Geoscience Reference
In-Depth Information
Table 6.4
The cryosolic order in the Canadian soil classifi cation system
Cryosolic order
Turbic cryosol
Static cryosol
Organic cryosol
Soil
Mineral
Mineral
Organic
Cryoturbation
Marked, usually patterned
ground
None
None
Permafrost
Within 2 m of surface
Within 1 m of surface
Within 1 m of surface
Soil Classifi cation Working Group (
1998
)
Table 6.5
Distribution of cold soil taxa by soil temperature class
Soil temperature
class
MAST, 50 cm
(°C)
Permafrost zonation
Dominant soil taxa
Hypergelic
−10 or colder
Continuous
Gelisols
Gelic
−4 to −10
Discontinuous
Gelisols
Subgelic
+1 to −4
Sporadic
Gelaquents, Gelifl uvents,
Golorthents,
Gelepts, Cryo(Geli-)
fi brists, Gellols,
Gelods, Gelands
Frigid
<8
Seasonal frost
Cryids, Cryalfs, Cryands,
Cryolls,
Cryods, Cryepts, Cryerts,
Cryaquents,
Cryofl uvents, Cryorthents,
Cryopsamments,
Cryofi brists, Cryofolists,
Cryohemists,
Cryosaprists
The fi rst technical soil classifi cation system in the USA went through a series of
six approximations before yielding the
Seventh Approximation
(Soil Survey Staff
1960
). This scheme recognized permafrost and classifi ed soils previously identifi ed
as Tundra soils and Subarctic Brown Forest soils as Entisols (Cryaquents and
Cryudents), Inceptisols (Cryaquepts, Cryandepts, Cryumbrepts, and Cryochrepts),
and Histosols (order in development stage). In 1975
Soil Taxonomy
(Soil Survey
Staff
1975
) recognized permafrost-affected soils in Pergelic subgroups of Entisols
(Cryorthents and Cryopsamments), Histosols (Cryofi brists, Cryohemists, and
Cryosaprists), Inceptisols (Cryaquepts, Cryochrepts, and Cryumbrepts), and
Spodosols (Cryaquods, Cryohumods, and Cryorthods).
The second edition of
Soil Taxonomy
(Soil Survey Staff
1999
) included
Gelisols, the permafrost-affected soils. These were divided into three suborders:
Histels, organic soils with permafrost within 1 m of the surface; Turbels, mineral
soils with cryoturbation and permafrost within 2 m of the surface; and Orthels,
mineral soils with no cryoturbation and permafrost within 1 m of the surface.
Great groups were based on diagnostic horizons. The distribution of cold soil taxa
