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| Titel |
Investigating land use effects on soil hydrology in alpine ecosystems by stable isotopes |
| VerfasserIn |
Matthias H. Mueller, Christine Alewell |
| 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 |
250046823
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| Zusammenfassung |
| Soils in mountain areas are an important factor for hydrological ecosystem services of a
region (e.g. drinking water reservoirs and flood prevention). Changes in land use are currently
affecting mountain soils inducing a change not only in biogeochemical cycles, slope stability,
vegetation productivity, ecosystem biodiversity and nutrient production but also in water
budgets and flow paths. The main changes in land use in the Swiss Alps are reduced farming
activities, which have led to massive shrub encroachment and forest expansion into
formerly open habitats, particularly at higher elevations. These land use changes affect
the hydrology of soils and adjacent lowlands. In our test region, the Ursern Valley
in the Swiss Central Alps, we assess the status and current change of vegetation
cover, its influence on soil characteristics, and their combined effects on the soil
water balance and soil integrity. Water balance might be affected by green alder
shrubs with increased interception, evapotranspiration and infiltration compared to
grasslands. Further, green alders can be expected to alter soil physical and chemical
properties.
In four micro catchments (< 1 km2) with different percentage of green alder cover we
investigate how the expansion of green alder affects the soil hydrology. We directly compare
soil hydrological parameters of green alder and grass land sites. Investigated soil hydrological
parameters include volumetric soil water content to estimate water infiltration, surface flow
and soil erosion, soil bulk density, and water residence times in soils. The latter will be
studied by a stable isotope approach (18O and 2H in water). With weekly stable isotope data
of precipitation and runoff we will model water residence times. In addition, we applied a soil
water stable isotope sampling along a transect of a grass land site to study water flow
processes.
The stable isotopes of soil water confirmed our findings from the volumetric
soil water content data that water infiltration rates are rather high. Moreover, we
could infer from the soil water depth profiles that vertical infiltration processes are
dominating even at high slope angles. Lateral flow processes at lower slope angles
were observed to a smaller degree. Our results from the first year of precipitation
and stream water stable isotope sampling show that, the micro catchments have
high water residence times despite their small size. The latter might point to deep
flow paths with the infiltrating precipitation percolating through deeper carbonate
rich rock layers which underlie the gneiss parent material. Our stream water pH
measurements in these micro catchment (pH was 7-8) support this conclusion. |
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