Beech (Fagus sylvatica L.) is one of the most important broadleaved trees species in Central Europe. Beech forest stands provide many important ecosystem services, for example timber. Managed beech forest stands form a closed canopy. This canopy is disturbed mostly during shelterwood cutting, which modifies environmental conditions in forest understory through increased sunlight flow to the forest floor. These changes affect assemblages of forest animals, mostly invertebrates. The aim of our study was to evaluate how selected ecological factors altered by anthropogenic disturbances in forests ecosystems affects arachnid communities (Arachnida:Araneae, Opiliones). Specifically, we aimed to (i) determine the structure, diversity, and abundance of epigeic spider communities and identify the change of spider distribution at varying levels of canopy opening, (ii) determine the affect of the canopy opening on the epigeic harvestmen assemblages, (iii) characterize the communities of the harvestmen in beech forests modified by forest management and (iv) identify the influence of ecological factors and biological interactions on the structure of arboreal spider communities in tree cavities. Overall, we collected 17,359 specimens of spiders (176 species, 27 families) and 1,834 specimens of harvestmen (16 species, 4 families). Our results confirmed significant influence of the size of canopy opening on the diversity, abundance, and structure of the spider communities; however we did not find this influence on the harvestmen diversity. The number of harvestmen in open canopies was twice as high as in the closed canopy habitats. We found that, in addition to the influence of abiotic factors (season, type of bark), the intraspecific predation between spiders and the presence of the bird predator significantly influence the occurrence of arboreal spiders and the composition of individual spider guilds.