The effect of a permafrost disturbance on growing-season carbon-dioxide fluxes in a high Arctic tundra ecosystem
Soil carbon stored in high-latitude permafrost landscapes is threatened by warming and could contribute significant amounts of carbon to the atmosphere and hydrosphere as permafrost thaws. Thermokarst and permafrost disturbances, especially active layer detachments and retrogressive thaw slumps, are...
Main Authors: | , , |
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Format: | Article |
Language: | English |
Published: |
Copernicus Publications
2016-04-01
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Series: | Biogeosciences |
Online Access: | http://www.biogeosciences.net/13/2291/2016/bg-13-2291-2016.pdf |
Summary: | Soil carbon stored in high-latitude permafrost landscapes is threatened by
warming and could contribute significant amounts of carbon to the
atmosphere and hydrosphere as permafrost thaws. Thermokarst and permafrost
disturbances, especially active layer detachments and retrogressive thaw
slumps, are present across the Fosheim Peninsula, Ellesmere Island, Canada.
To determine the effects of retrogressive thaw slumps on net ecosystem
exchange (NEE) of CO<sub>2</sub> in high Arctic tundra, we used two eddy
covariance (EC) tower systems to simultaneously and continuously measure
CO<sub>2</sub> fluxes from a disturbed site and the surrounding undisturbed
tundra. During the 32-day measurement period in the 2014 growing season, the
undisturbed tundra was a small net sink (NEE = −0.1 g C m<sup>−2</sup> d<sup>−1</sup>); however, the disturbed terrain of the retrogressive thaw slump
was a net source (NEE = +0.4 g C m<sup>−2</sup> d<sup>−1</sup>). Over the
measurement period, the undisturbed tundra sequestered 3.8 g C m<sup>−2</sup>,
while the disturbed tundra released 12.5 g C m<sup>−2</sup>. Before full leaf-out
in early July, the undisturbed tundra was a small source of CO<sub>2</sub> but
shifted to a sink for the remainder of the sampling season (July), whereas
the disturbed tundra remained a source of CO<sub>2</sub> throughout the season. A
static chamber system was also used to measure daytime fluxes in the
footprints of the two towers, in both disturbed and undisturbed tundra, and
fluxes were partitioned into ecosystem respiration (<i>R</i><sub>e</sub>) and gross
primary production (GPP). Average GPP and <i>R</i><sub>e</sub> found in disturbed tundra
were smaller (+0.40 µmol m<sup>−2</sup> s<sup>−1</sup> and +0.55 µmol m<sup>−2</sup> s<sup>−1</sup>, respectively) than those found in undisturbed tundra
(+1.19 µmol m<sup>−2</sup> s<sup>−1</sup> and +1.04 µmol m<sup>−2</sup> s<sup>−1</sup>, respectively). Our measurements indicated clearly that the
permafrost disturbance changed the high Arctic tundra system from a sink to
a source for CO<sub>2</sub> during the majority of the growing season (late June
and July). |
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ISSN: | 1726-4170 1726-4189 |