No 8 (2023)

On the example of the Rostov region, the results of measurements by the chamber method of methane fluxes into the atmosphere from rice fields are analyzed. In addition to measuring methane fluxes in the phases of “germination” and “full ripeness” of rice, concentrations of methane and hydrogen sulfide, Eh, pH, density and humidity were determined in the water of the rice check and various horizons of watered soils. The rate of methane flow into the atmosphere from the surface of the rice check varied in the range from 0.195 to 0.531 mg СН₄/(m² h) and in the “full ripeness” phase of rice was on average 2.1 times higher than in the “germination” phase. The rate of methane flow into the atmosphere from the surface of soils located between rice checks was on average 4.9–12.1 times lower than the rate of its flow from rice checks, varying within 0.034–0.045 mg СН₄/(m² h). It is shown that after watering rice checks in soils isolated by a layer of water, Eh values decrease and, as a consequence, there is an increase in methane concentrations in soils and its fluxes into the atmosphere. According to the assessment, the total methane emission by rice fields of the Rostov region approximately reaches 1.253 tons per day or 150 tons/year, which is 0.4–1.5% of the annual methane release by the soils of the Rostov region.

A comprehensive study of the net carbon balance of Lgov administrative district (Kursk oblast) in the Chernozem zone of the European part of Russia is carried out. The data sources included field estimates of carbon dioxide and methane exchange between soil and atmosphere, above- and below-ground phytomass stocks, simulation models parameterized on these data, official statistical and meteorological information, and published scientific data. Watered filtration fields of waste disposal sites of sugar industry are responsible for 26% of CH₄ emissions from the territory of the district, although they occupy only 0.04% of its area. The maximum of CO₂ emission is found at volumetric soil moisture of 30%, whereas, with exceeding this value, methane emission begins to rise linearly, reaching a maximum on the open surface of water reservoirs, and among them – on watered filtration fields. Another significant local source of methane is compost storages (22%). However, water reservoirs and ponds are the largest source of CH₄ (43%). Amongst the net sources of CO₂ the combustion of fossil fuels by transport and agriculture machinery predominates (22.3%). In contrast to methane, which emission is mainly determined by powerful point sources, the input of net fluxes of CO₂ positively correlates with their area. Currently observed low rate net CO₂ flux in the district area (–6.4 g C m^–2 per year), is decisively overlapped by local methane sources (+95 g C (CO₂-eq.) m^–2 per year). The influence of the types of land use and methods of calculation on the C-balance of the territory in study, and a way of its transformation into a carbon-neutral state are discussed.

The research is devoted to the analysis of biodiversity of Antarctic soil cyanobacteria in hypolithic organo-accumulative horizons of the Larsemann Hills (East Antarctica). Studying of fouling glasses by the methods of light and confocal microscopy, as well as fluorescent in situ hybridization, has shown that filamentous forms predominate among cyanobacteria in the upper layers of Antarctic hypolithic microbial communities. To clarify the taxonomic status, strains of the genera Nostoc, Halotia, Leptolyngbya, Plectolyngbya, Phormidesmis, as well as some new and previously undescribed representatives of Antarctic cyanobacteria were isolated from corresponding soil samples. The strains of the unique collection of soil cyanobacteria that we formed for the first time were described according to modern methods of polyphasic taxonomy based on analysis of the complex of morphological and molecular-genetic characters. The results of phylogenetic analysis of the primary sequence of 16S rRNA gene and peculiarities of organization of secondary structures of internal transcribed spacers of ribosomal operon allowed to identify new taxa of potentially endemic cyanobacteria among the studied strains. The high level of similarity of 16S rRNA gene sequences of soil cyanobacteria with those previously detected in the water bodies of the Larsemann Hills confirms their ability to spread beyond the limits of individual ecological niches and to adapt flexibly to contrasting environmental conditions.

