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37
АРИДНЫЕ ЭКОСИСТЕМЫ, 2005, том 11, №26-27
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АРИДНОЕ ПОЧВООБРАЗОВАНИЕ И ПРОБЛЕМЫ ЕГО ИЗУЧЕНИЯ В РЕГИОНАХ ЕВРОПЕЙСКОГО ЮГА РОССИИ
© 2005 г. З.Г. Залибеков
Прикаспийский институт биологических ресурсов Дагестанского научного центра РАН 367025, г. Махачкала, ул. Гаджиева 45, Россия
Изучение процессов аридного почвообразования проводится в Прикаспийском институте биологических ресурсов ДНЦ РАН в пределах регионов Европейского юга России. Исследовательская работа сосредоточена на территории равнинного Дагестана, поскольку самая южная и типичная пустынно-степная климатическая обстановка, как основной фактор почвообразования, проявляется на территории Дагестана. При определении процессного уровня дифференциация стадий опустынивания мы руководствуемся принципами признания определенного типа отношений между взаимосвязанными компонентами наземных экосистем при которых изменение одного компонента приводит к смене другого, как правило способствуя развитию процессов деградации. Из комплекса факторов - почвообразователей наибольшее влияние на почвы оказывают климатические условия и растительность. Не отрицая значимости зоологических, гидрологических, биохимических критериев мы считаем, что приоритетом в определении стадий процессного уровня должны стать почвенные и климатические характеристики. Руководствуясь этими предпосылками на данном этапе исследований целесообразно принять за основу динамику почвообразования и их зависимость от параметров почвенного климата. Установленные параметры почвенного климата изменяются в зависимости от способов воздействия на растительный покров, определяемый плотностью выпасаемого поголовья скота. Процессы перегрева поверхности почвы под влиянием солнечной радиации проникая внутрь почвенной массы оказывают существенное влияние на преобразование органической и минеральной части почв. Можно полагать, что установленный для сероземов Центральной Азии процесс преобразования илистых частиц в профиле является характерной чертой опустынивания. Познание этих закономерностей даст возможность для оптимизации температурного режима почв, способствующего повышению продуктивности природных кормовых угодий и улучшению продовольственной базы населения.
ARID SOIL FORMATION AND THE PROBLEMS OF ITS STUDYING IN THE SOUTH
REGIONS OF RUSSIA
© 2005. Z.G. Zalibekov
Caspian Institute of biological resources, Daghestan scientific center, Russian Academy of sciences.
367025, Makhachkala, M. Gadjiev 45, Russia
Study of arid soil formation is undertaken in Caspian Institute of biological resources DSC RAS, including South regions of Russia. The major part of our research on this problem is concentrated on the territory of Caspian plain in Daghestan republic, where the most typical desert-steppe climatic situation is represented.
In identifying processing level of desertification stages differentiation we follow principles of definite type or ratio between correlated components of terrestrial ecosystems, in which the change of one of the components leads to change of the another one, and that causes development of land degradation.
Climatic conditions and vegetation have the strongest influence on development of soil processes among all the complex of its factors. It is possible to say, that majority of common rules, typical for biological objects, influence on soil as on an open bio-stagnant system, as well.
With a high importance of botanic, zoological, hydrological criteria, we consider that the priority in identifying of processing level stages belongs to soil criteria with climatic characteristics. In this connection, on the going stage of the research worth wile to consider the dynamics of soil formation processes and their dependence on parameters of soil climate as a basis. Soil climate parameters, in studied region depend on ways of influence on vegetation cover, determined by density of sheep livestock per unit area. The processes of land surface overheating under the impact of sun radiation permeating inside of soil mass have a strong influence on reformation of organic and mineral parts of soil. We think, that determined for gray semi - desert soil of Central Asia process of reformation of mud particles in the profile is typical stage of desertification.
In condition of soil profile dehydration of loam and clay compositions and weathering of soil mass, organic substances and emitted by them decomposition of carbon dioxide takes part in soil formation. Subsoil dehydration (temperature rise) includes not only degradation processes. In some extend, it contributes to formation of new mineral structures and minerals, unstudied yet.
