Soils of the European Union - European Soil Portal - Europa

4.3 AndosolsGeographical distributionAndosols cover some 0.21% of the surface of the EU (8,705 km 2 ). Large continuous areas with Andosols are found in theMassif Central of France, in the North-Eastern Carpathians in Romania and in the coastal volcanic areas of Sardinia andcontinental Italy. They form the dominant soil in 37 associations and occur as associated or inclusion soils in 22associations.Four soil units of the Andosol Reference Soil Group are present in the EU with Dystric Andosol occupying nearly half ofthe total area of Andosols (Table 4.3, Figure 4.3)Table 4.3 Area of the second level units of AndosolsUnits in the Reference Soil Groupin the EUCodes ofsoil unitsArea in the EUkm 2Dystric Andosol ANdy 3924Umbric Andisol ANum 2625Mollic Andosol ANmo 1224Vitric Andosol ANvi 932Dystric Andosols are dominant among the Andosols in France. They form inclusions in the Andosol-covered areas of theCarpathians and are also present in the Western Pyrenees. In regions of the EU where Andosols are present Umbric unitscan always be found in associations with other soils (with other units of Andosols as well!). On a continental scale MollicAndosols never dominate soil associations, however, they are present with considerably high share in Italy and as inclusionsoils in France. The overall situation of Vitric Andosols are similar to that of Mollic Andosols. However, besides beinginclusion soil in large regions of Italy, they are in association only in a very limited area in the Massif Central of France.10.71%14.06% 45.08% ANdyANumANmoANvi30.16%Global referenceFigure 4.3 Share of the second level soil units in the area of AndosolsAndosols are azonal soils developed on volcanic deposits and are found in all climates and at all altitudes in volcanicregions all over the world. The total Andosol area is estimated at some 1.1 million km 2 or less than 1% of the global landsurface. Andosols are characterised by the presence of either an andic horizon or a vitric horizon. An andic horizon is richin allophanes (and similar minerals) or aluminium-humus complexes whereas a vitric horizon contains an abundance ofvolcanic glass.Andosols typically have a dark humic A horizon on top of a brown B- or C-horizon. Topsoil and subsoil colours aredistinctly different. The average organic matter content of the surface horizon is about 8% but some varieties may containas much as 30% organic matter. The surface horizon is very porous and the good aggregate stability of Andosols and theirhigh permeability to water make these soils both fertile and relatively resistant to water erosion.Other international names are Andisols (Soil Taxonomy), Vitrisols (France) and volcanic ash soil.16