title: Spatial patterns and dynamic responses of arctic food webs corroborate the exploitation ecosystems hypothesis (EEH).
abstract: According to the exploitation ecosystems hypothesis (EEH), productive terrestrial ecosystems are characterized by community-level trophic cascades, whereas unproductive ecosystems harbor food-limited grazers, which regulate community-level plant biomass. We tested this hypothesis along arctic-alpine productivity gradients at the Joatka field base, Finnmark, Norway. In unproductive habitats, mammalian predators were absent and plant biomass was constant, whereas herbivore biomass varied, reflecting the productivity of the habitat. In productive habitats, predatory mammals were persistently present and plant biomass varied in space, but herbivore biomass did not. Plant biomass of productive tundra scrublands declined by 40% when vegetation blocks were transferred to predation-free islands. Corresponding transfer to herbivore-free islands triggered an increase in plant biomass. Fertilization of an unproductive tundra heath resulted in a fourfold increase in rodent density and a corresponding increase in winter grazing activity, whereas the total aboveground plant biomass remained unchanged. These results corroborate the predictions of the EEH, implying that the endotherm community and the vegetation of the North European tundra behaves dynamically as if each trophic level consisted of a single population, in spite of local co-occurrence of >20 plant species representing different major taxonomic groups, growth forms, and defensive strategies.
authors.affiliation: Department of Ecology and Environmental Science, Umeå University, SE-90187 Umeå, Sweden. maano.aunapuu@z.lst.se
authors.forename: Maano
authors.initials: M
authors.lastname: Aunapuu
authors.forename: Jonas
authors.initials: J
authors.lastname: Dahlgren
authors.forename: Tarja
authors.initials: T
authors.lastname: Oksanen
authors.forename: Doris
authors.initials: D
authors.lastname: Grellmann
authors.forename: Lauri
authors.initials: L
authors.lastname: Oksanen
authors.forename: Johan
authors.initials: J
authors.lastname: Olofsson
authors.forename: Ullar
authors.initials: U
authors.lastname: Rammul
authors.forename: Michael
authors.initials: M
authors.lastname: Schneider
authors.forename: Bernt
authors.initials: B
authors.lastname: Johansen
authors.forename: Hans Olav
authors.initials: HO
authors.lastname: Hygen
mesh_terms: D000818:Animals; D001110:Arctic Regions; D003411:Arvicolinae / Q000502:physiology; D018533:Biomass; D046091:Charadriiformes / Q000502:physiology; D046093:Falconiformes / Q000502:physiology; D005247:Feeding Behavior; D005306:Fertilization; D020387:Food Chain; D005589:Foxes / Q000502:physiology; D046428:Hawks / Q000502:physiology; D008954:Models, Biological; D045969:Mustelidae / Q000502:physiology; D009664:Norway; D063245:Plant Development; D011156:Population Density; D011157:Population Dynamics; D011235:Predatory Behavior