title: Local Environmental Factors Drive Divergent Grassland Soil Bacterial Communities in the Western Swiss Alps.
abstract: Mountain ecosystems are characterized by a diverse range of climatic and topographic conditions over short distances and are known to shelter a high biodiversity. Despite important progress, still little is known on bacterial diversity in mountain areas. Here, we investigated soil bacterial biogeography at more than 100 sampling sites randomly stratified across a 700-km2area with 2,200-m elevation gradient in the western Swiss Alps. Bacterial grassland communities were highly diverse, with 12,741 total operational taxonomic units (OTUs) across 100 sites and an average of 2,918 OTUs per site. Bacterial community structure was correlated with local climatic, topographic, and soil physicochemical parameters with high statistical significance. We found pH (correlated with % CaO and % mineral carbon), hydrogen index (correlated with bulk gravimetric water content), and annual average number of frost days during the growing season to be among the groups of the most important environmental drivers of bacterial community structure. In contrast, bacterial community structure was only weakly stratified as a function of elevation. Contrasting patterns were discovered for individual bacterial taxa. Acidobacteria responded both positively and negatively to pH extremes. Various families within the Bacteroidetes responded to available phosphorus levels. Different verrucomicrobial groups responded to electrical conductivity, total organic carbon, water content, and mineral carbon contents. Alpine grassland bacterial communities are thus highly diverse, which is likely due to the large variety of different environmental conditions. These results shed new light on the biodiversity of mountain ecosystems, which were already identified as potentially fragile to anthropogenic influences and climate change.
  
  
  
  This article addresses the question of how microbial communities in alpine regions are dependent on local climatic and soil physicochemical variables. We benefit from a unique 700-km2study region in the western Swiss Alps region, which has been exhaustively studied for macro-organismal and fungal ecology, and for topoclimatic modeling of future ecological trends, but without taking into account soil bacterial diversity. Here, we present an in-depth biogeographical characterization of the bacterial community diversity in this alpine region across 100 randomly stratified sites, using 56 environmental variables. Our exhaustive sampling ensured the detection of ecological trends with high statistical robustness. Our data both confirm previously observed general trends and show many new detailed trends for a wide range of bacterial taxonomic groups and environmental parameters.
authors.affiliation: Department of Fundamental Microbiology, University of Lausanne, Lausanne, Switzerland erika.yashiro@unil.ch.
authors.forename: Erika
authors.initials: E
authors.lastname: Yashiro
authors.affiliation: Department of Fundamental Microbiology, University of Lausanne, Lausanne, Switzerland Department of Ecology and Evolution, University of Lausanne, Lausanne, Switzerland.
authors.forename: Eric
authors.initials: E
authors.lastname: Pinto-Figueroa
authors.affiliation: Institute of Earth Surface Dynamics, University of Lausanne, Lausanne, Switzerland.
authors.forename: Aline
authors.initials: A
authors.lastname: Buri
authors.affiliation: Institute of Earth Surface Dynamics, University of Lausanne, Lausanne, Switzerland.
authors.forename: Jorge E
authors.initials: JE
authors.lastname: Spangenberg
authors.affiliation: Institute of Earth Sciences, University of Lausanne, Lausanne, Switzerland.
authors.forename: Thierry
authors.initials: T
authors.lastname: Adatte
authors.affiliation: Institute for Work and Health, University of Lausanne and Geneva, Epalinges-Lausanne, Switzerland.
authors.forename: Hélène
authors.identifier: 0000-0003-1467-8819
authors.initials: H
authors.lastname: Niculita-Hirzel
authors.affiliation: Department of Ecology and Evolution, University of Lausanne, Lausanne, Switzerland Institute of Earth Surface Dynamics, University of Lausanne, Lausanne, Switzerland.
authors.forename: Antoine
authors.initials: A
authors.lastname: Guisan
authors.affiliation: Department of Fundamental Microbiology, University of Lausanne, Lausanne, Switzerland.
authors.forename: Jan Roelof
authors.initials: JR
authors.lastname: van der Meer
mesh_terms: D061271:Acidobacteria / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D001419:Bacteria / Q000145:classification / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism*; D018407:Bacterial Physiological Phenomena; D041963:Bacteroidetes / Q000235:genetics / Q000302:isolation & purification / Q000502:physiology; D044822:Biodiversity; D002244:Carbon; D057231:Climate Change; D017753:Ecosystem; D004777:Environment; D005658:Fungi / Q000145:classification / Q000235:genetics / Q000302:isolation & purification / Q000378:metabolism; D065948:Grassland; D006863:Hydrogen-Ion Concentration; D059013:Microbial Consortia; D010758:Phosphorus; D012336:RNA, Ribosomal, 16S; D012621:Seasons; D012987:Soil / Q000737:chemistry; D012988:Soil Microbiology; D013557:Switzerland
chemical_list: D012336:RNA, Ribosomal, 16S; D012987:Soil; D010758:Phosphorus; D002244:Carbon