Add surface mulch before/after planting non-woody plants: brackish/saline wetlands

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

Source countries

Key messages

  • One study evaluated the effects, on vegetation, of mulching brackish/saline wetlands planted with emergent, non-woody plants. The study was in Canada.

VEGETATION COMMUNITY

 

VEGETATION ABUNDANCE

  • Overall abundance (1 study): One replicated, randomized, paired, controlled study in intertidal brackish marshes in Canada found that adding surface mulch after planting wetland herbs typically had no significant effect on total live vegetation biomass, two growing seasons later.
  • Individual species abundance (1 study): The same study found that adding surface mulch increased the cover of one of two planted herb species (creeping alkaligrass Puccinellia phryganodes) but had no significant effect on cover of the other species (estuary sedge Carex subspathacea). Cover was monitored over the second growing season after planting/mulching.

VEGETATION STRUCTURE

 

OTHER

  • Survival (1 study): One replicated, randomized, paired, controlled study in intertidal brackish marshes in Canada found that adding surface mulch had no significant effect on the survival of two of two planted herb species, after two 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 replicated, randomized, paired, controlled study in 1996–1997 in two degraded, intertidal, brackish marshes in Manitoba, Canada (Handa & Jeffries 2000) found that adding surface mulch increased the cover of one of two planted herb species, but did not significantly affect survival rates of either species or overall above-ground biomass. On all five survey dates across the second growing season after planting, creeping alkaligrass Puccinellia phryganodes cover was higher in mulched plots (1,820–5,400 mm2/m2) than unmulched plots (1,090–3,810 mm2/m2). However, cover of estuary sedge Carex subspathacea never significantly differed between treatments (mulched: 670–2,880 mm2/m2; unmulched: 720–2,600 mm2/m2). On all five dates, survival rates were statistically similar under each treatment for both alkaligrass (mulched: 87–100%; unmulched: 52–93%) and estuary sedge (mulched: 28–58%; unmulched: 23–50%). On at least two of three dates (results not clearly reported), live above-ground biomass was statistically similar under each treatment for both alkaligrass-dominated vegetation (mulched: 45–178 g/m2; unmulched: 29–122 g/m2) and sedge-dominated vegetation (mulched: 1–4 g/m2; unmulched: 1–4 g/m2). Methods: In June 1996, plugs of creeping alkaligrass and estuary sedge were transplanted from natural stands to 1-m2 plots within brackish marsh vegetation damaged by geese (one species/marsh; 12 plots/species; 42 plugs/plot). Two random quarters of each plot were mulched after planting (5 mm layer of peat from a nearby marsh). Half of each plot was also fertilized. All plots were fenced to exclude geese. Vegetation was surveyed in summer 1997. Survival and cover were monitored for planted plants in the centre of each plot. Vegetation samples were cut from the margins of each plot, then washed to remove dead biomass, dried and weighed.

    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?

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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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