Volume 50, Nº 3 (2017)

Taxonomic distances between pairs of soil orders in the Russian soil classification system have been calculated using a methodology suggested for calculation of taxonomic distances between the Reference Soil Groups in the international soil classification system (WRB). Basing on the data obtained, some proposals for the development of the Russian soil classification system have been formulated. Most of the orders are characterized by considerable taxonomic distances between them, and their identification in the classification system is doubtless. Small taxonomic distances are characteristic of the following pairs of orders: organo-accumulative and structural-metamorphic soils, hydrometamorphic soils and lithozems, and cryometamorphic and eluvial soils. Therefore, criteria for defining some orders, and/or profile formulas for some soil types composing the orders may be revised. The comparison of taxonomic distances between soil orders in the Russian system and between Reference Soil Groups in the international system allows us to suggest their certain similarity.

Contents of 11 most prevalent polycyclic aromatic hydrocarbons (PAHs) in snow and soils of arable, fallow, and forest areas significantly remote from impact technogenic sources of polyarenes have been examined in the Torzhok district of Tver oblast. From the analysis of snow samples, the volumes and composition of PAHs coming from the atmosphere onto the areas of different land use have been determined. Light hydrocarbons prevail in PAHs. They make up 65–70% of total PAHs; their share in soils reaches almost 95%. An increase in the content of PAHs is revealed in fallow soils compared to arable and afforested areas. A direct relationship is revealed between the lateral distribution of total PAHs and the content of organic carbon. The distribution of total PAHs is surface-accumulative in forest soils, mainly uniform in arable soils, and deepaccumulative in fallow soils. PAH groups characterized by similar radial distributions and ratios between their reserves in snow and soils are distinguished: (1) fluorene and phenanthrene, (2) biphenyl and naphthalene, (3) benzo(a)anthracene, chrysene, perylene, and benzo[a]pyrene, and (4) anthracene and benzo[ghi]pyrene.

Five variants of the distribution of clay (<0.001 mm) and physical clay (<0.01 mm) fractions along the vertical profiles of Vertisols (slitozems) and vertic soils (slitic subtypes of different soil types) from the European part of Russia are distinguished: (1) accumulative, (2) even, (3) regressive, (4) with a maximum in the middle-profile horizon and with their approximately equal contents in the upper and the lower horizons, and (5) eluvial–illuvial. These distribution patterns are related to the lithological specificity of sedimentation and formation of parent materials composed of swelling clays of different geneses and ages. Solonetzic, eluvial- gley, and solodic processes contribute to the development of the eluvial–illuvial and, partly, regressive variants of clay distribution. All the five variants with a predominance of the even distribution pattern can be found in Vertisols. Most of Vertisols in the European part of Russia have a medium clayey or a heavy clayey texture in the entire profile. The regressive distribution pattern is typical of the group of vertic soils. In the upper horizons of Vertisols, where slickensides do not form, the texture is usually heavier than that in the analogous horizons of vertic soils. The middle-profile and lower horizons with slickensides have similar statistical distributions of particle-size fractions in Vertisols proper and in vertic soils. However, in Vertisols, a tendency for a more frequent occurrence of the soils with a higher content of the clay fraction and with a higher portion of this fraction in the physical clay fraction is observed (as compared with the vertic soils).

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.

Soil biodiversity includes organisms which spend a part or all of their life cycle on or in the soil. Among soil-dwelling animals, macro-fauna as an important group of animals have important effects on the dynamics of soil organic matter and litter decomposition process. The humus forms interact with the climatic conditions, flora, as well as soil fauna, and microbial activity. In new humus form classifications, soil organisms play an important role in separation of humus horizons from one another. The subject of this study was to determine the diversity of macro fauna for different humus forms. We determined humus forms using morphological classification, and then 69 random samples were taken from plots of 100 cm² in area, and soil macro-fauna species were collected by hand sorting method. Two classes of humus forms, including Mull (with three humus orders, namely Dysmull, Oligomull, and Mesomull,) and Amphi (with four humus orders, namely Leptoamphi, Eumacroamphi, Eumesoamphi, and Pachyamphi) were identified. A number of 13 macro-fauna orders were identified using identification key. Among the humus orders, Shannon diversity, Simpson evenness and Margalef richness indices were the highest in Pachyamphi order. Arthropod diversity in Pachyamphi humus order was higher than those of Mull. These results showed that diversity of soil macrofauna increase by increasing the thickness of the organic horizons (OL, OF, OH), especially OH horizon.

The ecological status of oil-contaminated soils of Sakhalin and their background analogues has been evaluated with the use of soil invertebrates. The survival rates of Enchytraeus albidus in soils with different textures and the contents of organic carbon and nutrients have been compared. The indicative role of soil mesofauna (Enchytraeus albidus) for the ecological evaluation of oil-contaminated soils with due account for their properties has been shown. The permissible residual concentration of oil hydrocarbons in some soils of Sakhalin—acid brown forest soils (Umbrisols), high-moor peat soils (Histosols), acid meadow alluvial soils (Fluvisols), cultivated meadow soddy soils (Anthrosols), and mucky-podzolic surface-gleyed soils (Gleysols)— has been determined from data on the response of Enchytraeus albidus to different levels of the soil contamination with oil hydrocarbons.