EN
Changes in the herbaceous layer (vascular plants), taking place between 1959 and 2016 on the permanent study plot in the compartment 319 of the Strict Reserve in the Białowieża National Park are presented. Zaręba [1972] presented phytosociological research carried out in 1959 on the 1.2 ha plot. The author established 10 relevés (size between 100 and 400 m²), in which in total 91 different species of vascular plants were noted. In 2016, the similar study was conducted, using slightly modified methods (the inventory of plants involved the total area of the study plot). The comparison of data recorded during both investigations revealed that the total number of plant species declined from the initial 91 to current 83. During the ca. 60−year long period, 43 plant species disappeared completely and were replaced by 35 new species. In the declining group, almost the half (20) were species important from the point of view of nature conservation, including four Red List species (Arnica montana, Goodyera repens, Lathyrus laevigatus, Trolius europaeus), 10 plant species protected by law, and several other precious species related to rare and declining woodland community types. The obtained results confirm the findings of other authors describing unfavourable changes in the flora of the Białowieża Forest during the past several tens of years. The floristic richness is an important part of the overall biodiversity of Białowieża Forest. It appears that strict protection does not secure the maintenance of this key component. Thus, an attempt to preserve diverse values of Białowieża Forest on a sustainable basis should, first of all, look for a proper balance between strict and active protection. The later can (and should) be integrated within the multifunctional forest management, conducted on the prevailing area of the Białowieża Forest.