1 Les/Wood, Vol. 71, No. 2, December 2022 VSEBINA / CONTENTS Letnik 71, številka 2 / Volume 71, Number 2 • Uvodnik . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Editorial Katarina Čufar, Jože Kropivšek • Wood identification in objects of Bambuti people from the Congo in the collection of the Slovene ethnographic museum . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Identifikacija lesa predmetov ljudstva Bambuti iz Konga v zbirki slovenskega etnografskega muzeja Katarina Čufar, Hans Beeckman, Marko Frelih, Luka Krže, Wannes Hubau, Maks Merela • Air permeability of thermally modified hemlock wood . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25 Plinska permeabilnost termično modificiranega lesa zahodne čuge Yaohui Liu, Stavros Avramidis • Correlation between dry density and shrinkage in eight tropical hardwood species . . . . . . . . . . 31 Zveza med gostoto in krčenjem lesa osmih tropskih vrst Adedeji Robert Ojo, Samson Oluwaseun Ogutuga, Lawrence Olanipekun Aguda • Vpliv naravnega staranja na izbrane fizikalne in mehanske lastnosti konstrukcijskega lesa . . . . . 45 Effects of natural ageing on selected physical and mechanical properties of structural timber Matjaž Dremelj, Aleš Straže • Analiza življenjskega cikla in priložnosti za zmanjševanje vplivov lesne industrije na okolje . . . . 57 Life cycle assessment and opportunities to improve environmental impacts in the wood sector Katarina Remic, Matej Jošt Novice • Prof. dr. Primož Oven – prejemnik Zlate plakete Univerze v Ljubljani . . . . . . . . . . . . . . . . . . . . . . . 67 Prof. Dr. Primož Oven – recipient of the Golden Plaque of the University of Ljubljana Marko Petrič, Ida Poljanšek • Častni naziv Kongresni ambasador Slovenije za leto 2022 je prejel prof. dr. Miha Humar . . . . . . . 73 Honorary title of Congress Ambassador of Slovenia for 2022 awarded to Prof. Dr. Miha Humar Tina Drolc • Doc. dr. Davor Kržišnik prejemnik Svečane listine za mlade visokošolske učitelje in visokošolske sodelavce UL . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 75 Assistant Professor Dr. Davor Kržišnik recipient of the Ceremonial Certificate for Young Higher Education Teachers and Higher Education Associates of the University of Ljubljana Miha Humar • Priznanje Univerze v Ljubljani skupini strokovnih sodelavk in sodelavcev Biotehniške fakultete . 78 Katarina Čufar • 14. srečanje ALUMNI kluba Oddelka za lesarstvo . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 80 14th Meeting of the Alumni Club of the Department of Wood Science and Technology Katarina Čufar, Boštjan Lesar, Tomaž Kušar, Jure Žigon • Poročilo z drugega posveta projektne skupine projekta L4-2623: Ekstraktivi v jelovih grčah . . . . . 84 Viljem Vek, Ida Poljanšek, Primož Oven • Nova raziskovalna oprema na Oddelku za lesarstvo Biotehniške fakultete Univerze v Ljubljani - Instrument za določanje mikromehanskih lastnosti površin lesa, kompozitov in lesnoobdeloval- nih orodij MCT3 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 86 Marko Petrič 2 Les/Wood, Vol. 71, No. 2, December 2022 Les/Wood Založila/Published by Založba Univerze v Ljubljani / University of Ljubljana Press Za založbo/For the Publisher Gregor Majdič, rektor Univerze v Ljubljani / the Rector of the University of Ljubljana Izdala/Issued by Univerza v Ljubljani, Biotehniška fakulteta, Oddelek za lesarstvo / University of Ljubljana, Biotehnical Faculty, Department of Wood Science and Technology Za izdajatelja/For the Issuer Marina Pintar, dekanja Biotehniške fakultete UL / the Dean of the Biotehnical Faculty UL Naslov uredništva/Editorial Office Address Univerza v Ljubljani, Biotehniška fakulteta, Revija Les/Wood, Jamnikarjeva ulica 101, 1000 Ljubljana, Slovenia Glavna urednica/Editor-in-chief Katarina Čufar, Slovenija / Slovenia, katarina.cufar@bf.uni-lj.si Odgovorni urednik/Managing editor Jože Kropivšek, Slovenija / Slovenia, joze.kropivsek@bf.uni-lj.si Tehnična urednika/Technical editors Anton Zupančič, Slovenija / Slovenia, anton.zupancic@bf.uni-lj.si Teja Bizjak Govedič, Slovenija / Slovenia, teja.bizjakgovedic@bf.uni-lj.si Uredniški odbor/Editorial board Christian Brischke, Nemčija / Germany Alan Crivellaro, Velika Britanija / United Kingdom Dominika Gornik Bučar, Slovenija / Slovenia Miha Humar, Slovenija / Slovenia Denis Jelačić, Hrvaška / Croatia Leon Oblak, Slovenija / Slovenia Primož Oven, Slovenija / Slovenia Krishna K. Pandey, Indija / India Manuela Romagnoli, Italija / Italy Kevin T. Smith, ZDA / USA Milan Šernek, Slovenija / Slovenia Rupert Wimmer, Avstrija / Austria Jezikovni pregled/Proofreading Darja Vranjek (slovensko besedilo/Slovene text) Paul Steed (angleško besedilo/English text) Prelom/Layout Tiskarna Koštomaj, Celje Tisk/Print Tiskarna Koštomaj, Celje Natisnjeno v decembru 2022 v 100 izvodih./Printed in December 2022 in 100 copies. ISSN 0024-1067 (tiskana verzija/printed version) ISSN 2590-9932 (spletna verzija/on-line version) https://journals.uni-lj.si/les-wood Periodičnost/Frequency Dve številki letno/Two issues per year Les/Wood je referiran v mednarodnih bibliografskih zbirkah Les/Wood is indexed in the international bibliographic databases AGRIS, CAB Abstracts, Directory of Open Access Journals Les/Wood je revija z odprtim dostopom, ki izhaja pod pogoji licence Creative Commons CC BY-NC 4.0. Les/Wood is an Open Access journal published under the terms of the Creative Commons CC BY-NC 4.0 License. Izdajanje revije sofinancira Javna agencija za raziskovalno dejavnost Republike Slovenije (ARRS) The journal is co-financed by Slovenian Research Agency (ARRS) 3 Les/Wood, Vol. 71, No. 2, December 2022 UVODNIK / EDITORIAL Katarina Čufar, Jože Kropivšek Urednika / Editors Revija Les/Wood med tradicijo in novimi izzivi V letu 2022 je delo pri reviji Les/Wood zazna- movalo delovanje v okviru Založbe Univerze v Lju- bljani, o čemer smo že poročali. Tako je revija dos- topna na novi spletni strani, https://journals.uni-lj. si/les-wood. Novost za avtorice in avtorje ter vse, ki soustvarjajo revijo, je prenovljeni portal za oddajo, recenzijo in spremljanje prispevkov do končne ob- jave. Na isti strani so dostopne tudi vse številke od leta 2017, v pripravi pa je tudi arhiv starejših letni- kov revije. Uredniškemu odboru se je kot tehnična uredni- ca pridružila Teja Bizjak Govedič, ki je že v tej številki revije uredila večino prispevkov. Tako se je znatno skrajšal čas od sprejetja do objave prispevkov. Nove tehnične urednice smo zelo veseli in ji želimo us- pešno delo v naši uredniški ekipi. Revija ostaja zvesta dolgoletni tradiciji, a se na drugi strani hitro odziva na nove smernice znan- stvene periodike. Tu bi vas radi opozorili na nekaj prednosti revije, najprej odprti dostop, ki postaja vse bolj pomembna zahteva financerjev raziskoval- ne dejavnosti. Odprti dostop revije odgovarja na priporočilo (oz. določilo, ki na primer velja za pro- jekte Obzorje Evropa) za takojšnjo odprto dosto- pnost recenziranih člankov in daljših besedil z licen- cami Creative Commons (CC BY ali CC0). Priporoča se, da morajo biti dostopni tudi preko repozitorijev. Zato so članki, objavljeni v Les/Wood, dostopni tudi preko repozitorija Univerze v Ljubljani RUL. Revija že dlje časa ob objavi člankov omogoča tudi obja- vo raziskovalnih podatkov, večinoma v repozitoriju RUL, kar je tudi v skladu s priporočilom odprte zna- nosti. V povezavi z zahtevami odprtega dostopa smo začeli članke sistematično opremljati tudi z odprtim identifikatorjem za raziskovalce in sodelavce ORCID (Open Researcher and Contributor ID), ki ga pripe- njamo imenom avtoric in avtorjev. ORCID je enolični in trajni identifikator, s katerim upravlja nepridobi- tna organizacija ORCID Inc., prek njega pa je mo- goče spremljati objave posameznih avtorjev. OR- CID je trenutno med najbolj razširjenimi tovrstnimi identifikatorji v globalni akademski skupnosti. Vse to pomaga, da objave v reviji Les/Wood samodej- no prepoznajo tudi baze kot so Google učenjak in Research Gate, ki dodatno omogočajo razširjanje, promocijo in posredno večjo citiranost člankov. Revija ostaja pomembna za učenje strokovne- ga izrazoslovja. Les/Wood je skupaj z drugimi revi- jami, ki objavljajo slovenska in angleška besedila, pomemben vir za razvoj in izpopolnjevanje orodij za strojno prevajanje iz slovenščine v angleščino in obratno ob podpori umetne inteligence. Revija še naprej ostaja prepoznavna tudi za ob- javo del mladih avtoric in avtorjev na začetku karie- re, ki so skupaj z mentorji napisali kar štiri od petih člankov te številke. Zahvaljujemo se vsem, ki soustvarjate revijo, še posebej recenzentom in recenzentkam, katerih anonimno delo je neprecenljivo za njeno delovanje. Glede na izzive med tradicijo in novostmi bo glavna skrb revije Les/Wood tudi v prihodnosti usmerjena v pridobivanje kritičnega števila kakovostnih pri- spevkov ter skrb za razširjanje objavljenega znanja, ki se izraža v prosti dostopnosti, branosti, citiranosti ter napredku znanosti in stroke. 4 Les/Wood, Vol. 71, No. 2, December 2022 Les/Wood between tradition and future challenges In 2022, Les/Wood’s work has evolved with the help of the University of Ljubljana Press. The journal is now available on a new website, https:// journals.uni-lj.si/les-wood. It has a new portal for submission, review, and follow-up of submissions to final publication. All issues from 2017 are also available on the same site, and an archive of older issues of the journal is in the works. Teja Bizjak Govedič, who has edited most of the articles in this journal, has joined the Editorial Board as the new Technical Editor. This has signifi- cantly shortened the time from acceptance to pub- lication. We are very pleased to welcome the new technical editor and wish her successful co-opera- tion with our editorial team. The journal remains faithful to its long-stand- ing tradition, but on the other hand responds quickly to new trends in scientific journals. At this point, we would like to mention some of the jour- nal’s strengths. The first is open access, which is becoming an increasingly important requirement of research funders. The open access nature of Les/Wood is in line with the recommendation that peer-reviewed articles and longer texts be made immediately freely available with Creative Commons licences (CC BY or CC0) and accessible through repositories. For this reason, articles pub- lished in Les/Wood are also accessible through the University of Ljubljana’s RUL repository. In addition to publishing articles, the journal has also made re- search data available, mostly in the RUL repository, which is also in line with the open science recom- mendation. Furthermore, we have started to systematically assign an Open Researcher and Contributor ID (OR- CID) to the names of authors of articles. ORCID is a unique and persistent identifier managed by the non-profit organisation ORCID Inc. through which individual authors’ publications can be tracked. All of this helps ensure that publications in Les/ Wood are automatically recognised by databases such as Google Scholar and Research Gate, further facilitating dissemination and promotion and indi- rectly increasing the citation of articles. The journal remains important for learning technical terminology. Together with other jour- nals that publish both Slovenian and English texts, Les/Wood is an important resource for the devel- opment and refinement of AI-assisted machine translation tools from Slovenian into English and vice versa. The journal continues to be recognised for publishing the work of young authors at the begin- ning of their careers, who co-authored four of the five articles in this issue. Finally, we would like to thank all those who help shape the journal, especially the reviewers, whose anonymous work is invaluable to the jour- nal. Given the challenges between tradition and novelty, Les/Wood’s primary concern will continue to be attracting a critical mass of high-quality man- uscripts and disseminating published knowledge that leads to open access, readership, citations, and advances in science and the profession. 25 Les/Wood, Vol. 71, No. 2, December 2022 Vol. 71, No. 2, 25-30 DOI: https://doi.org/10.26614/les-wood.2022.v71n02a01 1 Department of Wood Science, Faculty of Forestry, University of British Columbia, Vancouver, BC, Canada * e-mail: lyaohui@student.ubc.ca AIR PERMEABILITY OF THERMALLY MODIFIED HEMLOCK WOOD PLINSKA PERMEABILNOST TERMIČNO MODIFICIRANEGA LESA ZAHODNE ČUGE Yaohui Liu 1* , Stavros Avramidis 1 UDK 630*812.23 Received / Prispelo: 29.7.2022 Original scientific article / Izvirni znanstveni članek Accepted / Sprejeto: 11.8.2022 . Abstract / Izvleč ek Abstract: Western hemlock (Tsuga heterophylla) is a prevalent coastal species in British Columbia (BC). Its wood has a high potential for thermal modification, a process that can affect numerous physical properties, including air permeability. The current study investigates the longitudinal air permeability of hemlock wood modified at three temperature levels, 170 °C, 212 °C, and 230 °C, and a two-hour treatment length. Permeability values obtained using Darcy’s law and the water-falling volume displacement method were positively correlated with treatment temperature up to 212 °C, after which the permeability decreased slightly. ANOVA followed by the Duncan test revealed that thermal treatment at 212 °C and 230 °C significantly increased air permeability, whereas it was insignificant at 170 °C. Keywords: wood, thermal modification, western hemlock, longitudinal air permeability, specific permeability, temperature effect Izvleček: Zahodna čuga (Tsuga heterophylla) je prevladujoča obalna vrsta v Britanski Kolumbiji (BC) z velikim potencialom za termično modifikacijo lesa, ki lahko vpliva na številne fizikalne lastnosti, vključno s plinsko permeabilnostjo. Ta študija preučuje vzdolžno plinsko permeabilnost lesa čuge, termično modificiranega pri treh temperaturah, 170 °C, 212 °C in 230 °C, ter 2-urni obdelavi. Vrednosti plinske permeabilnosti, določene iz Darcyjevega zakona z metodo izpodrivanja prostornine vode, so bile pozitivno povezane s temperaturo obdelave do 212 °C, nato pa se je permeabilnost nekoliko zmanjšala. Analiza variance (ANOVA) skupaj z Duncanovim testom mnogoterih primerjav sta pokazala, da je termična obdelava pri 212 °C in 230 °C znatno povečala plinsko permeabilnost, medtem ko so bile spremembe pri 170 °C neznačilne. Ključne besede: termična modifikacija, zahodna čuga = Tsuga heterophylla, vzdolžna plinska permeabilnost, specifična permeabilnost, vpliv temperature 1 INTRODUCTION 1 UVOD The increasing demand for sustainable con- struction materials calls for improved wood perfor- mance, including UV-stability, fire resistance, and anti-fungal properties, because future bio-econo- mies rely on renewable biomaterials to design and manufacture new products. Wood as a raw material has a wide variety of applications, such as furniture, construction, many objects, and toolmaking. How- ever, wood has several shortcomings that restrict its application. For example, it can easily absorb water (moisture), resulting in dimensional instabili- ty, checking, and biodegradation by wood-destroy- ing organisms such as fungi and insects (Bahmani et al., 2016; Bahmani & Schmidt, 2018). Researchers have developed different chemical methods such as acetylation (Hill et al., 1999) and salinization (Do- nath et al., 2006) to reduce wood’s hydrophobicity and hygroscopicity, and thus improve dimensional stability. Thermal modification is a non-chemical method of decreasing hygroscopicity with an in- creasing market acceptance that improves specific properties and results in a material that does not pose an environmental hazard compared to chem- ically treated wood. Thermally modified wood 26 Les/Wood, Vol. 71, No. 2, December 2022 Liu, Y ., & Avramidis, S.: Plinska permeabilnost termično modificiranega lesa zahodne čuge has various applications in furniture construction, flooring, sauna/bathroom furnishings, doors, and cladding (Hill, 2006). Permeability is a critical wood property be- cause it directly affects drying (Perre, 2007; Rahi- mi et al., 2019; Rahimi et al., 2022) and impregna- tion with fluids (Mansouryar et al., 2010; Chu et al., 2019a; Chu et al., 2019b; Dong et al., 2020). It is worth evaluating the permeability of thermally modified wood because different levels of perme- ability are desired based on the application of the modified wood. For example, cladding requires low permeability, whereas post-treatment with fluid fire retardants requires high permeability. Yuan (1994) reported increased air permea- bility in eucalyptus that was heat-treated at 140 °C for 5 hours. A study by Kang et al. (2018) revealed that air permeability increased after the heat treat- ment of malas (Homalium foetidum) at 190 °C for 3 hours. Taghiyari and Malek (2014) reported that heat treatment affected air permeability. At tem- peratures below 60 °C, permeability increased due to bound water reduction and shrinkage. Hermawan et al. (2020) investigated the effects of drying temperatures on preservative retention and penetration of some Malaysian fast-growing species timbers. The results demonstrated that high-temperature drying has a positive impact on preservative penetration. However, other studies revealed no effect of temperature on permeability. Rhatigan et al. (2003) reported no differences in air permeability between lumber dried at convention- al and high temperatures. Other studies revealed that heat treatment did not change the permeabil- ity of Populus robusta (Rousset et al., 2004) or sub- alpine fir (Abies lasiocarpa) (Poonia et al., 2015). Although thermal modification is a well-devel- oped industrial process in Europe, it is still in its in- fancy in Canada. Therefore, establishing that such a method adds value to local wood species may lead to the development of new products and markets. Western hemlock (Tsuga heterophylla) forms ex- tensive forests along the coastal mountains of the North American Pacific Northwest, and its wood is light in colour and typically resin-free, but the heartwood routinely contains wet pockets and ex- tractives (Ward & Pong, 1980). Its attributes, such as high-quality machinability, smooth sanding, easy gluing, and high nail and screw holding, make it suitable for plywood, roof decking, and general construction (Alden, 1995). This work hypothesizes that thermal treat- ment significantly increases permeability in west- ern hemlock, and the treatment temperatures are positively correlated with permeability (Nourian & Avramidis, 2021). As such, the objective here is to evaluate the effects of thermal modification under three temperatures on hemlock air permeability. 2 MATERIALS AND METHODS 2 MATERIALI IN METODE Two hundred permeability samples of 70 mm × 13 mm × 13 mm in the longitudinal, radial, and tangential directions were cut from second-growth western hemlock lumber that was commercially thermally modified in a past study (Nourian & Avr- amidis, 2021). Thermal modification was carried out at 170 °C, 212 °C, and 230 °C, with a holding time of 2 hours in a Jartek industrial heat treatment chamber at Scottywood Corporation in Squamish, BC, Canada. The superficial air permeability (kg, m 3 (gas)/m Pa s) of the specimens was measured by the fall- ing-water volume displacement method using an apparatus similar to that described by Siau (1995). The specific permeability (K, m 3 /m) was thereafter calculated by multiplying kg by the air viscosity of 1.81·10 -5 Pa s. Analysis of variance (ANOVA) followed by the Duncan test to determine the significance of the differences between the air permeability of sam- ples in four different groups was performed with the K dataset. 3 RESULTS AND DISCUSSION 3 REZULTATI IN DISKUSIJA Table 1 lists the K-values for the four sample groups. The average ± standard deviation in the controls was 0.72 × 10 -11 ± 0.59 × 10 -11 and 1.00 × 10 -11 ± 1.01 × 10 -11 for 170 °C. The average specific permeability values for the samples treated at 212 °C to 230 °C were 1.26 × 10 -11 ± 1.01 × 10 -11 and 1.21 × 10 -11 ± 0.78 × 10 -11 , respectively. After heat treat- ment at 212 °C, the permeability was 1.75 times greater than the controls. This finding accords with Lin and Kozlik (1971) and Rhatigan et al. (2003) for 27 Les/Wood, Vol. 71, No. 2, December 2022 Liu, Y ., & Avramidis, S.: Air permeability of thermally modified hemlock wood eastern hemlock, where permeability increased with increasing temperature. Measures of dispersion (standard deviation, coefficient of variation, and range) indicated a high variation of air permeability within each treatment group. The high variation in the permeability in each group is possibly related to anatomical differenc- es, namely differences in the sapwood and heart- wood content in specimens. Table 2 summarizes the ANOVA results of the different temperatures on the permeability of hemlock wood. The effect of different temperatures on the permeability of the samples was statistically significant (P ≤ 0.05). According to Duncan’s test, thermal treatment at 170 °C increased air permeability insignificantly compared to the controls, while thermal treatment at 212 °C and 230 °C significantly increased air per- meability. In addition, the air permeability in modi- fied wood showed insignificant changes among the three thermally treated groups. Figure 1 shows a direct relation between per- meability and treatment levels until 212 °C. Ac- cording to several studies, treatment temperature and air permeability are positively correlated (Her- mawan et al., 2020; Kang et al., 2018; Yuan, 1994). The one-way ANOVA tests revealed an insignificant difference in permeability values between samples treated at 212 °C to 230 °C, although specific per- meability for T–212 °C was slightly higher. Table 1. Central tendency and dispersion for the specific permeability. Preglednica 1. Osrednja tendenca in razpršenost za specifično permeabilnost. Statistical parameter Specific permeability at different thermal treatment levels Control 170 °C 212 °C 230 °C Measures of central tendency Mean (m 3 ·m -1 ·) 0.72 × 10 -11 1.00 × 10 -11 1.26 × 10 -11 1.21 × 10 -11 Median (m 3 ·m -1 ·) 0.58 × 10 -11 0.70 × 10 -11 0.93 × 10 -11 1.13 × 10 -11 Measures of dispersion Standard deviation (m 3 ·m -1 ) 0.59 × 10 -11 1.01 × 10 -11 1.01 × 10 -11 0.78 × 10 -11 Coefficient of variation (%) 81.85 101.31 80.09 64.62 Range (m 3 ·m -1 ) 2.86 × 10 -11 5.21 × 10 -11 4.80 × 10 -11 3.82 × 10 -11 Table 2. Analysis of variance results for the specific permeability. Preglednica 2. Rezultati analize variance za specifič- no permeabilnost. Sum of Squares df Mean Square F Sig. Between groups 0.000 3 0.000 3.985 0.009 * Within groups 0.000 196 0.000 Total 0.000 199 * Significant at 95% Figure 1. Mean and standard deviation for specif- ic permeability in untreated and thermally treated western hemlock. The histograms show the mean, and the whiskers represent the standard deviation. Different letters above the whiskers (a or b or ab) indicate statistically significant differences between groups in the Duncan test. Slika 1. Povprečje in standardni odklon specifične permeabilnosti za neobdelan in termično obdelan les zahodne čuge. Histogrami prikazujejo povpre- čje, ročaji pa standardni odklon. Različne črke (a, b ali ab) označujejo statistično značilne razlike med skupinami po Duncanovem testu. 28 Les/Wood, Vol. 71, No. 2, December 2022 Liu, Y ., & Avramidis, S.: Plinska permeabilnost termično modificiranega lesa zahodne čuge Bordered pits affect wood permeability con- siderably, and thermal treatment can change or restructure these. In addition, extractives may ob- struct the pit membranes, which hinders fluid flow through the wood elements (components). The process of thermal modification also alters the ex- tractives and redistributes them such that they may be deposited on the cell walls and pits (Esteves & Pereira, 2009). Overall, the findings of this study indicate that permeability reaches its maximum at 212 °C. Further research is required to reveal the possible effects of temperature on wood permea- bility above 230 °C. 4 CONCLUSION 4 ZAKLJUČKI This project investigated the influence of three different temperatures, namely 170 °C, 212 °C, and 230 °C, on the specific permeability of west- ern hemlock wood. The findings revealed that by increasing the temperature the permeability of the hemlock wood samples increased, where there was a significant difference between the samples heated above 170 °C and the control ones. More- over, the permeability of the samples heat-treated at 212 °C was 1.75 times greater than that of the control samples. Overall, the findings of this study suggest that thermal modification is potentially an effective method for increasing the permeability of hemlock wood. It is worth mentioning that perme- ability is strongly affected by anatomical proper- ties, and thus future research should focus on the effects of thermal treatment on different regions of hemlock wood, such as juvenile wood vs. mature wood and sapwood vs. heartwood. 5 SUMMARY 5 POVZETEK Les je znan kot vsestranska surovina, ki se lah- ko uporablja na različne načine. Vendar pa je upora- ba lesa v nekaterih primerih lahko omejena zaradi njegovih specifičnih lastnosti, vključno s higrosko- pnostjo in dovzetnostjo za razkroj (Bahmani et al., 2016; Bahmani & Schmidt, 2018). Natančneje, obstajajo nekateri primeri uporabe lesa, pri kate- rih ima permeabilnost, ki se nanaša na enostav- nost prehajanja tekočine skozi porozne materiale pod gradientom tlaka, ključno vlogo (Rahimi et al., 2011). Zato je pomembno oceniti permeabilnost, saj lahko to pomaga pri izdelavi boljših izdelkov za določene uporabe. V tej študiji je bila ocenjena plinska permeabilnost lesa zahodne čuge (Tsuga heterophylla, angleško hemlock) pri treh različnih temperaturah termične modifikacije. Za to študijo je bilo zbranih 200 vzorcev lesa zahodne čuge, ki so bili razrezani na določene di- menzije. Vzorci so bili termično modificirani z indu- strijsko pripravo za termično modifikacijo Jartek. Glede na temperaturo, pri kateri so bili vzorci ter- mično modificirani, so bile oblikovane štiri skupine: 170 °C, 212 °C, 230 °C in kontrolna skupina. Za dolo- čitev plinske permeabilnosti na podlagi poroznosti mikrostrukture lesa je bila uporabljena naprava na osnovi metode izpodrivanja prostornine vode, kot jo je opisal Siau (1995). Plinska permeabilnost vzorcev v štirih različnih skupinah je bila analizirana z ANOVA, ki ji je sledil Duncanov test za določitev značilnosti razlik. Rezultati te študije so pokazali, da je plinska permeabilnost pozitivno povezana s temperaturo, saj se je permeabilnost vzorcev lesa zahodne čuge, segretih nad 170 °C, bistveno razlikovala od kon- trolne. Na podlagi podrobnejšega opazovanja so vzorci, termično modificirani pri 212 °C, pokazali 1,75-kratno povečanje prepustnosti v primerjavi z nemodificiranimi. REFERENCES VIRI Alden, H. (1995). Softwoods of North America, FPL-GTR-102. Madi- son, WI. U.S. Dept. of Agriculture, Forest Service, Forest Produ- cts Laboratory, 151pp. Bahmani, M., & Schmidt, O. (2018). Plant essential oils for envi- ronment-friendly protection of wood objects against fun- gi. Maderas. Ciencia y tecnología, 20(3), 325-332. Bahmani, M., Schmidt, O., Fathi, L., & Frühwald, A. (2016). Envi- ronment-friendly short-term protection of palm wood against mould and rot fungi. Wood Material Science & Engineering, 11(4), 239-247. Chu, D., Mu, J., Avramidis, S., Rahimi, S., Liu, S., & Lai, Z. (2019a). 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Taghiyari, H. R., & Malek, B. M. (2014). Effect of heat treatment on longitudinal air and liquid permeability of circular and square- shaped native hardwood specimens. Heat and Mass Transfer, 50(8), 1125-36. Ward, J. C., & Pong, W. Y . (1980). Wetwood in trees: a lumber reso- urce problem. USDA Forest Service General Technical Report PNW 112, Pacific North West Forest Range Station, Portland, Oregon, 56pp. Yuan, L. (1994). Heat treatment of Eucalyptus wood and its perme- ability improvement. China Wood Industry, 1994; 8(3), 30-3. (In Chinese). 