Alpine soils form on top of hard rocks and sediments. Therefore, they are clearly influenced by the physical and the chemical-mineralogical properties of the soil parent material (hard rocks and sediment), which is also important for the nutrient availability.

Chemical-mineralogical properties
For silicatic rocks, SiO₂ is the principal component. For carbonate rocks, it is CaO and CO₂. The other elements differ according to the rock type (Fig. 1). Consequently, soil chemistry is strongly related to bedrock, or, if the bedrock is overlain by sediments (e.g. slope debris, moraines, dust), to the sediments.

1 - Components of rock types

Physical properties
In alpine areas, bedrock is often covered by sediments like moraines, dust and solifluction deposits. The spatial distribution of the cover is often related to relief and landscape evolution. Generally, sediments are the precondition for the existence of well developed soils in alpine areas, whereas on hard rocks, mainly weakly developed soils form, because chemical weathering is minor.

Chilean Altiplano

The lower part of a steep slope in the central Chilean Andes (3500 m) is covered by slope debris. Bedrock as well as slope debris are overlain by dust, which is very typical for this arid to semiarid landscape. At the limit of bedrock, the soil type changes drastically, accompanied by a clear vegetation change.

Select two soil types and drag them to their appropriate area on the diagram. See Soil classification if more information is needed.

Austrian Alps

In this example from the Austrian Alps, bedrock is partly covered by a moraine (Upper Pleistocene). A late-glacial to Early Holocene solifluction lobe, which has been stabilized by alpine meadows, covers the landscape. Due to climatic deterioration during the Upper Holocene, a younger solifluction lobe has formed, which is still moving downstream and is covered with scarce vegetation. Soil types vary according to the availability and age of periglacial sediments.

Select the soil types and drag them to their appropriate position on the diagram. See Soil classification if more information is needed.

29 August 2011
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