Abstract
The paper analyses the influence of auxiliary trees species on selected qualitative characteristics of the parent oak stand aged 100-120 years from the tending aspect point of view. Stand structure described by relative height position, and stem straightness and branchiness as the main qualitative parameters were studied on 162 trees in three different forest stands: (i) without woody understorey, (ii) with understorey dominated by European hornbeam with an admixture of small-leaved linden and field maple, and iii) with understorey dominated by small-leaved linden. The results showed a positive effect of auxiliary tree species on the oak quality (straightness and branchiness of stems) in the lower part of the stem. Under the assumed elimination of genetic influences, better qualitative parameters of oak could be explained by the occurrence of auxiliary trees in the understorey.