Summary:

The aim of the present research was to compare the communities of oribatid mites (Oribatida) on the plantations of chokeberry (Aronia melanocarpa (Michx.) Elliott) and blackcurrant (Ribes nigrum L.) as well as to define the effect of mi-croirrigation on those Acari. The experiment was performed in degraded Phaeozems formed from sand, on shallow-deposited sand in Kruszyn Krajeński in the vicinity of Bydgoszcz. The soil reaction was slightly acid or acid and the differences in the acidity between chokeberry and blackcurrant were inconsiderable. The abundance of oribatid mites on chokeberry and blackcurrant plantations ranged from 3110 to 5290 individuals • m-2 and it was much higher, as compared with the neighbouring set-aside. The density of Oribatida on blackcurrant plantation was clearly higher than in chokeberry; however there was recorded no significant effect of the type of irrigation on the density. In total on both plantations there were reported 31 species of oribatid mites; mean species number s in blackcurrant was higher than in chokeberry. The dominance structure of oribatid mites on the chokeberry plantation was more even than in blackcurrant and in Tectocepheus velatus communities dominated mostly. The species preferred the blackcurrant plantation and irrigation stimulated its abundance. Chamobates schutzii, an oribatid mite, came second; it preferred the soil of chokeberry plantation; it was especially numerous on irrigated stands. Scutovertex sculptus also demonstrated some preference for chokeberry soil and no tolerance to irrigation. Whereas such oribatid mite species as Gymnodamaeus bicostatus, Metabelba pulverulenta,
Oppiella nova, Quadroppia quadricarinata and Damaeus sp. showed some pref-erence for the blackcurrant plantation.