Dynamics of tree species composition and characteristics of available space utilization in the natural forest of the National Nature Reserve Hrončokovský Grúň

The paper deals with changes in the diameter structure of particular tree species as well as with the selected production characteristics in the mixed virgin forest Hrončokovský Grúň. The object of the analysis was the diameter structure of particular tree species in developmental stages of virgin forest. The data were collected in the years 1972, 1982, 1992 and 2002 on permanent research plots 71.5 × 70 m (0.5 ha) in size. Diameter frequencies for particular tree species were approximated with the curves. The goal was to evaluate their mortality or vitality according to the strength of the correlation in developmental stages of the virgin forest. A strong correlation was confirmed in the advanced phase of the growth stage, whereas the strongest correlation was recorded for the ash. Beech as a virgin forest bearer had a medium strong correlation. For the advanced phase of the optimum stage lower values of the correlation coefficients were determined for all tree species. The growth vitality and thus lower mortality was characteristic of maple and ash. Beech as a structure bearer is characterized by higher mortality and therefore a weaker correlation. In the breakdown stage the highest mortality was found for the fir, which is confirmed by the lowest value of the correlation coefficient. In the advanced phase of the optimum stage the highest mortality was recorded for the beech. The analysis of growth and production relationships was conducted on the transects of 3 permanent research plots 10 × 71.5 m in size (i.e. total size of 2,145 m2). The analysis of the growth relationships between the crown and stem volume confirmed a strong correlation for beech and fir despite the fact they are present in the entire height profile of the virgin forest. The reason is that both of them are the shade-tolerant tree species. High correlation coefficients for maple and ash (R = 0.82 and R = 0.84) are the evidence of a distinctive influence of the assimilatory apparatus on the stem volume. The reason is the fact that both tree species are situated in the upper tree layer and have relatively enough space for the crown growth. The productive utilization of the crown space in the virgin forest confirmed the dominance of the beech as a structure bearer.