Nitrogen limitation in the coastal heath at Anholt,Denmark

The purpose of the study was to investigate, whether the coastal grey dune vegetation at Anholt, Denmark, is limited by nitrogen or phosphorus. The island Anholt (22,37 km²) is situated in the centre of Kattegat A two factor fertilization experiment with nitrogen as NH₄NO₃ (N-addition) and phosphorus as KH₂PO₄ (P-addition) was carried out in the coastal grey dune vegetation of Anholt. The N-addition corresponded to 40 kg N ha^?1 year^?1 and the P-addition to 7 kg P ha^?1 year^?1 The experiment included N-, P-, N + P-addition and control. Lichens (genera: mainly Cladonia, Stereocaulon, Cetraria, Hypogymnia) and bryophytes (genera: Polytrichum, Racomitrium) cover most of the surface. Only two plant species, Corynephorus canescens and Empetrum nigrum, constitute nearly all vascular plant cover and biomass of this calcium poor coastal heath community. Corynephorus and Empetrum increased their cover significantly following N and N + P addition. No effect was observed by P addition alone. N limitation of this coastal heath vegetation remote from agricultural and industrial activities was evident. The effect on the plant species of the single application was short-lived. After two-three years of enhanced cover, the Corynephorus and Empetrum cover had returned to their level before the experiment. The lichen vegetation, however, changed more permanently, and after 12 years the subplots with N + P addition was dominated by rich growth of Cladina and Cetraria species. The results are discussed in relation to anthropogenic nitrogen deposition and conservation of this high priority ecosystem.