Identification

Title

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

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.

Resource type

document

Resource locator

Unique resource identifier

code

http://n2t.net/ark:/85065/d7kd1zk4

codeSpace

Dataset language

eng

Spatial reference system

code identifying the spatial reference system

Classification of spatial data and services

Topic category

geoscientificInformation

Keywords

Keyword set

keyword value

Text

originating controlled vocabulary

title

Resource Type

reference date

date type

publication

effective date

2016-01-01T00:00:00Z

Geographic location

West bounding longitude

East bounding longitude

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South bounding latitude

Temporal reference

Temporal extent

Begin position

End position

Dataset reference date

date type

publication

effective date

2008-05-01T00:00:00Z

Frequency of update

Quality and validity

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Conformity

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name of format

version of format

Constraints related to access and use

Constraint set

Use constraints

Limitations on public access

None

Responsible organisations

Responsible party

contact position

OpenSky Support

organisation name

UCAR/NCAR - Library

full postal address

PO Box 3000

Boulder

80307-3000

email address

opensky@ucar.edu

web address

http://opensky.ucar.edu/

name: homepage

responsible party role

pointOfContact

Metadata on metadata

Metadata point of contact