title: Pikas (Ochotona princeps : Lagomorpha) as allogenic engineers in an alpine ecosystem.
abstract: Pikas (Ochotona princeps: Lagomorpha) build caches of vegetation ("haypiles"), which serve as a food source during winter in alpine and subalpine habitats. Haypiles appear to degrade over time and form patches of nutrient-rich soils in barren talus and scree areas. We sampled soils underneath and next to haypiles, and plants growing on and near haypiles in an alpine cirque in northwestern Wyoming, USA, to determine the effects of pika food caches on N, C, and C/N ratios in soils and plants. We found that (1) haypile soils had significantly higher carbon and nitrogen levels and lower C/N ratios than both adjacent soils and soils in the general study area, (2) two of three plant species tested (Polemonium viscosum and Oxyria digyna) had significantly higher levels of tissue percent N when growing on haypile soils, and (3) total standing plant biomass at the study site increased with soil percent N suggesting that vegetation was nitrogen limited. Pikas may therefore function as allogenic ecosystem engineers by modulating nutrient availability to plants.
authors.affiliation: Center for Ecological Research and Education, Department of Biological Science, Idaho State University, Pocatello, ID 83209, USA, , , , , , US.
authors.forename: Ken
authors.initials: K
authors.lastname: Aho
authors.affiliation: Center for Ecological Research and Education, Department of Biological Science, Idaho State University, Pocatello, ID 83209, USA, , , , , , US.
authors.forename: Nancy
authors.initials: N
authors.lastname: Huntly
authors.affiliation: Department of Ecological Botany, Umeå University, S-901 87 Umeå, Sweden Fax: +46-90-166691; e-mail: jonm@ekbot.umu.se, , , , , , SE.
authors.forename: Jon
authors.initials: J
authors.lastname: Moen
authors.affiliation: Department of Animal Ecology, Umeå University, S-901 87 Umeå, Sweden, , , , , , SE.
authors.forename: Tarja
authors.initials: T
authors.lastname: Oksanen
keywords: Indirect effects; Key words Herbivory; Nitrogen; Positive feedbacks; Soils