In 2005 and 2010 the Amazon basin experienced two strong droughts1, driven by shifts in the tropical hydrological regime2 possibly associated with global climate change3, as predicted by some global models3. Tree mortality increased after the 2005 drought4, and regional atmospheric inversion modelling showed basin-wide decreases in CO2 uptake in 2010 compared with 2011 (ref. 5). But the response of tropical forest carbon cycling to these droughts is not fully understood and there has been no detailed multi-site investigation in situ. Here we use several years of data from a network of thirteen 1-ha forest plots spread throughout South America, where each component of net primary production (NPP), autotrophic respiration and heterotrophic respiration is measured separately, to develop a better mechanistic understanding of the impact of the 2010 drought on the Amazon forest. We find that total NPP remained constant throughout the drought. However, towards the end of the drought, autotrophic respiration, especially in roots and stems, declined significantly compared with measurements in 2009 made in the absence of drought, with extended decreases in autotrophic respiration in the three driest plots. In the year after the drought, total NPP remained constant but the allocation of carbon shifted towards canopy NPP and away from fine-root NPP. Both leaf-level and plot-level measurements indicate that severe drought suppresses photosynthesis. Scaling these measurements to the entire Amazon basin with rainfall data, we estimate that drought suppressed Amazon-wide photosynthesis in 2010 by 0.38 petagrams of carbon (0.23–0.53 petagrams of carbon). Overall, we find that during this drought, instead of reducing total NPP, trees prioritized growth by reducing autotrophic respiration that was unrelated to growth. This suggests that trees decrease investment in tissue maintenance and defence, in line with eco-evolutionary theories that trees are competitively disadvantaged in the absence of growth6. We propose that weakened maintenance and defence investment may, in turn, cause the increase in post-drought tree mortality observed at our plots.
Access optionsAccess options
Subscribe to Journal
Get full journal access for 1 year
only $3.90 per issue
All prices are NET prices.
VAT will be added later in the checkout.
Rent or Buy article
Get time limited or full article access on ReadCube.
All prices are NET prices.
We thank P. Brando and Tanguro partners for logistical support and advice. This work is a product of the Global Ecosystems Monitoring (GEM) network (http://gem.tropicalforests.ox.ac.uk) and the RAINFOR and ABERG research consortia, and was funded by grants to Y.M. and O.L.P. from the Gordon and Betty Moore Foundation to the Amazon Forest Inventory Network (RAINFOR) and the Andes Biodiversity and Ecosystems Research Group (ABERG), and grants from the UK Natural Environment Research Council (NE/D01025X/1, NE/D014174/1, NE/F002149/1 and NE/J011002/1), the NERC AMAZONICA consortium grant (NE/F005776/1) and the EU FP7 Amazalert (282664) GEOCARBON (283080) projects. Some data in this publication were provided by the Tropical Ecology Assessment and Monitoring (TEAM) Network, a collaboration between Conservation International, the Missouri Botanical Garden, the Smithsonian Institution and the Wildlife Conservation Society, and partly funded by these institutions, the Gordon and Betty Moore Foundation, and other donors. T.R.F. is supported by a National Council for Scientific and Technological Development (CNPq, Brazil) award. P.M. is supported by an ARC fellowship award FT110100457; O.L.P. is supported by an ERC Advanced Investigator Award and a Royal Society Wolfson Research Merit Award; Y.M. is supported by an ERC Advanced Investigator Award and by the Jackson Foundation. C.E.D. acknowledges funding from the John Fell Fund.
About this article
Uncertainty Quantification of Extratropical Forest Biomass in CMIP5 Models over the Northern Hemisphere
Scientific Reports (2018)