Cryogenic Soil Processes - Cryopedology - page 51

of permafrost regions and result in soils that have markedly different properties than
those not infl uenced by cryopedogenic processes (Makeev and Kerzhentsev 1974 ;
Hendershot 1985 ; Dobrovol'skiy 1996 ). For example, podzolic soils underlain by
permafrost are “genetically … the product of the podzolic process in combination
with the cryogenic process” (Kuzmin and Sazonov 1965 , p. 1272). Permafrost has
actually induced podzolization in the Transbaikal region through its control on
hydrologic and thermal regimes. In other environments, like those of central and
southwestern Yakutia, permafrost, along with low precipitation, suppresses pod-
zolization by limiting leaching of weathering products (Zolnikov et al. 1962 ).
Many aspects of the cryopedogenic process are “positive” in the traditional
sense, including size reduction of particles, arrangement of soil particles, formation
of soil aggregates, disintegration of rocks, and ice-salt exclusion (Tedrow 1968 ;
Makeev 1981 ; Marion 1995 ). Gerasimov ( 1975 ) identifi ed deformation, which
included cryogenic processes, as key elementary soil processes. Cryopedogenic
processes can be observed at the landscape scale by the presence of patterned
ground and at the pedon scale by cryoturbation (transfer), cryodesiccation (trans-
fer), and ice segregation (transfer/transformation). At the microscopic level, these
processes are manifested by characteristic platy, blocky, or vesicular macrostruc-
tures and banded and orbiculic microstructures (Gerasimova et al. 1992 ; Fox 1994 ;
Rusanova 1996 , 1998 ).

5.2 Cryopedologic Processes

Cryogenic soil processes may be viewed from a landscape scale, a pedon scale, and
a microscopic scale. At the landscape scale, cryopedogenesis is evidenced by a
variety of patterned ground features (Figs. 4.5 and 4.6 ) . Figure 5.1 depicts the evolu-
tion of cryogenic processes during soil development in a permafrost region, i.e., at
the pedon scale. Cold temperatures are the forcing factor. In the early stages of soil
development, yield an immature soil derived from relatively unaltered parent mate-
rials underlain by permafrost. As the soil undergoes development, the presence of
permafrost and the resulting active layer enable processes such as frost heaving,
cryoturbation, thermal cracking, and ice segregation to occur. These processes yield
irregular and broken soil horizon boundaries, the development of platy and massive
structures. The soil horizons that form refl ect not only these cryopedologic pro-
cesses but also the imprint of other pedologic processes such as humifi cation (devel-
opment of organic layers and organic-enriched A horizons), cambisolization
(development of color or structural B horizons), gleization (restriction of water fl ow
by the underlying permafrost), podzolization, etc.
At the microscopic scale, thin sections can show compaction from cryodesicca-
tion, displacement from cryoturbation and related processes, and pore-formation
from ice segregation (Fig. 5.2 ). These features are described using terminology
from the sub-discipline of soil micromorphology (Bullock et al. 1985 ).