title: Host and tissue variations overshadow the response of boreal moss-associated fungal communities to increased nitrogen load.
abstract: Human activity has more than doubled the amount of nitrogen entering the global nitrogen cycle, and the boreal forest biome is a nitrogen-limited ecosystem sensitive to nitrogen load perturbation. Although bryophyte-associated microbes contribute significantly to boreal forest ecosystem function, particularly in carbon and nitrogen cycling, little is known about their responses to anthropogenic global change. Amplicon pyrosequencing of the ITS2 region of rDNA was used to investigate how fungal communities associated with three bryophyte species responded to increased nitrogen loads in a long-term fertilization experiment in a boreal Picea abies forest in southern Norway. Overall, OTU richness, community composition and the relative abundance of specific ecological guilds were primarily influenced by host species identity and tissue type. Although not the primary factor affecting fungal communities, nitrogen addition did impact the abundance of specific guilds of fungi and the resulting overall community composition. Increased nitrogen loads decreased ectomycorrhizal abundance, with Amphinema, Cortinarius, Russula and Tylospora OTUs responding negatively to fertilization. Pathogen abundance increased with fertilization, particularly in the moss pathogen Eocronartium. Saprophytic fungi were both positively and negatively impacted by the nitrogen addition, indicating a complex community level response. The overshadowing of the effects of increased nitrogen loads by variation related to host and tissue type highlights the complexity of bryophyte-associated microbial communities and the intricate nature of their responses to anthropogenic global change.
authors.affiliation: Department of Ecology and Natural Resource Management, Norwegian University of Life Sciences, PO Box 5003, NO-1432, Ås, Norway.|Section for Genetics and Evolutionary Biology, Department of Biosciences, University of Oslo, PO Box 1066 Blindern, NO-0316, Oslo, Norway.
authors.forename: Marie L
authors.initials: ML
authors.lastname: Davey
authors.affiliation: Department of Ecology and Natural Resource Management, Norwegian University of Life Sciences, PO Box 5003, NO-1432, Ås, Norway.
authors.forename: Marte J
authors.initials: MJ
authors.lastname: Skogen
authors.affiliation: Norwegian Forest and Landscape Institute, Fanaflaten 4, NO-5244, Fana, Norway.
authors.forename: Einar
authors.initials: E
authors.lastname: Heegaard
authors.affiliation: Department of Botany, Natural History Museum, University of Oslo, PO Box 1172 Blindern, NO-0318, Oslo, Norway.
authors.forename: Rune
authors.initials: R
authors.lastname: Halvorsen
authors.affiliation: Section for Genetics and Evolutionary Biology, Department of Biosciences, University of Oslo, PO Box 1066 Blindern, NO-0316, Oslo, Norway.
authors.forename: Håvard
authors.initials: H
authors.lastname: Kauserud
authors.affiliation: Department of Ecology and Natural Resource Management, Norwegian University of Life Sciences, PO Box 5003, NO-1432, Ås, Norway.
authors.forename: Mikael
authors.initials: M
authors.lastname: Ohlson
mesh_terms: D044002:Bryophyta / Q000382:microbiology*; D021903:DNA, Ribosomal Spacer / Q000235:genetics; D065928:Forests; D038821:Mycorrhizae / Q000145:classification*; D009584:Nitrogen / Q000032:analysis*; D058458:Nitrogen Cycle; D009664:Norway; D014197:Trees
chemical_list: D021903:DNA, Ribosomal Spacer; D009584:Nitrogen
keywords: 
  Dicranum scoparium
  ; 
  Hylocomium splendens
  ; 
  Pleurozium schreberi
  ; biodiversity; bryophilous fungi; nitrogen fertilization