This paper tested the hypothesis that the placement of trees in the floodplain ecosystem leads to multiscale spatial structuring and plays an important role in formation of the spatial patterns of the soil macrofauna. The research polygon was laid in an Eastern European poplar-willow forest in the floodplain of the River Dnipro. The litter macrofauna was manually collected from the soil samples. The distances of the sampling locations from the nearest individual of each tree species were applied to obtain a measure of the overstorey spatial structure. The pure effect of tree structured space on the soil animal community was presented by the broad-scale and meso-scale components. The soil animal community demonstrated patterns varying in tree structured space. The tree induced spatial heterogeneity was revealed to effect on the vertical stratification of the soil animal community. The complex nature of the soil animal community variability depending on the distance from trees was depended on the interaction of tree species in their effects on soil animals. The importance of the spatial structures that interact with soil, plants and tree factors in shaping soil macrofauna communities was shown.

In the present investigation catena approaches to assess the landscape diversity of the “Dnipro-Orilsky” natural reserve was developed. Catena which lies in the reserve embraces flood and arena biogeocoenoses. The research was performed during the 2014– 2018. The two profiles were made at the “Dnipro-Orilsky” natural reserve within which main geomorphological landscape elements are presented. There are 29 sampling polygons within these p rofiles. The soil profile description, vegetation investigation, soil and soil animals quantitative assessment was carried out in each of them. In this publication we presented the results of sampling polygons 1–4, 25 and 26. The profile 1 best reflects the traditional view of catena: it goes from the highest places of the sand terrace (arena) to the lowest place (floodplain). But relief diversity is increased by the availability of small river Protich. It floodplain provides an alternative transit and accumulation gradient. It should be noted that the main part of the main slope profile does not fully meet the transit regime, as compiled by sandy soils, which are char- acterized by high filtration capacity. Therefore, the slope profile position is largely corresponded to eluvial regimes. The accumulative part of the profile which corresponds to the floodplain of Dnipro river is significantly influenced by impact of the flood factor than the accumulative part of the profile which corresponds to the floodplain of Protich river. The soils within floodplain of Protich river have more quantity of clay. Clay soils are characterized by capillary properties, as soil salinization is common in the floodplain of Protich river. Alternative profile 2 includes Orlov valley. This element of the landscape is accumulative, but not affected by flood factor. In the biogeocenotic context catena sampling points were considered as being composed of pedocatena, phytocatena and zoocatena. The biogeocenotic approach is the chain that connects the landscape structure, the diversity of soil cover, and diversities of the plant and animal communities. The functional, spatial and temporal properties of ecosystems in landscape context can be expressed by catena. The biogeocoenosis concept is a basis for integration of the pedocatena, phytocatena and zoocatena. Catena approach is the framework for a monitoring system landscape diversity both at the level of individual component biogeocoenosis (edaphotop, phytocenosis, and zoocenosis) and biogeocoenosis level in terms of its horizontal and vertical structure and at the landscape level as a whole intercon- nected system. The traditional idea of catena as a set of eluvial, transit and accumulative positions in a complex and diverse landscape is not able to cover the most important environmental gradients modes. The complexity of the landscape is due to relief diversity and the effects of anthropogenic transformation biogeocenotic cover. Catena therefore can be seen as a multilevel hierarchical system of the biogeocenotic polygons needed to consider the diversity of physiographic conditions and anthropogenic gradients.

Investigated polygon laid in the northeastern part of the "Dnieper-Orilskyy" natural reserve. Five test plots were laid within polygon. The most common moisture conditions within the explored catena meet meadow steppe regime. For most studied soil moistening the soil plays an essential role in the water regime. Groundwater was at a depth that exceeds the depth of the cut in chornozem-like pine-forest soil and in a sod-forest chornozem-like soil. In other soils, the water level was 155 cm in sod-forest chornozem-like soil, 98 cm in alluvial meadow soil and 83 cm or 135 cm in alluvial meadow marsh soils. The conditions of the salt regime can be attributed to the soils of the studied catena categorized as poor soils. The chornozem-like pine-forest soil has a wide range of variability salt regime, while the alluvial meadow marsh soil has a wide range of variability humidity conditions. The most favorable conditions for plants of the mesotrophic group formed in the meadow alluvial soil and in sod-forest chornozem-like soils and for semioligotrophic-in sod-forest chornozem-like gleic soil. Forest ecosystems within catena are characterized by similarity of water regime conditions. Sandy steppe ecotopes in the catena are characterized by the highest volatility of the moisture conditions. The most common acid regime within catena can be considered as characteristic for weak-acid soil / neutral soils. The acarbonatophiles are the most typical for catena studied. Plants of this ecological group are living in neutral ecotopes and kept the minor content of carbonates in the soil. The alluvial meadow marsh soil is characterized by smallest carbonates level, and the alluvial meadow solohchak soil is characterized by the largest carbonates level. In the chornozem-like pine-forest soil the effervescence from HCl treatment war not revealed. The depth of effervescence of processing 10% solution of HCl is 64 cm in sod-forest chornozem-like soil, 31 cm in alluvial meadow soil, 18 cm in alluvial meadow marsh soil or from the surface. The sod-forest chornozem-like soil boils on the surface. Sod-forest soil chornozem-like boils from the depth of 127 cm. The content of digestible forms of nitrogen is an important aspect of the edaphotope trophicity. Within catena the most typical is an ecotope where conditions are favorable for nitrophiles. The lowest level of nitrogen nutrition set was found in sandy steppe (chornozem-like pine-forest soil), and the highest-in the forest ecosystems (sod-forest chornozem-like soils). The subaerophiles are the most typical for catena studied. The marsh biogeocoenosis are characterized by significantly aggravated conditions of aeration. It generated conditions conducive to subaerophobes-aerophobes.