Letter | Published:

Death from drought in tropical forests is triggered by hydraulics not carbon starvation

Nature volume 528, pages 119122 (03 December 2015) | Download Citation

Abstract

Drought threatens tropical rainforests over seasonal to decadal timescales1,2,3,4, but the drivers of tree mortality following drought remain poorly understood5,6. It has been suggested that reduced availability of non-structural carbohydrates (NSC) critically increases mortality risk through insufficient carbon supply to metabolism (‘carbon starvation’)7,8. However, little is known about how NSC stores are affected by drought, especially over the long term, and whether they are more important than hydraulic processes in determining drought-induced mortality. Using data from the world’s longest-running experimental drought study in tropical rainforest (in the Brazilian Amazon), we test whether carbon starvation or deterioration of the water-conducting pathways from soil to leaf trigger tree mortality. Biomass loss from mortality in the experimentally droughted forest increased substantially after >10 years of reduced soil moisture availability. The mortality signal was dominated by the death of large trees, which were at a much greater risk of hydraulic deterioration than smaller trees. However, we find no evidence that the droughted trees suffered carbon starvation, as their NSC concentrations were similar to those of non-droughted trees, and growth rates did not decline in either living or dying trees. Our results indicate that hydraulics, rather than carbon starvation, triggers tree death from drought in tropical rainforest.

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Acknowledgements

This work was supported by UK NERC grant NE/J011002/1 to P.M. and M.M., CNPQ grant 457914/2013-0/MCTI/CNPq/FNDCT/LBA/ESECAFLOR to A.C.L.D., and ARC grant FT110100457 to P.M. It was previously supported by NERC NER/A/S/2002/00487, NERC GR3/11706, EU FP5-Carbonsink and EU FP7-Amazalert to P.M. and J.G., and by grant support to Y.M. from NERC NE/D01025X/1 and the Gordon and Betty Moore Foundation. L.R., M.M. and P.M. would also like to acknowledge support from S. Sitch, Y. Salmon and B. Christoffersen. The authors would also like to thank three anonymous referees for their useful comments.

Author information

Affiliations

  1. School of GeoSciences, University of Edinburgh, Edinburgh EH9 3FF, UK

    • L. Rowland
    • , O. J. Binks
    • , J. Grace
    • , M. Mencuccini
    •  & P. Meir
  2. Centro de Geosciências, Universidade Federal do Pará, Belém 66075-110, Brazil

    • A. C. L. da Costa
    •  & A. A. R. Oliveira
  3. School of Geography, University of Leeds, Leeds LS2 9JT, UK

    • D. R. Galbraith
  4. Instituto de Biologia, UNICAMP, Campinas 13.083-970, Brazil

    • R. S. Oliveira
  5. The University of Cambridge, Cambridge CB2 1TN, UK

    • A. M. Pullen
  6. Environmental Change Institute, The University of Oxford, Oxford OX1 3QY, UK

    • C. E. Doughty
    •  & Y. Malhi
  7. Department of Physical Geography and Ecosystem Science, Lund University, Lund S-223 62, Sweden

    • D. B. Metcalfe
  8. EMBRAPA Amazônia Oriental, Belém 66095-903, Brazil

    • S. S. Vasconcelos
  9. Museu Paraense Emílio Goeldi, Belém 66077-830, Brazil

    • L. V. Ferreira
  10. ICREA at CREAF, 08193 Cerdanyola del Vallés, Spain

    • M. Mencuccini
  11. Research School of Biology, Australian National University, Canberra, Australian Capital Territory 2601, Australia

    • P. Meir

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Contributions

L.R., P.M., A.C.L.D. and M.M. designed and implemented the research. P.M. conceived and led the experiment and this study. L.R. led recent measurements; all authors contributed to data collection, led by A.C.L.D.; L.R. analysed the data with M.M., P.M., O.J.B. and A.M.P.; L.R. wrote the paper with P.M. and M.M., with contributions from all authors.

Competing interests

The authors declare no competing financial interests.

Corresponding author

Correspondence to L. Rowland.

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DOI

https://doi.org/10.1038/nature15539

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