The ecological restoration of urban parks is used to increase their recreational attractiveness, improve air quality, mitigate urban heat island effects, improve stormwater infiltration, and provide other social and environmental benefits. The dynamics of plant communities after urban forest restoration requires investigation. The study assessed the impact of urban park reconstruction on the state of grass cover, phytoindication of changes in light regime caused by park reconstruction and found out the dependence of reliability of phytoindication assessment on the number of species in the relevant area. The study was conducted in the recreational area of the Botanical Garden of the Oles Honchar Dnipro National University (Ukraine). A tree plantation was created after the Second World War in the location of a natural oak forest. In 2019, a 2.8 ha area of the park was reconstructed. The samples were taken within polygons, two of which were placed in the reconstruction area and two of which were placed in a similar section of the park where no reconstruction was performed. During the reconstruction process, walkways were rebuilt, shrubs were removed, old, damaged trees were removed, and tree crowns were trimmed. Juvenile trees were planted in place of the removed old trees. Old outbuildings, which greatly impaired the aesthetic perception of the park, were also removed. Transport and construction machinery was involved in the reconstruction. A total of 65 plant species were found within the studied polygons. The number of herbaceous species in the park area after reconstruction was higher than without reconstruction. The crown closure in the reconstructed area was significantly lower than that in the untreated conditions. The phytoindication assessment showed that the light regime varies from the conditions suitable for the scyophytes (plants of typical foliage forests) to the conditions suitable for the sub-heliophytes (plants of light forests and shrubberies, or high herbaceous communities; lower layers are in the shade). The light regime in the park area after reconstruction was statistically significantly different from the regime in the untreated park area. The lighting regime after the reconstruction was favourable to sub-heliophytes, and without reconstruction the regime favoured hemi-scyophytes. Tree canopy crown closure negatively correlated with grass height and herbaceous layer projective cover. The tree canopy crown closure, grass height, and herbaceous layer projective cover were able to explain 86% of the phytoindication assessment of the lighting regime variation. These parameters negatively affected the light regime. The prospect of further research is to investigate the dependence of indicative reliability of the assessment of other environmental factors with the help of phytoindication depending on the number of species. In addition to the indication of traditional ecological factors it is of particular interest to clarify the aspect of the dynamics of hemeroby indicators as a result of park reconstruction.

The aims of this research are to assess the relationship between the concepts of hemeroby and naturalness of plant communities and to test the hypothesis about the ordinal nature of the response of social behavior types of plants under anthropogenic influence. Study area is the recreational zone of the Botanical Garden of Dnipro National University, named after Oles Gonchar, Dnipro City, Ukraine (48.43°N 35.05°E). Four polygons (105 relevés in each) were examined. Two polygons were in the zone after park reconstruction, and two were in the zone without reconstruction. The vegetation community ordination was performed using RLQ analysis. The Q-table was represented by eight dummy variables, which indicated social behavior types. The most important predictors of naturalness were aggressive alien species and invaders and weeds (positive dependence) and disturbance tolerants (negative dependence). The most important predictors of hemeroby were aggressive alien species (negative dependence) and ruderal competitors, invaders, and disturbance tolerants (positive dependence). Naturalness and hemeroby reflect different strategies for transforming a plant community and are not completely symmetrically opposed concepts. The response of a plant community is multivariate, so the naturalness metric based on the social behavior types is only able to distinguish well between the extreme states of a plant community, but is a poor measure for a more detailed assessment of naturalness.

