13
The average monthly rainfall is low from July to September, increases in autumn
(October and November), and is thus maximum in March or April, after which a
rapid drying occurs in May and June. Winds can be intense, which sometimes cause
dust storms, especially towards the end of the dry season in September and October.
Specific cities that exemplify climate patterns in Central Asia include Tashkent and
Samarkand, Uzbekistan; Ashgabat, Turkmenistan; and Dushanbe, Tajikistan, the
latter of which represents one of the wettest climates in Central Asia with an average
annual rainfall of over 254 mm (Alamanov et al. 2006).
2.2 Description of Central Asian Soils
The natural conditions in Central Asia are very diverse. Depending on the climate,
vegetation, and geological structure of the area, the soil cover also changes. The
most pronounced change in soil types occurs from north to south, which is called
latitudinal zoning. In the mountains, the soil types change from the foot to the top,
indicating that there is a vertical (high-altitude) zonation.
The weathering processes in the sharply continental conditions in Central Asia
led to the formation of a residual carbonate–silicate weathering crust, which is relatively weakly weathered, that is expressed in the abundant accumulation of sandy–
silty destruction products and low content of fine (silty) particles. The weathering
products are loess-like (this is one of the main reasons of the wide distribution of
loess and loess-like deposits in Central Asia); they are rich in various elements of
plant ash nutrition.
The weathering processes are most active in the middle-mountain and lowmountain high-altitude zones, where more clayey products are formed. In deserts,
however, weathering is mostly weakened and complicated by the accumulation of
carbonates, gypsum, and readily soluble salts. Similar processes occur in the desert
highlands.
The products of weathering of rocks are transported by surface and underground runoff. Due to the drainlessness of the territory of Central Asia, they accumulate in closed basins. The main role in this accumulation belongs to readily
soluble chloride-sulfate salts, gypsum and calcium carbonate. (Gvozdetsky and
Mikhailov 1978).
All the desert plains in Central Asia are areas of chloride–sulfate accumulation,
which occurs against a highly calcified background since solid runoff also plays a
significant role in the accumulation of lime (suspended sandy, dusty, and clayey
particles contain 7–23% of carbon dioxide). In addition, the low desert plains in
Central Asia, which have experienced several stages of the alluvial regime, are areas
where aluminosilicate weathering products accumulate in the form of sandy, sandy
loam, and clay particles brought by surface waters from the mountain ranges.
The composition of rocks and the processes of alluvial and proluvial sedimentation and subaerial denudation, as well as glaciation, gravitational processes, and
2.2 Description of Central Asian Soils
The average monthly rainfall is low from July to September, increases in autumn
(October and November), and is thus maximum in March or April, after which a
rapid drying occurs in May and June. Winds can be intense, which sometimes cause
dust storms, especially towards the end of the dry season in September and October.
Specific cities that exemplify climate patterns in Central Asia include Tashkent and
Samarkand, Uzbekistan; Ashgabat, Turkmenistan; and Dushanbe, Tajikistan, the
latter of which represents one of the wettest climates in Central Asia with an average
annual rainfall of over 254 mm (Alamanov et al. 2006).
2.2 Description of Central Asian Soils
The natural conditions in Central Asia are very diverse. Depending on the climate,
vegetation, and geological structure of the area, the soil cover also changes. The
most pronounced change in soil types occurs from north to south, which is called
latitudinal zoning. In the mountains, the soil types change from the foot to the top,
indicating that there is a vertical (high-altitude) zonation.
The weathering processes in the sharply continental conditions in Central Asia
led to the formation of a residual carbonate–silicate weathering crust, which is relatively weakly weathered, that is expressed in the abundant accumulation of sandy–
silty destruction products and low content of fine (silty) particles. The weathering
products are loess-like (this is one of the main reasons of the wide distribution of
loess and loess-like deposits in Central Asia); they are rich in various elements of
plant ash nutrition.
The weathering processes are most active in the middle-mountain and lowmountain high-altitude zones, where more clayey products are formed. In deserts,
however, weathering is mostly weakened and complicated by the accumulation of
carbonates, gypsum, and readily soluble salts. Similar processes occur in the desert
highlands.
The products of weathering of rocks are transported by surface and underground runoff. Due to the drainlessness of the territory of Central Asia, they accumulate in closed basins. The main role in this accumulation belongs to readily
soluble chloride-sulfate salts, gypsum and calcium carbonate. (Gvozdetsky and
Mikhailov 1978).
All the desert plains in Central Asia are areas of chloride–sulfate accumulation,
which occurs against a highly calcified background since solid runoff also plays a
significant role in the accumulation of lime (suspended sandy, dusty, and clayey
particles contain 7–23% of carbon dioxide). In addition, the low desert plains in
Central Asia, which have experienced several stages of the alluvial regime, are areas
where aluminosilicate weathering products accumulate in the form of sandy, sandy
loam, and clay particles brought by surface waters from the mountain ranges.
The composition of rocks and the processes of alluvial and proluvial sedimentation and subaerial denudation, as well as glaciation, gravitational processes, and
2.2 Description of Central Asian Soils