Page 32 - Soil Degradation, Conservation and Remediation

1.6 Classification of World Soils 17

2. If never saturated with water for more than a few days, 20 % or more organic
carbon
Histosols typically form in settings where poor drainage inhibits the decompo-
sition of plant and animal remains, allowing these organic materials to accumulate
over time. Thus, they have developed in organic parent materials, and they are
mostly soils that are commonly called bogs, moors, or peats and mucks. Peat is the
name given to slightly decomposed organic material in soil, while muck is used for
the rotten, highly decomposed material. The peat is used for fuel, potting soil in
greenhouses, and for packing. Histosols can be cultivated only if artifi cially
drained. Histosols serve as important habitats for wetland plants and animals and
as carbon reservoirs. Histosols are ecologically important because of the large
quantities of carbon they contain. Typically, Histosols have very low bulk density
(Chap. 5 ) and are poorly drained because of their occurrence in low-lying areas and
high organic matter content. Most Histosols are acidic, and many are defi cient in
plant nutrients. Many Histosols are not suitable for cultivation because of poor
drainage and low chemical fertility. However, many other Histosols formed on
recent glacial lands can be very productive when drained. They can sometimes be
used for orchards and vines if carefully managed. However, there is a great risk of
wind erosion, shrinkage, subsistence, and compaction. (The same Histosols name
is given in WRB.) Histosols occupy only 1.2 % of the global ice-free land
surface.
Histosols have four suborders mostly distinguished on the basis of the state of
organic matter and drainage. They are:
Fibrists: Fibrists are the wet, slightly decomposed Histosols. The largest extent is in

southern Alaska of the USA. Most of these soils support natural vegetation of
widely spaced, small trees, shrubs, and grasses.

Folists: 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. Most of these soils support forest vegetation. Some of the
soils mainly support grass. A few of the soils are used for specialty crops or for
urban or recreational development.
Hemists: Hemists are the wet Histosols in which the organic materials are mod-
erately decomposed. They are extensive 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: Saprists are the wet Histosols in which the organic materials are well
decomposed. The largest extent in the USA 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.