Classification of Cryosols - Cryopedology - page 65

where the soil-temperature class (STC) is hypergelic (−10 °C or colder) and are
predominant in areas where the STC is gelic (−4 to −10 °C). However, in areas
with a subgelic STC (+1 to −4 °C), permafrost is below the 1 or 2 m required
depth for Gelisols, and the soils are classifi ed in Gel- suborders or great groups.
A frigid STC (1-8 °C) includes soils with seasonal frost; these soils lack perma-
frost are classifi ed in Cry- suborders and great groups.
There are 52 Gelisols soil series in the NRCS SSURGO database for the USA,
including all three suborders, 9 great groups, and 14 subgroups (Table 6.6 ). It is of
interest that only 14 (13 %) of the 107 possible subgroups allowed in the Gelisols
are represented by identifi ed soil series; and 38 (73 %) of the 52 soil series occur in
three subgroups: Typic Historthels, Typic Aquiturbels, and Typic Histoturbels.
However, the database contains additional Gelisols from Russia and Antarctica.
In 2006 a cryosol subgroup was recognized as one of 32 such subgroups in the
WRB (IUSS WRB Working Group 2006 ). cryosols were defi ned as mineral soils
with permafrost within 100 cm of the ground surface and were considered to be
analogous to Gelisols in ST, cryozems in the Russian scheme, and Polar Desert soils
in the zonal system of Tedrow ( 1977 ). Detailed information about cryosols in the
WRB is given in Tarnocai et al. ( 2004 ).

Table 6.6 Classifi cation of soils within the Gelisol order and current soil series recognized in the

USA
Suborder Great group Subgroup Soil series recognized

Histels Folistels Lithic

Glacic Fels

Typic Peluk

Glacistels Hemic

Sapric
Typic

Fibristels Lithic

Terric
Fluvaquentic
Sphagnic
Typic Lemata

Hemistels Lithic

Terric Wrangell

Fluvaquentic Haggard

Typic Bolio, Bonot

Sapristels Lithic

Terric
Fluvaquentic
Typic

(continued)