EMPIRICAL USE OF THREE OAK SPECIES IN AFFORESTATION: LESSONS FROM SOWING AND TRANSPLANTING EXPERIMENTS

The effects of different factors on the growth in height and diameter of oak saplings in comparative cultures were estimated: progeny from autumn and spring sowing of acorns (1); growing conditions of pedunculate oak (Quercus robur L.) mother plants (2); the initial planting density of sessile oak (Q. petraea Liebl.) (3); natural lightening level of downy oak (Q. pubescens Willd.) mother plants (4). The pedunculate oak seedlings obtained after spring sowing were characterized by faster growth compared with those obtained from the autumn sowing. The lower growth rate observed in seedlings sown in autumn was due to the prolonged frosty weather during winter, which led to a decrease in acorn viability and progeny vigour. Due to the higher genetic diversity of the progeny obtained from the free-pollinated pedunculate oaks, it is possible that their growth was more intense and stable in comparison to those of saplings obtained from the acorns of isolated trees. The planting under the forest canopy had a clear influence on the growth in height of saplings. At low density levels (1.0 x 1.0 m), the sessile oak saplings benefited from larger availability of soil nutrients and displayed the highest growth, contrasting with those planted at high density (0.5 x 0.5 m). The deep and moderate shading caused a substantial reduction in the growth of downy oak saplings. Therefore, when planting, it is recommended to avoid using fast-growing species, which, due to asymmetric competition, could drastically reduce the growth in height of the downy oak saplings. Prolonged regeneration of the pruned root system following the transplantation process of sessile and downy oak seedlings determined their very slow growth in the first years of life.