Abstract

The aim of the paper was to determine the effect of microirrigation and organic fertilization on the structure of assemblages of oribatid mites in Silver birch and Scots pine cultivations under conditions of mulching with forest ectohumus. Investigations were conducted at Forest Nursery BiaÅ‚e BÅ‚ota, Forest District in Bydgoszcz (Poland). Separate experiments in Scots pine and S. birch stands were established in 2003; the single plot area measured 4 m² and contained 4 rows (4 m long). The soil samples for mites were taken twice a year (in May and October of 2003 and 2004). A total of 39 oribatid mite species were found in forest nursery cultivations of both tree species. Irrigation was found to be the factor which determined the mean number of species per sample in both plantations, as well as the density of oribatids, which were more numerous in S. birch stands than in that of Scots pine. Eurybionthic populations of oribatids – Oppiella nova, Oribatula tibialis and Tectocepheus velatus – were the most numerous in the study sites.Most of the species preferred specific ecological conditions which were created by high seedlings of S. birch which is characterized by abundant leaf-fall. Only the xerophilous Scutovertex sculptus was more abundant in Scots pine cultivation.

Key words: Forest nursery, irrigation, organic fertilization, mulching, oribatid mites.