Peculiarity of soil formation processes in arid conditions is expressed by successiveness of stages with its morphological and physical-chemical properties. Stages of soil properties change are followed by deterioration of agronomic characteristics, decrease of productivity and lose of stability. Such evolution we call regressive evolution, as formation of new properties is followed by staged simplification of structural-functional organization of soil. For illustrating these indexes we use stages of regressive evolution of meadow-chestnut and light-chestnut soil of the Tersko-Kumskaya lowland. In meadow - chestnut soil desertification is connected with salinization, that's why this type of desertification was called halogen-lithogeneous type of desertification.
On background level, the profile is distinctly differentiated on horizons with generally accepted parameters of morphological features. During the first stage of desertification the humid horizon is being lost, as well as structural-functional organization of the profile and subhumid horizon is going on the land surface. In condition of moderate stage of development of regressive evolution humid horizon is blown off, soil forming sediments draw near the surface and, in fact, humid part of the profile is disappearing what entails decrease of biophilic elements' role in turnover and the features of geological turnover are manifested. In strong and very strong stages of regressive evolution, humid cover disappears completely, exposed to destruction and denudation. Analyzing the stage of regressive evolution of light chestnut soil, the same trend is revealed with formation of aeolian - lithogeneous type of desertification. Its stages are differentiated by the degree of expressiveness of the processes of windy erosion and sedimentation. Characteristics of the stages of regressive evolution of light-chestnut soil show diminution of the degree of humidity from 2,5% of the gross contents to 0,5%. The most typical is density of hard phase of the first stage 1,1 - 1,3, in the stage of very strong desertification>1,7, what explained by a high anthropogenic impact, pasture load, influencing by physical density on sediments coming on the land surface. We have to mention reduction of water permeability (mm/h) according to the parameters of desertification degree. The same changes are manifested by the accumulation of vaporous moisture of atmosphere and projective cover of vegetation by the stages of desertification and decrease of plant productivity.
Data, characterizing change of soil climate according to quantity of pasture loads are of considerable interest. Increase of density of 5 pastured sheep heads per hectare (fig.1) entails temperature rise of light-chestnut, middle-loam soil in 0-3 layer to 5-6 0C in comparison with condition of maximal loads of 1 sheep per hectare. Dynamics of temperature regime change of some layers differs in interval 10-14 0C. Formed differences result in decrease of moisture stock and nutritious elements, accessible for vegetation . As well as indicators of salinization, erosion and slitization, temperature regime of upper soil horizons serves as limitive factor. Reveal of optimal gradation of soil profile temperature, particularly during dry periods represents one of the most important problems of arid soil formation. It is illustrated by daily variation of temperature (fig. 2) on light-chestnut soil surface. Maximal temperature with maximal difference under 6-8 0C is formed between variants with optimal load of 1 sheep per hectare and deteriorated parcel with over load >5 sheep per hectare. On the basis of changes, revealed by temperature indicators it is possible to say about formation of essential changes in soil climate under anthropogenic factor. Influence of climatic conditions, contributing to arid
degradation is illustrated by vertical zones of development of wind's different speeds on different altitudes. Dust, risen in atmosphere forms 2 tiers: in zone of low speeds it entails sedimentation process, but in zone of high speeds - material transportation in long distances on intercontinental level (fig. 3). We can consider that sands' move from Aral basin reaches coastal parts of the Caspian Sea, forming massifs of moving sands.
