title: Nitrogen deposition alters nitrogen cycling and reduces soil carbon content in low-productivity semiarid Mediterranean ecosystems.
abstract: Anthropogenic N deposition poses a threat to European Mediterranean ecosystems. We combined data from an extant N deposition gradient (4.3-7.3 kg N ha⁻¹ yr⁻¹) from semiarid areas of Spain and a field experiment in central Spain to evaluate N deposition effects on soil fertility, function and cyanobacteria community. Soil organic N did not increase along the extant gradient. Nitrogen fixation decreased along existing and experimental N deposition gradients, a result possibly related to compositional shifts in soil cyanobacteria community. Net ammonification and nitrification (which dominated N-mineralization) were reduced and increased, respectively, by N fertilization, suggesting alterations in the N cycle. Soil organic C content, C:N ratios and the activity of β-glucosidase decreased along the extant gradient in most locations. Our results suggest that semiarid soils in low-productivity sites are unable to store additional N inputs, and that are also unable to mitigate increasing C emissions when experiencing increased N deposition.
authors.affiliation: Museo Nacional de Ciencias Naturales, Consejo Superior de Investigaciones Científicas, C/Serrano 115 Bis, 28006 Madrid, Spain. raul.ochoa@mncn.csic.es
authors.forename: Raúl
authors.initials: R
authors.lastname: Ochoa-Hueso
authors.forename: Fernando T
authors.initials: FT
authors.lastname: Maestre
authors.forename: Asunción
authors.initials: A
authors.lastname: de Los Ríos
authors.forename: Sergio
authors.initials: S
authors.lastname: Valea
authors.forename: Mark R
authors.initials: MR
authors.lastname: Theobald
authors.forename: Marta G
authors.initials: MG
authors.lastname: Vivanco
authors.forename: Esteban
authors.initials: E
authors.lastname: Manrique
authors.forename: Mathew A
authors.initials: MA
authors.lastname: Bowker
mesh_terms: D000393:Air Pollutants / Q000032:analysis* / Q000633:toxicity; D002244:Carbon / Q000032:analysis*; D057965:Carbon Sequestration; D017753:Ecosystem; D009584:Nitrogen / Q000032:analysis* / Q000633:toxicity; D058458:Nitrogen Cycle / Q000187:drug effects*; D012987:Soil / Q000737:chemistry*; D012988:Soil Microbiology; D013030:Spain
chemical_list: D000393:Air Pollutants; D012987:Soil; D002244:Carbon; D009584:Nitrogen