The method of cohesion determination in soil aggregates

Theoretical fundamentals and experimental methods to study the strength of water-stable bonds in soil aggregates are discussed. The strength of water-stable aggregates characterized by cohesion is proved to be one of the important structural and mechanical properties of soil. The regular variation of this parameter inthe soils under study is related to the content of humus and physical clay.     

Effect of mycorhiza-forming fungus <Emphasis Type="Italic">Glomus intraradices</Emphasis> on phytoextraction of nickel and copper and status of microbe cenoses under conditions of a model experiment

Effect of inoculation of plants by mycorhiza-forming fungus Glomus intraradices on nickel and copper phytoextraction from soddy-podzolic soil has been studied. The soil was intentionally contaminated by these elements. Mycorhization may cause both a rise and a drop in the content of the elements in the above ground parts of plants. It is shown that inoculation of plants by mycorhiza-forming fungus by its application to the soil at seeding does not result in the destabilization of microbe cenoses in the variants with application of heavy metals and in control variants.     

Structure and stability of soil aggregates

The formation and disintegration of macroaggregates into water-stable particles in a wide range of soil water contents—from the hygroscopic moisture to the capillary saturation moisture—were analyzed. It was found that the disintegration of macroaggregates into water-stable particles follows an exponential law. As the system becomes a three-phase system, neighboring particles in the macroaggregate are pressed together due to capillary pressure, and strong molecular bonds are formed. The disintegration curve of macroaggregates is an integral informative characteristic, which reflects the dynamics of changes in the strength properties of the macroaggregates.     

Structure and properties of soil organic-mineral gel

Changes in the fractal dimension and scattering intensity of colloidal structures in a chernozem, soddy-podzolic soil, and a krasnozem were studied by small-angle neutron scattering at different temperatures and soil water contents. The character of the neutron scattering by soil colloids indicated that the latter were mass fractals in all of the soils studied; i.e., the colloidal particles were located apart from one another even in dry soils. The obtained results confirmed the supposition about the distribution of colloidal particles in the humus gel matrix. The changes in the fractal parameters of the soddy-podzolic soil and chernozem with increasing water contents were nonmonotonic in character, which indicated complex structural rearrangements of the colloidal component in these soils. From the results obtained, a conclusion was drawn that the destruction of the molecular network of reinforced humus gel occurred upon heating the soils to high temperatures: colloidal particles reinforcing the humus gel began to move and coagulate with the formation of dense aggregates. The electron-microscopic study of gel films released from the predried and then capillary wetted aggregates in water showed that the gel films were nonhomogeneous and included zones of humus gel reinforced by colloidal particles and zones almost free from these particles.     

Actinomycetal complexes in drained peat soils of the taiga zone upon pyrogenic succession

The number and diversity of actinomycetes in peat soils vary in dependence on the stage of pyrogenic succession. In the cultivated peat soil, the number of actinomycetes after fires decreases by three-four times, mainly at the expense of acidophilic and neutrophilic groups. An increase in the number of mycelial prokaryotes (at the expense of alkaliphilic forms) is seen on the fifth year of functioning of the pyrogenic peat soil. The species diversity of streptomycetes in peat soils also decreases after fires. An increase in the range of streptomycetal species at the expense of neutrophilic and alkaliphilic forms takes place on the fifth year of the pyrogenic succession. Parameters of the actinomycetal complex—the population density, species composition, and ecological features—are the criteria whose changes allow us to judge the state of peat soils in the course of their pyrogenic succession.     

Biological Activity of Soils in Mountain Tundra Ecosystems under Postpyrogenic Restoration

The dynamics of the content and microbiological transformation of carbon and nitrogen compounds in the surface horizons of mountain tundra soils are considered in the postpyrogenic succession. The contents of total and labile carbon and nitrogen increase in the course of postpyrogenic soil evolution. At the same time, in the surface organic horizons, the carbon reserves, as compared to the nitrogen ones, are restored faster. The aerobic transformation of carbon compounds prevails at all the stages of the succession. The tolerance of soil organic matter toward mineralization increases as the ecosystem recovers after fire. However, this parameter reaches the values characteristic of the control soils no earlier than 60 years after the fire. The microbial communities of the podburs (Folic Podzols, Haplic Podzols) restore their functional activity fast enough after the fire (about three years). In the remote future, the effect of fire leads to an increase in the availability of soil nitrogen and in the soil ability to fix atmospheric nitrogen. Despite the temporary increase in the availability of mineral nitrogen (including nitrates) at early stages of the postpyrogenic restoration of soil systems, denitrification does not play a significant role in the biogeochemical cycle of nitrogen.     

Relationship between water tension and electrical resistivity in soils

An increase in the soil water content results in a decrease in the electrical resistivity of soil. This relationship obeys an exponential equation. When the water content is below the range of capillary-film water, the clearest relationship between the electrical resistivity and water content is observed, which allows the soil and ground waters to be studied. At a high water content, the dependence of the electrical resistivity on the content of exchangeable anions, the pH, and some other properties is detectable.     

Electrical resistivity as a possible indicator cultivation of arable sandy soils of the humid zone

It is established that soils with different degrees of cultivation have distinctions not only in the morphological structure of a profile, but also in the capacities of anthropogenically transformed (arable) horizons, properties of soils that are reflected in the amounts of electrical resistivity of the soils defined both on a profile and in a vulgar measurement with the use of horizontal electrical resistivity. Accurate reduction of the amounts of electrical resistivity of soils with term increase cultivation is revealed in the middle of a range (0?C100 years) reflected in fertility improvement. The express method of electrical resistivity mapping is rather promising for evaluating changes in properties of sandy soils in humid zone during anthropogenic agricultural transformation.     

Obtaining Spheroplasts of Armored Dinoflagellates and First Single-Channel Recordings of Their Ion Channels Using Patch-Clamping

Ion channels are tightly involved in various aspects of cell physiology, including cell signaling, proliferation, motility, endo- and exo-cytosis. They may be involved in toxin production and release by marine dinoflagellates, as well as harmful algal bloom proliferation. So far, the patch-clamp technique, which is the most powerful method to study the activity of ion channels, has not been applied to dinoflagellate cells, due to their complex cellulose-containing cell coverings. In this paper, we describe a new approach to overcome this problem, based on the preparation of spheroplasts from armored bloom-forming dinoflagellate Prorocentrum minimum. We treated the cells of P. minimum with a cellulose synthesis inhibitor, 2,6-dichlorobenzonitrile (DCB), and found out that it could also induce ecdysis and arrest cell shape maintenance in these microalgae. Treatment with 100–250 µM DCB led to an acceptable 10% yield of P. minimum spheroplasts and was independent of the incubation time in the range of 1–5 days. We show that such spheroplasts are suitable for patch-clamping in the cell-attached mode and can form 1–10 GOhm patch contact with a glass micropipette, allowing recording of ion channel activity. The first single-channel recordings of dinoflagellate ion channels are presented.