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| Titel |
Stable isotopes as indicators for long term soil degradation |
| VerfasserIn |
Katrin Meusburger, Franz Conen, Christine Alewell |
| 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 |
250092609
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| Publikation (Nr.) |
 EGU/EGU2014-6965.pdf |
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| Zusammenfassung |
| We summarize the results of several studies that explored the suitability of stable isotope as
indicators for soil degradation. Two approaches to indicate soil degradation were tested. The
first one aims to identify soil erosion in hill slope transects from uplands (erosion source, oxic
soils) to adjacent wetlands (erosion sink, anoxic soils) as it often occurs in mountain
environments. The second aims at identifying long-term disturbance of oxic soils through
decreasing correlations between δ13C and soil organic carbon (SOC), δ15N and N content,
and δ15N and C:N ratio.
Following the first approach, different stable isotope signatures can be expected for uplands
and adjacent wetland soils. In our study, δ13C of SOC in wetland soils was with
-28.3 ± 0.6 olighter than those of upland soils (-26.6 ± 0.6 o). Soil erosion is
indicated by intermediate δ13C values (-27.5 ± 0.5 o) of the wetland soil. Analogue
oxic upland soils and wetlands not affected by soil erosion also differed in δ18O
values. The upper horizons (0–10 cm) of upland soils had a mean δ18O between 5
and 15 o, while δ18O signatures of reference wetland soils varied between 15
and 20 o. Intermediate δ18O values for wetland soils adjacent to an upland can
consequently be interpreted as mixing of soil erosion material with the organic wetland
soil.
Following the second approach, ‘stable’ landscape positions (reference sites), which are
neither affected by erosion nor deposition are compared with disturbed sites. For
undisturbed soils we expect that the enrichment of 15N and 13C with soil depth, due to
fractionation during decomposition, goes in parallel with a decrease in N and SOC
content. In the Swiss Alps, the soil profiles of the reference sites showed significant
correlations between SOC content and its corresponding 13C signature. In contrast, for
the eroding sites this relationship was not significant. The usefulness of the stable
carbon isotope signature as a qualitative indicator for soil disturbance could be
confirmed for a mountain site in South Korea. For the Korean site, we could further
show that the 15N isotope signature can be used similarly for uncultivated sites.
Further, δ15N is functionally related to the C:N ratio. In unperturbed sites δ15N
values cover a relatively narrow range at any particular C:N ratio in soils within a
large geographical region. Substantial loss, or gain of N, mostly results in the loss
or gain of 15N-depleted forms. The latter results in larger or smaller δ15N values
than usual at the observed C:N ratio and can serve as a soil disturbance indicator. |
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