5.13 - Histosols

Histosols are soils without permafrost that are predominately composed of organic materials in various stages of decomposition. They generally consist of at least half organic materials (by volume). They are usually saturated with water which creates anaerobic conditions and causes organic matter accumulation at rates faster than that of decomposition. Little soil profile development is present, due to their saturated and anaerobic condition, however layering of organic materials is common.

Histosols can form in wetland areas of any climate where plants can grow such as bogs, marshes, and swamps, but are most commonly formed in cool climates

Soil order - Histosols. *Image courtesy of USDA-NRCS*

**Profile example - Histosol Series. Image courtesy of USDA-NRCS**

**USDA details**

**More information from the University of Idaho**

Key Characteristics: Histosols

Organic Peat Lands, or Boggy soils
Consist of layered organic materials (more than 20% organic materials by mass)
Form in cool, wetland environments
Do not contain permafrost.
Found mainly in geographically high latitude areas or other marshy wetlands.
Extent of world ice-free land area: 1%

U.S. Order Distribution Map for Histosols. *Image courtesy of USDA-NRCS*

**Further Details from the NRCS**

Quiz

Question

The most dominant soil forming factor at work in the formation of Histosols is usually:

A. parent material

Incorrect: Wetland environments -- where saturated, anaerobic conditions limit decomposition -- promote the accumulation of partially decayed plant materials of any type. Decomposition is further slowed by cool temperatures.

B. climate

Correct: Yes! Even though Histosols are composed of mainly organic materials (vegetation), they require a wet, saturated environment that limits decomposition. Cooler climates also limit decomposition, promoting accumulation of organic materials.

C. vegetation

D. topography

E. time

Looks Good! Correct: Yes! Even though Histosols are composed of mainly organic materials (vegetation), they require a wet, saturated environment that limits decomposition. Cooler climates also limit decomposition, promoting accumulation of organic materials.

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