title: Moth herbivory enhances resource turnover in subarctic mountain birch forests?
abstract: Massive moth outbreaks cause large-scale damage in subarctic mountain birch forests with a concomitant decrease in carbon flux to mycorrhizal fungi and an increased deposition of dissolved carbon and nutrients as moth frass into soil. We investigated impacts of moth herbivory along three replicated gradients with three levels of moth herbivory (undamaged, once damaged, repeatedly damaged) on soil nutrient levels and biological parameters. We found an increase in soil nutrients and in the biomass of enchytraeid worms, which are key faunal decomposers. Fungi bacteria ratio and C:N ratio decreased in humus with increasing severity of herbivory. Our findings suggest enhanced resource turnover in mountain birch forests due to massive moth herbivory. This may provide a shortcut for carbon and nutrient input to subarctic soils, which largely bypasses the main routes of carbon from plants to soil via mycorrhizal and litter-decomposing fungi. Moreover, a temporal shift occurs in carbon allocation to soil, providing decomposers an opportunity to use an early-season peak in resource availability. Our results suggest a hitherto unappreciated role of massive insect herbivore attacks on resource dynamics in subarctic ecosystems.
authors.affiliation: Department of Biology, University of Oulu, P.O. Box 3000, 90014 Oulu, Finland. maarit.kaukonen@oulu.fi
authors.forename: Maarit
authors.initials: M
authors.lastname: Kaukonen
authors.forename: Anna Liisa
authors.initials: AL
authors.lastname: Ruotsalainen
authors.forename: Piippa R
authors.initials: PR
authors.lastname: Wäli
authors.forename: Minna K
authors.initials: MK
authors.lastname: Männistö
authors.forename: Heikki
authors.initials: H
authors.lastname: Setälä
authors.forename: Karita
authors.initials: K
authors.lastname: Saravesi
authors.forename: Karoliina
authors.initials: K
authors.lastname: Huusko
authors.forename: Annamari
authors.initials: A
authors.lastname: Markkola
mesh_terms: D000818:Animals; D029662:Betula / Q000502:physiology*; D017753:Ecosystem; D060434:Herbivory / Q000502:physiology*; D009036:Moths / Q000502:physiology*; D011157:Population Dynamics; D014197:Trees / Q000502:physiology*