title: Influence of Lumbricus terrestris and Folsomia candida on N2O formation pathways in two different soils - with particular focus on N2emissions.
abstract: BACKGROUND
  The gaseous N losses mediated by soil denitrifiers are generally inferred by measuring N2O fluxes, but should include associated N2emissions, which may be affected by abiotic soil characteristics and biotic interactions. Soil fauna, particularly anecic earthworms and euedaphic collembola, alter the activity of denitrifiers, creating hotspots for denitrification. These soil fauna are abundant in perennial agroecosystems intended to contribute to more sustainable production of bioenergy.
  
  
  METHODS
  Two microcosm experiments were designed to evaluate gaseous N emissions from a silty loam and a sandy soil, both provided with litter from the bioenergy crop Silphium perfoliatum (cup-plant) and inoculated with an anecic earthworm (Lumbricus terrestris), which was added alone or together with an euedaphic collembola (Folsomia candida). In experiment 1, litter-derived N flux was determined by adding15N-labelled litter, followed by mass spectrometric analysis of N2and N2O isotopologues. In experiment 2, the δ18O values and15N site preference of N2O were determined by isotope ratio mass spectrometry to reveal underlying N2O formation pathways.
  
  
  RESULTS
  Lumbricus terrestris significantly increased litter-derived N2emissions in the loamy soil, from 174.5 to 1019.3 μg N2-N kg-1soil, but not in the sandy soil (non-significant change from 944.7 to 1054.7 μg N2-N kg-1soil). Earthworm feeding on plant litter resulted in elevated N2O emissions in both soils, derived mainly from turnover of the soil mineral N pool during denitrification. Folsomia candida did not affect N losses but showed a tendency to redirect N2O formation pathways from fungal to bacterial denitrification. The N2O/(N2+ N2O) product ratio was predominantly affected by abiotic soil characteristics (loamy soil: 0.14, sandy soil: 0.26).
  
  
  CONCLUSIONS
  When feeding on S. perfoliatum litter, the anecic L. terrestris, but not the euedaphic F. candida, has the potential to cause substantial N losses. Biotic interactions between the species are not influential, but abiotic soil characteristics have an effect. The coarse-textured sandy soil had lower gaseous N losses attributable to anecic earthworms. Copyright © 2016 John Wiley & Sons, Ltd.
authors: Johann Heinrich von Thünen-Institute (TI) - Federal Institute for Rural Areas, Forestry and Fisheries, Institute of Biodiversity, Bundesallee 50, D-38116, Braunschweig, Germany. quentin.schorpp@thuenen.de.
authors: Quentin
authors: Q
authors: Schorpp
authors: Johann Heinrich von Thünen-Institute (TI) - Federal Institute for Rural Areas, Forestry and Fisheries, Institute of Biodiversity, Bundesallee 50, D-38116, Braunschweig, Germany.
authors: Catharina
authors: C
authors: Riggers
authors: Johann Heinrich von Thünen-Institute (TI) - Federal Institute for Rural Areas, Forestry and Fisheries, Institute of Climate-Smart Agriculture, Bundesallee 50, D-38116, Braunschweig, Germany.
authors: Dominika
authors: D
authors: Lewicka-Szczebak
authors: Johann Heinrich von Thünen-Institute (TI) - Federal Institute for Rural Areas, Forestry and Fisheries, Institute of Climate-Smart Agriculture, Bundesallee 50, D-38116, Braunschweig, Germany.
authors: Anette
authors: A
authors: Giesemann
authors: Johann Heinrich von Thünen-Institute (TI) - Federal Institute for Rural Areas, Forestry and Fisheries, Institute of Climate-Smart Agriculture, Bundesallee 50, D-38116, Braunschweig, Germany.
authors: Reinhard
authors: R
authors: Well
authors: Johann Heinrich von Thünen-Institute (TI) - Federal Institute for Rural Areas, Forestry and Fisheries, Institute of Biodiversity, Bundesallee 50, D-38116, Braunschweig, Germany.
authors: Stefan
authors: S
authors: Schrader
mesh_terms: D000818:Animals; D001181:Arthropods / Q000378:metabolism*; D001419:Bacteria / Q000378:metabolism; D058440:Denitrification; D005658:Fungi / Q000378:metabolism; D009584:Nitrogen / Q000737:chemistry / Q000378:metabolism*; D009609:Nitrous Oxide / Q000737:chemistry / Q000378:metabolism*; D009835:Oligochaeta / Q000378:metabolism*; D012987:Soil / Q000737:chemistry* / Q000469:parasitology; D012988:Soil Microbiology
chemical_list: D012987:Soil; D009609:Nitrous Oxide; D009584:Nitrogen