gleysols

Gleysols are soils formed in environments that remain saturated with groundwater or surface water for long periods, leading to reduced conditions in the upper part of the soil profile. The defining feature is gleying: pale gray to bluish-gray matrix colors produced by reduction of iron, often accompanied by distinct redoximorphic mottling produced when the soil dries and oxidizes. The diagnostic horizon or subhorizon shows low chroma colors (typically chroma 2 or less) and conspicuous mottles of brown, olive, or yellow caused by alternating reducing and oxidizing conditions.

Formation and properties: In saturated soils, oxygen is depleted, iron and manganese are reduced and mobilized; when the water table drops, oxidation occurs and iron oxides re-precipitate, forming mottles. The result is a characteristic gley texture and color. Gleysols are usually mineral soils with horizons displaying gley features; some may accumulate organic matter in the top layers in shallow water.

Distribution and environment: They occur in poorly drained landscapes such as floodplains, depressions, coastal wetlands, peatlands at the edge of water bodies, and in regions with frequent waterlogging. They are common in temperate and boreal zones but occur worldwide where drainage is slow.

Management and significance: Gleysols indicate wetland conditions important for hydrology, biodiversity, and carbon storage. They are often drained to improve agricultural use, which can alter redox conditions and soil structure and may release greenhouse gases. Preservation of the natural hydrological regime is important for maintaining ecosystem functions associated with these soils.