1 Les/Wood, Vol. 71, No. 1, June 2022 VSEBINA / CONTENTS Letnik 71, številka 1 / Volume 71, Number 1 • Uvodnik . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Editorial Matevž Rudolf • The synergistic effect of microwave drying and plasma surface treatments on the wettability of green wood . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Sinergistični učinek mikrovalovnega sušenja in obdelave s plazmo na omočljivost svežega lesa Sauradipta Ganguly, Jure Žigon, Kavyashree Srinivasa, Marko Petrič, Sebastian Dahle • Sorption properties of wood impregnated with the fire retardant Burnblock . . . . . . . . . . . . . . . . 15 Sorpcijske lastnosti lesa, impregniranega z ognjezadrževalnim sredstvom Burnblock Miha Humar, Boštjan Lesar, Davor Kržišnik • Physical and chemical properties of three wild almond wood species grown in Zagros forests . 23 Fizikalne in kemijske lastnosti lesa treh divjih vrst mandljevca, ki rastejo v gozdovih Zagrosa Leila Fathi, Redžo Hasanagić, Yaghoob Iranmanesh, Mohammad Dahmardeh Ghalehno, Miha Humar, Mohsen Bahmani • Tree-ring chronologies of Picea abies, Larix decidua and Fagus sylvatica along altitudinal gradients . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 Kronologije širin branik drevesnih vrst Picea abies, Larix decidua in Fagus sylvatica vzdolž gradientov nadmorske višine Klemen Novak, Martin de Luis, Nina Škrk, Aleš Straže, Katarina Čufar • Critical steps and troubleshooting in sample preparation for wood and phloem formation: from sampling to microscopic observation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 47 Kritični koraki in reševanje težav pri pripravi vzorcev za spremljanje nastajanja lesa in floema: od vzorčenja do opazovanja pod mikroskopom Angela Balzano, Katarina Čufar, Luka Krže, Maks Merela • Dendrokronologija in absolutno datiranje kolišč na Ljubljanskem barju . . . . . . . . . . . . . . . . . . . . 57 Dendrochronology and absolute dating of pile-dwellings in Ljubljansko Barje Katarina Čufar, Maks Merela, Luka Krže, Anton Velušček Novice • Dr. Jure Žigon je prejel Jesenkovo nagrado Biotehniške fakultete UL za najboljšega diplomanta doktorskega študija 3. stopnje 2021 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71 Dr. Jure Žigon received the Jesenko Award of the Biotechnical Faculty UL for the best PhD graduate in 2021 Sebastian Dahle, Marko Petrič • Srečanje mikroskopistov Slovenije – nagrada za najboljši poster dr. Angeli Balzano . . . . . . . . . . . 77 Meeting of Microscopists of Slovenia – Best Poster Award to Dr. Angela Balzano Maks Merela • Katedra za management in ekonomiko lesnih podjetij (Oddelek za lesarstvo Biotehniške fakul- tete) je prejela prestižno priznanje mednarodne asociacije WoodEMA . . . . . . . . . . . . . . . . . . . . . . 78 The Chair of Management and Economics of Wood Companies (Department of Wood Science and Technology, Biotechnical Faculty) receives the prestigious award of the international asso- ciation WoodEMA Leon Oblak • Gozdno-lesna veriga in podnebne spremembe: prehod v krožno biogospodarstvo . . . . . . . . . . . . 80 Nov raziskovalni program, ki povezuje tri raziskovalne organizacije. Davor Kržišnik in Jožica Gričar • Klub alumnov lesarstva v letu 2022 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 81 Alumni Club Wood Science and Technology in 2022 Katarina Čufar, Boštjan Lesar • Mednarodna delavnica »Manj znane lesne vrste v dendrokronologiji in kulturni dediščini« . . . . 83 International workshop »Less known wood species in dendrochronology and cultural heritage« Maks Merela, Angela Balzano 2 Les/Wood, Vol. 71, No. 1, June 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 Nataša Poklar Ulrih, 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 Tehnični urednik/Technical editor Anton Zupančič, Slovenija / Slovenia, anton.zupancic@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 juniju 2022 v 100 izvodih./Printed in June 2022 in 100 copies. ISSN 0024-1067 (tiskana verzija/printed version) ISSN 2590-9932 (spletna verzija/on-line version) http://www.les-wood.si/ 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 Abstract 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. 