Drought impact on forest carbon dynamics and fluxes in Amazonia.
In 2005 and 2010 the Amazon basin experienced two strong droughts, driven by shifts in the tropical hydrological regime possibly associated with global climate change, as predicted by some global models. Tree mortality increased after the 2005 drought, 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. We propose that weakened maintenance and defence investment may, in turn, cause the increase in post-drought tree mortality observed at our plots.
Environmental Change Institute, School of Geography and the Environment, University of Oxford, Oxford OX1 3QY, UK.
Christopher E
CE
Doughty
Department of Physical Geography and Ecosystem Science, Lund University, Sölvegatan 12, 223 62 Lund, Sweden.
D B
DB
Metcalfe
Environmental Change Institute, School of Geography and the Environment, University of Oxford, Oxford OX1 3QY, UK.
C A J
CA
Girardin
Universidad Nacional San Antonio Abad de Cusco, Apartado Postal Nro 921, Cusco, Perú
F Farfán
FF
Amézquita
Universidad Nacional San Antonio Abad de Cusco, Apartado Postal Nro 921, Cusco, Perú
D Galiano
DG
Cabrera
Universidad Nacional San Antonio Abad de Cusco, Apartado Postal Nro 921, Cusco, Perú
W Huaraca
WH
Huasco
Universidad Nacional San Antonio Abad de Cusco, Apartado Postal Nro 921, Cusco, Perú
J E
JE
Silva-Espejo
Museo de Historia Natural Noel Kempff Mercado, Universidad Autónoma Gabriel Rene Moreno, Av. Irala 565, Casilla 2489, Santa Cruz, Bolivia.
A
A
Araujo-Murakami
Universidade Federal do Pará, Instituto de Geociências, Faculdade de Meteorologia, Rua Augusto Correa, n° 01, CEP 66075 - 110, Belém, Pará, Brazil.
M C
MC
da Costa
IPAM Instituto de Pesquisa Ambiental da Amazônia Rua Horizontina, 104, Centro, 78640-000 Canarana, Mato Grosso, Brazil.
W
W
Rocha
Department of Geography, College of Life and Environmental Sciences, University of Exeter, Exeter EX4 4RJ, UK.
T R
TR
Feldpausch
Universidad Nacional San Antonio Abad de Cusco, Apartado Postal Nro 921, Cusco, Perú
A L M
AL
Mendoza
Universidade Federal do Pará, Instituto de Geociências, Faculdade de Meteorologia, Rua Augusto Correa, n° 01, CEP 66075 - 110, Belém, Pará, Brazil.
A C L
AC
da Costa
1] School of Geosciences, University of Edinburgh, Edinburgh EH9 3FF, UK [2] Research School of Biology, Australian National University, Canberra, Australian Capital Territory 2601, Australia.
P
P
Meir
School of Geography, University of Leeds, Leeds LS2 9JT, UK.
O L
OL
Phillips
Environmental Change Institute, School of Geography and the Environment, University of Oxford, Oxford OX1 3QY, UK.
Y
Y
Malhi
D001938:Brazil; D002244:Carbon / Q000378:metabolism*; D002245:Carbon Dioxide / Q000378:metabolism; D019069:Cell Respiration; D055864:Droughts; D065928:Forests; D010788:Photosynthesis; D014197:Trees / Q000166:cytology / Q000378:metabolism; D014329:Tropical Climate
D002245:Carbon Dioxide; D002244:Carbon