The lemming – a key herbivore in our alpine ecosystems?
Lauri Oksanen (project leader)
Summary of results with list of publications from Ecology and Environmental Science, Umeå University.
Email: lauri.oksanen@abo.fi
The objective of this project was to study the dynamics of lemmings and their impact on vegetation, from productive slopes with birch forests and willow scrubland to barren alpine plateaux with heathland, snow beds and wetlands with sedge and cottongrass. The hypothesis was that lemmings are controlled by predators in the productive areas, while on the alpine plateau there is intensive interaction between lemmings and vegetation. Lemmings should therefore contribute to the biodiversity of the alpine plateau where they "prepare the ground" and prevent the strongest competitors from displacing the species that are less competitive. On the productive slopes this mechanism should not work because of the controlling effect of predators.
The principal results are that the number of coexisting plant species greatly increases from the birch forests to the alpine areas. At the same time, the intensity of competition among plant species decreases. The pattern appears to have a lot to do with grazing. Reindeer and voles are able to control the total plant biomass, and predators can prevent this influence by regulating the herbivores. In the most productive mountain environments we thus have a typical "trophic cascade" where a strong influence of predators prevents the realisation of a potentially strong herbivore-plant interaction. In the more barren environments this control is relaxed, and the potential of herbivores to control vegetation is realised. The defence of plants does not appear to play any major role. All that is available in the winter is eaten or severely damaged when the herbivores clear the way. It is primarily grass and sedge which are favoured by the advance of the food limited herbivores, but concentrating on heavily defended wintergreen shoots appears to be a poor strategy.
Multivariate characterisation of the reindeer breeding area
Börje Danell (project leader)
Summary of results with list of publications from Animal Breeding and Genetics, SLU.
Email: orje.danell@hgen.slu.se
Hard stuggle for food
The Swedish reindeer breeding area accounts for 50% of the land area of Sweden and is divided into 51 Sami villages. The area is heterogeneous with regard to natural and anthropogenic conditions. Productivity varies as a result of an interplay among many environmental factors and various adaptations associated with management.
The project identifies factors which influence the conditions for reindeer breeding, gives proposals for zonal division of the reindeer breeding area and suggests grouping of Sami villages based on similarities and dissimilarities. Characterisation and grouping make it easier to identify strengths and weaknesses in the conditions of the Sami villages, and enable relevant comparisons to be made between villages with identical conditions.
The effect of reindeer grazing on the biodiversity of alpine plant communities
Johan Olofsson (project leader)
Summary of results with list of publications from Umeå University.
Email: johan.olofsson@emg.umu.se
Reindeer grazing, together with tourism, is the most extensive form of land use in the Swedish mountain areas. The Swedish Riksdag has resolved that all land use in the mountains should consider biodiversity is such a way that sustainable development is promoted. In order to achieve these goals, we must understand how reindeer grazing affects nature, but this knowledge is greatly limited.
The effect of grazing on species richness has been studied intensively in grasslands in the temperate climate zone, primarily in meadows and semi-natural pastures. These studies have shown that grazing almost always increases the species richness of plants. There are however studies which show that grazing less often has a positive effect on species richness in low productive systems. The objective of this project has therefore been to test whether the theories developed are also valid for reindeer grazing in the mountain areas and to investigate how the effect of reindeer grazing on species richness varies depending on the temporal or spatial scale at which the study is conducted.
The results show that the effect of grazing differs between mountain ecosystems and more productive ecosystems. Because of the reduced competition among plants, reindeer grazing is of less significance for species richness. The facts that grazing has a positive effect on uncommon species and that trampling by reindeer may prevent moss cover becoming contiguous and hindering seed establishment, indicate that reindeer grazing can nevertheless be significant in preserving a high species richness at larger scales and over longer periods.
Responsible for this page: Kerstin Franklin