Milieu en vegetatie van Carex hartmanii Caj. op Terschelling, in het kader van een oecologische vergelijking tussen deze soort en Carex buxbaumii Wahlenb

Carex hartmanii Caj., a sedge new for the Netherlands and closely allied to C. buxbaumii Wahlenb., is ecologically compared to the latter. Whereas the habitat of C. buxbaumii presents a geographical gradient from a Central European eutrophic environment of swamps and wet meadows (Magnocaricion and Cnidio-Juncetum juncetosum subnodulosi) up to, in Sweden, a nearly ombrotrophic vegetation of a raised bog, Carex hartmanii does not show such a gradient. It is known from a slightly more dry and acid habitat (compared to C. buxbaumii) in Central Europe (Cnidio-Juncetum juncetosum acutiflori) up to damp rivulet meadows rich in nutrients in S.-Sweden (Calthion). Both species are, however, contrasting in such a way, that in Central Europe C. hartmanii is more acidophilus than C. buxbaumü, whereas in S.-Sweden the former seems to be more basiphilous than the latter. The Dutch habitat on the island of Terschelling has been analysed. Carex hartmanii is differential here for the Ophioglosso-Calamagrostietum epigeios, a community of older secondary dune valleys slightly overblown with sand, and with strongly fluctuating water level, submersed in winter, running dry in summer. This habitat appears to be richer in nutrients than the environment of C. buxbaumii in the Netherlands. Consequently the ecological position of both species in the Netherlands is more related to that in Sweden than to that in Central Europe, and corresponds with the boreal character of the Dutch Wadden-district