Restoration Potential of Soil Seed Banks for Coastal Heathlands and Calcareous Meadows in Western Norway

Abstract

Over the last centuries, traditional farming practices have created species-rich, semi-natural ecosystems that depend on human use to maintain the characteristic open vegetation. Recent land use changes, including abandonment and afforestation, decreased the extent and ecological condition of semi-natural ecosystems in Norway. Restoration efforts are now needed to counteract the loss of semi-natural ecosystems and their associated values. This thesis investigated whether the soil seed bank (SSB) of two semi-natural ecosystems in western Norway – coastal heathland and calcareous meadow – can support the restoration process after the deforestation of spruce plantations. One study area covered the two islands dominated by coastal heathland, Vågsøy and Silda, where soil samples were taken from intact coastal heathland sites, restoration sites, and Sitka spruce plantations. The other study area was a calcareous meadow located in Voss municipality, where soil samples were taken from an intact meadow and a restoration site that was a deforested Norwegian spruce plantation. Germination trials were conducted to compare seed density and species composition of the SSBs of the site types. The results showed a significantly higher seed density for the intact sites in both ecosystems and a significant difference in species composition between the site types, with more “target” species found in the intact sites. However, the results indicate differences in the restoration potential of the SSB of the two ecosystems. Seeds of target species germinated in the soil of about 50-year-old Sitka spruce plantations in the coastal heathland ecosystem, indicating that the SSB has the potential to support the restoration process. Future measures should include burning the restoration sites to enhance germination and grazing to increase seed input from intact sites. The results from the calcareous meadow ecosystem are rather ordinary and agree with other studies that spatial dispersal of seeds might be more relevant than the SSB for ecological restoration of meadows. Active input of seeds might be necessary, especially to prevent problem species from establishing in the restoration site.