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| Titel |
Soil temperature synchronisation improves estimation of daily variation of ecosystem respiration in Sphagnum peatlands |
| VerfasserIn |
Benoît D'Angelo, Sébastien Gogo, Franck Le Moing, Fabrice Jegou, Christophe Guimbaud, Fatima Laggoun |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250101715
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| Publikation (Nr.) |
 EGU/EGU2015-906.pdf |
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| Zusammenfassung |
| Ecosystem respiration (ER) is a key process in the global C cycle and thus, plays an
important role in the climate regulation. Peatlands contain a third of the world soil C in spite
of their relatively low global area (3% of land area). Although these ecosystems represent
potentially a significant source of C under global change, they are still not taken into
account accordingly in global climatic models. Therefore, ER variations have to
be accounted for, especially by estimating its dependence to temperature.s The
relationship between ER and temperature often relies only on one soil temperature
depth and the latter is generally taken in the first 10 centimetres. Previous studies
showed that the temperature dependence of ER depends on the depth at which the
temperature is recorded. The depth selection for temperature measurement is thus a
predominant issue. A way to deal with this is to analyse the time-delay between ER and
temperature. The aim of this work is to assess whether using synchronised data in
models leads to a better ER daily variation estimation than using non-synchronised
data.
ER measurements were undertaken in 2013 in 4 Sphagnum peatlands across France: La
Guette (N 47°19’44”, E 2°17’04”, 154m) in July, Landemarais (N 48°26’30”, E -1°10’54”,
145m) in August, Frasne (N 46°49’35”, E 6°10’20”, 836m) in September, and Bernadouze
(N 42°48’09”, E 1°25’24”, 1500m) in October. A closed method chamber was used to
measure ER hourly during 72 hours in each of the 4 replicates installed in each site. Average
ER ranged from 1.75 μmol m-2 s-1 to 6.13 μmol m-2 s-1. A weather station was
used to record meteorological data and soil temperature profiles (5, 10, 20 and 30
cm).
Synchronised data were determined for each depth by selecting the time-delay leading to the
best correlation between ER and soil temperature. The data were used to simulate ER
according to commonly used equations: linear, exponential with Q10, Arrhenius, Lloyd
and Taylor. Models comparison was performed using RMSE (goodness-of-fit) and
AIC (goodness-of-fit and model complexity) as indicators to assess their relative
quality.
Both indicators showed a wide variation between sites. However, for each site differences
between synchronised and non-synchronised data were larger than the differences between
models equations. According to the AIC, models using synchronised data produced better ER
estimations than models using non-synchronised data, at all depth. RMSE support
this result for all sites for superficial peat layer. In some locations, mainly Frasne,
synchronised data at 5 cm depth provide better estimation than air temperature, i.e.Â25.0
vs. 26.4 for RMSE and 337.1 vs. 379.8 for AIC, respectively. The equation of the
most appropriate model varies between sites, but the differences between them are
small.
At a daily scale, data synchronisation in Sphagnum peatlands improves ER estimation
regardless of the model used. Moreover, to estimate ER flux, the use of synchronised data at 5
cm depth seems the most adequate method. |
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