Investigation of technological and growth characteristics of spruce roundwood with non destructive methods

Na desetih drevesih smreke z rastišča pod Karavankami smo vizualno ocenjevali kakovost lesa, ter jo primerjali s kakovostjo izdelanih 4 m dolgih sortimentov po višini posameznega drevesa. K vizualnemu ocenjevanju smo dodali še nedestruktivno določanje kakovosti. Na prsni višini stoječih dreves smo z napravo Arborsonic 3D® izdelali akustične tomografe, pri izdelani hlodovini pa smo z analizo frekvenčnega odziva določali vzdolžno hitrost zvoka. Na posameznih sortimentih po celotni višini dreves smo na osnovi radialnih izvrtkov dodatno izvedli še dendrokronološko analizo. Po višini dreves, od koreničnika do krošnje, se je kakovost izdelane hlodovine zmanjševala, večinoma zaradi števila in velikosti grč ter prisotnosti juvenilnega lesa. Tangencialna hitrost na obodu dreves, izmerjena z 2D akustičnim tomografom, je bila nižja pri drevesih z večjim prirastkom v adultnem obdobju. Povprečna vzdolžna hitrost zvoka je pri hlodovini kakovostnega razreda B in C znašala posamično 4196 m/s in 4155 m/s. Značilno nižjo hitrost zvoka 3714 m/s smo potrdili v najslabšem D-kakovostnem razredu. Ti sortimenti so večinoma izhajali iz 5. (16 – 20 m) in 6. vertikalne pozicije (> 20 m) v drevesih. Hlodovino tega kakovostnega razreda je mogoče na osnovi vzdolžne hitrosti zvoka zanesljivo razvrščati in ločiti od preostalih bolj kakovostnih sortimentov.We visually assessed the quality of ten spruce trees from a site below the Karavanke Mountains and compared it with the quality of 4-m-long logs made along the height of a single tree. The visual assessment was supplemented by a non-destructive method. For this purpose, acoustic tomographs were made at breast height of standing trees using the Arborsonic 3D® instrument, and longitudinal sound velocity was determined by longitudinal vibrations in the logs. We also performed an analysis of the radial growth of the wood on individual logs along the height of the trees. Depending on the height level in the trees, from the stump to the top, the quality of the logs produced decreased, mainly due to the number and size of branches, knots and the presence of juvenile wood. The tangential velocity at the circumference of trees measured with a 2D sonic tomograph was lower for trees with wider growth rings of adult wood. The average longitudinal sound velocity for logs in quality classes B and C was 4196 m/s and 4155 m/s, respectively. A much lower sound velocity of 3714 m/s was found in the poorest quality class D. These worst class logs mostly came from the 5th (16 - 20 m) and 6th vertical positions (> 20 m) in the trees. Logs of this quality class can be reliably sorted and separated from other assortments of higher quality based on longitudinal sound velocity