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Ergasheva Olimaxon Xaliqjonovna, National University of Uzbekistan E-mail: [email protected] Gafurova Lazizakhon Akramovna, National University of Uzbekistan E-mail: [email protected] Djalilova Gulnora Tulkunovna, National University of Uzbekistan E-mail: [email protected].
DISTINCTIVE FEATURES OF THE DISTRIBUTION OF MEDIUM HIGH MOUNTAIN SOILS AND THEIR DEGREE OF ERODIBILITY
Abstract: Distinctive features of the distribution of mountain cinnamonic soils and subtypes are described in the paper, the distinction in morphological indices, chemical, agrochemical and physical properties of these soils are given, as well as the content and character of humus distribution, СО2 carbonates in the composition of absorbed bases, depending on their location in various slope exposition and their susceptibility to erosion. It is established that all these indices are closely related to climate, slope exposition, the composition of soil-forming rocks and the state of plant cover.
Keywords: Mountain cinnamonic soils, subtypes of cinnamonic carbonate, cinnamonic typical, cinnamonic leached, soil erosion, degree of erodibility, morphological indices, thickness of the humus horizons, humus, chemical, physical properties, clay-forming, relief, steepness and exposition of slopes, soil protection.
Introduction: The problem of studying mountain nov, N. V. Kimberg, 1961; B. V. Gorbunov, N. V. Kim-
soils and their protection from erosion is becoming more berg, 1975; A. Z. Ghenusov, 1983; O. M. Mamytov, 1986;
and more urgent. This is due, firstly, to the recognition of M. A. Mazirov, 1995; A. S. Nazarov, 1996; M. F. Fakhrud-
the outstanding role of soil in the life of biosphere, and dinova, 1998; Kh. M. Makhsudov, L. A. Gafurova,
secondly, to the recognition of the fact that the top-soil is I. Turapov, A. Khanazarov, 2002; G. M. Nabieva, 2008;
now in unfavorable ecological state. Indeed, by now it has L. A. Gafurova, 2017; G. T. Djalilova, 2017 and others).
been convincingly shown that soil is not only the main However, there is still no consensus on the nature of
means of agricultural production, but also an important mountain soil formation; the distinctions in the genesis
component of earth biogeocenosis, a powerful energy of mountain soils have not been adequately established,
accumulator on the earth, a regulator of the composi- their classification and methodology for large-scale soil-
tion of atmosphere and hydrosphere, a reliable barrier to erosion mapping, which should account for the features
the migration of pollutants. However, it is necessary to of erodibility of mountain soils located in different exposi-
state that this earth component of biosphere undergoes tions and elements of the slope, have not been developed.
considerable degradation. Of all its aspects, the most With this in mind, we set the task of studying the
widespread and harmful is soil erosion. Therefore, it is ecological-genetic state of the main top-soil, the certain
no accident that the authorities in Uzbekistan pay serious features of medium high mountain soils and their de-
attention to the problems of soil protection from erosion. gree of erodibility in mountain areas, while simultane-
Current state ofthe issue: Mountain soils have been ously compiling a soil erosion map for the development
studied by many researchers (I. P. Gherasimov, 1948, and deployment of erosion control measures, including
M. A. Glazovskaya, 1956; A. Z. Ghenusov, B. V. Gorbu- biogeocenosis protection.
Materials and methods ofresearch: The subjects of research are mountain cinnamonic typical soils common in mountainous regions. The investigations were carried out by three methods: 1) route-expeditionary one with cutting of soil sections (slits) along the slope elements; 2) cameral- laboratory one; 3) stationary-field. Soil profiles were laid on the slopes of southern expositions, as the most prone to erosion, and also at northern expositions.
