Applied nucleation in the restoration of a suitable tree species composition in a protected forest

Applied nucleation is one of silvicultural measures used in the afforestation of new areas and reclamation or rebuilding of the forest species composition. It involves sawing or planting small patches of trees, or nuclei as focal areas for succession, which spread out into the environment as soon as they produce seeds. The aim of the study was to create a plan of planted nuclei that facilitate, in the long term, the enrichment of the species composition and gradual reconstruction of forests in the Stołowe Mountains National Park (PNGS), south−western Poland. The plan was assumed to comprise the locations of nuclei with an indication of tree species designated for planting in a given nucleus. Stand descriptions and maps from 2014 were used to determine: (1) the expected proportion (tab. 1) as well as the need to change of the proportion of individual tree species (tab. 3), (2) the urgency of actions to be taken due to the difference between the desired and actual proportion of a given tree species in individual stands (tab. 2), (3) the proportion of nuclei with a given tree species (tab. 3) and (4) the location of nuclei (200 in total) taking into consideration the local needs to increase the proportion of a given species. To determine the proportion (and then the number) of nuclei with a given tree species we took into account: (1) the difference between the present and desired proportion of a given species (considering the most numerous one), (2) the frequency of species as desired admixture or co−dominant species, and (3) the occurrence of species in rare but important habitats, e.g. along streams or ravines (tab. 3). A map of the distribution of stands where introduction of a given tree species is desirable, including information on the urgency of this treatment was prepared (fig. 1). The PNGS forest area was divided into patches using polygons of different shape and area. The boundaries of the polygons were drawn separately for each tree species in such a way that the number of patches was equal to the number of nuclei designed for planting, and the number of stands in the two highest planting urgency classes within each of these patches was equal. One nucleus of a given tree species was planned to be established within a patch. Only proportion of European beech, silver fir and wych elm was lower than desired (tab. 3). Such an assessment did not reflect the scarcity of species in individual stands. In more than thousand cases, the urgency of introduction of a given species was very high (tab. 4). It was essential to establish some nuclei in a significant part of the PNGS forests (fig. 2)