31 Les/Wood, Vol. 71, No. 2, December 2022 Vol. 71, No. 2, 31-44 DOI: https://doi.org/10.26614/les-wood.2022.v71n02a02 1 Department of Forest Products Development and Utilization. Forestry Research Institute of Nigeria. P .M.B 5054, Jericho, Ibadan, Nigeria * e-mail: ojo.ar@frin.gov.ng CORRELATION BETWEEN DRY DENSITY AND SHRINKAGE IN EIGHT TROPICAL HARDWOOD SPECIES ZVEZA MED GOSTOTO IN KRČENJEM LESA OSMIH TROPSKIH VRST Adedeji Robert Ojo 1* , Samson Oluwaseun Ogutuga 1 , Lawrence Olanipekun Aguda 1 UDK 630*812:176.1 Received / Prispelo: 16.7.2022 Original scientific article / Izvirni znanstveni članek Accepted / Sprejeto: 29.9.2022 . Abstract / Izvleč ek Abstract: Eight tropical hardwood species were assessed for their density and radial, tangential and volumetric shrinkage, after which the relation between the density and different shrinkages was checked through correlation and regression. The results showed that the highest mean density was observed in Milicia excelsa with 900.63±50.13 kg/m³, followed by Afzelia africana, Nesogordonia kabingaensis and Nauclea diderichii with 831.25±41.67 kg/m³, 808.75±20.88 kg/m³ and 801.88±46.40 kg/m³, respectively. The mean density for Cassia simea was 781.88±27.71 kg/m³, Mansonia altissima 593.13±65.98 kg/m³, and Sterculia tragacantha 481.25±111.73 kg/m³, while the least density was observed in Treculia africana with 463.75±67.88 kg/m³. The highest volumetric shrinkage was observed in Nesogordonia kabingaensis with 14.71±2.28%, and the least in Cassia simea with 5.11±2.65%. It is concluded that there exists positive but weak correlation between density and the shrinkages in the eight tropical hardwood species. Keywords: wood, topical hardwoods, density, shrinkage Izvleček: V raziskavi ocenjujemo zvezo med gostoto in krčenjem za osem tropskih lesnih vrst. Raziskali smo gostoto ter radialno, tangencialno in prostorninsko krčenje osmih tropskih lesnih vrst. Rezultati so pokazali, da je imela največjo povprečno gostoto vrsta Milicia excelsa z 900,63±50,13 kg/m³, sledijo Afzelia africana, Nesogordonia kabingaensis in Nauclea diderichii z 831,25±41,67 kg/m³, 808,75±20,88 kg/m³ in 801,88±46,40 kg /m³. Povprečna gostota za vrste Cassia simea je bila 781,88±27,71 kg/m³, Mansonia altissima 593,13±65,98 kg/m³, Sterculia tragacantha 481,25±111,73 kg/m³, medtem ko je bila najmanjša gostota opažena pri vrsti Treculia africana s 463,75±67,88 kg/m³. Največje prostorninsko krčenje je bilo zaznano pri vrsti Nesogordonia kabingaensis (14,71 ± 2,28 %), najmanjše pa pri vrsti Cassia simea (5,11 ± 2,65 %). Ugotavljamo, da obstaja šibka pozitivna korelacija med gostoto in krčenjem pri osmih tropskih vrstah listavcev. Ključne besede: les, tropski listavci, gostota, krčenje 1 INTRODUCTION 1 UVOD Water is a natural constituent of a living tree, and it commonly makes up over half the total weight; that is, the weight of water in green wood is commonly equal to or greater than the weight of the dry wood substance (Haygreen & Bower, 1996). It is well known that wood is an anisotropic material which presents differential dimensional changes in the different structural directions. The magnitude of shrinkage and swelling is affected by the amount of moisture gained or lost by wood when the moisture content fluctuates between zero and the fibre saturation point (Usta & Guray, 2000). Shrinking and swelling occur as the wood changes moisture content in response to daily as well as seasonal changes in the relative humidity of the atmosphere. That is, when the air is humid wood adsorbs moisture and swells, while when the 32 Les/Wood, Vol. 71, No. 2, December 2022 Ojo, A. R., Ogutuga, S. O., & Aguda, L. O.: Zveza med gostoto in krčenjem lesa osmih tropskih vrst air is dry, wood loses moisture and shrinks. Various finishes and treatments may be used to slow this process, but, in general, they do not stop it (Eckel- man, 2012). Likewise, air and kiln drying do not pre- vent the wood from subsequently gaining or losing moisture. Thus, wood that is kiln dried to 6% mois- ture content and stored in a dry shed outdoors in a temperate climate, such as that found in Indiana, USA, will regain moisture until it eventually reaches about 12% moisture content. Under the same con- ditions in a tropical climate, the wood will come to a moisture content of about 16%. The resulting di- mensional changes in the wood are a major source of defects in furniture and other wood structures (Ojo et al., 2016). The changes in wood dimensions as a result of its shrinkage as it dries and swelling during moisture absorption are of great importance to anyone who uses wood, because wood readily takes on or gives off moisture, even from the atmosphere. When wood loses moisture below fibre saturation point (FSP), it shrinks and swells when water is absorbed. The percentage change in wood dimensions as a re- sult of moisture loss is termed shrinkage (Dinwood- ie, 1989). The observed changes in wood dimen- sions as a result of shrinkage are unequal along the three structural directions. This behaviour of wood has been documented widely by various authors (Panshin & de Zeeuw, 1980; Lausberg et al., 1995; Ogunsanwo, 2000; Ojo et al., 2016). However, Panshin and de Zeeuw (1980), not- ed that the geometric disposition of cells along the principal directions is mainly responsible for this observation. The moisture content is the water contained in wood and it is a natural constituent of all parts of a living tree and makes up about half of the total weight (Hossain et al., 1991). Desch and Dinwood- ie (1983), reported that timber of living trees and freshly felled logs contains a large amount of water which has a profound influence on the properties of wood, such as weight and strength. Wood is also liable to attack by some insects and fungi when the moisture content is high. Density is the amount of wood substance per unit volume. Panshin and de Zeeuw (1980), Din- woodie (1981), and Desch (1988), explained that the density of wood is a function of the cell wall thickness and also depends on the level of cell wall development. In research activities, densities are frequently reported on an oven-dry weight and volume ba- sis. At any other condition the moisture content has a marked effect on density (Kellog, 1981). As the moisture content increases from the oven-dry condition up to fibre saturation point, the weight increases and as a result of swelling so does the volume (Kellog, 1981). Meanwhile, high density is associated with thick fibre walls and a higher pro- portion of fibres. These are the qualities which contribute to water absorption and resultant di- mensional changes (Shrivastava, 1997). It is there- fore necessary to ascertain that in the absence of any other data about the dimensional stability of a particular species, wood density is used as a guide to its utilization by establishing the relationship between the density and dimensional stability of some tropical hard wood species so as to serve as guide for their general technical application. The eight tropical timbers assessed in this study are as follows: Nauclea diderrichii (African peach; opepe) is an evergreen tree that reaches a height of about 30-40 m and a diameter of 0.9-1.5 m; bole cylindrical, slender, straight and branchless, rising to 20-30 m and a broad spherical crown with thick foliage (Orwa, 2009). It is a commercial timber of West Africa. The wood is yellow and darkens slightly when exposed to light. It is semi-heavy and of medium hardness. Because of its good mechanical properties and natural durability, which can be enhanced by pre- servative treatment, it is sought after as a timber for outdoor uses (harbour works, railway sleepers), buildings (carpentry, floors, facings, indoor and outdoor woodwork) and for cabinet making. The wood is also suitable for fence posts and bridges as it is moderately termite-resistant and resistant to fungi and marine borers (Orwa, 2009). The wood is strong and moderately hard to hard. At 12% moisture content the modulus of rupture is 85–166 N/mm², modulus of elasticity 10,490–14,660 N/mm², compression parallel to grain 52–78 N/mm², shear 8.5–17 N/mm², cleavage (7–)12–24 N/mm, Janka side hardness 5790–7260 N, Janka end hardness 7140–9160 N and Cha- lais-Meudon side hardness 3.0–8.6. (Protabase, 2010). 33 Les/Wood, Vol. 71, No. 2, December 2022 Ojo, A. R., Ogutuga, S. O., & Aguda, L. O.: Correlation between dry density and shrinkage in eight tropical hardwood species Milicia excelsa (African teak; iroko) is large de- ciduous tree, growing up to 50 m high and 350 cm in trunk diameter. The trunk is often buttressed and can be branchless for up to 20 m (Barwick, 2004). The heartwood is pale yellow to yellow, darken- ing on exposure to yellowish or greenish brown or sometimes to chocolate brown. The wood is some- what greasy and is odourless (Protabase, 2022). The wood is of medium weight, moderately hard, of good durability, being resistant to fungi, dry wood borers and termites. The wood is a highly valued commercial timber in Africa, for which de- mand is also high. It is used for construction work, shipbuilding and marine carpentry, sleepers, sluice gates, framework, trucks, draining boards, outdoor and indoor joinery, stairs, doors, frames, garden furniture, cabinet work, panelling, flooring and profile boards for decorative and structural uses. It is also used for carving, domestic utensils, musi- cal instruments and toys. As it is resistant to acids and bases, it is used for tanks and barrels for food and chemical products and for laboratory benches. It is used as sliced veneer but only rarely as rotary veneer. The wood is also used as firewood and for making charcoal (Protabase, 2022). At 12% mois- ture content, the modulus of rupture is 75–156 N/ mm², modulus of elasticity 8300–13,300 N/mm², compression parallel to grain 42–65 N/mm², shear 5.4–14.1 N/mm², cleavage 10.3–20.9 N/mm, Janka side hardness 4400–5610 N, and Janka end hard- ness 5360–6640 N (Protabase, 2010). Afzelia africana (afzelia) is an evergreen, small to fairly large tree up to 40 m tall; bole branchless for up to 20 m, usually straight and cylindrical, up to 150(–200) cm in diameter. Like other Afzelia spp., the wood of Afzelia africana is characterized by excellent stability with little susceptibility to varia- tions in humidity and a good natural durability. The wood is durable and treatment with preservatives is unnecessary, even for usage in permanently hu- mid conditions or in localities where wood-attack- ing insects are abundant. This makes it an excellent wood for use in pleasure-crafts, especially for keels, stems and panels, for bridges, as well as interior fit- tings. The wood is also valued for joinery and pan- elling, both interior and exterior, parquet floors, doors, frames, stairs, furniture and sporting goods. The wood is also used as firewood and for charcoal production (Gerard & Louppe, 2011). The heartwood is orange-brown to golden brown, becoming red-brown upon prolonged expo- sure, sometimes with darker streaks. It is distinct- ly demarcated from the whitish to pale yellow, up to 8 cm wide sapwood. At 12% moisture content, the modulus of rupture is 105–145(–200) N/mm², modulus of elasticity (9100–)14,000–17,000 N/ mm², compression parallel to grain 57–85 N/mm² (Gerard & Louppe, 2011). Cassia siamea (Senna siamea; yellow casia; kassod tree) is large-sized tree species, with a height up to 20-25 m, diameter 50-60 cm. Its stem is cylindrical, twisted. The bark is grey, with regular small and narrow cracks, sometimes segments are formed due to the stem twisting at some points. (SSR-VINA, 2022). Sapwood and heartwood have different colours; sapwood is pale yellow, heart- wood got yellowish-brown to blackish brown. Sen- na siamea wood can be used for structures requir- ing high durability in construction, and transport (SSR-VINA, 2022). The pressure strength along the grain is 615kg/ cm², the static bending strength is 1520kg/cm², splitting strength is 20kg/cm, collision bending is 0.64, Janka hardness 1,490 lbf (6,640 N), modulus of rupture 12,440 lbf/in2 (85.8 MPa), elastic modu- lus 1,581,000 lbf/in2 (10.90 GPa), crushing strength 10,150 lbf/in2 (70.0 MPa) (Wood database, 2018). Mansonia altissima (African black walnut; Afri- can walnut) is an evergreen medium-sized to fairly large tree up to 45 m tall; bole branchless for up to 30 m, up to 100(–150) cm in diameter, generally straight, cylindrical. The wood is used for general and high-quality joinery, cabinet work, furniture, turnery, decorative veneer and handicrafts. It is also used in construction for doors and windows, in railway coaches and shop fittings, and for boxes and crates (Ohene-Coffie, 2008). The heartwood is yellowish brown to dark grey-brown or even dark brown, often with purple, reddish or greyish green streaks, often in alternat- ing light and dark bands. It fades on exposure to a somewhat dull brown. It is distinctly demarcated from the 2–4(–6) cm wide, white to pinkish sap- wood. The grain is usually straight and the texture fine. The wood is moderately lustrous (Ohene-Cof- fie, 2008). At 12% moisture content the modulus of rupture is (61–)114–177(–183) N/mm², modu- lus of elasticity 9320–12,800 N/mm², compression 34 Les/Wood, Vol. 71, No. 2, December 2022 Ojo, A. R., Ogutuga, S. O., & Aguda, L. O.: Zveza med gostoto in krčenjem lesa osmih tropskih vrst parallel to grain 43–68(–96) N/mm², shear 6–15 N/ mm², cleavage 9–23 N/mm, Janka side hardness 5690–7470 N and Janka end hardness 5740–7470 N (Protabase, 2010). Treculia africana (African breadfruit) is a large, slow-growing, evergreen tree with a dense, spread- ing crown; usually growing 15–30 m tall but with some specimens up to 50 m. The bole is fluted. It is a very valuable food crop in Africa, providing a nutritious protein and oil rich food. It is thus of- ten grown in and around African villages where it is commonly harvested for its edible seeds, which are sold in local markets. Trees are often protect- ed when land is cleared for agriculture (Ken Fern, 2022). The heartwood is yellow with very narrow pale sapwood that is very dense, fairly elastic and flexible, rather heavy, with a fine, even structure. It is suitable for furniture, carving, turnery and in- lay wood, as well as for pulp and papermaking. The wood is used for fuel and making charcoal (Ken Fern, 2022). The wood density of the species is 674 kg/m³ (Keay, 1989). The wood is fairly elastic and flexible (Torelli & Čufar, 1995) and has an even structured fine grain, and saws and planes very eas- ily. Sterculia tragacantha (African tragacanth) is a tree to about 28 m high, the bole sometimes with buttresses, girth up to 1.5 m by 10–15 m long, bear- ing a crown of pseudo-whorled branches. It used for building materials (made from the bark), fibre (wood), pulp and paper (wood), carpentry and related applications (gum, wood), farming, forest- ry, hunting and fishing equipment (gum) (Burkill, 1985). Nesogordonia kabingaensis (danta) is a medi- um-sized to large tree up to 45(–50) m tall, mostly evergreen but sometimes briefly deciduous. The bole is usually straight and cylindrical, branchless for up to 25 m and 80(–120) cm in diameter, with narrow buttresses up to 3 m high (Oyen, 2005). The heartwood is pale brown to purplish brown with a tendency to become lighter on ex- posure to light, distinctly demarcated from the pale brown to pink sapwood, which is 2–5(–10) cm thick. The grain is straight or interlocked, the tex- ture fine. At 12% moisture content the modulus of rupture is 108–183(–231) N/mm², modulus of elas- ticity (7800–)10,900–16,200 N/mm², compression parallel to grain 45–75 N/mm², shear 8–16 N/mm², and cleavage 13–31 N/mm (Oyen, 2005). The species Nauclea diderrichii, Mansonia al- tissima , Nesogordonia kabingaensis, Cassia sim- ea, Afzelia africana and Milicia excelsa are all well known, while Treculia africana and Sterculia tra- gantha are less familiar. They grow in the natural forests in Nigeria, and due to the afforestation and reforestation efforts of the government and private individuals a number of plantations of the species are being established. The trees are very important in Nigeria and elsewhere because the woods are hardwood and naturally durable, and thus suitable for various construction purposes. The general objective of this study is to es- tablish the relationship between the density and shrinkage/swelling of the wood of the selected spe- cies, and thus its specific objectives are as follows: determination of density, evaluation of the radial, tangential and volumetric shrinkage of the wood and their correlations with the density. 2 MATERIALS AND METHODS 2 MATERIALI IN METODE 2.1 DETERMINATION OF WOOD DENSITY 2.1 DOLOČANJE GOSTOTE LESA Two discs, 20 cm long were cut from each of the species at the base and top. Selection of rep- resentative samples for test was carried out from the central planks obtained from each of the discs to give 16 planks from where test samples for all the experiments were obtained. Ten samples were collected for each of the species from the bark to the pith resulting in eighty (80) test samples. For the determination of density, test samples of di- mensions 20 x 20 x 60 mm were produced from the central planks. The test samples were oven-dried to a constant weight, and the density was thus de- termined as given below in accordance with the American Standard for Testing Materials (ASTM D) 2395 (1983): D M V kg m =       3 (1) 35 Les/Wood, Vol. 71, No. 2, December 2022 Ojo, A. R., Ogutuga, S. O., & Aguda, L. O.: Correlation between dry density and shrinkage in eight tropical hardwood species Where: D = density M = weight of the wood V = volume of wood 2.2 DETERMINATION OF PERCENTAGE SHRINK- AGE 2.2 DOLOČANJE KRČENJA Test specimens of 20 x 20 x 60 mm were pro- duced, which were then properly aligned and de- noted ‘T’ and ‘R’ for tangential and radial planes, respectively. They were soaked in water for 48 hrs in order to get them conditioned to moisture above the fibre saturation point (FSP). Specimens were re- moved one after the other, and their dimensions in wet condition were taken to the nearest millimetre with the aid of a vernier calliper. The percentage shrinkages along the two planes were measured af- ter specimens had been oven-dried as S DD D x SO S = − 100 (2) Where: S = shrinkage % D S = dimensions at saturated condition D O = dimensions at oven dry condition Volumetric shrinkage is approximately equal to the sum of radial and tangential shrinkage, as given below: SSS vR T =+ (3) Where: S V = volumetric shrinkage S R = radial shrinkage S T = tangential shrinkage This is in accordance with the approximations done by Dinwoodie (1989). Anisotropy S S T R = (4) 2.3 EXPERIMENTAL DESIGN AND DATA ANALYSIS 2.3 EKSPERIMENTALNA ZASNOVA IN ANALIZA PODATKOV The design adopted for the experiment was a completely randomized design with ten replica- tions each and the data obtained were subjected to analysis of variance (ANOVA), correlation, linear and non-linear regression. 3 RESULTS AND DISCUSSION 3 REZULTATI IN RAZPRAVA 3.1 DENSITY 3.1 GOSTOTA The highest mean density was observed in Milicia excelsa with 900.63±50.13 kg/m³, followed by Afzelia africana, Nesogordonia kabingaensis and Nauclea diderichii with 831.25±41.67 kg/m³, 808.75±20.88 kg/m³ and 801.88±46.40 kg/m³, respectively. The mean density for Cassia sim- ea was 781.88±27.71 kg/m³, Mansonia altissima 593.13±65.98 kg/m³, and Sterculia tragacantha 481.25±111.73 kg/m³, while the least density was ob- served in T reculia africana with 463.75±67.88 kg/m³. According to Brandon (2005), who classified wood species based on their density (the density of seasoned timber is usually measured for clas- sification purposes at 12% air-dry MC) as follows: exceptionally light – under 300 kg/m³, light – 300 to 450 kg/m³, medium – 450 to 650 kg/m³, heavy – 650 to 800 kg/m³, and very heavy – 800 to 1000+ kg/m³. Based on this classification, Milicia excelsa, Afzelia africana, Nesogordonia kabingaensis and Nauclea diderichii are termed very heavy density wood while Cassia simea to be heavy and Manso- nia altissima , Sterculia tragacantha and Treculia af- ricana have medium density wood (Table 1). According to Jane (1970), wood from different parts of a tree is noted to show differences in den- sity, and according to Panshin and de Zeeuw (1980) this variation exists horizontally from the pith to the periphery, and vertically from the base to the crown of the tree. According to the United nations Food and Agriculture Organization (1985), timber should be graded hard, intermediate or soft, cor- responding to high, medium and low densities. The technical limits between the grades are: high densi- ty above 500 kg/m³, medium density between 500 36 Les/Wood, Vol. 71, No. 2, December 2022 Ojo, A. R., Ogutuga, S. O., & Aguda, L. O.: Zveza med gostoto in krčenjem lesa osmih tropskih vrst and 350 kg/m³, low density less than 350 kg/m³, and only high density timber is acceptable for structural purposes. Chaffe (1991) reported that high cellulose con- tent in wood is a good indication of high density and low lignin content. Density varies greatly de- pending on the anatomical structure of the wood. However, the results of ANOVA show that there is a significant difference among the wood species (Table 2) regarding density. The results of corre- lation analysis indicated that there was a positive correlation between density and tangential shrink- age (0.236) at a 0.01 level of probability, and a pos- itive but not significant correlation among density, radial shrinkage and volumetric shrinkage (Table 3). 3.2 RADIAL SHRINKAGE 3.2 RADIALNO KRČENJE The highest mean radial shrinkage was ob- served in Nesogordonia kabingaensis with 6.98±1.63%, followed by Nauclea diderichii, Milicia excelsa and Mansonia altissima with 4.36±1.64%, 3.98±1.02% and 3.96±1.34%, respectively. The mean RS for Cassia simea was 3.65±1.56%, Afzelia africana 3.12±2.24%, Sterculia tragacantha 3.71±1.06% and for Treculia africana 3.30±1.23% (Table 1). Ogunsanwo (2000), in his work on Triplochi- ton scleroxylon, and Choong et al. (1989) as well as Poku et al. (2001), all reported significant differ- Table 1. Mean values of the parameters from the eight hardwood species; density = oven dry density, ST, SR, SV – tangential, radial and volumetric shrinkage. Preglednica 1. Povprečne vrednosti parametrov lastnosti lesa za osem tropskih listavcev; density – gostota lesa v absolutno suhem stanju, ST, SR, SV – tangencialni, radialni in prostorninski skrček, anisotropy – anizotropija krčenja. Species Density (kg/m³) S T (%) S R (%) S V (%) Anisotropy Nauclea diderrichii 801.88 a ±46.40 4.44 a ±1.42 4.36 a ±1.64 8.79 a ±1.67 1.32 a ±1.00 Mansonia altissima 593.13 c ±65.98 3.96 a ±1.34 5.20 ab ±1.74 9.16 a ±1.55 0.88 a ±0.49 Treculia africana 463.75 b ±67.88 3.30 a ±1.23 3.91 a ±1.49 7.21 ab ±1.42 1.08 a ±0.76 Sterculia tragacantha 481.25 b ±111.73 3.92 a ±1.59 3.71 a ±1.06 7.64 ab ±0.96 1.24 a ±0.71 Nesogordonia kabingaensis 808.75 a ±20.88 7.74 b ±1.40 6.98 b ±1.63 14.71 c ±2.28 1.15 a ±0.20 Cassia siamea 781.88 a ±27.71 3.77 a ±3.21 3.65 a ±1.56 5.11 b ±2.65 2.09 a ±0.10 Afzelia africana 831.25 a ±41.67 4.30 a ±2.01 3.12 a ±2.24 7.42 ab ±3.02 2.01 a ±1.57 Milicia excelsa 900.63 d ±50.13 4.34 a ±0.90 3.98 a ±1.02 8.32 a ±1.34 1.17 a ±0.45 Values with the same letters are not significantly different from one another. Vrednosti z isto črko niso značilno različne. Table 2. Analysis of variance of all parameters. Preglednica 2. Analiza variance vseh parametrov. F-values SV df density SR ST SV Anisotropy Species 7 79.07* 5.8112* 5.9619* 19.756* 0.76ns Error 72 Total 79 * = significant at 0.05 level of probability ns = not significant at 0.05 level of probability * = značilno pri stopnji verjetnosti 0,05 ns = ni značilno pri stopnji verjetnosti 0,05 Table 3. Pearson correlation matrix for the tested parameters. Preglednica 3. Matrika s Pearsonovimi korelacijski- mi koeficienti za testirane parametre. D S R S T S V 1.00 0.107 0.236* 0.191 1.00 0.232* 0.671** 1.00 0.644** 1.00 D S R S T S V ** Correlation is significant at the 0.01 level * Correlation is significant at the 0.05 level ** Korelacija je značilna na ravni 0,01 * Korelacija je značilna na ravni 0,05 37 Les/Wood, Vol. 71, No. 2, December 2022 Ojo, A. R., Ogutuga, S. O., & Aguda, L. O.: Correlation between dry density and shrinkage in eight tropical hardwood species Table 4. Linear and non-linear models of the relationship between oven dry density and shrinkage (S T , S R , S V – tangential, radial and volumetric shrinkage) for each of the species. Preglednica 4. Linearni in nelinearni modeli za proučevanje zveze med gostoto lesa in krčenjem (S T , S R , S V – tangencialni, radialni in prostorninski skrček) vsako vrsto. Species Models ST SR SV Nauclea diderrichii Simple Linear y = -7.967x + 837.2 R² = 0.059 y = 17.77x + 724.4 R² = 0.396 y = 11.42x + 701.3 R² = 0.169 Exponential y = 837.9e-0.01x R² = 0.063 y =726.9e0.022x R² = 0.397 y =707.6e0.014x R² = 0.164 Logarithmic y = -11.4ln(x) + 817.6 R² = 0.025 y = 58.76ln(x) + 720.1 R² = 0.341 y = 88.21ln(x) + 611.5 R² = 0.142 Polynomial y = -10.58x2 + 55.96x + 781.2 R² = 0.234 y = -0.392x2 + 21.43x + 716.9 R² = 0.397 y = 3.413x2–48.16x + 952.8 R² = 0.232 Power y = 817.3x-0.01 R² = 0.028 y = 722.9x0.073 R² = 0.343 y = 634.1x0.108 R² = 0.137 Mansonia altissima Simple Linear y = 11.73x + 546.6 (R² = 0.056) y = 12.85x + 530.1 R² = 0.053 y = 22.32x + 388.6 R² = 0.275 Exponential y = 537.4e0.023x R² = 0.057 y = 520.8e0.025x R² = 0.053 y = 398.2e0.042x R² = 0.265 Logarithmic y = 47.69ln(x) + 529.6 R² = 0.052 y = 12.85x + 530.1 R² = 0.053 y = 226.1ln(x) + 95.09 R² = 0.318 Polynomial y = -1.357x2 + 24.15x + 520.9 R² = 0.057 y = 19.12x2–176.5x + 974.9 R² = 0.165 y = -16.05x2 + 330.1x–1049. R² = 0.534 Power y = 519.3x0.094 R² = 0.054 y = 505.8x0.097 R² = 0.035 y = 226.3x0.434 R² = 0.309 Treculia africana Simple Linear y = 32.89x + 355.1 R² = 0.377 y = -7.649x + 493.6 R² = 0.028 y = 17.56x + 337.1 R² = 0.136 Exponential y = 364.4e0.07x R² = 0.366 y = 494.0e-0.01x R² = 0.036 y = 357.4e0.034x R² = 0.114 Logarithmic y = 55.04ln(x) + 403.3 R² = 0.178 y = -6.03ln(x) + 471.4 R² = 0.001 y = 113.5ln(x) + 241.6 R² = 0.128 Polynomial y = 33.18x2–161.3x + 586.5 R² = 0.882 y = -9.652x2 + 69.81x + 357.6 R² = 0.219 y = 3.794x2–34.50x + 508.3 R² = 0.144 Power y = 404.4x0.115 R² = 0.168 y = 471.4x-0.02 R² = 0.004 y = 295.9x0.224 R² = 0.107 Sterculia tragacantha Simple Linear y = -22.10x + 568.1 R² = 0.099 y = 60.91x + 255.1 R² = 0.332 y = -2.491x + 534.2 R² = 0.013 Exponential y = 595.0e-0.06x R² = 0.084 y = 232.0e0.185x R² = 0.303 y = 534.4e-0.00x R² = 0.013 Logarithmic y = -34.2ln(x) + 522.4 R² = 0.054 y = 244.2ln(x) + 170.3 R² = 0.420 y = -18.9ln(x) + 553.5 R² = 0.015 Polynomial y = -9.615x2 + 37.15x + 505.6 R² = 0.138 y = -74.71x2 + 621.7x–721.9 R² = 0.672 y = 2.589x2–40.01x + 667.6 R² = 0.032 Power y = 521.5x-0.10 R² = 0.047 y = 178.4x0.745 R² = 0.387 y = 555.3x-0.03 R² = 0.015 38 Les/Wood, Vol. 71, No. 2, December 2022 Ojo, A. R., Ogutuga, S. O., & Aguda, L. O.: Zveza med gostoto in krčenjem lesa osmih tropskih vrst Species Models ST SR SV Nesogordonia kabingaensis Simple Linear y = -7.817x + 869.2 R² = 0.273 y = -5.706x + 848.5 R² = 0.200 y = -5.892x + 895.4 R² = 0.413 Exponential y = 871.2e-0.01x R² = 0.273 y = 848.7e-0.00x R² = 0.196 y = 899.3e-0.00x R² = 0.408 Logarithmic y = -57.0ln(x) + 924.6 R² = 0.276 y = -41.9ln(x) + 889.2 R² = 0.206 y = -83.0ln(x) + 1031. R² = 0.431 Polynomial y = 0.335x2–12.78x + 886.9 R² = 0.273 y = 0.259x2–9.625x + 862.6 R² = 0.202 y = 0.580x2–22.30x + 1008. R² = 0.440 Power y = 932.8x-0.07 R² = 0.276 y = 891.8x-0.05 R² = 0.201 y = 1062.x-0.10 R² = 0.426 Cassia siamea Simple Linear y = -3.671x + 795.7 R² = 0.181 y = -6.415x + 807.8 R² = 0.063 y = -5.760x + 815.4 R² = 0.064 Exponential y = 795.1e-0.00x R² = 0.180 y = 807.4e-0.00x R² = 0.063 y = 814.5e-0.00x R² = 0.062 Logarithmic y = -18.0ln(x) + 800.0 R² = 0.329 y = -22.6ln(x) + 812.9 R² = 0.041 y = -43.0ln(x) + 856.9 R² = 0.099 Polynomial y = 0.745x2–12.59x + 811.8 R² = 0.280 y = -6.455x2 + 52.86x + 680.5 R² = 0.148 y = 10.06x2–131.3x + 1192. R² = 0.379 Power y = 799.4x-0.02 R² = 0.324 y = 812.4x-0.02 R² = 0.041 y = 857.6x-0.05 R² = 0.095 Afzelia africana Simple Linear y = 1.969x + 822.7 R² = 0.009 y = 4.403x + 817.5 R² = 0.056 y = 3.310x + 806.6 R² = 0.057 Exponential y = 821.4e0.002x R² = 0.010 y = 4.403x + 817.5 R² = 0.056 y = 805.3e0.004x R² = 0.064 Logarithmic y = 18.81ln(x) + 805.6 R² = 0.047 y = 24.28ln(x) + 808.6 R² = 0.176 y = 31.82ln(x) + 770 R² = 0.111 Polynomial y = -4.708x2 + 49.52x + 722.5 R² = 0.222 y = -3.664x2 + 41.90x + 752.7 R² = 0.331 y = -1.561x2 + 28.64x + 717.5 R² = 0.209 Power y = 804.7x0.023 R² = 0.050 y = 807.8x0.029 R² = 0.187 y = 770.2x0.039 R² = 0.120 Milicia excelsa Simple Linear y = 21.91x + 805.4 R² = 0.157 y = 8.825x + 865.4 R² = 0.032 y = 15.17x + 774.3 R² = 0.165 Exponential y = 809.2e0.024x R² = 0.163 y = 865.7e0.009x R² = 0.032 y = 782.6e0.016x R² = 0.169 Logarithmic y = 93.44ln(x) + 765.4 R² = 0.166 y = 40.23ln(x) + 846.3 R² = 0.047 y = 115.7ln(x) + 657.0 R² = 0.169 Polynomial y = -9.791x2 + 105.7x + 633.4 R² = 0.177 y = -19.18x2 + 160.7x + 582.8 R² = 0.165 y = -2.082x2 + 47.29x + 654.6 R² = 0.170 Power y = 774.2x0.103 R² = 0.172 y = 848.0x0.043 R² = 0.047 y = 687.5x0.127 R² = 0.173 39 Les/Wood, Vol. 71, No. 2, December 2022 Ojo, A. R., Ogutuga, S. O., & Aguda, L. O.: Correlation between dry density and shrinkage in eight tropical hardwood species ences between radial and tangential shrinkage on lesser-used hardwood species from Ghana. Laus- berget et al. (1985), reported that this could have been caused by the presence of ray cells on the radial plane, with their horizontally aligned cells producing a restraining effect on radial shrinkage. However, Panshin and de Zeeuw (1980) noted that it is related to the rapid reduction of the microfibril angle in the cell wall. The results of the analysis of variance of radial shrinkage show that there were significant differ- ences among the wood species at a 0.05 level of probability (Table 2). However, the results of cor- relation analysis indicate that there was strong and positive significant correlation between radial and tangential shrinkage (0.644**) at a 0.05 level of probability (Table 3), but of all the models devel- oped none of them has a good fit because of the low R 2 for all the species (Fig. 1 and Table 4) The observed changes in wood dimensions as a result of shrinkage are unequal along the three structural directions. This behaviour of wood has been documented widely by various authors (Pan- shin and de Zeeuw 1980; Dinwoodie, 1981; Laus- berg et al., 1995; Ogunsanwo, 2000). However, Pan- shin and de Zeeuw (1980) noted that the geometric disposition of cells along the principal directions is mainly responsible for this observation. Osadare (2001) observed that the noticeable variations in wood properties are influenced prin- cipally by (i) the changes in activities of cambium as it grows older, (ii) genetic constitutions which govern the form and growth of the tree, and (iii) environmental influences. However, the interac- tion of these factors made it difficult to attribute the observed variations in wood properties to only a single factor. The variability of wood character- istics within individual trees is basically related to changes resulting from ageing of the cambium and modifications imposed on the cambial activity by the environmental conditions, genetic and silvicul- tural effects, as noted by Evans (1991). 