The other plots remained at ground level. Some pickleweed was cut and removed from half of the plots. Vegetation was surveyed between May and September 2006.

    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?

List of journals searched by synopsis

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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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