Studying of physical properties by desertification stages of light-chestnut soils shows changes of such important indicators as density and water permeability in upper layers. On the background level of desertification processes fold density is characterized by optimal unit 1,0-1,2 with high water permeability 50-60 mm/hour. Gradual increase of desertification processes is revealed according to their stages, mentioned earlier. In stage of very strong desertification density of layer fold is 0-10 cm> 2,0. Essential differences are formed by remote soil indicators. According to intensity of pasturage, particularly, in soil areas with different summarized salt contents in half meter layer of the profile in % (limits of approximate distance). In intensive pasturage salt contents in half meter layer of light-chestnut soils forms 0-0,2%, minimal area 2,2 % , maximal-2,8%. By increase of summarized salt contents in meadow solonchaks to 2 %, minimal area forms 62,3, maximal 62,3 the total area of "mobile" soil areals in intensive pasturage is 1,5%, in moderate pasturage 2 sheep per hectare 4,6, in reserved regime 48,1. According to these data we can conclude that cattle breeding is one of the most important factors of soil formation. In intensive pasturage, "mobile" areals are stabilized on the level of strong desertification, in reserved regime with duration of 10 years, maximal unit of "mobile" areals on the level of low, desertification is formed. The same data are revealed in change of soil areas with different degree of salinization. In intensive pasturage more than 3-5 sheep per hectare of "mobile" areals during 2000-2002 years is about 46,6 %, indicating dynamics character of remote soil indicators. Maximal unit of "mobile" areals differs between moderate level and strong level of soil salinization, that reaches 46,652,9%. Soil formation, as phenomenon totality of moving processes is characterized by formation of "mobile", moving areals differentiated by salinization degree, sodicity, erosion, slitization. Formed indicators of soil categories by desertification stages illustrate ratio and unit of soil functioning areas to the total land territory. Borders of soil functioning areas are differentiated in general structure with soil areals under strong desertification impact, where geological sediments came on the surface by wind erosion and contemporary sediments-in condition of salinization and sodicity high development. According to these data very high content of functional soil area is revealed in meadow solonchaks and fixed sands that are in stage of restoration. In stage of transformation to typical solonchaks, light-chestnut solonchaks, meadow solonchaks and meadow-chestnut soils, decrease of FCP to 85-90% is revealed and accordingly increase of areas under desertification impact on high and very high level. Very low content of <70% is typical for light-chestnut, sor, crust soils and solonchaks where desertification is very strong - there are lands without biogeocoenosis cover.
Generalized data about anthropogenic desertification drivers manifest the leading role of processes connected with interaction of open land surface with atmosphere, vegetation cover and formation of geological sediments on the surface.
Atmosphere processes' influence is manifested by the rise of fine earth soil material by wind in atmosphere and its concentration in wet layers, preventing from precipitation. In the same time, temperature gradient is formed and the currents of moisture don't move. Very important factor is data of vegetation cover, increase of areas without vegetation cover and open land surface. These processes contribute to spread of the area occupied by inhabited localities and increase of reflecting ability of soil.
Generalizing results of arid soil formation study, we should note that soil which is influenced by desertification processes, in consequence of radical changes transform in particular taxonomic unit with high diversity of properties, typical for terrestrial ecosystem conditions. That's why we consider that formation of new variety of soil types and new gradient of environmental conditions with different set of properties is elementary act of arid soil land evolution.
Its principle feature - cyclic change of arid ecosystems, of water and geological origins.
Carrying out of fundamental and applied researches of soil formation processes and laws of their changes in conditions of dry regions by the type of soil and non soil formations - presents the basis of worked out scientific direction - "Arid soil formation".
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Fig. 1. Maximal temperature of upper layers of light-chestnut middle loam soils of the Tersko-Kymskaya lawland. A - optimal load 1 sheep/ha E - overpusturage in density 1 sheep/ha
- soil surface;
- depth 0-1 cm;
- -//- 1-3 cm;
- -//- 3-5 cm.
л
50л --^^
41} ■
■ 30- У / / / . / / N \ \ \ \ \
20/, X \ \ hours
S 10 12 14 16 18 20 22'Ss>v 14*07.94.
Fig. 2. Daily variation of temperature of the surface of light-chestnut middle-loam soil of the Tersko-Kumskaya lowland:
--optimal load (1 sheep/ha) on soil of ephemera-sagebrush (wormwood) vegetation;
-------- deteriorated parcel with over load > 5 sheep/ha.
