RESPONSE OF FAGUS SYLVATICA L. AND ABIES ALBA MILL. IN DIFFERENT GAP SIZE

Montane forests of silver fir and European beech in the Dinaric region represent the largest continuous forest area in Central Europe. The appropriately sized canopy gap is the main silvicultural tool for indirect promotion of silver fir. Within gaps four categories were established based on proportion of direct and diffuse radiation for comparison of beech and fir responses in managed and old growth forest. Quantum yield (Phi) in beech and silver fir was compared on all microsites during three consecutive periods (2009, 2010, and 2011) under controlled environmental conditions. Different response between species in same light categories was shown between different gap sizes. Quantum yield decreased with increasing gap size in all light categories the exception was beech growing under predominant direct light, in which yield significantly increased. Our conclusions emphasize the importance of gaps with low direct light levels, relatively small in size (0.03 - 0.11 ha) and the single tree selection silvicultural system to increase the competitive advantage of fir.