Acoustic and physico-mechanical properties of spruce timber: influence of differently intensive pruning

The work studies the physic.-mechanical properties of wood from the stands of Norway spruce (Picea abies (L.) Karst.), formed after pruning of various intensity. It was revealed that the high-intensity pruning in 23-year aged spruce stands (5-6 upper live branch clusters were left) led to a significant increase in the density of wood (by 15.6%) for trees with diameter larger than average in 3 years after. The removal of live and dry branches of lesser intensity does not affect the density of the wood. The wood formed as a result of 60 years of cultivation after pruning has quite high physical and mechanical properties: the compressive strength along the fibers is 51.6 +/- 1.02 MPa compared to reference value of 44.5 MPa; and the larger impact toughness (0.68 +/- 0.045 kgfm/cm(2)) than the reference value (0.40). It has been established that wood formed over 60-year cultivation after pruning has resonant properties: the average acoustic constant is 11.4 m(4)/kg. sec., while the optimal value of this indicator for the use of this wood in the music industry is more than 12 m(4)/kg. sec. It has been concluded that pruning combined with rational stand density makes it possible to produce wood with acoustic properties.