EN
Five plots with young beech trees of the same age (13–15 years) were established to study the
threshold, where plagiotropic growth becomes evident as the consequence of the reduced light intensity.
Trees were equally distributed along the light gradient and were divided according to light conditions (Indirect
Site Factor, ISF) into three groups of stand conditions: close canopy stand (ISF<20), edge (20<ISF<25)
and open area conditions, without the sheltering effect of a mature stand (ISF>25).
Morphological and physiological responses of young beech were studied between managed and old growth
forest and between different forest complexes (Pohorje and Kocevje region) on natural beech sites. Criteria
for the plagiotrophic growth was the relation between tree length and tree height (l/h) under various light
conditions.
Under controlled conditions (temperature, flow and CO2 concentration, RH, light intensity) light saturation
curves of leaf net photosynthesis were measured on same trees to compare both responses between different
light categories and different plots within comparable light conditions.
Our study confirmed different thresholds for morphologic response between two forest complexes as well as
between old growth and managed forest. Results were in accordance with physiological responses: the value
of limiting light for a plagiotropic response was lower in Kocevje (17% ISF) than on Pohorje (25% ISF).