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Predators indirectly protect tundra plants by reducing herbivore abundance

Authors

  • Peter A. Hambäck,

  • Lauri Oksanen,

  • Per Ekerholm,

  • Åsa Lindgren,

  • Tarja Oksanen,

  • Michael Schneider


P. A. Hambäck, L. Oksanen, P. Ekerholm, Å. Lindgren, T. Oksanen and M. Schneider, Department of Ecology and Environmental Sciences, Umeå University, SE-901 87 Umeå, Sweden Present address for PAH and ÅL: Dept of Botany, Stockholm Univ., SE-106 91 Stockholm, Sweden (peter.hamback@botan.su.se). Present address for MS: County Administration, Västerbotten County, SE-901 86 Umeå, Sweden.

Abstract

The role of predators in controlling herbivores and indirectly affecting plant abundance is controversial, and some have argued that such trophic cascades are rare in terrestrial habitats. To examine the potential of trophic cascades in a shrubby tundra ecosystem, vole densities, plant damage and plant cover were examined in areas with and without small mammal predators. On islands without predators, vole densities and plant damage were upto five times higher compared with predator-rich mainland habitats. As a consequence, the abundance of three out of five dwarf shrub species was substantially reduced on predator-free islands, providing evidence for strong cascading effects in a rather large-scale terrestrial system. Herbs on the other hand were not affected by the increased herbivory on islands. This suggests that the strength of trophic cascades also depends on the interaction between plant type and seasonality.

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