Glossary

 

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Biota

A soil formation factor that describes living organisms in a particular region and at a particular time. It includes vegetation, microbes, soil animals, and human beings.


Black Earth

Term synonymous with Chernozem used (e.g. in Australia) to describe self-mulching black clays.


Bog

Wetland that has no significant inflows or outflows, supports acidophilic mosses, particularly Sphagnum and in which peat is accumulating. Similar to: fen, marsh, pocosin, swamp, and wetland.


Boulder clay

Unstratified glacial deposits laid down directly beneath the ice or dropped from the surface as the ice melted; boulder clay and till are synonymous terms for this unsorted material which ranges from rock flour to rocks and boulders of great size, according to the nature of the bedrock.


Calcification

Process whereby the soil is kept sufficiently supplied with calcium to saturate the soil cation exchange sites.


Capillary water

Water in capillary pores influenced by forces that hold water in soils against a tension usually greater than 60cm. Capillary water can move upwards against gravity.


Carbon cycle

Sequence of transformations whereby carbon dioxide is converted to organic forms by photosynthesis or chemosynthesis, recycled through the biosphere (with partial incorporation into sediments), and ultimately returned to its original state through respiration or combustion.


Cation

Particle with positive charge; reactions between anions and cations create electrical forces.


Cation exchange

Interchange between a cation in solution and another cation in the boundary layer between the solution and surface of negatively charged material such as clay or organic matter.


Clay

Soil particle smaller than 0.002mm or 2µm, with high specific area mainly influencing soil colloidal properties (see also colloid) as well as stability of soil structure: high stability in both wet and dry conditions; also a soil texture class.



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