Page 31 - Soil Degradation, Conservation and Remediation

16 1 Soil Resources and Soil Degradation

1.6.5 Gelisols

Gelisols are soils that contain gelic materials (mineral or organic soil materials that show
cryoturbation, cryodesiccation, and/or ice segregation in the active layer). Gelisols are
soils of very cold climates that contain permafrost within 2 m of the surface. Freezing

and thawing in the active layer influence soil formation in Gelisols. Permafrost restricts
the downward movement of water. Thus, there are few diagnostic horizons in Gelisols,
if any. Cryoturbation results in irregular or broken horizons, organic matter accumula-
tion on the permafrost table, oriented rock fragments, and silt caps on rock fragments.
These soils are limited geographically to the high- latitude polar regions and localized
areas at high mountain elevations. Gelisols are the permafrost-affected soils that occur
throughout the zone of continuous permafrost in Antarctica (Bockheim 1995 ). (Gelisols

are called Cryosols in WRB classification system.) Gelisols occur in 8 % of the earth
surface. Gelisols have three suborders. They are:
Histels: Histels have organic horizons similar to Histosols except that they have perma-
frost within 2 m below the ground. They have 80 % or more organic materials from
the soil surface to a depth of 50 cm or to a glacic layer or densic, lithic, or paralithic
contact, whichever is shallower. These soils occur predominantly in subarctic and
low Arctic regions of continuous or widespread permafrost. The natural vegetation in
Histels is mostly mosses, sedges, and shrubs. The soils are used as wildlife habitat.
Turbels: Turbels are Gelisols that commonly show cryoturbation and contain

tongues of mineral and organic horizons, organic and mineral intrusions, and
oriented rock fragments. Organic matter is accumulated on top of the permafrost,
and ice wedges are common features in Turbels.

Orthels: Orthels are soils that show little or no cryoturbation (less than one-third of

the pedon). These soils occur primarily within the zone of discontinuous perma-
frost, in alpine areas where precipitation is greater than 1,400 mm per year. The
natural vegetation is mostly lichens, mosses, sedges, shrubs, black spruce, and
white spruce. The soils are used mostly as wildlife habitat. They occur through-
out the Gelisol area in Alaska. The vegetation is mostly mosses, sedges, shrubs,
and black spruce.

1.6.6 Histosols

Histosols are permafrost-free soils dominated by organic soil materials. Organic
soil materials consist of organic debris accumulating at the surface in which the
mineral component does not signifi cantly influence the properties of soils. Organic

soil materials have either:
1. Under water saturated conditions 18 % organic carbon (30 % organic matter) or

more if the mineral fraction has 60 % or more clay, or 12 % organic carbon (20 %
organic matter) if the mineral fraction has no clay, or a proportional intermediate
organic carbon for intermediate content of clay