Transplant wetland soil before/after planting non-woody plants: freshwater wetlands
Overall effectiveness category Unknown effectiveness (limited evidence)
Number of studies: 2
Background information and definitions
Loose soil can be transplanted from a healthy marsh or swamp to a one that is being created or restored. Soil could simply be added to a recipient site, or be used to replace material in the recipient site. Soil transplants can be useful to introduce a chemically and physically suitable substrate for growth of wetland vegetation, and a mixture of soil organisms such as bacteria, fungi and invertebrates (Anderson & Cowell 2004). Thus, soil transplants might be used to aid the initial survival and growth of introduced marsh or swamp plants. Soil transplants usually also contain a mixture of wetland plant seeds, roots, tubers or rhizomes, which could supplement the focal introduced vegetation to create a diverse, wetland-characteristic plant community.
Caution: This action inevitably causes damage to any donor site. Also, transplanted soil could contain invasive plants, animals or microorganisms. A possible solution to these problems is to use soil from healthy marshes or swamps that are earmarked for destruction. Using local donor sites could minimize the spread of invasive species, and make use of communities adapted to local conditions.
Other published names for this action include “salvaged marsh surface replacement”, transplanting “seed banks” and “mulching”. We restrict the latter term to the addition of organic matter that is largely free of plant propagules, e.g. domestic compost or seaweed, to the ground surface.
Anderson C.J. & Cowell B.C. (2004) Mulching effects on the seasonally flooded zone of west-central Florida, USA wetlands. Wetlands, 24, 811–819.
Brown S.C. & Bedford B.L. (1997) Restoration of wetland vegetation with transplanted wetland soil: an experimental study. Wetlands, 17, 424–437.
Supporting evidence from individual studies
A replicated, site comparison study in 1999–2000 of the ephemeral marsh zone in 33 created freshwater wetlands in Florida, USA (Anderson & Cowell 2004) found that adding marsh soil before planting marsh vegetation created a plant community characteristic of wetter conditions and had season-specific effects on plant species richness and diversity, but had no significant effect on overall vegetation abundance. Whilst amended and unamended marshes both developed a wetland-characteristic plant community, the community in amended marshes was characteristic of significantly wetter conditions (data reported as a wetland indicator index). Amended marshes had 44–75% cover of wetland-characteristic plants (vs unamended marshes: 32–58%; statistical significance not assessed). In the wet season, plant species richness and diversity were similar or lower in amended marshes than unamended marshes (amended: 9; unamended: 11 species/m2; and diversity reported as an index). In the dry season, these metrics were similar or higher in amended marshes than unamended marshes (amended: 8; unamended: 7 species/m2; diversity reported as an index). Both treatments had statistically similar overall vegetation cover (amended: 54–83%; unamended: 49–76%) and above-ground biomass (amended: 87; unamended: 80 g/m2). Cover of plant groups (e.g. grasses/reeds, mosses, and tree/shrub seedlings) was generally similar in amended and unamended marshes (see original paper for data). Methods: Vegetation was surveyed in the marshy, seasonally flooded zone of 33 excavated wetlands (≥5 years old). All but one wetland had been planted with marsh vegetation (details not reported). Marsh soil had been spread on the surface of 17 of the sites, in a layer 15–30 cm thick. In November 1999 (wet season) and June 2000 (dry season), plant species and cover were recorded in three 1-m2 quadrats/marsh. In August 2000, vegetation was cut from three 0.25-m2 quadrats/marsh, then dried and weighed.Study and other actions tested
A replicated, randomized, paired, controlled study in 2010–2011 in six experimental wetland trenches in Alberta, Canada (Roy et al. 2014) found that adding peat-rich soil to mine tailings did not reduce survival of planted water sedge Carex aquatilis over two growing seasons, and typically increased the biomass of surviving sedges. In two of four comparisons, pots of mine tailings mixed with peat-rich soil supported higher sedge survival (50–67%) than pots of raw mine tailings (24–44%). There was no significant difference between treatments in the other two comparisons (added peat: 74%; raw tailings: 54–69%). In three of four comparisons, the above-ground biomass of surviving sedges was higher in pots of mine tailings mixed with peat-rich soil (2.1–2.8 g/trench) than in pots of raw mine tailings (1.1–1.5 g/trench). There was no significant difference between treatments in the other comparisons (added peat: 2.2 g/trench; raw tailings: 2.2 g/trench). Methods: In June 2010, water sedges were collected from a natural marsh and randomly planted into 192 one-gallon pots (number of plants/pot not clearly reported). Half of the pots contained mine tailings mixed with peat-rich soil (1:2 parts). Half of the pots contained pure mine tailings (dense sediments, low in organic matter, rich in salts and metals). The pots were placed into six experimental wetland trenches: 16 peaty pots and 16 raw tailings pots/trench. Surviving plants were harvested at the end of the 2011 growing season. Biomass was dried before weighing.Study and other actions tested