Том 50, № 4 (2017)

Soils and sediments composing Tell Körtik Tepe (Epipaleolithic, Turkey) and Tell Yunatsite (Chalcolithic (Eneolithic), Bulgaria) have been studied with the aim to gain a better insight into their microfabrics, determine the composition of anthropogenic artifacts, and, on this basis, to analyze similarities and distinctions between these objects and the modern soils of urban areas. The methods of micromorphology, scanning electron microscopy with an energy dispersive X-ray microanalyzer, X-ray fluorometry, and other techniques to determine the chemical and physical properties of the soils and sediments have been applied. Two paleosols have been identified in Tell Yunatsite with a total thickness of 9 m: the paleosol buried under the tell and the paleosol in its middle part. Sediments of Tell Körtik Tepe have a total thickness of up to 5 m; their accumulation began at the end of Pleistocene over the surface of buried paleosol. The cultural layer of the tells consists of construction debris mainly represented by a mixture of clay and sand and of domestic wastes with the high content of phosphorus. The major source of phosphorus is calcium phosphate (apatite) of bone tissues. The abundance of various anthropogenic materials in the sediments is clearly seen in thin sections. Even in the paleosols developed within the cultural layer (the mid-profile paleosol in Tell Yunatsite), the amount of microinclusions of bone fragments, charcoal, and burnt clay (ceramics) is very high. Micromorphological data indicate that up to 50% of the layered material filling an Epipaleolithic construction in Tell Körtik Tepe consists of the anthropogenic inclusions: bone fragments, charcoal, etc. The features of pedogenic transformation are present in the sediments. Such sediments can be classified as synlithogenic soils similar to the modern Urbic Technosols. It is shown that the formation of paleosols and sediments of Tell Körtik Tepe took place under extreme environmental conditions—arid climate of the latest Pleistocene climate cooling phase (the Younger Dryas, Tell Körtik Tepe)—and intensive anthropogenic loads (tells Körtik Tepe and Yunatsite).

The stocks of organic carbon and mean rates of the CO₂ emission during the growing season (May–September) and the entire year were estimated in a sequence of grass ecosystems along the transect encompassing chestnut and meadow-chestnut steppe soils, marsh and meadow alluvial soils, and a haloxerophytic community on a typical solonchak. The total stocks of organic carbon comprised 6.17–9.70 kg С/m² in steppe, 7.41–10.04 kg С/m² in floodplain, and 4.74 kg С/m² in haloxerophytic ecosystems. The portion of humus carbon in the upper 50-cm-thick soil layer comprised 79–92% of the total carbon stock. The mean daily CO₂ emission (С–CO₂/(m² day)) from alluvial soils was moderate (3.3–4.9) or low (1.5–2.5). The dependence of the CO₂ emission on the moistening of steppe soils, temperature of alluvial soils, and temperature and moistening of solonchak was revealed. In comparison with the CO₂ emission from the zonal chestnut soil, its mean values during the growing season and the entire year were 1.2 times higher for the meadowchestnut soil, 3.3 times higher for the marsh alluvial soil, 2.3 times higher for the meadow alluvial soil, and 1.7 times higher for the solonchak. The portion of the CO₂ emission beyond the growing season in the mean annual emission averaged 19.8–24.2% and depended on the type of grass ecosystem and on weather conditions of particular years. The sink of carbon in the grass ecosystems exceeded carbon emission, especially in the steppe ecosystems.

The mineralization and humification of leaf litter collected in a mixed forest of the Prioksko-Terrasny Reserve depending on temperature (2, 12, and 22°C) and moisture (15, 30, 70, 100, and 150% of water holding capacity ( WHC)) has been studied in long-term incubation experiments. Mineralization is the most sensitive to temperature changes at the early stage of decomposition; the Q₁₀ value at the beginning of the experiment (1.5–2.7) is higher than at the later decomposition stages (0.3–1.3). Carbon losses usually exceed nitrogen losses during decomposition. Intensive nitrogen losses are observed only at the high temperature and moisture of litter (22°C and 100% WHC). Humification determined from the accumulation of humic substances in the end of incubation decreases from 34 to 9% with increasing moisture and temperature. The degree of humification C_HA/C_FA is maximum (1.14) at 12°C and 15% WHC; therefore, these temperature and moisture conditions are considered optimal for humification. Humification calculated from the limit value of litter mineralization is almost independent of temperature, but it significantly decreases from 70 to 3% with increasing moisture. A possible reason for the difference between the humification values measured by two methods is the conservation of a significant part of hemicelluloses, cellulose, and lignin during the transformation of litter and the formation of a complex of humic substances with plant residues, where HSs fulfill a protectoral role and decrease the decomposition rate of plant biopolymers.

