GROWTH OF YOUNG BEECHES (FAGUS-SYLVATICA L) IN AN EVEN-AGED, 18-YEAR OLD NATURAL BEECH REGENERATION

In an even-aged 18-year old natural beech regeneration, the growth of young plants has been analysed using only the main stem under 3 daylight intensities: full-light, half-light, and shade. The structure shows 3, 2 and 1 layers respectively under these light conditions (table I). The variations in total height and root collar diameter had 2 components in full-light and in half-light only, ie among- and within-layers (figs 1, 2 and 3). In full-light, the height variations were responsible for the differences among the layers and those of root collar diameter for the differences within the layers, fig 1. In half-light the variations in height and root collar diameter were simultaneously responsible for the differences among and within the layers (fig 2). The structure appeared early with a single or several layer(s) (fig 8). The annual and multiannual growth exhibited 3 periods: establishment, differentiation, and regression or stabilisation, (figs 5, 6, 8 and 9). In full-light where differentiation is best between the layers, stratification had an influence on the vigour of the seedlings and to some degree on their shape, but not in half-light (fig 10). The layers may be considered as reflecting social status in full-light where the height is regulated by stratification. The classification of seedlings according to their total height over the 18-year period will be analysed in a subsequent paper.