title: High tolerance of subalpine grassland to long-term ozone exposure is independent of N input and climatic drivers.
abstract: In a seven-year study, we tested effects of increased N and O3 deposition and climatic conditions on biomass of subalpine grassland. Ozone risk was assessed as exposure (AOT40) and as stomatal flux (POD0,1). We hypothesized that productivity is higher under N- and lower under O3 deposition, with interactions with climatic conditions. Aboveground biomass was best correlated with growing-degree days for May (GDDMay). Nitrogen deposition increased biomass up to 60% in the highest treatment, and 30% in the lowest addition. Also belowground biomass showed a positive N-response. Ozone enrichment had no effect on biomass, and no interaction between O3 and N was observed. Growth response to N deposition was not correlated to GDDMay or precipitation, but indicated a cumulative effect over time. Productivity of subalpine grassland is tolerant to increasing ozone exposure, independent of N input and climatic drivers. N deposition rates at current critical loads, strongly increase the grassland yield.
authors.affiliation: Agroscope, Air Pollution/Climate Group, Reckenholzstrasse 191, CH-8046 Zurich, Switzerland. Electronic address: matthias.volk@agroscope.admin.ch.
authors.forename: Matthias
authors.initials: M
authors.lastname: Volk
authors.affiliation: Agroscope, Air Pollution/Climate Group, Reckenholzstrasse 191, CH-8046 Zurich, Switzerland.
authors.forename: Veronika
authors.initials: V
authors.lastname: Wolff
authors.affiliation: Agroscope, Air Pollution/Climate Group, Reckenholzstrasse 191, CH-8046 Zurich, Switzerland.
authors.forename: Seraina
authors.initials: S
authors.lastname: Bassin
authors.affiliation: Agroscope, Air Pollution/Climate Group, Reckenholzstrasse 191, CH-8046 Zurich, Switzerland.
authors.forename: Christof
authors.initials: C
authors.lastname: Ammann
authors.affiliation: Agroscope, Air Pollution/Climate Group, Reckenholzstrasse 191, CH-8046 Zurich, Switzerland.
authors.forename: Jürg
authors.initials: J
authors.lastname: Fuhrer
mesh_terms: D000222:Adaptation, Physiological / Q000502:physiology*; D000393:Air Pollutants / Q000633:toxicity*; D000397:Air Pollution / Q000706:statistics & numerical data; D018533:Biomass; D031255:Carex Plant / Q000502:physiology; D002980:Climate; D017753:Ecosystem; D004777:Environment; D031751:Festuca / Q000502:physiology; D009584:Nitrogen / Q000032:analysis*; D010126:Ozone / Q000633:toxicity*
chemical_list: D000393:Air Pollutants; D010126:Ozone; D009584:Nitrogen
keywords: Air pollution; Critical load/level; Nitrogen; Phytotoxic ozone dose POD; Productivity