Effect of reducing silver birch competition on growth of sessile oak during the thicket stage

Naturally regenerated silver birch is one of the most abundant competitor for planted seedlings in central Poland. The effect of the interaction between planted oak seedlings and naturally regenerated birch was studied in 14−17−years−old sessile oak stand. The experiment was established at stand age of 14−years. At that time, there were around 4000 oaks and 10000 birches per hectare. A sample of dominant individuals of oak were selected and one of three treatments were applied to each individual. The treatments included: (i) removal of all naturally regenerated trees in a radius of 1 m (W1), (ii) removal of all naturally regenerated trees in a radius of 2 m (W2) and (iii) untreated control (K). Breast height diameter and height of selected oaks were measured during three years following the experiment establishment. The release of competition resulted in greater diameter and height growth. The diameter growth was increasing with an increment of free space from oak and was the greatest in the W2 treatment. The increment of height growth was similar regardless of the treatment radius. In practical forestry, silver birch can be recommended as admixture in pure oak stands with low survival rate as replacement for dead oaks. However, a minimum distance of 2 m between oak and birch should be kept