An influence of different thinning methods on qualitative wood production of European beech (Fagus sylvatica L.) on two eutrophic sites in the Western Carpathians

The issues related to appropriate management methods of beech stands have been considered as a crucial topic from the past up to now. Although the positive effect of tending on wood quality in beech stands is a generally known fact, the results from long-term experiments are very scarce. We investigated the qualitative production of beech forests, treated by different thinning methods during a long-term period of 53 years. For this purpose two long-term (lasting 53 years with a measurement interval of 5 years) series of research plots were used. On each plot three different thinning methods were applied: i) heavy thinning from below (C-grade according to the German forestry research institutes in 1902), ii) free crown thinning (original thinning method developed in Slovak Republic), and iii) control plot (without treatments). As much as 6,316 trees at the beginning of research and 864 trees at the last measurement were assessed and measured. Chi-squared test was used to quantify the effect of different thinning methods on qualitative wood production. The results showed the highest proportion of target trees, as well as the best average quality of the stem and crown on plots where the free crown thinning was applied followed by the plots with heavy thinning from below and control ones. We found that the proportion (expressed out of the total growing stock of crop trees) of veneers was the highest on plots managed by the free crown thinning (30 and 36%) and the lowest on control (unthinned) plots (10 and 19%). It is concluded that no significant differences between the two studied sites were found, which demonstrates a similar effect of the investigated thinning methods at different places across the region of Slovak Republic, but with similar site conditions. On the other hand, the most appropriate and hence successful thinning method was proved to be the free crown thinning, which is also recommended for management of beech forests from the aspect of silvicultural wood quality.