Cast production and NIR spectral signatures of Aporrectodea caliginosa fed soil with different amounts of half-decomposed Populus nigra litter

Sub-adult individuals of Aporrectodea caliginosa were incubated for 16 weeks under laboratory cultures in a soil treated with 0%, 10% or 50% of a Populus nigra half-decomposed leaves, respectively. Growth was maximum in the 50% organic matter treatment and cocoon production occurred. Average soil ingestion rates decreased from 1.56 g/g^?1 fresh weight of worm per day^?1 in control soil to 1.17 and 0.5 g, respectively, in treatments with 10% and 50% half-decomposed litter. Surface casts never comprised more than 10% of total cast production. Near-infrared spectrometry (NIRS)signatures of digested and non-ingested soil significantly differed and showed a rather constant effect of digestion, independent of the organic matter content (p?<?0.01). These results confirm the value of NIRS spectral signatures as indicators of the origin of soil aggregates and biological processes involved in soil aggregation.     

Preferential water flows in an ordinary chernozem of the Azov Plain

Preferential flows of gravitational water were studied with the use of modified grid lysimeters in an ordinary chernozem developed from loesslike loam on the slightly inclined Azov Plain. Within horizontal soil sections, the lysimetric water flow changed from high values to the complete absence at short (5–10 cm) distances. The funnel type of gravitational water flow concentration was noted. According to the character of changes in water infiltration during two consecutive cycles of soil watering, the zones with stable and altering (both increasing and decreasing) water flows were distinguished. No definite regularities of the changes in the concentration of the added label (chloride salts) in dependence on the intensity of the water flows and on the depth of the lysimeter installation were noted. Five days after the infiltration of considerable amounts of water (250 and 135 mm) into the soil monolith, the spatial variability of the concentration of the label was seen at distances of 5–15 cm.     

Coefficients of association and activity of cadmium and lead ions in soil solutions

The thermodynamic calculations were made for the contents of Pb and Cd compounds in soil solutions and water extracts of the meadow-steppe and meadow solonetzes (Rostov oblast) based on their prescribed analytic concentrations of 3 and 5 μg/l, respectively. The solonetzes studied are characterized by their high carbonate content and high alkalinity. The activity of Pb²⁺ and Cd²⁺ was shown to be many times lower than their total concentration in the solution due to the association of these metals with carbonate and other anions and the formation of hydroxocomplexes CdOH⁺ and PbOH⁺. This fact is one of the reasons for the low input of Pb²⁺ and Cd²⁺ to plants growing on calcareous soils.     

Assessment of agronomic homogeneity and compatibility of soils in the Vladimir Opolie region

Complexes of gray forest soils of different podzolization degrees with the participation of gray forest podzolized soils with the second humus horizon play a noticeable role in the soil cover patterns of Vladimir Opolie. The agronomic homogeneity and agronomic compatibility of gray forest soils in automorphic positions (“plakor” sites) were assessed on the test field of the Vladimir Agricultural Research Institute. The term “soil homogeneity” implies in our study the closeness of crop yield estimates (scores) for the soil polygons; the term “soil compatibility” implies the possibility to apply the same technologies in the same dates for different soil polygons within a field. To assess the agronomic homogeneity and compatibility of soils, the statistical analysis of the yields of test crop (oats) was performed, and the spatial distribution of the particular parameters of soil hydrothermic regime was studied. The analysis of crop yields showed their high variability: the gray forest soils on microhighs showed the minimal potential fertility, and the maximal fertility was typical of the soils with the second humus horizon in microlows. Soils also differed significantly in their hydrothermic regime, as the gray forest soils with the second humus horizon were heated and cooled slower than the background gray forest soils; their temperature had a stronger lag effect and displayed a narrower amplitude in seasonal fluctuations; and these soils were wetter during the first weeks (40 days) of the growing season. Being colder and wetter, the soils with the second humus horizons reached their physical ripeness later than the gray forest soils. Thus, the soil cover of the test plot in the automorphic position is heterogeneous; from the agronomic standpoint, its components are incompatible.     

