Article

A new flux-oriented concept to derive critical levels for ozone to protect vegetation

Institute for Plant Ecology, University of Giessen, Heinrich-Buff-Ring 26-32, D-35392 Giessen, Germany.
Environmental Pollution (Impact Factor: 4.14). 02/2001; 111(3):355-62. DOI: 10.1016/S0269-7491(00)00181-0
Source: PubMed

ABSTRACT

The current European critical levels for ozone (O3) to protect crops, natural and semi-natural vegetation and forest trees are based on a relative small number of open-top chamber experiments with a very limited number of plant species. Therefore, the working group "Effects of Ozone on Plants" of the Commission on Air Pollution Prevention of the Association of German Engineers and the German Institute of Standardization reanalysed the literature on O3 effects on European plant species published between 1989 and 1999. An exposure-response relationship for wild plant species and agricultural crops could be derived from 30 experiments with more than 30 species and 90 data points; the relationship for conifer and deciduous trees is based on 20 experiments with nine species and 50 data points. From these relationships maximum O3 concentrations for different risk stages are deduced, below which the vegetation type is protected on the basis of the respective criteria. Because it is assumed that the fumigation concentrations reflect the O3 concentrations at the top of the canopy, i.e. the upper surface boundary of the quasi-laminar layer if the micrometeorological big-leaf approach is applied, the application of these maximum O3 concentrations requires the transformation of O3 concentrations measured at a reference height above the canopy to the effective phytotoxic concentrations at the top of the canopy. Thus, the approach described in this paper is a synthesis of the classical concept of toxicology of air pollutants (critical concentrations) and the more toxicological relevant dose concept.

