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The diversity and sustainability of species composition are important topic of forest research. The possibility to observe the coexistence of tree species in a given forest patch and their succession in the next generation is limited because there are few forests unaffected by management activities. For this reason, the study was conducted in the oldest part of the Białowieża National Park, called Strict Reserve. The purpose of the research was to determine the relationship between the quantity of individual tree species in the overstorey (the standing volume of trees with the diameter at breast height d≥8 cm) and regeneration layer (the total height of trees with the diameter at breast height d<8 cm or height h≤1.3 m) as well as the relationships between those stand layers. Multiple regression and canonical analysis were used to determine the relationships between 12 tree species (tab. 1). The research material was the results of measurements of 920 concentric sample plots conducted in 1995 and 2005. In the overstorey, the correlation coefficient between the standing volume of a given tree species on sample plots and the standing volume of other tree species assumed for each species both significant positive values (species ‘co−occurrence’), significant negative values (species ‘avoidance’) and close to zero values (fig. 1). The same was true for the regeneration layer (fig. 2). In eight cases the correlation between the total height of trees of a given species in the regeneration layer and the standing volume of trees from the overstorey showed the highest positive values when referred to the ‘regeneration−overstorey’ relationship of the same species (fig. 3). The same referred to the ‘overstorey−regeneration’ relationship (fig. 4). Eight of the canonical variables turned out to be significant (tab. 2). For the first canonical variable, standing volume of hornbeam in the overstorey (Gb_m) showed the highest absolute value of the loading factor in the first dataset, while the variable the total height of hornbeam trees in the regeneration layer (Gb_o) – in the other dataset (fig. 5). The total redundancy was 20.7%, which means that such part of the variance of the total height of individual tree species in the regeneration layer could be explained by their standing volume in the overstorey. The sequence of tree generations understood as the relationship between species composition of the regeneration and overstorey layers was associated with life strategies of tree species.
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