Parks perform a wide range of ecosystem services in urban environments. The functional importance of parks depends on the composition and structure of the tree stand and the specific influence on soil and microclimatic conditions. The article reveals the dependence of soil and microclimatic properties on the structure of the crown space of a park stand. Spectral indices were also shown to be applicable for predicting the spatial variability of soil and climatic properties and indicators of crown space. Soil properties (temperature, moisture, and electrical conductivity in the 5–7 cm layer) and microclimatic parameters (light exposure, air temperature, and atmospheric humidity) were measured in the park plantation using a quasi-regular grid. The canopy structure and gap light transmission indices were extracted from the true-colour fisheye photographs. Thirty species of trees and shrubs were detected in the stand and understory. Robinia pseudoacacia L. was found most frequently (24.5% of all tree records). Acer negundo L. and A. platanoides L. were also frequent (12.4% and 15.5%, respectively). The first four principal components, whose eigenvalues exceeded unity, were extracted by the principal components analysis of the variability of ecological properties and vegetation indices. The principal component 1 explained 50.5% of the variation of the traits and positively correlated with the spectral vegetation indices. The principal component 1 reflected the variability of tree cover densities due to the edaphic trophicity. The principal component 2 described 13% of the variation in the feature space. This component correlated positively with the spectral indices. The principal component 2 was interpreted as a trend of vegetation cover variability induced by moisture variation. The principal component 3 described 8.6% of trait variation. It was most strongly correlated with the atmospheric humidity. An increase in atmospheric humidity was associated with an increase in the soil moisture and electrical conductivity and a decrease in the soil and atmospheric temperature. The principal component 4 described 7.5 % of the variation of traits. An increase in the values of principal component 4 was associated with an increase in the soil moisture and electrical conductivity and atmospheric moisture and was associated with a decrease in the soil and atmospheric temperature. The combinations of the trophotope and hygrotope create the optimal conditions for specific tree species, which is a condition for achieving the maximization of ecosystem services. The mineral nutrition conditions of plants and soil moisture exhibit spatial patterns that allow them to be considered in the design and management of park plantations. The ecological indices measured in the field were shown to be predicted using the vegetation indices. Multiple regression models were able to explain 11–61% of indicator variation. The regression relationships between markers of soil and microclimatic conditions and vegetation predictors are important for monitoring the condition of park plantations and evaluating the performance of park plantation management tools.

Horizontal structure of natural plant communities attracted the attention of researchers for a long time, while the problem of horizontal structure of urban park plantations was not studied sufficiently. Species richness of different tiers of park plantation in the large industrial city of Dnipro (Ukraine) was revealed in this study. Also features of variation in the structure of plant communities at different spatial levels were revealed, the influence of park plantation canopy on the understory and herbaceous layer of the park. There were 30 plant species in the tree layer of the park plantation. The most common species were Robinia pseudoacacia L., Acer platanoides L., A. negundo L., Gleditsia triacanthos L., Aesculus hippocastanum L., Populus carolinensis Moench. The variance-to-mean ratio revealed that 13 tree species were randomly distributed throughout the park, and 14 species were aggregated. The number of occurrences of a given tree species per site and variance-to-mean ratio were positively correlated. The numerous tree species showed a tendency of aggregated distribution within the park. Sixteen plant species were found in the understory. Among them, the most abundant species were Acer platanoides L., A. negundo L., A. pseudoplatanus L., Sambucus nigra L., Robinia pseudoacacia L. Eight species were found to be randomly distributed over the park area, and eight species showed an aggregate distribution. The number of species encountered in the understory and variance-to-mean ratio were positively correlated. In the herbaceous stand, 99 plant species were found, of which Chelidonium majus L., Viola odorata L., Impatiens parviflora DC., Parthenocissus quinquefolia (L.) Planch., Geum urbanum L. predominated. The variance-to-mean ratio of all species was significantly less than unity, indicating regular spatial distribution. The values of alpha- and gamma-diversity of the plant community in separate layers are very different. The highest gamma diversity was found for the herbaceous stand, while the diversity of the tree stand and understory was significantly lower. Alpha biodiversity of the tree stand and the understory did not practically differ. Beta diversity values between the layers are very close, and beta diversity is practically equal for tree stand and herbaceous layer. Thus, we can assume that the mechanisms of species turnover for the plant communities of different layers are determined by the common causes. The spatial broad-scale component was able to explain 8.2% of community variation, the medium-scale component was able to explain 4.2% of community variation, and the fine-scale component was able to explain 0.7% of community variation. The understory is the most sensitive to the environmental factors, the herbaceous stand is somewhat less sensitive, and the tree stand is the least sensitive to the environmental factors. The environmental factors in this study are represented by a set of variables. The spatial variation of the stand is predominantly influenced by the factors of trophicity and moisture of the edaphotope. These same factors also act on the herbaceous stand and understory, but along with them are included the environmental variables, which are determined by the architectonics of the crown space and thus the light regime, which is regulated by the tree stand. It is important to note that the variation of the communities of the different layers of the park plantation is subject to spatial patterns. The herbaceous and understory variation is more spatially structured than the tree stand variation. The spatial patterns can arise as a result of the influence of spatially structured environmental factors and as a result of factors of a neutral nature. The latter aspect of variation is best described by the pure spatial component of community variation.