SCHRIFTENREIHE Institut für Pflanzenernährung und Bodenkunde ...

(Type ML2x, Delta-T Devices, Cambridge, UK) that were calibrated for the soil
and inserted into the surface at each point. In total, measurements were made at
52 different times.
Soil water content was compared to other properties that were anticipated to
influence water transport and storage. At least 3 times during the growing
season the following measurements were made in situ. Shear strength was
measured with a hand-held shear vane tester (Geonor H-60, Norway). Water
repellency was estimated with the water drop penetration time (WDPT) test, by
measuring the time taken for a 0.5 mm 3 drop of water to enter the soil. A longer
time indicates greater water repellency. Hydraulic conductivity was measured
using a Mini-disk Infiltrometer (Decagon devices, USA) at a suction value of 0.5
cm.
Once each year, in July or August, the vegetation coverage was analyzed
using a non-destructive method based on Braun-Blanquet (1964). Aboveground
biomass was sampled on 0.25 m x 0.25 m plots by cutting plant at 10 mm height,
including the standing dead material. At the first sampling time in 2004, 0-4 cm
depth samples were taken for soil organic carbon determined in duplicate by dry
combustion on a Vario Max CNS elemental analyzer (Elementar
Analysensysteme GmbH, Hanau), and soil texture with the pipette method.
Intact soil cores, 56 mm diameter x 40 mm heigh were taken for bulk density and
water retention. The cores were dried to pF 1.8 (field capacity) on a sand table
and 4.2 (wilting point) on a pressure plate to describe water retention. The main
mean characteristics (100 points) for each plot are described in Table 1.
A terrain elevation model was derived from Real Time Kinematic dGPS
(RTK-GPS) measurements with a lateral resolution of 2 m and vertical resolution
of 0.1 m. Using this information, topographical variables such as slope, aspect,
curvature, and upslope contribution area were computed using ArcGIS
(Johnston, et al., 2001). A wetness index, which is a surrogate for lateral
subsurface flow process, was also derived. This index was defined as ln(α/tanβ),
where α is the upslope contribution area and β is the local slope angle
(Gómez-Plaza, et al., 2001).
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