Permafrost

The analysis of the data concerning the conditions of the occurrence and the chemical
composition of cryopegs, obtained during these investigations and taken from literature,
enabled us to identify landscape indicators of the cryopegs that are situated near the surface.
The origin of those cryopegs, which possess both a salinity that is considerably lower than
that of the sea water and a chemical composition that is devoid of sulphates but has increased
magnesium ion content, cannot be considered to be completely understood. Association on the
cryopegs with hasyreys and riverbeds suggests that their formation is connected with cryogenic
metamorphosis during deep freezing of the lake (surface) and under-lake (under-riverbed)
groundwater in very severe climatic conditions (about 20000-18000 years ago). In this case, the
depth of cryopegs of this type is determined by the depth of paleo-lake. A promising direction
for ongoing investigations of cryopegs is the greater application of isotopic method.
The presence of cryopegs in the ground poses several challenges to infrastructure: they
considerably reduce the bearing capacity of the ground and the brine solution aggressively
attacks concrete and is corrosive to metals, which also renders surface water unusable for water
supply. Temperature conditions of formation of cryopegs needs to be studied in future.
Influence of Morphological Structure of Soils on the Depth of Seasonal
Thawing
Alexey Desyatkin
(Hokkaido University, Sapporo )
Abstract: In order to assess the role of soil morphological structure on the thawing depth
during the the growing season in cryolithozone, measurements of soil temperatures were carried
out on four sites of the Central Yakutia. Observed sites are located close from each other and
developing in identical bioclimatic conditions. For comparison two meadow and two forest
sites were selected. Meadow sites located on the belts of optimum moisture at Tungulu (site 1)
and Ulakhan Sukkhan alases (site 2) and were developed under the presence of Рucсinе11iа
tеnuif1оrа (Grisеb.) Sсribn, еt Меrr. meadows. The maximum height of a grass cover reached
40-50 cm, productivity of meadows 15 c/ha in dry weight. Characteristics of forest sites are as
follows: site 3 – cow berried larch forest (Larix gmelinii (rupr). Rupr.) with low density
(0,4-0,5), middle productive capacity (about 90 m 3 /ha); 4 - Pinus sylvestris L. pine forest with
foxberry, has low density (0,4-0,5), and also has middle productivity (about 90 m 3 /ha). Thus,
characteristics of vegetation cover of sites are close, but each site differs by morphological
structure and granulometric structure of soils.
Capacity of the top humus-accumulative horizon in forest sites, and sod-humus layer in
grassland soils is the basic difference in a morphological structure of soils. Therefore, capacity
of sod humus horizon of grassland soil of site 1 amounts 10-15 cm, but at the site 2 - up to
40-45 cm, middle clay loam horizons located below. In forest soils of site 3 the structure of the
top part of soil profile is as follows: 6 (8) - 0 cm – over surface cover of cowberry, 0-2 (4) cm –
tree litter from weakly decomposed plant remains, from 2 to 5 (8) cm humus-accumulative
horizon. And lower located middle clay loam horizons. A morphological structure of the top
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