Ecological and micromorphological research of soils of the central floodplain of the Samara river

Abstract

The influence of environmental factors on the formation of microforms typical for soils of the central river floodplain Samara and mechanisms of formation of the soil profile have been considered. The attention is paid to the identification and soil genesis of cutana. To achieve the goals the micromorphological research methods and techniques of scanning electron microscopy have been used. The decoding of soil thin sections has been carried out in the standard scheme. The relief of chip surface was studied in the secondary electrons, the homogeneity of the distribution of chemical elements - by the surface of the secondary electrons, the chemical composition of the studied surface areas was received by a microroentgen-spectral analysis. The studies have shown the main features in the microstructure of these soils. In the profile the microstructure is inhomogeneous, in the upper horizons is silty-plasma, changes with the depth to sand-plasma and in the lower horizons – plasma-sand. The skeleton grains are characterized by the following transfer on their surface (scratches) and by a good roundness. Plasma is humus-clay, with the depth the clayey plasma decreases. It is typical for the clay part of the plasma two refractive indices, the orientation and the ability to restructure. The pore space is the most developed in the upper horizons, thanks to digging activity of earthworms. With the depth the pore area decreases and often the pore walls cover with clayey cutanas for the illuvial processes. As a result of intensive impacts of nutrient factors, the upper horizons are well-structured. In each profile you can select several kaprolit horizons. For this kind of profile the humus mull is more typical. Kutana complex is represented by clay cutana. In the upper horizons they are poorly expressed, are not present in all pores. Down to the profile their quantity in the pores increases, they become more pronounced. The explanation of the chip surface using a scanning electron microscopy confirmes the mobility of plasma and illuvial origin of cutana. The data obtained in the secondary electron mode and microanalysis shows the monotony of addition with minor bright zones which belongs to titanium or chromium-containing minerals. The features of the microstructure of the soil profile in central floodplain are conditioned by the floodplain processes. With the reduction of their influence, because of the increase between the periods of flood and their intensity, the forming role of biological factors increases.