Biodiversity and vegetation dynamics in the coastal heathlands of western Norway

The heaths of Lygra, western Norway, were investigated, and 19 communities at the association level were distinguished. Distinct ecotypes of Ranunculus acris and Poa humilis and microspecies of Euphrasia were restricted to the grass heaths. No distinct ecotypes were found in the Calluna-dominated vegetation. It is suggested that the regular burning, which has been part of the management of the area, has activated the seed bank of the ericaceous heath, and thus maintained genetic diversity and slowed down ecotype differentiation. The grass heaths, with no combustible material, have been unaffected in this way. Permanent plots in the two dominant heath types, dry heath (Vaccinio-Callunetum) and wet heath (Ericetum tetralicis) were followed over six years and the data analysed using a modification of Jaccard's index, allowing for species abundances.