Disturb soil/sediment surface: brackish/salt marshes

Overall effectiveness category Unknown effectiveness (limited evidence)
Number of studies: 1
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How is the evidence assessed?

Effectiveness

34%
Certainty

29%
Harms

0%

Calculating overall effectiveness category

Background information and definitions

This action involves shallow disturbance of the top few centimetres of soil/sediment in degraded marshes (e.g. by tilling, ploughing, disking or scarifying) without permanently removing any material. Such disturbance may encourage the growth of desirable plants. It can break up any hard soil crust, or create bare patches clear of competing vegetation or litter in which new plants can grow. Marsh plants may colonize from nearby habitat patches, or germinate from propagules (e.g. seeds, spores or root/rhizome fragments) already in the soil. The first colonizing plants will typically be fast-growing, weedy species – but these may also be desirable members of target plant communities, or act as nurse plants for later desirable communities.

Related actions: Physically damage problematic plants, including by disturbing the soil/sediment; Remove surface soil/sediment; Bury surface soil/sediment, including by deep ploughing.

Study locations

Key messages

One study evaluated the effects, on vegetation, of disturbing the surface of brackish/salt marshes. The study was in the USA.

VEGETATION COMMUNITY

Community composition (1 study): One replicated, paired, site comparison study of brackish/salt marshes in the USA reported that marshes disked every spring for at least six years (and drawn down during spring/autumn) shared only 24–34% of plant species with marshes that were not disked (or drawn down).
Overall richness/diversity (1 study): The same study found that overall plant species richness and diversity were similar in managed marshes (disked every spring and drawn down during spring/autumn, for at least six years) and unmanaged marshes (neither disked nor drawn down).

VEGETATION ABUNDANCE

VEGETATION STRUCTURE

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, site comparison study in 2007–2009 of eight brackish/salt marshes in Texas, USA (Fitzsimmons et al. 2012) found that managed marshes (disked every spring, along with a spring/autumn drawdown) and unmanaged marshes (subjected to neither of these interventions) had few plant species in common, but had similar overall plant species richness and diversity. Only 24–34% of plant species were found in both managed and unmanaged marshes (reported as a similarity index). However, both marsh types had statistically similar plant species richness (six of six comparisons; managed: 12–21 species/marsh; unmanaged: 8–18 species/marsh) and plant diversity (six of six comparisons; data reported as a diversity index). Methods: In autumn, winter and spring 2007/2008 and 2008/2009, vegetation was surveyed in four pairs of managed and unmanaged marshes (fifty-six 1-m² quadrats/marsh, placed along transects). In the managed marshes, the soil surface was disked every spring for 6–9 years. The managed marshes had also been impounded to control water levels and salinity (drawdown each spring-autumn). The study does not distinguish between the effects of three interventions. All marshes were grazed each summer and burned every three years. The marshes were brackish in 2007/2008 (managed: <2 ppt; unmanaged: <10 ppt) but saline in 2008/2009 following a hurricane and storm surge (e.g. average salinity in managed marshes: 20 ppt).
Study and other actions tested
Referenced paper
Fitzsimmons O.N., Ballard B.M., Merendino M.T., Baldassarre G.A. & Hartke K.M. (2012) Implications of coastal wetland management to nonbreeding waterbirds in Texas. Wetlands, 32, 1057-1066.

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

All the journals searched for all synopses

This Action forms part of the Action Synopsis:

Marsh and Swamp Conservation

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Add sediment: freshwater marshes Action Link	Unknown effectiveness (limited evidence)	1	Synopsis Link
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Add inorganic fertilizer: freshwater swamps Action Link	No evidence found (no assessment)	0	Synopsis Link