Different approaches were applied to assess soil moisture optima and tolerance of the ecological niche temporal projection of terrestrial invertebrates within an experimental polygon created to investigate the reclamation processes after deep underground hard-rock mining in the Ukrainian steppe drylands. Sampling was carried out in 2013–2015 on a variant of artificial soil (technosols). To investigate the spatiotemporal variation in the abundance, species richness and species composition of invertebrate assemblages the animals were sampled using pitfall traps. The readily available water for plants, precipitation, wind speed, atmospheric temperature, atmospheric humidity, and atmospheric pressure were used as environmental predictors. The two-dimension geographic coordinates of the sampling locations were used to generate a set of orthogonal eigenvector-based spatial variables. Time series of sampling dates were used to generate a set of orthogonal eigenvector-based temporal variables. Weighted averaging, generalized linear mixed models, Huisman-Olff-Fresco models expanded by Jansen-Oksanen, correspondence analysis, and constrained correspondence analysis were used to estimate soil moisture species optima and tolerance. The moisture content in the technosols was revealed to be the most important factor determining the temporal dynamics of terrestrial invertebrate community in conditions of semi-arid climate and the ecosystem which formed as a result of the reclamation process. The species response to the soil water content is affected not only by the soil water content but also by the complex of the other environmental, temporal, and spatial factors. The effect of other factors on the species response must be extracted previously to find real estimations of the species optima and tolerance.

The paper assesses the effect of transformation of soil physical properties on the abundance of micromolluscs in the conditions of an urban park. The studies were carried out in Novooleksandrivskiy Park (Melitopol, Ukraine). An experimental polygon was represented by 7 transects with 18 sampling points in each. The interval between the points in the transect, as well as the interval between transects, was 3 meters. The total area of the polygon was 1,134 m2. The tree species growing within the polygon were Quercus robur, Sophora japonica, and Acer campestre. Shrubs were represented by Ulmus laevis, Tilia cordata, Celtis occidentalis, and Morus nigra. The locations of the trees and shrubs were mapped. The crowns of tree and shrub plants formed a dense canopy and a shady light regime. The grass cover was practically absent. The soil mechanical resistance, soil aggregate-size distribution, electrical conductivity of soil, soil moisture and bulk density were measured. We recorded 618 individuals of Vallonia pulchella, 120 individuals of Cochlicopa lubrica, and 58 individuals of Acanthinula aculeata within the surveyed polygon. We extracted three principal components, which could explain 60.9% of the variation in the feature space of the soil properties. The principal component 1 explained 42.0% of the variation of the feature space and depended on the soil penetration resistance throughout the whole profile, aggregate composition, density, electric conductivity and moisture content of soil. This component reflected a tendency for soil penetration resistance and soil density to increase near recreational trails. The principal component 1 was used to indicate the gradient of recreational transformation of the soil. The principal component 2 was able to explain 10.6% of the variation in the feature space. It negatively correlated with the distance from the recreational trail, soil penetration resistance at the depth of 35 cm or more, soil electrical conductivity, and the proportion of aggregates greater than 3 mm in size. This component positively correlated with soil penetration resistance at 0–5 cm depth and the proportion of aggregates less than 0.5 mm in size. This component can be interpreted as a "halo" from the recreational trail, or a gradient of indirect soil transformations adjacent to the zone of intense recreational load. The principal component 3 was able to explain 8.3% of the variation in the feature space. It positively correlated with soil penetration resistance at the depth of 20–40 cm, the proportion of 0.5–7.0 mm aggregates, and soil moisture. It negatively correlated with the proportion of aggregates larger than 7 mm and smaller than 0.25 mm. This component indicated a variation in soil properties that was induced by causes independent of recreational exposure. The extracted gradients of soil properties significantly influenced the abundance of micromollusc populations. The abundance of all species decreased after increase in recreational load. Micromollusc species responded to direct recreational exposure as plateau (C. lubrica) and asymmetric unimodal responses (V. pulchella and A. aculeata).

