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Forskningsartikel - Refereegranskat, 2007

Grey-sided voles increase the susceptibility of Northern willow, Salix glauca, to invertebrate herbivory

Olofsson J, Dahlgren J, Witzell J


The relationships between grey-sided vote (Clethrionomys rufocanus) densities, levels of invertebrate herbivory on Northern willow (Salix glauca) leaves, and chemical quality of the willows was studied on 8 islands and 2 mainland sites with contrasting vote densities in northernmost Norway. These variables were measured at each of the study sites to determine the degree and nature of the effects of browsing-induced alterations in plant quality on subsequent invertebrate herbivory. The level of invertebrate herbivory was positively correlated with vote density, as were the number of leaves per shoot, leaf size, and leaf nitrogen content, while leaf C/N ratios were negatively correlated with vote density. The level of herbivory increased from > 1% on the vole-free island to < 4% on the island with the highest vote density. The plant character that explained most of the variance in the level of invertebrate herbivory was leaf size. Since the vote densities have been altered by human intervention and their numbers are largely governed by predation rather than food quality, the positive correlation between vote densities and level of invertebrate herbivory is probably due to a facilitative effect of votes on invertebrate herbivores, mediated through changes in plant chemistry. We suggest that votes affect susceptibility of willows to invertebrate herbivory both directly by winter browsing and indirectly by reducing the abundance of competing plants

Publicerad i

2007, Volym: 14, nummer: 1, sidor: 48-54