The Soils of the Portofino Promontory (NW Italy): distribution, genesis and paleoenvironmental implications

Abstract

The coverage of detailed soil maps is commonly limited in Italy, and the available regional soil inventories are not adequate for local land planning strategies. The aim of this research is to map the soil units in Portofino Natural Park using a Geographical Information System (GIS) approach. Soil micromorphology is used in conjunction with routine laboratory analyses to study several representative benchmark profiles in order to determine their genesis and to assess their palaeoclimatic significance. The spatial distribution and variability of the most extensive soil types were analysed using a GIS approach and were plotted in a 1:10,000-scale soil map with a descriptive legend. We identified six Reference Soil Groups: Cambisol, Regosol, Leptosol, Luvisol, Acrisol, and Umbrisol. The GIS database was then used to produce three derived maps: soil erodibility factor, spatial distribution of soil organic carbon (SOC) and Hydrologic Soil Groups. Deep and highly weathered soils were identified on an ancient erosional surface. These soils are relict palaeosols: they were generated through long-term pedogenesis but are no longer affected by active processes. The polygenetic development of these palaeosols was highlighted by micromorphological studies showing relict features that reflect climate conditions typical of past interglacial periods, which were warmer and more humid than today.