Changes in population parameters of oribatids (Acari: Oribatida) of meadow habitats on the Transcarpathian Lowlands in the edaphotope humidity gradient

Among all abiotic factors, environmental humidity is of great importance for the formation of the population of oribatid mites. Most of the published works, both in the Transcarpathian Lowland and in Europe in general, concern the study of oribatid mite complexes in different types of zonal ecosystems, especially forest ones. In contrast, the population of oribatids of meadow habitats, which are the main type of intrazonal communities, has been studied at a fragmentary level. However, the question of the dynamics of the parameters of the populationof oribatids of meadow biotopes on the Transcarpathian Lowland in the edaphotopee humidity gradient stillremains unsolved. A study of oribatid complexes of xerophytic, mesophytic, hygrophytic and floodplain meadows has been conducted. It has been established that the edaphotopee humidity has a significant impact on the dynamics of oribatid mite communities in different types of meadows on the Transcarpathian Lowland. A correlation analysis was conducted, which showed a high level of dependence of the density of oribatids on soil moisture. The dependence of some parameters of the synecological structure of oribatid mites on soil moisture in different meadows has been established. Thus, the degree of correlation between the moisture factor and the species richness of oribatids in mesophytic meadows is the highest. This factor has a somewhat lower degree of dependence in floodplain meadows. Soil moisture has the greatest influence on the density of oribatids in hygrophytic meadows. A lowerdegree of correlation between density and humidity was found in mesophytic and xerophytic meadows. An analysisof the diversity indices of oribatid mite communities in meadow biotopes of the Transcarpathian Lowland was conducted, which confirmed the identified trend – a decrease in the level of species richness of oribatids in the gradient of decreasing soil moisture. The following indices were calculated: Margalef, Menhinik, Simpson, Shannon and Berger-Parker. For example, the Simpson index value is very sensitive to the dominant species in the studied biotopes, and the Berger-Parker index value is to the most numerous species. This feature of the last two mentioned indices allowed us to identify another trend – an increase in the proportion of dominant oribatid species is manifested with an increase in the humidity of the edaphotope. The Shannon index, given its sensitivity to rare species, allowed us to identify another pattern – an increase in rare forms of oribatids in the gradient of decreasing edaphotope humidity. The detected trend does not apply to the oribatid mite communities of hygrophytic meadows,which are rich in rare species.