Forty years spontaneous changes in species composition of natural and seminatural forest association in the Roztocze National Park, south-eastern Poland

Investigations were conducted in natural and semi natural forests, in the strictly and partially protected areas of the Roztoczanski National Park (south-eastern Poland). Measurements of tree stands were carried out in 12 rectangular study plots, each of 0.5 ha size, established in the nineteen sixties in 4 forest communities: Abietetum polonicum, Dentario glandulosae-Fagetum, Querco roboris-Pinetum and Leucobryo Pinetum as well as in secondary forest communities of the Querco-Fagetea and Vaccinio-Piceetea classes. All trees which diameter at breast height exceeded 7 cm were considered as a forest canopy trees, and the smaller ones as forest regeneration. In the latter category individuals which height exceeded 0.5 m were considered as saplings, and the ones below 0.5 m as seedlings. This year regenerations were considered as germinants. Measurements of the canopy trees included their diameters (measured in two perpendicular directions), heights and height of their crown base. Besides, each stand tree (both alive and dead) was numbered and its coordinates (x, y) within the plot were measured. Forest regeneration as well as shrubs were counted throughout the study plots (saplings) or in the sample subplots (seedlings and germinants) Regenerations in the sample subplots were labeled, described, and measured (height, diameter of their base and 3-years height increment). Injures from herbivores were estimated too. Dead lying trees were numbered, measured (length of the trunk, diameter - dbh) and their stages of decay has been estimated. In each small sample plot the species of vascular plants and bryophytes were recognized and described as well as main types of site substrates and solar circumstances were estimated. The main aims of this study was to answer the following questions: 4. What are the current directions of spontaneous transformations in the phytocoenoses examined in natural (virgin) and seminatural forests, especially as climatic changes, habitat eutrophication and plant cover changes related to them are observed? 5. Is spontaneous regeneration of the natural forest from previously planted stands possible, when human intervention ceases or is the stand conversion necessary? 6. Is the stand conversation really accelerate regeneration of natural forest communities or establishing their artificial character.