Gley horizon

Gley horizons form when the water table is present within the soil profile. Soils with gley horizons (denoted g ) are typically aquepts (gleysols), a suborder of the inceptisols (Fig. 4.22). Gley horizons may be either Bg and/or Ag horizons, depending on the height of the water table influence in the soil profile (Fig. 4.25). 

The soil cover of the forest and thin-forest zone of Alaska consists of various sub-types of Gleysols, which are generally similar to analogous soils of North Siberia. Kaolinite and motmorillonite and also chloritized monmorillonite are present in the most intensely gleyed horizons. Lepidocrocite (monohydrate of iron oxide) and a large quantity of amorphous hydrated oxides of silicon and aluminum are found in almost all soils. The ratio of silicon to aluminum in the clay fraction is low, in certain places less than 1.0. 

Waterlogged mineral soils are those in which part or the whole soil profile is saturated for a sufficient period of time to create distinctive gley horizons in the profile. These soils can be sandy, loamy, or clay soils. The other most commonly referred term is flooded soils. We confine our discussion in this group primarily to mineral soils. The distinctive characteristics of these soils are... 

Mottled zone (gley horizon) where iron and manganese accumulate... 

The subscript g is used to indicate a gleyed horizon resulting from the reduction of Fe +. Use of g with B indicates pedogenic changes in the horizon, and use of g with C suggests no pedogenic changes in the horizon. 

Used with B or C horizon g Gleyed or waterlogged soil... 

Fig. 1. Hypothetical soil profile chat has all principal horizons. Not all horizons shown are present in any given profile, but every profile has some of them. Terms used in diagram Eluviation is the downward movement of soluble or suspended material in a soil from the A horizon to the B horizon by groundwater percolation. The term refers especially, but not exclusively, lo the movement of colloids, whereas the term leaching refers lo the complete removal of soluble materials. Illuviation is the accumulation of soluble or suspended material in a lower soil horizon that was transported from an upper horizon by the process of eluviation. Gleying is soil mottling, caused by partial oxidation and reduction of its constituent ferric iron compounds, due to conditions of intermittent water saturation. Process is also called gleizalion (Adapted from USD A diagram)...

Mineral horizons in which the main feature is loss of silicate clay, iron, aluminum, or some combination of these, leaving a concentration of sand and silt particles Horizons formed below A, E, or O horizons. Show one or more of the following (i) illuvial concentration of silicate clay (Bt), iron (Bs), humus (Bh), carbonates (Bk), gypsum (By), or silica (Bq) alone or in combination (ii) removal of carbonates (Bw) (iii) residual concentration of oxides (Bo) (iv) coatings of sesquioxides that make horizon higher in chroma or redder in hue (Bw) (v) brittleness (Bx) or (vi) gleying (Bg). 

The excessive ground humidity is favorable to tbe formation of gley soils in Boreal forest ecosystems. Clay-podzolic soils with a massive forest litter layer provide the conditions for low water saturation. In high water-saturated conditions, a peat horizon... 

In A horizons, some Fe and Mn can also be precipitated around plant roots. In many wetland plants, reddish-brown layers are seen around the roots, as a result of Fe oxidation and subsequent precipitation. This can also result in mottle formation along the channels of plant roots with surrounding gleyed soil. Root zone oxidation is most visible in completely reduced and gleyed soils, where they appear on red to yellow mottles. 

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