title: Estimating the uptake of traffic-derived NO2from15N abundance in Norway spruce needles.
abstract: The15N ratio of nitrogen oxides (NOx) emitted from vehicles, measured in the air adjacent to a highway in the Swiss Middle Land, was very high [δ15N(NO2) = +5.7‰]. This high15N abundance was used to estimate long-term NO2dry deposition into a forest ecosystem by measuring δ15N in the needles and the soil of potted and autochthonous spruce trees [Picea abies (L.) Karst] exposed to NO2in a transect orthogonal to the highway. δ15N in the current-year needles of potted trees was 2.0‰ higher than that of the control after 4 months of exposure close to the highway, suggesting a 25% contribution to the N-nutrition of these needles. Needle fall into the pots was prevented by grids placed above the soil, while the continuous decomposition of needle litter below the autochthonous trees over previous years has increased δ15N values in the soil, resulting in parallel gradients of δ15N in soil and needles with distance from the highway. Estimates of NO2uptake into needles obtained from the δ15N data were significantly correlated with the inputs calculated with a shoot gas exchange model based on a parameterisation widely used in deposition modelling. Therefore, we provide an indication of estimated N inputs to forest ecosystems via dry deposition of NO2at the receptor level under field conditions.
authors.affiliation: Institute of Plant Physiology, University of Berne, CH-3013 Berne, Switzerland, , , , , , CH.
authors.forename: M
authors.initials: M
authors.lastname: Ammann
authors.affiliation: Paul Scherrer Institute, CH-5232 Villigen, Switzerland e-mail: markus.ammann@psi.ch, Tel.: +41-56-3104049, Fax: +41-56-3104435, , , , , , CH.
authors.forename: R
authors.initials: R
authors.lastname: Siegwolf
authors.affiliation: Austrian Research Centre Seibersdorf, A-2444 Seibersdorf, Austria, , , , , , AT.
authors.forename: F
authors.initials: F
authors.lastname: Pichlmayer
authors.affiliation: Institute of Plant Physiology, University of Berne, CH-3013 Berne, Switzerland, , , , , , CH.
authors.forename: M
authors.initials: M
authors.lastname: Suter
authors.affiliation: Paul Scherrer Institute, CH-5232 Villigen, Switzerland e-mail: markus.ammann@psi.ch, Tel.: +41-56-3104049, Fax: +41-56-3104435, , , , , , CH.
authors.forename: M
authors.initials: M
authors.lastname: Saurer
authors.affiliation: Institute of Plant Physiology, University of Berne, CH-3013 Berne, Switzerland, , , , , , CH.
authors.forename: C
authors.initials: C
authors.lastname: Brunold
keywords: Forests; Key words15N; NO2 deposition; Picea abies; Spruce