title: Elevated ozone and nitrogen deposition affect nitrogen pools of subalpine grassland.
abstract: In a free-air fumigation experiment with subalpine grassland, we studied long-term effects of elevated ozone (O3) and nitrogen (N) deposition on ecosystem N pools and on the fate of anthropogenic N. At three times during the seventh year of exposure, N pools and recovery of a stable isotope tracer ((15)N) were determined in above- and belowground plant parts, and in the soil. Plants were much better competitors for (15)N than soil microorganisms. Plant N pools increased by 30-40% after N addition, while soil pools remained unaffected, suggesting that most of the extra N was taken up and stored in plant biomass, thus preventing the ecosystem from acquiring characteristics of eutrophication. Elevated O3 caused an increase of N in microbial biomass and in stabilized soil N, probably resulting from increased litter input and lower litter quality. Different from individual effects, the interaction between the pollutants remained partly unexplained.
authors.affiliation: Agroscope, Institute of Sustainability Sciences ISS, Reckenholzstrasse 191, CH-8046 Zurich, Switzerland. Electronic address: seraina.bassin@agroscope.admin.ch.
authors.forename: Seraina
authors.initials: S
authors.lastname: Bassin
authors.affiliation: Agroscope, Institute of Sustainability Sciences ISS, Reckenholzstrasse 191, CH-8046 Zurich, Switzerland.
authors.forename: David
authors.initials: D
authors.lastname: Käch
authors.affiliation: Agroscope, Institute of Sustainability Sciences ISS, Reckenholzstrasse 191, CH-8046 Zurich, Switzerland.
authors.forename: Alain
authors.initials: A
authors.lastname: Valsangiacomo
authors.affiliation: Agroscope, Institute of Sustainability Sciences ISS, Reckenholzstrasse 191, CH-8046 Zurich, Switzerland.
authors.forename: Jochen
authors.initials: J
authors.lastname: Mayer
authors.affiliation: Agroscope, Institute of Sustainability Sciences ISS, Reckenholzstrasse 191, CH-8046 Zurich, Switzerland.
authors.forename: Hans-Rudolf
authors.initials: HR
authors.lastname: Oberholzer
authors.affiliation: Agroscope, Institute of Sustainability Sciences ISS, Reckenholzstrasse 191, CH-8046 Zurich, Switzerland.
authors.forename: Matthias
authors.initials: M
authors.lastname: Volk
authors.affiliation: Agroscope, Institute of Sustainability Sciences ISS, Reckenholzstrasse 191, CH-8046 Zurich, Switzerland.
authors.forename: Jürg
authors.initials: J
authors.lastname: Fuhrer
mesh_terms: D018533:Biomass; D017753:Ecosystem; D065948:Grassland; D009584:Nitrogen / Q000032:analysis*; D010126:Ozone / Q000494:pharmacology*; D012987:Soil / Q000737:chemistry
chemical_list: D012987:Soil; D010126:Ozone; D009584:Nitrogen
keywords: Grassland; Nitrogen; Ozone; Soil; Stable isotopes