The effect of long-term use of nitrogen, phosphorus and potash fertilizers and their combinations (N, P, K, NP, NK, PK and NPK) on chang in sod-podzolic heavy loamy soil (Albic Retisol (Abruptic, Aric Loamic)) was studied the content of gross potassium and its easily exchangeable, exchangeable and non-exchangeable compounds. The research was carried out in a meter layer of soil under the conditions of a long-term stationary experiment laid down in the Perm Region in 1978. In the experiment, ammonium nitrate or urea, double or simple superphosphate and potassium chloride were used. The dose of fertilizers was 90 kg/ha in the primary plant food. Long-term application of potassium chloride in pure form and in combination with superphosphate and nitrogen fertilizers (K₉₀, (PK)₉₀, (NK)₉₀, (NPK)₉₀) provided an increase in the gross content of potassium in the arable soil layer by 1.1–1.2 times and its various compounds by 1.1–2.8 times (relative to the control variant). A narrowing of the ratio of non-exchangeable forms of potassium to exchange forms is noted here. Changes in the meter layer of soil depended on the combination of fertilizers, the studied form of potassium compounds in the soil. The introduction of only nitrogen and phosphorus fertilizers (N₉₀, P₉₀, (NP)₉₀) without compensation for potassium removal during five rotations of the eight-field field crop rotation led to a decrease in the reserves of exchangeable and non-exchangeable potassium compounds in the 0–40 cm layer by 15–20%. The minimum level of potassium exchange compounds in sod-podzolic heavy loamy soil in a layer of 0–20 cm was 108–112 mg/kg.

The pollution of the topsoils of the city of Gusinoozersk (Republic of Buryatia) under the influence of emissions from State District Power Plant (SDPP) which used the Okino-Klyuchevskiy brown coal as fuel was studied. The content of 14 elements (Sr, As, Co, Mo, Sb, V, Cu, Ni, Cr, W, Zn, Bi, Cd, Pb) in bulk samples, as well as in the fraction of physical clay (particles with a diameter <10 µm, PM10) and in samples of brown coal and ash from the SDPP. Strontium, As, Co, Mo, Sb, V are the priority pollutants in the soils of Gusinoozersk with higher concentrations of most elements in the PM10 fraction. Soils and the PM10 fraction in the industrial operating subzone are the most polluted with Sr, As, Co, V, Cu, Mo, Ni, Cr, which are contained in the fly ash of the Gusinoozerskaya SDPP. Most of the territory (57% for soils in general and 47% for the PM10 fraction) is characterized by a low level of pollution (Zc = 8–16). Arsenic poses the greatest environmental hazard; in the PM10 fraction, its concentrations exceeded the MPC in 90% of the studied samples. In soils and their PM10 fraction, the leading factors for the accumulation of elements are the content of Fe₂O₃, organic matter, soil texture, alkaline-acid conditions, and belonging to a functional zone, which determine the formation of various classes of geochemical barriers. The polluting effect of brown coals depends on the content of heavy metals and metalloids in them. Comparison of the chemical composition of the Okino-Klyuchevskii brown coal and ash from the Gusinoozerskaya SDPP and the Kansk-Achinskii coal and ash from the Central Thermal Power Plant of Severobaikalsk showed that the brown coal and ash from Severobaikalsk were slightly enriched in metals and metalloids, which significantly reduced their accumulation in soils.

Natural reforestation on the abandoned arable lands is one of the characteristic processes that triggers the transformation of soils, accompanied by the change in the abundance, biomass, and taxonomic structure of the soil macrofauna. The assessment of the restoration potential of the soil properties and soil macrofauna to the natural state, the duration of this period, the dynamics of soil organic carbon stocks, and the role of macrofauna in this process at different stages of post-agrogenic successions is relevant for prediction of changes in ecosystem components and their role in the storage of organic carbon under various land use scenarios. The work is based on the data on organic carbon reserves, morphological properties of soils, abundance, biomass and taxonomic structure of the soil macrofauna of arable lands, primary forests and 5 stages of pine forest restoration (fallow meadows and pine forests of different ages) at the Smolenskoye Poozerye National Park (Smolensk region). It was revealed that in the soils of the 85–100-year-old pine forests, signs of plowing are preserved in the form of the smooth lower boundary of the humus horizon. At the same time, signs of soil regradation appear already at the meadow stage and are expressed in the formation of a thin humus horizon penetrated by roots, which transforms further at the next stages. In the litter and mineral part of the soil, the carbon stocks change non-monotonically with a maximum at the meadow stage and a minimum in 70–80-year-old forests. By the age of 80, the stock of organic carbon in the mineral part of soils is almost restored to the background values. The composition of soil macrofauna changes drastically during the transition from meadow to forest communities. At the initial stages (in agrocenoses and fallow meadows), the fauna of mineral soil horizons predominates: endogeic earthworms and larvae of lamellar beetles. Further, the fauna of organic horizons is restored, among which there is a high proportion of saprophages – epigeic and epi-endogeic earthworms, which contribute to the differentiation of litter. The biomass of saprophages has a negative correlation with the carbon reserves in the mineral part of forest soils, the thickness and reserves of organic carbon in the litter, and a positive correlation with the share of the easily decomposable litter fraction.