Land-use
change in the humid tropics alters soil hydraulic parameters which may change near-
surface hydrologic flow paths. In southern
Soil saturated
hydraulic conductivity (Ks) is a sensitive indicator to assess those changes
regarding soil hydrology. We measured Ks in situ at soil depths of 12.5, 20,
and 50 cm (n=150/depth) under landslides of different ages (0 to 30 years),
under actively grazed pasture, fallows following pasture abandonment (2 to 25
years of age), and under natural forest. The results can be related to prevailing
rainfall intensities to diagnose the possible occurrence of an impeding layer
at a shallow soil depth. Additionally, we analyzed the data for spatial autocorrelations
using geostatistical tools.
Results
from the human – induced disturbance regime show an enormous decrease of Ks
after forest conversion to pasture at shallow soil depths, and a slow
regeneration after pasture abandonment. However, the reduced permeability
hardly causes an alteration of the prevailing vertical flow paths, since local rainfall
intensities are predominantly low. In contrast, Ks does
not differ among landslides and in comparison to the natural forest which
suggests a marginal effect of landslide activity in this region on soil
hydrology.
Geostatistical analyses reveal spatial autocorrelations of Ks including anisotropy for
the old fallow and natural forest; variograms for
pasture, a young fallow and a landslide show pure nugget effects. Hence, any
spatial structure of Ks is likely to disappear under disturbed land covers and
may be restored during regeneration.