1, June 2022 UVODNIK / EDITORIAL Matevž Rudolf Predstojnik Založbe Univerze v Ljubljani / Head of Office, University of Ljubljana Press Revija Les/Wood izhaja pod okriljem Založbe Univerze v Ljubljani Univerza v Ljubljani je s 40.000 študentkami in študenti največja in najstarejša univerza v Sloveniji. Sestavlja jo kar 26 fakultet in akademij in pokriva vsa znanstvena področja. Posledično je bogata tudi njena založniška dejavnost, ki pa je zelo razvejana. Konec študijskega leta 2019/2020, ko je Univerza praznovala 100. obletnico, so se uresničile dolgo- letne želje, da bi Univerza dobila skupno založbo. Nastala je Založba Univerze v Ljubljani (University of Ljubljana Press), ki s svojevrstno organiziranostjo povezuje založniško dejavnost na fakultetah in aka- demijah. Osnova Založbe UL sicer ostaja založniška dejavnost na članicah UL, pomemben korak pa smo naredili z začetkom izdajanja publikacij pod skup- nim imenom Založba UL. Ko bo ta proces v celoti končan, bo šele res razvidno, da je Založba UL ena večjih evropskih univerzitetnih založb, ki letno izda- ja več kot 250 monografij. V okviru Univerze v Ljubljani izhaja tudi 50 mednarodnih znanstvenih revij. Skoraj vse revi- je izhajajo v odprtem dostopu, kar pomeni, da so članki dostopni takoj po izidu posamezne številke. Ker so bile do pred kratkim revije objavljene na naj- različnejših naslovih in platformah, je Založba UL vzpostavila skupni spletni portal Revije UL. Portal temelji na odprtokodnem sistemu Open Journals Systems, ki poleg objave posameznih člankov v ozadju omogoča tudi vse potrebne založniške kora- ke za urednikovanje (elektronsko sprejemanje član- kov, posredovanje člankov recenzentom, oblikoval- cem, lektorjem itd.). Portal je dostopen na naslovu https://journals.uni-lj.si/. Na portalu trenutno gos- tuje 19 revij, objavljenih pa je več kot 6.500 člankov. Ena izmed takih revij je tudi revija Les/Wood, ki od leta 2017 dvakrat letno izhaja z odprtim dos- topom po diamantnem modelu. Revija sicer na- daljuje zapuščino revije Les: revija za lesno gospo- darstvo, ki je neprekinjeno izhajala med leti 1949 in 2013. Revija obravnava širše področje lesarstva in z lesarstvom povezana področja, teme, ki so še kako pomembne za trajnostno naravnan odnos do današnjega sveta. Les je namreč edina obnovljiva surovina, ki jo imamo v Sloveniji v izobilju, zato je še toliko bolj pomembno, da tudi preko znanstvenih člankov podpiramo poglobitev znanj o lesu in lesnih kompozitih ter sodobnih tehnologijah za predelavo in obdelavo lesa, hkrati pa tudi spodbujamo razi- skave o konstruiranju in oblikovanju ter gospodar- jenju z lesom in lesnimi proizvodi. Sedež uredništva revije Les/Wood je na Biotehniški fakulteti Univerze v Ljubljani, z letom 2021 pa je revija začela izhajati pod imenom Založbe Univerze v Ljubljani. Verjame- mo, da bo s tem korakom revija Les/Wood pridobila večjo mednarodno prepoznavnost in tako še okre- pila svojo interdisciplinarno naravnanost. Uredništvu revije Les/Wood na tem mestu izre- kam pohvale za vse opravljeno delo, zaradi katerega revija dosega visoke akademske založniške standar- de. S skupnimi močmi bomo tako še bolj spodbudili globalno izmenjavo znanja in tako pripomogli k bolj trajnostnemu razvoju sodobnega sveta. 4 Les/Wood, Vol. 71, No. 1, June 2022 The journal Les/Wood is published by the University of Ljubljana Press With some 40,000 students, the University of Ljubljana is the largest and oldest university in Slo- venia. It includes 26 faculties and academies, and covers all scientific disciplines. Consequently, its pu- blishing activity is also very rich and wide-ranging. At the end of the academic year 2019/2020, when the University of Ljubljana celebrated its 100th anniversary, a long-held wish came true: that the university would have a single, united publishing house. The University of Ljubljana Press was thus established, joining the publishing activities of the faculties and academies through a unique organi- sational structure. While the basis of the University of Ljubljana Press remains the publishing activities of the faculties, an important step has been taken by starting to publish our publications under the common name of the University of Ljubljana Press. When this process is fully completed, it will become clear that the University of Ljubljana Press is one of the largest university presses in Europe, publishing more than 250 monographs per year. The University of Ljubljana also publishes 50 international scientific journals. Almost all of the journals are open access, meaning that articles are available immediately after the publication of each issue. Since the journals have been published on a variety of websites and platforms, the University of Ljubljana Press has initiated a single web portal for the UL journals. The portal is based on the Open Journals Systems, which also provides all the ne- cessary publishing steps for