title: Soil fertilization leads to a decline in between-samples variability of microbial community δ13C profiles in a grassland fertilization experiment.
abstract: Gas chromatography combustion isotope ratio mass spectrometry (GC-C-IRMS) was used to measure the (13)C/(12)C ratios of PLFAs at natural abundance levels from a temperate grassland nitrogen (N) and phosphorus (P) factorial fertilization experiment in northern Greece. In each plot two rhizosphere samples were derived centred around individual Agrostis capillaris and Prunella vulgaris plants. It was hypothesized that the isotopic signal of microbes that preferentially feed on recalcitrant litter such as fungi would be modified by fertilization more strongly than that of opportunistic microbes using labile C. Microbial community δ(13)C was affected by both P and N fertilization regime and plant species identity. However, we have been unable to detect significant nutrient effects on individual groups of microbes when analyzed separately in contrast to our original hypothesis. Intra-treatment variability, as evaluated from Hartley's F(max) tests in the five first PCA components axes as well as the size of the convex hulls in PCA scoreplots and Mahalanobis distances, was considerably higher in the non-fertilized controls. Moreover, a significant relationship was established between the change in PLFA abundances and their respective changes in δ(13)C for the aggregate of samples and those simultaneously fertilized with N and P. We conclude that use of compound specific isotope analysis in the absence of labelling represents a valuable and overlooked tool in obtaining an insight of microbial community functioning.
authors.affiliation: Laboratory of Ecology and Environmental Protection, Faculty of Agriculture, Aristotle University of Thessaloniki, Thessaloniki, Greece.
authors.forename: Stavros D
authors.initials: SD
authors.lastname: Veresoglou
authors.forename: Barry
authors.initials: B
authors.lastname: Thornton
authors.forename: George
authors.initials: G
authors.lastname: Menexes
authors.forename: Andreas P
authors.initials: AP
authors.lastname: Mamolos
authors.forename: Demetrios S
authors.initials: DS
authors.lastname: Veresoglou
mesh_terms: D031703:Agrostis / Q000502:physiology; D001419:Bacteria / Q000254:growth & development*; D002244:Carbon / Q000032:analysis*; D057486:Carbon Cycle; D002247:Carbon Isotopes; D017753:Ecosystem; D005308:Fertilizers; D005658:Fungi / Q000502:physiology*; D008401:Gas Chromatography-Mass Spectrometry / Q000379:methods; D006115:Greece; D059013:Microbial Consortia / Q000502:physiology*; D009584:Nitrogen / Q000737:chemistry; D010758:Phosphorus / Q000737:chemistry; D031347:Prunella / Q000502:physiology; D012987:Soil / Q000032:analysis; D012988:Soil Microbiology; D018709:Statistics, Nonparametric
chemical_list: D002247:Carbon Isotopes; D005308:Fertilizers; D012987:Soil; D010758:Phosphorus; D002244:Carbon; D009584:Nitrogen