3.3 TANGENTIAL SHRINKAGE 3.3 TANGENCIALNO KRČENJE The highest tangential shrinkage was observed in Nesogordonia kabingaensis with 7.74±1.40%, followed by Mansonia altissima (5.20±1.74%), Nauclea diderichii (4.44±1.42%) and Milicia excel- sa (4.34±0.90%). The mean tangential shrinkages for Sterculia tragacantha, Afzelia africana, Tre- culiaafricana were 3.92±1.59%, 4.30±2.01% and 3.91±1.49%, respectively, while the least tangen- tial shrinkage was observed in Cassia simea with 3.77±3.21% (Table 1). According to the classifica- tion of Bolza and Keating (1972), TEDB (1994) and Upton and Attah (2003), the tangential shrinkage values are classified as small (3.5-5.0%), medium (5.1-6.0%), large (6.1-8.0%) and very large (above 8.0%) The results of the analysis of variance of tan- gential shrinkage show that there were significant differences among the wood species at a 0.05 level of probability (Table 2), while the follow-up analy- Figure 1. Wood den- sity and radial shrink- age of the eight tropi- cal wood species. Slika 1. Gostota lesa in radialno krčenje osmih tropskih lesnih vrst. 40 Les/Wood, Vol. 71, No. 2, December 2022 Ojo, A. R., Ogutuga, S. O., & Aguda, L. O.: Zveza med gostoto in krčenjem lesa osmih tropskih vrst sis shows that there was no significant difference among the species except for Nesogordonia ka- bingaensis (Table 1). However, the results of the correlation analysis indicated that there was a strong and positive significant correlation between tangential shrinkage and radial shrinkage (0.232*) at the 0.01 level of probability, and a positive but not significant correlation between tangential and volumetric shrinkage (Table 3). Likewise, of all the models developed none of them had a good fit with the data because of the low R 2 for all the spe- cies (Fig. 2 and Table 4). The greatest dimensional shrinkage occurs along the tangential plane, followed by shrinkage along the radial plane while longitudinal shrink- age has been widely reported to be the smallest, ranging from 0.1 to 0.3% (Desch, 1988; Dinwoodie, 1989). The suitability of wood for various end uses has been linked with the tangential/radial shrink- age ratio (ST/SR), also known as anisotropy. Pan- shin and de Zeeuw (1980) noted that a low value of T/R is synonymous with high suitability of wood for end uses. In this study, it is observed that the anisotropy found for the eight species is low, as can be seen in Table 1. 3.4 VOLUMETRIC SHRINKAGE 3.4 PROSTORNINSKO KRČENJE The highest volumetric shrinkage was observed in Nesogordonia kabingaensis, at 14.71±2.28%, followed by Mansonia altissima (9.16±1.55%) Nauclea diderichii (8.79±1.67%) and Milicia excel- sa (8.32±1.34%). The mean volumetric shrinkag- es for Sterculia tragacantha, Afzelia africana, and Treculia Africana were 7.64±0.96%, 7.42±3.02% and 7.21±1.42%, respectively. The least volumet- ric shrinkage was observed in Cassiasimea, at 5.11±2.65% (Table 1). Poku et al. (2001), recorded volumetric shrinkages of 7.51%, 11.51% and 6.21% for Alstonia boonei. Pterocarpus macrocarpus and Ricinodendron hendelotti, respectively, while Kiaei and Samariha (2011) obtained 12.39% for Ulmus glabra grown in Iran. The wide disparity among the eight species could be attributed to their densities and probably the presence of more biomass in latewood cells, as noted by Chudnoff (1976). However, many other factors, such as spiral grain and latewood propor- tion, also affect the variation in the shrinkage of wood (Pilura et al, 2005; Walker, 2006) The results of the analysis of variance of tan- gential shrinkage show that there were significant differences among the wood species at a 0.05 lev- el of probability (Table 2). Moreover, none of the models developed in this work had a good fit be- cause of the low R 2 for all the species (Fig. 3 and Table 4). 4 CONCLUSIONS 4 SKLEPI The use of the eight tropical hardwood spe- cies for this study has provided useful information Figure 2. Wood den- sity and tangential shrinkage of the eight tropical wood spe- cies. Slika 2. Gostota lesa in tangencialno kr- čenje osmih tropskih lesnih vrst. 41 Les/Wood, Vol. 71, No. 2, December 2022 Ojo, A. R., Ogutuga, S. O., & Aguda, L. O.: Correlation between dry density and shrinkage in eight tropical hardwood species regarding the density, shrinkage and anisotropy of the wood and the relationships among them. Based on the findings of this study, the following conclusions were made. Nesogordonia kabingaen- sis shrinks more than the other species studied. Along the radial and tangential plane, there was a positive correlation between wood density, radial, tangential, and volumetric shrinkage but a weak co- efficient of fitness R 2 for the linear and non-linear models for all the species. Statistically significant differences among the eight species could not be established for all the studied parameters. 5 SUMMARY 5 POVZETEK Izbrali smo les osmih tropskih vrst: Nauclea diderichii, Mansonia altissima, Treculia africana, Sterculia tragacantha, Nesogordonia kabingaensis, Cassia simea, Afzelia africana, Milicia excelsa in raziskali gostoto, radialno, tangencialno in volum- sko krčenje ter anizotropijo krčenja ter povezave med njimi. Večina vrst je uveljavljenih, samo Trecu- lia africana in Sterculia tragantha sta z vidika last- nosti lesa manj znani. Za določanje gostote lesa v absolutno suhem stanju so bili izdelani testni vzorci dimenzij 20 x 20 x 60 mm iz centralnih desk spodnjega dela debel. Testni vzorci so bili posušeni v laboratorijskem su- šilniku do konstantne mase, gostota lesa pa je bila tako določena v skladu z ameriškim standardom za testiranje materialov (ASTM D) 2395 (1983). Izdela- ni so bili orientirani vzorci velikosti 20 x 20 x 60 mm; za merjenje tangencialnih in radialnih skrčkov. Les so namočili v vodo za 48 ur, da je dosegel vlažnost nad točko nasičenja celičnih sten (FSP). Dimenzije v mokrem stanju so bile natančno določene s pomoč- jo Venierovega merilnika. Odstotek krčenja vzdolž obeh ravnin je bil izmerjen po tem, ko so vzorci v sušilniku dosegli ravnovesno, absolutno suho sta- nje. Največjo povprečno gostoto je imel les vrste Milicia excelsa z 900,63±50,13 kg/m³, sledijo Afzelia africana, Nesogordonia kabingaensis in Nauclea di- derichii z 831,25±41,67 kg/m³, 808,75±20,88 kg/m³ oziroma 801,88±46,40 kg/m³. Povprečna gostota za les vrst Cassia simea je bila 781,88±27,71 kg/m³, Mansonia altissima 593,13±65,98 kg/m³, Sterculia tragacantha 481,25±111,73 kg/m³, medtem ko je imela najmanjšo gostoto vrsta Treculia africana s 463,75±67,88 kg/m³ (preglednica1). Največje povprečno radialno krčenje je bilo pri lesu vrste Nesogordonia kabingaensis s 6,98 ± 1,63 %, sledijo Nauclea diderichii, Milicia excelsa in Mansonia altissima s 4,36 ± 1,64 %, 3,98 ± 1,02 % in 3,96 ± 1,34 %. Povprečen radialni skrček pri vrsti Cassia simea je bil 3,65 ± 1,56 %, pri vrsti Afzelia africana 3,12 ± 2,24 %, pri Sterculia tragacantha 3,71 ± 1,06 % in pri Treculia africana 3,30 ± 1,23 % (preglednica 1). Največje tangencialno krčenje je bilo zabele- ženo pri vrsti Nesogordonia kabingaensis s 7,74 ± 1,40 %, sledijo Mansonia altissima (5,20 ± 1,74 %), Nauclea diderichii (4,44 ± 1,42 %) in Milicia excelsa Figure 3. Wood den- sity and volumetric shrinkage of the eight tropical wood spe- cies. Slika 3. Gostota lesa in prostorninsko kr- čenje osmih tropskih lesnih vrst. 42 Les/Wood, Vol. 71, No. 2, December 2022 Ojo, A. R., Ogutuga, S. O., & Aguda, L. O.: Zveza med gostoto in krčenjem lesa osmih tropskih vrst (4,34 ± 0,90 %), srednje tangencialno krčenje je imel les vrst Sterculia tragacantha, Afzelia africana in Treculia africana (3,92±1,59 %, 4,30±2,01 % in 3,91±1,49 %), medtem ko je bilo najmanjše tangen- cialno krčenje opaženo pri vrsti Cassia simea s 3,77 ± 3,21 % (preglednica1). Največje prostorninsko krčenje so opazili pri vrsti Nesogordonia kabingaensis s 14,71 ± 2,28 %, sledijo Mansonia altissima (9,16 ± 1,55 %), Nauclea diderichii (8,79 ± 1,67 %) in Milicia excelsa (8,32 ± 1,34 %), povprečno prostorninsko krčenje za vrste Sterculia tragacantha, Afzelia africana, Treculia africana je bilo 7,64±0,96 %, 7,42±3,02 % oziroma 7,21±1,42 %. (preglednica 1). Za les osmih raziskanih tropskih listavcev smo ovrednotili tudi povezave med gostoto absolutno suhega lesa in krčenjem lesa, vendar nismo mogli potrditi statistično značilne povezave. Na podlagi raziskav ugotavljamo, da se les vrste Nesogordonia kabingaensis krči bolj kot les drugih vrst. Determinacijski koeficient R 2 je bil v vseh pri- merih prenizek, da bi lahko potrdili zvezo med go- stoto lesa ter radialnim, tangencialnim in prostor- ninskim krčenjem. REFERENCES VIRI American Society for Testing and Materials D 2395-83 (ASTM) (1983). Standard test methods for specific gravity of wood and wood- base materials. West Conshohocken, Pennsylvania. Reappro- ved in 2007, 9. Barwick, M. (2004). Tropical and subtropical trees–A worldwide en- cyclopaedic guide. London: Thames & Hudson. Bolza, E., & Keating, W. G. (1972). African timbers – the properties, uses and characteristics of 700 species. Melbourne: CSIRO, Di- vision of Building Research, 1-9. Brandon, J. (2005). Properties of wood. Builders guide to aircraft materials – Wood, plywood and adhesives modules. AUF Au- stralia, 9. Burkill, H.M. 1985. The useful plants of west tropical Africa, Vol 5. 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URL: https://www.wood-database.com/the-wood-dictionary/ (30.7.2022) 44 Les/Wood, Vol. 71, No. 2, December 2022 57 Les/Wood, Vol. 71, No. 2, December 2022 Vol. 71, No. 2, 57-66 DOI: https://doi.org/10.26614/les-wood.2022.v71n02a03 1 Univerza v Ljubljani, Biotehniška fakulteta, Oddelek za lesarstvo, Jamnikarjeva 101, 1000 Ljubljana, SLO * e-mail: katarina.remic@bf.uni-lj.si ANALIZA ŽIVLJENJSKEGA CIKLA IN PRILOŽNOSTI ZA ZMANJŠANJE VPLIVOV LESNE INDUSTRIJE NA OKOLJE LIFE CYCLE ASSESSMENT AND OPPORTUNITIES TO IMPROVE ENVIRONMENTAL IMPACTS IN THE WOOD SECTOR Katarina Remic 1* , Matej Jošt 1 UDK 674*620.97 Prispelo / Received: 14.11.2022 Pregledni znanstveni članek/Review scientific article Sprejeto / Accepted: 29.11.2022 . Izvleček / Abstract Izvleček: Analiza življenjskega cikla (LCA) je metoda ocene vplivov na okolje, ki jih ima nek izdelek ali storitev v času celotnega cikla – od pridobivanja surovin do odlaganja na deponijo. LCA sestavljajo štiri faze, ki se med seboj prepletajo in so standardizirane s standardoma ISO 14040:2006 in ISO 14044:2006. Zaradi vsestranske uporabnosti in celostnosti pri sprejemanju strateških odločitev uporaba LCA hitro narašča. Porast uporabe se opaža tudi v lesnopredelovalnem sektorju. Ključne besede: LCA, trajnost, življenjski cikel, okoljski vplivi, krožno gospodarstvo, lesnopredelovalni sektor Abstract: Life cycle assessment (LCA) is a method that analyses the environmental impact of products or services throughout their life cycle – from the acquisition of raw materials to the end-of-life scenario in landfill. LCA consists of four phases that interact with each other and is standardized with ISO 14040:2006 and ISO 14044:2006. Due to its versatility and comprehensive nature with regard to strategic decision making, the use of LCA is growing rapidly, including in the wood sector. Keywords: LCA, sustainability, life cycle, environmental impacts, circular economy, wood sector 1 UVOD 1 INTRODUCTION Analiza življenjskega cikla (Life Cycle Assess- ment – LCA) je metodološki proces, ki se posto- poma razvija že od leta 1960, prvi ISO standard na to temo pa je bil objavljen 1970. LCA obravnava in ocenjuje potencialne regijske in globalne vplive na okolje in na zdravje ljudi med celotno življenjsko dobo nekega izdelka (ali specifične funkcije izdelka) s pomočjo vhodnih in izhodnih parametrov. Zaje- ma vse faze življenjske dobe, od pridobivanja su- rovin, pridobivanja energetskih virov, proizvodnje in distribucije potrebne energije, proizvodnje po- lizdelkov, sestavnih delov in dodatkov, proizvodnje končnih izdelkov in soproduktov, transporta med posameznimi proizvodnimi sistemi, transporta in distribucije končnih izdelkov, pakiranja, uporabe, vzdrževanja, morebitnega recikliranja ter končne- ga odlaganja na deponijo. Glavna funkcija analize življenjskega cikla je omogočanje informiranega odločanja npr. v namene strateških odločitev, na- črtovanja, postavitve prioritet, dizajna ter redizajna izdelkov in procesov. Uporablja se tako v industriji kot tudi v vladnih in nevladnih organizacijah in po- staja ena izmed najbolj popularnih strategij za kon- troliranje količin odpadkov (Ellingsen & Vildåsen, 2022; Pirc Barčić et al., 2022; Quintana-Gallardo et al., 2021; Saadatian et al., 2022; Vilén et al., 2022). Obravnavanje življenjskega cikla je ključno za podporo trajnostnega razvoja pri postopku spre- jemanja zakonov, oblikovanju krožnega gospodar- stva, pri standardizaciji, določanju označb, izdaji znanstvenih napotkov, pri odgovornosti korporacij in doseganju političnih ciljev. LCA omogoča identifi- kacijo priložnosti za izboljšanje trajnostnega vidika posameznih izdelkov ali storitev v različnih obdob- 58 Les/Wood, Vol. 71, No. 2, December 2022 Remic, K., & Jošt, M: Life cycle assessment and opportunities to improve environmental impacts in the wood sector jih njihove življenjske dobe. Hkrati je sledenje in kontroliranje izdelkov (storitev), njihovega življenj- skega cikla in različnih vidikov trajnostnega razvoja glavno izhodišče za boljše razumevanje treh glav- nih stebrov trajnosti (3P) v celotni verigi ponudbe- -povpraševanja. Ti stebri so prebivalstvo, planet in profit oziroma uspeh. Ker analiza življenjskega cikla nudi vpogled v celotni cikel izdelka, se z njo izogne- mo problematiki, kjer zavestno zmanjšamo vplive na okolje v eni fazi življenjskega cikla, pri tem pa (nezavedno) povečamo negativne vplive na okolje v neki drugi fazi cikla. Posledično lahko takšna ana- liza poveča učinkovitost upravljanja s surovinami in energetskimi viri. Kljub čedalje bolj razširjeni upo- rabi in konstantni optimizaciji programske opreme, ki se uporablja za izvedbo LCA, nekatere slabosti te metode še vedno ostajajo. Glavna pomanjkljivost je ogromna količina podatkov, ki jih moramo pridobiti iz baz. Podatki pa so običajno tudi nepopolni ali pa celo neobstoječi za specifično področje in jih mora- mo kombinirati s podatki iz drugih področij. Za iz- vedbo analize življenjskega cikla potrebujemo veli- ko časa, poglobljeno znanje o izdelku in proizvodnih tehnikah ter poglobljeno znanje in izkušnje o vred- notenju raziskave. Kljub temu, da se LCA celostno ukvarja z okoljsko problematiko, pa ne preučuje tehničnih sposobnosti sistema, ekonomskih pos- ledic ter socialnih in političnih vidikov sprememb v preučevanih sistemih (de Carvalho Araújo et al., 2022; Füchsl et al., 2022; Rey-Álvarez et al., 2022; Vance et al., 2022). 2 METODOLOGIJA LCA 2 LCA METHODOLOGY LCA je strukturirana, obširna in mednarodno standardizirana metoda, ki zajema štiri faze: fazo definiranja ciljev in obsega raziskave, fazo analize inventarja, fazo analize vplivov na okolje in fazo interpretacije rezultatov. SAIC (Scientific Applicati- ons International Corporation (SAIC), 2006) in (ILCD European Commission. Joint Research Centre. In- stitute for Environment and Sustainability., 2010) vsako fazo tudi razdelita in definirata kot sosled- je korakov, ki jih mora raziskovalec sprejeti med obravnavanjem posamezne faze. Faza definiranja ciljev in obsega raziskave opre- deljuje podatke, ki narekujejo celotno raziskavo. Postavljeni cilji definirajo razloge za izvedbo razi- skave, določijo, kako detajlno bo raziskava izvedena in ali bo pokrivala široko področje ali bo zelo spe- cifično usmerjena. Obseg raziskave pa poleg koli- čine detajlov, ki bodo upoštevani, opredeljuje tudi omejitve sistema določene raziskave. V kateri fazi sistema se bo raziskava začela in v kateri končala, je zelo različno in pogojeno s subjektivno percep- cijo raziskovalca, kaj v danem primeru predstavlja “cradle” in kaj “grave”. Glede na določen začetek in konec cikla mora biti predmet raziskave jasno zas- tavljen (izdelki oziroma storitve, trženjski segmenti, alternative). Jasno morajo biti opredeljene funkcije sistema (primarne in sekundarne), razdelitve obre- menitev in referenčni diagram, LCIA metodologija, vrste vplivov, geografske, časovne in tehnološke omejitve, interpretacija, ki bo uporabljena, vrsta kritičnega vrednotenja, opredeljeno mora biti, ka- teri podatki so potrebni in kakšna mora biti njihova kvaliteta, lahko pa sta definirana tudi vrsta in for- mat poročila raziskave. Jasno morajo biti oprede- ljene tudi vse funkcionalne enote, ki predstavlja- jo referenčne enote, na katere so preračunani in normirani vsi vhodni in izhodni podatki ter njihovi vplivi na okolje. Poenotenje funkcionalnih enot je pomembno predvsem pri primerjavi različnih izdel- kov. Pomembno je, da so cilji in omejitve zasnovani v skladu z nameravano uporabnostjo raziskave in da je vseskozi znano ali bodo rezultati namenjeni primerjavi javnega značaja ali bodo morda zaupne narave (Hassan et al., 2022; Pirc Barčić et al., 2022; Vance et al., 2022; Vilén et al., 2022). Pri izvajanju prve faze LCA procesa mora raziskovalec sprejeti in definirati šest odločitev: • definiranje cilja projekta; • opredelitev, katera vrsta informacij je potrebna za pomoč pri sprejemanju odločitev; • opredelitev potrebne specifičnosti; • opredelitev, kako naj bodo podatki in rezultati predstavljeni; • definiranje obsega, omejitve raziskave; • opredelitev osnovnih pravil in pogojev dela (beleženje predvidevanj in predpostavk, po- stopki za kontrolo kakovosti, zahteve poročila). Fazo analize inventarja (LCI faza) predstavlja proces kvantifikacije potrebne energije, potrebnih surovin ter nastalih emisij in odpadkov in zajema popis vseh zbranih podatkov, ki so potrebni za do- seganje definiranih ciljev raziskave (Hassan et al., 2022; Pirc Barčić et al., 2022; Vance et al., 2022; 59 Les/Wood, Vol. 71, No. 2, December 2022 Remic, K., & Jošt, M.: Analiza življenjskega cikla in priložnosti za zmanjševanje vplivov lesne industrije na okolje Vilén et al., 2022). Glavni koraki za izvedbo LCI faze so: • razvoj diagrama procesa (“flow diagram”); • razvoj načrta zbiranja podatkov; • proces zbiranja podatkov; • evalvacija in poročanje rezultatov. Diagram procesa (življenjskega cikla izbranega izdelka) grafično prikazuje vse primarne in sekun- darne procese v obravnavanem sistemu, prido- bljeni podatki pa vključujejo kvalitativne in kvan- titativne podatke za vsako fazo procesa znotraj omejitev. Pomembno je, da je vsaka faza procesa natančno opisana, da ne prihaja do napak oziroma napačnega razumevanja. Pri postavljanju diagrama procesa je najpomembnejša ohranitev sistemske enakosti, ki predstavlja ohranitev mase in energije znotraj oblikovanega diagrama. Osnovni problem analize življenjskega cikla je določevanje mej med aktivnostmi, ki sodijo v preučevani sistem, in ak- tivnostmi, ki spadajo v življenjski cikel predelanih ali že recikliranih izdelkov. V primeru odprte zanke recikliranja, ko se reciklirani materiali porabijo za drug izdelek, se delež materiala “odcepi” od glav- nega sistema, posledično mora ocenjevalec preso- diti, kateri način razmejitve obremenitev na okolje bo uporabil. Prvemu (glavnemu) izdelku pripadajo obremenitve pridobivanja surovin, procesa proi- zvodnje, uporabe in odstranjevanja nerecikliranih materialov, drugemu (odcepljenemu) pa obremeni- tve pridobivanja manjkajočih primarnih materialov, obremenitve proizvodnje, uporabe in odstranjeva- nja tega izdelka. Obremenitve na okolje, ki nastajajo v procesu reciklaže, lahko v celoti pripišemo ali pr- vemu ali drugemu izdelku. Obremenitve lahko tudi razdelimo in vsakemu pripišemo polovico. Lahko pa upoštevamo skupne obremenitve prvega in druge- ga izdelka v fazah pridobivanja primarnih materia- lov, recikliranja in odstranjevanja ter jih delimo na pol. Pri zaprti zanki recikliranja do tega problema ne prihaja. Poleg razmejitve sistema z deljenjem obre- menitev, čemur standard ni naklonjen, obstaja tudi razširitev sistema. Pri tem soprodukte, ki nastajajo, obravnavamo kot samostojne proizvode, ki služijo kot (okoljsko boljša) alternativa drugim izdelkom na trgu/v industriji in pri izračunu zmanjšujejo vplive celotnega cikla na okolje. Podatke za izvedbo LCA delimo na glavne informacije, ki se nanašajo direk- tno na obravnavani sistem, npr. emisije pri lakiranju stola, in na informacije “iz ozadja”, ki jih prav tako pridobimo iz baz podatkov, vendar se ne nanaša- jo direktno na obravnavani sistem, npr. predhodna analiza življenjskega cikla sadike drevesa (Ellingsen & Vildåsen, 2022; Pirc Barčić et al., 2022; Vilén et al., 2022). Namen faze analize vplivov na okolje je prido- bivanje dodatnih informacij, ki so v pomoč pri razu- mevanju in vrednotenju rezultatov iz LCI faze. Tretjo fazo imenujemo tudi LCIA faza. Zajema razumeva- nje in ocenjevanje razsežnosti in pomembnosti ne- kega potencialnega vpliva na okolje in zdravje ljudi. Kljub temu da lahko na podlagi podatkov inventarja preučujemo mnogo različnih področij in tez, je faza analize vplivov namenjena predvsem pridobivanju ključnih osnov za izvedbo primerjav (med različni- mi scenariji in posledično različnimi vrstami emisij) (Hassan et al., 2022; Pirc Barčić et al., 2022; Vance et al., 2022; Vilén et al., 2022). Glavni koraki izved- be LCIA faze so: • izbor in definiranje vplivnih kategorij; • klasifikacija (razporeditev rezultatov iz LCI faze v izbrane kategorije vpliva, npr. vpliv CO 2 raz- poredimo v kategorijo segrevanje ozračja); • karakterizacija (pretvorba vplivov iz LCI faze v kategorije vpliva s pomočjo skupnih faktorjev karakterizacije (npr. vpliv CO 2 preračunamo kot potencialni vpliv na segrevanje ozračja); • normalizacija (potencialne vplive izrazimo tako, da jih lahko med samo primerjamo); • združevanje (razvrščanje npr. po razsežnosti merila); • razvrščanje po pomembnosti, dodelitev uteži; • evalvacija in priprava poročila LCIA rezultatov. Faza interpretacije rezultatov združuje rezulta- te LCI in LCIA faz (fazi sta lahko obravnavani združe- no ali pa vsaka posebej), ki so obravnavani in obli- kovani v povzetek. Ta služi kot razprava rezultatov za izdelavo napotkov pri odločanju in kot usmeritev za sprejemanje odločitev v skladu s postavljenimi cilji. Vsebovati mora identifikacijo ključnih proble- mov glede na rezultate LCI in LCIA faz, celostno vrednotenje, kontrolo občutljivosti in doslednosti, zaključke, omejitve in priporočila (Ellingsen & Vil- dåsen, 2022; Hassan et al., 2022; Pirc Barčić et al., 2022; Vance et al., 2022; Vilén et al., 2022). Inter- pretacija rezultatov zajema: • identifikacijo ključnih problematik na osnovi LCI in LCIA faz; 60 Les/Wood, Vol. 71, No. 2, December 2022 Remic, K., & Jošt, M: Life cycle assessment and opportunities to improve environmental impacts in the wood sector Preglednica 1. Kategorije vplivov za analizo življenjskega cikla izdelkov in storitev (de Carvalho Araújo et al., 2022; Klein et al., 2015; Scientific Applications International Corporation (SAIC), 2006; Vance et al., 2022). Table 1. Impact categories for life cycle assessment of products and services (de Carvalho Araújo et al., 2022; Klein et al., 2015; Scientific Applications International Corporation (SAIC), 2006; Vance et al., 2022). Kategorija vpliva Razse- žnost merila Klasifikacija podatkov analize inventarja Skupen faktor karakterizacije Enota Segrevanje ozračja Skupno Globalno CO 2 (ogljikov dioksid), NO 2 (dušikov dioksid), CH 4 (metan), CFC (klorofluoro- ogljikovodiki), HCFC (hidroklorofluoro- ogljikovodiki), CH 3 Br (metil bromid) Potencialno se- grevanje ozračja kg CO 2 ali ekvivalent Fosilna goriva Biogeni vplivi Tanjšanje stratosferske ozonske plasti Globalno CFC, HCFC, CH 3 Br, haloni Potencialno tanjšanje ozonske plasti kg CFC-11 ali ekvivalent Zakisovanje Regijsko in lokalno SOx (žveplovi oksidi), NOx (dušikovi oksi- di), HCl (klorovodikova kislina), HF (fluorovo - dikova kislina), NH 4 (amonijak) Potencialno zaki- sovanje kg mol H+ Evtrofikacija Evtrofikacija sladkih voda Lokalno PO 4 (fosfati), NO (dušikov oksid), NO 2 , nitrati, NH 4 Potencialna evtrofikacija kg PO 4 ali ekvivalent Evtrofikacija morskih voda kg N ali ekvivalent Evtrofikacija zemlje mol N Fotogemičen smog Lokalno NMHC (ne-metanski ogljikovodiki) Potencial pojava fotokemičnega smoga kg NMVOC ali ekvivalent Izraba surovin Izraba abiotskih surovin – mine- ralov in kovin Globalna, regijska in lokalna Količina porabljenih mineralov in kovin Potencial izrabe surovin kg Sb ali ekvi- valent Izraba abiotskih surovin – fosilna goriva Količina porabljenih fosilnih goriv MJ (neto) Toksični vplivi na človekovo zdravje Karcinogeni Globalno, regijsko in lokalno Skupni izpusti kemikalij v zrak, vodo in zemljo LC 50 CTU (št. bolezni na kg kemikalije) Nekarcinogeni Ekotoksičnost Sladkih voda Lokalno Toksične kemikalije, za katere je bila ugotovljena smrtna koncentracija za določeno vrsto organizmov LC 50 (za sladko- vodne organizme) CTU (št. Refe- renčnih toksič- nih vplivov na kg kemikalije) Morske vode LC 50 (za morske organizme) Zemlje LC 50 (za glodalce) Raba vode Regijsko in lokalno Porabljena voda Potencialno po- manjkanje vode Pomanjkanje povprečne količine pora- bljene vode na svetovnem nivoju v m 3 61 Les/Wood, Vol. 71, No. 2, December 2022 Remic, K., & Jošt, M.: Analiza življenjskega cikla in priložnosti za zmanjševanje vplivov lesne industrije na okolje • evalvacijo, ki zajema preverjanje celostnosti, občutljivost in doslednosti; • pripravo zaključkov, priporočil in poročila. 3 KATEGORIJE IN PARAMETRI 3 CATEGORIES AND PARAMETERS V preglednici 1 so prikazane kategorije vpli- vov na okolje, ki jih lahko obravnavamo v okviru LCA raziskave. Kategorije lahko na okolje in človeka vplivajo na različnih nivojih razsežnosti (lokalnem, regijskem ali globalnem nivoju), oziroma se vpli- vi kažejo na večrazsežnostnih nivojih. Preglednici je dodana klasifikacija podatkov, ki nastane v fazi analize inventarja in predstavlja najpogostejše po- datkovne parametre, ki vplivajo na določeno kate- gorijo. Vse te podatke se pri izračunih združuje na skupni faktor karakterizacije s funkcionalno enoto, ki je glavna referenčna vrednost za primerjavo (Qu- intana-Gallardo et al., 2021). 4 KROŽENJE OGLJIKA IN IMPLEMENTACIJA LCA V LESNOPREDELOVALNO INDUSTRIJO 4 CARBON CYCLE AND IMPLEMENTATION OF LCA IN WOOD SECTOR Ogljik je četrti najbolj razširjen element v ve- solju in glavni vir življenja na Zemlji. Največji delež ogljika na Zemlji je vezan v kamenje in skalovje, pre- ostali del pa je v oceanu, atmosferi, rastlinah, zemlji in fosilnih gorivih. S kopičenjem ogljika v skalovju se regulira količina ogljika v atmosferi, posledično pa tudi temperatura na Zemlji. Količina vodne pare v ozračju sorazmerno narašča in pada s povečanjem oziroma zmanjšanjem koncentracij CO 2 v atmosferi, zemlja pa se segreje pri povečanih količinah vod- ne pare v ozračju in obratno. Ogljikov dioksid, ki je vezan v rastlino (ali fitoplankton), se sprosti nazaj v atmosfero šele, ko pride do fotosintezi obratne kemijske reakcije. Ta nastopi v štirih različnih scena- rijih. V želji po pridobivanju energije lahko rastline same porabijo sladkor, ko potrebujejo energijo za rast ali pa živali in ljudje pojedo rastline. Do spro- ščanja CO 2 prihaja tudi, ko rastline odmrejo in se razkrajajo ali pa če zgorijo. Lesni izdelki vsebujejo ogljik, ki so ga absorbirali v fazi rasti drevesa v pro- cesu fotosinteze. Znano je, da drevo za vsak kubik svoje rasti absorbira 1 tono CO 2 iz atmosfere in pro- izvede 0,7 tone kisika. Večinski del (0,9 tone) CO 2 drevo obdrži absorbiranega po procesu rasti in se v lesu ohranja ne glede na to, kako ga predelujemo (v kakšne izdelke). Izloči se šele, ko nastopi eden izmed štirih scenarijev. Lesna biomasa je pogos- to opisana kot obnovljiv, trajnostni vir surovine in energije. Čeprav se les smatra kot zelo dobra alter- nativa marsikateremu drugemu materialu z večjim ogljičnim odtisom, pa je nivo dejanske obnovljivosti in trajnosti odvisen od količine neobnovljivih virov, ki smo jih vnesli v sistem predelave. Ogljično nev- tralnost zmanjšujejo gojeni sistemi dreves in netraj- nostno upravljanje z gozdnimi sistemi. V splošnem življenjski cikel lesnih izdelkov zajema fazo pridobi- vanja surovin (aktivnosti gojenja gozdov, sečnja in spravilo lesa iz gozda), fazo proizvodnje materialov (predelava hlodovine v žagane elemente, ploščne kompozite, itd.), fazo uporabe in vzdrževanja ter fazo uničenja in odstranjevanja na deponijo. Med vsemi fazami se pojavljata distribucija in transport. V fazo proizvodnje so zajete tudi vse aktivnosti se- kundarne predelave, kjer so posamezni materiali Kategorija vpliva Razse- žnost merila Klasifikacija podatkov analize inventarja Skupen faktor karakterizacije Enota Raba tal Globalno, regijsko in lokalno Količina odloženih odpadkov na organi- zirana in neorganizirana odlagališča ter ostali posegi v prostor/tla Razpoložljivost tal Ni merljivo v konstantnih enotah, spremembe v kvaliteti zemlje Radioaktivnost Lokalno, regijsko Pojavljanje negativnih stranskih učinkov na ljudeh in ekosistemih zaradi sevanja Potencialni vpliv na človeško zdravje KBq U-235 Emisije drobnih delcev Lokalno, regijsko Indikator pogostosti obolenj zaradi emisij drobnih delcev Potencialna pogo- stost obolenj Pogostost obolenj 62 Les/Wood, Vol. 71, No. 2, December 2022 Remic, K., & Jošt, M: Life cycle assessment and opportunities to improve environmental impacts in the wood sector uporabljeni in vgrajeni v izdelek. Nadaljnja uporaba se lahko pojavlja v različnih oblikah. Kot ponovna uporaba, kjer izdelek uporabimo za isti namen, kot predelava, kjer izdelek uporabimo za drug namen ali pa kot recikliranje, kjer izdelek predelamo v surovino za nadaljnjo rabo (Aryapratama & Pau- liuk, 2022; Cordier et al., 2022; Duan et al., 2022; Fimbres Weihs et al., 2022; Klein et al., 2015; Pirc Barčić et al., 2022). Na sliki 1 je prikazano kroženje lesa v Evropi, ki si prizadeva za čimbolj celovito rabo lesa in lesnih ostankov. Prvotne LCA raziskave za lesnopredelovalno verigo so se osredotočale na manjše segmente (produkte) lesne industrije, danes pa se analiza življenjskega cikla večinoma uporablja za celostno vrednotenje lesnih alternativ v gradbeništvu. Grad- nja bivalnih in javnih objektov je v zadnjih letih močno narasla, hkrati pa je gradbeni sektor postal ciljni sektor za zmanjševanje vplivov na okolje, saj vsako leto proizvede kar 39 % vseh svetovnih emi- sij (Andersen et al., 2022). Podatki kažejo, da bi z uvedbo 17 % lesa kot alternativnega materiala, emi- sije v gradbeništvu zmanjšali za 20 %. Pri LCA, kjer je bila lesena gradnja celostno obravnavana (Duan et al., 2022), pa je bilo ugotovljeno, da bi emisije lahko zmanjšali za kar 22-50 %. Najnovejše direkti- ve Evropske unije izpostavljajo nujo po zmanjšanju emisij stavb do leta 2050, kar podpira tudi iniciativa novi evropski Bauhaus, ki temelji na okolju prijazni gradnji in zajema estetska, trajnostna in inkluzivna načela. Izvedene so bile analize občutljivosti (Duan et al., 2022) za izolacije, osnovne materiale, uporabo fenol-formaldehidne smole, razdaljo transporta, vrsto uporabljene energije, energijsko učinkovitost, prehajanje zraka, uporabo recikliranih materialov, upravljanje z ostanki biomase, življenjsko dobo, učinkovitost toplotne črpalke in še posebej za delež ponovno uporabljenega lesa. Kot najbolj vplivni in ključni za nadaljnjo raziskovanje njihovih alternativ- nih možnosti so se izkazali: izolacija (Bucklin et al., 2022; Duan et al., 2022; Füchsl et al., 2022; Galim- shina et al., 2022), vrsta uporabljenih lesnih kom- pozitov (Andersen et al., 2022; Bucklin et al., 2022; Cascione et al., 2022; Duan et al., 2022; Kromoser et al., 2022), transport materiala za gradnjo (Duan et al., 2022), vrsta uporabljene energije (Duan et al., 2022; Saadatian et al., 2022; Tushar et al., 2022) in vrsta oken (Duan et al., 2022; Saadatian et al., 2022; Tushar et al., 2022), kjer so še posebej opa- zne prednosti uporabe lesenih oken v primerjavi s PVC, aluminijastimi oziroma kompozitnimi (les-alu- minij) sistemi oken. Pomembno vplivajo tudi ostali dejavniki, kot sta razmerje velikosti oken glede na steno in orientacija oken v objektu. Analiza vplivov na okolje (Quintana-Gallardo et al., 2021) pri biva- nju v primerljivih stanovanjskih objektih na različnih lokacijah po Evropi kaže, da je prav lokacija najbolj vplivala na okoljsko obremenjujoče razlike pri emi- sijah, še posebej na porabo elektrike in vrsto vira energije. Zaradi potrebe po ponovni uporabi odslu- ženega lesa (Szichta et al., 2022) se uveljavljajo tudi LCA raziskave, ki se osredotočajo na rušenje objek- tov z (deloma) lesenimi konstrukcijami in upravlja- nje z njimi po končani življenjski dobi, še posebej pa pretvarjanje odsluženega lesa v izdelke, surovino ali snovi z višjo dodano cenovno in funkcionalno vre- Slika 1. Kroženje lesa v Evropi (prirejeno po Man- tau, 2012). Figure 1. Wood flow in Europe (adapted from Mantau, 2012). 