Volume 52, Nº 10 (2019)

This study aims to determine variation in soil physical, chemical and microbial properties along altitudinal gradients in fragile mountains region of the Karakoram. The soil samples were collected at the altitude ranging from 2787 to 3600 m from the alpine forest of the Bagrot valley, northern Karakoram, Pakistan and analyzed for various physical, chemical, and microbial parameters. The results indicate that there is a strong relationship of the soil parameters with altitude (p ≤ 0.01). With increasing elevation, soil bulk density, sand content, electrical conductivity (EC), pH, CaCO₃ content, and 16S rRNA decreased significantly, while total porosity, saturation percentage, soil organic matter (SOM) contents, soil nutrients, and fungi-to-bacteria ratio increased with increasing altitude. These findings increase the understanding of dynamics of soil properties and enhance predictions of the responses of alpine soils to global warming.

Competitive adsorption of scandium, yttrium, and lanthanides was studied for soddy-podzolic and gray forest soils and for leached chernozem. The chemical behavior of scandium significantly differs from that of other rare-earth elements (REEs) by the quick reaching of equilibrium in the soil–solution system and by the fact that its adsorption is not described by the Langmuir equation unlike yttrium and lanthanides. Individual chemical properties of REEs are the most pronounced in the experiments on competitive adsorption. In the yttrium–lutetium sequence, there is a tendency for a gradual decrease in the maximal adsorption capacity (from 0.025 to 0.010 mmol/kg in soddy-podzolic soil and from 0.100 to 0.050 mmol/kg in leached chernozem) and more pronounced increase in the Langmuir adsorption constants (from 5000 to 25 000 L/mmol in soddy-podzolic soil and from 5000 to 40 000 L/mmol in leached chernozem). This reflects the competition between different elements for soil sorption sites, which is directly related to the change in ionic radii of the elements (so-called “lanthanide contraction”). Unlike other soils, leached chernozem absorbs a large amount of REEs and provides their stronger fixation.

The isotopic composition of nitrogen in soils and plants may be an indicator of transformation of its compounds and sources of N nutrition of plants. Natural ¹⁵N abundance (δ¹⁵N) was determined in soils (the total, ammonium, and nitrate nitrogen) and in plant leaves and roots of four tundra ecosystems in the Khibiny Mountains. The studied soils (Folic Leptic Entic Podzol and Leptosols) significantly differ in N availability, and plants are represented by the species, forming ectomycorrhiza, ericoid mycorrhiza, and arbuscular mycorrhiza, as well as by the species, which usually do not form a mycorrhiza. The range of δ¹⁵N in soil inorganic compounds is from –16.2 ‰ in nitrates to +6.4‰ in ammonium, which reflects the correlation between the activities of N-mineralization and nitrification and δ¹⁵N-\({\text{NH}}_{4}^{ + }\), as well as a potentially strong effect on the isotopic composition of nitrogen in plants. The value of δ¹⁵N in plant leaves and roots changes in a narrower range (from –7.3 to +2.4‰), which may be related to N uptake from different sources and to fractionation of N isotopes during N assimilation. Roots are ¹⁵N-enriched in comparison with leaves in most of the studied plant species, which corresponds to the concept of mycorrhiza participation in N nutrition of plants. Regardless of the type of mycorrhizal symbiosis, the difference in δ¹⁵N between roots and leaves of most plant species decreases contrary to N availability in soils.

Soil salinity is a major problem in Kerman pistachio (Pistacia vera) orchards which caused low pistachio’s productivity in recent years. Farmers excessively use gypsum and sulfuric acid amendments to remediate saline soils in their pistachio orchards overcoming this problem. The aim of this study was to investigate type of amendments and the pore volumes of water (PVs) required to efficiently leach excessive salts from saline-calcareous soil. Laboratory experiments were conducted using soil columns that were collected from a pistachio orchard near Kerman city. Four treatments, including irrigation water (control), sulfuric acid, gypsum, and dissolved gypsum were applied to remove salt from these soil columns with using different PVs of water. The concentrations of removed cations and salt from the soil columns were measured by analysis of effluent continuously. The results demonstrated that the effect of chemical amendments in removing soluble salts, sodium, magnesium and calcium was similar to irrigation water and did not differ significantly. Thus, irrigation water removed 62% of the total sodium, 73% of magnesium, and 70% of soluble salts from the soil column up to 1.5 PVs of effluent. Application of chemical amendments was not beneficial to infiltration rate in comparison with irrigation water. Thus, the efficiency of only 1.5 PVs of irrigation water without any amendments can be recommended as the appropriate strategy for practical reclamation of the studied soil.

