Post on 17-Jul-2015
transcript
GHG Emissions in Southeastern Amazonia: The Effect of Agricultural Intensification
Christine OConnell, Paulo Brando, Carlos Eduardo Cerri, Michael Coe, Eric Davidson, Gillian Galford, Marcia Macedo, Chris Neill, Rodney Venterea
AAG 2015 22 April 2015
Q What are the impacts
of intensifying agriculture in Amazonia
on greenhouse gas emissions?
~20% of Amazonia is deforested, largely for
agricultural export commodities
Hansen et al. (2013), Nepstad et al. (2014)
Southeastern Amazonia is rapidly transitioning to a novel form of industrial,
highly managed tropical agricultureDeFries et al. (2014), Spera et al. (2014)
Tanguro Ranch: Land use change impacts case study
Tanguro Ranch: Land use change impacts case study
Tanguro Ranch: Land use change impacts case study
Tanguro Ranch: Land use change impacts case study
Tanguro Ranch: Land use change impacts case study
Tanguro Ranch: Land use change impacts case study
Tanguro Ranch: Land use change impacts case study
Tanguro Ranch has three land uses:
transitional Amazon forest (F), soybean cultivation (S), and
soybean/maize (double cropped)
cultivation (M).MAT: 27C
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)
Field measurement of N pools and GHG fluxes
N2Oor 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
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
S MF
F S MCH
4 Flu
x
CO2 F
lux
N 2
O F
lux CO2 cropland
wet season fluxes were much larger
than hypothesized.
CH4 emissions in forests had
strong heterogeneity
within site.
While post-fertilization N2O peaks can be substantial, in several cases they barely deviated from the baseline.
Are these differences in fertilization response between sites driven by soil moisture? Initial results suggest not.
S MF
What about row / inter-row heterogeneity?
N2O emissions are highest between rows in M; CO2 emissions are highest on the row in S.
ForestInter-rowRow
F M S F M S F M S
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
N2Ois 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
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
Global nutrient cycles?
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?
Thanks very much
Photo credits Flickr CC Users
CIFORBilltacular
Jacsonquerubinflinner!
Carine06LeoFFreitas
terryduggalliceIcelight
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. OConnell, coconn@umn.edu, UMN EEB/IonE
We are limited by
ideas, not by tools
- Peter Groffman