Atmospheric nitrogen deposition causes indirect NO and N 2 O emissions in (semi-)natural ecosystems Tobias Bühlmann (University of Basel) Beat Achermann (FOEN) Simon Liechti (FOEN) Beat Rihm (Meteotest) Erika Hiltbrunner (University of Basel) Christian Körner (University of Basel) TFEIP, Milano, 11 May 2015

Indirect N 2 O and N emissions (Semi-)natural ecosystems are used extensively only or not at all; no net N input besides atmospheric N deposition TFEIP, Milano, 11 May 20152

Total atmospheric N deposition (wet + dry) 2010 TFEIP, Milano, 11 May 20153

Exceedance of CLN Correlation between atmospheric N deposition and NO/N 2 O emission (Butterbach et al. 1998) TFEIP, Milano, 11 May 20154

Today’s methods Indirect N 2 O emissions (Guidelines for National Greenhouse Gas Inventories 2006, IPCC) – N 2 O-N = (NH 3 -N + NO x -N emissions) x EF 4 EF 4 = 1% Indirect NO emissions (Emission Inventory Guidebook 2013, EMEP/EEA) – Simpler methodology (Skiba et al. 1997) NO = N input x EF NOx ng NO-N m -2 s -1 – EF NOx = 0.3% – Detailed methodology (Novak and Pierce 1993) Not suitable for annual emissions Attention: EF 4 and EF NOx are based on agriculture data only TFEIP, Milano, 11 May 20155

Methods Aim: Calculate indirect NO and N 2 O emissions of Swiss (semi-)natural ecosystems – EMEP/EEA and IPCC compatibility: “Activity x EF” TFEIP, Milano, 11 May 20156

Methods Literature research – Studies measuring NO or N 2 O emission in (semi-)natural ecosystems Total N deposition known (measured or modelled) Similar climatic conditions as Switzerland Long time measurements No fertilizer, no N 2 -fixing plants N deposition dependent emission rates  SWC, soil pH, soil temperature etc. could not be involved in analyses TFEIP, Milano, 11 May 20157

Results & discussion 57 N 2 O long-term emission measurements N deposition induces significant N 2 O emissions; confirmed by Machefert et al and Skiba et al TFEIP, Milano, 11 May Bühlmann et al. 2015

Results & discussion TFEIP, Milano, 11 May NO long-term emission measurements Bühlmann et al. 2015

Results & discussion Emission rates differ between (semi-)natural ecosystems (Bühlmann et al. 2015; Groffman et al. 2000) TFEIP, Milano, 11 May de.wikipedia.org N2ON2O NO N2ON2O

Results & discussion TFEIP, Milano, 11 May Stehfest and Bouwman 2006 N input EF N2O-N : 0.9 % EF NO-N : 0.6 % N input EF N2O-N : 3.7 % EF NO-N : 12.5 %

Application Calculation of ecosystem specific indirect NO and N 2 O emissions – Indirect N emission = N deposition x emission rate – Ecosystem specific emission rate (this study) Ecosystem type: Land Use Statistics, WMG-100 – 100 m resolution – N deposition (Meteotest) 100 m resolution, for the years 1990, 2000, 2007, 2010 TFEIP, Milano, 11 May

Results & discussion Indirect N 2 O emissions of (semi-)natural ecosystems TFEIP, Milano, 11 May Bühlmann et al. 2015

Results & discussion Indirect NO emissions of (semi-)natural ecosystems TFEIP, Milano, 11 May Bühlmann et al. 2015

Results & discussion Indirect N 2 O emissions of (semi-)natural ecosystems for the year 2000 IPCC approach underestimates N 2 O emissions of (semi-) natural ecosystems in Switzerland In % of the total N 2 O emission were emitted from (semi-)natural ecosystems TFEIP, Milano, 11 May N 2 O (Gg N) This study N 2 O (Gg N) IPCC (modified) N 2 O (Gg N) Kesik et al Forests 1.45 ± Grass- and wetlands 0.24 ± total 1.69 ±

Results & discussion Indirect NO emissions of (semi-)natural ecosystems for the year 2000 EMEP/EEA approach underestimates NO x emissions of (semi-) natural ecosystems in Switzerland In % of the total NO x emission were emitted from (semi-)natural ecosystems TFEIP, Milano, 11 May NO (Gg N) This study NO (Gg N) EMEP/EAA NO (Gg N) Kesik et al Forests 2.56 ± Grass- and wetlands 0.03 ± total 2.61 ±

Conclusion Indirect N 2 O and NO emissions from (semi-)natural ecosystems are substantial. EFs for indirect N emissions differ between ecosystems. – EFs for agricultural land are unsuitable for (semi-)natural ecosystems. Indirect N 2 O and NO emissions of (semi-)natural ecosystems are currently underestimated by the international approaches. – High uncertainty for NO emissions. TFEIP, Milano, 11 May

Acknowledgements University of Basel – Erika Hiltbrunner, Christian Körner FOEN – Beat Achermann, Richard Ballaman, Martin Schiess, Simon Liechti Meteotest – Beat Rihm TFEIP, Milano, 11 May

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Application in emission inventories indEmis total = indEmis (semi-)nat. ecosystems + indEmis rest N deposition missing in emission inventories – Relate indirect emissions of (semi-)natural ecosystems to the sum of direct NO x -N and NH 3 -N emissions  Ef emis Switzerland – Indirect N 2 O emissions are calculated for direct emissions of agriculture only. TFEIP, Milano, 11 May

Application of results: NO Indirect NO emissions NO ind. = NO ind. nat. ecosystems + NO ind. rest = Activity x EF nat. Ecosystems + activity x EF NOx = Activity x (EF nat. Ecosystems + EF NOx ) Activity = sum of national NO x -N and NH 3 -N emissions EF nat. ecosystems = (NO-N nat. ecosystems )/(sum of national NO x -N and NH 3 -N emissions) – Available for the years 1990, 2000, 2007, 2010 – Only valid for Switzerland! EF NOx = (NO-N rest )/(sum of national NO x -N and NH 3 -N emissions) TFEIP, Milano, 11 May

Application of results: N 2 O Indirect N 2 O emissions N 2 O ind. = N 2 O ind. nat. ecosystems + N 2 O ind. rest = Activity x EF nat. Ecosystems + activity x EF 4 x Activity = sum of national NO x -N and NH 3 -N emissions EF nat. ecosystems = (N 2 O-N nat. ecosystems )/(sum of national NO x -N and NH 3 -N emissions) – Available for the years 1990, 2000, 2007, 2010 – Only valid for Switzerland! EF 4 = 0.01 TFEIP, Milano, 11 May