The paper reveals regularities of grass projective cover variation depending on the level of recreational transformation of public green spaces, taking into account stand density and soil electrical conductivity. The hypothesis that herbaceous cover is positively influenced by moisture and trophicity of edaphotopes and the stand is an antagonist of herbaceous cover is confirmed. The nature of intra-ecosystem relationships of the park stand is influenced by the level of recreation. Assessment of the level of recreational transformation of the grass cover of green areas of public use is performed on the example of the park Novoalexandrovsky of Melitopol. Within the city park, the grass layer is influenced by natural and anthropogenic environmental factors. Based on the data on the hardness of the soil quantified the level of recreational load and set the following levels of recreational load: low level, below a moderate level, moderate level, above a moderate level and high level. Stand density is an important natural factor that affects the herb layer primarily through the regulatory function of access to sunlight. Quantitatively, trophicity and moisture can be estimated using the electrical conductivity index, which depends on both the amount of salts dissolved in the ground liquid (trophicity) and the moisture content. The obtained data show that electrical conductivity of soil within the park is on the average 0,11 ± 0,0037 dSm/m and in 95% of cases varies from 0 (electrical conductivity below the lower limit of device sensitivity) to 0,19 dSm/m. Observed electrical conductivity values are much less than critical values, so within the park, excessive salinity is not a limiting factor for herbaceous plant growth. Projective cover of the herbaceous layer is on average 2,60 ± 0,11%. In 95% of cases this indicator is in the range of 0‒10%. The level of variability of projective coverage is rather high ‒ 96,48%. Distribution asymmetry is significant and positive, indicating a significant shift in the distribution of this indicator towards small values. The kurtosis is also significant and positive, which indicates the predominance of modal values compared to the random alternative. The distribution of the projective coverage can be described as a mixture of two distributions with a normal law. The component with a lower mean of 0,76 ± 0,59% is 46,0% of the mixture, and the component with a mean of 3,63 ± 2,24% is 54,0% of the mixture. It should be noted that the Kolmogorov‒Smirnov test indicates a low level of explanatory power even for such a complex model. Therefore, it should be assumed that the variation of the projective cover of herbaceous cover is determined by a number of significant factors. According to the quantitative indicators of vegetation cover, the following levels of recreational load can be distinguished: low (combines small and less than moderate levels), medium (combines moderate and above moderate) and high (corresponds to the high level). Differences in projective cover within the smallest and below moderate level on the one hand, and medium and above moderate level on the other hand, are not statistically reliable.

The article shows the possibility of assessing the level of recreational transformation of public green spaces in terms of the soil penetration resistance and proved that the profile distribution of soil penetration resistance values is an information valuable indicator for establishing the level of recreational load. The measurement of soil penetration resistance within the park Novooleksandrivsky (Melitopol, Ukraine) was performed at 179 points on a quasi-regular grid with a distance between the points of accounting 30–40 m. The soil penetration resistance was revealed to be naturally increases with the growth of the depth of the soil layer from 2.42±0.023 MPa in the soil layer 0‒5 cm to 9.86±0.078 MPa in the soil layer 95‒100 cm. The process of increasing soil penetration resistance with depth is not monotonous, resulting in the presence of local penetration resistance at a depth of 50‒55 or 55‒60 cm. The variability of soil penetration resistance within one layer, which is described by the variation coefficient, is in the range of 6.98‒20.54%. This indicator naturally changes by profile. The high level of variation is peculiar to the top layer of soil 0‒5 cm, where the coefficient of variation of soil penetration resistance is 12.94 %. It is proved that under the influence of recreation there is a formation of functional layering of soil, expressed in the existence of structures in which layers of soil with greater soil penetration resistance are degraded by layers of less penetration resistance. The presence of such features can cause a complex of negative phenomena, which are associated with restriction of moisture penetration into the soil, reducing the migration capacity of air in the soil, limiting the growth of root systems of plants and the movement of animals. Functional layering can form local waterproof horizons that will limit the soil’s ability to absorb moisture. Correlational analysis of the connection of soil penetration resistance and the indicator of recreational load allowed to establish that with the increase of recreational pressure soil penetration resistance increases. The established correlational dependence of soil penetration resistance indicators and the assessment of the level of recreational load allows us to consider the possibility on the basis of penetration resistance data to quantify the level of recreational load. We completed this task with the help of multiple linear regression with the procedure of step-by-step inclusion of predictors in the model. The regression model is statistically significant and has made it easy to explain 46% of the varying indicators of recreational load. The step-by-step inclusion procedure provided an opportunity to choose the 10 most informative predictors for use in the model. The following levels of recreational load were established: low level, below moderate, moderate level, above moderate to high levels, as well as the procedure for indication of these levels based on soil penetration resistance data at different depths. The levels of recreational load were indicated on the basis of the procedure of classification trees on the soil penetration resistance data

As a result of the experiment, the ecological niche of the micromollusc Vallonia pulchella on artificial soil-like structures was investigated, with use of the edaphic and phytoindication indices. The study was conducted in June 2019 at a research path within the Nikopol manganese ore basin (on pedozem). The experimental polygon consisted of 105 samples located within 7 transects (15 samples each). The distance between the rows in the polygon is 3 m. The average density of the investigation object is 1.18 specimens/m 2 . It is shown that the spatial organization of the micromollusc is structured under the influence of edaphic and phytoindication indices. The edaphic and plant factors can be considered as determinants of the ecological space of V. pulchella, which is accomplished within the framework of the theory of ecological niche. It is established that the average soil hardness increases with depth down the profile. The influence of the hardness of deep soil layers on the distribution of mollusсs, which occur mainly on the surface, can be considered as a result of indirect influence through the structure of vegetation. Micromolluscs give an advantage to the places with a dominance of aggregates, which belong to the category of agronomically valuable (size from 1-2 to 3-5 mm). Small (less than 0.25-0.5-1.0 mm) and large aggregates (more than 10 mm) negatively affect the number of V. pulchella. Phytoindication scales act as valuable indicators to describe the properties of the ecological niche of the investigated object. The micromolluscs V. pulchella give an advantage to the areas with high levels of carbonic salts, as well as with a low content of free nitrogen in the soil. The indicators of ombroclimate and termal conditions contribute to the increase in the number of molluscs. Further research will be directed to study the impact of vegetation on the ecological niche of the micromollusc Vallonia pulchella (Muller, 1774) with application of geostatic analysis.