Reindeer in the archipelago of Holmöarna : Abundance of habitats and how reindeer have utilized them during winter 2015-16 and summer 2016

Sammanfattning: In the winter 2015/2016, about 700 reindeer were winter grazing on the islands of Holmöarna. Since the islands had not been used for reindeer grazing for more than 100 years, this is a unique opportunity to study how reindeer influence the vegetation that has developed in the absence of reindeer. Moreover, it also means that all reindeer faeces depositions and grazing damages originate from the last year. Most of the reindeer grazing occurred on Ängesön and Grossgrunden, at least during winter, due to lichen rich habitats. To investigate which habitats were available for reindeer, the abundance of these habitats and which resources they provide, 239 randomly selected study sites were investigated. To find out reindeer utilization of resources and impact on vegetation, all faecal droppings from reindeer were counted. Also, lichen height, lichen cover, lichen volume, grazing damages of lichens and vegetation, trampling, and digging, were recorded at every study site. Old-grown spruce forest was the most abundant habitat, providing reindeer with ground lichens, bilberries and epiphytic lichens. Pine forest, rich in ground lichens, was the most preferred and used habitat based on lichen cover and lichen volume, lichen damage and trampling. NMSD ordination confirmed a strong relationship between lichen height and lichen cover, i.e. lichens were heavily grazed in every habitat where lichens were recorded. Reindeer depositions of dungs and pellets were found in all habitats, but were most abundant in spruce forest with ground lichens. Strong relationships between lichen damages, digging signs and reindeer pellets confirmed more activities where lichens were abundant. Grazing of bilberry shoots and trampling, both indications of summer activities by reindeer, were also closely associated, indicating that bilberry shoots was an important food resource in summer on these islands. In the light of my result, the islands of Holmöarna have good provision for reindeer, in winter by richness of ground lichens in pine forest and old spruce forest, and summer primarily by bilberries in old grown spruce forest, mixed forest and pine forest with Vaccinium ssp. Although almost all suitable habitats show signs of reindeer activities after only one year, there is still abundant winter and summer food resources available for future grazing. There is thus plenty of resources available for reindeer on the islands of Holmöarna and reindeer are able to utilize them. If they are suitable to use for reindeer grazing in the future is thus more dependent on logistic problems like difficulties in transporting the reindeer from mainland to the islands.