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GHG Emissions in Southeastern Amazonia: The Effect of Agricultural Intensification

AAG 2015 conference presentation

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GHG Emissions in Southeastern Amazonia: The Effect of Agricultural Intensification

  1. 1. GHG Emissions in Southeastern Amazonia: The Effect of Agricultural Intensification Christine O’Connell, Paulo Brando, Carlos Eduardo Cerri, Michael Coe, Eric Davidson, Gillian Galford, Marcia Macedo, Chris Neill, Rodney Venterea AAG 2015 22 April 2015
  2. 2. Q What are the impacts of intensifying agriculture in Amazonia on greenhouse gas emissions?
  3. 3. ~20% of Amazonia is deforested, largely for agricultural export commodities Hansen et al. (2013), Nepstad et al. (2014)
  4. 4. Southeastern Amazonia is rapidly transitioning to a novel form of industrial, highly managed tropical agriculture DeFries et al. (2014), Spera et al. (2014)
  5. 5. Tanguro Ranch: Land use change impacts case study
  6. 6. Tanguro Ranch: Land use change impacts case study
  7. 7. Tanguro Ranch: Land use change impacts case study
  8. 8. Tanguro Ranch: Land use change impacts case study
  9. 9. Tanguro Ranch: Land use change impacts case study
  10. 10. Tanguro Ranch: Land use change impacts case study
  11. 11. Tanguro Ranch: Land use change impacts case study
  12. 12. Tanguro Ranch has three land uses: transitional Amazon forest (F), soybean cultivation (S), and soybean/maize (double cropped) cultivation (M). MAT: 27°C MAP: 1800 mm/y Management: N- (x2, M only) and P-fertilizer (x2), lime, pesticide, herbicide Soils: ~40% clay; pH 4.5 (F), 5.5-6 (S, M)
  13. 13. Field measurement of N pools and GHG fluxes
  14. 14. N2O or nitrous oxide, a greenhouse gas with 300 times the warming potential of CO2, may be an important N loss pathway. CO2 emissions we expect to fall in cropland because deforestation can deplete soil C CH4 emissions are often negative in tropical forests, with drier cropland soils perhaps lowering uptake rates
  15. 15. Forest (F) Soybean (S) Soybean/Maize (M) Dry season N2O emissions are uniformly near zero (~0-0.5 ngN/cm2/h). Surprisingly, wet season emissions remain low as well, between 1-4 ngN/cm2/h. Post- fertilization spikes increase by an order of magnitude. S MF
  16. 16. S MF F S MCH4FluxCO2FluxN2OFlux CO2 cropland wet season fluxes were much larger than hypothesized. CH4 emissions in forests had strong heterogeneity within site.
  17. 17. While post-fertilization N2O peaks can be substantial, in several cases they barely deviated from the baseline.
  18. 18. Are these differences in fertilization response between sites driven by soil moisture? Initial results suggest not. S MF
  19. 19. What about row / inter-row heterogeneity? N2O emissions are highest between rows in M; CO2 emissions are highest on the row in S. Forest Inter-row Row F M S F M S F M S
  20. 20. Inter-row Row Inter-row Row S MF When accounting for row / inter-row, soil moisture seems to play a role: inter-row N2O emissions in M correlate with moisture. But available N may be a better predictor…
  21. 21. N2O is a surprisingly limited loss rate of nitrogen (gaseous loss as non-GHG or soil adsorption?) CO2 rise in cropland in the wet season, likely driven by high productivity CH4 becomes a less variable carbon loss pathway after deforestation and cultivation
  22. 22. Spera et al. (2014) 2001 2011 Scaling field results to the regional level will help constrain uncertainty surrounding N cycle consequences of this novel land use
  23. 23. Relying on key terrestrial ecosystems for agriculture and development will inherently have ecological consequences Determining how to balance these tradeoffs will require continued science with an eye on whole- ecosystem impacts – and on scale So… Agricultural Amazonia?
  24. 24. Thanks very much Photo credits Flickr CC Users CIFOR Billtacular Jacsonquerubin flinner! Carine06 LeoFFreitas terrydu ggallice Icelight MODIS images via NASA Obrigada toThe Foley, Polasky, Powers and Hobbie lab groups Unending thanks to the fantastic IPAM field team and Chelsea Nagy Supporting agencies, institutions and collaborators below, especially IPAM and the Woods Hole Research Center Amazon group Friends and family Christine S. O’Connell, coconn@umn.edu, UMN EEB/IonE
  25. 25. We are limited by ideas, not by tools - Peter Groffman

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