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| Titel |
137Cs re-sampling as a method for soil erosion assessment in Alpine grasslands |
| VerfasserIn |
Laura Arata, Katrin Meusburger, Nicole Bissig, Lionel Mabit, 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 |
250089167
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| Publikation (Nr.) |
 EGU/EGU2014-3360.pdf |
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| Zusammenfassung |
| Over the past decades, radioactive fallout 137Cs has been used as a tracer to provide
information on soil erosion and sedimentation rates. However, the method may produce
relatively large uncertainties in Alpine grasslands. The latter difficulties are caused by a
combination of (i) the heterogeneous distribution of atmospheric 137Cs Chernobyl fallout, (ii)
the partly snow covered ground in Alpine areas during the fallout event in April 1986, which
results in inhomogeneous 137Cs distribution during snow melt and (iii) uncertainties in
finding undisturbed references sites in the geomorphological and anthropogenic highly active
slopes of the Alps.
To overcome these difficulties, our aim is to replace the classical 137Cs approach, where
an undisturbed reference site is compared to erosional sites, with a re-sampling approach,
where we re-sample sites which have already been measured for 137Cs inventories in the past.
Thus, we use temporal instead of spatial reference.
The study area is located in the Central Swiss Alps in the Urseren Valley. Potential
erosional sites have been sampled in 2007 and re-sampled in 2012. Two different
grassland types were investigated: hayfield (2 sites) and pasture without dwarf shrubs (3
sites). For each site, 4 to 9 sampling points have been defined, and at each point
two soil samples have been collected. To reduce the random error, the two soil
samples were bulked prior to gamma-analysis. 137Cs inventories of the two sampling
years were calculated and used to assess recent soil erosion in the experimental
sites.
Our results show that within the 5 years measurable soil erosion and deposition processes
have occurred within the sites, as indicated by the relevant difference between the
137Cs inventories of 2007 and 2012. 64% of the sites exhibit a decrease in 137Cs
inventories, 20% of the sites an increase, and the remaining 16% no significant difference.
In particular, hayfield sites have been affected by erosion processes, mostly due
to high snow glide and avalanche dynamic, whereas pasture inventories indicate
both deposition and erosion. Resulting re-sampling erosion rates for the period of
2007-2012 indicate high erosion rates of >20 t ha-1 yr-1, which confirm previous
studies.
The 137Cs re-sampling method has also been successfully tested to verify the
appropriateness of reference sites. Reference sites in the study area, defined and sampled
in 2010, have been re-sampled in 2013. Sites which did not show a considerable
difference in 137Cs inventories, may subsequently be used to apply the classical 137Cs
approach.
The 137Cs re-sampling approach represents an effective and reliable method to assess
short term erosion in Alpine grasslands, and a useful addition for the 137Cs classical
approach, in validating the suitability of reference sites. |
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