Results of research and their discussion: As a result of long-term field route-expeditionary and laboratory research in the area under study, the following subtypes of mountain cinnamonic soils have been identified:
Mountain cinnamonic calcareous (eroded) soils; the criterion for subtyping is the thickness of the carbonate-leached layer of the profile. This is reflected by the high layingof soil, i.e. a difference in general climatic character, and particular features - the effect of exposition and moisture content. The most pronounced clay-forming of the entire stratum, especially the middle part, is characteristic for cinnamonic soils. The feature of cinnamonic mountain soils is a carbonate content of the mineral part carbonates. The degree of carbonation and the depth of occurrence of carbonates depend on the stage of soil development. In carbonate calcareous soils, they occur from the surface, in typical and leached soils the occurrences are determined by the depth and intensity of soil saturation by atmospheric precipitation. A different ratio of soils and soil formations makes it possible to distinguish a combination with a predominance of fine-earth-skeletal differences, as well as outcrops and screes. Soil-forming rocks of cinnamonic calcareous soil-sare mainly loess-like loams and eluvium of limestones. On steep slopes of the juniper belt, these soils often develop on slates and limestones deluvium, less often on deluvial loess-like loamy soils. Cinnamoniccal careous soils located on southern slopes usually suffer heavily from grazing, they are heavily eroded, fine-grained, skeletal-fine-grained soils on proluvium and eluvium of bedrock. Geological process of formation of erosion relief has contributed to the rise of known differences in the properties of virgin cinnamonic calcareous soils along the elements of the slope. Sharp changes occur in the content of humus, nitrogen and other nutrients. The noted differences, although related to some surface distribution of substances and moisture content under the influence of geological erosion, are mostly the results of
unregulated grazing of livestock. Due to pasture erosion, the soil is washed away.
Mountain cinnamonic typical soils on the investigated objects are distributed above cinnamoniccal careous soils, at an altitude from 1200 to 1800 m above sea level. They are developed under large-grass-shrubby vegetation, shrub thickets, juniper forests. Cinnamonic typical soils has the humus horizon more powerful than cinna-monic calcareous soils, more pronounced illuvial layer and more deep-lying calcareous layer (100-200 cm). The process of clay-forming in cinnamonic typical soils is more developed than in cinnamonic calcareous soils.
The study of the main morphological properties of mountain-cinnamonic typical soils has shown the following features: deep humus profile, i.e. the presence of a rather thick dark-colored humus horizon A; humus content in this horizon varies considerably, and therefore one can distinguish a light (low-humus), dark (mediumhumus) and humus types of cinnamonic soils. In the color of the transition horizon (B1, and even more so B2), brown and dark brown tones are more pronounced. Downward along the profile, the color gradually becomes lighter from light brown to whitish, due to a decrease in humus content and the appearance of carbonates; deep processing of the whole humus horizon by earthworms and digging animals; compacted clay-forming horizon in the middle part of the profile and fracturing.
The presence of carbonate illuvial horizon at a certain depth: in carbonate cinnamonic soils - within the humus horizon A, in typical soils - in the lower part of the profile, at depth of 110-180 cm, a massive accumulation of carbonates, the boundary of carbonates being sharp. The mountain-cinnamonic leached soils are developed on the most humid areas of the range of mountain cinnamonic soils. They are distributed above cinnamonic typical soils or are combined with them. The composition of vegetation there are: meadow-steppe cenosis with iris, teresken, etc., as forthe shrubs - archa, spruce, apple, walnut.
Cinnamonic leached soils are distributed in the upper stripe of cinnamonic soil belt, below they turn into cinnamonic typical soils, which gradually give way to cinnamoniccal careous soils. Mountain cinnamonic leached soils differ in the thickness of the humus horizon, formation of various subtypes of cinnamonic soils.
Morphological description of the sections reveals the following features ofmountain cinnamonic leached soils: a
thick humus horizon, brown color, well-pronounced gran-ular-pulverescent and lumpy-granular structure, absence of a pronounced carbonate horizon. Leaching from carbonates is characteristic for the upper and middle parts of the profile. Individual carbonate discharges appear below.
