Soil types are considered 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 percent by mass of organic substances. These soils are sometimes overlaid with organic horizons of varying thickness; H, L, or O horizons with more than 30 percent by mass of organic substances, especially in forests.
Soil types of mineral soils are categorised into the following horizons:
- mineral topsoil horizon – A horizon,
- mineral subsoil horizon – B horizon, and
- mineral undersoil horizon – C horizon.
The mineral topsoil ‘A horizon’ is characterised by an accumulation of organic substances and/or a loss of mineral substance; washouts of clay, humic materials, iron oxides and aluminium oxides. Material-specific accumulation and translocation processes enable further divisions of the A horizon. This differentiation in horizon terminology is indicated by a trailing lower-case letter. Taking Ah as an example, h stands for humus, while l in Al represents clay lessivation (washout).
The mineral subsoil ‘B horizon’ is characterised by the accumulation of materials washed out of the topsoil horizon, as well as weathering and transformational processes, e.g. brunification and the formation of clay. This produces colours and material compositions different from that of the parent material. Further differentiation of the B horizon parallels the A horizon, e.g. the v in Bv stands for weathered, brunified, clayey; whereas the t in Bt indicates accumulated clay.
The mineral undersoil ‘C horizon’ is formed by the relatively unaltered parent material underneath the soil.
The soil profile of soils characterised by several translocational or transformational processes thus features several A and/ or B horizons layered on one another.
The horizon sequence indicates 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 influence of the groundwater level. The temporary or permanent effect of groundwater on soils affects how gley characteristics, e.g. rust and bleached spots, are formed in terrestrial and semiterrestrial soils. The depth of gley characteristics is applied in the naming of soil types, such as cambisols (brown soils):
- < 40 cm – dystric gleysol (brown gley soil)
- 40 to 80 cm – eutro-gleyic cambisol (gleyic brown soil)
- 80 to 130 cm – stagno-gleyed cambisol (gleyed brown soil)
Anthropogenic Alterations of the Soil
Anthropogenic alterations of the soil are increasing with progressing use of technologies and the use of ever larger areas.
Nowadays, there are hardly any untouched soils with horizon structures unaltered by humans. Soils are categorised as ‘near-natural’ where horizon sequences remain largely unchanged in spite of influences by human use, such as is commonly the case with forest plantations. Soils are categorised as anthrosols (anthric, anthropogenic soils, soils influenced by humans) when the horizon sequence has been destroyed. It has proven extremely challenging to clearly categorise soils into these two groups, due to the difficulty in identifying the exact transition point to anthropogenic influences. The upper 20 – 30 cm of soils used for agriculture are usually mixed by ploughing. In areas used as military training grounds or cemeteries, near-natural soils, interspersed with (small) patches of highly anthropogenic soil, may be preserved. The degree of anthropogenic influence and/or the degree of destruction is difficult to estimate without appropriate soil studies. The
effect use has on the soil is also influenced by whether the whole area was used or not.
A developmental point of view sees soils as relatively “young” or “old”. Soils relatively unaffected by use have a developmental period of up to several thousand years. The primary development of soils in the young moraine area around Berlin occurred in the Holocene period, which began about 12,000 years ago. A favourable climate, and the quick spread of vegetation connected with it, caused a stronger formation of soils. Various soil-forming processes took place during the long developmental period, and these processes are reflected in the formation of typical horizons. The horizon sequences of these soil types are thus much more greatly differentiated than those of “younger” soils.
Soil does not reproduce and is not reproducible. The use of soil is often linked with alterations of the original ecological conditions and this can lead to serious endangerment to the functional abilities of soil or even to its existence.
The quantity of soil as a natural resource is endangered by the progressive impervious coverage of soils. Industrial, commercial, traffic, and residential uses of soil are increasing more and more. Pervious soils once used agriculturally are found at the edge of the city; these soils have largely near-natural properties. Building construction caused soils to be translocated, mixed, made impervious over extensive areas and destroyed.
The quality of soils is altered by pollutants. Soils are permanently damaged by pollutant inputs from unregulated waste disposal, accidents, spills and leakages, improper storage as well as emissions from industry, commerce, and traffic. Pollutant inputs can directly and indirectly endanger all organisms, including humans. The primary concern is the uptake of pollutants through the food chain, but attention must also be given to the direct oral ingestion of soil, especially by small children.
Soil has a limited capacity to store and filter pollutants. If this capacity is exceeded, pollutants may pass through the soil unhindered and enter the groundwater.
In metropolitan areas like Berlin, issues related to land use, e.g. the quantitative problem of impervious coverage, and the qualitative problem of material contamination of the soil from old contaminated sites and other pollutant inputs, are particularly pronounced. Since soil is not renewable and heavily impacted soils can hardly ever be restored to their original quality, protecting remaining near-natural soils is imperative.
Soil Protection
The discussion and considerations on soil protection at federal and state government levels in West Germany first really got underway at the beginning of the 1980s. Soil protection was first anchored in law in the Federal Soil Protection Act of 1998. This law was supplemented by a Berlin law in 2004.
The goal of the Berlin Soil Protection Act is “to protect the soil as the basis of life for humans, animals, and plants; to avert damaging alterations and to take precautions against the origin of new ones”. Long-term effects to soil are to be avoided, and the natural functions of soil are to be protected.
Prerequisites for effective soil protection include knowledge about the spatial condition of the soils as well as impairments in their quantity and quality. In some cases, information on land use, degree of impervious coverage and material contamination of the soil has been compiled in Berlin for decades.
This information forms the basis for assessing the anthropogenic impact on the soil. A cadastre of impacts on soil was developed, and a Map of Degrees of Impervious Coverage as well as a Land-Use Map were prepared.
To plan soil protection measures and to consider soil protection concerns at individual planning levels, it is necessary to determine soil value, suitability, and sensitivity. Complete data about distribution of soils and their ecological characteristics must be available. The Map of Soils may be used to derive ecological parameters in order to assess soil properties and functions.
