Pedogenetic processes, soil hydrology and erosion along a soil catena in the Turbolo watershed (northwest Calabria, southern Italy)

This work focuses on the analysis of a soil catena in the Turbolo watershed (NW Calabria, southern Italy), which is representative of widespread zones in this region and in the Mediterranean area, in terms of lithological, geomorphological, pedological and climatic features, and high susceptibility to soil erosion. The Turbolo stream is a left tributary of the Crati river and drains Palaeozoic metamorphic rocks in its western, high-relief, steep sector and Neogene-Quaternary sedimentary terrains in its eastern, hilly, gentler reaches, respectively ranging from about 1015 to 75 m asl. The soil toposequence investigated consists of six soil profiles on an abandoned agricultural land. They developed on Pleistocene marine silty-clays along a N-facing slope, ranging between 85 and 140 m asl in elevation and 5 to 20° inclined, affected by sheet wash, rill and occasional gully erosion. The soil profiles represent Inceptisols with varying juxtaposition of Ap, Bw and Bg horizons, some vertic properties and poor CaCO3 dynamics. A multidisciplinary approach was applied, spanning from geomorphological and pedological field observations, in situ infiltrometric measurement of hydrological properties, Mercury intrusion porosimetry and chemical-physical laboratory analyses, micromorphological study of thin sections obtained from undisturbed soil samples. The main soil features clearly highlight changes in intensity of major morphodynamic processes along the slope (erosion and reworked soil accumulation), testified by topsoil truncation, varying organic matter and carbonate content. Some interesting relationships are evidenced among particle size distribution, hydraulic conductivity, estimated microporosity, pore size and their effects on water infiltration or runoff and soil erosion.