Bioindication potentials of the grass stand and soil macrofauna for assessing the level of anthropogenic transformation of an urban park are complementary

Changes in the environment induced by anthropogenic impact or natural stressors are subject to bioindication. Most often, the anthropogenic stressors are the main object of bioindication research. Hemeroby and naturalness are considered as indicators of the level of anthropogenic transformation of ecosystems. Hemeroby is frequently used to assess disturbances in different types of vegetation. However, this concept has rarely been used to assess the impact on animals. According to the method of indicator values, species richness of a community is a marker of bioindication potential. The article compares the patterns of response of species richness of soil macrofauna and herbaceous cover communities in a city park, taking into account gradients of environmental factors, naturalness, and hemeroby. Within the study area, test plots were located. Soil macrofauna samples were taken at 105 points in each of the test sites, and soil hardness, electrical conductivity and soil temperature, litter height, and grass cover height were also measured. A geobotanical description of the vegetation cover was made within each plot. In the survey plots, 7.6 ± 3.0 plant species were found in the herbaceous layer. In soil samples, 6.8 ± 2.9 species of macrofauna were found. With an increase in the number of plant species in the herbaceous layer, the number of soil macrofauna species showed a downward trend. An increase in the number of soil macrofauna species is accompanied by a decrease in both naturalness and hemeroby of the plant community. The naturalness index does not depend on the number of plant species, but the largest number of plant species was observed under conditions of naturalness level from 0 to 1. With an increase in hemeroby, the number of plant species increases, although this relationship also has a nonlinear component. The largest number of plant species is observed at hemeroby levels from 45 to 65. Environmental factors and indicators of hemeroby and naturalness were able to explain 27% of the variation in the number of soil macrofauna species. Humidity regime and continentality did not affect the number of species. Increased variability in moisture conditions, carbonate content, and indicators of frost and cryoclimate contributed to an increase in the number of invertebrate species. Increases in acidity, mineral salts, nitrates, and soil aeration had a negative impact on the number of soil macrofauna species. Soil properties were able to explain 21% of the variation in the number of soil macrofauna species. Environmental factors and indicators of hemeroby and naturalness were able to explain 72% of the variation in the number of herbaceous plant species. Increases in moisture, acidity, mineralization, thermocline, and cryoclimate indicators had a negative impact on the number of plant species. Biological indicators can be used to assess complex environmental factors that are difficult to measure using instrumental methods. Bioindicators are also used to assess the level of anthropogenic transformation of ecosystems. The key concepts for solving this problem are the naturalness and hemeroby of plant communities, which are used as markers of ecosystem disturbance in general. Vegetation cover as a source of bioindication information can provide a biased assessment of the level of anthropogenic transformation due to its greater sensitivity to certain types of anthropogenic pressure. The potential of soil animals as a source of information on the level of anthropogenic transformation in the urban environment is quite significant. Species richness is a marker of the potential ability of a plant or animal community to provide reliable bioindication information. The bioindication complementarity of animal and plant communities is that the highest species richness of soil macrofauna is observed at a relatively low level of species richness of plant communities. Therefore, soil macrofauna can complement and clarify estimates of the level of anthropogenic transformation made using plant communities or can be an independent source of information for such estimates.