Introduce fragments of trees/shrubs: freshwater wetlands
Overall effectiveness category Unknown effectiveness (limited evidence)
Number of studies: 1
Background information and definitions
This action involves introducing fragments of trees/shrubs to restore/create swamps. For trees/shrubs, fragments will most likely be unrooted cuttings. Vegetation fragments may be planted directly into the soil, or spread on the soil surface. Fragments may be obtained from plants raised in greenhouses/laboratories, or collected from natural sites (with potential damage to donor site; Laegdsgaard 2002).
Introduction of target vegetation might be useful in severely degraded or bare sites – which may lack remnant plants or seed banks to kick start revegetation with desirable species, and may be at risk of being taken over by undesirable species (Brown & Bedford 1997). It might also be useful in isolated wetlands, far from sources of marsh or swamp plant propagules. However, note that up-front costs can be high.
The effects of planting may be highly dependent on the environmental conditions in each study. Questions you might ask when interpreting the evidence include: Is the study site degraded? Where and when were fragments introduced? Was there any intervention to improve conditions before planting? What were the environmental conditions over the duration of the study?
The scope of this action does not include planting nurse plants; planting submerged or floating plants; planting to restore bogs, fens, fen meadows or peat swamp forests (see Taylor et al. 2018); or planting facultative wetland plants in upland sites. In contrast, the scope does include planting non-native species to conserve marshes or swamps – whilst acknowledging that this is often considered ethically unacceptable due to the risk of invasion (e.g. Ren et al. 2009).
Related actions: Directly plant whole plants; Introduce seeds or propagules; Transplant or replace wetland soil; Restore/create marshes or swamps using multiple interventions, often including planting.
Brown S.C. & Bedford B.L. (1997) Restoration of wetland vegetation with transplanted wetland soil: an experimental study. Wetlands, 17, 424–437.
Laegdsgaard P. (2002) Recovery of small denuded patches of the dominant NSW coastal saltmarsh species (Sporobolus virginicus and Sarcocornia quinqueflora) and implications for restoration using donor sites. Ecological Management & Restoration, 3, 202–206.
Ren H., Lu H., Shen W., Huang C., Guo Q., Li Z. & Jian S. (2009) Sonneratia apetala Buch.Ham in the mangrove ecosystems of China: an invasive species or restoration species? Ecological Engineering, 35, 1243–1248.
Taylor N.G., Grillas P. & Sutherland W.J. (2018) Peatland Conservation: Global Evidence for the Effects of Interventions to Conserve Peatland Vegetation. Synopses of Conservation Evidence Series. University of Cambridge, Cambridge.
Supporting evidence from individual studies
A study in 2007–2009 in a floodplain swamp restoration site in Wisconsin, USA (Thomsen et al. 2012) reported 12% survival of planted tree cuttings over two years. All surviving individuals were willows Salix spp. No cottonwood Populus deltoides or red osier dogwood Cornus stolonifera cuttings survived at monitored points – although some surviving cottonwood cuttings were noted elsewhere in the site (not quantified). Methods: Fresh (<2-week-old), unrooted tree cuttings were planted into 16 plots in a floodplain swamp restoration site (a clearing created by a storm). Cottonwood cuttings were planted in May 2007. Black willow Salix nigra, sandbar willow Salix exigua and dogwood cuttings were planted in April 2008. All plots had been cleared of invasive reed canarygrass Phalaris arundinacea and disked in November 2006. Herbicide was then applied regularly through to November 2008). Survival was monitored for 28 cuttings situated at survey points.Study and other actions tested