Soil carbon stock in relation to soil properties and landscape position in a forest ecosystem of southern Italy (Calabria region)

Carbon (C) storage in forest soils is of great importance both to forest ecosystems and to reduce the CO2 in atmosphere.Knowledge of spatial pattern of soil organic carbon (SOC) and the factors influencing it in various soil-landscapes areessential for understanding global C cycle.The objective of this study was to investigate at profile scale SOC stock in a forested area of southern Italy (Calabria)in relation to soil properties and landscape position. Twenty-eight soil profiles were sampled to cover all soil types andphysiographic units of the study area and each horizon was sampled and characterized for its physical-chemical properties(bulk density, texture, pH, SOC, and nitrogen). Moreover, the organic horizon (O) was sampled and SOC concentrationwas determined. Then, the SOC stock for the organic layer and mineral horizons was calculated.Soils developed in the study area belong to the Inceptisol and Entisol orders varying from shallow to moderately deep,with chemical and physical characteristics mainly controlled by granitic parent rock. SOC stock for the organic layer variedfrom 3 Mg ha- 1 to 6 Mg ha- 1 whereas for mineral horizons ranged between 20.2 Mg ha- 1 and 310.9 Mg ha- 1.The results showed a different behaviour of physical-chemical properties and carbon storage for coarse-textured soilsand more fine-textured soils. In addition, soil types and topographic features such as slope gradient, slope curvature andlandscape position controlled SOC stored in mineral horizons through changes in both in-depth variability of SOC concentrationand profile thickness. In particular, higher SOC stocks were recorded in flat areas than on steep slopes, andInceptisols developed on slopes with concave morphology exhibited higher values than Entisols located on convex slope.