Ozone critical levels for (semi-)natural vegetation dominated by perennial grassland species
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RESEARCH ARTICLE
Ozone critical levels for (semi-)natural vegetation dominated by perennial grassland species Felicity Hayes 1
&
Harry Harmens 1 & Gina Mills 1 & Jürgen Bender 2 & Ludger Grünhage 3
Received: 27 July 2020 / Accepted: 17 November 2020 # Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract New critical levels for ozone based on accumulated flux through stomata (phytotoxic ozone dose, POD), for temperate perennial grassland (semi-)natural vegetation, have been agreed for use within the Convention on Long-Range Transboundary Air Pollution. These were based on data from several experiments conducted under naturally fluctuating environmental conditions that were combined and analysed to give linear dose-response relationships. Dose-response functions and flux-based critical levels were derived based on biomass and flower number. These parameters showed a statistically significant decline with increasing accumulated stomatal ozone flux. The functions and critical levels derived are based on sensitive species and can be used for risk assessments of the damaging effect of ozone on temperate vegetation communities dominated by perennial grassland species. The critical level based on flower number was lower than that for biomass, representing the greater sensitivity of flower number to ozone pollution. Keywords Ozone . Biodiversity . Flowering . Stomata . Critical level . biomass
Introduction Tropospheric ozone is a secondary pollutant formed by reactions of precursors, which mainly originate from anthropogenic sources, in the presence of sunlight. Baseline ozone concentrations increased rapidly during the late twentieth century and at northern mid-latitudes approximately doubled over the period of 1950 to 2000 (Parrish et al. 2012). These levels caused significant damage to vegetation such that impacts could be observed on plants in ambient air conditions, with field evidence of effects demonstrated on over 80 (semi-)natural vegetation species in 16 European countries over the period of 1994–2006 (Mills et al. 2011a). Since approximately Responsible Editor: Gangrong Shi * Felicity Hayes [email protected] 1
UK Centre for Ecology & Hydrology, Environment Centre Wales, Deiniol Road, Bangor, Gwynedd LL57 2UW, UK
2
Thünen Institute of Biodiversity, Bundesallee 65, 38116 Braunschweig, Germany
3
Institut für Pflanzenökologie, Heinrich-Buff-Ring 26, 35392 Giessen, Germany
2000, the rate of increase in ozone concentration has slowed, and for individual monitoring sites in Europe, there can be decreasing, increasing or no trend in summertime daytime ozone concentrations over the period of 2000–2014 depending on the individual site (Chang et al. 2017). This is thought to reflect changes in emissions of ozone precursors such as carbon monoxide, methane, non-methane volatile organic compounds and nitrogen oxides. Many models of future ozone projections are very sensitive to small changes in emissions and/or climate change (Young et al. 2013). Despite some efforts to reduce emissions of precursor mo
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