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

Motivation: will Amazon forest die-back with future climate change? 45 S 90S 90W 0 1 2 3 4 5 6 7 8 Mean daily temperature change(K) -3 -2 -1 -0.5 0.5 1 2 3 Precipitation change (mm day-1) Differences relative to 1990 - 2090 mean -8 -4 -2 -1 1 2 4 8 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

Motivation: August 2008 – June 2008 La Niña Event Oceanic Nino Index, ONI (ERSST.v3b ONI) Upper ocean heat anomalies (1991 -2009) 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. 1990 1992 1994 1996 1998 2000 2002 2004 2006 2008 2010 La Niña ONI value for ASO 2007 – AMJ 2008 is -1.4oC The most recent ONI value (July – September 2009) is +0.8oC. Source: http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_advisory/

Motivation: 2008 – June 2008 La Niña Event Oceanic Nino Index, ONI (ERSST.v3b ONI) Upper ocean heat anomalies (1991 -2009) 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. 1990 1992 1994 1996 1998 2000 2002 2004 2006 2008 2010 NOV JAN MAR MAY JUL 2008 2009 Source: http://www.cpc.ncep.noaa.gov/

Motivation: South America precipitation 2008 – 2009 Apr-May Normilized anomaly K67 K67 Anomaly=((precip)m,y -(mean precip)m,1998-2009)/(std dev precip)m,1998-2009) 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 – 2009 [NASA, 2006]

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

Tapajós K67 tropical forest

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

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

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

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

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)

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

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

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

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

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?

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