Thus, the study ofmorphological indices ofcinnamon-icsoils has shown that the structure ofthe top -soil is closely related to the relief, slope exposition, composition of soil-forming rocks and the state of vegetation, this has caused the formation of various subtypes of cinnamonicsoils.
Chemical and agrochemical indicators of cinnamon-icsoils, distinctions in morphology and physical properties of these soils, in particular in the content and distribution of humus, carbonates, in the composition of absorbed bases and other components, are noted. The distribution and content of humus in the vertical profile of soils under consideration are specific. Cinnamonic typical soils are characterized by a moderate content of humus in the upper horizon and a sharp decrease in it below the sub-turf horizon. The humus content in the upper turf and sub-turf horizons varies from 5.8 to 7.3% or less, downward its amount decreases considerably. In the upper horizon of mountain cinnamonic calcareous soils, the humus content varies from 1.11 to 3.15% depending on the slope exposition and the degree of erodibility; downward decrease in humus content being gradual. In cinnamonic calcareous soils, an amount of humus is less than in cinnamonic typical soils, which is due to the sparse plant cover, on the one hand, and the rapid rate of mineralization of the organic mass under conditions ofeluvial-xeromorphic regime, on the other hand. Mountain cinnamonic soils are characterized by a wide carbon-nitrogen ratio: in the upper humus horizon it is from 7 to 11.8, in the subsequent ones - from 5.1 to 8.9. The enrichment of humus with nitrogen depends to a large extent on its qualitative composition. In the upper horizons (to a depth of 60-100 cm), the carbonate content does not exceed 1% of the soil mass. In the rock this index reaches 8-9%, and the boundary between the transition and carbonate horizons is sharply expressed. In the carbonate horizon, in addition to the pseudomycelium carbonates, the white-eye and concretions are observed.
Cinnamoniccal careous soils have a high content of carbonates throughout the profile. Ifin typical cinnamonic soils the carbonate content does not exceed 1% in the upper one meter layer, then in cinnamoniccal careous soils it
varies from 6 to 16% along the profile. Thus, the obtained materials on the content of humus and nutrients show that the formation of the humus horizon, its thickness and humus content is largely determined by the exposition of the slope, soil erodibility, and the supply of organic matter. With the increase in slope steepness, the humus content and thickness of the humus horizon decrease, especially in cinnamonic calcareous soils on the southern slopes.
The structure of the top-soil of the area under study is closely connected with the climate, slope exposition, slope element, the composition of soil-forming rocks and the state of vegetation; all that causes the formation of mountain cinnamonic calcareous soils, mountain -cinnamonic typical, as well as mountain - cinnamonic leached ones, which differ in morphological features, mechanical composition, chemistry and susceptibility to water erosion.
Conclusions: Erosion processes are intensively developing due to the complex geological and geomorpho-logic structure of soil surface with significant slopes and depth of local bases of erosion, weak erosion-preventive stability of soils and soil-forming rocks, non-uniform distribution of atmospheric precipitation, stormy rains in spring, large-scale plowing of land, lack of erosion-preventive measures.
The top-soil structure is closely related to the climate, slope exposition, the composition of soil-forming rocks and the state of vegetation. These factors cause the formation of cinnamonic soils of the vertical belt. The accumulation of salty fractions was found everywhere, especially in the middle part of the profile. Significant skeletal nature of soil was also noted, especially on the slopes of southern exposition.
It was revealed that the formation of the humus horizon, its thickness and humus content is largely determined by the exposition of slope, soil erodibility, chemical and physical properties, and reserve of plant mass. With an increase in slope steepness, the humus content and thickness of the humus horizon decrease.
Erosion processes have largely changed the morpho-genetic, chemical, agrochemical and agrophysical properties of soils. With increasing degree of erodibility, the content and reserves of humus, the reserves of nutrients, the amount of physical clay decreased; the structure deteriorated, and the number ofwaterproof aggregates and moisture content in soil decreased.
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