63 Les/Wood, Vol. 71, No. 2, December 2022 Remic, K., & Jošt, M.: Analiza življenjskega cikla in priložnosti za zmanjševanje vplivov lesne industrije na okolje dnostjo (Ivanica et al., 2022; Khodaei et al., 2022). Hkrati se razvijajo inovativni kompoziti, ki vključu- jejo les. Pri razvoju lesno-betonskega kompozita za talne obloge (Tighnavard Balasbaneh et al., 2022) so se prednosti pokazale ne samo pri zmanjšani rabi betona in zmanjšanju negativnih vplivov na okolje, ampak tudi pri mehanskih lastnostih tega kompozi- ta. Duan in sodelavci (2022) poudarjajo, da lesena gradnja ni vedno upravičena, oziroma ne pomeni avtomatskega zmanjšanja emisij na okolje, še pose- bej v državah in pokrajinah, ki niso bogato porašče- ne z gozdom. Quintana-Gallardo in sodelavci (2021) izpostavljajo še pretirano poenostavljanje okoljske učinkovitosti lesene gradnje in dodatno pojasnjuje- jo, da je za dejansko zmanjšanje vplivov na okolje potrebna implementacija različnih biomasnih ma- terialov tudi v druge elemente celotne stavbe – ne samo uporaba lesa za konstrukcijo objekta. Velik delež negativnih vplivov na okolje predsta- vljajo nelesni materiali v lesnih sistemih npr. smole in površinski premazi. S pomočjo LCA raziskovalci poskušajo opredeliti možnosti na zmanjšanje vpli- vov že med proizvodnjo smol in veziv (Vujanović et al., 2022) oziroma razviti alternativne »zelene smo- le« na osnovi taninov (Hu et al., 2023) sojinih pro- teinov (Liu et al., 2022), agro-industrijskih ostankov lignina (de Carvalho Araújo et al., 2022). S tem bi se izognili (tolikšni) uporabi fenol-formaldehida. De Carvalho Araújo in sodelavci (2022) poudarjajo tudi pomembnost biomimikrije in nanodelcev pri razvo- ju novih sistemov in rešitev. Razširjena pa postaja tudi proizvodnja in uporaba lesno-plastičnih kom- pozitov, tudi na osnovi odsluženega lesa (de Carval- ho Araújo et al., 2022; Friedrich, 2022; Huang et al., 2022). Potreba po produktih iz biomasnih ostankov z višjo dodano vrednostjo se v veliki meri obravnava v okviru biorafinerij in manjših predelovalnih obra- tov. Ti na podlagi LCA ter stroškovnih analiz oprede- lijo smiselnost pridobivanja, ekstrakcije, produkcije, zbiranja odpadkov in njihove pretvorbe (Zhang et al., 2023). V praksi se iz lignocelulozne biomase že pridobiva vodik (Buffi et al., 2022; Wu et al., 2023), nanoceluloza (Shahzad et al., 2023), mlečne kisline, ksilitol, etanol, metan, različne lipide, betakaroten (Zhang et al., 2023), itd. To so običajno zgolj ciljni produkti, tehnološke izboljšave pa bi omogočile še dodatne stranske produkte, ki so bili do sedaj namenjeni le sežigu – pridobivanju energije. V to skupino velikokrat odpade lignin, ki je kljub njegovi uporabnosti stroškovno ugodnejši za pridobivanje energije kot za nadaljnjo predelavo v vanilin, polihi- droksialkanoate in aldehide. Raziskave zato ocenju- jejo možnosti uporabe lignina kot celote za različne namene npr. kot del asfaltnega sistema (Moretti, 2023). Ugotovljeno je bilo, da znotraj lesnoprede- lovalne biorafinerije lignifikacija predstavlja 80 % vseh vplivov ekotoksičnosti sladkih voda in zemlje, saharifikacija pa predstavlja nezanemarljivo gene- racijo drobnih delcev, evtrofikacijo sladkih voda, segrevanje ozračja, toksičnost za ljudi in ekotoksič- nost zemlje (Zhang et al., 2023). 5 ZAKLJUČKI 5 CONCLUSIONS Analiza življenjskega cikla je standardizirana metoda ocene vplivov nekega izdelka ali storitve na okolje v času celotnega življenjskega cikla. Zajema pridobivanje surovin, pridobivanje potrebnih ener- getskih virov, proizvodnjo in distribucijo potrebne energije, proizvodnjo polizdelkov, potrebnih sestav- nih delov in dodatkov, proizvodnjo končnih izdelkov in soproduktov, transport med posameznimi proi- zvodnimi sistemi, transport in distribucijo končnih izdelkov, pakiranje, uporabo, vzdrževanje, morebi- tno recikliranje ter končno odlaganje na deponijo. LCA zajema štiri faze, ki se med seboj interak- tivno prepletajo in dopolnjujejo. Prva faza je faza definiranja ciljev in obsega raziskave. V samem začetku mora raziskovalec jasno definirati razloge za raziskavo in posledično postaviti cilje raziskave. Ključna je ustrezna izbira omejitev LCA, ki zajema obseg, specifičnost, količino podatkov, začetno in končno fazo obravnavanega sistema in vse vmesne faze sistema ter način raziskave in njeno kontrolo doslednosti. Sledi faza analize inventarja, ki zajema popis vseh potrebnih podatkov za izvedbo raziska- ve in njihovo vrednotenje. Faza zajema tudi razvoj diagrama procesa, ki grafično prikazuje vse faze znotraj življenjskega cikla izdelka. Tretja faza je faza analize vplivov na okolje, kjer raziskovalec podatke iz druge faze smiselno pripiše kategorijam, ki pred- stavljajo različne vplive na okolje in jih normalizira tako, da so vrednosti primerljive med sabo. V zad- nji fazi, fazi interpretacije, so obravnavani rezultati druge in tretje faze. Oblikuje se povzetek raziskave, ki mora vsebovati identifikacijo ključnih problemov 64 Les/Wood, Vol. 71, No. 2, December 2022 Remic, K., & Jošt, M: Life cycle assessment and opportunities to improve environmental impacts in the wood sector glede na rezultate LCI in LCIA faz, celostno vredno- tenje, kontrolo občutljivosti in doslednosti, zaključ- ke, omejitve in priporočila. Les je pogosto opisan kot obnovljiv in trajno- stni vir surovine, energije in kot okoljsko zelo dobra alternativa marsikateremu drugemu materialu. Če drevesa rastejo v gozdnih sistemih, ki so upravljani po trajnostnih načelih, lahko les predstavlja ogljič- no nevtralno surovino. Kljub temu pa lahko lesen izdelek v svojem življenjskem ciklu ustvari neza- nemarljivo količino negativnih vplivov na okolje, zato je izvedba LCA smiselna za ohranitev okoljske nevtralnosti v čim večji meri. Dosedanje raziskave so opredelile izzive lesne industrije s problematič- nimi vplivi na okolje, ki se nanašajo predvsem na pomožne materiale in transport, in izpostavile učin- kovitejše možnosti upravljanja z lesno biomaso za pridobivanje trajnostnih produktov z višjo dodano vrednostjo. To podpira tudi iniciativa novi evropski Bauhaus, ki predlaga LCA metodologijo kot mož- nost za vodilo oblikovanja stavb, saj bi celostno obravnavanje pripomoglo k praksam, ki stremijo k dolgi življenjski dobi, uporabljajo obnovljive vire, ponovno uporabljajo odslužen material in zmanjšu- jejo vplive na okolje, ki nastajajo zaradi transporta. Hkrati takšne prakse vseeno ohranjajo raznoliko kulturo in ne omejujejo kreativnega razvoja. 6 POVZETEK 6 SUMMARY Life cycle assessment (LCA) is a methodologi- cal process that has been developing since 1960. It discusses and evaluates products and services throughout their life cycle. It covers the acquisition of raw materials and energy, production and distri- bution of energy, production of intermediate prod- ucts, main products and by-products, production of final products and co-products, transport between production systems, transport and distribution of final products, packaging process, use, mainte- nance, possible recycling and final landfill scenario. LCA is mainly a tool for strategic decision making, but it can also be used to identify opportunities for improvement throughout the product production process. The main disadvantage of LCA is the huge amount of data needed coupled with the lack of ac- curate data that is available. LCA consists of four phases. The first phase is the definition of the aim and scope, in which the re- searcher defines the main purpose of the LCA and, accordingly, the goals of the research. It is also very important to define the scope properly – where is the beginning of the analysed system, where is the end and which production phases are included in the system. This is followed by the inventory analy- sis (LCI phase), where a flow chart is created, a plan for data collection is designed and all the necessary data is collected and analysed. The third phase is the impact assessment phase. In this phase of the research process, all data from the previous phase are classified into impact categories and further normalized so that all data have the same function- al unit. The following impact categories are consid- ered in LCA: climate change (which is described as the potential for global warming and can be divided into general climate change, climate change from fossil fuels and climate change from biogenic emis- sions), ozone depletion (which is caused in particu- lar by the presence of CFCs, HCFCs, CH 3 Br and hal- ogens in the atmosphere), acidification (especially of soil), eutrophication (which is subdivided into eutrophication of freshwater, marine eutrophica- tion or terrestrial eutrophication), photochemical ozone formation (which occurs due to NMHCs in the atmosphere), resource depletion (resources are subdivided into minerals and metals and fos- sil fuels), human toxicity (subdivided into carcino- genic and non-carcinogenic due to the presence of certain chemicals in the atmosphere), ecotoxicity (of freshwater, marine and terrestrial ecotoxicity), water use, land use, ionizing radiation and partic- ulate matter emissions (indicating how frequently various diseases occur due to the presence of such emissions). Finally, the interpretation phase takes place, in which all data sorted by category are eval- uated, the most important hotspots (phases in the system with the most problematic environmental impacts) are identified and conclusions and recom- mendations are formulated. Wood products contain carbon that was ab- sorbed by the trees during their growth phase through photosynthesis. As long as the wood does not rot or burn, CO 2 remains in the wood. And even then, only the amount of CO 2 that was absorbed during growth is released. The goal is, however, is to delay incineration by reusing it as much as possi- 65 Les/Wood, Vol. 71, No. 2, December 2022 Remic, K., & Jošt, M.: Analiza življenjskega cikla in priložnosti za zmanjševanje vplivov lesne industrije na okolje ble. Although wood is often seen as a more environ- mentally friendly solution than many other materi- als, it is important to understand that its processing can have a significant impact on the environment. In order to maximize the use of wood, and in par- ticular reclaimed wood before incineration, many sectors are developing new technologies and prod- ucts with the support of LCA. The most important sector is construction, where the goal of sustain- able buildings can be achieved with timber struc- tures. In addition to timber construction, LCA also supports innovation research in wood-based mate- rials, energy, chemistry, pharmaceuticals and other sectors. ZAHVALA ACKNOWLEDGEMENT Raziskavo je finančno podprla Javna agencija za raziskovalno dejavnost Republike Slovenije (ARRS), v okviru programa Les in lignocelulozni kompoziti (P4-0015). VIRI REFERENCES Andersen, J. H., Rasmussen, N. L., & Ryberg, M. W. (2022). Com- parative life cycle assessment of cross laminated timber bu- ilding and concrete building with special focus on biogenic carbon. Energy and Buildings, 254, 111604. DOI: https://doi. org/10.1016/J.ENBUILD.2021.111604 Aryapratama, R., & Pauliuk, S. (2022). 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DOI: https://doi. org/10.1016/J.BIORTECH.2022.128281 5 Les/Wood, Vol. 71, No. 2, December 2022 Vol. 71, No. 2, 5-24 DOI: https://doi.org/10.26614/les-wood.2022.v71n02a04 WOOD IDENTIFICATION IN OBJECTS OF THE BAMBUTI PEOPLE FROM THE CONGO IN THE COLLECTION OF THE SLOVENE ETHNOGRAPHIC MUSEUM IDENTIFIKACIJA LESA PREDMETOV LJUDSTVA BAMBUTI IZ KONGA V ZBIRKI SLOVENSKEGA ETNOGRAFSKEGA MUZEJA Katarina Čufar 1 , Hans Beeckman 2 , Marko Frelih 3 , Luka Krže 1 , Wannes Hubau 2,4 , Maks Merela 1* UDK članka: UDK 630*811:630*176.1 Received / Prispelo: 15.11.2022 Original scientific article / Izvirni znanstveni članek Accepted / Sprejeto: 1.12.2022 . Abstract / Izvleč ek Abstract: The African collection of the Slovene Ethnographic Museum (SEM) in Ljubljana, Slovenia, holds objects of everyday life from the Bambuti people from the Ituri forest, in the northeastern part of the Democratic Republic of the Congo. The items were collected by the anthropologist Paul Joachim Schebesta, possibly during his expeditions around 1930. The objects containing wood were selected for wood identification by using microscopic wood identification, with the help of the InsideWood database and reference samples from the xylarium of the Royal Museum for Central Africa in Tervuren, Belgium. The investigated musical instrument, a wooden zither, was made of wood of Musanga cecropioides, the handle of the shield of Alstonia sp., the dagger and sheath of Autranella congolensis or another high density species of Sapotaceae, and the crossbow of Nauclea diderichii (bow) and Xylopia sp. (stock). Wood identification helped us to gain additional information on the origin, knowledge of wood, and time of the collection of objects in the Congo. Keywords: museum objects, wood identification, Musanga cecropioides, Alstonia, Autranella congolensis, Nauclea diderichii, Xylopia, Africa Izvleček: Afriška zbirka Slovenskega etnografskega muzeja (SEM) v Ljubljani hrani predmete iz vsakdanjega življenja ljudstva Bambuti iz gozda Ituri, na severovzhodu Demokratične republike Kongo. Predmete je zbral antropolog Paul Joachim Schebesta med svojimi odpravami verjetno okoli leta 1930. Predmeti, ki so vsebovali adultni les, so bili izbrani za raziskavo in mikroskopsko identifikacijo lesa s podporo platforme InsideWood ter referenčne zbirke lesa Kraljevega muzeja za Srednjo Afriko v Tervurnu v Belgiji. Raziskano glasbilo (lesene citre) je bilo izdelano iz lesa vrste Musanga cecropioides, ročaj ščita iz vrste Alstonia sp., nožnica in bodalo iz Autranella congolensis ali sorodne vrste z visoko gostoto iz družine Sapotaceae, samostrel pa iz Nauclea diderichii (lok) in Xylopia sp. (ročaj). Identifikacija lesa je ponudila dodatne informacije o izvoru, poznavanju lesa in času zbiranja predmetov v Kongu. Ključne besede: muzejski predmeti, identifikacija lesa, Musanga cecropioides, Alstonia, Autranella congolensis, Nauclea diderichii, Xylopia, Afrika 1 INTRODUCTION 1 UVOD The Slovene Ethnographic Museum (SEM) in Ljubljana holds an African collection with objects collected by the anthropologist Paul Joachim Sche- besta. They were possibly collected during his ex- peditions in 1929 and 1930 when he visited the Ituri rainforest on the Congo River and lived among the central African Pygmy people and explored their culture (Frelih et al., 2017). 1 University of Ljubljana, Biotechnical Faculty, Department of Wood Science and Technology, Jamnikarjeva 101, 1000 Ljubljana, Slovenia 2 Royal Museum for Central Africa, Laboratory for Wood Biology, Leuvensesteenweg 13, B-3080 Tervuren, Belgium 3 Slovene Ethnographic Museum, Metelkova ulica 2, 1000 Ljubljana, Slovenia 4 Ghent University, Faculty of Bioscience Engineering, Coupure Links 653, B-9000 Gent, Belgium * e-mail: maks.merela@bf.uni-lj.si 6 Les/Wood, Vol. 71, No. 2, December 2022 Čufar, K., Beeckman, H., Frelih, M., Krže, L., Hubau, W., & Merela, M.: Identifikacija lesa predmetov ljudstva Bambuti iz Konga v zbirki slovenskega etnografskega muzeja Paul Joachim Schebesta (Šebesta) was born in 1887 in Groß Peterwitz, Upper Silesia, at that time in the Austro-Hungarian Empire. During his studies in Mödling, near Vienna, he was dedicated to philosophy, theology, linguistics and ethnogra- phy. Under the influence of his professor, Wilhelm Schmidt, he developed a passion for studying the origin of religions which was later the main reason for his expeditions and extensive field research in Africa and Asia (Gütl, 2010). For this purpose, he searched for peoples who lived in remote, hard to reach areas and who were not yet affected by ex- ternal influences from other cultures. Schebesta undertook several research expedi- tions in the Congo (Figure 1). He was most attract- ed by the Bambuti (Mbuti) people in the rainforest on the Ituri catchment. In his first two expeditions in 1929 and 1930, he visited the Ituri rainforest, where the Pygmies had moved under pressure from other tribes (Schebesta, 1932). He was con- sidered to be the first European who managed to live among the shy rainforest people for a signifi- cant period of time, and learned about their way of living, customs and traditions, which in some ways would be considered prehistoric in Europe (Frelih et al., 2017). The culture, which in the first half of 20 th century was already in danger of becoming ex- tinct, was important for exploration of the cultural history of mankind due to its ancientness. The Pygmies from the Ituri rainforest in the Congo Basin seemed to have had a simple mate- rial culture, but they had impressive knowledge of flora, fauna and survival in the rainforest habitat. During his expeditions, Schebesta systematical- ly documented and published what he observed (e.g., Schebesta, 1957). He also collected photo- graphs, many of which are publicly available at the Bildarchiv Austria (2022) (Figure 1). He also system- atically collected a selection of objects related to life of the investigated cultures, and presented his research through numerous lectures to the scientif- ic community, students, and general public all over Europe (Frelih et al., 2017). Schebesta’s private collection, acquired dur- ing his fieldwork in the Congo, contained several thousands of objects, which he brought home to Mödling near Vienna. He later gradually gave or sold objects to museums in Brussels, Prague, and Vienna. However, it is less well known that a part of Schebesta’s African collection is also kept in the Slo- vene Ethnographic Museum. Most likely it arrived there in October 1933, when Schebesta held a number of lectures in Ljubljana and other locations in Slovenia. He most likely donated the collection to Figure 1. Photos from the archive of Paul Joachim Schebesta in the Bildarchiv Austria (2022): (a) Bambuti Pygmies in the village of Kero, with Schebesta surrounded by men (#10818394); (b) Bandaka Pygmies, specifically the headmen with his daughter, with the shield resembling the one investigated in this study (#12348274); (c) Nkundo Pygmies, with two men and weapons, including daggers like the ones in this study (#12452720) Slika 1. Fotografije iz arhiva Paula Joachima Schebeste, ki ji hrani Bildarchiv Austria (2022): (a) Bambutiji v vasi Kero–Schebesta obkrožen z moškimi (#10818394), (b) ljudstvo Bandaka–poglavar s hčerjo–ščit je podoben tistemu, ki je bil raziskan v tej študiji (#12348274), (c) ljudstvo Nkundo–dva moška z orožjem, vključno z bodalom, podobnim bodalu v tej študiji (#12452720). 7 Les/Wood, Vol. 71, No. 2, December 2022 Čufar, K., Beeckman, H., Frelih, M., Krže, L., Hubau, W., & Merela, M.: Wood identification in objects of Bambuti people from the Congo in the collection of the Slovene ethnographic museum Professor Lambert Ehrlich, who lived and worked in Ljubljana. The existing sources also do not reveal when Ehrlich transferred the collection to the Slo- vene Ethnographic Museum, since two dates are mentioned – 1940 and 1941 – and whether he sold or donated the collection (Frelih et al., 2017). Due to these facts, it is extremely likely that the collec- tion originates from the two expeditions Schebesta made to the Congo in 1929 and 1930. Schebesta’s collection at the Slovene Ethno- graphic Museum consists of 96 objects. Although it is not large, it contains a diversity of systematically collected objects, providing a basic presentation of the principal activities in the everyday life and ma- terial culture of different Bambuti groups native to the Ituri rainforest, Congo. The collection was not extensively researched or published until 2017, i.e. 130 years after Schebesta’s birth and 50 years after his death, when the Slovene Ethnographic Muse- um and the Slovene Museum of Christianity pre- pared an exhibition and publication entitled Baba wa Bambuti, the name Schebesta was given by the natives on the Ituri River (Frelih et al., 2017). In ad- dition to objects from Schebesta’s collection, an ex- ample of a wooden crossbow from the second half of the 19 th century is also included in this research. The crossbow is from the Congo, and nothing is known about the collector. The objects examined in this collection are mainly made of plant and animal material, and only few seem to be made of wood, which has not been investigated so far. In this study we thus focused on a few selected objects to perform wood research and identification. Our aim was to find out if such research can help answer various questions related to origin and history of the objects, and to explore how such information can help the museum cura- tors. Figure 2. Some of the ob- jects from the collection of Pavel Schebesta in the Slovene Ethnographic Museum (SEM) in Lju- bljana (from Frelih et al., 2017). Slika 2. Nekaj predmetov iz zbirke Pavla Schebeste, Slovenskega etnografske- ga muzeja (SEM) v Ljublja- ni (iz Frelih et al., 2017). 8 Les/Wood, Vol. 71, No. 2, December 2022 Čufar, K., Beeckman, H., Frelih, M., Krže, L., Hubau, W., & Merela, M.: Identifikacija lesa predmetov ljudstva Bambuti iz Konga v zbirki slovenskega etnografskega muzeja 2 MATERIALS AND METHODS 2 MATERIAL IN METODE 2.1 SELECTION OF MUSEUM OBJECTS 2.1 IZBOR MUZEJSKIH OBJEKTOV In the depository of the Slovene Ethnographic Museum (SEM) in Ljubljana we inspected a list of objects from Schebesta’s collection and selected ones that were presumably made of adult wood. The selected objects were a musical instrument (wooden zither), a shield, a dagger with sheath, and a crossbow consisting of bow and stock (Fig- ure 2, Table 1). Each of the objects was carefully in- spected by the museum curator, conserver-restorer and wood specialist in order to define the optimal location for sampling for wood identification. For sampling we developed a minimally de- structive method which allowed us to take small samples of wood to prepare thin microscopic slides (Koren, 2017). The wood samples were taken under the supervision of a museum curator and conserver on the least exposed and if possible hidden parts of the objects. For this purpose we used a special small drilling tool, an oscillating saw, and a surgical knife (Figure 3). The locations for wood sampling were carefully selected for each of the items, de- pending on its form and size. The samples con- tained enough wood tissue to produce cross-, ra- dial- and tangential sections for microscopic wood identification. 2.2 SAMPLE PREPARATION 2.2 PRIPRAVA VZORCEV After sampling, the wood was softened in a mixture of distilled water, glycerol and ethanol (in a ratio of 1:1:1) for about one week. Afterwards, the samples were observed under a magnifying glass and oriented to define the anatomical planes for cutting cross-, radial- and tangential sections with the help of a Leica SM2000R sliding microtome equipped with steel knives. The thickness of the sections was 10-20 μm. In one case the sample was taken with a surgical knife (Figure 3) and was em- bedded in paraffin; in this case 9 µm thick sections were cut with a Leica RM 2245 rotary microtome. Finally, the sections were stained with a water mix- ture of safranin and astra blue (i.e., 40 mg safranin and 150 mg astra blue in 100 ml demineralized wa- ter and 2 ml acetic acid) for at least 20 min, then washed, gradually dehydrated in ethanol (50, 70 and 100%) and finally mounted in Euparal accord- ing to the standard procedure (e.g., Prislan et al., 2022). In this way, we produced one permanent slide for each of the objects or their parts, if they were made of more than one wood species. Table 1. The investigated objects and their description from the catalogue (Frelih et al., 2017). Preglednica 1. Preučevani objekti in njihov opis iz kataloga (Frelih et al., 2017). Museum code Muzejska koda Name Ime Description Opis EM 2953 Wooden zither Musical instrument – a wooden zither with twelve plant-fibre strings (originally 15 strings). Lesene citre Glasbeni instrument – lesene citre z 12 strunami iz rastlinskih vlaken (prvotno 15 strun). EM 2866 Shield Shield made of interwoven thin sticks and plant fibres with a carved handle plate, made of a single piece of wood and fixed to two vertical parallel sticks. Ščit Ščit iz prepletenih tankih palic in rastlinskih vlaken z izrezljanim ročajem, izdelanim iz enega kosa lesa in pritrjenim na dve navpični vzporedni palici. EM 2864 Dagger and sheath (scabbard) Dagger with wooden hilt and iron blade, in a wooden sheath with an attached leather belt. Bodalo in nožnica Bodalo z lesenim ročajem in železnim rezilom v leseni nožnici s pritrjenim usnjenim pasom. EM 2675 Crossbow Not in the catalogue/unknown collector from 19 th century. Samostrel Ni v katalogu/ neznan zbiralec iz 19. stoletja. 9 Les/Wood, Vol. 71, No. 2, December 2022 Čufar, K., Beeckman, H., Frelih, M., Krže, L., Hubau, W., & Merela, M.: Wood identification in objects of Bambuti people from the Congo in the collection of the Slovene ethnographic museum 2.3 WOOD IDENTIFICATION 2.3 IDENTIFIKACIJA LESA Microscopic wood identification was per- formed by observing the sections under a Nikon Eclipse E800 light microscope equipped with a Nikon DS-Fil digital camera and using the NIS Ele- ments BR 3.0 image analysis computer program to capture the images. We examined the sections and recorded the observed features using the IAWA list of microscopic features for hardwood identification (IAWA committee, 1989) and InsideWood database (Wheeler, 2011; InsideWood, 2022). Afterwards the combinations of features were compared with reference data from the InsideWood database and xylarium of the Royal Museum of Central Africa, Tervuren, Belgium. 