Gleysol

Gleysol is a reference soil assembly from the World Reference Base for Soil Resources (WRB). This group includes those soils that are strongly influenced by groundwater or by reducing gaseous substances and have developed corresponding redox or reduction characteristics.

Delimitation and definition

Gleysols are marked according to the WRB classification of mineral soils with signs of a shift of iron due to reduction and possibly diffusion and reoxidation . B. on typical colors or accumulations in the form of rust stains in their groundwater or reductant gas-influenced horizons.

Characteristic soil horizons

In the WRB soil classification, Gleysols are defined as soils with gleyic properties with at least temporarily reducing conditions (see below) that occur within the top 40 cm of the soil. Due to their position in the identification key, Gleysols must not have any of the following soil horizons :

• a salt ( salic ) or sulfur enriched ( thionic ) soil horizon above 50 cm
• a clay-rich soil horizon characterized by strong swelling and shrinking ( vertic )
• a clay-enriched, sodium-rich soil horizon ( natric )
• a permanently frozen soil horizon ( cryic )
• a soil horizon with high proportions of artificial material ( artefacts )
• one of the horizons that characterize Anthrosols ( hortic , plaggic , terric , pretic , irragric or anthraquic with hydragric ).

They also need the gleyic properties and reducing conditions

• begin at a depth of not more than 40 cm and be developed to a thickness of at least 25 cm or
• Use immediately below a dark, humus-rich mollic or umbric horizon, which has reducing conditions above 40 cm, developed over a thickness of at least 10 cm and extends deeper than 65 cm below the mineral soil surface

and the soil should be comparatively deep and not too rich in stones.

The gleyic properties

The gleyic properties are defined in the WRB as follows:

• at least 95% of the horizon with reductimorph colors (gray, yellowish-green, greenish, bluish or black) or
• 5% rust stains or iron concretions , especially along root tubes or in the outer area of ​​the soil aggregate .

The reducing conditions

The reducing conditions are defined in the WRB as follows:

• an rH value (negative logarithm of the hydrogen partial pressure ) (calculated as Eh · 29 ⁻¹ + 2 · pH) <20 or
• Presence of iron in the form of free Fe ²⁺ , detectable by red coloration when 0.2% α, α-dipyridyl solution in 10% acetic acid is added , or
• Presence of iron sulfide or
• Presence of methane .

The reducing conditions arise due to the displacement of the oxygen-carrying air by the groundwater or reducing substances in a gaseous state .

distribution

Gleysols are common all over the mainland, especially in lowlands. There they are associated with fluvisols , from which they can develop through pedogenic dissolution of the sediment layers. They also occur under low water cover, on tidal coasts also in the tidal area. They usually develop from loose rock .

Local names

Gleysols exist with a similar name in many soil classifications. In the German soil classification , they are the gleys , marshes , tidal flats or subhydrischen floors allocated in the Russian classification the Gleyzems . In Brazil they are currently referred to as track solos and in Australia as hydrosols . In the US Soil Taxonomy they do not form a separate order, but are marked with the prefix Aqu , for example Endoaquoll ( Mollisols ) or Endoaquept ( Inceptisols ), unless they are assigned to the Wassents ( Entisols ).

Web links

• Profile photos (with classification) WRB homepage
• IUSS profile photos (with classification) IUSS World of Soils

literature

• IUSS Working Group WRB: World Reference Base for Soil Resources 2014, Update 2015. World Soil Resources Reports 106, FAO, Rome 2015, ISBN 978-92-5-108369-7 ( PDF 2.3 MB).
• W. Zech, P. Schad, G. Hintermaier-Erhard: Soils of the world. 2nd edition Springer Spectrum, Heidelberg 2014, ISBN 978-3-642-36574-4 .
• W. Amelung, H.-P. Blume , H. Fleige, R. Horn, E. Kandeler , I. Kögel-Knabner , R. Kretschmar, K. Stahr , B.-M. Wilke: Scheffer / Schachtschabel textbook of soil science. 17th edition Springer, Heidelberg 2018, ISBN 978-3-662-55870-6 .