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| Titel |
Effects of winter temperature and summer drought on net ecosystem exchange of CO2 in a temperate peatland |
| VerfasserIn |
Carole Helfter, Claire Campbell, Kerry Dinsmore, Julia Drewer, Mhairi Coyle, Margaret Anderson, Ute Skiba, Eiko Nemitz, Michael Billett, Mark Sutton |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250088141
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| Publikation (Nr.) |
 EGU/EGU2014-2220.pdf |
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| Zusammenfassung |
| Northern peatlands are one of the most important global sinks of atmospheric carbon dioxide
(CO2); their ability to sequester C is a natural feedback mechanism controlled by climatic
variables such as precipitation, temperature, length of growing season and period of snow
cover. In the UK it has been predicted that peatlands could become a net source of carbon in
response to climate change with climate models predicting a rise in global temperature of ca.
3oC between 1961-1990 and 2100. Land-atmosphere exchange of CO2in peatlands exhibits
marked seasonal and inter-annual variations, which have significant short- and long-term
effects on carbon sink strength.
Net ecosystem exchange (NEE) of CO2 has been measured continuously by
eddy-covariance (EC) at Auchencorth Moss (55°47’32 N, 3°14’35 W, 267 m a.s.l.), a
temperate peatland in central Scotland, since 2002. Auchencorth Moss is a low-lying,
ombrotrophic peatland situated ca. 20 km south-west of Edinburgh. Peat depth ranges from
5 m and the site has a mean annual precipitation of 1155 mm. The vegetation
present within the flux measurement footprint comprises mixed grass species, heather and
substantial areas of moss species (Sphagnum spp. and Polytrichum spp.). The EC system
consists of a LiCOR 7000 closed-path infrared gas analyser for the simultaneous
measurement of CO2 and water vapour and of a Gill Windmaster Pro ultrasonic
anemometer.
Over the 10 year period, the site was a consistent yet variable sink of CO2 ranging from
-34.1 to -135.9 g CO2-C m-2 yr-1 (mean of -69.1 ± 33.6 g CO2-C m-2 yr-1). Inter-annual
variability in NEE was positively correlated to the length of the growing seasons
and mean winter air temperature explained 93% of the variability in summertime
sink strength, indicating a phenological memory-effect. Plant development and
productivity were stunted by colder winters causing a net reduction in the annual
carbon sink strength of this peatland where autotrophic processes are thought to be
dominant. The site is wet throughout most of the year (water table depth < 5 cm below
the peat surface), but there are indications that drought enhanced heterotrophic
respiration and depressed gross primary productivity (GPP); a sustained drought
during the summer of 2010 (maximum water table depth 36 cm below surface)
was accompanied by a two-fold increase in total respiration and a 30% decrease in
GPP. The cold preceding winter could also have contributed to lowering GPP, and
disentangling the confounding adverse effects of drought and winter climate on GPP
is thus not straightforward. Whilst 2010 had the smallest NEE in the 2002-2012
period, the largest values were found for years with warm winters and relatively wet
growing seasons. A simple parameterisation of the effects of PAR on GPP of and air
temperature on ecosystem respiration, suggest that a rise in air temperature of 1°C
between 2012 and 2065 could lead to a 73% increase in the carbon sink strength of the
peatland, provided hydrological conditions remain unchanged. This demonstrates that
climate change is not likely to change this peatland into a carbon source by 2100. |
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