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| Titel |
Effect of the vegetation cover on the 137Cs soil redistribution rates in Mediterranean slope transects |
| VerfasserIn |
Leticia Gaspar, Ana Navas, Javier Machín |
| 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 |
250055273
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| Zusammenfassung |
| Soil degradation due to water erosion is considered as one of the major environmental
problems for the preservation of soil which is required to support biodiversity. Vegetation
cover is widely recognized as one of the main factors controlling soil erosion and its
maintenance is vital for the sustainability of fragile ecosystems. In the study reported in this
contribution, soil redistribution was estimated along slope transects of a subhumid
Pre-Pyrenean catchment. The artificial radionuclide 137Cs coming from nuclear tests was
applied to assess soil erosion and deposition along two transects with contrasting
land use and vegetation cover. A total of 19 soil sectioned cores were collected
along two slope transects. The northern transect consists of 7 cores along 300 m
length and the western transect provided 12 cores along 600 m length. Models
reported by Soto and Navas (2004, 2008) were used to estimate soil redistribution
rates (t ha-1 y-1) based on 137Cs for individual sampling points. Assuming that
each transect represents a 1 m wide strip, the rate values for each sampling point
were used to calculate equivalent values of soil loss or deposition (kg y-1) for
individual slope segments with similar vegetation cover. The resulting values for
each segment were summed to provide a sediment budget for the overall transect,
comprising information on the total erosion, total deposition, net soil loss, sediment
delivery ratio and net rates of soil loss for each of transect. The northern transect
(11% slope) has a relict of forest of Quercus coccifera in the upper and middle
part of the transect and 43% of its surface was originally cultivated, but was then
abandoned and at present supports a natural sparse shrubland vegetation. The total
erosion estimated for this transect was 75 kg y-1 and total deposition was 28 kg y-1,
representing a sediment delivery ratio (SDR) of 63%. The western transect T4 (17%
slope), with 15% of abandoned terraced fields but predominance of cultivated land
(58%) had a total erosion estimated at 1008 kg y-1, and total deposition at 193
kg y-1, representing a SDR of 81%. The northern transect, where the surface of
abandoned land has naturally recovered, showed much lower values of net soil loss
in comparison with the western transect, where predominance of cultivated land
largely increased soil erosion resulting in higher SDR. The results suggest that
vegetation cover together with tillage are key factors affecting the pattern of soil
redistribution in the transects. Cultivation increases soil losses because in the study area in
addition of tillage erosion there is documented coincidence of intense rain events
when soils are bare after harvest and during sowing periods. In the transects, the
vegetation cover not only prevents soil erosion but affects sedimentation patterns as
vegetation strips contributed to trap sediments. The assessment of soil redistribution
rates under different land uses and vegetation cover is of importance for a better
understanding of the factors involved in the functioning of Mediterranean agroecosystems. |
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