Wetland Seedbanks





Restoration Decisions: (and theory)


reference sites

Case Studies


State of the Science

success criteria
floristic quality


Created by:

Abby Rokosch
Jessen Book
Siobhan Fennessy

Seed banks have the potential to contribute to the establishment of diverse vegetation communities in wetland restoration projects (see mini-case study). Examining wetland seed banks can determine what species are present in the wetland but are currently not growing (Galatowitsh and van der Valk, 1997). The usefulness of wetland seed banks to establish native vegetation depends on the condition and composition of the seed bank. The value of the seed bank for wetland restoration depends on the type and length of disturbance that the wetland was subjected to (Middleton, 1999). Long-term drainage of wetlands can deplete the seed bank of viable seeds (Weinhold and van der Valk, 1989; Brown, 1995; Galatowitsch and van der Valk, 1996 in Brown and Bedford, 1997). Short episodes of farming can deplete the seed bank of all its useful seeds (Middleton, 1999). The loss of viable seeds may slow down the recovery or establishment of vegetation following the restoration of wetland hydrology (Brown and Bedford, 1997).

Recently, transplanting remnant wetland seed banks has been studied to increase the probability of vegetation establishment (Brown and Bedford, 1997). Wetland restorationists have conflicting views about the effectiveness of using remnant wetland seed banks as methods to establish vegetation in restoration sites (Middleton,1999). Those who believe in the "self-design" approach of wetland restoration would argue that the time and effort spend on transplanting seed banks is a waste of time and that through the physical processes of nature will determine the establishment of wetland vegetation. Though they would advocate that wetland seed banks can contain rare species and have the potential to assist wetland recovery, knowledge of seed bank composition and the ways in which certain species germinate and disperse can be invaluable to wetland restoration projects (Middleton, 1999).

Wetland seed banks have been extensively studied in prairie potholes (Galatowitsch and van der Valk, 1996; Middleton, 1999. Weinhold and van der Valk (1989) found that farmed prairie potholes have the potential to retain approximately 60% of their wetland plant species for up to 20 years or more (Middleton, 1999). However, not all vascular plant species can return to drained and farmed prairie potholes after hydrology is established (Zedler, 2000)

Mini Case-study

In a paper by Galatowitsch and van der Valk (1996), the "efficient community hypothesis" was studied which refers to the idea that the vegetation of restored prairie pothole wetlands will develop rapidly after their hydrology has been restored. They tested the hypothesis that according to the efficient-community hypothesis, all plant species that can become established and survive under environmental conditions found at a site will eventually be found growing there and/or in its seed bank. If this hypothesis proved to be true, it would support the "self-design" theory that all restored wetlands will establish plant communities regardless of efforts to plant or seed. However, if the hypothesis proved to be false, then restoration recovery would be affected by location of propagule source and introduction of propagules by planting or seeding. These results would support the "design" theory of wetland restoration.


  • The vegetation of restored wetlands was not similar to that of the natural wetlands in many ways: the natural wetlands had more species than the restored wetlands, some guilds of species had significantly more species in the restored wetlands, the distribution of and abundance of most species at different elevations was different in natural and restored wetlands, and finally, the seed banks of restored wetlands contained fewer species and fewer seeds than the natural wetland.
  • Emergent species composition was similar in both natural and restored wetlands
  • Because they found some similarity between the natural and restored wetlands they concluded that dispersal of propagules to hydrologically restored basins is the primary mechanism responsible for the re-establishment of wetland vegetation. But because dispersal of species varies, the rate of re-vegetation will vary. This implies that re-vegetation of some plant species may take a very long to be established or may never established if the restored wetland is not somehow connected to the natural wetland.
  • There is no guarantee that all plant species will be reestablished through dispersal only. It would be beneficial to the restored wetland if planting methods were implemented to increase the wetlands capacity to re-vegetate with their natural plant communities.