title: Atmospheric N deposition alters connectance, but not functional potential among saprotrophic bacterial communities.
abstract: The use of co-occurrence patterns to investigate interactions between micro-organisms has provided novel insight into organismal interactions within microbial communities. However, anthropogenic impacts on microbial co-occurrence patterns and ecosystem function remain an important gap in our ecological knowledge. In a northern hardwood forest ecosystem located in Michigan, USA, 20 years of experimentally increased atmospheric N deposition has reduced forest floor decay and increased soil C storage. This ecosystem-level response occurred concomitantly with compositional changes in saprophytic fungi and bacteria. Here, we investigated the influence of experimental N deposition on biotic interactions among forest floor bacterial assemblages by employing phylogenetic and molecular ecological network analysis. When compared to the ambient treatment, the forest floor bacterial community under experimental N deposition was less rich, more phylogenetically dispersed and exhibited a more clustered co-occurrence network topology. Together, our observations reveal the presence of increased biotic interactions among saprotrophic bacterial assemblages under future rates of N deposition. Moreover, they support the hypothesis that nearly two decades of experimental N deposition can modify the organization of microbial communities and provide further insight into why anthropogenic N deposition has reduced decomposition, increased soil C storage and accelerated phenolic DOC production in our field experiment.
authors.affiliation: School of Natural Resources & Environment, University of Michigan, Ann Arbor, MI, 48109, USA.
authors.forename: Zachary B
authors.identifier: http://orcid.org/0000-0001-9160-7470
authors.initials: ZB
authors.lastname: Freedman
authors.affiliation: School of Natural Resources & Environment, University of Michigan, Ann Arbor, MI, 48109, USA.|Department of Ecology and Evolution, University of Michigan, Ann Arbor, MI, 48109, USA.
authors.forename: Donald R
authors.initials: DR
authors.lastname: Zak
mesh_terms: D001419:Bacteria / Q000145:classification*; D002244:Carbon / Q000737:chemistry; D004269:DNA, Bacterial / Q000235:genetics; D065928:Forests; D059014:High-Throughput Nucleotide Sequencing; D008824:Michigan; D059013:Microbial Consortia; D009584:Nitrogen / Q000737:chemistry*; D010802:Phylogeny; D017422:Sequence Analysis, DNA; D012987:Soil / Q000737:chemistry*; D012988:Soil Microbiology
chemical_list: D004269:DNA, Bacterial; D012987:Soil; D002244:Carbon; D009584:Nitrogen
keywords: N deposition; co-occurrence network; phylogenetic dispersion