title: Developing ozone critical levels for multi-species canopies of Mediterranean annual pastures.
abstract: Ozone (O3) critical levels (CLe) are still poorly developed for herbaceous vegetation. They are currently based on single species responses which do not reflect the multi-species nature of semi-natural vegetation communities. Also, the potential effects of other factors like the nitrogen (N) input are not considered in their derivation, making their use uncertain under natural conditions. Exposure- and dose-response relationships were derived from two open-top chamber experiments exposing a mixture of 6 representative annual Mediterranean pasture species growing in natural soil to 4 O3fumigation levels and 3 N inputs. The Deposition of O3and Stomatal Exchange model (DO3SE) was modified to account for the multi-species nature of the canopy following a big-leaf approach. This new approach was used for estimating a multi-species phytotoxic O3dose (PODy-MS). Response relationships were derived based on O3exposure (AOT40) and flux (PODy-MS) indices. The treatment effects were similar in the two seasons: O3reduced the aboveground biomass growth and N modulated this response. Gas exchange rates presented a high inter-specific variability and important inter-annual fluctuations as a result of varying growing conditions during the two years. The AOT40-based relationships were not statistically significant except when the highest N input was considered alone. In contrast, PODy-MSrelationships were all significant but for the lowest N input level. The influence of the N input on the exposure- and dose-response relationships implies that N can modify the O3CLe. However, this is an aspect that has not been considered so far in the methodologies for establishing O3CLe. Averaging across N input levels, a multi-species O3CLe (CLef-MS) is proposed POD1-MS= 7.9 mmol m-2, accumulated over 1.5 month with a 95% confidence interval of (5.9, 9.8). Further efforts will be needed for comparing the CLef-MSwith current O3CLefbased on single species responses.
authors.affiliation: Ecotoxicology of Air Pollutants CIEMAT (Ed.70), Avda. Complutense 40, 28040, Madrid, Spain. Electronic address: hector.calvete@ciemat.es.
authors.forename: H
authors.initials: H
authors.lastname: Calvete-Sogo
authors.affiliation: Ecotoxicology of Air Pollutants CIEMAT (Ed.70), Avda. Complutense 40, 28040, Madrid, Spain. Electronic address: ignacio.gonzalez@ciemat.es.
authors.forename: I
authors.initials: I
authors.lastname: González-Fernández
authors.affiliation: Ecotoxicology of Air Pollutants CIEMAT (Ed.70), Avda. Complutense 40, 28040, Madrid, Spain. Electronic address: hector.garcia@ciemat.es.
authors.forename: H
authors.initials: H
authors.lastname: García-Gómez
authors.affiliation: Ecotoxicology of Air Pollutants CIEMAT (Ed.70), Avda. Complutense 40, 28040, Madrid, Spain. Electronic address: rocio.alonso@ciemat.es.
authors.forename: R
authors.initials: R
authors.lastname: Alonso
authors.affiliation: Ecotoxicology of Air Pollutants CIEMAT (Ed.70), Avda. Complutense 40, 28040, Madrid, Spain. Electronic address: susana.elvira@ciemat.es.
authors.forename: S
authors.initials: S
authors.lastname: Elvira
authors.affiliation: Ecotoxicology of Air Pollutants CIEMAT (Ed.70), Avda. Complutense 40, 28040, Madrid, Spain. Electronic address: j.sanz@ciemat.es.
authors.forename: J
authors.initials: J
authors.lastname: Sanz
authors.affiliation: Ecotoxicology of Air Pollutants CIEMAT (Ed.70), Avda. Complutense 40, 28040, Madrid, Spain. Electronic address: victoria.bermejo@ciemat.es.
authors.forename: V
authors.initials: V
authors.lastname: Bermejo-Bermejo
mesh_terms: D000383:Agriculture; D000393:Air Pollutants / Q000032:analysis* / Q000592:standards / Q000633:toxicity; D018533:Biomass; D004784:Environmental Monitoring / Q000379:methods* / Q000592:standards; D065928:Forests; D019083:Mediterranean Region; D008962:Models, Theoretical; D009584:Nitrogen; D010126:Ozone / Q000032:analysis* / Q000592:standards / Q000633:toxicity; D018515:Plant Leaves / Q000737:chemistry; D012621:Seasons
chemical_list: D000393:Air Pollutants; D010126:Ozone; D009584:Nitrogen
keywords: AOT40; Dehesa pasture; Ozone and nitrogen interaction; Phytotoxic ozone dose; Stomatal conductance