Reforestation and soil recovery in a Mediterranean mountain environment: Insights into historical geomorphic and vegetation dynamics in the Sila Massif, Calabria, southern Italy

[Display omitted] •Severe land degradation affected the Sila Massif (south Italy) until the late 1950s.•Reforestation promoted biomass increase and slope stabilization even on steep slopes.•Shallow A horizons formed by humus accumulation under reforested stands.•Topsoils are enriched in 210Pbex and 137Cs, favored by tree canopies interception.•Gamma-emitting radionuclides in the soil profiles show overall low hazard potential. We investigated the genesis and local response of soils in mountain sites of the Sila Massif (Calabria, southern Italy), reforested ca. 60 years ago, and their relationships with geomorphic dynamics and forest stand structure. A multidisciplinary approach is proposed, focused on an often neglected soil profile scale and horizon-wise sampling strategy, and including pedological field observations, physical, chemical, mineralogical analyses, isotope geochemistry including fallout radionuclides (137Cs and 210Pbex), geomorphology, historical documentation of anthropogenic land cover changes, forestry and dendrometric measurements. Reforestation was carried out following extreme land degradation, which took place after forest clearance and field cultivation. Different tree species and soil preparation techniques were used according to site conditions. We focused on the main properties of selected soil profiles and the distribution of some radionuclides, in order to understand the effects of forest stands on hampering soil erosion and promoting novel soil formation, and to evaluate the potential hazard of natural gamma radiation. A comparison with soil profiles developed under naturally regenerated forest and field crops was achieved. The soil profiles in reforested sites showed a poor degree of development and a complex history of reworking processes alternated with soil-formation processes, in line with modern to historical radiocarbon dates increasing downprofile, the presence of buried horizons and 137Cs in the topsoils. Inventory changes obtained for 210Pbex and 137Cs highlight a process of soil stabilization occurred after reforestation, with more efficient effects under Calabrian pine than oak forest, whereas major geomorphic dynamics (erosion and accumulation) were triggered by forest coppicing, thinning and agricultural practices. Our data remark a positive response of the soil ecosystem to reforestation against erosion, trapping mobile material, stabilizing buried soils, promoting humus accumulation leading to new shallow topsoil