3 RESULTS AND DISCUSSION 3 REZULTATI IN RAZPRAVA 3.1 WOODEN ZITHER 3.1 LESENE CITRE The musical instrument, a wooden zither (EM2953), was made of wood of low density. The body was about 70 cm long, 20 cm wide, and 2 cm thick, and the wood working was rough. The instru- ment contained twelve plant-fibre strings where- as the body had 15 incisions at each end, where the strings were attached (Figure 4). Two wooden sticks, about 2 cm thick, positioned between the strings and the body, were used for tensioning the strings. They were not fixed, so their position could be changed to achieve the desired tone. Based on its wood structure (Figure 5) the wood of the body was identified as Musanga cecro- pioides R. Br., Urticaceae, with the most frequently used common names being African corkwood or parasolier (InsideWood, 2022). The wood is diffuse porous with indistinct or absent growth ring boundaries and large vessels (tang. diameter ≥ 200 µm), thin walled fibres, par- atracheal axial parenchyma (scanty, vasicentric), heterogeneous rays (body ray cells procumbent with 1-4 rows of upright and / or square marginal cells), 1-3 cells wide with sheath cells and prismatic crystals. The species Musanga cecropioides grows in tropical Africa (PlantUse Musanga, 2022). Its wood is of low commercial importance and is not avail- able on international markets. It has low density wood, with an air dry density of 190–370 kg/m³. The colour of the wood is basically white, some- times with a pinkish tinge when freshly cut, turning to pale yellow or pale brown upon exposure. Heart- wood cannot be distinctly demarcated from the sapwood. The wood is nondurable, class 5 (CEN, 2016), as reported by Wagenführ and Wagenführ (2022). The wood belongs to one of the lightest ones in the central African forests. It is easy to cut and work. It is occasionally locally used for light inte- rior constructions, partitions, doors, fences, roof rafters, stools, beds, musical instruments, toys, Figure 3. Collection of small samples for microscopic slides: (a) small drilling tool, (b) dimensions of wood sample, (c) collection of wooden splinter with a surgical knife. Slika 3. Odvzem majhnih vzorcev za mikroskopske preparate: (a) majhno vrtalno orodje, (b) dimenzija le- senega vzorca, (c) odvzem lesene trske s kirurškim skalpelom. 10 Les/Wood, Vol. 71, No. 2, December 2022 Čufar, K., Beeckman, H., Frelih, M., Krže, L., Hubau, W., & Merela, M.: Identifikacija lesa predmetov ljudstva Bambuti iz Konga v zbirki slovenskega etnografskega muzeja walking sticks, paddles, trays, baskets, and as a cork substitute to make floats for fishing nets and small canoes. It is suitable for sporting goods, box- es, crates, carvings, veneer, plywood, hardboard, particle board and wood-wool. The wood is tradi- tionally used to produce thin split boards. It can po- tentially be used as industrial insulation. The boles were traditionally hollowed out to make containers for liquids and small canoes, and to produce carved objects. Figure 4. Wooden zither (length about 70 cm): (a) entire instrument, (b, c) details, and (d) location of wood sampling. Slika 4. Lesene citre (dolžine približno 70 cm): (a) celoten instrument, (b, c) podrobnosti ter (d) mesto odvzema vzorca lesa. 11 Les/Wood, Vol. 71, No. 2, December 2022 Čufar, K., Beeckman, H., Frelih, M., Krže, L., Hubau, W., & Merela, M.: Wood identification in objects of Bambuti people from the Congo in the collection of the Slovene ethnographic museum Musanga cecropioides is an outspoken pioneer species, often growing on clear cuts or in disturbed areas in wetter forests and on small scale cano- py-gaps, in regions with a mean annual temperature of 25–30°C and annual rainfall of 1300–2500 mm or more. The trees are generally characterized by quick growth, and are often found around villages and along roads. The species usually occurs below 800 m altitude, and in the Democratic Republic of Congo occasionally up to 1200 m (PlantUse Musan- ga, 2022). 3.2 THE SHIELD 3.2 ŠČIT The shield is labelled EM2866 and is made of different types of plant material. The base of the shield is formed by two sticks, which support the handle and the front part (mask) of the shield, which is artificially made of intertwined plant ma- terial. The central sticks are positioned along the shield, which is about 140 cm long (Figure 6), and provide a quality construction solution to improve the strength of the shield. The central sticks are Figure 5. Wood from the body of the wooden zither Musanga cecro- pioides with: (a) cross-, (b) tangen- tial-, and (c, d) ra- dial sections. Scale bars–100 µm. Slika 5. Les glavne- ga dela citer vrste Musanga cecropi- oides: (a) prečni, (b) tangencialni in (c, d) radialni pre- rez. Merilne daljice -100 µm. 12 Les/Wood, Vol. 71, No. 2, December 2022 Čufar, K., Beeckman, H., Frelih, M., Krže, L., Hubau, W., & Merela, M.: Identifikacija lesa predmetov ljudstva Bambuti iz Konga v zbirki slovenskega etnografskega muzeja connected by the handle and a skilfully made piece of interlaced plant material, which also serves for decoration. The handle is made of one piece of wood and is attached to the shield with a rope. The object is very light, and therefore was possibly used as a ceremonial shield. The wood of the shield handle was identified as Alstonia boonei De Wild. or A. congensis Engl., Apocynaceae with the vernacular names cheese- wood, ekouk or emien. The two species cannot not be distinguished based on wood structure (Inside- Wood, 2022; PlantUse Alstonia…, 2022). The wood is diffuse porous (Figure 7). Interves- sel pits are vestured and vessel-ray pits similar to intervessel pits in size and shape appear through- out the ray cell, the fibres are very thin-walled, axial parenchyma is reticulate, aligned in narrow bands or lines up to three cells wide. Rays are one to three cells wide and heterogeneous, with procumbent body cells and one to four rows of upright and / or square marginal cells. Laticifers are present but they are very small (with a similar size to the ray cells) and difficult to distinguish in the ray on tan- gential section (Figure 7b) (InsideWood, 2022). The heartwood is creamy white and indistinct- ly demarcated from the up to 20 cm wide sapwood. The wood darkens upon exposure to light. The grain is straight, occasionally wavy, and the texture moderately coarse. Growth rings are indistinct or absent. The wood has a disagreeable smell when green. It is lightweight, and the mean air-dry den- sity is 360 kg/m³. The wood is not durable and be- longs to durability class 5 (CEN, 2016). The wood is easy to saw, although the presence of latex may cause clogging of sawblades (CIRAD Alstonia, 2022; PlantUse Alstonia boonei, 2022; PlantUse Alstonia congensis, 2022). The wood of Alstonia boonei, called alstonia in international trade, is used for light constructions, light carpentry, open boats, moulding, furniture, in- terior joinery, implements, boxes, crates, matches, pencils, sculptures, and for veneer and plywood. It is locally popular for the production of household implements because of its good working properties and stability. It is easy to carve therefore it is also used for masks, sculptures and so on. The genus Alstonia comprises about 40 species with a pantropical distribution. Only two, Alstonia congensis and Alstonia boonei, are indigenous in Figure 6. The shield (length 140 cm): (a) front and (b, c) back view with the wooden handle. Slika 6. Ščit (dolžine 140 cm): (a) sprednji in (b, c) zadnji del z lesenim ročajem. 13 Les/Wood, Vol. 71, No. 2, December 2022 Čufar, K., Beeckman, H., Frelih, M., Krže, L., Hubau, W., & Merela, M.: Wood identification in objects of Bambuti people from the Congo in the collection of the Slovene ethnographic museum Africa. The wood of the two species is closely re- lated, and the two species are not discriminated in use. 3.3 DAGGER AND SHEATH 3.3 BODALO IN NOŽNICA The dagger with a wooden hilt, iron blade and a wooden sheath (EM2864) is a decorated ob- ject which could be produced and used for ritual purposes (Figure 8). Macroscopic inspection of the wood revealed that the hilt and sheath were made of the same wood species. The sheath is ap- proximately 35 cm long and is made of one piece of wood. It contains a precisely made opening which fits the blade of the dagger. A leather belt is attached through a hole and enables fitting the objects around the waist. The sheath is made with exceptional precision, which is evident from the wood processing, decoration and precise dimen- sions. The dagger with an about 30 cm long blade and over 10 cm long wooden hilt is also precisely made. The blade is decorated with cuts. The pom- Figure 7. Wood of Alstonia sp. from the shield handle: (a) cross-, (b) tangen- tial-, and (c) radial sections, (d) vestured intervessel pits, (e) detail showing vessel ray pits. Scale bars–a, b, c, e–100 µm, d–50 µm. Slika 7. Les ročaja šči- ta vrste Alstonia sp.: (a) prečni, (b) tan- gencialni in (c) radi- alni prerez, (d) okra- šene intervaskularne piknje, (e) pogled, kjer so vidne piknje med trakom in tra- hejo. Merilne daljice: a, b, c, e–100 µm, d–50 µm. 14 Les/Wood, Vol. 71, No. 2, December 2022 Čufar, K., Beeckman, H., Frelih, M., Krže, L., Hubau, W., & Merela, M.: Identifikacija lesa predmetov ljudstva Bambuti iz Konga v zbirki slovenskega etnografskega muzeja mel of the hilt is decorated with bronze rivets. One of the photos taken by Paul Joachim Schebesta shows two warriors of the Nkundu people in full gear, including a dagger, similar to the one investi- gated in this study (Figure 1c). The wood of the dagger hilt and sheath was identified as similar to Autranella congolensis A. Chev., Sapotaceae, with the most common vernac- ular names being elang and mukulungu (Inside- Wood, 2022). This diffuse-porous wood species with small vessels (Figure 9) has the following features: in- tervessel pits alternate, vessel-ray pits with much reduced borders to apparently simple pits rounded or angular, non-septate fibres present, fibres very thick-walled, axial parenchyma diffuse and diffuse in aggregates, axial parenchyma in narrow bands or lines up to three cells wide (mainly one cell wide), eight (five to eight) cells per parenchyma strand, ray width one to three cells, body ray cells procum- bent with mostly two to four rows of upright and / or square marginal cells, body ray cells procumbent with over four rows of upright and / or square mar- ginal cells (InsideWood, 2022). The wood has a high air-dry density (940 kg/ m ³ ). The heartwood is red brown and can be clearly distinguished from sapwood. The wood is very du- rable, class 5 (CEN, 2016). The wood is used for hy- draulic works, sleepers, heavy constructions, poles, heavy carpentry, flooring, stairs, sliced veneer, ex- terior panelling, and cooperage (CIRAD, Autranella congolensis, 2022). Autranella congolensis occurs in primary ev- ergreen rainforest, and is usually scattered, rarely abundant. Natural regeneration is currently poor. The growth of trees is slow and very long cutting cy- cles are probably required for sustainable harvest- ing. This makes Autranella congolensis a tree with few prospects for timber production, and attention should concentrate on its protection. Figure 8. Dagger with a wooden hilt and iron blade, and a wooden sheath with leather belt. Slika 8. Bodalo z lesenim ročajem in železnim rezi- lom ter leseno nožnico z usnjenim pasom. 15 Les/Wood, Vol. 71, No. 2, December 2022 Čufar, K., Beeckman, H., Frelih, M., Krže, L., Hubau, W., & Merela, M.: Wood identification in objects of Bambuti people from the Congo in the collection of the Slovene ethnographic museum 3.4 CROSS-BOW 3.4 SAMOSTREL The cross-bow (label EM 2675) is entirely made of wood and consists of two parts, a bow and han- dle (stock) (Figure 10). Based on the macroscopic examination, we supposed that the two parts must be made of two different wood species. The han- dle is about 120 cm long. Approximately two-thirds of its length is the trigger mechanism. From the structural point of view, the trigger mechanism is remarkably well made (Frelih et al., 2017). The han- dle is evenly split into two parts, all the way to the chisel for the bow string. The bow is about 80 cm long. It is made of one piece of bent wood. As the distance between both ends of the bow and the incisions for the string are short, it is necessary to use a wood of exceptional toughness to produce an effective weapon. The wood of the bow is identified as Nauclea diderrichii Merr., Rubiaceae, with the most com- mon vernacular names being bilinga and opepe. Figure 9. Wood from the dagger hilt and sheath, Autranella congolensis, Sapotac- eae with (a, b) cross-, (c, d) tangential-, and (e, f) radial sections. Scale bars–100 µm. Slika 9. Les ročaja in nožnice bodala iz lesa vrste Autranella con- golensis, Sapotaceae: (a, b) prečni, (c, d) tangencialni in (e, f) radialni prerez. Me- rilne daljice–100 µm. 16 Les/Wood, Vol. 71, No. 2, December 2022 Čufar, K., Beeckman, H., Frelih, M., Krže, L., Hubau, W., & Merela, M.: Identifikacija lesa predmetov ljudstva Bambuti iz Konga v zbirki slovenskega etnografskega muzeja This wood species is diffuse porous and has very small, isolated vessels (Figure 11). Other IAWA features of the species are: vessel-ray pits with dis- tinct borders that are similar to intervessel pits in size and shape throughout the ray cell, bordered pits in fibres can be seen in radial and also in tan- gential fibre walls, axial parenchyma is diffuse, diffuse-in-aggregates or scanty paratracheal, ray width one to three cells. Rays have multiseriate portion(s) as wide as uniseriate ones, body ray cells are procumbent with mostly two to four or over four rows of upright and / or square marginal cells orperforated ray cells, and the ray-body cells are procumbent. Nauclea diderichii is on the list of commercial hardwoods (Richter and Dallwitz, 2002; CIRAD, Nauclea diderrichii, 2022). Its heartwood is golden yellow or orange yellow, clearly demarcated from the sapwood. Its wood is hard, dense (average air- dry density 760 kg/m ³ ) and very durable, in dura- bility class 1 (CEN, 2016), and it is resistant to fungi and insects (CIRAD, Nauclea diderrichii, 2022). It is used in joinery, flooring and marine constructions. Figure 10. Crossbow – different views showing: (b) the bow made of Nauclea diderichii and (s) the stock made of Xylopia sp.; arrows show iron belts for reinforcement. Slika 10. Samostrel, različni pogledi: (b) lok iz lesa Naeuclea diderichii in (s) ročaj iz lesa vrste Xylopia sp.; puščice kažejo železne trakove za ojačitev. 17 Les/Wood, Vol. 71, No. 2, December 2022 Čufar, K., Beeckman, H., Frelih, M., Krže, L., Hubau, W., & Merela, M.: Wood identification in objects of Bambuti people from the Congo in the collection of the Slovene ethnographic museum It is used for railway sleepers, heavy carpen- try, poles, heavy constructions, hydraulic works, flooring, cabinetwork, sliced veneer, ship building, planking and panelling (CIRAD, Nauclea diderrichii, 2022). It was as a rule also used for numerous eth- nographic objects. Nauclea diderichii is a tree species natural in subtropical or tropical moist lowland forests. It is threatened by habitat loss (IUCN, 2022). The wood of the stock belongs to the genus Xy- lopia, Annonaceae and we could not identify it to a species level. The wood is diffuse-porous with radial diameters of vessels of ca. 200 µm. Vessel-ray pits have distinct borders and are similar to intervessel pits in size and shape throughout the ray cell. Fibres have simple to minutely bordered pits. Fibres are thick-walled. Axial parenchyma is in narrow bands or lines up to three cells wide, reticulate. Ray width is one to three, all ray cells are procumbent. Densi- ty is medium, 400-750 kg/m ³ (InsideWood, 2022). Wood structure with a great proportion of thick-walled fibres and a homogenous struc- Figure 11. Wood from the bow of the cross- bow (Nauclea dideri- chii): (a, b) cross-, (c) tangential- and (d, e) radial sections; (d) detail showing ves- sel ray pits and pits in fibres. Scale bars– 100 µm. Slika 11. Les iz loka samostrela (Nau- clea diderichii): (a, b) prečni, (c) tangenci- alni in (d, e) radialni prerez; (d) detajl s piknjami med trakom in trahejo in piknjami vlaken. Merilne dalji- ce–100 µm. 18 Les/Wood, Vol. 71, No. 2, December 2022 Čufar, K., Beeckman, H., Frelih, M., Krže, L., Hubau, W., & Merela, M.: Identifikacija lesa predmetov ljudstva Bambuti iz Konga v zbirki slovenskega etnografskega muzeja ture with uniformly distributed axial parenchyma strands indicate that the wood may have a high density and favourable mechanical properties. Up to twenty different species of Xylopia grow in the Congo. Although the trees can be large enough to be used as timber, the wood is relatively unknown in international markets, but has some commercial potential if available in sig- nificant stocks. The wood is moderately hard and heavy, moderately durable to durable, of durabili- ty class 2-3 (CEN, 2016), and has good machining characteristics, as shown for Xylopia hypolampsa from the forests of the Central African Republic (Možina & Torelli, 1977; Torelli, 1983; Čufar, 1984). Wood of Xylopia sp. has some decorative value for applications such as parquet flooring and furniture (Dahms, 1999). One species growing in the Ituri for- est that is a candidate for the botanical identity of the crossbow is Xylopia chrysophyllum. Figure 12. Wood from the stock of the crossbow (Xylopia sp.): (a, b) cross-, (c) tangential-, and (d) radial sections. Scale bars–100 µm. Slika 12. Les ročaja samostrela (Xylopia sp.): (a, b) prečni, (c) tangencialni in (d) ra- dialni prerez. Merilne daljice–100 µm. 19 Les/Wood, Vol. 71, No. 2, December 2022 Čufar, K., Beeckman, H., Frelih, M., Krže, L., Hubau, W., & Merela, M.: Wood identification in objects of Bambuti people from the Congo in the collection of the Slovene ethnographic museum 3.5 POTENTIAL OF WOOD RESEARCH IN MUSEUM OBJECTS 3.5 POTENCIAL RAZISKAV LESA MUZEJSKIH OBJEKTOV The collection of 96 objects from the SEM con- tained only few objects which were made of wood of larger trees. Nearly all of these objects have in- ventory labels (Figure 2), featuring their names and how the natives possibly used them. Interestingly, the labels show two, three, or even four different inventory numbers, written with different pens. Schebesta probably inventoried and numbered the objects in the field, but they were later renum- bered in Mödling, and perhaps finally once more in Ljubljana (Frelih et al., 2017). The pictures from Schebesta’s archive stored in the picture archive Bildarchiv Austria (2022) additionally help us to un- derstand the use of the objects (Figure 1). The wood of the objects has never been stud- ied, so its potential to shed light on the wood spe- cies used by the Bambuti and to provide additional information on the origin and history of the objects could not be exploited. In four studied objects, we identified five dif- ferent species (Table 2) from different families, all of which grow in the tropical rainforest of Ituri in the Congo. The species are mostly unknown in in- ternational markets. They have different densities and other characteristics, and have been effectively used to make various objects, confirming that their characteristics are well known to the local people, the Bambuti. The choice of species confirms the origin of the wood from the Congo, more precisely from the dense tropical rainforest of Ituri. Since the species are not known internationally and have never been used in Slovenia, their identification could only be done by making high quality microscopic sections for observation under a microscope. This required destructive sampling, which in our case was less in- vasive because the process was optimized and very small wood particles were taken. Despite high qual- ity microscopic sections, identification could not be done without the InsideWood collection and col- laboration with the Royal Museum of Central Africa and its xylarium, with collections of wood samples and microscopic slides. The objects in the Ljubljana collection resem- ble numerous objects in the Weltmuseum Wien in Vienna. Archival sources indicate that the objects in Vienna originate from the Congo region and come from Schebesta’s expeditions in 1929-1930 and 1934-35 (Frelih et al., 2017). Our enquiries in Austria and Belgium have shown that systematic identification of the wood of ethnographic objects from the Schebesta collection has mostly not been carried out, as also observed for other African collections (e.g., Bontadi & Bern- Table 2. Wood taxa in the wooden objects from the museum collection and main information; *density of air-dry wood from the literature. Preglednica 2. Vrste lesa v lesenih predmetih iz muzejske zbirke in glavni podatki; *gostota zračno suhega lesa iz literature. Name and museum code Ime in muzejska koda Wood species Vrsta lesa Family Družina Density* Gostota* kg/m³ Wooden zither EM 2953 Lesene citre Musanga cecropioides Urticaceae 190–370 Shield (handle) EM 2866 Ščit (ročaj) Alstonia boonei Alstonia congensis Apocynaceae 360 Dagger and sheath EM2864 Bodalo in nožnica Autranella congolensis Sapotaceae 940 Crossbow EM 2675 Samostrel -bow / lok Neuclea diderichii Rubiaceae 760 -stock / ročaj Xylopia sp. Annonaceae possibly >750 20 Les/Wood, Vol. 71, No. 2, December 2022 Čufar, K., Beeckman, H., Frelih, M., Krže, L., Hubau, W., & Merela, M.: Identifikacija lesa predmetov ljudstva Bambuti iz Konga v zbirki slovenskega etnografskega muzeja abei, 2016; Petrovčič, 2016). However, at least the botanical identity of a few objects from the mate- rial culture of the Bambuti is known, thanks to the research of Tanno (1981), who analysed their plant use with particular reference to their material cul- ture and the use of wild vegetables as food. Since the Bambuti had to move their camps regularly, their baggage was rather light. The men carried only the hunting equipment and axes, while the women carried the household items in baskets. Other items were shared with other families and used by the group as a whole, or made locally when needed (Tanno, 1981). The number of items in the material culture of the Bambuti is rather limited compared to that seen with sedentary cultures, but they testify to a close connection with nature and natural resources, and to an exceptional knowledge of forest products, including the wood characteris- tics of various trees, which were used for a wide range of applications. 4 CONCLUSIONS 4 SKLEPI Although the Congolese indigenous objects collected by anthropologist Paul Joachim Schebes- ta are stored in several museums throughout Eu- rope, and his missions to the Congo are well doc- umented, the identification of wood in the objects has generally not been undertaken. This study shows that five different wood species – namely Musanga cecropioides, Alstonia boonei or Alstonia congensis, Autranella congolen- sis, Neuclea diderichii, and Xylopia sp. – were iden- tified in four studied objects. They all grow in the tropical rainforest of Ituri, Congo, and are largely unknown in international markets. Their identifi- cation could therefore only be achieved by making high quality microscopic sections and carrying out microscopic wood identification with the help of the InsideWood database and the wood collection of the Royal Museum of Central Africa. Wood re- search has thus helped us to obtain additional in- formation on the origin and history of objects rep- resentative of the material culture of the Bambuti. The selection of wood species confirms their excel- lent knowledge of the wood properties of species growing in the Ituri rainforest habitat. 5 SUMMARY 5 POVZETEK Slovenski etnografski muzej (SEM) v Ljublja- ni hrani zbirko predmetov, ki jih je zbral antropo- log Paul Joachim Schebesta na svojih odpravah v Kongu, verjetno v letih 1929 in 1930, ko je obiskal deževni gozd Ituri ob reki Kongo in živel med sre- dnjeafriškimi Pigmejci ter raziskoval njihovo kulturo (Frelih et al., 2017). Sistematično zbrani predmeti so povezani z življenjem raziskovanih kultur, ki jih je predstavil v številnih publikacijah in predavanjih po Evropi (Frelih et al., 2017). Veliko zbranih pred- metov je postopoma podaril ali prodal muzejem v Bruslju, Pragi in na Dunaju, del Schebestove afriške zbirke pa hrani tudi SEM v Ljubljani. Najverjetneje je tja prišla oktobra 1933, ko je imel Schebesta pre- davanja v Ljubljani in drugih krajih v Sloveniji. V raz- iskavo smo vključili tudi leseni samostrel iz Konga, ki ga je muzej pridobil v drugi polovici 19. stoletja. Kdo je muzeju izročil samostrel, ni znano. Schebestova zbirka v SEM obsega 96 predme- tov, ki omogočajo osnovno predstavitev glavnih dejavnosti v življenju in materialni kulturi različnih skupin ljudstva Bambut, ki živijo v deževnem gozdu Ituri. Predmeti so večinoma izdelani iz rastlinske- ga in živalskega materiala. Le nekaj predmetov je izdelanih iz lesa večjih dreves. Les doslej še ni bil raziskan. V tej študiji smo se osredotočili na izbor in raziskavo lesenih predmetov, kjer smo opravili identifikacijo lesa. Zanimalo nas je tudi, ali lahko raziskave lesa prispevajo k razjasnitvi vprašanj, po- vezanih z izvorom in zgodovino predmetov, ter kako lahko pomagajo muzejskim kustosom. V depoju SEM smo pregledali nabor predmetov in izbrali tiste, ki so domnevno izdelani iz adultnega lesa dreves. Izbrali smo štiri predmete: leseno glas- bilo–citre, ščit z lesenim ročajem, bodalo z nožnico in samostrel, sestavljen iz loka in ročaja (pregledni- ca 1, slike 2, 4, 6, 8, 10). Vsak predmet so skrbno pregledali muzejski kustos, konservator–restavra- tor in strokovnjaki za les, da bi določili optimalno mesto za odvzem vzorcev za identifikacijo lesa. Za odvzem lesa smo razvili metodo, ki je omo- gočila odvzem majhnih vzorcev, mikroizvrtkov ali trsk, za pripravo tankih mikroskopskih preparatov. Vzorce lesa smo pod nadzorom muzejskega kustosa in konservatorja odvzeli na čim bolj skritih delih predmetov. V ta namen smo uporabili posebno 21 Les/Wood, Vol. 71, No. 2, December 2022 Čufar, K., Beeckman, H., Frelih, M., Krže, L., Hubau, W., & Merela, M.: Wood identification in objects of Bambuti people from the Congo in the collection of the Slovene ethnographic museum majhno orodje za vrtanje, vrtalnik in nihajno žago ter kirurški nož (slika 3). Pripravljeni so bili trajni mikroskopski preparati treh anatomskih ravnin, mikroskopska identifikacija lesa pa je bila opravljena s pomočjo platforme In- side Wood ter referenčnih vzorcev lesa in prepara- tov iz zbirke Kraljevega muzeja za Srednjo Afriko v Tervurnu v Belgiji. Po odvzemu vzorcev smo les nekaj dni meh- čali v mešanici destilirane vode, glicerina in etano- la. Nato smo vzorce opazovali pod povečevalnim steklom in jih orientirali ter določili smer rezanja za pridobitev prečnih, radialnih in tangencialnih rezin. Rezine debeline 10–20 μm smo odrezali s pomočjo drsnega mikrotoma Leica SM2000R. V enem prime- ru je bil vzorec odvzet s kirurškim nožem (slika 3) in vklopljen v parafin (Prislan et al., 2022). V tem primeru so bili z rotacijskim mikrotomom Leica RM 2245 narezani 9 μm debeli preparati, ki smo jih obarvali z vodno raztopino barvil safranin in astra modro, izprali, dehidrirali in nazadnje vklopili v Eu- paral po standardnem postopku. Na ta način smo izdelali po en trajni preparat (prečni, radialni in tan- gencialni prerez) za vsak predmet ali njegov del, če je bil narejen iz več kot ene vrste lesa. Za mikroskopsko identifikacijo lesa smo upo- rabili svetlobni mikroskop Nikon Eclipse E800, opremljen z digitalnim fotoaparatom Nikon DS-Fil in računalniškim programom za analizo slik NIS Elements BR 3.0. Preparate smo pregledali in po- iskali znake za mikroskopsko identifikacijo lesa (IAWA Committee, 1989) ter opravili identifikacijo s pomočjo računalniškega ključa podatkovne zbirke Inside Wood (Wheeler, 2011; Inside Wood, 2022). Identifikacijo lesa smo opravili na osnovi kombi- nacije anatomskih znakov. Po oceni rodu ali lesne vrste smo opravili natančne primerjave z referenč- nimi podatki in slikami iz zbirke Inside Wood in z referenčnim materialom iz ksilarija Kraljevega mu- zeja Srednje Afrike v Tervurnu. Tako smo potrdili ali izboljšali predhodno identifikacijo, opravljeno v okviru diplomske naloge (Koren, 2017). Raziskali smo les štirih predmetov. To so glas- bilo–lesene citre, ščit z lesenim ročajem, bodalo in nožnica ter samostrel, izdelan iz dveh sestavljivih delov, loka in ročaja. Predmeti so prikazani na slikah 1, 2, 4, 6, 8 in 10. Raziskano glasbilo–lesene citre–je bilo izdela- no iz lesa vrste Musanga cecropioides, ki ima go- stoto zračno suhega lesa 190–370 kg/m³, uspeva v tropski Afriki in ni trgovsko pomemben. Lažji ščit, narejen iz rastlinskih materialov, ki je imel verjetno obredni pomen, je imel ročaj iz lesa iz rodu Alstonia (Alstonia boonei ali Alstonia con- gensis). Rod Alstonia vsebuje okoli 40 vrst, od tega samo omenjeni vrsti uspevata v Afriki. Vrsti Alstonia boonei in Alstonia congensis sta zelo sorodni, nju- nega lesa pa ni mogoče zanesljivo razlikovati. Les gostote okoli 360 kg/m³ je biološko neodporen in je priljubljen za lažje konstrukcije. Bodalo z lesenim ročajem in leseno nožnico je iz lesa vrste Autranella congolensis ali sorodne vrste z visoko gostoto iz družine Sapotaceae. Gosto- ta zračno suhega lesa je okoli 940 kg/m ³ . Les ima obarvano jedrovino in je odporen proti biološkim škodljivcem. Samostrel ima lok, narejen iz vrste Nauclea di- derichii, ki je na seznamu komercialnih lesnih vrst. Les ima visoko gostoto 760 kg/m ³ in zlato do oran- žno rumeno jedrovino. Je trd in trden ter odporen proti biološkim škodljivcem. Ročaj samostrela je narejen iz lesa ene od vrst iz rodu Xylopia. V Demo- kratični republiki Kongo uspeva okoli 20 vrst iz rodu Xylopia. Ena od vrst, ki uspeva v gozdu Ituri, je Xylo- pia chrysophyllum. Les vrst Xylopia je v splošnem srednje gostote 400–750 kg/m ³ in je malo znan na mednarodnih trgih. Raziskovalci z Oddelka za lesar- stvo so podrobneje raziskali les vrste Xylopia hypo- lampsa iz Centralnoafriške republike (CAR) (Moži- na & Torelli; Torelli, 1983; Čufar, 1984), ki so poleg anatomije ter fizikalno mehanskih lastnosti raziskali tudi njegovo obdelavnost. Centralnoafriški Pigmejci so les vrste Xylopia hypolampsa zaradi izjemne žila- vosti uporabljali za izdelavo strelskih lokov in samo- strelov (Torelli, osebna komunikacija). Za vsako od ugotovljenih lesnih vrst so prika- zane slike treh anatomskih prerezov s tipičnimi mi- kroskopskimi znaki, ključnimi za identifikacijo lesa (slike 5, 7, 9, 11, 12). Vsaka od vrst je tudi opisana z vidika lastnosti in rabe lesa (preglednica 2). Ugotovljene vrste lesa večinoma niso predmet mednarodne trgovine in niso široko znane. Njihova identifikacija ne bi bila mogoča brez baze podatkov za identifikacijo lesa listavcev Inside Wood in pri- merjav z lesom in preparati iz zbirke Kraljevega mu- zeja za Srednjo Afriko v Tervurnu. Čeprav so predmeti, ki jih je zbral antropolog Paul Joachim Schebesta, shranjeni v več muzejih 22 Les/Wood, Vol. 71, No. 2, December 2022 Čufar, K., Beeckman, H., Frelih, M., Krže, L., Hubau, W., & Merela, M.: Identifikacija lesa predmetov ljudstva Bambuti iz Konga v zbirki slovenskega etnografskega muzeja po Evropi in so njegove misije v Kongu dobro do- kumentirane, identifikacija lesa predmetov doslej v glavnem še nikjer ni bila opravljena. Ta študija kaže, da je bilo v štirih preučevanih predmetih mogoče identificiranih pet različnih vrst lesa, ki vse rastejo v tropskem deževnem gozdu Ituri v Kongu in so na mednarodnih trgih precej nezna- ne. Raziskave lesa so tako pomagale potrditi izvor lesa in nudijo dodatne podatke o domnevni zgodo- vini predmetov, ki predstavljajo materialno kulturo ljudstva Bambuti. Izbor lesnih vrst potrjuje, da so domačini odlično poznali drevesne vrste in lastnosti lesa vrst, ki uspevajo v deževnem gozdu Ituri. ACKNOWLEDGEMENTS ZAHVALE This study was supported by the Slovenian Research Agency ARRS, program P4-0015. Interna- tional collaboration was supported by COST Actions FP1106, STReESS, and FP 1302 Wood Musick. We thank Gregor Kos for great support during wood sampling, as well as students Luka Koren and Do- men Petrovčič for their help in the initial stages of the work. 