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

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

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: Additional European C sequestration due to N pollution

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

N deposition reduces species-richness Acid grassland, UK Heathland, UK Stevens et al. (2004) Science 303: Maskell et al. (2010) Global Change Biol.16: 671–679 kg N ha -1 y -1 Number of species Number of species

Global reactive-N deposition Dentener et al 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: kg N ha -1 yr

Predicting effects of N and S (MADOC) N14C: Tipping et al Ecological Modelling 247:11-26 VSD: Posch & Reinds 2009 Env Modelling and Software 24: DyDOC: Michalzik et al Biogeochemistry 66, 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

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

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 J Veg Sci 21: 643:656 Henrys et al. New J Bot in prep.

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

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:

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

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

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

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

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

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

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, Modelled responses (lines): responses to N and ozone negative interaction (ozone limits response to N, and vice versa) Symbols = Modelled Lines = observed

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?

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 (unpublished) Effect of ozone exposure on cover of Campanula rotundifolia in calcareous grassland

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)