The quality potential and possibilities of using beech logs and sawn wood was investigated. Twenty-seven beech logs, with a mean diameter of 48 cm, were cut from 10 trees from a Hacquetio epipactidis-Fagetum site in SE Slovenia. The trees were pre-selected according to the national 5-level quality scale for forest stand evaluation, using two trees per class. Beech logs were classified according to the EN 1316-1 and sawn afterwards into unedged boards of 35 mm nominal thickness. Altogether, 250 boards were visually graded according to the rules of the European Organisation of the Sawmill Industry (EOS). Longitudinal vibration of logs and boards with the determination of stress wave velocity by MTG timber grader was additionally included into the quality assessment. In the case of logs, we confirmed significance of the relationship between visually assessed log quality and stress wave velocity. The stress wave velocity in logs was also related to the stress wave velocity in boards, where it varied considerably, especially for low-graded material. In the case of sawn wood, the relationship between sawn wood grade and stress wave velocity was insignificant. The research confirmed the possibility of presorting of logs, visually or non-destructively, for better classification and utilization of sawn timber.

IZVLEČEK V raziskavi smo preučevali fizikalne in mehanske lastnosti lesa v deblih navadnih bukev (Fagus sylvatica L.), izruvanih med žledolomom. Lastnosti smo preučevali na vzporednih preizkušancih sveže in osušene bukovine, ki smo jih sistematično vzorčili po radialni in vertikalni smeri dreves. Določili smo gostoto, togost, upogibno trdnost, strižno trdnost v smeri lesnih vlaken ter tlačno trdnost lesa v vseh anatomskih smereh. Togost smo primerjalno vrednotili med statično 4-točkovnim upogibom in nedestruktivno z merjenjem hitrosti ultrazvoka ter z določanjem frekvenčnega odziva. V drevesih, ki so izruvana obležala v gozdu od februarja do konca vegetacijske dobe 2014 in so imela delno ohranjen koreninski sistem, aktivno krošnjo in zadosten kapilarni tok, nismo zaznali sprememb gostote in mehanskih lastnosti, ki bi bile posledica razkroja lesa. Tako v svežem kot osušenem stanju smo ugotovili značilni vzorec porazdelitve gostote in trdnosti. Gostota lesa je po višini dreves naraščala, v radialni smeri od stržena proti periferiji debla pa smo zaznali rahel trend zmanjševanja. Mehanske lastnosti z izjemo prečne tlačne trdnosti se povečujejo tako po višini debla kot tudi od stržena proti kambiju in so bile vedno boljše pri osušenem kot pri svežem lesu. Zanesljivost nedestruktivnih metod za določanje togosti je večja pri ocenjevanju osušenega lesa. Za oceno upogibne trdnosti z nedestruktivnimi metodami še vedno priporočamo vzporedno vizualno opredelitev značilnosti lesa.

The wood from which xylite is formed in a long-term process undergoes numous changes while still retaining the character of a hygroscopic porous material. To plan the optimal drying schedule of xylite, the permeability coefficient, diffusion coefficient, and surface emission coefficient were determined. The porosity of xylite is low due to the demolished capillary structure; concurrently with the blocked pits, the permeability of xylite is very low, with a permeability coefficient not higher than 2.12 × 10⁻¹⁰ m²/Pa s. The capillary flow of free water is insignificant, allowing the diffusion transport of water to prevail. The diffusion coefficient is considerably influenced by the xylite's density. We confirm a significant increase in the bound water diffusion coefficient as the temperature increased (from 5.5 × 10⁻¹² m²/s at 20°C to 46.3 × 10⁻¹² m²/s at 40°C), and we predict that the activation energy will increase as the moisture content of xylite decreases (approx. 0.63 to 1.05%/% MC changes). As a consequence of the low surface resistance, the surface emission coefficient barely influences the moisture transport below the fiber saturation point.With an appropriate drying schedule, quality dried xylite can be used for various products as an equivalent substitute for dark-colored, high-density woods like ebony.