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InsideWood–a web resource for hardwood anatomy. IAWA Journal, 32 (2), 199–211. Wagenführ, R., & Wagenführ, A. (2022). Holzatlas. 7. überarbeitete und ergänzte Auflage, Carl Hanser Verlag München. 24 Les/Wood, Vol. 71, No. 2, December 2022 45 Les/Wood, Vol. 71, No. 2, December 2022 Vol. 71, No. 2, 45-56 DOI: https://doi.org/10.26614/les-wood.2022.v71n02a05 1 Univerza v Ljubljani, Biotehniška fakulteta, Oddelek za lesarstvo, Jamnikarjeva 101, 1000 Ljubljana, Slovenija * e-pošta: matjaz.dremel@gmail.com VPLIV NARAVNEGA STARANJA NA IZBRANE FIZIKALNE IN MEHANSKE LASTNOSTI KONSTRUKCIJSKEGA LESA EFFECTS OF NATURAL AGEING ON SELECTED PHYSICAL AND MECHANICAL PROPERTIES OF STRUCTURAL TIMBER Matjaž Dremelj 1* , Aleš Straže 1 UDK 630*814.1:812 Prispelo / Received: 4.11.2022 Pregledni znanstveni članek / Review scientific article Sprejeto / Accepted: 30.11.2022 . Izvleček / Abstract Izvleček: Les je po poseku in uporabi za konstrukcije izpostavljen staranju, ki je med drugim odvisno od pogojev izpostavitve. V času življenjske dobe oz. uporabe je les izpostavljen fotodegradaciji, biodegradaciji, površinskim in notranjim strukturnim spremembam in staranju, ki se kaže v spremembi barve, kemijske sestave, higroskopnosti, dimenzijske stabilnosti ter nekaterih mehanskih lastnosti. Podajamo pregled literature, s posebnim poudarkom vpliva pogojev izpostavitve na spremembe lastnosti lesa ter pregled kemijskih in mikrostrukturnih sprememb ter sprememb barve, sorpcijskih in mehanskih lastnosti. V splošnem so spremembe zaradi staranja lahko zelo počasne in jih je težko ovrednotiti tudi zaradi velike naravne variabilnosti lesnih lastnosti. Poznavanje sprememb v naravno staranem lesu je ključno pri ohranjanju kulturne dediščine. Pri načrtovanju vzdrževanja, konzerviranja ter pri obnovi kulturne dediščine, z upoštevanjem staranja konstrukcijskega lesa bolje razumemo strukturne spremembe, vlažnostna in napetostno-deformacijska stanja lesenih konstrukcij ter interakcije z drugimi gradbenimi materiali. Ključne besede: les, staranje, barva, higroskopnost, dimenzijska stabilnost, sorpcija, mehanske lastnosti Abstract: After harvesting, wood in constructions undergoes an ageing process that depends, among other things, on exposure conditions. During its lifetime wood is subject to photodegradation, biodegradation, surface and internal structural changes, and ageing, which is reflected in changes in colour, chemical composition, hygroscopicity, dimensional stability, and mechanical properties. We present a literature review, with particular emphasis on the influence of exposure conditions on changes in wood properties, chemical and microstructural changes, and changes in colour, sorption, and mechanical properties. In general, ageing-related changes can be very slow and difficult to detect, in part because of the wide natural variability in wood properties. Knowledge of the changes in naturally aged wood is critical for preserving cultural heritage, evaluating the safety of wood structures, and planning their conservation. When planning maintenance, conservation, and restoration of cultural heritage, we can better understand the structural changes, moisture and stress deformation states of wood structures, and interactions with other building materials if we consider the ageing of structural wood. Keywords: wood, ageing, colour, hygroscopicity, dimensional stability, sorption, mechanical properties 1 UVOD 1 INTRODUCTION Les je kot naraven polimerni kompozit med življenjsko dobo oz. uporabo izpostavljen fotode- gradaciji, biodegradaciji, površinskim in notranjim strukturnim spremembam in tudi staranju (Kránitz et al., 2016; Turkulin & Živković, 2018). Naravno staranje lesa se večinoma razlaga kot počasen pro- ces blage termične oksidacije, t.j. v območju narav- nega temperaturnega nihanja, kjer je kisik prisoten v zraku ali raztopljen v vodi, in hidrolize zaradi vseb- nosti kislin ter vezane vode v lesu (Stamm, 1956; Matsuo et al., 2011). V vlažnih razmerah se lahko s staranjem v lesu v zelo nizkih koncentracijah tvori- jo nekatere organske kisline, kot sta 4-metilgluku- ronska in galaktoronska kislina, a le velika količina 46 Les/Wood, Vol. 71, No. 2, December 2022 Dremelj, M., & Straže, A.: Effects of natural ageing on selected physical and mechanical properties of structural timber kislin v dovolj dolgem obdobju lahko povzroči tudi razgradnjo celuloze in izgubo mase ter trdnostnih lastnosti (Sundqvist, 2006; Kránitz et al., 2016). Kot posledice staranja lesa so pogosto vidne majhne spremembe v barvi, blage kemijske spremembe, zlasti nižanje deleža hemiceluloz, spremenjena higroskopnost in dimenzijska stabilnost ter tudi ne- katere mehanske lastnosti (Straže et al., 2018). Za- radi higroskopne narave lesa prihaja v njem do na- petosti zaradi nihanja vlažnosti, kljub temu, da je les viskoelastični material (Matsuo et al., 2011; Kránitz, 2014). Poznavanje lastnosti naravno staranega lesa je ključno pri ohranjanju kulturne dediščine, saj les poleg kamna in opeke predstavlja pomemben del konstrukcij v zgodovinskih objektih. Lastnosti sta- ranega lesa so ključne pri razumevanju obnašanja in ocenjevanju varnosti konstrukcij kot tudi pri na- črtovanju sanacij starih stavb, poškodovanih zaradi naravnih ujm, kot je na primer bil potres v Zagrebu marca 2020 (Turkulin, osebna komunikacija). 2 SPREMEMBE LASTNOSTI LESA MED NA- RAVNIM STARANJEM 2 CHANGES IN WOOD PROPERTIES DURING NATURAL AGEING 2.1 POGOJI IZPOSTAVITVE IN POSLEDICE 2.1 EXPOSURE CONDITIONS AND CONSEQUENC- ES Čeprav ima les v drevesu različno kambijevo starost, odvisno od tega, v katerem letu je nastala posamezna branika, velja, da se staranje lesa zač- ne s posekom drevesa. Spremembe v lesu potekajo zelo počasi in so odvisne od okoljskih mikroklimat- skih razmer. V vročem, suhem puščavskem podne- Slika 1. Del stare strešne konstrukcije cerkve sv. Barbare v vasi Ravnik pri Hotedršici. Figure 1. Part of the old wooden roof structure of the St. Barbara church located in the village of Ravnik near Hotedrščica. 47 Les/Wood, Vol. 71, No. 2, December 2022 Dremelj, M., & Straže, A.: Vpliv naravnega staranja na izbrane fizikalne in mehanske lastnosti konstrukcijskega lesa bju se leseni predmeti in tekstil na osnovi rastlinskih vlaken lahko ohranijo celo več tisočletij, medtem ko njihovo razgradnjo pospešujejo razmere, v katerih uspevajo mikroorganizmi. Razlikujemo dva tipa raz- mer, v katerih potekajo procesi staranja: anaerobne in aerobne. Les se lahko zelo dolgo ohrani v anaerobnih razmerah (brez prisotnosti zraka), ki veljajo za le- sene predmete, potopljene v vodo ali zakopane v zemljo brez prisotnosti kisika. V takih razmerah se lahko nahajajo temelji stavb, stebri, ladje ipd. Razmere, v katerih je les, ki je potopljen v vodi ali zakopan v zemlji, sprožijo zelo počasen proces fo- silizacije, pri katerem se kemijske sestavine celične stene v več tisoč letih pretvorijo v visoko kondenzi- rane spojine (koalifikacija) ali se nadomestijo z mi- nerali (silicifikacija). V to kategorijo spada subfosilni les debel močvirskih hrastov, ki se v mokrem okolju lahko ohranijo več tisoč let (Pearson et al., 2014; Rede et al., 2022) in les različnih predmetov z Lju- bljanskega barja, kot je les s koliščarskih naselbin, najstarejše leseno kolo na svetu ter različni deblaki (Čufar & Velušček, 2012). Različne komponente lesa so izpostavljene različnim vrstam razgradnje in pretvorbe (Fengel, 1991). Praviloma spremembe najprej doživijo he- miceluloze in celuloza, zato v lesu narašča delež lignina (npr. Čufar et al., 2008). Ker je v omenjenih razmerah kisik redko popolnoma odsoten, je les po- gosto podvržen počasnemu razkroju bakterij (Kim & Singh, 2000; Singh et al., 2019; Balzano et al., 2022). V tem pregledu nas zanima predvsem les kon- strukcij stavb, ki se stara v aerobnih razmerah (Slika 1). Kadar so razmere ugodne (ugodna temperatura, odsotnost UV sevanja ter vode oz. zamakanja), se zdi, da je učinek staranja na strukturo lesa minima- len, tudi pri arheološkem lesu iz piramid, starem do 4400 let (Van Zyl et al., 1973). V nadaljevanju podajamo pregled sprememb lesa, vgrajenega v stavbah. 2.2 KEMIJSKE SPREMEMBE 2.2 CHEMICAL CHANGES Pri naravnem staranju lesa se najpogosteje z vidika osnovnih lesnih komponent omenjajo spre- membe na hemicelulozah, najmanj stabilni kom- ponenti, ki ima zaradi svoje manj urejene struk- ture večjo topnost in se lažje hidrolizira (Hedges, 1989; Fengel, 1991). V večini dosedanjih raziskav so zaznali zmanjšanje deleža hemiceluloz zara- di hidrolize (Chowdhury et al., 1967; Pishik et al., 1971; Erhardt et al., 1996; Yonenobu & Tsuchikawa, 2003; Tsuchikawa et al., 2005; Popescu et al., 2007; Ganne-Chédeville et al., 2012; Kránitz, 2014; Kačík et al., 2014; Hudson-McAulay, 2016; Belec, 2017). Holz (1981) pa pri vzorcih manjše starosti, 60-180 let, ni zaznal značilnih razlik v primerjavi z recen- tnim lesom. Hudson-McAulay (2016) v svoji razi- skavi navaja, da se z zmanjšanjem deleža acetilnih skupin v polimerih hemiceluloz zaradi te kemijske reakcije sprošča ocetna kislina. Celuloza je bolj odporna na staranje kot hemi- celuloze, saj ima višjo stopnjo kristaliničnosti in vi- soko stopnjo medmolekularne povezanosti znotraj fibril, kaže nizko topnost v večini topil in razmero- ma močno odpornost na hidrolizo (Hedges, 1989; Fengel, 1991). V nekaterih raziskavah so zazna- li zmanjšanje deleža celuloze (Chowdhury et al., 1967; Pishik et al., 1971; Tomassetti et al., 1990; Campanella et al., 1991; Belec, 2017), v drugih pa niso zaznali bistvenih sprememb v količini celulo- ze (Holz, 1981; Erhardt et al., 1996; Kránitz, 2014). Yonenobu in Tsuchikawa (2003) sta zaznala degra- dacijo v amorfnih regijah celuloze. Nekatere raziskave podajajo spremembe za holocelulozo, ki vključuje celulozo in hemiceluloze. Tako Kohara in Okamoto (1955) in drugi viri poro- čajo o zmanjšanem deležu holoceluloze, Van Zyl in sodelavci (1973) poročajo o povečanem deležu holoceluloze, Kačík in sodelavci (2014) pa o rahlem zmanjšanju. Lignin se zdi med glavnimi gradniki celične ste- ne najbolj odporen na staranje. Etrske vezi in vezi med ogljikovimi atomi naredijo lignin odporen pro- ti hidrolizi, vendar pa je dovzeten za oksidacijske procese (Kránitz, 2014). Oksidacija lignina skupaj z drugimi reakcijami lahko privede do degradacije makromolekul lignina na manjše enote (Borgin et al., 1975a). Od gradnikov celične stene spada lignin med najbolj občutljive na ultravijolično svetlobo (UV). Nekatere raziskave ugotavljajo, da pride s sta- ranjem do povečanja deleža lignina (Narayanamur- ti et al., 1961; Tomassetti et al., 1990; Campanella et al., 1991), druge pa poročajo o zmanjšanju (Pi- shik et al., 1971; Van Zyl et al., 1973; Borgin, et al. 1975a; Ganne-Chédeville et al., 2012; Kačík et al., 2014). Več avtorjev (Kránitz, 2014; Hudson-McAu- 48 Les/Wood, Vol. 71, No. 2, December 2022 Dremelj, M., & Straže, A.: Effects of natural ageing on selected physical and mechanical properties of structural timber lay, 2016; Belec, 2017) ni zaznalo bistvenih spre- memb, je pa bila zaznana oksidacija lignina. Za pro- centualno povečanje deleža lignina v elementarni sestavi je verjetno odgovorna razgradnja hemicelu- loz in zmanjšanje njihovega deleža (Dremelj, 2018). Glede kristaliničnosti celuloze si raziskave niso tako enotne. Nekatere poročajo o povečanju stop- nje kristaliničnosti (Popescu et al., 2007; Saito et al., 2008; Gawron et al., 2012), druge o zmanjšanju (Borgin et al., 1975a; Erhardt et al., 1996; García Esteban et al., 2006; Kránitz, 2014), nekatere pa govorijo, da sprememb niso opazili (Yonenobu & Tsuchikawa, 2003; Inagaki et al., 2008). Kohara in Okamoto (1955) sta pri lesu japon- ske paciprese (Chamaecyparis obtusa, jap. hinoki) zaznala povečanje kristaliničnosti do starosti 100 let, nato pa pri starejših vzorcih zmanjšanje, med- tem ko je bilo pri lesu listavca zelkova (Zelkova serrata, jap. keyaki) opaženo stalno zmanjševanje stopnje kristaliničnosti. Kohara in Okamoto (1955), razlagata povečanje deleža kristaliničnosti z ustvar- janjem novih intermolekulskih vezi v amorfnih de- lih celuloznih mikrofibril. Fukada (1965) je prouče- val les Japonske ciprese (Cryptomeria japonica, jap. sugi), indeks kristaliničnosti celuloze je bil največji pri lesu starosti 350 let, nato pa je indeks padal do starosti lesa 1400 let. Navaja, da so dobre akustič- ne lastnosti povezane s samo kristaliničnostjo, in so najboljše pri največji kristaliničnosti celuloze. Kačík in sodelavci (2014), Kohara in Okamoto (1955), Pishik in sodelavci (1971) poročajo o pove- čanju deleža ekstraktivov, Ganne-Chédeville in so- delavci (2012) pa o njihovi degradaciji. Več virov (Pishik et al., 1971; Van Zyl et al., 1973; Borgin et al., 1975a; Tomassetti et al., 1990) poroča o povečanem deležu pepela pri staranem lesu, pri raziskavah, ki sta jih opravila Holz (1981) in Kránitz (2014), pa se delež pepela ni bistveno spre- menil. Kránitz (2014) navaja zmanjšanje količine ekstraktivov pri lesu, starem 150 let ali manj, kot posledico izhlapevanja hlapnih komponent. Pri sta- rejšem lesu ista avtorica ponovno povečanje deleža ekstraktivov pojasnjuje kot posledico povečanja de- leža oksidacijskih produktov lignina in hemiceluloz. 2.3 MIKROSTRUKTURNE SPREMEMBE 2.3 MICROSTRUCTURAL CHANGES Več virov navaja spremembe v mikrostrukturi naravno staranega lesa. Na makroskopskem nivo- ju samih sprememb pogosto ni možno opaziti, šele z mikroskopskimi metodami, kot je mikroskopija v svetlem polju, elektronska mikroskopija z uporabo vrstičnega (SEM) in transmisijskega elektronskega mikroskopa (TEM) daje vpogled v samo mikrostruk- turo in spremembe v njej, ki so posledica staranja lesa. Več raziskav poroča o delaminaciji S3 sloja celične stene (Narayanamurti et al., 1958; Froide- vaux et al., 2012; Kránitz, 2014), prav tako tudi o delaminaciji srednje lamele (Kollmann & Schmidt, 1962; Borgin et al., 1975b; Froidevaux et al., 2012; Kránitz, 2014) ter pojavu radialnih razpok v sekun- darni steni (Kollmann & Schmidt, 1962; Froidevaux et al., 2012; Kránitz, 2014). Chowdhury in sodelavci (1967) pa poročajo tudi o helikalnih razpokah v ce- ličnih stenah vlaken. Brez poznavanja natančne zgodovine lesa ni mogoče zagotoviti, da so napake posledica samo staranja. Priprava vzorca, zunanje ali notranje na- petosti lahko prav tako vplivajo na mikrostrukturo, vendar se napake večinoma pojavljajo na območjih, kjer je več hemiceluloz, pektinskih materialov in lig- nina (Borgin et al., 1975b). Kojiro in sodelavci (2008) so raziskovali poroz- nost lesa in poroznost celične stene. Število por v celični steni, manjših od 0,6 nm, se je zmanjšalo s starostjo lesa. S starostjo lesa je prišlo tudi do pro- storninskega zmanjšanja por na maso lesa. 2.4 BARVA LESA 2.4 WOOD COLOUR V procesu staranja lesa je najbolj opazna spre- memba barve površine. Najbolj pride do izraza pri lesu, ki je izpostavljen direktnim sončnim žarkom. Izpostavljenost lesa sončnim žarkom v kombinaciji z vodo pripelje do barvnih sprememb na površini lesa, kjer voda lahko tudi spere produkte fotode- gradacije lignina, ki nastanejo zaradi UV sevanja in les posivi. Prav tako pa lahko nastanejo razpoke na površini in med samimi celicami in znotraj celične stene. Fotodegradacija pojasnjuje spremembo bar- ve na površini lesa, medtem ko sprememba barve lesa v notranjosti lesnih elementov ni natančno po- jasnjena. Obstaja le malo dosedanjih študij barvnih sprememb znotraj lesenih elementov. Matsuo in sodelavci (2011) v svoji raziskavi pojasnjujejo, da je sprememba barve med naravnim staranjem pred- vsem posledica počasnega in blagega procesa ter- 49 Les/Wood, Vol. 71, No. 2, December 2022 Dremelj, M., & Straže, A.: Vpliv naravnega staranja na izbrane fizikalne in mehanske lastnosti konstrukcijskega lesa mične oksidacije lesa. Do spremembe barve lesa pa lahko pride tudi zaradi spreminjanja deleža ekstrak- tivov in njihove kemijske strukture. Delež ekstrakti- vov se pri starem lesu povečuje kot posledica razpa- da strukturnih elementov lesa, oksidacije lignina in hemiceluloz (Kačík et al., 2014; Kránitz, 2014). Avtorji (Kohara, 1955; Matsuo et al., 2011; Kránitz, 2014; Dremelj, 2018) enotno opažajo temnenje barve in povečanje kromatičnosti barv- nega odtenka na zeleno-rdeči (+a) in rumeno-mod- ri (+b) osi s starostjo lesa (Slika 2). Kránitz (2014) večje razlike v barvi opaža pri iglavcih, manjše pa pri hrastovini. Sprememba barve lesa ni odvisna samo od okoljskih razmer, temveč tudi od vrste lesa in razlik v kemični sestavi med lesnimi vrstami (slika 2). Matsuo in sodelavci (2011) navajajo, da so barv- ne spremembe zaradi naravnega staranja in toplo- tne obdelave podobne. 2.5 HIGROSKOPSKE LASTNOSTI 2.5 HYGROSCOPIC PROPERTIES V različnih klimatskih razmerah les, ki je higroskopen material, vzpostavlja ravnovesno vla- žnost in s tem tudi svoje stabilne dimenzije. Dimen- zijsko stabilnost določajo sorpcijske lastnosti mate- rialov (Noack et al., 1973; Gorišek, 2009). Osnovni gradniki celične stene izkazujejo različne higroskop- ske lastnosti. Hemiceluloze so najbolj higroskopne, sledi celuloza, najmanj higroskopen pa je lignin. V zgodovinskih stavbah so pohištvo, leseni izdelki in konstrukcije izpostavljeni različnim nihajočim rela- tivnim zračnim vlažnostim (Gereke et al., 2011), to lahko povzroči velika dimenzijska nihanja lesa, kar pa lahko privede zaradi razlik v krčenju in/ali nab- rekanju lesa tudi do ireverzibilnih strukturnih po- škodb lesa (Hudson-McAulay, 2016). Kohara in Okamoto, (1955) sta poročala o zmanjšanju koeficienta nabrekanja, prav tako Dre- melj (2018) poroča tudi o zmanjšanju diferencialne- ga nabreka. Schulz in sodelavci (1984) pa pri smre- kovini starosti 300 let ugotavljajo nasprotno, da se koeficient nabrekanja (h) povečuje. Holz (1981) ni odkril bistvenih razlik v nabrekanju vzorcev smre- ke, stare 60–180 let, prav tako pri boru (Erhardt et al., 1996) niso mogli dokazati nobenih sprememb. Kránitz (2014), ki je proučevala les smreke, jelke in hrasta, ni zaznala bistvenih razlik pri sorpciji in rav- novesni vlažnosti v primerjavi z recentnim lesom. Opravljenih je bilo več študij sorpcijskih izoterm in ravnovesne vlažnosti starega lesa. Buck (1952) navaja, da čeprav so sorpcijske izoterme pokazale rahlo zmanjšanje ravnovesne vlažnosti pri starih vzorcih, razlik ni bilo mogoče jasno ugotoviti zara- di majhnega števila vzorcev in možnih napak med meritvami. Več avtorjev je zaznalo nižje sorpcijske izoterme za staran les in s tem nižje ravnovesne vla- žnosti (Kohara & Okamoto, 1955; Burmester, 1967; Lang, 2004; Inagaki et al., 2008; Kawai et al., 2008; Kurtoglu, 1983; Dremelj, 2018). Dremelj (2018) na stari hrastovini pri preverjanju velikosti histerezne zanke in adsorpcijsko-desorpcijskega razmerja ni potrdil bistvenih razlik (Slika 3). Esteban in sode- lavci (2006) ugotavljajo na vzorcu juvenilnega lesa rdečega bora večjo histerezno zanko in višjo ravno- vesno vlažnost na vsakem posamičnem intervalu dinamičnega sorpcijskega testiranja. Razlika je lah- ko posledica nižje stopnje kristaliničnosti celuloze, opažene pri staranih vzorcih. Nekatere raziskave pa omenjajo tudi ožanje sorpcijske histerezne zanke starega in recentnega lesa, če se les za več tednov izpostavi vlažnejši klimi. To povezujejo s sprošča- njem napetosti v materialu, oz. celičnem matriksu. Staranje lesa s tem podobno kot toplotno obdelavo lesa razlagajo kot delno reverzibilen proces (Oba- taya, 2017). Na testih absorpcije oz. navzemanja te- koče vode, ki jih je izvedel Narayanamurti s sodelav- Slika 2. Videz tipičnih hrastovih preizkušancev od najmlajše do najstarejše starostne skupine (100–600 let) (po Straže et al., 2018). Figure 2. Appearance of typical oak specimens sorted from the youngest to the oldest (age groups 100 – 600 years) (after Straže et al., 2018). 50 Les/Wood, Vol. 71, No. 2, December 2022 Dremelj, M., & Straže, A.: Effects of natural ageing on selected physical and mechanical properties of structural timber ci (1958) na 1500 let starih vzorcih tikovine, so prav tako pokazali zmanjšanje higroskopnosti, pri čemer je skupna količina adsorbirane vode znatno nižja pri starih vzorcih. Če povzamemo predhodne ugotovitve, lahko domnevamo, da se ravnovesna vlažnost s stara- njem lesa zmanjšuje, vendar vzrok sprememb v ve- čini primerov ostaja neznan. V procesu staranja lesa pride do razgradnje higroskopnih hemiceluloz, prav tako se spremeni stopnja kristaliničnosti celuloze, ki se s staranjem lesa povečuje (Kohara & Okamo- to, 1955; Gawron et al., 2012), vendar si pretekle raziskave niso enotne. To je pojasnjeno z ustvarja- njem novih intermolekularnih vezi med celuloznimi verigami, ki nastajajo v amorfnih področjih (Koha- ra et al., 1955). Povečanje stopnje kristaliničnosti celuloze povzroči manjše nabrekanje lesa, manjšo higroskopnost, višjo gostoto, višjo trdoto in trdnost (Gawron et al., 2012) 2.6 MEHANSKE LASTNOSTI 2.6 MECHANICAL PROPERTIES Večina študij mehanskega obnašanja naravno staranega lesa obravnava le nekaj izbranih lastnosti. Tlačna trdnost je bila razmeroma pogosto raziskana predvsem za oceno stanja staranih lesenih kon- strukcij. Meritve na konstrukcijah iz lesa iglavcev kot so smreka, jelka in rdeči bor, v večini raziskav ne kažejo sprememb v tlačni trdnosti vsaj do starosti 400 let (Ehlbeck & Görlacher, 1988, 1993; Deppe & Rühl, 1993; Nier, 1994; Weimar, 2000; Lang, 2004; Lissner & Rüg, 2004; Kránitz, 2014). Narayanamurti in sodelavci (1961) na listavcih paduk (Pterocarpus soyauxii) in tik (Tectona grandis), starosti 500 let, prav tako niso zaznali sprememb v tlačni trdnosti. Medtem ko so (Schulz et al., 1984) na 300 let stari smrekovini, (Attar-Hassan, 1976) na 140 let stari bo- rovini, (Kohara, 1955) na japonski pacipresi (hinoki) do starosti 100 let in Narayanamurti in sodelavci (1958) na 1500 let stari tikovini zaznali povečano tlačno trdnost v primerjavi z recentnim lesom. Hud- son-McAulay (2016) pa je zaznala na stari borovini veliko zmanjšanje tlačne trdnosti, podobno sta jo zaznala Kohara in Okamoto (1955) na lesu zelkove. Trdota staranega lesa kaže podobne težnje kot tlač- na trdnost (Kohara & Okamoto, 1955; Attar-Hassan, 1976; Kavčič, 2019). Določanje upogibne trdnosti in modula ela- stičnosti v vzdolžni smeri se pogosto ugotavlja tudi pri preiskavah staranega lesa. Več študij na lesu iglavcev in listavcev ni pokazalo razlik med upogib- no trdnostjo recentnega in staranega lesa, starega do 400 let (Ehlbeck & Görlacher, 1988, 1993; Rug & Seemann, 1989; Nier, 1994; Horie, 2002; Baron, 2009; Hudson-McAulay, 2016; Zupanc et al., 2021), oz. kažejo, da se trdnost staranega lesa lahko celo poveča (Schulz et al., 1984), pri lesu zelkove do sta- rosti 650 let, japonske paciprese nad starostjo 100 Slika 3. Vzorci hrasta, odvzeti iz starih konstrukcijskih elementov lesenih zgradb (a) in primer sorpcijske his- tereze adsorpcijsko-desorpcijskega eksperimenta za starostne skupine lesa 100, 300 in 500 let po poseku (b) (Straže et al., 2018). Figure 3. Oak wood samples from old structural elements of wooden buildings (a) and the sorption hys- teresis for the adsorption-desorption test for the age groups 100, 300 and 500 years after tree felling (b) (Straže et al., 2018). 51 Les/Wood, Vol. 71, No. 2, December 2022 Dremelj, M., & Straže, A.: Vpliv naravnega staranja na izbrane fizikalne in mehanske lastnosti konstrukcijskega lesa let in zelenega bora starosti do 140 let zmanjša (Ko- hara & Okamoto, 1955; Attar-Hassan, 1976). Zmanjšanje upogibnega statičnega modula elastičnosti so opazili pri starani smrekovini ter lesu zelenega bora, zelkove, paduka in kino (Kohara & Okamoto, 1955; Narayanamurti et al., 1961; Attar- Hassan, 1976; Lang, 2004), vendar so z ultrazvoč- nimi testi izmerili povečanje dinamičnega modula elastičnosti (Attar-Hassan, 1976; Kránitz, 2014). Pri starem rdečem boru niso bile ugotovljene nobene značilne spremembe modula elastičnos- ti (Erhardt et al., 1996). Pri smreki vrste jezoensis (Picea jezoensis), jelki vrste sachalinensis (Abies sa- chalinensis) in japonski pacipresi niso opazili pos- labšanja modula elastičnosti (Horie, 2002; Yokoya- ma et al., 2009). Poleg tega nekateri članki poročajo o povečanju elastičnega modula, kot npr. Kawai in sodelavci (2008) na vzorcih japonske paciprese, starih 500–1600 let, ter Noguchi s sodelavci (2011), ki obravnava 300 let star japonski rdeči bor (Pinus densiflora ). Poskusi na slednjem so razkrili tudi več- jo hitrost zvoka, manjše dušenje (nižji kot izgub) in večje razmerje med elastičnim in strižnim mo- dulom. Saito in sodelavci (2008) na vzorcih japon- skega rdečega bora poročajo o zmanjšanju modula elastičnosti, Kohara in Okamoto (1955) pa govorita o povečanju modula elastičnosti v prvih 100 letih, nato pa sledi zmanjšanje. Froidevaux in sodelavci (2012) so opravili mi- kro natezne teste v radialni smeri na 200–500 let starih primerkih smreke. Opazili so približno 25-od- stotno zmanjšanje trdnosti, vendar niso ugotovili razlik v modulu elastičnosti. Yokoyama in sodelavci (2009) so določili upogibno trdnost v radialni smeri za stare vzorce japonske paciprese, stare do 1580 let. Vrednosti za star les so bile bistveno nižje kot pri recentnih vzorcih. Raziskave natezne trdnosti so protislovne. Medtem ko poročajo o povečanju trdnosti 300 let starega smrekovega lesa (Schulz et al., 1984), se ta pri 140 let starem lesu zelenega bora v primerjavi z recentnim lesom zmanjša (Attar-Hassan, 1976). Zdi se, da se večina trdnostnih lastnosti lesa s staranjem spreminja precej počasi, da sprememb ni mogoče zaznati ali pa sploh ne nastanejo. Vendar je bilo ugotovljeno, da je obnašanje staranega lesa pri zlomu pogosto drugačno od obnašanja recentnega lesa. Les lahko s staranjem postane bolj krhek, kot so omenili Attar-Hassan (1976) in Kawai in sodelav- ci (2008). Številni avtorji poročajo o zmanjšanju ab- sorbirane energije ob preskusu udarne žilavosti pri staranem lesu (Kohara & Okamoto, 1955; Schulz et al., 1984; Weimar, 2000; Lang, 2004; Baron, 2009; Yokoyama et al., 2009). Vzorci, raziskani v teh študijah, predstavljajo predvsem les iglavcev, edina izjema je študija, ki sta jo opravila Kohara in Okamoto (1955), kjer obrav- navata tudi les zelkove, ki je listavec. Vsi preiskani vzorci lesa so služili v konstrukcijah 300–1600 let. Pregledi lomnih površin so razkrili večji delež krhkih lomov pri starem kot pri recentnem lesu (Weimar, 2000; Lang, 2004) ter več neravnih in kompleksnih lomnih površin na mikroskopski ravni (Ando et al., 2006). Pri smreki jezoensis (Picea jezoensis), jel- ki (Abies sachalinensis) z dobo uporabe 30–80 let niso opazili nobene razlike v udarni žilavosti (Horie, 2002). Erhardt in sodelavci (1996) ne poročajo o nobenih spremembah v porušitveni deformaciji in meji elastičnosti v več ponovitvah statičnega nate- znega obremenjevanja 300–400 let starih vzorcev rdečega bora. Kar zadeva strižno trdnost so se vrednosti sta- ranega zelenega bora s starostjo povečale, vrednos- ti lesa japonske paciprese in zelkove pa zmanjšale (Kohara & Okamoto, 1955; Attar-Hassan, 1976), na drugi strani pa ni bilo mogoče zaznati razlik med strižno trdnostjo 270 let starega japonskega rdeče- ga bora in recentnega lesa. Vendar je analiza akus- tične emisije med strižnimi testi pokazala večjo krh- kost staranega lesa. Ugotovljeno je bilo razmeroma dolgo in stabilno napredovanje mikrorazpok pred končnim zlomom v primerjavi z recentnim lesom, kjer mikrorazpok ni bilo, pri čemer so bile lomne površine videti bolj neravne in kompleksne na mi- kroskopski ravni. Prav tako se v primeru staranega lesa poleg loma znotraj celične stene pojavljajo tudi številni lomi med celicami, ki so nastali predvsem na obrobju pikenj (Ando et al., 2006). Avtor meni, da so mikrorazpoke že obstajale na robu pikenj pred samim lomljenjem. Froidevaux in sodelavci (2012) so raziskovali le- zenje in mehano-sorptivne deformacije smrekove- ga lesa, starega 200–500 let v radialni smeri. Glede viskoelastičnosti se zdi, da je recentni les nekoliko bolj viskozen kot staran les. Vendar pa so bili lomni parametri v plastičnem območju mehanskih obre- menitev pri staranem lesu močno poslabšani. Z vi- dika mehano-sorpcijskega obnašanja je ireverzibil- 52 Les/Wood, Vol. 71, No. 2, December 2022 Dremelj, M., & Straže, A.: Effects of natural ageing on selected physical and mechanical properties of structural timber na deformacija bistveno večja pri recentnih vzorcih, kar kaže na določeno degradacijo lesa, ki se pojavi z naravnim staranjem. 