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| Titel |
Long-term steady state 13C labelling to investigate soil carbon turnover in grasslands |
| VerfasserIn |
K. Klumpp, J. F. Soussana, R. Falcimagne |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 4, no. 3 ; Nr. 4, no. 3 (2007-06-26), S.385-394 |
| Datensatznummer |
250001734
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| Publikation (Nr.) |
 copernicus.org/bg-4-385-2007.pdf |
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| Zusammenfassung |
We have set up a facility allowing steady state 13CO2 labeling of
short stature vegetation (12 m2) for several years. 13C labelling
is obtained by scrubbing the CO2 from outdoors air with a
self-regenerating molecular sieve and by replacing it with 13C depleted
(−34.7±0.03‰) fossil-fuel derived CO2 The facility, which
comprises 16 replicate mesocosms, allows to trace the fate of photosynthetic
carbon in plant-soil systems in natural light and at outdoors temperature.
This method was applied to the study of soil organic carbon turnover in
temperate grasslands. We tested the hypothesis that a low disturbance by
grazing and cutting of the grassland increases the mean residence time of
carbon in coarse (>0.2 mm) soil organic fractions.
Grassland monoliths (0.5×0.5×0.4 m) were sampled from high and low
disturbance treatments in a long-term (14 yrs) grazing experiment and were
placed during two years in the mesocosms. During daytime, the canopy
enclosure in each mesocosm was supplied in an open flow with air at mean
CO2 concentration of 425 µmol mol−1 and δ13C of
−21.5±0.27‰. Fully labelled mature grass leaves reached a δ13C
of −40.8 (±0.93) and −42.2‰ (±0.60) in the low and high
disturbance treatments, respectively, indicating a mean 13C labelling
intensity of 12.7‰ compared to unlabelled control grass leaves. After two
years, the delta 13C value of total soil organic matter above 0.2 mm
was reduced in average by 7.8‰ in the labelled monoliths compared to
controls. The isotope mass balance technique was used to calculate for the
top (0–10 cm) soil the fraction of 13C labelled carbon in the soil
organic matter above 0.2 mm (i.e. roots, rhizomes and particulate organic
matter). A first order exponential decay model fitted to the unlabelled C in
this fraction shows an increase in mean residence time from 22 to 31 months
at low compared to high disturbance. A slower decay of roots, rhizomes and
particulate organic matter above 0.2 mm is therefore likely to contribute to
the observed increased in soil carbon sequestration in grassland monoliths
exposed to low disturbance. |
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