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| Titel |
Soil organic carbon fractions in uncultivated and tilled profiles of mountain Mediterranean agroecosystems. |
| VerfasserIn |
Laura Quijano-Gaudes, Leticia Gaspar, Ana Navas |
| Konferenz |
EGU General Assembly 2011
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250055801
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| Zusammenfassung |
| In the global carbon cycle, one of the most important terrestrial pools for carbon storage
and exchange with atmospheric CO2is the soil organic carbon (SOC). SOC can be
fractionated into two main pools according to the chemical stability and the turnover
times. The labile carbon pool is easily degraded and the recalcitrant carbon pool is
more stable and because of its much slower turnover time is particularly relevant to
the role of soil as a long-term terrestrial C sink. The purpose of this study was
to investigate the content and depth distribution of SOC and its pools in selected
cultivated and uncultivated soil profiles representing eroding, aggrading and stable
sites. Representative soil profiles of Regosols and Calcisols were collected in a
typical mountain agroecosystem of NE Spain (42º 01’ 42”N, 0º 31’ 30”E) with
continental-mediterranean climate and mean annual rainfall of around 500 mm. Soil
redistribution patterns at the selected sites were characterized using fallout 137Cs radiotracer
that allowed distinction of stable, eroded and deposition profiles. Nine profiles were
in uncultivated soils (3 eroded, 3 deposition and 3 stable sites), 6 profiles were
in cultivated soils (3 eroded and 3 deposition sites). A total of 112 samples were
analysed for the content of SOC and the two organic pools, labile and recalcitrant
carbon were measured by dry combustion method using a Leco RC-612 multiphase
analyser on a sub-sample of the dried interval soil sample. The results indicate that in
uncultivated profiles the content of SOC was highest in the surface layers and decreased
with depth, following a similar pattern to that of 137Cs. In cultivated profiles such
distribution was not evident due to mixing by tillage. In all soil samples the content of
labile carbon was higher than the recalcitrant carbon. The content of SOC was
highly variable and ranged between 0.09 and 6.91% (mean: 1.69% ± 1.23). The
percentage of labile carbon showed also large variations from 0.09 to 5.77% (mean:
1.10% ± 0.89), while the recalcitrant carbon varied less between 0.09% and 1.47%
(mean: 0.55% ± 0.38). The content of labile and recalcitrant carbon in uncultivated
profiles was significantly higher (p -¤ 0.05) than in cultivated profiles. In uncultivated
soil profiles identified with 137Cs as deposition sites, the content of recalcitrant
carbon was slightly higher than in soil profiles affected by erosion. Soil redistribution
in non-tilled soils would have implications for the capacity of soils to sequester
carbon. The results suggest that the content of labile and recalcitrant carbon in
soils are strongly affected by the land use. Further research has to be done for a
better understanding of the role of erosion and sedimentation in the distribution
patterns of soil organic carbon fractions which is of interest for a better description
of the processes involved in SOC dynamics in Mediterranean agroecosystems. |
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