Crown development of beech crop trees under different thinning regimes

Crop trees are the main bearers of qualitative and value production of the stands. Although the number and production of the mentioned trees are affected by various factors, crown development by means of the thinning regime can be considered as very significant. The paper aims at the comparison of crop trees in homogeneous beech (Fagus sylvatica Linnaeus) stands, which were managed by three different management or thinning regimes for a long period (ca. 50 years): (i) heavy thinning from below (C grade according to the German forest research institutes released in 1902), (ii) Štefančík's free crown thinning, (iii) without interventions (control). Selection of crop trees was carried out at the beginning of research using the best stem quality, diameter and height dimension and regular spacing). In this paper only the last assessment of crop trees aged from 83 to 105 years including 23 subplots established across the Slovakian territory was analysed. The highest number of crop trees has been reached in forests where Štefančík's free crown thinning was applied. The proportion of these trees on subplots with the mentioned type of crown thinning was 61% out of the basal area at stand age of 100 years. A much lower proportion was found on subplots managed by thinning from below (32%) and on control ones (20%). Crown parameters (crown width, crown ratio, crown projection area, crown surface area and volume) showed the most appropriate values on subplots where Štefančík's free crown thinning was used. It was: 8.36 m (crown width), 0.50 (crown ratio), 56.84 m2 (crown projection area), 289.56 m2 (crown surface area), and 481.75 m3 (volume). Based on the results obtained after almost 50 years of systematic investigations, the mentioned thinning method was recommended for beech forests.