1. 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

2. 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

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

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

5. 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 + 0.1 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

6. 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

7. 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

8. Results & discussion 57 N 2 O long-term emission measurements N deposition induces significant N 2 O emissions; confirmed by Machefert et al. 2002 and Skiba et al. 2012 TFEIP, Milano, 11 May 20158 Bühlmann et al. 2015

9. Results & discussion TFEIP, Milano, 11 May 20159 16 NO long-term emission measurements Bühlmann et al. 2015

10. Results & discussion Emission rates differ between (semi-)natural ecosystems (Bühlmann et al. 2015; Groffman et al. 2000) TFEIP, Milano, 11 May 201510 de.wikipedia.org N2ON2O NO N2ON2O

11. Results & discussion TFEIP, Milano, 11 May 201511 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 %

12. 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 201512

13. Results & discussion Indirect N 2 O emissions of (semi-)natural ecosystems TFEIP, Milano, 11 May 201513 Bühlmann et al. 2015

14. Results & discussion Indirect NO emissions of (semi-)natural ecosystems TFEIP, Milano, 11 May 201514 Bühlmann et al. 2015

15. 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 2010 21 % of the total N 2 O emission were emitted from (semi-)natural ecosystems TFEIP, Milano, 11 May 201515 N 2 O (Gg N) This study N 2 O (Gg N) IPCC (modified) N 2 O (Gg N) Kesik et al. 2005 Forests 1.45 ± 0.400.180.75 Grass- and wetlands 0.24 ± 0.040.03- total 1.69 ± 0.340.21-

16. 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 2010 10 % of the total NO x emission were emitted from (semi-)natural ecosystems TFEIP, Milano, 11 May 201516 NO (Gg N) This study NO (Gg N) EMEP/EAA NO (Gg N) Kesik et al. 2005 Forests 2.56 ± 0.640.060.58 Grass- and wetlands 0.03 ± 0.040.03- total 2.61 ± 0.550.09-

17. 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 201517

18. Acknowledgements University of Basel – Erika Hiltbrunner, Christian Körner FOEN – Beat Achermann, Richard Ballaman, Martin Schiess, Simon Liechti Meteotest – Beat Rihm TFEIP, Milano, 11 May 201518

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20. 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 201520

21. 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 201521

22. 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 0.543 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 201522