Effects of combined ozone and nitrogen deposition on the in situ properties of eleven key plant species of a subalpine pasture |
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Authors: | Seraina Bassin Roland A. Werner Karin Sörgel Matthias Volk Nina Buchmann Jürg Fuhrer |
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Affiliation: | (1) Air Pollution and Climate Group, Agroscope Research Station ART, Reckenholzstrasse 191, 8046 Zurich, Switzerland;(2) Institute of Plant Sciences, ETH Zurich, 8092 Zurich, Switzerland |
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Abstract: | Tropospheric O3 and deposition of reactive N threaten the composition and function of natural and semi-natural vegetation even in remote regions. However, little is known about effects of these pollutants individually or in combination on plant species in alpine habitats. We analyzed 11 frequent plant species of a subalpine Geo-Montani-Nardetum pasture exposed at 2,000 m a.s.l. in the Swiss Alps during 3 years using a factorial free-air exposure system with three concentrations of O3 and five rates of N application. The aim was to detect subtle effects on leaf chlorophyll and N concentrations, leaf weight, specific leaf area (SLA), and δ18O and δ13C as proxies for gas exchange. We expected that the species’ responsiveness to O3 and N would be related to their functional traits and that N-induced changes in these traits would modify the species’ response to O3 via increased growth and higher leaf conductance (g s). Most species reacted to N supply with the accumulation of N and chlorophyll, but with no change in SLA, g s, and growth, except Carex sempervirens which showed increased water use efficiency and leaf weight. Elevated O3 reduced g s in most species, but this was not related to a reduction in leaf weight, which was recorded in half of the species. Contrary to our expectation, the magnitude of the response to both O3 and N was not related to species-specific traits such as SLA or g s. No pronounced O3 × N interactions were observed. In conclusion, since for most species neither N nor gas exchange limited growth, their short-term response to O3 and N and to their combination was small. O3 × N interactive effects are expected to be more pronounced in habitats where species are more responsive to N due to favorable growth conditions in terms of nutrient availability and temperature. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. |
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Keywords: | Functional trait Species composition Stable isotope |
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