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| Titel |
Understanding the erosion of semi-arid landscapes subject to vegetation change: a combined approach using monitoring, isotope and 14C analysis |
| VerfasserIn |
R. E. Brazier, L. Turnbull, R. Bol, L. Dixon, J. Wainwright |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250031542
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| Zusammenfassung |
| The degradation of grasslands is a common problem across semi-arid areas worldwide. Over
the last 150 years much of the South-Western USA has experienced significant land
degradation, with desert grasslands becoming dominated by shrubs and concurrent changes in
runoff and erosion which are thought to propagate further the process of degradation.
Field-based experiments were carried out to determine how runoff and erosion vary at stages
over a transition from a black grama (Bouteloua eriopoda) grassland to creosotebush (Larrea
tridentata) shrubland at the Sevilleta NWR LTER site in New Mexico. 14C and δ13C
analyses were carried out to investigate the age and potential provenance of eroded
sediment.
Results show an overall increase in runoff and erosion over the transition from grassland to
shrubland, associated with an increase in connectivity of bare, runoff-generating areas,
although these increases do not appear to follow a linear trajectory. Erosion rates increased
over the transition from grassland to shrubland, related in part to changes in runoff
characteristics and the increased capacity of the runoff to detach, entrain and transport
sediment. Over all plots fine material was preferentially eroded which has potential
implications for nutrient cycling since nutrients tend to be associated with fine sediment.
There are significant differences in the isotopic signatures of eroded sediment between the
grass- and shrub-dominated plots. The positive correlation between event runoff and
δ13C signatures of eroded sediment that is consistent over plots 1, 3 and 4 suggests
that the δ13C signatures can be used to distinguish between changes in erosion
dynamics over events of different magnitudes and over different vegetation types. 14C
analysis of sediment revealed that sediment eroded from all plots is considerably
younger than the surface soils over all plots, which is likely to indicate that eroded
sediments tend to source form very near surface areas that are enriched by the bomb
spike (>105% modern), but also contain a mixture of eroded soils which are less
enriched. |
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