Soils with gley horizons

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). 

Mottled red/brown and grey horizon diagnostic of gleysols 

As water moves through the soil, either by fluctuating groundwater levels or capillary action, this mobile aqueous iron species is dispersed. If the water table drops, however, the reduced Fe(HC03)2 is exposed to more oxygenated condition, resulting in the formation of oxidized (Fe3+) minerals such as Fe(OH)3 (Fig. 4.25). 

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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... 

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

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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