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Available from: Ludger Grünhage, Aug 11, 2015
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    • "Ozone-and drought-induced loss of stomatal function may enhance both leaf water loss and O 3 uptake. Current modeling efforts of O 3 effects on plants have been developed using steadystate parameters (Emberson et al., 2000; Grünhage et al., 2001) and the O 3 -induced losing control of dynamic stomatal response was ignored. The results presented here suggest to reconsider the role of O 3 pollution on leaf gas exchange and highlight complex interactions between ozone and drought. "
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    ABSTRACT: We tested whether short-term exposure to realistic ozone pollution (≤150 ppb, 1 h) and soil water stress (soil water content ≤15%) slow stomatal dynamics in an ozone-sensitive cultivar of snapbean. Both ozone exposure and water stress caused stomata to be sluggish in the degree of closure after leaf severing, while ozone also delayed the time the closing signal was perceived. Ozone-induced aberrations lasted up to the night and caused incomplete closure of stomata. No synergic effect was observed in the dynamic measurements. In contrast, at steady-state, water stress protected the plants from the negative ozone effects on stomatal conductance. Ambient ozone peaks may thus cause sluggish stomatal response and increase leaf water loss both under well watered and drought conditions.
    Full-text · Article · Apr 2013 · Environmental and Experimental Botany
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    • "2.4) sowie bei der Beurteilung der daraus resultierenden Ergebnisse verwendet. 2.2 Berechnung der maximal zulässigen Ozonkonzentration (MPOC) Das MPOC-Konzept (Grünhage et al. 2001; VDI 2002; Krause et al. 2003) ist ein empirisches, expositionsbasiertes Modell, das aus stündlichen Ozonkonzentrationen eine Worst-case-Belastungssituation für Waldbäume ableitet . Die relative Risikobewertung für einen Bestand er- Tabelle 2 Standortscharakterisierung der kombinierten Flächenpaare, klimatische Verhältnisse und Ozonregime für die Jahre 2002 und 2003 Flächenpaar BA WG BT BS BD nFk ND2002 ND2003 TI2002 TI2003 O 3 2002 O 3 2003 as-ROT Ei/Bu 2 BB Ls f n – 258 1,00 0,90 25 ± 21 97 32 ± 26 134 – 672 wb-WUE Ei 4 LL-DD Tu f-m n 411 873 200 415 1,00 0,74 29 ± 19 89 39 ± 23 122 ns-RIE Ei 6 sw ss LL ü CF Tu f-m m 442 262 0,98 0,87 35 ± 20 99 42 ± 21 117 904 455 me-AOE Fi 13 sw pp LL Lt f n-m 598 352 1,00 0,77 32 ± 18 92 38 ± 21 100 1113 685 KF-FRE Bu 12 LL/BB Lu f-m n-m 558 304 1,00 0,83 34 ± 17 90 46 ± 20 106 Bu 12 1015 558 ab-ZUS Fi 12 BB-SS Ut f-m m 709 403 9,99 0,53 35 ± 20 93 41 ± 24 113 1274 721 re-BOD Ki 9 sw pp BB St m-g n 424 238 0,99 0,90 28 ± 19 36 ± 22 957 477 90 109 na-ROK Fi 8 sw pp BB Lt f m 384 294 1,00 0,88 31 ± 20 39 ± 23 1294 882 89 113 ga-SOG Fi 15 LL Lt f n-m 781 541 1,00 1,00 31 ± 16 41 ± 19 Bu 13 1043 990 86 96 tb-FLO 10 BB-PP Sl f n-m 636 268 1,00 0,85 45 ± 14 52 ± 16 Fi 10 1236 512 89 114 FB-MIT Bu/Fi 11 BB Ls f m 898 349 1,00 1,00 41 ± 12 50 ± 13 Bu 11 pp BB 2552 1007 85 107 hp-KRE Fi 14 BB-H.GG Lt f m 1203 773 1,00 1,00 42 ± 12 51 ± 14 Fi 15 2126 1478 91 95 gw-BER Fi 15 L.RR Ls g m-h 1220 856 1,00 1,00 56 ± 13 96 64 ± 14 111 Lä 15 2016 1536 BA: Baumart (Hauptbaumart an Waldklimastation), WG: Forstliche Wuchsgebietsgliederung (nach Gulder 2001), BT: Bodentyp (nach Bodenkundliche Kartieranleitung 2005), BS: Bodensubstrat, nFk: nutzbare Feldkapazität bis ca. "
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    ABSTRACT: Background, aim, and scope Increasing background concentrations of ground-level tropospheric ozone and more frequent and prolonged summer drought incidences due to climate change are supposed to increase the stress on Bavarian forests. For such scenarios growth reduction and yield losses are predicted. Sustainable forest management in Bavaria aims to significantly increase the proportion of beech (Fagus sylvatica L.) because of its broad ecological amplitude. In our regional study different approaches for calculating ozone impact were used to estimate the risks for Bavarian forests in the average climatic, rather moist year 2002 and the extremely dry year 2003. Materials and methods Measurements were conducted for eleven forest ecosystem sites and two forest research sites representing typical Bavarian forest stands under different climatic conditions and situated in different altitudes. For risk assessment currently used approaches were applied either based on the calculation of the cumulative ozone exposure (external dose; MPOC maximal permitted ozone concentration; critical level AOT40phen‚ accumulated ozone exposure over a threshold of 40 nl [O3] l–1, for the effective phenolgy of beech) or based on the calculation of the phytomedically relevant ozone flux into the stomata (internal dose, critical level AFst>1,6, accumulated stomatal flux above a flux threshold of 1.6 nmol O3 m–2 PLA; PLA = projected leaf area). For calculations continuously recorded ozone concentrations and meteorological and phenological data from nearby rural open field background measuring stations from the national air pollution control and from forested sites were used. Additionally ozone induced leaf symptoms were assessed. Results The exposure-based indices AOT40phen and MPOC as well as the flux-based index AFst>1.6 suggest that Bavarian forests are at risk from O3 during a rather moist average year concerning climate conditions (2002) as well as in an extreme dry year (2003). Thus, growth reductions of 5 % are predicted when thresholds are exceeded. Threshold exceedance occurred in both years at all plots, mostly already at the beginning of the growing season and often even many times over. Ozone induced leaf symptoms could be detected only on a few plots in a very slight occurrence. Discussion The results for the applied critical level indices differed depending on climatic conditions during the growing seasons: Regarding exposure-based indices, the highest degree of threshold exceedance occurred in the dry year of 2003 at all plots; the flux-based approach indicated the highest stomatal ozone uptake and thus an increased risk at moist sites or during humid years, whereas the risk was decreasing at dry sites with prolonged water limitation. Hence, soil and accordingly plant water availability was the decisive factor for the flux-modelled internal ozone uptake via stomata. Drought and increased ozone impact can generate synergistic, but also antagonistic effects for forest trees. At water limited rather dry forest sites restricted transpiration and thus production, but concurrently lower ozone uptake and reduced risk for damage can be expected. Conclusions, recommendations, and perspectives For realistic site-specific risk assessment in forest stands the determination of the internal ozone dose via modeling flux based internal stomatal ozone uptake is more appropriate than the calculation of the external ozone dose. The predicted 5 % growth reductions are in discrepancy with the frequently observed increment increase during the last decades in forest stands. Comprehensive and significant statistical verification for ozone induced forest growth reduction as well as the systematic validation of thresholds for ozone in the field is still lacking. However, a multiplicity of different specific new and retrospective growth analysis data should allow closing the gap. Moreover, the determination of canopy transpiration with sap flow measurements is a novel approach to provide cause-effect related, site specific results for the effective internal ozone dose as well as for canopy water supply and consecutively for regional risk estimation. A further future objective is the refinement of O3 flux modelling by further consideration of soil/water budget characteristics and the above mentioned improved estimations of crown and canopy transpiration. Further, the introduction of threshold ranges for forest trees in view of their specific regional climatic conditions and their validation in real forest stands is necessary for developing meaningful ozone risk predictions for forests.
    Full-text · Article · Oct 2010 · Umweltwissenschaften und Schadstoff-Forschung
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    • "Estimation of ozone dose is based on the stomatal flux approach, which takes into account the stomatal conductance of the vegetation. A clear understanding of stomatal conductance behaviours, in relation to different environmental conditions (especially in relation to water availability) becomes essential to quantify the amount of ozone effectively absorbed by plants (Grü nhage et al., 2001). "
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    ABSTRACT: Stomatal ozone uptake, determined with the Jarvis' approach, was related to photosynthetic efficiency assessed by chlorophyll fluorescence and reflectance measurements in open-top chamber experiments on Phaseolus vulgaris. The effects of O(3) exposure were also evaluated in terms of visible and microscopical leaf injury and plant productivity. Results showed that microscopical leaf symptoms, assessed as cell death and H(2)O(2) accumulation, preceded by 3-4 days the appearance of visible symptoms. An effective dose of ozone stomatal flux for visible leaf damages was found around 1.33 mmol O(3) m(-2). Significant linear dose-response relationships were obtained between accumulated fluxes and optical indices (PRI, NDI, DeltaF/F'(m)). The negative effects on photosynthesis reduced plant productivity, affecting the number of pods and seeds, but not seed weight. These results, besides contributing to the development of a flux-based ozone risk assessment for crops in Europe, highlight the potentiality of reflectance measurements for the early detection of ozone stress.
    Full-text · Article · May 2009 · Environmental Pollution
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