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Berlin Environmental Atlas

01.01 Soil Associations (Edition 2013)

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Overview

Definition of Soil

Soil is the layer of earth formed on the surface by weathering and the influence of all other environmental factors. The mineral and organic substances of soil are pervaded with air, water and life forms. Natural soil originates through the combined interaction of parent material (basis rock), climate, water, relief, topography, flora, and fauna. The conditions at each location produce different soil types with characteristic profiles and specific physical and chemical properties.

Along with air, water, and sunlight, soil is the basis of life for plants and animals, including humans. Soil is not only a manufacturing base for foodstuffs, feeds, renewable raw materials and source of raw material itself, but has regarding its multiple functions an outstanding importance in the ecosystem and is an important natural resource.

Soil is:

  • natural habitat for animals and plants,
  • part of the ecosystem and its material cycles,
  • production basis for foodstuffs, feeds, and plants useful as raw materials,
  • filter and storage depot for groundwater,
  • location and supporter of constructed facilities,
  • an influential element of nature and the landscape and
  • an archive of natural and cultural history.

However soil is rearranged, altered and destroyed by human activities (e.g. in agriculture or by construction of buildings).

Thus, soil represents a limited and non-renewable resource, that must be dealt responsibly with.

Soil Formation

Soil formation is a natural process beginning on the surface of the earth and continuing into the depths. Table 1 names factors and processes which lead to differentiations of soil structures and properties, and to the formation of various soil horizons (layers). Soil types are formed by combinations of soil horizons.

Overview of Soil-forming Factors and Soil Development Processes
Tab. 1: Overview of Soil-forming Factors and Soil Development Processes
(after Lieberoth 1982)

Excel
[Table is also available as Excel-File (MS-Excel is required).]

Soil is formed from source rock; it is a mixture of 3 components and 3 phases of solid, fluid, and gaseous constituents:

solids: minerals, including rock fragments of various sizes, oxides, salts, colloids, and organic materials,
fluids: soil solution with dissolved nutrients and other elements,
gaseous: soil air (oxygen, nitrogen, carbon dioxide).

Systematization of Soils

Soils are systematized in divisions, major soil groups, soil types, soil units, and soil forms. (Translator's note: Soil systems in various countries and languages are complicated and are not uniform. This translation is oriented to the FAO/UNESCO system, as much as is possible. The terms in parenthesis following the FAO/UNESCO are common terms. The common terms are given so that readers who are not soil specialists may have some access.) The following divisions are differentiated according to groundwater level:

  • terrestrial soils,
  • semiterrestrial soils (semi-hydromorphic soils),
  • hydromorphic soils (groundwater soils),
  • sub-enhydrous soils (submerged soils),
  • bogs/swamps.

Table 2 exemplifies the principle of systematization with the division of terrestrial soils, major soil group of cambisols and andosols (brown soils). A detailed description of soil systemization in German is found in the Bodenkundliche Kartieranleitung (1982, 1994 and 2005).

Soil Classification
Tab: 2: Soil Classification according to Bodenkundliche Kartieranleitung 1982
(Soil Science Mapping Guidelines)

Excel
[Table is also available as Excel-File (MS-Excel is required).]

Soil Types – Horizons

Soil types are seen as stages of soil development often encountered under certain environmental conditions. They unify soils with the same or similar profile structures (horizon layers), due to similar processes of material transformations and translocations.

The most frequent soil types in Berlin are mineral soils with less than 30 mass percent of organic substances. These soils are sometimes overlaid with organic horizons of varying thickness; H, L, or O horizons with more than 30 mass percent of organic substances, especially in forests.

Soil types of mineral soils are categorized into the following horizons:

mineral topsoil horizon – A horizon
mineral subsoil horizon – B horizon
mineral undersoil horizon – C horizon

The mineral topsoil A horizon is characterized by the accumulation of organic substances and/or a loss of mineral substance; washouts of clay, humic materials, iron oxides and aluminum oxides. Material-specific accumulation and translocation processes enable further divisions of the A horizon. This differentiation in horizon terminology is given with a lower case letter; e.g., Ah, h stands for humus; Al, l stands for clay lessivation (washout).

The mineral B subsoil horizon is characterized by the accumulation of materials washed out of the topsoil horizon, as well as weathering and transformational processes, e.g., brunification, formation of clay, etc. This produces colors and material compositions different than the parent rock. Further differentiation of the B horizon parallels the A horizon, e.g. Bv, v stands for brunification; Bt, t stands for clay illuviation ("wash in").

The mineral C undersoil horizon is formed by the relatively unaltered parent rock underneath the soil.

Soils characterized by several material translocational or transformational processes have several A and/or B horizons in their soil profile.

The horizon sequence gives the horizon profile. The horizon profile is then used to differentiate soils into soil types.

Another factor in the formation of soil types is the groundwater level. The temporary or permanent action of groundwater on soils affects how terrestrial soils form gley characteristics, e.g. rust and bleached spots. The depth of gley characteristics is applied in the naming of soil types, such as cambisols (brown soils):

< 40 cm – eutric gleysol (brown gley soil)
40 - 80 cm – eutro-gleyic cambisol (gleyic brown soil)
80 - 130 cm – stagno-gleyed cambisol (gleyed brown soil).

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