Add below-ground organic matter before/after planting trees/shrubs: brackish/saline wetlands

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

Study locations

Key messages

  • One study evaluated the effects, on vegetation, of adding below-ground organic matter to brackish/saline wetlands planted with trees/shrubs. The study was in Brazil.








  • Survival (1 study): One replicated, randomized, controlled study in a coastal swamp in Brazil reported that adding manure to plots planted with tree seedlings had mixed effects on their survival over three years, depending on the species of tree and dose of manure.
  • Growth (1 study): The same study reported that adding manure to plots planted with tree seedlings had mixed effects on their growth over three years, depending on the species of tree and dose of manure.

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, controlled study in 2002–2005 in a degraded coastal swamp in southeast Brazil (Zamith & Scarano 2010) reported that adding manure had mixed effects on survival and growth of planted tree seedlings over three years, depending on species, dose and metric. Manure increased survival for one of five planted species (manure: 77–83%; no manure: 67%) but reduced survival for two species (manure: 57–83%; no manure: 77–93%). For the other two species, manure either increased or reduced survival depending on the dose. Statistical significance of these survival results was not assessed. Manure had no significant effect on seedling growth in 20 of 30 comparisons. It did increase diameter growth in 4 of 10 comparisons, height growth in 4 of 10 comparisons, and canopy area growth in 2 of 10 comparisons (see original paper for data). However, manure did not consistently increase growth, across all metrics and doses, for any species. Methods: In May 2002, ninety seedlings of each of five tree species were planted, 1.5 m apart, into a degraded coastal swamp. Thirty seedlings/species received each manure treatment: 30 L/seedling, 15 L/seedling or none. The study does not report further details of the manure or application. Invasive trees and grasses were removed from the swamp before planting. The survival of each seedling was monitored until May 2005. The diameter, height and canopy area of each seedling were measured in August 2002 and August 2005.

    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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