Page 87 - Microsoft Word - 20120528 Unesco study

Histosols
Origin:
Most of the Histosols are generated by chemical-biological phenomena under conditions of
hydromorphic, a permanent or temporary state of saturation of water in the soil that is
associated with the existence of reducing conditions. Histosols comprise soils characterized by
being highly organic, even peaty with frequent water logging and nature devoid of oxygen.

Environment:
Are limited to poorly drained basins, depressions, swamps and wetlands with shallow water
and highland areas with a high ratio of precipitation/evapotranspiration.

Comparison:
The mineral fraction of these soils is minor compared with that provided by the necromass.
PT - Peat and other highly organic soils.

Leptosols
Origin:
Because these soils are begun to be altered by the action of climate and vegetation, many of
its properties are associated with rocks that it originated them and therefore are very varied.
Consist of several types of continuous rock or unconsolidated material, less than 20 percent
(by volume) of fine soil.

Environment:
They are found mainly in lands with medium or high altitude with strongly dissected
topography. Leptosols are found in all climate zones, particularly in areas with heavily eroded.

Comparison:
Leptosols are extremely young and thin soils, very rocky with abundant gravels. Therefore,
they can be compared with the following groups:
GW - Gravel well graduates, sand and gravel mixtures with little or no fines
GP - Poorly graded gravels, sand and gravel mixtures with little or no fines
GM - Silty gravels, mixtures of gravel, sand and silt
GC - Clayey gravels, mixtures of gravel, sand and clay

Luvisols
Origin:
They come from a wide variety of unconsolidated materials including extremely
heterogeneous sediments of glacial origin and eolian deposits, alluvial and colluvial.
Differentiation of pedogenic clay content with a low content in surface soil and a higher
content in the subsoil without advanced weathering of high-activity clays.

Environment:
Mostly flat or gently sloping lands, mountainous terrain, undulating plateaus, cool and warm
temperate regions with pronounced dry and wet seasons.

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