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

Death from drought in tropical forests is triggered by hydraulics not carbon starvation
Death from drought in tropical forests is triggered by hydraulics not carbon starvation
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.
0028-0836
119–122
Rowland, L.
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Da Costa, A. C. L.
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Galbraith, D. R.
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Oliveira, R. S.
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Binks, O. J.
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Oliveira, A. A. R.
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Pullen, A. M.
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Doughty, C. E.
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Metcalfe, D. B.
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Vasconcelos, S. S.
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Ferreira, L. V.
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Malhi, Y.
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Grace, J.
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Mencuccini, M.
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Meir, P.
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Rowland, L.
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Da Costa, A. C. L.
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Galbraith, D. R.
d8a1a39d-9723-4963-b136-f4dba9e6bc22
Oliveira, R. S.
a690f845-1591-4b35-9a06-4cc681844c50
Binks, O. J.
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Oliveira, A. A. R.
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Pullen, A. M.
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Doughty, C. E.
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Metcalfe, D. B.
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Vasconcelos, S. S.
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Ferreira, L. V.
259a9e7a-b55a-4d1a-98e8-36b4a85a16d9
Malhi, Y.
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Grace, J.
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Mencuccini, M.
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Meir, P.
7d45259e-5dc0-44dc-b78c-466f6e207d36

Rowland, L., Da Costa, A. C. L., Galbraith, D. R., Oliveira, R. S., Binks, O. J., Oliveira, A. A. R., Pullen, A. M., Doughty, C. E., Metcalfe, D. B., Vasconcelos, S. S., Ferreira, L. V., Malhi, Y., Grace, J., Mencuccini, M. and Meir, P. (2015) Death from drought in tropical forests is triggered by hydraulics not carbon starvation. Nature, 119–122. (doi:10.1038/nature15539).

Record type: Article

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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Published date: 3 December 2015

Identifiers

Local EPrints ID: 417046
URI: https://eprints.soton.ac.uk/id/eprint/417046
ISSN: 0028-0836
PURE UUID: 80cdc676-6014-4e7e-a58f-be64b8ef1a40

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Date deposited: 18 Jan 2018 17:30
Last modified: 05 Mar 2019 17:31

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