3 ZAKLJUČKI 3 CONCLUSIONS V preteklih študijah je bil uporabljen velik na- bor različnih metod za prepoznavanje sprememb, ki nastanejo v lesu pri naravnem staranju. Iz pre- teklih študij lahko sklepamo, da razgradnja zaradi staranja lesa najbolj prizadene hemiceluloze. Ce- luloza je nekoliko bolj odporna in je degradirana predvsem v amorfnem delu. Glede kristaliničnosti celuloze si raziskave niso tako enotne, nekatere po- ročajo o povečanju kristaliničnosti, druge o zmanj- šanju. Vsebnost pepela praviloma narašča z naraš- čanjem starosti lesa. Pri deležu lignina niso zaznali bistvenih sprememb v odvisnosti od starosti, ven- dar pa so v več raziskavah našli produkte oksidacije lignina. Dosedanje raziskave poročajo o mikrostruk- turnih spremembah, kjer so najpogosteje opažene poškodbe kot je delaminacija srednje lamele in S3 sloja ter radialne razpoke v sekundarnem sloju celičnih sten lesnih vlaken. Pri barvnih spremem- bah s staranjem avtorji enotno opažajo temnenje barve in povečanje kromatičnosti barvnega odten- ka na zeleno-rdeči (+a) in rumeno-modri (+b) osi. Ravnovesna vlažnost se s starostjo lesa praviloma zmanjšuje. Glede na rezultate mehanskih testov je mogoče ugotoviti v splošnem bolj krhko obnašanje staranega lesa z zmanjšano udarno žilavostjo (Kra- nitz et al., 2016). Zmanjša se lahko tudi trdnost v prečni ravnini, v vzdolžni smeri pa ni mogoče opazi- ti jasnega trenda glede trdnosti in togosti. Različne ugotovitve številnih študij so verjetno deloma pos- ledica v splošnem velike variabilnosti lesnih lastnos- ti, različnih mikroklimatskih pogojev izpostavitve, ki jim je les izpostavljen med dolgotrajno uporabo, in razliki v metodologiji raziskav. Zelo verjetno je, da se zaradi inherentnih strukturnih in kemijskih last- nosti lesne vrste tudi različno obnašajo v procesu staranja. 4 POVZETEK 4 SUMMARY Wood is a natural polymer composite, and over its lifetime its structures are subjected to pho- todegradation, biodegradation, structural changes of the surface and interior, and ageing (Straže et al., 2018). Natural ageing of wood is usually inter- preted as a slow process of mild thermal oxidation in the range of natural temperature fluctuations, where oxygen is dissolved in air or water, and hy- drolysis occurs due to the presence of acids and bound water in wood (Stamm, 1956; Matsuo et al., 2011). The consequences of ageing of wood can be seen in its properties, such as changes in colour and chemistry, altered hygroscopicity and dimensional stability, and changes in some mechanical proper- ties (Straže et al., 2018). The hygroscopic nature and variations of moisture content in the material, as well as the viscoelasticity of wood, cause inter- nal stresses (Matsuo et al., 2011; Kránitz, 2014). Knowledge of the properties of naturally aged wood is critical for its conservation, as wood forms an important part of the structures in cultural herit- age buildings. The properties of aged wood are also critical for evaluating the safety of structures. In this review article, we provide an overview of the literature, focusing on the influence of ex- posure conditions on changes in wood properties, and provide an overview of chemical and micro- structural changes, as well as changes in colour, hy- groscopic, and mechanical properties. A wide range of methods have been used in previous studies to determine the changes that occur during the natural ageing of wood. From previous studies, it can be concluded that the age-related degradation of wood mainly affects the hemicelluloses. Cellulose seems to be more resist- ant, and is more likely changed in its amorphous form. As for the crystallinity of cellulose, the re- ports in previous studies vary, with some reporting an increase in the degree of crystallinity and others a decrease. In general, the amount of extractives increases with the age of the wood. No significant age-related changes were found in lignin content, but lignin oxidation products were found in wood in several studies. Microstructural changes have been noted in earlier research, with the most commonly observed damage being delamination of the mid- dle lamella and S3 layer and radial cracks in the sec- ondary wall. In terms of colour changes with age- ing, various authors uniformly observe a decrease in colour lightness and an increase in chromaticity in the green-red (+a) and yellow-blue (+b) axes. 53 Les/Wood, Vol. 71, No. 2, December 2022 Dremelj, M., & Straže, A.: Vpliv naravnega staranja na izbrane fizikalne in mehanske lastnosti konstrukcijskega lesa Equilibrium moisture content generally decreases with age. According to the results of the mechan- ical tests, the aged wood is generally more brittle with a consistently lower impact bending strength (Kranitz et al., 2016). Strength perpendicular to the grain may also decrease. However, no clear trend can be seen with respect to strength and stiffness in the longitudinal direction. Knowledge of the changes in naturally aged wood is essential for preserving cultural heritage and evaluating the safety of wooden constructions. 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DOI: https://doi. org/10.1366/000370203322554635 Zupanc Lipovec, E., Fajdiga, G., & Humar, M. (2021). Primerjava mehanskih lastnosti recentnega in 400 let starega lesa evrop- skega macesna. Les/Wood, 70(2), 31-40. DOI: https://doi. org/10.26614/les-wood.2021.v70n02a01 56 Les/Wood, Vol. 71, No. 2, December 2022 67 Les/Wood, Vol. 71, No. 2, December 2022 PROF. DR. PRIMOŽ OVEN – PREJEMNIK ZLATE PLAKETE UNIVERZE V LJUBLJANI PROF. DR. PRIMOŽ OVEN – RECIPIENT OF THE GOLDEN PLAQUE OF THE UNIVERSITY OF LJUBLJANA Marko Petrič 1* , Ida Poljanšek 1** . Izvleček / Abstract Izvleček: Na Univerzi v Ljubljani (UL) je med 28. novembrom in 2. decembrom 2022 potekal Teden univerze in tudi letos, ob 103. rojstnem dnevu univerze, so bili predstavljeni najodličnejši raziskovalni dosežki, podeljeni častni nazivi, plakete, nagrade in priznanja vsem, ki so pripomogli, da je Univerza v Ljubljani iz leta v leto boljša. Na Oddelku za lesarstvo Biotehniške fakultete UL smo zelo ponosni, da je na slavnostni seji Senata Univerze v Ljubljani 29. 11. 2022 Zlato plaketo prejel tudi naš sodelavec, prof. dr. Primož Oven, vodja Katedre za kemijo lesa in druge lignocelulozne materiale. Prof. Oven je mednarodno uveljavljen raziskovalec in pedagog na področju proučevanja zvez med funkcijami, strukturami, kemizmom in lastnostmi lesa, biorafinacije ter valorizacije lesne biomase s poudarkom na pridobivanju in uporabi nanoceluloze in lesnih ekstraktivov. V akademskem in gospodarskem okolju promovira trajnostno izrabo lesa v krožnem biogospodarstvu in skrbi za ugled UL doma in v tujini. Ključne besede: Univerza v Ljubljani, Zlata plaketa Univerze, kemija lesa Abstract: From November 28 to December 2, 2022, the University Week was held at the University of Ljubljana (UL). As in previous years, and on this, the occasion of the 103 rd anniversary of the University, the most outstanding research achievements were presented, and honorary degrees, plaques, awards and recognitions were given to all those who have contributed to make the University of Ljubljana better year after year. At the Department of Wood Science and Technology of the Biotechnical Faculty of the University of Ljubljana, we are very proud that at the ceremonial meeting of the Senate of the University of Ljubljana on November 29, 2022, our colleague, the Head of the Chair of Wood Chemistry and Other Lignocellulosic Materials, Prof. Dr. Primož Oven, was also awarded the Golden Plaque. Prof. Oven is an internationally recognised researcher and lecturer in the field of research on the relationships between functions, structures, chemistry and properties of wood, biorefineries and valorisation of woody biomass, with a focus on the extraction and use of nanocellulose and wood extracts. In the academic and business environment, he promotes the sustainable use of wood in the circular bioeconomy and takes care of UL’s reputation at home and abroad. Keywords: University of Ljubljana, Golden Plaque, wood chemistry Prof. dr. Primož Oven, univ. dipl. inž. les., na Univerzi v Ljubljani deluje vse od leta 1990, ko se je po diplomi (1989) kot mladi raziskovalec zaposlil na Oddelku za lesarstvo Biotehniške fakultete UL. Magistriral je leta 1993 in doktoriral leta 1997. Do leta 2008 je izjemno uspešno kot pedagog in razi- skovalec deloval na Katedri za tehnologijo lesa, kjer je bil od leta 2004 do 2008 tudi vodja raziskovalne skupine “Tehnologija lesa«. Leta 2008 pa se je dr. Oven pogumno odločil za zamenjavo svojega ož- jega raziskovalnega področja, na katerem je že bil mednarodno uveljavljen znanstvenik. Intenzivno se je začel ukvarjati s kemijo lesa in leta 2008 prešel na Katedro za kemijo lesa in drugih lignoceluloznih materialov, ki jo še vedno vodi. Kemija lesa je na Oddelku za lesarstvo pedago- ška in raziskovalna dejavnost z dolgoletno tradicijo. Prof. Ovnu je na tem temelju z dobro pretehtanimi odločitvami in zavzetim delom uspelo okrog sebe zbrati odlično pedagoško in raziskovalno ekipo, za Vol. 71, No. 2, 67-72 DOI: https://doi.org/10.26614/les-wood.2022.v71n02a06 1 Univerza v Ljubljani, Biotehniška fakulteta, Oddelek za lesarstvo 1 University of Ljubljana, Biotechnical Faculty, Department of Wood Science and Technology * marko.petric@bf.uni-lj.si ** ida.poljansek@bf.uni-lj.si 68 Les/Wood, Vol. 71, No. 2, December 2022 Petrič, M., Poljanšek, I.: Prof. Dr. Primož Oven – recipient of the Golden Plaque of the University of Ljubljana področje je navdušil mlajše sodelavce in študente, laboratorije je opremil z najsodobnejšo raziskoval- no opremo ter vzpostavil tesne stike z gospodar- stvom. S tem je osnoval moderen in mednarodno konkurenčen laboratorij za širše znanstveno podro- čje kemije lesa (Oven, 2022a). Posebno pozornost posveča tudi prenosu in uporabi znanj v prakso, saj je svojo skupino povezal s številnimi raziskovalnimi skupinami na Biotehniški fakulteti, na Kemijskem inštitutu, na Inštitutu za celulozo in papir itd. Po- vezuje se z gospodarstvom in industrijo, s katerimi prijavlja skupne projekte, kot tudi z različnimi dr- žavnimi službami. Tako je pod njegovim vodstvom Oddelek za lesarstvo utrdil svoj status mednarodno uveljavljene in priznane institucije tudi na področju kemije lesa in lignoceluloznih materialov. Osnovno poslanstvo prof. dr. Primoža Ovna v vlogi rednega profesorja je seveda pedagoška de- javnost. Na Oddelku za lesarstvo UL BF za kemijo lesa navdušuje študente na vseh stopnjah in sme- reh študija lesarstva v okviru predmetov kot so na primer Kemija lesa, Kemična zgradba lesa, Kemična predelava lesne biomase, Nanofibrilirana celuloza iz lesnih vlaken in še nekaterih drugih predmetov. Predavatelj pa je tudi na Oddelku za gozdarstvo in obnovljive vire BF UL ter na Akademiji za likovno umetnost in oblikovanje UL. Poleg tega je bil od leta 2009 do 2022 koordinator znanstvenega področja Les in biokompoziti na interdisciplinarnem dok- torskem študiju Bioznanosti ter vodja Komisije za doktorski študij na Biotehniški fakulteti UL in je član komisije za doktorski študij Univerze v Ljubljani. Kot gostujoči profesor in raziskovalec je v letu 2010/11 deloval na Universität für Bodenkultur (BOKU) na Dunaju. O njegovem pedagoškem ugledu priča dejstvo, da je mentoriral štiri mlade raziskovalce oziroma doktorande in somentoriral dve doktoran- dki, od katerih je ena prejela nagrado za najboljši doktorat na področju papirništva. Trenutno pa pod njegovim mentorskim vodstvom študij zaključujejo trije doktorandi, pri eni doktorandki, ki je v zadnjem letniku doktorskega študija, pa je somentor. Samo po sebi je umevno, da je bil mentor tudi pri števil- nih diplomskih delih, od katerih sta bili dve nagra- jeni s fakultetno, eno pa z univerzitetno Prešernovo nagrado. V vlogi somentorja je bil pri eni magistrski nalogi, ki je bila nagrajena s fakultetno Prešernovo nagrado. Seveda tako kvalitetno pedagoško delo v uni- verzitetnem okolju ne bi bilo možno brez izvrstne- ga raziskovalnega dela z odličnimi rezultati. Znan- stveno težišče raziskav prof. Ovna, ki je rezultiralo v skoraj 100 objavljenih delih, od tega preko 60 v uglednih recenziranih revijah (Bibliografija Primož Oven, 2022), je proučevanje zvez med funkcijami, strukturami in kemizmom ter lastnostmi lesa kot in- ženirskega materiala in tkiva živih dreves. Proučeval je možnosti uporabe magnetno resonančnega slika- nja na širšem področju znanosti o lesu, kar je med drugim omogočilo iznajdbo nove, v soavtorstvu patentirane metode za določanje lesne vlažnosti. V zadnjem obdobju pa je raziskovalno delo usmeril na področje biorafinacije in valorizacije lesne bio- mase s poudarkom na pridobivanju in razvoju apli- kacij ekstraktivov lesa in skorje ter nanofibrilirane celuloze. S svojimi raziskavami in aktivnim vključe- vanjem v strategije razvoja na področju lignocelulo- znih materialov tako na UL kot tudi v družbenem in gospodarskem okolju dr. Oven posega na dandanes izjemno aktualen prehod v krožno gospodarstvo, ki ga s svojimi pedagoškimi in raziskovalnimi izkušnja- mi in delom aktivno sooblikuje. V tem kratkem prispevku je nemogoče opisa- ti vse številne aktivnosti prejemnika Zlate plakete Univerze v Ljubljani, prof. dr. Primoža Ovna. Zato naj omenimo le še, da je bil glavni in odgovorni ure- dnik Zbornika za gozdarstvo in lesarstvo v letu 2006 in je tudi član uredniškega odbora te revije, sedaj Acta Silvae at Ligni. V letih 2021 in 2022 je gostujoči urednik posebne izdaje Chemistry and Applications of Lignocellulosic Materials pri reviji Forests, kot na- cionalni predstavnik in ekspert je aktivno deloval v komiteju in akcijah COST Evropske unije ter bil vod- ja različnih raziskovalnih projektov doma in v tujini. Veseli smo, da imamo na Oddelku za lesarstvo Biotehniške fakultete UL tako odličnega sodelavca, kolego in prijatelja. Iskrene čestitke, Primož! 69 Les/Wood, Vol. 71, No. 2, December 2022 Petrič, M., Poljanšek, I.: Prof. dr. Primož Oven – prejemnik Zlate plakete Univerze v Ljubljani Slika 1. Rektor Univerze v Ljubljani prof. dr. Gregor Majdič izroča zlato plaketo (Foto: Viljem Vek). Figure 1. The rector of the University of Ljubljana presents the Golden Plaque (Photo: Viljem Vek). Prof. Dr. Primož Oven, Univ. B. Sc. Wood Eng. has been working at the University of Ljubljana since 1990, when, after graduation (1989), he was employed as a young researcher at the Department of Wood Science and Technology of the Biotechni- cal Faculty of the University of Ljubljana. He ob- tained his master’s degree in 1993 and his PhD in 1997. Until 2008, he worked extremely successfully as a lecturer and researcher at the Department of Wood Technology, where he was also the head of the “Wood Technology” research group from 2004 to 2008. In 2008, Dr. Oven courageously decided to change his narrow field of research, in which he was already an internationally recognised scientist. He began to work intensively on wood chemistry and in 2008 moved to the Chair of Chemistry of Wood and Other Lignocellulosic Materials, which he still heads. Wood chemistry is a pedagogical and research activity with a long tradition at the Department of Wood Science and Technology. On this basis, with well-considered decisions and dedicated work, Dr. Oven has succeeded in gathering around him an excellent teaching and research team, inspiring younger colleagues and students to take up the subject, equipping the laboratories with state-of- the-art research equipment, and establishing close contacts with industry. As a result, he has created a modern and internationally competitive labora- tory for the wider scientific field of wood chemis- try (Oven, 2022b). He also pays special attention to the transfer and application of knowledge in prac- tice, as he has linked his group with many research groups at the Biotechnical Faculty, the National In- stitute of Chemistry, the Institute of Pulp and Pa- per, and others. He is in contact with business and industry, with which he applies for joint projects, as 70 Les/Wood, Vol. 71, No. 2, December 2022 Petrič, M., Poljanšek, I.: Prof. Dr. Primož Oven – recipient of the Golden Plaque of the University of Ljubljana well as with various government agencies. Under his leadership, the Department of Wood Science and Technology has consolidated its status as an in- ternationally established and recognised institution also in the field of wood chemistry and lignocellu- losic materials. The main task of Prof. Dr. Primož Oven as a full professor is, of course, teaching. At the De- partment of Wood Science and Technology of UL BF he inspires students at all levels and in all pro- grammes of the study of wood science and technol- ogy on topics such as wood chemistry, the chemical structure of wood, chemical processing of woody biomass, nanofibrillated cellulose from wood fibres and some other topics. He is also a lecturer at the Department of Forestry and Renewable Resources BF UL and at the Academy of Fine Arts and Design UL. In addition, from 2009 to 2022 he was the coor- dinator of the scientific area of wood and biocom- posites in the interdisciplinary PhD programme in Biosciences and the head of the Commission for Doctoral Studies at the Biotechnical Faculty of UL, and is a member of the Commission for Doctoral Studies of the University of Ljubljana. In 2010/11 he worked as a visiting professor and researcher at the University of Natural Resources and Applied Life Sciences (BOKU) in Vienna. His pedagogical reputation is evidenced by the fact that he has su- pervised four young researchers or PhD students and co-supervised two female PhD students, one of whom received an award for the best PhD thesis in pulp and paper science. Three doctoral students are currently completing their studies under his su- pervision, and he is the co-mentor of one doctoral student who is also in the final year of her doctor- al studies. It goes without saying that he has also supervised many diploma theses, two of which were awarded the Faculty’s and one the Universi- ty’s Prešeren Prize. In the role of co-mentor, he was Slika 2. Prejemnik Zlate plakete Univerze v Ljubljani, prof. dr. Primož Oven (Foto: Katja Kodba in Nebojša Tejić (STA)). Figure 2. Recipient of the Golden Plaque of the University of Ljubljana, Prof. Dr. Primož Oven (Photo: Katja Kodba and Nebojša Tejić (STA)). 71 Les/Wood, Vol. 71, No. 2, December 2022 Petrič, M., Poljanšek, I.: Prof. dr. Primož Oven – prejemnik Zlate plakete Univerze v Ljubljani also involved in a master’s thesis that was awarded with the Faculty’s Prešeren Prize. Of course, such high-quality educational work in an academic environment would not be possible without excellent research work with outstanding results. Prof. Oven’s scientific research focus, which has resulted in nearly 100 published papers, includ- ing more than 60 in prestigious journals (Bibliografi- ja Primož Oven, 2022), is the study of the relation- ships among the functions, structures, chemistry and properties of wood as an engineering materi- al and the tissues of living trees. He explored the possibilities of using magnetic resonance imaging in the broader field of wood science, which led, among other things, to the invention of a new method for determining wood moisture content, which he helped to develop and patent. In recent years he has focused his research on the field of biorefining and valorisation of woody biomass with emphasis on the extraction and development of the application of wood and bark extracts and na- nofibrillated cellulose. Through his research and ac- tive involvement in lignocellulosic material devel- opment strategies, both at UL and in the broader social and economic spheres, Dr. Oven is involved in today’s highly relevant transition to a circular economy, which he is actively shaping through his experience and work in teaching and research. In this short presentation, it is impossible to describe all the many and varied activities of the recipient of the Golden Plaque of the University of Ljubljana, Prof. Dr. Primož Oven. Therefore, it will only be mentioned that he was the Editor-in-Chief of the Proceedings of Forestry and Woodworking in 2006 and is also a member of the Editorial Board of this journal, which is now called Acta Silvae at Ligni. In 2021 and 2022, he was the guest editor of the special issue of the Forest journal focusing on the chemistry and applications of lignocellulosic materials. As a national representative and expert, he actively participated in the COST committee and COST actions of European Union, and was the lead- er of several research projects at home and abroad. We are pleased to have such an excellent co-worker, colleague, and friend at the Department of Wood Science and Technology of University of Ljubljana’s Biotechnical Faculty. Sincere congratula- tions, Primož! VIRI REFERENCES Bibliografija Primož Oven – COBISS, Kooperativni online bibliografski sistem. URL: https://bib.cobiss.net/bibliographies/si/webBi- blio/bib201_20221208_123809_11223.html (8. 12. 2022). Oven, P . (2022a). Katedra za kemijo lesa in drugih lignoceluloznih ma- terialov. V: Matjašec, D., Sepčić, K., Kunej, T. & Brus, R. (ur.), Petinsedemdesetletnica Biotehniške fakultete Univerze v Lju- bljani. Ljubljana: Biotehniška fakulteta, 37-39. URL: https:// repozitorij.uni-lj.si/IzpisGradiva.php?lang=slv&id=142082 (8. 12. 2022). Oven, P . (2022b). Chair of chemisty of wood and other lignocellulose materials. In: Matjašec, D., Sepčić, K., Kunej, T. & Brus, R. (eds.), Seventy fifth anniversary of the Biotechnical Faculty University of Ljubljana [na spletu]. Ljubljana: Biotechnical Faculty, 37-39. URL: https://repozitorij.uni-lj.si/IzpisGradiva.php?lang=slv&id= 142081 (8. 12. 2022) 72 Les/Wood, Vol. 71, No. 2, December 2022 Petrič, M., Poljanšek, I.: Prof. Dr. Primož Oven – recipient of the Golden Plaque of the University of Ljubljana 73 Les/Wood, Vol. 71, No. 2, December 2022 Les/Wood Novice/News Častni naziv Kongresni ambasador Slovenije za leto 2022 je prejel prof. dr. Miha Humar Honorary title of Congress Ambassador of Slovenia for 2022 awarded to Prof. Dr. Miha Humar Tina Drolc V torek, 22. novembra 2022, je Kongresni urad Slovenije ob podpori Slovenske turistične organi- zacije in Kongresnega urada Turizma Ljubljana že četrtič podelil častne nazive Kongresni ambasador oziroma ambasadorka Slovenije. Časten naziv je prejelo 14 kongresnih ambasadork in ambasador- jev, med njimi je tudi prof. dr. Miha Humar s Kate- dre za lesne škodljivce, zaščito in modifikacijo lesa Oddelka za lesarstvo Biotehniške fakultete Univerze v Ljubljani. Mag. Petra Stušek, direktorica Turizma Ljubljana, je na podelitvi povedala: »Izjemni posa- mezniki, ki so danes prejeli naziv Kongresni amba- sador, s svojim aktivnim in dolgoletnim delovanjem krepijo pozicijo Slovenije kot enega od središč inte- lektualnega kapitala, inovativnosti ter trajnostnega in regenerativnega razvoja v širši regiji. Ponosna sem, da večina letošnjih prejemnikov tega častnega naziva deluje v okviru članic Univerze v Ljubljani ali nacionalno pomembnih znanstvenoraziskovalnih, gospodarskih in kulturnih ustanovah s sedežem v našem mestu, kar podpira nadaljnji razvoj Ljubljane kot vodilne slovenske kongresne destinacije.« Zbra- ne sta nagovorila tudi mag. Maja Pak, direktorica Slovenske turistične organizacije in Fredi Fontanot, v. d. direktorja Kongresnega urada Slovenije. Sve- čana prireditev je potekala v Stanovski dvorani Lju- bljanskega gradu. V letu 2022 je sedemčlanska komisija, ki so jo sestavljali predstavniki destinacijskih klubov in Kon- gresnega urada Slovenije, konec oktobra potrdila 14 dobitnikov častnega naziva. Med njimi je bilo največ nominirancev s področja znanstveno-stro- 74 Les/Wood, Vol. 71, No. 2, December 2022 Les/Wood Novice/News kovnih kongresov, eden s področja športa in nagra- jenka s področja gospodarstva. Med 1štirinajstimi dobitniki častnega naziva Kongresnega ambasador- ja Slovenije v letu 2022 je tudi prof. dr. Miha Humar, ki deluje na področju lesarstva, lesnih škodljivcev ter zaščite in modifikacije lesa. Ob prejemu naziva je povedal: »V zadnjem obdobju, posebej pa v letu 2021 in 2022, smo ob številnih mednarodnih projek- tih, ki potekajo na fakulteti, organizirali tudi različ- na mednarodna srečanja, delavnice, izobraževanja in kongrese. Izbirali smo različne lokacije v Sloveniji, v juniju je na Bledu potekalo 53. srečanje Svetov- nega združenja za zaščito lesa, ki se ga je udeleži- lo okoli 200 udeleženk in udeležencev iz 32 držav. Uspel nam je izreden dogodek, tudi v sodelovanju s predstavniki turistične destinacije, ki je navdušila naše udeleženke in udeležence.« Slovenski ambasadorski program je podpor- ni steber pri organizaciji znanstveno-strokovnih in drugih poslovnih ter športnih dogodkov. Namen podeljevanja častnih nazivov Kongresni ambasador oziroma ambasadorka Slovenije je privabiti v Slo- venijo večje število mednarodnih znanstveno-stro- kovnih in poslovnih dogodkov, saj z njihovo organi- zacijo ustvarjamo odlične priložnosti za mreženje, pretok znanja, inovacij in izmenjavo izkušenj ter vzpostavitev dolgoročnih mednarodnih povezav. On Tuesday, December 22, 2022, the Slovenian Congress Bureau, with the support of the Slovenian Tourist Board and the Ljubljana Convention Bureau of Tourism, awarded the honorary title of Congress Ambassador of Slovenia for the fourth time. Four- teen Congress Ambassadors were awarded the honorary title, including Prof. Dr. Miha Humar from the Department of Wood Pests, Wood Protection and Wood Modification, Department of Wood Sci- ence, Faculty of Biotechnology, University of Lju- bljana. As Petra Stušek, director of Ljubljana Tourism, said at the ceremony: “The outstanding personali- ties who have been awarded the title of Congress Ambassador today strengthen Slovenia’s position as one of the centres of intellectual capital, inno- vation and sustainable and regenerative develop- ment in the wider region through their active and long-standing work. I am proud that most of this year’s recipients of this honorary title work at the University of Ljubljana, or at nationally significant scientific, research, economic and cultural institu- tions in our city, which supports the further devel- opment of Ljubljana as a leading Slovenian congress destination.” The audience was also welcomed by Maja Pak, director of the Slovenian Tourist Board, and Fredi Fontanot, acting director of the Sloveni- an Convention Bureau. The gala event took place in the Estates Hall of Ljubljana Castle. A seven-member jury composed of represent- atives of destination clubs and the Slovenian Con- vention Bureau confirmed the 14 winners of the honorary title at the end of October. Among them, most of the nominees were from the field of scien- tific and professional congresses, one from the field of sports and the winner from the field of business. Among the 14 winners of the honorary title of a Congress Ambassador of Slovenia in 2022 is Prof. Dr. Miha Humar, who works in the field of wood sci- ence, wood pests and wood protection and mod- ification. He said at the event: “Recently, and es- pecially in 2021 and 2022, in addition to the many international projects taking place at the Faculty, we have organised various international meetings, workshops, trainings and congresses. We have cho- sen various locations in Slovenia, and in June the 53rd meeting of the World Association for the Pro- tection of Wood was held in Bled, with about 200 participants from 32 countries. We managed to organise an exceptional event, also in cooperation with the representatives of the tourist destination, which impressed the participants.” The Slovenian Ambassador Programme is a mainstay in the organisation of scientific, profes- sional and other business and sports events. The goal of the Slovenian Congress Ambassador or Slo- venian Ambassador Honour is to attract a greater number of international scientific, professional and business events to Slovenia, as the organisation of these events creates excellent opportunities for networking, knowledge flow, innovation and the exchange of experience, as well as building long- term international relationships. 