Osmunda regalis L. op Terschelling, oecologisch en vegetatiekundig bezien

In the Dutch “Wadden District”, a chain of islands, mainly constituted of dunes poor in lime, Osmunda regalis is only known from the island of Terschelling, which is the poorest in lime. There it is known since 1886 from a single locality along the bank of a ditch at the innermost dune border. The habitat and the vegetation of this locality have been analysed. They have slightly been influenced by adjacent wood plantations in 1951 and 1959—1960 ( Pinus nigra, Alnus glutinosa, Prunus serotina), which seem to have induced Osmunda to spread. The open habitat is more related to the corresponding atlantic Irish one than to the more sheltered and shady habitat in Southern atlantic and subatlantic Europe. Concerning nutrition level of the substrate, which is very poor, the habitat is however more comparable with that on the Dutch mainland than with both the Irish and the southern atlantic and subatlantic one.