Honningblom Herminium monorchis – overvåking av artens tre populasjoner på Hvaler

Abstract

The musk orchid Herminium monorchis (L.) R.Br. is one of Norway’s rarest vascular plants, listed as Critically Endangered in the Red-list for species. Since 2011 the species has also been listed as a Priority Species under the Norwegian Nature Diversity Act. Its distribution in Norway is restricted to three populations at Asmaløy, Hvaler municipality, Østfold county. In 2014 we established 80 permanent plots to monitor the populations, and to increase our understanding of important population processes. The three localities differed widely, one being a rich fen, one a salt meadow and the third a dry, short-statured meadow. Flowering was strongly correlated with plant size, and plant size varied among the three localities. The population size varied between 2014 and 2015, but not synchronously among the localities, due to a certain proportion of the population being dormant (i.e. without aboveground biomass) each year. A long-term monitoring of individual ramets will provide a better understanding of the key processes affecting population viability, so that management actions can be better targeted.