On the Interaction between Rodents and Alpine Plant Communities
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- Institutt for biologi 
Rodents with cyclic population dynamics are important herbivores in alpine areas with major effects on vegetation composition, biomass and diversity. Many places in Fennoscandia the population cycles in lemmings and voles have been fading out during the last two decades. Together with the recent climate change this has the potential to cause serious changes in alpine plant communities. This study has investigated the distribution of rodents in response to preferred and non-preferred plant species and their effect on seedling emergence in two Norwegian alpine regions with contrasting rodent dynamics over the last decades; Børgefjell with intact 3-4 year population cycles and Dovrefjell where the cycles have been absent in recent years. Field work was conducted in the summer of 2011, a peak year for rodents in both mountain regions. Recordings of vegetation, rodent tracks and number of seedlings were done in 270 square (0.5×0.5 m) plots in lee sides and snow beds in the low alpine zone. The results indicate that lemming and voles avoid patches with high frequencies of non-preferred forage. In both regions seedling emergence was significantly positively correlated with disturbance from rodents, with the increase in number of seedlings being higher in Dovrefjell compared to Børgefjell. This suggests that microsite limitation is common in both regions. Generally fewer seedlings were found in Børgefjell than Dovrefjell, and as expected, the number of seedlings was higher in snow beds compared to lee sides in both regions. These results indicate that rodents have an important role for the presence of recruitment dynamics in lee side and snow bed communities in alpine areas.