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