White willow sexual regeneration capacity under estuarine conditions in times of climate change

  • Tidal forested wetlands
  • Salinity and tidal flooding stress
  • Salix alba
  • Germination
  • Early establishment of willows
  • Tidal wetlands provide both habitats for coastal populations and wildlife, and ecosystem services for human welfare. Building with nature regarding cost-effective coastal protection is of increasing interest. Much research has been carried out on plant reproduction capacities in mangroves and salt marshes, but less is known on this issue in tidal freshwater wetlands. Willows are being successfully used for bank stabilization in riverine habitats, however, today white willow softwood forests in tidal wetlands are highly fragmented, and restoration is required e.g. by the European Habitats Directive. Recently, tolerance to increasing salinity and tidal flooding was found for vegetative propagules of floodplain willows. However, the establishment of autochthonous sexual recruits is necessary to conserve the genetic diversity of local populations, and thus may be preferable in restoration. The germination and early seedling establishment of Salix alba (white willow) was experimentally studied under simulated estuarine conditions. The species tolerance to increasing salinity (0, 0.5, 1, 1.5, and 2) was tested in a climate chamber, and its tolerance to flooding at different tidal treatments (control, spring tide, daily tide 15 min and 2 h flooding) in the greenhouse. Germination was neither affected by increasing salinity nor by tidal flooding. Salix seedlings established up to salinity 1.5, but cotyledon performance and radicle growth was largely reduced at salinity 2. Under tidal flooding, seedling growth was similar in all treatments. However, in the treatments with daily tides seedling anchorage in the substrate took more than two weeks, and fewer seedlings reached a suitable length to approach the high water line. We assess S. alba sexual regeneration under estuarine conditions as generally possible. Further studies are needed on the effects of sedimentation-erosion processes on willow establishment in the field, especially on feedbacks between Salix survival and tidal wetland evolution.
  • info:eu-repo/semantics/closedAccess
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