title: Contrasting effects of nitrogen addition on soil respiration in two Mediterranean ecosystems.
abstract: Increased atmospheric nitrogen (N) deposition is known to alter ecosystem carbon source-sink dynamics through changes in soil CO2fluxes. However, a limited number of experiments have been conducted to assess the effects of realistic N deposition in the Mediterranean Basin, and none of them have explored the effects of N addition on soil respiration (Rs). To fill this gap, we assessed the effects of N supply on Rsdynamics in the following two Mediterranean sites: Capo Caccia (Italy), where 30 kg ha-1year-1was supplied for 3 years, and El Regajal (Spain), where plots were treated with 10, 20, or 50 kg N ha-1year-1for 8 years. Results show a complex, non-linear response of soil respiration (Rs) to N additions with Rsoverall increasing at Capo Caccia and decreasing at El Regajal. This suggests that the response of Rsto N addition depends on dose and duration of N supply, and the existence of a threshold above which the N introduced in the ecosystem can affect the ecosystem's functioning. Soil cover and seasonality of precipitations also play a key role in determining the effects of N on Rsas shown by the different responses observed across seasons and in bare soil vs. the soil under canopy of the dominant species. These results show how increasing rates of N addition may influence soil C dynamics in semiarid ecosystems in the Mediterranean Basin and represent a valuable contribution for the understanding and the protection of Mediterranean ecosystems.
authors.affiliation: Department of Science for Nature and Environmental Resources (DipNET), University of Sassari, Via Enrico de Nicola, No. 9, 07100, Sassari, Italy. mlocascio@uniss.it.|Euro-Mediterranean Centre on Climate Change (CMCC), IAFES Division, Via Enrico de Nicola, No. 9, 07100, Sassari, Italy. mlocascio@uniss.it.
authors.forename: Mauro
authors.identifier: http://orcid.org/0000-0002-5050-179X
authors.initials: M
authors.lastname: Lo Cascio
authors.affiliation: Department of Science for Nature and Environmental Resources (DipNET), University of Sassari, Via Enrico de Nicola, No. 9, 07100, Sassari, Italy.
authors.forename: Lourdes
authors.initials: L
authors.lastname: Morillas
authors.affiliation: Department of Ecology, Autonomous University of Madrid, Darwin St., 2, 28049, Madrid, Spain.
authors.forename: Raúl
authors.initials: R
authors.lastname: Ochoa-Hueso
authors.affiliation: Centre for Ecology, Evolution and Environmental Changes (cE3c), Faculdade de Ciências, Universidade de Lisboa, Campo Grande, 1749-016, Lisbon, Portugal.
authors.forename: Silvana
authors.initials: S
authors.lastname: Munzi
authors.affiliation: Department of Science for Nature and Environmental Resources (DipNET), University of Sassari, Via Enrico de Nicola, No. 9, 07100, Sassari, Italy.
authors.forename: Javier
authors.initials: J
authors.lastname: Roales
authors.affiliation: Department of Forest Ecology and Management, Swedish University of Agricultural Sciences, SE-901 83, Umeå, Sweden.
authors.forename: Niles J
authors.initials: NJ
authors.lastname: Hasselquist
authors.affiliation: Department Biogeography and Global Change, Spanish National Research Council (MNCN-CSIC), National Museum of Natural Sciences, C/Serrano 115 Dpdo, 28006, Madrid, Spain.
authors.forename: Esteban
authors.initials: E
authors.lastname: Manrique
authors.affiliation: Department of Science for Nature and Environmental Resources (DipNET), University of Sassari, Via Enrico de Nicola, No. 9, 07100, Sassari, Italy.|Euro-Mediterranean Centre on Climate Change (CMCC), IAFES Division, Via Enrico de Nicola, No. 9, 07100, Sassari, Italy.
authors.forename: Donatella
authors.initials: D
authors.lastname: Spano
authors.affiliation: Department of Science for Nature and Environmental Resources (DipNET), University of Sassari, Via Enrico de Nicola, No. 9, 07100, Sassari, Italy.
authors.forename: Renée Abou
authors.initials: RA
authors.lastname: Jaoudé
authors.affiliation: Department of Science for Nature and Environmental Resources (DipNET), University of Sassari, Via Enrico de Nicola, No. 9, 07100, Sassari, Italy.|Euro-Mediterranean Centre on Climate Change (CMCC), IAFES Division, Via Enrico de Nicola, No. 9, 07100, Sassari, Italy.
authors.forename: Simone
authors.initials: S
authors.lastname: Mereu
mesh_terms: D057965:Carbon Sequestration; D017753:Ecosystem; D007558:Italy; D009584:Nitrogen / Q000737:chemistry* / Q000378:metabolism; D010944:Plants; D012621:Seasons; D012987:Soil / Q000737:chemistry*; D012988:Soil Microbiology; D013030:Spain
chemical_list: D012987:Soil; D009584:Nitrogen
keywords: Air pollution; CO2 emission; Carbon and nitrogen interaction; Carbon use efficiency (CUE); Fertilization experiment; Global change; Soil nutrients; Spatial-temporal variability