Coatings in cryoaridic soils and other records of landscape and climate changes in the Ak-Khol Lake basin (Tyva)

An assemblage of coatings in cryoaridic soils (Skeletic Cambisols Protocalcic) of southwestern Tyva is considered as a key block of soil memory, which is an intrasoil archive of landscape and climate changes in regional geosystems in the Holocene. The results of hierarchical macro-, meso-, and micromorphological studies of a large assemblage of coatings and the data on the X-ray microanalysis of coatings and composition of stable carbon and oxygen isotopes, as well as on radiocarbon dating of coatings are presented. The synthesis of the results made it possible to reconstruct the main evolutionary phases of cryoaridic soils in the Holocene and landscape and climate changes that induced their alteration. The following climatogenic evolutionary phases of pedogenesis were distinguished: (1) formation of microsparite–micritic dense silica-containing coatings due to short-term fluctuations of the shallow alkaline bicarbonate groundwater level in the semiarid–arid climate; (2) formation of sparitic dense coatings under the slow accumulation of carbonates from low-mineralized bicarbonate water at the higher lake level as compared to the present one in the less arid conditions; (3) the eluvial-illuvial formation of micritic loose coatings under stable automorphic semiarid conditions; (4) formation of Fe-humus coatings in cool humid climate (Al–Fe-humus phase of pedogenesis); (5) the recommencement of the eluvial-illuvial formation of micritic loose coatings under aridization of the last thousand years of the Holocene.     

Soils of cryogenic subarid steppe landscapes in the Terekhol intermontane Depression of the Sangilen Upland

The soil cover of the Terekhol intermontane Depression in the Tyva Region is poorly studied. The data obtained in the 1950s do not reflect the real genetic diversity of soils and their specific character. According to these data, the soil cover was dominated by meadow-chernozemic soils under virgin steppe-like meadows. The investigations of 2007–2009 show that the disperse-carbonate chernozems, which are often solonetzic and weakly saline; the specific polygenetic dark soda solonchaks-solonetzes; and the postagrogenic chernozems, solonetzes, and agrozems are the main components of the soil cover of the depression at the present time. The described chernozems correspond mainly to the central image of southern Siberia chernozems. The investigated solonetzes are characterized by a number of evolution-genetic features that distinguish them from previously described solonetzes of Tyva and from all the solonetzic soils in the current interpretation. The chernozems and solonetzes have cryogenic features due to the cold extremely continental climate and relatively shallow continuous permafrost.     

Record of Holocene Changes in High-Mountain Landscapes of Southeastern Altai in the Soil–Sedimentary Sequence of the Boguty River Valley

Eurasian Soil Science - The results of morphosubstantive genetic study of a soil–sedimentary sequence with four buried soils in the Boguty River basin (southeastern Altai) are discussed. A...     

Cryo-geomorphological evolution of soils on islands of Terekhol Lake,Tyva, Southern Siberia

Specific soils on calcareous lacustrine sediments have been described on the islands in the Terekhol Lake, Terekhol’skaya intermontane trough of the Tuva Upland. The islands themselves originate from frost heaving cycles as shown by their relief and interfacial analysis of litho- and biostratigraphy of dated cores sampled in the bottom of the lake and on the islands. Soils of two altitude-age groups (generations) of islands have been studied. Younger islands (400–1700 cal yrs BP) have relative heights above the lake level below 2.5 m and an active layer 0.6–1.5 m thick. Histic Cryosols (Limnic, Drainic) were found there. Soils are well drained now and have no relation with the lake waters. The central elevated parts of older, and higher islands (4000–5000 cal yrs BP; 2.5–4.5 m, active layer about 1.5 m thick) are under dry-steppe phytocenoses on Calci-Mollic (Histic) Cryosols (Limnic, Calcaric, Gypsiric). The following evolution phases of islands and their soils were reconstructed. The lacustrine sediments were raised from the sedimentation zone to remain in subaerial conditions, where Histic Cryosols were formed. Owing to heaving, an admixture of limnic material was included in them. Further heaving resulted in the isolation of soils from the lake waters, the sedimentation completely stopped, and pedogenesis slowly shifted toward that inherent to well-drained conditions under dry-steppe vegetation. Histic horizons got degraded and transformed to mollic ones, the permafrost table moved deeper, carbonates, gypsum and soluble salts were leached from the upper horizons.