Soils as a useful tool for reconstructing geomorphic dynamics in high mountain environments: The case of the Buscagna stream hydrographic basin (Lepontine Alps)

Abstract

The soil formation, its development, and its preservation in high mountain environments are largely determined by topography and geomorphological dynamic. Therefore, soil development in alpine areas is often non-linear over time, and characterized by phases of progressive and regressive evolution. The interaction among soil-forming factors is preserved in soils as physical/chemical properties and pedological features. In particular, the action of surface geomorphological processes can be observed as stone lines or sequences of buried surfaces. In this light, exhaustive investigation of soils and paleosols could provide enough information to reconstruct past environmental conditions and spatio-temporal changes in denudation/deposition processes.The main aim of this study is to assess the role of soil as a useful archive for retracing the geomorphological processes that are responsible for the landscape evolution during the Late Holocene in a typical alpine catchment such as the Buscagna stream hydrographic basin (Veglia-Devero Natural Park, Lepontine Alps). The asymmetry in valley slopes, due to lithology and structural control, generates a great variety of geomorphic processes and landforms. Therefore, seven soil profiles were selected along the two slopes, in different morphological contexts, to reveal the influence of the different active geomorphic processes in soil development. Soils were investigated by means of field and laboratory analyses, and geomorphological maps of the area surrounding the profiles were made. On the southeastern slope, characterized by calcschist substratum, the soil profiles are composed of two superimposed pedological units, separated by an instability hiatus. On the northwestern slope, characterized by gneiss and ultramafic rocks, and on the valley bottom, the soils record instability phases in different ways, fitting well with the geomorphological context. In this mountain environment, the close relationship between soil development and geomorphic processes allows us to confirm the role of soil as a useful archive to potentially reconstruct the past geomorphological conditions.