In the course of field and laboratory studies, the activities of nitrogen fixation, denitrification, CO₂ emission, and methane formation in an oligotrophic peat soil were determined at the Staroselsky Mokh Station of the Central Forest State Natural Biospheric Reserve in Tver oblast. The high intensity of methane oxidation was found in the oligotrophic peat soil. It was supposed that methane under these conditions could be used by diazotrophic bacteria as energy source. Determination of the nitrogen-fixing activity of oligotrophic peat soil in the presence of methane showed a sharp increase in the nitrogenase activity. It is important to emphasize that nitrogenase activity was higher in the presence of methane, even in comparison with the variant with glucose. The preferential absorption of nitrous oxide by the upper horizon of oligotrophic peat soils was found, which allowed us to consider these ecosystems to be a natural sink for N₂O.

The cacao plantations in Sulawesi Island, Indonesia are responsible for a great part of the local economy; however, their soils still need to be deeply explored. Our study focused on evaluation of the microbial communities in cacao soils according to their location and applied management system. Four soil samples were taken from six cacao farms under two kinds of systems (conventional and organic). 16S and ITS rDNA amplicon sequencing analyses of soils were also performed to identify bacteria and fungi, respectively, whereby their relative abundance and diversity were determined. In general view, the bacterial and fungal communities were affected by management system at the local and general levels. Bacterial analyses indicated that the number of operational taxonomic units and bacterial diversity were higher under the organic system in Kulawi, Palolo, and Poso farms. The composition and biodiversity of fungi were clearly different between organic and conventional systems and between different places (coastal and inland). The effect of agricultural management was observed in each location individually and in general.

An experiment on the transformation of test biotite of the clay fraction (<1 µm) and the medium silt fraction (5–10 µm) immersed into the AELоа horizon of podzolic soil for one or three years was performed. Partial transformation of biotite in the medium silt and clay fractions into irregular biotite–vermiculite under the modern pedogenesis conditions within one year of incubation in the AELоа horizon of podzolic soil was demonstrated. A considerable part of biotite was transformed into irregular biotite–vermiculite and biotite–vermiculite–pedogenic chlorite, and small amounts of vermiculite and pedogenic chlorite were formed after three years of incubation in the soil. Biotite transformation into expandable minerals was accompanied by the decrease in the layer charge, loss of interlayer K, and loss of Mg and Fe from the octahedral lattice. Mica transformation was most significant in the medium silt fraction: the overall decrease in the share of nonexpandable biotite layers and in the thickness of biotite crystallites after three years of incubation was more pronounced in this fraction than in the clay fraction.

Among residents of the Bryansk and Gomel regions of Russia and Belarus, who were exposed to the so-called “iodine attack” as a result of the 1986 Chernobyl Nuclear Power Plant accident, there was a sharp increase in thyroid disease. Therefore, the natural iodine deficiency in soils was an important additional risk factor that could cause adverse reactions primarily among children, for whom the incidence of thyroid cancer in Belarus increased by 76 times. Potatoes belong to one of the main ration-forming foods for local population. In this regard, in 2007–2017, 97 settlements were surveyed in the affected areas, in which samples of local arable soils and potatoes were taken from 138 private subsidence farms (PFs).The iodine content in the studied soils of the private farms of the Bryansk region ranged from 0.11 to 3.5 mg/kg (air-dry weight). The content of iodine in potatoes grown on these soils varied within a considerably wider interval: from 0.002 to 0.119 mg/kg (wet weight), averaging 0.033 mg/kg, which indicates a generally low iodine transfer to this particular product. The data obtained deserve attention when organizing monitoring and carrying out measures for the prevention of iodine deficiency.

We analyzed the original and most developed environmental legislation of the Netherlands, Germany, the United States, and Canada, as well as the systems of Finland, the Czech Republic, China, the Republic of South Africa, Australia, and New Zealand, which have a number of specific features in terms of the content of chemical elements in soils. We summarized environmental legislation principles and actions in cases of exceeding soil quality standards. Comparing methodologically close legislations, the specificity of calculation of a soil quality standard should be taken into account. The standards for the content of chemical elements are differentiated depending on the properties of soils in Russia, Germany, China, and the Czech Republic; land use is taken into account in Canada, Germany, the Republic of South Africa, China (only for agricultural land), Australia, New Zealand, and the United States. Synergism of negative effects on organisms in case of polyelemental contamination is taken into account in the standards of Russia for element pairs Mn + V and Hg + Pb and in the standards of the United States for all substances.

It has been experimentally shown that there are two ranges of water flow velocities, at which the erodibility of a monofractional soil (of aggregates 1–2 mm) sharply differs. In the low-velocity range, the erodibility varies from 171.53 to 3.17 m^–2 s² at an increase in the soil density from 1.2 to 1.5 g/cm³. In the range of high velocities, it varies from 36.88 to 0.88 m^–2 s². The simultaneous solution of equations for the two velocity ranges enables us to obtain the boundary values of the flow velocity. Above them, other erodibility values should be taken into account at calculations. The boundary velocities for the model soil are within 1.6–1.7 m/s. This is explained by the fact that at a slow flow, water removes aggregates, which have lost the contact with the main soil as a result of its peptization by water. At high-velocity water flow, aggregates are detached under the effect of hydrodynamic forces.