Management impacts on the C balance in agricultural ecosystems

1. CarboEurope, Poznan meeting, October 9, 2007. Management impacts on the C balancein agricultural ecosystems Jean-François Soussana1 Martin Wattenbach2, Pete Smith2 1. INRA, Clermont-Ferrand, France 2. Aberdeen University, Scotland, UK

2. Uncertainties in the carbon balance of European ecosystems before the start of CarboEurope (Janssens et al. Science, 2003). Source Sink Geographic Europe Fossil fuel emissions = 1850 Mt C per year

3. Components of the agricultural C budget NBP: Net Biome Productivity, Soil C balance NEE: Net Ecosystem Exchange, Atmospheric C balance

4. 28sites Main Grass. Main Wet. Anc. Grass. Anc. Wet. CarboEurope IP grasslands & wetlands sites

5. Climate drivers of grassland and wetland annual GPP at CarboEurope IP sites Log(GPP) = 2.27 + 0.377. Log (Temp) + 0.614. Log (Precip) (n=50, r2=0.705, P<0.0001)

6. Rhetero. Herbivore 46 Rhetero. SOM 89 Rhetero. Litter 294 GPP 1228 Rauto. 615 K3 = 83 Q10 =1.21 K1=0.50 K2=0.43 Digest.=0.65 NBP 128 Intake 70 Enteric fermentation 3.4 Cut 75 Manure 16 Mean C fluxes (gC m-2 yr-1) at CarboEurope grassland and wetland sites NBP = K2 (K1 GPP – Cut – Digest . Intake + Manure)– K3 e LN(Q10).Tsoil/10 –FCH4-C (n=43, R2=0.52, P<0.001)

7. Fate of NPP and manure (at C sink sites) Cut Cut & Grazed Grazed Abandoned & Wet

8. Current herbage utilisation is lower than maximum

9. Role of cutting and grazing management for NBP Maximal grazing Maximal cutting Trade-off between C sequestration and agricultural (livestock) production

10. Grassland GPP over Europe Data upscaling with annual means of temperature and precipitation PASIM model (Vuichard et al., 2007 GBC)

11. Spatial distribution of NBP of grasslands in Europe (data upscaling) Assuming a management similar to mean site management NEXT STEP: map NBP using agricultural management based on statistics

12. C sequestration efficiency in grasslands (data upscaling) Assuming a management similar to mean site management NEXT STEP: map NBP/GPP using agricultural management based on statistics

13. How large is the grassland C sink? • First estimate, which needs to be refined: • DOC/DIC losses up to 8 % of NBP • On site N2O and CH4 emissions reach ca. 30 % of NBP • Indirect N2O and CH4 emissions, reach ca 15 % of NBP

14. CarboEurope-IP Cropland sites http://www.abdn.ac.uk/modelling/cropwebpage/cropwebpage4IE.htm

15. Variability between years and under different crops (Gruenwald, pers. comm. to Christine Moureaux)

16. Using models to interpret EC data from croplands

17. Using models to interpret EC data from croplands Analysis by Mike Williams

18. What are the uncertainties associated with the simulation of cropland ecosystems at site level ? Output distribution Monte Carlo – multi model run Input distribution DNDC* model The discrepancy between simulated mean value from the Monte Carlo runs and the annual value obtained from a single run using the best estimates. suggest that using the best estimate may not lead to the most probable model result. * DeNitrification-DeComposition model

19. Are croplands as big a source of C as we thought?

20. Looking to the future…more work on organic soils Organic soil restoration vs. mineral soil sequestration Data from: Smith et al. (2007a)

21. Change in cropland SOC – climate&NPP&technology Climate only J.U. Smith et al. (2005)

22. Change in cropland SOC – climate&NPP&technology Climate&NPP&technology J.U. Smith et al. (2005)

23. Some potential for agricultural GHG mitigation in Europe Management impacts on cropland C balance – climate mitigation Smith et al. (2007a)

24. Conclusions • Synthesis papers are being written for each landuse type • Plans for whole agricultural sector. Same methodology for both land uses. • Need to account better for actual agricultural management over Europe. • Major challenges • Interannual variability and climate change • Continental upscaling • Organic soils • Non CO2 GHG emissions • Interactions with mitigation and adaptation