Integrating Geostatistics and GIS for Assessment of Erosion Risk on Low Density Quercus suber Woodlands of South Portugal

Abstract

This research integrates the Revised Universal Soil Loss Equation (RUSLE) with geostatistical techniques and a Geographic Information System (GIS) to model erosion potential for soil conservation planning in Quercus suber agrosilvopastoral woodlands in the Algarve region of southern Portugal. Graphical interpretation of the RUSLE parameters was performed using ordinary kriging. Semi-variograms were produced for each parameter. The maps resulting from the interpolation techniques were introduced in a GIS and their values reclassified. After that, spatial modelling was used to develop the final overlay map from all the information of the analyzed soil properties and RUSLE parameters, simulating “a potential soil erosion map.” Hydraulic conductivity and the soil erodibility K factor with a nugget-to-sill ratio of 57% and 67%, respectively, showed the weakest spatial dependence, whereas organic matter demonstrated the strongest (31%). The maps created demonstrate the existence of a heavily textured area in the southern part of the site that could affect erosion and vegetation management techniques. Hydraulic conductivity was higher than 6 cm/h in the northeastern part of the experimental area. The correlation between the spatially interpolated and observed values during the semi-variogram cross-validation, using the data set for method development, was high (r2 > 0.81). The northwestern area was the most adequate for annual fodder cultivation. The most degraded and less suitable areas were in the southern part, with 108 t/ha potential erosion. Site-specific management methods could improve productivity and decrease the risk of erosion. The present research shows that geostatistics and GIS are useful tools for sustainable management of extensive agrosilvopastoral areas.