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Drought impact on forest carbon dynamics and fluxes in Amazonia

Doughty, Christopher E.; Metcalfe, Dan LU ; Girardin, C. A. J.; Farfan Amezquita, F.; Galiano Cabrera, D.; Huaraca Huasco, W.; Silva-Espejo, J. E.; Araujo-Murakami, A.; da Costa, M. C. and Rocha, W., et al. (2015) In Nature 519(7541). p.78-140
Abstract
In 2005 and 2010 the Amazon basin experienced two strong droughts', driven by shifts in the tropical hydrological regime(2) possibly associated with global climate change(3), as predicted by some global models'. Tree mortality increased after the 2005 drought(4), 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... (More)
In 2005 and 2010 the Amazon basin experienced two strong droughts', driven by shifts in the tropical hydrological regime(2) possibly associated with global climate change(3), as predicted by some global models'. Tree mortality increased after the 2005 drought(4), 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 growth(6). We propose that weakened maintenance and defence investment may, in turn, cause the increase in post-drought tree mortality observed at our plots. (Less)
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Nature
volume
519
issue
7541
pages
78 - 140
publisher
Nature Publishing Group
external identifiers
  • wos:000350304000039
  • scopus:84924353432
ISSN
0028-0836
DOI
10.1038/nature14213
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English
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yes
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be9e4bbe-48a2-420e-8127-447ade8944bf (old id 5305085)
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2015-04-27 11:41:06
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@article{be9e4bbe-48a2-420e-8127-447ade8944bf,
  abstract     = {In 2005 and 2010 the Amazon basin experienced two strong droughts', driven by shifts in the tropical hydrological regime(2) possibly associated with global climate change(3), as predicted by some global models'. Tree mortality increased after the 2005 drought(4), 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 growth(6). We propose that weakened maintenance and defence investment may, in turn, cause the increase in post-drought tree mortality observed at our plots.},
  author       = {Doughty, Christopher E. and Metcalfe, Dan and Girardin, C. A. J. and Farfan Amezquita, F. and Galiano Cabrera, D. and Huaraca Huasco, W. and Silva-Espejo, J. E. and Araujo-Murakami, A. and da Costa, M. C. and Rocha, W. and Feldpausch, T. R. and Mendoza, A. L. M. and da Costa, A. C. L. and Meir, P. and Phillips, O. L. and Malhi, Y.},
  issn         = {0028-0836},
  language     = {eng},
  number       = {7541},
  pages        = {78--140},
  publisher    = {Nature Publishing Group},
  series       = {Nature},
  title        = {Drought impact on forest carbon dynamics and fluxes in Amazonia},
  url          = {http://dx.doi.org/10.1038/nature14213},
  volume       = {519},
  year         = {2015},
}