Gorban V., Huslystyi A., Kotovych O., Yakovenko V.: Changes in physical and chemical properties of Calcic chernozem affected by Robinia pseudoacacia and Quercus robur plantings. EkológiaGrowth of forest plantations on soils causes changes in their properties. These changes, their behavior, and magnitude depend on the original soil characteristics and also on the effect of forest plantations being grown. In the steppe zone of Ukraine, Robinia pseudoacacia L. and Quercus robur L. are the woody species most widely used in planting of forest plantations on chernozem soil. Chernozem soil formed exclusively under zonal steppe vegetation and chernozem soil under Robinia pseudoacacia and Quercus robur plantations were studied in this work to analyze the changes in soil properties caused by growth of these tree species. Dry aggregate size distribution, density, particle density, total porosity, organic carbon content, cation exchange capacity, pH values, hydrolytic soil acidity and dry residue, and the available nitrogen, phosphorus, and potassium content were analyzed. The studies found that Robinia pseudoacacia and Quercus robur plantations contribute to an increase in the share of aggregates 2-1 mm in size, as well as formation of aggregate fraction >10 mm, which are completely absent in the Calcic chernozem developed under the steppe vegetation. An increase in the density and particle density, as well as a decrease in the total porosity values were observed under the influence of forest stands studied. This is more common with chernozem under Q. robur plantation. It was found that the carbon percentage decreased in chernozem under the influence of Robinia pseudoacacia growth (on average, 0.4% by a meter-deep layer), but under Quercus robur planting it increased (on average 0.3% by meter-deep layer). Effect of Robinia pseudoacacia plantings on chernozem was also manifested by a decrease in cation exchange capacity (on average, 11 cmol/100 g by a meter-deep layer). The growth of R. pseudoacacia and Quercus robur plantations results in decrease of pH values (0.2 by a meter-deep layer) and increase of hydrolytic soil acidity and dry residue in chernozem water extract. Effect of Robinia pseudoacacia planting leads to a decrease in carbon, nitrogen, and phosphorus content in chernozem. The change in chernozem properties under the influence of Quercus robur plantation is reflected in accumulation of these nutrients. Growth of Robinia pseudoacacia and Quercus robur plantations leads to a decrease in potassium reserves in chernozem, which may indicate its active uptake by these woody species. In general, Q. robur planting is characterized by a large positive effect on the physical and chemical properties of chernozem than Robinia pseudoacacia planting. The findings obtained serve as a ground for making a recommendation for growing Quercus robur plantations under climate conditions of the steppe zone of Ukraine in order to improve the zonal chernozems' state and fertility.

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The characteristics of important water-physical properties and water-balance monitoring results for Calcic Chernozems located in the zone of true steppe were provided. The differences between soil-hydrological constants in carbonated loess-like loam and organogenic horizons were established. The results of water-balance monitoring showed that the moisture has uneven distribution along the soil profile, and most of the active moisture (more than 90%) was accumulated within the range of depths from 0 to 150 cm. During the entire calendar year, the soil is characterized by a lack of moisture available to plants. There are no periods free from water deficit.

In conditions of increasing anthropogenic pressure on the objects of the natural environment, an objective assessment of the hydrochemical state of water bodies is necessary, taking into account background values of heavy metals, the presence of which is associated only with natural factors. Therefore, the aim of our studies was to determine the concentration of heavy metals in groundwater lying in different geological and geomorphological conditions in a territory remote from the large industrial centers – Dnipro and Pavlograd. As a result of the carried out researches it was possible to establish the qualitative and quantitative composition of microelements that are contained in the ground waters of Prisamarya Dniprovske. The most common microelements from those that were determined were zinc, strontium, iron and manganese. In the groundwater of the floodplain of the Samara River the most common are zinc, strontium, iron and manganese. A distinctive feature of the groundwater of the first above-terrace is the presence of a large amount of iron – an average of 2 mg/l3, while this is not observed in the groundwater of the floodplain and steppe areas. This can be attributed to the chemical characteristics of forest litter from needles which has an acidic pH reaction. In turn, with acid reaction, iron passes from the bound state to the free state and, together with the descending streams of water, migrates from the soil to the groundwater. Among the microelements of the second above-the-top terrace, zinc, copper, iron and manganese predominate. Other trace elements from those that were determined are absent, or their number is below the sensitivity limit of the device. With a deep bedding of groundwater (22 m) and their slow water exchange with surface waters among the microelements, zinc, cadmium, copper, nickel, cobalt, iron and manganese predominate. The direction of the migration of microelements in the system soil ↔ groundwater can be determined by calculating the concentration of chemical elements in the soil and groundwater contained. The concentrations obtained for lead, copper, nickel and manganese in the majority of the investigated objects turned out to be less than one, which indicates the predominance of processes of removal of microelements from soil to groundwater. At the same time for groundwaters of the first above-the-top terrace there is accumulation of such microelements as copper and manganese. Here the maximum value of the clark concentration for copper is 18.14, for manganese 14.66. Considering the absence of close proximity to the territory of the research of large industrial facilities and highways with intensive traffic, the indicators obtained by us can be used as background values in complex biogeocenological studies. In addition, the values obtained can be useful for assessing the hydrochemical and toxicological state of natural waters, as well as for the integrated ecohydrological assessment of water bodies in this region.

The spontaneous vegetation in permanent flooding zone around technogenic water bodies arising on former pastures due to underground coal mining in the Western Donbass basin (steppe zone of Ukraine) was studied in 2018–2019. Occurrence and abundance of herbaceous plants were taken into account in 36 vegetation plots over a total area of 0.8 km2 in different habitats: dry, wet and flooded. In total, 83 plant species belonging to 31 families and 66 genera were identified, among which perennials dominated. Strong negative Pearson’s correlation was found between the amount and abundance of plant species and soil characteristics across the studied habitats, where the joint action of all edaphic factors determined the mosaic appearance of transformed vegetation. The spontaneous vegetation of the least disturbed xero-mesophilic habitats was most similar to (semi)natural grasslands, while the vegetation of hygrophilic habitats had a complete mismatch. Surrounding grasslands were not the most important diasporas’ source for spontaneous succession in the disturbed zone, and many species were supposed to come from the more remote areas. Recovery of target vegetation did not occur for 25 years of permanent subsidence and flooding due to radical transformation of landscape and soil and appearance of completely inappropriate habitats. At the same time, the unusual species composition of spontaneous vegetation and significant number of rare and endangered plants indicate the formation of valuable biotopes in the subsidence and flooding zone.