The analysis evaluates the potential and methods of the respective assessment of beech trees, beech logs and sawn timber. The objective of the study was to assess the impact of the quality of the incoming raw material (tree) on the quality and quantity of products – obtained at the sawmill. The study presents a model that indicates the relations between the assessment of the quality of a standing beech tree and the quality of the sawmill products obtained from its wood. In addition, relations between individual quality classes of sawlogs, pulpwood, energy wood and sawn timber are shown. Standing trees were assessed in three sites according to the national 5-grade quality scale, assortments produced from selected trees pursuant to the EN 1316-1 standard, and sawn timber produced from assortments according to the rules of the European Organisation of the Sawmill Industry (EOS). In total, 87.04 m3 of timber was harvested. In higher quality trees (quality 1 and 2), the shares of sawlogs were between 53% and 72% of gross tree volume, but in the poorest quality trees, the shares were only between 23% and 36%. What remained was pulp and energy wood. In trees of excellent quality (quality 1), sawlogs of the highest quality prevailed (A and B quality grade), while sawlogs of C and B quality prevailed in trees of lower quality. Covered knots and heart defects were typically the decisive criteria for classifying sawlogs quality in all three sites. A total of 30,786 m3 of unedged timber was sawn from the sawlogs, which comprised 35% of the total gross quantity of trees on average. Nine percent of the sawn timber was classified into the A–EOS class (top quality), 27% into the B–EOS class and 47% into the C–EOS class. Seventeen percent of the timber was only suitable for post-processing. The crucial criteria for classifying sawn timber were as follows: dead and rotten knots, heart, curvature and cracks. Above-average sawlogs (A and B quality grade) was mainly obtained from trees of better quality. Relations between the quality of trees, sawlogs and sawn timber indicated the suitability of classifying standing trees and sawlogs, since it was possible to produce sawn timber of higher quality from quality trees or logs. The model presents a rare attempt to establish and monitor quality and quantity from standing tree to end product.

This article investigates the quality of the machining surface of the five most common invasive tree species in Slovenia, i.e., black locust (Robinia pseudoacacia L.), boxelder maple (Acer negundo L.), horse chestnut (Aesculus hippocastanum), honey locust (Gleditsia triacanthos) and tree of heaven (Ailanthus altissima). The machining tests were made according to the American Society for Testing and Materials (ASTM) D1666-17 standard, where the quality of the surfaces after planing, routing and turning were evaluated with visual assessment, and the area and profile roughness parameters were also determined on selected specimens. The results showed that boxelder maple, horse chestnut and honey locust can be machined very well in all the studied operations, with the best results in routing and a little less good by turning, whereas the tree of heaven had the best quality in planing, and the worst by turning. Among all studied tree species, the black locust had the worst quality in planing, but the quality at routing was very similar to other tested species. The research also showed that there is little or no significant relationship between the qualities of the various types of machining for tested tree species.

Invasive tree species continue to spread, so in addition to strategies to limit this their use in the production of innovative products must be considered. This research aimed to develop and apply a model for calculating the cost price of invasive wood products considering the specificities of materials and production process, and is suitable for quickly assessing the economic feasibility of using the selected tree species for a given product. The TDABC method with the inclusion of fuzzy logic was used to incorporate the uncertainty of time and quality parameters. In the model, the imprecise values of these parameters are represented with triangular fuzzy numbers. Using a furniture product (dining table) made of black locust wood as an example, we demonstrated the applicability of the developed model. We found that the most probable cost price of a table made of black locust wood is comparable to the price of a product made of oak wood. In this way, we proved the potentially high economic value of invasive wood. The innovative products from invasive non-native wood species can achieve a high added value due to their visual characteristics and attractive appearance. Such use could increase interest in the (more efficient) management of invasive tree species, which would help to manage and use them efficiently. For further research, it would be useful to apply the proposed model to other invasive tree species as well as to other products.

This research was conducted to determine the impact bending strength and dynamic bending strength of Norway spruce wood from Slovenia. An accelerometer was added to the impact pendulum in order to capture the material’s response to an instantaneous load. Impact bending strength of specimens were determined by standard method measuring the height of pendulum before and after the break. While measuring the impact pendulum decelerations during the fracture of the specimen, the impact bending strength and dynamic bending strength was calculated. Correlations between the measured properties were determined, for which the R2 was in the range 0.88 to 0.51 between the standard and accelerometer method and between the impact bending strength and dynamic bending strength, respectively. The results confirmed that the methods used to determine the impact bending strength were comparable and that it was possible to determine dynamic bending strength on the basis of impact pendulum deceleration measurement.

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.

Green value chains are becoming increasingly important due to the current European and global strategic orientation. Wood and wood-related value chains are one of them. There are many challenges to overcome in the Slovenian forest-wood bioeconomy in order to strengthen it and make it more efficient. One of the biggest challenges is the increasing share of deciduous trees in Slovenian forests. This raises the question of how to build or strengthen forest-wood value chains with hardwood of different qualities as a basic raw material. The most important thing for the entire forest-wood bioeconomy is to have effective and functioning primary value chains in order to have a strong basis for multiplying the impact and value in the entire forest-wood value chain. The aim of this study was to analyze the primary value chains in the Slovenian forest-wood bioeconomy, with a focus on the processing of hardwood. The main research question was whether the primary value chains are equivalent for the efficient functioning of the forest wood chain, whose main raw material is hardwood. Based on an in-depth qualitative multi-criteria decision-making analysis, we can conclude that all analyzed primary value chains are very important for creating the conditions for the maximum utilization of the potential of hardwood raw materials of different quality. From the point of view of providing basic and advanced materials for further value chains in the wood sector (and related industries), these are mainly the chains P1 Sawlogs, P2 Veneer logs and P3 Wood for pulp and composites, and for other industries also the most advanced materials from the chain P4 Other industrial wood, which still require a lot of investment in research and development to reach the level of their wider (industrial) implementation. In terms of ensuring circular economy and sustainability, connecting chains C6 Residues and C7 Reclaimed wood are particularly important.