Complex climate-induced changes in soil development as markers for the Little Ice Age in the Northern Apennines (Italy)

In the Northern Apennines the effects of the Little Ice Age (LIA) on the mountain landscape are poorly known. A pedosedimentary sequence on the northern slope of Mt. Cusna (Tuscan-Aemilian Apennines) and its geomorphological setting were investigated in order to assess the influence of the LIA on the soils and the geomorphological processes. The upper portion of the described sequence could be interpreted as colluvial deposits burying an old paleosurface. The LIA climatic effects acted on the sequence in two distinct phases: in a first moment, partial denudation of the surfaces allowed direct daily and seasonal freeze-thaw cycles (i.e. frost action) to produce ice-related relict microscopic pedofeatures in the soil horizons constituting the paleosurface, and absent on modern surfaces. Afterwards, a slope instability phase, possibly caused by the change to wetter conditions, promoted the widespread colluvial deposits, which were later partially reworked by frost in solifluction lobes. The triggering of these events seems to be influenced by the presence of pastoral communities, too: charcoals found on the paleosurface point to the use of fire events for clearance practices and, possibly, later pasture exploitation of the surfaces. In this light, the environmental history recorded by the Mt. Cusna pedosedimentary sequence highlights how LIA was fundamental in shaping the modern landscape of the N Apennines and suggests a complex relationship between climate and human forcing on mountain environments.