Geostatistical Tools for Characterizing the Spatial Variability of Soil Water Repellency Parameters in a Laurel Forest Watershed

摘要

Soil water repellency is recognized to be a widespread phenomenon which may affect a wide range of spatially dependent hydrological processes that take place in the vadose zone such as infiltration, preferential flow, and soil water distribution. Despite this, the spatial structure of soil repellency has received almost no attention in the past. The objective of this study is to investigate the spatial variability of water repellency in the top horizon of a laurel forest watershed. Water repellency was measured with the molarity of an ethanol droplet (MED) test, from saturation to oven-dry, in 140 soil samples taken in a nested structure that encompasses both short (centimeter scale) and long (meter scale) distances. Geostatistical tools such as correlograms and kriging were used to quantify the spatial structure of soil organic matter (SOM) content and the parameters that characterize the water repellency curve. Both showed characteristic spatial trends, and, in general, spatial correlation followed a spherical, exponential, or gaussian model. All parameters investigated exhibit scale dependence, in particular, variability of SOM and the area below the repellency curve point toward a self-similar fractal scaling. Cross-correlation of some of the repellency parameters and SOM was not random but showed spatial structure.