INVESTIGATIONS ON THE RELATIONSHIPS BETWEEN SOIL CHARACTERISTICS, TOPSOIL ERODIBILITY AND HILLSLOPE FEATURES IN THE RIVO CATCHMENT (MOLISE, SOUTHERN ITALY)

Soil erosion is one of the main environmental problems in the Mediterranean area. This problem is becoming even more important especially in the Apennines, where several erosive processes, frequently favoured by intensive land use, occur due to the action of running water. To investigate on the relationships between soil characteristics and local morphologic-topographical features, a study was carried out in the southern part of the Rivo catchment which is located in Molise region within the middle Trigno valley. Here, a soil “catena” was constructed along which soil profiles where examined as to their main physical and chemical parameters such as thickness, structure and texture. In the study area, also a systematic sampling of topsoil was performed to individuate and evaluate by means of geostatistical techniques the relationships between soil erodibility and superficial soil structure, texture and organic matter content. The results obtained from the analyses on topsoil samples were then compared with those of the catena, as well as with several morphometric slope indexes, automatically extracted from a Digital Terrain Model (DTM). The performed cross analyses have given clear evidence about the relation between investigated topsoil characteristics and morphometric indexes. On particular, the differences in topsoil features appear to be directly related to slope morphology and to the specific morphodynamic features which characterise the distinguished morphologic units present in the study area. The observed relationships reflect the possibility to better evaluate both the soil erodibility factor (K) used within the USLE equation and the spatial variability of physical and chemical soil characteristics on the basis of digital terrain analyses, and so better predict soil loss rates. The presented methodology, if further verified, may significantly contribute to facilitate studies on soil erosion when the required data on soil properties are too expensive or difficult to be acquired by means of traditional field and laboratory approaches.