Changes in the structure of bacterial complexes of vegetable crops in the course of their growth on a cultivated soddy-podzolic soil

The dynamics of population density and taxonomic structure of epiphytic bacterial communities on the leaves and roots of potatoes, carrots, and beets have been studied. Significant changes take place in the ontogenesis of these vegetables with substitution of hydrolytic bacteria for eccrisotrophic bacteria feeding on products of plant exosmosis. The frequency of domination of representatives of different taxa of epiphytic bacteria on the studied plants has been determined for the entire period of their growth. Bacteria of different genera have been isolated from the aboveground and underground organs of vegetables; their functions are discussed. It is shown that the taxonomic structure of bacterial communities in the soil under studied plants is not subjected to considerable changes and is characterized by the domination of typical soil bacteria—Arthrobacter and bacilli—with the appearance of Rhodococcus as a codominant at the end of the season (before harvesting).     

Paleoecological crisis in the steppes of the Lower Volga region in the Middle of the Bronze Age (III–II centuries BC)

Diagnostic features of a catastrophic aridization of climate, desertification, and paleoecological crisis in steppes of the Lower Volga region have been identified on the basis of data on the morphological, chemical, and microbiological properties of paleosols under archeological monuments (burial mounds) of the Middle Bronze Age. These processes resulted in a certain convergence of the soil cover with transformation of zonal chestnut (Kastanozems) paleosols and paleosolonetzes (Solonetz Humic) into specific chestnut-like eroded saline calcareous paleosols analogous to the modern brown desert-steppe soils (Calcisols Haplic) that predominated in this region 4300–3800 years ago.¹ In the second millennium BC, humidization of the climate led to the divergence of the soil cover with secondary formation of the complexes of chestnut soils and solonetzes. This paleoecological crisis had a significant effect on the economy of the tribes in the Late Catacomb and Post-Catacomb time stipulating their higher mobility and transition to the nomadic cattle breeding.     

Heavy metals in soils and plants of the don river estuary and the Taganrog Bay coast

Natural and anthropogenic factors determining the distribution and accumulation features of Pb, Cu, Zn, Cr, Ni, Cd, Mn, and As in the soil–plant system of the Don River estuary and the northern and southern Russian coasts of Taganrog Bay estuary have been studied. High mobility of Cu, Zn, Pb, and Cd has been revealed in alluvial soils. This is confirmed by the significant bioavailability of Cu, Zn, and, to a lesser degree, Cd and the technophily of Pb, which are accumulated in tissues of macrophytic plants. Statistically significant positive correlations have been found between the mobile forms of Cu, Zn, Cd, and Mn in the soil and the accumulation of metals in plants. Impact zones with increased metal contents in aquatic ecosystems can be revealed by bioindication from the morphofunctional parameters of macrophytic plants (with Typha L. as an example).     

Effect of soil density,tensile strength,and water infiltration on the rupture rate of interaggregate bonds

The effect of density of monofraction samples from the plow horizon of leached chernozem on the rupture rate of interaggregate bonds in water has been studied. The rupture rate of bonds has been determined in a hydraulic flume by alternating passive phases of 1–5 min in duration, during which the sample occurs under a nonmoving water layer, with short (15-s long) active phases with a water flow in the flume. Samples have also been tested for tensile strength and water infiltration rate. It has been shown that the rupture rate of interaggregate bonds is related by a hyperbolic law to the soil density and by an exponential law to the rate of water infiltration to the soil. The latter relationship varies within a year and, hence, can be used as reliable parameter for predicting the seasonal dynamics of soil erodibility.     

Stability and morphological and molecular-genetic identification of algae in buried soils

Living cultural strains of the green algae ‘Chlorella’ mirabilis and Muriella terrestris have been isolated from buried soils, and their identification has been confirmed by morphological and molecular-genetic analysis. It has been shown that the retention of their viability could be related to their small size and the presence of sporopollenin in cell walls. The effect of methods for the reactivation of dormant microbial forms on the growth of algae in paleosols has been estimated. The total DNA content has been determined in buried and recent background soils, and relationship between DNA and the presence and age of burial has been established.