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Histosols are forming in organic soil materials. The general rule is that a soil is classified as a Histosol if half or more of the upper 80 cm is organic.
Fibrists are the wet, slightly decomposed Histosols. The largest extent is in southern Alaska. Most of the soils support natural vegetation of widely spaced, small trees, shrubs, forbs, and grasses and grass-like plants.
Folists are the more or less freely drained Histosols that consist primarily of horizons derived from leaf litter, twigs, and branches resting on bedrock or on fragmental materials. The largest extent is in Hawaii and Alaska. Some Folists developed in the mountains and the most humid parts of the conterminous United States. Most of these soils support forest vegetation. Some of the soils in Hawaii mainly support grass. A few of the soils in Hawaii are used for specialty crops or for urban or recreational development.
Hemists are the wet Histosols in which the organic materials are moderately decomposed. The largest extent is in Minnesota and Alaska. Most Hemists support natural vegetation and are used as woodland, rangeland, or wildlife habitat. Some have been cleared and drained and are used as cropland.
Saprists are the wet Histosols in which the organic materials are well decomposed. The largest extent is in Michigan, Florida, Wisconsin, Minnesota, and Alaska. Small areas are common on the Atlantic and gulf coasts. Many Saprists support natural vegetation and are used as woodland, rangeland, or wildlife habitat. Some of the soils, mostly those with a mesic or warmer temperature regime, have been cleared and drained and are used as cropland.