Authored by: Randall K. Kolka , Martin C. Rabenhorst , David Swanson

Handbook of Soil Sciences Properties and Processes

Print publication date:  November  2011
Online publication date:  November  2011

Print ISBN: 9781439803059
eBook ISBN: 9781439803066
Adobe ISBN:


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While most soils of the world comprise primarily mineral materials, a small but important group of soils are formed from organic materials derived from plants, or less frequently, from animals. Organic soil materials contain a minimum of 12%–18% organic carbon, depending on the particle size of the mineral component (Soil Survey Staff, 2010). Generally speaking, soils with at least 40 cm of the upper 80 cm that are organic materials, and which do not have permafrost within 1 m of the soil surface, are Histosols. Prior to 1997, organic soils with permafrost were included in the Histosol order; they are now placed in the Histel suborder of Gelisols (Soil Survey Staff, 1998). Following the separation of Histosols and permafrost soils, Histosols occupy about 1% of the global land area while the Histel suborder of Gelisols occupies about 0.8% (Buol et al., 2003). Organic soil materials are commonly referred to as peat, and land covered by Histosols or Histels is known as peatland. The term mire is a synonym of peatland that is more commonly used in Europe. Histosols also include a narrowly distributed group of soils, the Folists, that consist of well-drained organic soil materials that directly overly bedrock or coarse fragments with little or no intervening fine soil. The peat layer in Folists may be (and usually is) thinner than the 40 cm required for other Histosols.

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