1. Carbon loss on the other side of drought:  excess wet season precipitation during La Niña suppresses Amazon forest photosynthesis
Natalia Restrepo-Coupe,
Brad Christoffersen, Daniel F. Amaral, Plínio B. de Camargo;
Scott R. Saleska

2. Motivation: will Amazon forest die-back with future climate change?
45 S
90S
90W
Mean daily temperature
change(K)
Precipitation change (mm day-1)
Differences relative to mean
Change in Vegetation Carbon (kg C m-2)
Adapted from: Cox et al., 2003, Amazon Dieback under Climate-Carbon Cycle Projections for the 21st Century

3. Motivation: August 2008 – June 2008 La Niña Event
Oceanic Nino Index, ONI (ERSST.v3b ONI)
Upper ocean heat anomalies ( ) 4 3 2 1 -1 -2 -3
Sea Surface Temperature
Anomlies (C)
El Niño
neutral
La Niña
The basin-wide equatorial upper ocean (0-300 m) heat content is greatest prior to and during the early stages of a Pacific warm (El Niño) episode (compare top 2 panels) and least prior to and during the early stages of a cold (La Niña) episode.
La Niña ONI value for ASO 2007 – AMJ 2008 is oC
The most recent ONI value (July – September 2009) is +0.8oC.
Source:

4. Motivation: 2008 – June 2008 La Niña Event
Oceanic Nino Index, ONI (ERSST.v3b ONI)
Upper ocean heat anomalies ( ) 4 3 2 1 -1 -2 -3
1.5 1
0.5
-0.5 -1 -2
Sea Surface Temperature
Anomlies (C)
neutral
La Niña
Sea Surface Temperature
Anomlies (C)
The basin-wide equatorial upper ocean (0-300 m) heat content is greatest prior to and during the early stages of a Pacific warm (El Niño) episode (compare top 2 panels) and least prior to and during the early stages of a cold (La Niña) episode.
NOV JAN MAR MAY JUL
Source:

5. Motivation: South America precipitation 2008 – 2009
Apr-May
Normilized anomaly
K67
K67
Anomaly=((precip)m,y -(mean precip)m, )/(std dev precip)m, )
departure from the 1998–2009 mean (TRMM1998 – 2009), normalized by the standard deviation (s).
Lon
Lon
Tropical Rainfall Measuring Mission (TRMM) data, at 0.25 spatial resolution 1998 – [NASA, 2006]

6. … on the other side of drought …
Caxiuana calculate the anomaly

7. Tapajós K67 tropical forest

8. Tapajós K67 tropical forest: Climate
dry season wet season
Aug 2008 – Jul 2009
dry season wet season
Dry season starts ~15 July
dry season wet season
Hydrological year: Dry season – Wet season
HY2002: Aug 1, 2002 – Jul 31, 2003 HY2003: Aug 1, 2003 – Jul 31, 2004
HY2004: Aug 1, 2004 – Jul 31, 2005 HY2005: Aug 1, 2005 – Jan 6, 2006
HY2008: Aug 1, 2008 – Jul 31, 2009

9. Result 1: La Niña Event corresponds to C Forest Loss
Aug 2008 – Jul 2009
dry season wet season
Net ecosystem exchange
Forest C losses
Forest C uptake

10. Result 1: La Niña Event corresponds to C Forest Loss
Aug 2008 – Jul 2009
dry season wet season
dry season wet season
Instantaneous C-flux
Cumulative C-flux and Precipitation

11. What is the cause of C-loss? (split into photosynthesis & respiration)
NEE: Net Ecosystem Exchange
R: Ecosystem Respiration
GEE: Gross Ecosystem Productivity
~ Photosynthetic activity
Higher C losses
dry season wet season
Higher C uptake
NEE = R + GEE

12. Result 2: Forest C Loss is due to reduced photosynthesis
NEE: Net Ecosystem Exchange
R: Ecosystem Respiration
GEE: Gross Ecosystem Productivity
~ Photosynthetic activity
Higher C losses
dry season wet season
dry season wet season
dry season wet season
Higher C uptake
NEE = R + GEE
Reduced photosynthesis (less negative)

13. What is the cause of reduced photosynthesis?
Higher C losses
dry season wet season
dry season wet season
Higher C uptake

14. What is the cause of reduced photosynthesis?
Higher C losses
Lower PAR and…
dry season wet season
dry season wet season
Higher C uptake

15. Decreased photosynthetic response
Result 3: decreased photosynthetic response
Decreased photosynthetic response
Jan
Higher C losses
dry season wet season
GEP = -GEE
dry season wet season
Feb
Higher C uptake

16. What is the cause of reduced photosynthetic response?
Earlier onset of the wet season?
High soil moisture? ….

17. Summary: at Tapajós K67 tropical forest
Result 1: La Niña Event (wet wet season and earlier onset of the wet season, corresponds to C Forest Loss.
Result 2: Forest C Loss is due to reduced photosynthesis.
Result 3: decreased photosynthetic response.
Future work: Investigaion on the cause of reduced photosynthetic response?

18. Acknowledgments
This research was funded by the National Science Foundation’s Partnerships for International Research and Education (PIRE) and the National Aeronautics and Space Administration (NASA) LBA investigation CD-32.
Thank you