75 Les/Wood, Vol. 71, No. 2, December 2022 Les/Wood Novice/News Doc. dr. Davor Kržišnik prejemnik Svečane listine za mlade visokošolske učitelje in visokošolske sodelavce UL Assistant Professor Dr. Davor Kržišnik recipient of the Ceremonial Certificate for Young Higher Education Teachers and Higher Education Associates of the University of Ljubljana Miha Humar Doc. dr. Davor Kržišnik je zaposlen na Oddelku za lesarstvo Biotehniške fakultete Univerze v Lju- bljani (OL BF UL). Trenutno opravlja delo asistenta in je habilitiran v naziv docenta za področje Znanost o lesu in lignoceluloznih kompozitih ter tehnologije v lesarstvu. Davor Kržišnik je diplomiral leta 2014 na MSc programu Lesarstvo. Že med študijem se je dva semestra usposabljal v tujini na Tuscia Uni- versity (Università degli Studi della Tuscia) (prof. dr. Mauela Romagnoli), na osnovi česar je objavil tudi izvirni znanstveni članek. Stike s to raziskoval- no skupino je ohranil, kar se kaže v raziskovalnem sodelovanju. Slika 1. Davor Kržišnik je prejel svečano listino za mlade visokošolske učitelje in visokošolske sodelavce Univerze v Ljubljani za leto 2022. Podelil mu jo je rektor Univerze v Ljubljani prof. dr. Gregor Majdič (Foto: Katja Kodba in Nebojša Tejić/STA, 2022) Figure 1. Davor Kržišnik received the 2022 Ceremonial Certificate for Young Higher Education Teachers and Higher Education Associates from the rector of the University of Ljubljana prof. Dr. Gregor Majdič (Photo: Katja Kodba and Nebojša Tejić/STA, 2022) 76 Les/Wood, Vol. 71, No. 2, December 2022 Les/Wood Novice/News V letu 2015 se je Davor Kržišnik zaposlil kot mladi raziskovalec v programski skupini P4-0015 Les in lignocelulozni kompoziti. V okviru doktorskega študija je predstavil povezavo med laboratorijskimi in terenskimi preizkusi pri ocenjevanju funkcional- ne in estetske življenjske dobe lesa. Ovrednotil je potencial različnih laboratorijskih testov za namen napovedovanja dinamike vlaženja lesa na prostem. Dokazal je, da se lahko nekateri hitrejši laboratorij- ski preizkusi uporabijo za napovedovanje dinamike spremembe vlažnosti na prostem. V drugem delu se je posvetil analizi barvnih sprememb lesa na prostem. Večina rezultatov disertacije je bila pred- stavljena na domačih in mednarodnih konferencah. Disertacija je sestavljena iz desetih znanstvenih člankov, objavljenih v vrhunskih revijah s področ- ja lesarstva. Uspešno delo na področju zaščite lesa je prepoznalo tudi mednarodno društvo za zaščito lesa in Davorju v letu 2019 podelilo nagrado Ron Cockroft award za udeležbo na mednarodni konfe- renci v Quebecu. V času zaposlitve se je Davor Kržišnik angaži- ral pri raziskovalnem delu. Usposobil se je za delo na raznolikih laboratorijsko-eksperimentalnih teh- nikah (mikrobiološke tehnike, dinamična sorpcija vodne pare, piknometrija, modifikacija lesa, FTIR, digitalna in konfokalna mikroskopija, terensko delo …), kar se kaže v številnih objavah. Davor Kržišnik je soavtor 30 izvirnih znanstvenih člankov, sodeluje pri prijavi projektov. Zelo pomemben je podatek, da je bil v imenu Biotehniške fakultete uspešen pri prijavi nove programske skupine (P4-0430) pod ko- ordinatorstvom Gozdarskega inštituta. Davor Krži- šnik tako koordinira delo te programske skupine na Biotehniški fakulteti. Dela dr. Kržišnika so odmevna, kar se izraža v več kot 200 citatih. Dr. Davor Kržišnik se zelo vključuje v pedago- ško delo katedre. Že kmalu po zaposlitvi je začel z delovnim mentoriranjem diplomantov. Pedagoško delo je nadaljeval z vodenjem vaj pri predmetih na študiju Lesarstva, študiju Biotehnologije in študiju Konzervatorstva na ALUO. Udeležuje se številnih usposabljanj, ki jih organizira UL in ta spoznanja sproti prenaša v pedagoško prakso. Vse to se od- raža v odličnih pedagoških ocenah. Dr. Davor Krži- šnik je aktiven tudi na strokovnem področju in kot promotor sodeluje pri promociji študija lesarstva v srednjih šolah. Poleg tega dr. Kržišnik sodeluje z Lesarskim grozdom pri uvajanju okoljevarstvenih zahtev v lesno industrijo kot pospeševalec in preso- jevalec. Vse to je prepričalo strokovno komisijo UL, da dr. Kržišniku podeli ugledno priznanje. Svečane listine za mlade visokošolske učiteljice in učitelje ter visokošolske sodelavke in sodelavce sta prejeli še dve mladi sodelavki Biotehniške fakul- tete (Teden univerze, 2022). To sta asist. dr. Meta Sterniša in asist. dr. Katarina Šimunović. Dr. Ster- niša je leta 2020 doktorirala na Katedri za bioteh- nologijo, mikrobiologijo in varnost živil, Oddelka za živilstvo BF, kjer se z raziskovalnim in pedagoškim delom usmerja v živilsko mikrobiologijo, bakterij- sko encimsko aktivnost in filmotvornost ter načine preprečevanja kvarnih mikrobioloških procesov. Dr. Šimunović, asistentka na Oddelku za mikrobiologijo, je odlična raziskovalka in predana pedagoginja, ki je ključno in z navdušenjem prispevala k pomembnim raziskovalnim objavam na področju mikrobiologije, prijavi patenta in zagonu start-up podjetja za razvoj in trženje inovacij. Vsem iskrene čestitke! Assist. Prof. Dr Davor Kržišnik is employed in the Department of Wood Science and Technolo- gy at the Biotechnical Faculty of the University of Ljubljana. He currently works as an assistant and is habilitated as an assistant professor in the field of wood science and lignocellulosic composites and technology in wood science. Davor Kržišnik com- pleted the MSc programme in Wood Science and Technology in 2014. Already during his studies he completed two semesters abroad, at the University of Tuscia (Università degli Studi della Tuscia) (Prof. Dr. Mauela Romagnoli), based on which he also published an original scientific article. He main- tained contacts with this research group, which is reflected in his research collaboration. In 2015, Davor Kržišnik was hired as a young researcher in the P4-0015 Wood and Lignocellu- losic Composites programme group. As part of his PhD studies, he presented the link between labo- ratory and field testing in assessing the functional and aesthetic service life of wood. He evaluated the potential of different laboratory tests to pre- dict the outdoor moisture dynamics of wood. Mr Kržišnik proved that some faster laboratory tests can be used to predict the dynamics of outdoor moisture changes. In the second part, he devoted himself to the analysis of colour changes of wood 77 Les/Wood, Vol. 71, No. 2, December 2022 Les/Wood Novice/News outdoors. Most of the results of the dissertation were presented at national and international con- ferences. The dissertation consists of ten scientif- ic articles published in leading journals in the field of wood research. The successful work in the field of wood preservation was also recognised by the International Association for Wood Protection. in 2019, Davor was awarded the Ron Cockroft Award for participation in an international conference in Quebec. Dr. Kržišnik was active in research during his employment. He trained in various experimental laboratory techniques (microbiological techniques, dynamic water vapour sorption, pycnometry, wood modification, FTIR, digital and confocal microscopy, and field work, among others), which is reflected in numerous publications. Dr. Kržišnik is the co-author of 30 original scientific articles and participates in the registration of projects. It is very important to mention that he successfully applied for a new pro- gramme group (P4-0430) under the coordination of the Forest Institute on behalf of the Faculty of Biotechnology. Davor Kržišnik is thus coordinating the work of this programme group at the Faculty of Slika 2. Prejemniki Svečane listine za mlade visokošolske učitelje in visokošolske sodelavce Univerze v Lju- bljani za leto 2022 iz Biotehniške fakultete: doc. dr. Davor Kržišnik, asist dr. Meta Sterniša in asist. dr. Kata- rina Šimunović. Figure 2. Recipients of the 2022 Ceremonial Certificates for Young Higher Education Teachers and Higher Education Associates of the University of Ljubljana from the Biotechnical Faculty: Associate Professor Dr. Davor Kržišnik, Assistant Professor Dr. Meta Sterniša and Assistant Professor Dr. Katarina Šimunović. 78 Les/Wood, Vol. 71, No. 2, December 2022 Les/Wood Novice/News Biotechnology. Dr Kržišnik’s work is also having an impact on other researchers, as reflected in around 200 citations his publications have already gained. Dr. Davor Kržišnik is very involved in the de- partment’s educational work. Soon after he was hired, he began mentoring graduates. He con- tinued his educational work by leading exercises in the courses in Wood Science and Technology, Wood Engineering, Biotechnology and Conserva- tion at ALUO. Dr. Kržišnik participates in numerous trainings organised by UL and transfers this knowl- edge into pedagogical practice. All this is reflected in excellent pedagogical evaluations. Dr. Kržišnik is also professionally active, working to promote the study of wood science in secondary schools. In ad- dition, Dr. Kržišnik cooperates with the Wood In- dustry Cluster in the introduction of environmental protection requirements in the wood industry, as an accelerator and reviewer. All this has convinced the UL Expert Committee that Dr. Kržišnik should receive a prestigious award. The ceremonial certificates for young univer- sity teachers and university assistants of the Uni- versity of Ljubljana have been received by two more young colleagues of the Biotechnical Facul- ty. They are Assistant Professor Dr. Meta Sterniša and Assistant Professor. Dr. Katarina Šimunović. Dr. Sterniša received her PhD in 2020 in the Depart- ment of Biotechnology, Microbiology and Food Safety, and the Department of Food Science and Technology. Her research and teaching activities focus on food microbiology, bacterial enzyme activ- ity and film formation, and ways to prevent these defective microbiological processes. Dr. Šimunović in the Department of Microbiology is an outstand- ing researcher and dedicated educator who has enthusiastically contributed to important research publications in the field of microbiology, a patent application, and the creation of a start-up compa- ny for the development and commercialisation of research innovations. Congratulations to all certif- icate awardees. VIRI / REFERENCES Foto: Katja Kodba in Nebojša Tejić/STA, Univerza v Ljubljani, Pode- litev priznanj strokovnim sodelavkam in sodelavcem Univerze v Ljubljani. URL: UNILJ > Medijsko središče > Foto galerija > Teden Univerze > Teden Univerze 2022 https://www.uni-lj.si/ medijsko_sredisce/foto_galerija/teden_univerze/teden_uni- verze_2022/2022120209064199/ (8. 12. 2022). Teden Univerze v Ljubljani 2022, Svečana listina za mlade viso- košolske učiteljice in učitelje ter visokošolske sodelavke in sodelavce. URL: https://www.uni-lj.si/tedenuniverze/tede- nuniverze_2022/svecana_listina_za_mlade_visokosolske_uci- teljice_in_ucitelje_ter_visokosolske_sodelavke_in_sodelavce/ (8. 12. 2022). Priznanje Univerze v Ljubljani skupini strokovnih sodelavk in sodelavcev Biotehniške fakultete Katarina Čufar V Tednu univerze v letu 2022 je Univerza v Ljubljani podelila priznanje skupini strokovnih so- delavk in sodelavcev Biotehniške fakultete za po- memben prispevek k izboljšanju delovnih procesov in pozitivni klimi na fakulteti in univerzi. Skupina strokovnih sodelavk in sodelavcev je priznanje prejela za uvedbo sistema APIS na Bio- tehniški fakulteti Univerze v Ljubljani. Priznanje so prejeli Darko Klobučar, Ana Kaplan Novak, Polona Hribar, Mateja Bregant Perić, Nataša Miklavčič, Sandra Zafirovič, Jana Trakoštanec, Renata Kovačič, Tomaž Valenčič, Mihael Prosenjak, Petra Žejavac, Jasna Lukan, Urška Iglič, Tadeja Lovšin, Anita Strmo- le, Jožef Hanč, Tea Kuzman, Maja Kristan Mihičinac, Tadeja Dečman Flis, Tamara Štular, Tina Košnjek, Tomaž Podboj, Anton Zupančič, Mojca Dermastja, Sonja Osolnik, Selma Uršula Muhar in Anja Uršič. V letu 2019 je Univerza v Ljubljani začela pro- jekt uvajanja enotnega poslovno informacijskega sistema APIS – Sap. Biotehniška fakulteta ga je us- pešno začela uporabljati 1. aprila 2021. To je omo- gočilo prehod na enoten sistem, ki povezuje vse ključne poslovne funkcije in procese Univerze v Ljubljani ter zagotavlja najvišjo stopnjo transparen- tnosti, zanesljivosti poslovanja in zagotavljanja na- tančnih in točnih podatkov. Da je uporaba sistema 79 Les/Wood, Vol. 71, No. 2, December 2022 Les/Wood Novice/News stekla, so zaslužni strokovni sodelavci in sodelavke, ki so sodelovali pri pripravi potrebnih baz podatkov, se učili uporabe modulov novega poslovnoinfor- macijskega sistema APIS ter učili svoje sodelavce in druge zaposlene na Biotehniški fakulteti Univerze v Ljubljani. V sodelovanju s koordinatorji ključnih uporabnikov so tvorno sodelovali in predlagali šte- vilne rešitve, ki so pripomogle k boljšemu delova- nju sistema (Teden univerze, 2022). Sodelavkam in sodelavcem za zasluženo pri- znanje iskreno čestitamo! Med prejemniki priznanja je tudi Anton Zupan- čič, univ. dipl. inž. les. z Oddelka za lesarstvo. Kolega Zupančič je tajnik in vodja skupnih služb oddelka. Poleg rednih zadolžitev, ki so bile v preteklem ob- dobju nadpovprečne zaradi uvajanja omenjenega sistema, je Tone nepogrešljiv sodelavec, ki ima ve- like zasluge za delovanje Oddelka. Nanj se zaposle- ni na Oddelku dnevno obračamo z najrazličnejšimi vprašanji v zvezi z administrativnim in finančnim poslovanjem, delovanjem stavbe in opreme v učil- nicah, uporabo računalniških sistemov in mnogimi drugimi vprašanji, če je njegova številna opravila in zasluge sploh mogoče strniti v tako kratek zapis. Anton Zupančič je tudi tehnični urednik revije Les/ Wood z izjemnim znanjem in izkušnjami. Tone, iskrene čestitke za zasluženo priznanje! VIRI Foto: Katja Kodba/STA, Univerza v Ljubljani, Podelitev priznanj stro- kovnim sodelavkam in sodelavcem Univerze v Ljubljani. URL: UNILJ > Medijsko središče > Foto galerija > Teden Univerze > Teden Univerze 2022 URL: https://www.uni-lj.si/medij- sko_sredisce/foto_galerija/teden_univerze/teden_univer- ze_2022/2022120209300854/ (8. 12. 2022) Teden Univerze v Ljubljani 2022, Priznanje strokovnim sodelavkam in sodelavcem. URL: https://www.uni-lj.si/tedenuniverze/tedenuniverze_2022/pri- znanje_strokovnim_sodelavkam_in_sodelavcem/ (8. 12. 2022) Slika 1. Prejemnice in prejemniki priznanja strokovnim sodelavkam in sodelavcem na podelitvi v zbornični dvorani Univerze v Ljubljani (Foto: Katja Kodba/STA). Slika 2. Anton Zupančič z Oddelka za lesarstvo je s skupino sodelavk in sodelavcev Biotehniške fakul- tete prejel priznanje, ki jim ga je v Tednu univer- ze 2022 podelil rektor Univerze v Ljubljani prof. dr. Gregor Majdič (Foto: Katja Kodba/STA). 80 Les/Wood, Vol. 71, No. 2, December 2022 Les/Wood Novice/News 14. srečanje ALUMNI kluba Oddelka za lesarstvo 14th Meeting of the Alumni Club of the Department of Wood Science and Technology Katarina Čufar, Boštjan Lesar, Tomaž Kušar, Jure Žigon Po triletni prekinitvi zaradi epidemije covida-19 se je skupnost alumnov Oddelka za lesarstvo 23. 11. 2022 ponovno zbrala na tradicionalnem sreča- nju. Tokrat se je na srečanju zbralo okoli 120 bivših študentk in študentov. Udeleženke in udeleženci srečanja so se začeli zbirati že v popoldanskih urah. Poleg uradnega ogleda Oddelka so si vsi najbolj že- leli druženja ter se po dolgem času s kolegicami in kolegi pogovoriti, kaj je novega. Uradni program je bil kot po navadi namenjen predstavitvam novosti na Oddelku in v stroki. Letos ga je popestril nastop mladega čelista Filipa Dem- šarja. Zaigral je na inštrument, izdelan v Ateljeju Demšar, ki ga vodi njegov oče, priznani goslar in naš alumen Blaž Demšar. Podrobneje se nam je predstavila skupina di- plomantov, ki so diplomirali pred 20 leti. Že kot štu- denti so bili zelo aktivna in prepoznavna generacija, ki je imela tudi to posebnost, da v letniku ni ime- la nobene kolegice. Pohvalijo se lahko, da so med njimi številni direktorji in podjetniki, dva doktorja znanosti in en nosilec znanstvenega magisterija. Na letošnjem srečanju so se posebej predstavili mag. Tomaž Kušar, vodja Društva lesarjev Slovenije, univ. dipl. inž. les. Tomaž Vilar iz podjetja DIMPEX, ki je bil glavni sponzor srečanja, in izr. prof. dr. Maks Me- rela, novi prodekan Oddelka za lesarstvo BF. Slika 1. Ogledi laboratorijev. Figure 1. Laboratory tours. Slika 2. Polna predavalnica in glasba. Figure 2. Full lecture room and music. 81 Les/Wood, Vol. 71, No. 2, December 2022 Les/Wood Novice/News Tomaž Vilar je predstavil podjetje DIMPEX lesnoobdelovalni stroji, ki se ukvarja s prodajo lesnoobdelovalnih strojev priznanih proizvajalcev iz Nemčije, Avstrije, Švice in Češke. Poleg prodaje nudijo vsestransko podporo kupcem, ki vključuje servis in vzdrževanje, rezervne dele, montažo, za- gon strojev in usposabljanje za varno delo ter seli- tev strojev. Podrobneje nam je predstavil prodajni program različnih proizvajalcev kot so HOLZHER, ALTENDORF, KUNDIG, LANGZAUNER, ELKOM, RE- INBOLD in ADAMIK, s posebnim poudarkom na inovativnih rešitvah, ki omogočajo varno in kakovo- stno delo. Raziskovalno delo na Oddelku za lesarstvo so letos predstavile mlade raziskovalke in raziskovalci oz. doktorski študentki in študent. Mlada razisko- valka Eli Keržič je predstavila raziskave, ki proučuje- jo spremembe odpornosti lesa zaradi izpiranja bio- loško aktivnih učinkovin in spremembe morfologije površin kot posledice vremenskih vplivov. Raziskave potekajo predvsem v sodelovanju s prof. dr. Miho Humarjem in doc. dr. Viljemom Vekom. Doktorska študentka Urška Osolnik je predstavila raziskovalno delo na Katedri za kemijo lesa, kjer deluje skupaj s Slika 3. Predstavniki generacije, ki je zaključila študij pred 20 leti. Figure 3. Representatives of the generation which graduated 20 years ago. Slika 4. Tomaž Vilar univ. dipl. inž. les. in podjetje DIMPEX–glavni sponzor srečanja. Figure 4. Tomaž Vilar univ. dipl. ing. and DIMPEX, the main sponsor of the meeting. 82 Les/Wood, Vol. 71, No. 2, December 2022 Les/Wood Novice/News prof. dr. Primožem Ovnom (vodja katedre) ter izr. prof. dr. Ido Poljanšek in doc. dr. Viljemom Vekom. Uradnemu delu je sledilo neformalno druže- nje, ki so se ga alumni po treh letih omejitev zaradi pandemije najbolj razveselili. Sponzor in organiza- torji so kot vedno poskrbeli za pogostitev, vsi skupaj pa za prijetno vzdušje. Srečanja so se nekateri udeležili prvič po diplo- mi, in tako po daljšem času tudi več (deset) let spet videli, kako je danes na “faksu”. Alumni klub ima tudi zelo zveste udeležence, ki nikoli ne manjkajo. Med njimi je skupina alumnov, ki se približujejo 50-letnici diplome. Slika 5. Nepogrešljivo druženje. Figure 5. A much-appreciated get-together. Slika 6. Milan Pohar, Miran Bajec, Milan Osterman in Janko Stanonik, diplomirani inženirji lesarstva, ki so se na študij lesarstva vpisali v letu 1967/68 in diplomirali pred skoraj 50 leti. Predstavljajo eno najbolj zvestih skupin alumnov in se srečanja udeležijo vsako leto. Figure 6. Milan Pohar, Miran Bajec, Milan Osterman and Janko Stanonik, wood science and technology engineers who began their studies in 1967/68 and graduated nearly 50 years ago. They represent one of the most loyal groups of alumni, those who attend the reunion every year. 83 Les/Wood, Vol. 71, No. 2, December 2022 Les/Wood Novice/News Srečanje vedno radi obiščejo tudi mladi udele- ženci, ki so diplomirali ali magistrirali pred kratkim, redno pa na srečanje povabimo tudi predstavnike študentov. Tokrat sta nam dva študenta in motivira- na tutorja tudi pomagala pri pogostitvi. Med zelo motivirane alumne, ki redno obisku- jejo srečanje, je tudi skupina, ki je visokošolski štu- dij končala okoli leta 2006. Pravijo, da se radi vrača- jo nazaj na svoj “faks”, tudi zato, ker jih nanj in na kolegice ter kolege vežejo lepi spomini. Srečanje je organiziral klub alumnov Oddelka za lesarstvo Univerze v Ljubljani skupaj z Društvom lesarjev Slovenije. Oddelek in Društvo sta srečanje tudi vsestransko podprla, za kar se iskreno zahva- ljujemo. Srečanja so se v velikem številu udeležili kolegice in kolegi Oddelka za lesarstvo, ki so z veli- ko zagnanostjo prevzeli vlogo organizatorjev. Vsem lepa hvala. Velika zahvala gre tudi sponzorju DIM- PEX s Tomažem Vilarjem. After 3 years of restrictions due to the COV- ID-19 pandemic, we met again at the traditional, and now 14th, Alumni Club meeting of the Depart- ment of Wood Science and Technology, Biotechni- cal faculty, University of Ljubljana (DWST BF UL). The programme of the meeting included a tour through the department, presentations with a cul- tural programme – this time performed by a young cello player Filip Demšar, a son of our alumen and respected violin maker Blaž Demšar univ. dipl. ing. During the official programme, the organisers presented what is new in DWST. The research work was presented by three young researchers, PhD students. Part of the programme was designed by the generation of alumni who graduated 20 years ago. Among them are Tomaž Vilar univ. dipl. ing., representative of the main sponsor DIMPEX, the president of the Slovenian Association of Wood Sci- ence and Technology (DLS) mag. Tomaž Kušar, and the current vice dean of DLWS BF UL, Prof. Dr. Maks Merela. The meeting was organised by the Alumni Club of UL BF DWST and DLS. Both DWST and DLS, sup- ported the meeting in every possible way, for which we would like to express our sincere gratitude. The meeting was well attended by alumni of all gener- ations, who also appreciated the opportunity for an informal face-to-face meeting with colleagues. We thank the DWST staff who enthusiastically took on the role of organisers. A big thanks also goes to the sponsor DIMPEX with Tomaž Vilar. The pictures show that the meeting was a great success. Slika 7. Leta 2006 so pridobili strokovne nazive in odšli vsak svoji karieri naproti, sedaj, več let kasneje, pa se še vedno radi vračajo nazaj na svoj “faks”. Figure 7. In 2006, they earned their professional degrees and left the faculty to pursue their careers. Now, many years later, they still enjoy returning to their faculty. 84 Les/Wood, Vol. 71, No. 2, December 2022 Les/Wood Novice/News Poročilo z drugega posveta projektne skupine projekta L4-2623: EKSTRAKTIVI V JELOVIH GRČAH Viljem Vek, Ida Poljanšek, Primož Oven V sredo, 15. junija 2022, je v Podjetniškem inkubatorju Kočevje potekal posvet in drugi letni sestanek projektne skupine L4-2623. Posvet z nas- lovom Ekstraktivi v jelovih grčah je bil organiziran skladno s terminskim planom aktivnosti, ki je defi- niran v projektni prijavi ARRS-RPROJ-JR/929. Vod- ja delovnega sklopa WP 7 prof. dr. Primož Oven, ki pokriva področje upravljanja projekta in disemina- cije, je sestanek organiziral v sodelovanju z dr. Ido Poljanšek in dr. Viljemom Vekom. Dogodek je del aktivnosti SRIP Mreže za prehod v krožno gospo- darstvo, fokusno področje Biomasa in alternativne surovine. Z aplikativnim projektom z naslovom Pridobi- vanje ekstraktivov grč in skorje z visoko vsebnostjo polifenolov iz manj izkoriščene biomase bele jelke (L4-2623) raziskujemo načine za optimalno pripra- vo drevesne biomase za ekstrakcijo ter proučujemo možnosti za učinkovito ekstrakcijo naravnih bioak- tivnih spojin iz lesa in skorje bele jelke (Abies alba). Projekt financirata Agencija za raziskave in razvoj Republike Slovenije in podjetje Ars Pharmae d. o. o. Gostitelj dogodka je bil g. Aleš Marolt, vodja razi- skovalne razvojne skupine Kočevski les. Na posvetu smo aktivno sodelovali Primož Oven, Ida Poljanšek in Viljem Vek kot predstavniki članice Univerze v Ljubljani (Biotehniška fakulteta, Oddelek za lesar- stvo), Marko Domazet in Urša Zaloker iz podjetja Ars Pharmae d. o. o. ter Aleš Marolt in Alan Obra- novič iz podjetja Kočevski les d. o. o. Seznam vseh udeležencev s kontakti je zajet v SRIP listi prisotno- sti. S tokratnim posvetom smo pozornost namenili grčam. Grče v lesu na splošno predstavljajo tehno- loške napake, v lesnopredelovali industriji so neza- želene in jih večinoma obravnavamo zgolj kot lesni ostanek. Po drugi strani pa grče predstavljajo bogat vir polifenolov, torej naravnih spojin z visoko tr- žno vrednostjo. Na posvetu smo izpostavili izbrane lesno biološke in tehnološke vsebine, ki so osnova za pridobivanje ekstraktivov iz grč bele jelke. Po uvodnem govoru dr. Primoža Ovna so Aleš Marolt ter Marko Domazet in Urška Zaloker predstavili trenutne aktivnosti raziskovalnih skupin Kočevski les in Ars Pharmae. Sledilo je predavanje z naslovom »Nastanek, struktura in kemizem grč pri jelki«, kjer je dr. Oven predstavil fiziološke osnove vej oziroma grč, opisal nastanek veje, definiral grčo, nato je nazorno predstavil kemijske in anatomske značilnosti lesa grč in tako jasno označil tkiva grč, ki predstavljajo relevantno surovino za pridobivanje in ekstrakcijo polifenolov ter s tem vsebinsko odprl novo področje. S predavanjem »Katero od polar- nih topil je najbolj primerno za ekstrakcijo jelovih grč?« je dr. Ida Poljanšek predstavila rezultate razi- skovalnih aktivnosti, ki so bile v preteklem obdobju opravljene na Oddelku za lesarstvo Biotehniške fa- kultete. Ti rezultati so jasno pokazali način za učin- kovito ekstrakcijo jelove grče, vključno z najprimer- nejšim načinom za vzorčenje grč, kakšna je ustrezna manipulacija s tkivi jelove grče, kako jelovo grčo ustrezno pripravimo za ekstrakcijo ter katera topila oziroma razmerja med topili so najprimernejša za učinkovito ekstrakcijo jelove grče. V tem sklopu so bili detajlno predstavljeni najprimernejši procesni pogoji, ki zagotavljajo visoke ekstrakcijske donose. Predavanje je zaključila s sklepnim sporočilom, kjer je jasno označila najprimernejši način za pilotno pridobivanje polifenolov iz lesa grč bele jelke. Sle- dila je predstavitev z naslovom »Vsebnost ekstrak- tivov v jelovih grčah« z natančnim povzetkom vseh aktivnosti, ki so bile opravljene v času trajanja pro- jekta L4-2623 v preteklem projektnem obdobju, z opisi vseh terenskih akcij, vzorčenj, s katerimi smo odvzeli material, ki je bil vključen v raziskave, vpli- va letnega časa na vsebnost ekstraktivov v skorji in grčah bele jelke, ter material, ki bo podal informa- cijo o vplivu sestave tal na vsebnost ekstraktivov. V tem delu je bil predstavljen seznam in število vseh odvzetih vzorcev. Projektni partnerji so se seznani- li z vsemi ključnimi rezultati, ki jasno kažejo na to, katera tkiva živih in mrtvih vej vsebujejo največ ek- straktivov, kakšna je sezonska variabilnost v vseb- nosti ekstraktivov v grčah in skorji bele jelke, na- tančno je bil predstavljen tudi plan raziskovalnega dela na projektu za zadnje projektno obdobje. 85 Les/Wood, Vol. 71, No. 2, December 2022 Les/Wood Novice/News Po predavanjih je sledila diskusija o raziskoval- nih izzivih, ki projektno skupino še čakajo do izteka aplikativnega projekta L4-2623. Projektna skupina je posvet zaključila s sklepom, da vse raziskovalne aktivnosti potekajo skladno s terminskim planom projekta L4-2623 ter da so bili v drugem projektnem letu doseženi vsi glavni projektni cilji (Spisek časov- nih mejnikov je naveden v opisu projekta na inter- netni strani Biotehniške fakultete: https://www. bf.uni-lj.si/sl/raziskave/raziskovalni-projekti/). Slika 1. Drugi posvet projektne skupine L4-2623 z naslovom »Ekstraktivi v jelovih grčah« je potekal v kon- ferenčni sobi Podjetniškega inkubatorja Kočevje (foto: Ida Poljanšek in Viljem Vek). 86 Les/Wood, Vol. 71, No. 2, December 2022 Les/Wood Novice/News Nova raziskovalna oprema na Oddelku za lesarstvo Biotehniške fakultete Univerze v Ljubljani - Instrument za določanje mikromehanskih lastnosti površin lesa, kompozitov in lesnoobdelovalnih orodij MCT3 Marko Petrič Na Oddelku za lesarstvo Biotehniške fakultete Univerze v Ljubljani smo se pred poletnimi počitni- cami leta 2022 razveselili nove pridobitve. Ob po- lovičnem finančnem prispevku Agencije Republike Slovenije za raziskovalno dejavnost (ARRS) in polo- vičnih lastnih sredstvih, smo v skupini za obdelavo površin na Katedri za lepljenje, lesne kompozite, obdelavo površin in konstruiranje uspeli pridobiti instrument za določanje mikromehanskih lastnos- ti površin različnih materialov, MCT3, proizvajalca Anton Paar. Novo opremo smo namestili v novem laboratoriju skupine za površinsko obdelavo, ki je bil prav tako dograjen in opremljen v letu 2022. Oprema MCT3 sodi v skupino instrumentov, s katerimi merimo mehanske lastnosti površin s karakterizacijskimi tehnikami, imenovanimi instru- mentalna indentacija, razenje in tribologija. Z rezul- tati meritev s takimi instrumenti dobimo odgovore na vprašanja, kot so: Kako elastična je površina? Kako dobro se premaz oprime podlage? Kako odpo- ren je material proti obrabi? ipd. Instrument MCT3 z diamantno konico različ- nih geometrij (piramida, stožec, krogla) omogoča mehanske preiskave površin z obremenjevanjem od 50 mN do 30 N z različnimi načini obremenjeva- nja. Z večcikličnim obremenjevanjem lahko trdoto in modul elastičnosti globinsko profiliramo v tankih plasteh do globine 1000 µm. To pomeni, da je mož- no določiti gradient merjenih lastnosti v odvisnosti od oddaljenosti od površine. Inštrument je opre- mljen s svetlobnim mikroskopom, ki omogoča za- jem sinhronizirane panoramske slike raze z ostalimi senzorji (preostala globina, sila trenja in akustična emisija). Tehnologija vključuje predskeniranje pro- fila površine (oblika, valovitost in hrapavost) vzorca pred izvedbo testa razenja. To omogoča popravlja- nje globine indenterja med razenjem (globina pe- netracije) in po njem (preostala globina) s profilom površine. Na ta način lahko okarakteriziramo ela- stične, plastične in viskoelastične lastnosti tankih plasti in materialov. In kakšne bodo možnosti uporabe mikro- mehanskih preiskav površin z mikroindenterjem MCT3 na Oddelku za lesarstvo za potrebe našega raziskovalnega in pedagoškega dela, za sodelujoče partnerje ter v obliki storitev za partnerje na trgu? MCT3 bo omogočil raziskave površin neobdelanega in na različne načine obdelanega lesa, lesnih kom- pozitov, lesnoobdelovalnih orodij in drugih trdnih materialov kot so npr. polimeri in polimerni filmi, vključno z lesnimi premazi, samoobnovljivimi pre- mazi, trdimi filmi, ipd. Odpirajo se možnosti raz- iskav površin arheološkega lesa, modificiranega lesa, lesa, okuženega z glivami, poslikav (premazov) na objektih kulturno zgodovinske dediščine, trdih tankih prevlek na lesnoobdelovalnih strojih, pa tudi kovin, cementnih materialov, in še bi lahko našte- vali. Merili bomo predvsem trdoto površin, elastič- ni modul, oprijemno trdnost premaza, odpornost proti razenju in obrabi. V sklopu nove opreme je tudi računalnik za upravljanje naprave z ustrezno programsko opremo za analizo in obdelavo rezulta- tov merjenja. Omogočeno je mapiranje mehanskih lastnosti mikro-strukturnih elementov ter povezava le-teh z rezultati, pridobljenimi z različnimi drugimi fizikalno-kemijskimi in optičnimi analiznimi tehni- kami na makro nivoju. 87 Les/Wood, Vol. 71, No. 2, December 2022 Les/Wood Novice/News Slika 1. Mikroindenter MCT3 v novem laboratoriju skupine za površinsko obdelavo (Foto: J. Žigon). Slika 2. Izvajanje meritve z instrumentom MCT3 (Foto: J. Žigon). 88 Les/Wood, Vol. 71, No. 2, December 2022 Les/Wood Novice/News