title: Microbial Potential for Ecosystem N Loss Is Increased by Experimental N Deposition.
abstract: Fossil fuel combustion and fertilizer use has increased the amount of biologically available N entering terrestrial ecosystems. Nonetheless, our understanding of how anthropogenic N may alter the physiological mechanisms by which soil microorganisms cycle N in soil is still developing. Here, we applied shotgun metagenomics to a replicated long-term field experiment to determine how two decades of experimental N deposition, at a rate expected by mid-century, has affected the genetic potential of the soil microbial community to cycle N in soils. Experimental N deposition lead to a significant and persistent increase in functional assemblages mediating N cycle transformations associated with ecosystem N loss (i.e., denitrification and nitrification), whereas functional assemblages associated with N input and retention (i.e., N fixation and microbial N assimilation) were less positively affected. Furthermore, the abundance and composition of microbial taxa, as well as functional assemblages involved in housekeeping functions (i.e., DNA replication) were unaffected by experimental N deposition. Taken together, our results suggest that functional genes and gene pathways associated with ecosystem N loss have been favored by experimental N deposition, which may represent a genetic mechanism fostering increased N loss as anthropogenic N deposition increases in the future.
authors.affiliation: School of Natural Resources & Environment, University of Michigan, Ann Arbor, Michigan, United States of America.
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, Michigan, United States of America.
authors.forename: Rima A
authors.initials: RA
authors.lastname: Upchurch
authors.affiliation: School of Natural Resources & Environment, University of Michigan, Ann Arbor, Michigan, United States of America.|Department of Ecology and Evolution, University of Michigan, Ann Arbor, Michigan, United States of America.
authors.forename: Donald R
authors.initials: DR
authors.lastname: Zak
mesh_terms: D001419:Bacteria / Q000145:classification / Q000235:genetics / Q000302:isolation & purification; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D004269:DNA, Bacterial / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism; D017753:Ecosystem; D065928:Forests; D056186:Metagenomics; D009584:Nitrogen / Q000378:metabolism*; D017422:Sequence Analysis, DNA; D012988:Soil Microbiology
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; D009584:Nitrogen