FATE OF ADDED NITROGEN IN A MOSS SEDGE ARCTIC COMMUNITY AND EFFECTS OF INCREASED NITROGEN DEPOSITION

Although nitrogen deposition has not increased as drastically in the Arctic as in the highly industrialized countries, this area has not been left unaffected. Several studies indicate at least twofold increases in the N-deposition in the Arctic during the last 100 years. Arctic plants are generally adapted to low availability of nutrients; thus arctic plant communities may be sensitive even to small changes in the nutrient input. Based on two field studies in Iceland, this paper discusses the effects of increased nitrogen deposition on a simple two-species plant community, Racomitrium lanuginosum moss-heath with Carer bigelowii. The paper also discusses the implications for community structure based on the interactions between the two major growth forms, the moss and the clonal graminoid, that are adapted to take up nitrogen from different sources.