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The fate of assimilated carbon during drought: impacts on respiration in Amazon rainforests

Meir, P.; Metcalfe, Dan LU ; Costa, A. C. L. and Fisher, R. A. (2008) In Royal Society of London. Philosophical Transactions B. Biological Sciences 363(1498). p.1849-1855
Abstract
Interannual variations in CO2 exchange across Amazonia, as deduced from atmospheric inversions, correlate with El Nino occurrence. They are thought to result from changes in net ecosystem exchange and fire incidence that are both related to drought intensity. Alterations to net ecosystem production (NEP) are caused by changes in gross primary production (GPP) and ecosystem respiration (R-eco). Here, we analyse observations of the components of R-eco (leaves, live and dead woody tissue, and soil) to provide first estimates of changes in R-eco during short-term (seasonal to interannual) moisture limitation. Although photosynthesis declines if moisture availability is limiting, leaf dark respiration is generally maintained, potentially... (More)
Interannual variations in CO2 exchange across Amazonia, as deduced from atmospheric inversions, correlate with El Nino occurrence. They are thought to result from changes in net ecosystem exchange and fire incidence that are both related to drought intensity. Alterations to net ecosystem production (NEP) are caused by changes in gross primary production (GPP) and ecosystem respiration (R-eco). Here, we analyse observations of the components of R-eco (leaves, live and dead woody tissue, and soil) to provide first estimates of changes in R-eco during short-term (seasonal to interannual) moisture limitation. Although photosynthesis declines if moisture availability is limiting, leaf dark respiration is generally maintained, potentially acclimating upwards in the longer term. If leaf area is lost, then short-term canopy-scale respiratory effluxes from wood and leaves are likely to decline. Using a moderate short-term drying scenario where soil moisture limitation leads to a loss of 0.5 m(2) m(-2) yr(-1) in leaf area index, we estimate a reduction in respiratory CO2 efflux from leaves and live woody tissue of 1.0 (+/-0.4) t C ha(-1) yr(-1). Necromass decomposition declines during drought, but mortality increases; the median mortality increase following a strong El Nino is 1.1% (n=46 tropical rainforest plots) and yields an estimated net short-term increase in necromass CO2 efflux of 0.13-0.18 t C ha(-1) yr(-1). Soil respiration is strongly sensitive to moisture limitation over the short term, but not to associated temperature increases. This effect is underestimated in many models but can lead to estimated reductions in CO2 efflux of 2.0 (+/-0.5) t C ha(-1) yr(-1). Thus, the majority of short-term respiratory responses to drought point to a decline in R-eco, an outcome that contradicts recent regional-scale modelling of NEP. NEP varies with both GPP and R-eco but robust moisture response functions are clearly needed to improve quantification of the role of R-eco in influencing regional-scale CO2 emissions from Amazonia. (Less)
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author
publishing date
type
Contribution to journal
publication status
published
subject
keywords
net ecosystem exchange, drought, respiration, leaf, woody tissue, soil
in
Royal Society of London. Philosophical Transactions B. Biological Sciences
volume
363
issue
1498
pages
1849 - 1855
publisher
Royal Society
external identifiers
  • wos:000254577500017
  • scopus:41649094550
ISSN
1471-2970
DOI
10.1098/rstb.2007.0021
language
English
LU publication?
no
id
39795ec0-2c88-40fc-bd7e-5faec7dd3638 (old id 4644073)
date added to LUP
2014-09-26 07:39:55
date last changed
2017-11-19 04:00:17
@article{39795ec0-2c88-40fc-bd7e-5faec7dd3638,
  abstract     = {Interannual variations in CO2 exchange across Amazonia, as deduced from atmospheric inversions, correlate with El Nino occurrence. They are thought to result from changes in net ecosystem exchange and fire incidence that are both related to drought intensity. Alterations to net ecosystem production (NEP) are caused by changes in gross primary production (GPP) and ecosystem respiration (R-eco). Here, we analyse observations of the components of R-eco (leaves, live and dead woody tissue, and soil) to provide first estimates of changes in R-eco during short-term (seasonal to interannual) moisture limitation. Although photosynthesis declines if moisture availability is limiting, leaf dark respiration is generally maintained, potentially acclimating upwards in the longer term. If leaf area is lost, then short-term canopy-scale respiratory effluxes from wood and leaves are likely to decline. Using a moderate short-term drying scenario where soil moisture limitation leads to a loss of 0.5 m(2) m(-2) yr(-1) in leaf area index, we estimate a reduction in respiratory CO2 efflux from leaves and live woody tissue of 1.0 (+/-0.4) t C ha(-1) yr(-1). Necromass decomposition declines during drought, but mortality increases; the median mortality increase following a strong El Nino is 1.1% (n=46 tropical rainforest plots) and yields an estimated net short-term increase in necromass CO2 efflux of 0.13-0.18 t C ha(-1) yr(-1). Soil respiration is strongly sensitive to moisture limitation over the short term, but not to associated temperature increases. This effect is underestimated in many models but can lead to estimated reductions in CO2 efflux of 2.0 (+/-0.5) t C ha(-1) yr(-1). Thus, the majority of short-term respiratory responses to drought point to a decline in R-eco, an outcome that contradicts recent regional-scale modelling of NEP. NEP varies with both GPP and R-eco but robust moisture response functions are clearly needed to improve quantification of the role of R-eco in influencing regional-scale CO2 emissions from Amazonia.},
  author       = {Meir, P. and Metcalfe, Dan and Costa, A. C. L. and Fisher, R. A.},
  issn         = {1471-2970},
  keyword      = {net ecosystem exchange,drought,respiration,leaf,woody tissue,soil},
  language     = {eng},
  number       = {1498},
  pages        = {1849--1855},
  publisher    = {Royal Society},
  series       = {Royal Society of London. Philosophical Transactions B. Biological Sciences},
  title        = {The fate of assimilated carbon during drought: impacts on respiration in Amazon rainforests},
  url          = {http://dx.doi.org/10.1098/rstb.2007.0021},
  volume       = {363},
  year         = {2008},
}