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 soillandscapesare essential 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 profileswere sampled to cover all soiltypes and physiographic units of the study area and each horizon was sampled and characterized for its physicalchemicalproperties (bulk density, texture, pH, SOC, and nitrogen). Moreover, the organic horizon (O) was sampledand SOC concentration was determined. Then, the SOC stock for the organic layer and mineral horizonswascalculated.Soils developed in the study area belong to the Inceptisol and Entisol orders varying fromshallow to moderatelydeep, with chemical and physical characteristics mainly controlled by granitic parent rock. SOC stock for the organiclayer varied from3Mg ha−1 to 6Mg ha−1 whereas for mineral horizons ranged between 20.2Mgha−1 and310.9 Mg ha−1.The results showed a different behaviour of physical-chemical properties and carbon storage for coarse-texturedsoils and more fine-textured soils. In addition, soil types and topographic features such as slope gradient, slopecurvature and landscape position controlled SOC stored in mineral horizons through changes in both in-depthvariability of SOC concentration and profile thickness. In particular, higher SOC stocks were recorded in flatareas than on steep slopes, and Inceptisols developed on slopes with concave morphology exhibited highervalues than Entisols located on convex slope.