The Influence of Birch Upon the Branch Diameter and the Self-Pruning of Pine Trees in Mixed Stands

1989

35 S.

7 Tab., 3 Anh., 12 Lit. Ang.

Bandaufführung

33999

Calculations carried out by the author have demonstrated that it is profitable to leave birch stems on cleaning young pine plantations even if the quality of the pine timber should not be improved by the presence of the birch (Haegg 1988). Nevertheless, it would be of considerable value to the forest farmer to gain more knowledge about the effects of the birch upin the making of quality pine timber. If these effects are positive he can take advantage of naturally regenerated birch in pine plantations in order to produce high quality pine timber. The purpose of the present study is to elucidate the influence of the birch upon the branch diameter and the self- pruning of pine trees in mixed stands. From the analyses performed the following conclusions can be darwn - Self regenerated birch (seedlings) in pine plantations increases the number of stems per hectare (condenses the spacing) before cleaning, which reduces the branch diameter of the butt logs of the pine, resulting in a high quality centre-cut. Leaving birch stems when cleaning the young stand raises the number of stems per hectare, which gives additional effects on the branch diameter. Further, birch stems left on cleaning enhances the self-pruning, resulting in an improved-quality of the side-boards of the butt logs. The positive effect of the birch on the quality of the pine re-enforces the profitability of brich admixture in coniferous forests.