This dataset represents the actual SOC (Soil Potential Carbon) stock for topsoil as calculated after processing spatial data from various databases of soil profiles reporting necessary information (i.e. C concentration, bulk density, rock fragments, horizon depth) and creating a spatialized solid baseline given by the combination of characteristics as soil type, land use and climate zoning. Classes of stock are as below: - Very low (<15 Mg/ha); - Low (15-40 Mg/ha); - Medium (40-70 Mg/ha); - High (70-140 Mg/ha); - Very high (>140 Mg/ha).

This field gives the percentage of organic carbon in the subsoil. Organic Carbon is together with pH, the best simple indicator of the health status of the soil. Moderate to high amounts of organic carbon are associated with fertile soils with a good structure. Soils that are very poor in organic carbon (<0.2%), invariable need organic or inorganic fertilizer application to be productive. Soils with an organic matter content of less than 0.6% are considered poor in organic matter. The following classes are suggested to prepare maps of organic carbon status for mineral soils: Code Percentage organic carbon 1 < 0.2 2 0.2 – 0.6 3 0.6 – 1.2 4 1.2 – 2.0 5 > 2.0

This dataset represents the potential GAP in SOC (Soil Potential Carbon) stock for topsoil in 2050 (medium term) under B1 IPCC emission scenario. GAP is expressed in terms of class differences between ACTUAL and POTENTIAL topsoil carbon sequestration under the same scenario ans time frame.

Reference Bulk Density of topsoil.Reference bulk density is a property of particulate materials. It is the mass of many particles of the material divided by the volume they occupy. The volume includes the space between particles as well as the space inside the pores of individual particles. The calculation procedures for reference bulk density can be found at http://www.pedosphere.com/resources/bulkdensity/index.html Bulk density, as a soil characteristic, is a function rather than a single value (USDA-NRCS, 2004 #3078, p. 73) as it is highly dependent on soil conditions at the time of sampling: changes in (field) water content will alter bulk density. The SOTWIS database provides estimates of bulk density values derived from available analyzed data, and thus consider differences in soil texture, organic matter content and porosity. Careful review of these values also by comparison with calculated reference bulk densities has revealed substantial differences. For reasons of data quality and consistency of the HWSD, reference bulk density values – calculated using equations developed by Saxton et al. (1986), have been used here: these equations represent a statistical estimate and reflect only the textural influence.

Volume percentage gravel respectively in the topsoil. Gravel stands for the percentage of materials in a soil that are larger than 2 mm.

This dataset represents the potential SOC (Soil Potential Carbon) stock for topsoil in 2100 (long term) under B1 IPCC emission scenario. It is function of re-spatialization of mean actual SOC stock for topsoil according to changes in land use and climate zone in 2100 under B1. Classes of stock are as below: - Very low (<15 Mg/ha); - Low (15-40 Mg/ha); - Medium (40-70 Mg/ha); - High (70-140 Mg/ha); - Very high (>140 Mg/ha).

This dataset represents the potential SOC (Soil Potential Carbon) stock for topsoil in 2050 (medium term) under B1 IPCC emission scenario. It is function of re-spatialization of mean actual SOC stock for topsoil according to changes in land use and climate zone in 2050 under B1. Classes of stock are as below: - Very low (<15 Mg/ha); - Low (15-40 Mg/ha); - Medium (40-70 Mg/ha); - High (70-140 Mg/ha); - Very high (>140 Mg/ha).

This dataset represents the potential GAP in SOC (Soil Potential Carbon) stock for topsoil in 2050 (medium term) under A1FI IPCC emission scenario. GAP is expressed in terms of class differences between ACTUAL and POTENTIAL topsoil carbon sequestration under the same scenario ans time frame.

Percentage sand in the in the topsoil. Sand comprises particles, or granules, ranging in diameter from 0.0625 mm (or 1⁄16 mm) to 2 millimeters. An individual particle in this range size is termed a sand grain. Sand feels gritty when rubbed between the fingers (silt, by comparison, feels like flour). Sand is commonly divided into five sub-categories based on size: very fine sand (1/16 - 1/8 mm diameter), fine sand (1/8 mm - 1/4 mm), medium sand (1/4 mm - 1/2 mm), coarse sand (1/2 mm - 1 mm), and very coarse sand (1 mm - 2 mm).

This field gives the cation exchange capacity of the clay fraction in top-soil. The type of clay mineral dominantly present in the soil is often characterizes a specific set of pedogenetic factors in which the soil has developed. Tropical, leaching climates produce the clay mineral kaolinite, while confined conditions rich in Ca and Mg in climates with a pronounced dry season encourage the formation of the clay mineral smectite (montmorillonite).