Summary:

The study was conducted within the Bydgoszcz limits and in the vicinity of city Bydgoszcz at seven different habitats of Hierochloë repens presence: city district Fordon - (1), (2), (3) and (4); city district Kapuściska - (5), and Białe Błota near Bydgoszcz - (6) and (7). Samples for acarological analyses were collected from the plots covered with Hierochloë repens in spring (27 May) and autumn (28 October) 2014.
The density of oribatid mites on the sites with Hierochloë repens was highly variable. High density of these microarthropods was characteristic of plots (2) with Convolvulo-Brometum inermis, (5) with Arrhenatheretum elatioris and (7) covered with grassy herbaceous plants growing on fertile soils. Particularly low density of oribatid mites was observed for plot (3) with Koelerio-Corynephoretea and Festuco-Brometea communities and the lowest content of carbon and nitrogen in the soil. Depending on the site and sample collection time, four to 22 species of oribatid mites were identified. Statistical analysis (Mann-Whitney U test) of mean number of species per sample s identified two groups of plots for both sample collection terms characterized by either low (1.00-3.10) or high values (3.30-7.40) of this parameter. The first group included plots (1), (3) and (6), and the second (2), (4), (5) and (7). The following species of oribatid mites dominated on the plots covered with Hierochloë repens: Tectocepheus velatus - (1), (2) and (6); Scheloribates laevigatus - (3), Oppiella nova - (4), Eupelops occultus - (5), Liebstadia similis - (7).