The results of experimental study of daily dynamics of denitrification activity and the activity and population density of ammonifiers in the abandoned (converted to long-term fallow) and intensely cultivated gray forest soils (Luvic Retic Greyzemic Phaeozems (Aric)) are discussed. The potential denitrification activity in the arable soil is higher than that in the fallow soil, whereas the actual denitrification activity in the arable soil is lower. Data on the dynamics of ammonification do not show reliable differences between the activities of ammonifiers in the arable and fallow soils, though the number of ammonifying bacteria is considerably higher in the arable soil. Differences in daily dynamics of the numbers of ammonifiers in the fallow and arable soils are shown.

An improved Mualem–Van Genuchten method for estimating soil hydraulic conductivity in the vadose zone from data on filtration coefficient and water-retention capacity of soil is proposed. The approach offered by Kosugi for a functional description of hydraulic conductivity of soil is applied. To calculate the values of hydraulic conductivity by Mualem’s formula, the function of differential water capacity of soil with interpreted parameters has been used instead of the function of integral water capacity of soil, which describes the water-retention capacity of soil. Approximations to functions of soil water-retention capacity and hydraulic conductivity are offered here. On the basis of some concepts on the specificity of the curve that describes soil water-retention capacity, a technique for identification of these parameters is developed. The experimental data from two parts of capillary pressure range, on which the water-retention capacity of soil is measured, are used in the technique. The first part corresponds to the zone of mainly film moisture, where the sorption component of the capillary-sorption forces retaining the water in the soil predominates. The second part includes (a) the zone of the mainly capillary-suspended moisture, where the capillary component of the capillary-sorption forces predominates, and (b) the zone of the capillary-backed moisture. The improved method for estimating relative values of hydraulic conductivity of soil has been verified with the use of measured data for the Beit Netofa Сlay soil. The advantages of this method include (a) the ability to identify parameters of the soil hydrophysical functions using relatively available soil indices and (b) the higher accuracy of calculating the soil hydraulic conductivity in comparison with the original version of the method.

Properties and mineralogy of fine fractions separated from agrochernozems forming a three-component noncontrasting soil combination in the Kamennaya Steppe have been characterized. The soil cover consists of zooturbated (Haplic Chernozems (Clayic, Aric, Pachic, Calcaric)), migrational-mycelial (Haplic Chernozems (Clayic, Aric, Pachic)), and clay-illuvial (Luvic Chernozems (Clayic, Aric, Pachic)) agrochernozems. All the soils are deeply quasi-gleyed because of periodical groundwater rise. The mineralogy of the fraction <1μm includes irregular mica–smectite interstratifications, di- and trioctahedral hydromicas, imperfect kaolinite, and magnesium–iron chlorite. The profile distribution of these minerals slightly varies depending on the subtype of spot-forming soils. A uniform distribution of clay minerals is observed in zooturbated agrochernozem; a poorly manifested eluvial–illuvial distribution of the smectite phase is observed in the clay-illuvial agrochernozem. The fractions of fine (1–5 μm) and medium (5–10 μm) silt consist of quartz, micas, potassium feldspars, plagioclases, kaolinite, and chlorite. There is no dominant mineral, because the share of each mineral is lower than 35–45%. The silt fractions differ in the quartz-to-mica ratio. The medium silt fraction contains more quartz, and the fine silt fraction contains more micas.

The analysis of bacterial complexes, including the number, taxonomic composition, physiological state, and proportion of ecological trophic groups was performed in a high moorland related to different elements of the microrelief. The abundance of bacteria, their ability for hydrolysis of polymers and the share of r-strategists were found to be higher in the sphagnum hillocks than on the flat surfaces. The total prokaryote biomass was 4 times greater in the sphagnum samples from microhighs (hillocks). On these elements of the microrelief, the density of actinomycetal mycelium was higher. Bacteria of the hydrolytic complex (Cytophaga and Chitinophaga genera) were found only in microhigh samples.

Urban recreation areas of different sizes were investigated in the city of Vladimir. The degree of their contamination with heavy metals and oil products was revealed. The content of heavy metals exceeded their maximum permissible concentrations by more than 2.5 times. The total content of heavy metals decreased in the sequence: Zn > Pb > Co > Mn > Cr > Ni. The mass fraction of oil products in the studied soils varied within the range of 0.016–0.28 mg/g. The reaction of soils in public gardens and a boulevard was neutral or close to neutral; in some soil samples, it was weakly alkaline. The top layer of all the soils significantly differed from the lower one by the higher alkalinity promoting the deposition of heavy metals there. As the content of Ni, Co, and Mn increased and exceeded the background concentrations, but did not reach the three-fold value of the maximum permissible concentrations, the activity of catalase was intensified. The stimulating effect of nickel on the catalase activity was mostly pronounced at the neutral soil reaction. The urease activity increased when heavy metals and oil products were present together in the concentrations above the background ones, but not higher than the three-fold maximal permissible concentrations for heavy metals and 0.3 mg/g for the content of oil products. The nitrifying activity was inhibited by oil hydrocarbons that were recorded in the soils in different amounts.