Abstract form

Gypsum pedofeatures in arid soils and their transformation under the
impact of anthropogenic loads
Irina A. YAMNOVA* 1 , Dmitry L. GOLOVANOV 2
1 V.V. Dokuchaev Soil Science Institute, Russian Academy of Agricultural Sciences,
Pyzhevskiy per. 7/2, Moscow, 119017 Russia
2 Geographical Faculty, Moscow State University, Moscow, 199991 Russia
*Corresponding author’s e-mail: yamnova@agro.geonet.ru
The morphology of gypsum pedofeatures and their role in the microfabric of arid soils
were studied at the Dzhizak Experimental Station, Uzbekistan. Regularities in the
spatial distribution of different morphotypes of gypsiferous horizons were studied, and
the ways of their cartographic representation were developed.
The territory of the Dzhizak Experimental Station can be considered a model of the
Golodnaya Steppe piedmont plain to the north of the Turkestan Ridge; it is composed of
the sediments of merging alluvial fans. The territory occupies a local plateau with
nonsaline and nongypsiferous (in the upper meter) sierozems and the valley of a
temporary stream with hydromorphic strongly saline and gypsiferous meadow and
solonchakous soils. Our studies were performed before the construction of a drainage
channel and 20 years after it to trace changes in the character of gypsiferous soils
The following conclusions can be made.
(1) Three morphotypes of gypsum pedofeatures have been specified: (a) the
incrustational gypsum with the subtypes of fine-, medium-, and coarse crystalline
gypsum; (b) the nodular gypsum and (c) the powdery gypsum with the subtypes of
crumb-like and marly gypsum.
(2) These morphotypes of gypsum pedofeatures are developed in dependence of the
character of soil hydromorphism and the position of soil in the landscape. The
micromorphological description of gypsiferous horizons attests to the partial
substitution of calcite for gypsum crystals.
(3) Specially developed scales of the morphological parameters of gypsiferous horizons
were applied to develop the maps showing the distribution of different morphotypes, the
depth of the horizon with the maximum accumulation of gypsum and the gypsum
content in this horizon with indication of the relative contribution of each morphotype.
(4) The morphotypes of gypsiferous horizons can be mapped on a detailed scale.
According to the logic of the new substantive-genetic classification of Russian soils, the
content of gypsum in the soils can be reflected at different taxonomic levels (orders,
types, subtypes and varieties) in dependence on the intensity of gypsum accumulation
and its morphological manifestation.
(5) Studies performed after 20 years, when the groundwater level dropped by about 1 m,
showed that the gypsum content in the soils decreased insignificantly. The major
morphotypes were also preserved. However, micromorphological investigations
demonstrated certain changes in the microfabric of gypsum pedofeatures. Thus, fine
dispersed crystals of gypsum disappeared from the soil profiles, and the number of
pseudomorphic substitutions of calcite for gypsum crystals increased significantly
attesting to the progressive calcification of the soil profiles.
This study was supported by the Russian Foundation for Basic Research (project nos.
07-04-00136а, 08-04-90266-Uzb_а)
Key words: gypsiferous soils, morphotypes of gypsum, soil mapping, microfabrics of
gypsiferous horizons
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