Abstract

The relative importance of positive and negative interactions among plant species in communities undergoing succession has been subject to a frequent discussion. We present data on interspecific associations among the first plants establishing on two primary successional glacier forefronts, one in North Cascade Range in North America and another in Kiölen mountains in northern Norway. Both glacier forefronts are devoid of plants with nitrogen fixing nodules. We observed mainly negative interspecific associations, although some positive associations also occurred. We conclude that the successional change at these two primary successional sites is mainly driven by species-specific inhibitory and competitive interactions although facilitative interactions may also have some contribution to the community dynamics. Finally, we propose that the negative associations are mainly attributable to below ground competition and inhibition whereas the positive associations may be attributable to two potential causes: habitats amelioration of environmental stress by any neighboring plants with marginal niché overlap and shared mycorrhizal habit among species sharing similar habitat requirements.