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Ecosystem-scale trade-offs between impacts of ozone and reactive nitrogen Ed Rowe, Felicity Hayes, Kasia Sawicka, Gina Mills, Laurence Jones, Filip Moldan, Sereina Bassin, Netty van Dijk & Chris Evans EGU, Vienna, 13th April 2015

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Nitrogen is an acidifying pollutant Giant Mountains, Czech Republic, 2005 UK NO x emissions UK NH 3 emissions RoTAP report, CEH, 2012 Temporal deposition sequence from GANE project (Fowler et al 2004 WASP:Focus 4: 9-23) UK SO 2 emissions Many systems are recovering from acid rain But reductions in reactive-nitrogen (NO x, NH y ) emissions have been small, compared to reductions in S emissions

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Nitrogen is also a fertiliser End of the fertiliser bag, Mutare, Zimbabwe, 2002 Ammonium nitrate delivery, Gwynedd, UK, 2006 Current Legislated [N] Emissions Maximum Feasible [N] Reduction de Vries & Posch (2011) Env Poll 159: 2289-2299 Additional European C sequestration due to N pollution

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not good for species that need ground-level light Hodgson et al. (2014) Functional Ecology 28: 1284-1291. more N --> increasing productivity ground-level shade litterfall Drosera rotundifolia Urtica dioica Lotus corniculatus

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N deposition reduces species-richness Acid grassland, UK Heathland, UK Stevens et al. (2004) Science 303: 1876-1879 Maskell et al. (2010) Global Change Biol.16: 671679 kg N ha -1 y -1 Number of species 0 5 30 40 0 45 Number of species

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Global reactive-N deposition Dentener et al. 2006 Global Biogeochem Cycles 20: GB4003 mg N m -2 yr -1 For terrestrial ecosystems, land-use change probably will have the largest effect [on biodiversity], followed by climate change, nitrogen deposition, biotic exchange, and elevated carbon dioxide concentration. Sala et al 2000, Science 287: 1770-1774 kg N ha -1 yr -1 60 20 5 1 0.1

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Predicting effects of N and S (MADOC) N14C: Tipping et al. 2012 Ecological Modelling 247:11-26 VSD: Posch & Reinds 2009 Env Modelling and Software 24: 329-340 DyDOC: Michalzik et al. 2003 Biogeochemistry 66, 241-264 N14C: vegetation growth and soil organic matter development VSD: cation exchange and pH DyDOC: dissolution of organic matter MADOC: dynamic integration, allowing feedback between pH and DOC

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MADOC passes some plausibility tests Rowe et al. 2014 Environmental Pollution 184, 271-282. Calibration dataset (EHFI acidification / alkalisation experiment) Independent dataset (Acid Waters Monitoring Network sites)

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Predicting effects on plant species and biodiversity Floristic response MultiMOVE Vegetation and soil biogeochemistry MADOC Total N deposition Indicators of environmental conditions e.g. pH, mineral N, light Habitat suitability for individual species Other drivers Biogeochemistry Plant ecology Quantity Model Key: Other drivers Rhynchospora alba Smart et al. 2010 J Veg Sci 21: 643:656 Henrys et al. New J Bot in prep.

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Summarising effects on biodiversity Rowe et al. (submitted) Ecological Indicators

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How will ozone pollution interact? Ozone in the stratosphere protects the planet from ultraviolet radiation but tropospheric i.e. ground-level ozone is a problem. Formed in reactions involving nitrogen oxides and Volatile Organic Compounds European NO x and VOC emissions controls decreasing peak concentrations Hemispheric transport increasing background concentrations Effects on human health Damage to plants increasing crop losses Photo: Gina Mills Tropospheric ozone formation diagram: http://keutsch.chem.wisc.edu/

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Ozone effects supported by evidence 1.Decreasing plant productivity (NPP) at greater ozone concs. reduced productivity, reduced carbon inputs 2.Reduced translocation of N out of senescing leaves at greater ozone concs. more potential for N loss e.g. leaching, N 2 O

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Ozone effects added into MADOC 1.Reduction in NPP with increasing ozone concentration

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Ozone effects added into MADOC 2. Reduced translocation of N out of senescing leaves with increasing ozone conc.

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Sites simulated LlynBrianne Montseny Alpflix Brandbjerg Whim Grizedale Sourhope Grdsjn Clocaenog Kiskunsag Klausen Oldebroek Sites modelled in ECLAIRE

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Responses to N treatments Whim Moss Scotland heath exposed to dry NH 3 or wet NaNO 3 or wet NH 4 Cl Symbols = Modelled Lines = observed

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Responses to N treatments Grdsjn Sweden coniferous forest subcatchments Treatments: Control; +40 kg N ha -1 yr -1 (wet NH 4 NO 3 ) Symbols = Modelled Lines = observed

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Responses to N x O 3 treatments AlpFlix Switzerland Alpine grassland, extremely low N deposition, but chronically exposed to ozone Experimental responses (circles): Strong productivity response to N No significant productivity response to ozone Bassin et al (2007) New Phytologist 175, 523-534. Modelled responses (lines): responses to N and ozone negative interaction (ozone limits response to N, and vice versa) Symbols = Modelled Lines = observed

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Sensitivity of productivity to N and Ozone i.e. ozone reduces plant productivity by a greater proportion at greater N deposition Could it be said that ozone pollution moderates the effects of N pollution?

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Direct ozone effects on biodiversity Hayes et al. (unpublished) Effect of ozone exposure on cover of Campanula rotundifolia in calcareous grassland

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Conclusions We need more ecosystem-level experiments on N-ozone interactions Simulations are the best available basis for assessing ecosystem effects of O 3 and N N is likely to increase productivity benefits for agriculture and forestry, C storage disbenefits for biodiversity Ozone is likely to decrease productivity benefits for biodiversity? likely to be outweighed by direct adverse effects of O 3 N and ozone together are likely to increase soil N cycling rates disbenefits due to N leaching and NOx emissions Acknowledgements This work was funded by the UK Government (Defra) and by the European Union (FP7 ECLAIRE project)