title: Litter quality as driving factor for plant nutrition via grazing of protozoa on soil microorganisms.
abstract: Plant residues provide a major source of nitrogen (N) for plant growth. Litter N mineralization varies with litter carbon-to-nitrogen (C-to-N) ratio and presence of bacterial-feeding fauna. We assessed the effect of amoebae, major bacterial feeders in soil, on mineralization of litter of low (high quality) and high C-to-N ratio (low quality) and evaluated consequences for plant growth. We used stable isotopes to determine plant N uptake from litter and plant C partitioning. Stable isotope probing of phospholipid fatty acids was used to follow incorporation of plant C into microorganisms. Amoebae increased plant N uptake independent of litter quality and thereby the biomass of shoots and roots by 33% and 66%, respectively. Plant allocation of total (13)C to roots in low (42%) exceeded that of high-quality litter treatments (26%). Amoebae increased plant allocation of (13)C to roots by 37%. Microbial community structure and incorporation of (13)C into PLFAs varied significantly with litter quality and in the low-quality litter treatment also with the presence of amoebae. Overall, the results suggest that in particular at low nutrient conditions, root-derived C fosters the mobilization of bacterial N by protozoa, thereby increasing plant growth when microorganisms and plants compete for nutrients.
authors.affiliation: Université de Lorraine UMR 1121 INRA Agronomie et Environnement Nancy-Colmar, Vandoeuvre-lès-Nancy, France. rkoller@uni-koeln.de
authors.forename: Robert
authors.initials: R
authors.lastname: Koller
authors.forename: Christophe
authors.initials: C
authors.lastname: Robin
authors.forename: Michael
authors.initials: M
authors.lastname: Bonkowski
authors.forename: Liliane
authors.initials: L
authors.lastname: Ruess
authors.forename: Stefan
authors.initials: S
authors.lastname: Scheu
mesh_terms: D000048:Acanthamoeba / Q000502:physiology; D001419:Bacteria / Q000378:metabolism; D018533:Biomass; D002244:Carbon / Q000032:analysis; D017753:Ecosystem; D005227:Fatty Acids / Q000032:analysis; D009584:Nitrogen / Q000032:analysis; D010743:Phospholipids / Q000737:chemistry; D063245:Plant Development; D018517:Plant Roots / Q000378:metabolism; D010943:Plantago / Q000737:chemistry / Q000254:growth & development / Q000378:metabolism; D010944:Plants / Q000737:chemistry / Q000378:metabolism; D058441:Rhizosphere; D012988:Soil Microbiology
chemical_list: D005227:Fatty Acids; D010743:Phospholipids; D002244:Carbon; D009584:Nitrogen
keywords: 13CO2 labelling; PLFA; mineralization; rhizosphere; stable isotope probing