Soils

These factors, including time, which influence soil development are commonly referred to as soil-forming processes. Their influence has often resulted in the formation of visible so-called soil horizons. The soil includes the humus layer and the mineral soil, but not the litter layer / S layer.

There are several structured systems for classifying different soils. The most commonly used classification systems today are Soil Taxonomy and the World Reference Base for Soil Resources (WRB). Within the National Forest Soil Inventory, soils on the inventoried sample plots were classified according to an older Swedish system, but since 2003 soils have been classified according to the international WRB classification system.

The frequency maps of different soils shown below are based on data collected during the years 1983–1987. At that time, the soils were classified according to the older Swedish system. However, by making use of a number of the inventoried variables, it was also possible to construct soil classes according to the WRB system. How this was done is shown under the heading “Determination of soil class according to the WRB system”. Prior to 1998, the WRB system was referred to as the FAO/Unesco system or the FAO system, which is reflected in some of the maps shown below.

Frequency maps of soils according to the WRB system

The maps were created based on data collected during the years 1983–1987. The soil classes according to the WRB system were constructed by making use of a number of variables that were determined at that time, in a manner that is described in more detail on the page Soil Classification.

More reading

Soil Horizons 

Soil‑forming processes

Soil Classification 

Diagnostic horizons, properties and materials

Short description of WRB soil groups common in Sweden