Climate indices strongly influence old-growth forest carbon exchange

We present a decade and a half (1998-2013) of carbon dioxide fluxes from an old-growth stand in the American Pacific Northwest to identify ecosystem-level responses to Pacific teleconnection patterns, including the El Niño Southern Oscillation (ENSO). This study provides the longest, continuous reco...

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Bibliographic Details
Published in:Environmental research letters 2016-04, Vol.11 (4), p.44016-44026
Main Authors: Wharton, Sonia, Falk, Matthias
Format: Article
Language:English
Subjects:
60 APPLIED LIFE SCIENCES
AmeriFlux
Carbon
Carbon dioxide
Carbon sinks
Carbon sources
Climate
Climate variability
eddy covariance
El Nino
ENVIRONMENTAL SCIENCES
Exchanging
Fluxes
Forests
interannual variability
La Nina
net ecosystem exchange
Net Primary Productivity
old-growth forest
Pacific teleconnections
Southern Oscillation
Switches
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Summary:We present a decade and a half (1998-2013) of carbon dioxide fluxes from an old-growth stand in the American Pacific Northwest to identify ecosystem-level responses to Pacific teleconnection patterns, including the El Niño Southern Oscillation (ENSO). This study provides the longest, continuous record of old-growth eddy flux data to date from one of the longest running Fluxnet stations in the world. From 1998 to 2013, average annual net ecosystem exchange (FNEE) at Wind River AmeriFlux was −32 84 g C m−2 yr−1 indicating that the late seral forest is on average a small net sink of atmospheric carbon. However, interannual variability is high (>300 g C m−2 yr−1) and shows that the stand switches from net carbon sink to source in response to climate drivers associated with ENSO. The old-growth forest is a much stronger sink during La Niña years (mean FNEE = −90 g C m−2 yr−1) than during El Niño when the stand turns carbon neutral or into a small net carbon source (mean FNEE = +17 g C m−2 yr−1). Forest inventory data dating back to the 1930s show a similar correlation with the lower frequency Pacific North American (PNA) and Pacific Decadal Oscillation (PDO) whereby higher aboveground net primary productivity (FANPP) is associated with cool phases of both the PNA and PDO. These measurements add evidence that carbon exchange in old-growth stands may be more sensitive to climate variability across shorter time scales than once thought.
ISSN:1748-9326
1748-9326
DOI:10.1088/1748-9326/11/4/044016