AAG 2015 conference presentation

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. Q
What are the impacts
of intensifying
agriculture in Amazonia
on greenhouse gas
emissions?

3. ~20% of Amazonia is
deforested, largely for
agricultural export commodities
Hansen et al. (2013), Nepstad et al. (2014)

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. Tanguro Ranch: Land use change impacts case study

6. Tanguro Ranch: Land use change impacts case study

7. Tanguro Ranch: Land use change impacts case study

8. Tanguro Ranch: Land use change impacts case study

9. Tanguro Ranch: Land use change impacts case study

10. Tanguro Ranch: Land use change impacts case study

11. Tanguro Ranch: Land use change impacts case study

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. Field measurement of N pools and GHG fluxes

15. 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

16. 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

17. S MF
F S MCH4FluxCO2FluxN2OFlux
CO2 cropland
wet season
fluxes were
much larger
than
hypothesized.
CH4 emissions
in forests had
strong
heterogeneity
within site.

18. While post-fertilization N2O peaks can be substantial,
in several cases they barely deviated from the baseline.

19. Are these differences in fertilization response between
sites driven by soil moisture? Initial results suggest not.
S MF

20. 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

21. 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…

23. 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

24. 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

25. 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?

26. 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

28. We are limited by
ideas, not by tools
- Peter Groffman