editors (electronic sub- mission of articles, peer reviewing, etc.). The portal is available at https://journals.uni-lj.si/. The portal currently hosts 19 journals and has published more than 6,500 articles. One of these journals is Les/Wood, which has been published twice a year in the open access dia- mond model since 2017. The journal continues the legacy of Wood: The Journal of the Wood Economy (Les: revija za lesno gospodarstvo), which was pu- blished continuously between 1949 and 2013. The journal publishes original research articles that explore the broad field of wood science and tech- nology, topics that are particularly relevant to a sustainable approach in today's world. Wood is the only renewable resource we have in abundance in Slovenia. Therefore, it is very important to promote knowledge about wood and wood composites, as well as modern technologies for wood processing and treatment, and also to support research in con- struction and design, as well as the management of wood and wood products. The editorial office of Les/Wood is located at the Biotechnical Faculty of the University of Ljubljana and since 2021 the jou- rnal is published under the brand the University of Ljubljana Press. We believe that this step will help the journal gain greater international visibility and thus strengthen its interdisciplinary focus. I would like to congratulate the editors of Les/ Wood for all the work they have done to ensure that the journal achieves the high standards of academic publishing. Together, we will continue to promote the global exchange of knowledge and thus contribute to a more sustainable development of the modern world. 5 Les/Wood, Vol. 71, No. 1, June 2022 THE SYNERGISTIC EFFECT OF MICROWAVE DRYING AND PLASMA SURFACE TREATMENTS ON THE WETTABILITY OF GREEN WOOD SINERGISTIČNI UČINEK MIKROVALOVNEGA SUŠENJA IN OBDELAVE S PLAZMO NA OMOČLJIVOST SVEŽEGA LESA Sauradipta Ganguly 1 , Jure Žigon 2 , Kavyashree Srinivasa 2 , Marko Petrič 2 , Sebastian Dahle 2* UDK 630*829.1:52-726 Received / Prispelo: 19. 11. 2021 Original scientific article / Izvirni znanstveni članek Accepted / Sprejeto: 10. 1. 2022 . Abstract / Izvleč ek Abstract: In spite of being both a one-step solution to several problems associated with woodworking and also energy efficient, the application of microwave (MW) modification in wood research has remained very limited and this promising method has practically no use in wood industries across the globe. Research done so far in this field primarily sheds light on its potential in enhancing wood permeability, treatability and uniform wood drying. While MW treatments are mostly used on wet or green wood, another modification technique, plasma, has potential benefits to synergistically enhance the effects of MW treatment, but so far has not been applied on wet or green wood specimens. This study takes a first step to investigate the effects of plasma treatments (PT) on green wood specimens, as well as combinations of MW and plasma treatments. As a preliminary study, the methodology focuses on water contact angle measurements, since these are most commonly used as indicators for surface modifications in industrial applications. An exponential time dependence was found for the contact angle on the investigated samples of Norway spruce (Picea abies Karst.). Initial contact angles after droplet deposition increased due to drying and migration of organic molecules during treatments. In comparison with the literature, the effect of plasma was significantly less pronounced on wet wood specimens. The initial contact angles showed the lowest statistical variations after MW treatment, whereas plasma increased inhomogeneities. The final contact angles on treated specimens was lowest for PT-only specimens as well as specimens treated with plasma after MW. In contrast to the initial contact angles, the final contact angles showed the lowest variations after PT. Wetting rates were insignificantly improved by plasma, with reduced statistical variations after all treatments. Keywords: Norway spruce wood, Wood drying, Microwave processing, Gliding arc plasma Izvleček: Kljub temu, da je uporaba mikrovalov za modifikacijo lesa energetsko učinkovita in obetavna enostopenjska rešitev za številne probleme, povezane z obdelavo lesa, je ta tehnologija v raziskavah lesa ostala zelo omejena in se v lesni industriji po vsem svetu praktično ne uporablja. Dosedanje raziskave na tem področju osvetljujejo predvsem potencial te metode pri izboljšanju permeabilnosti lesa, kurativne zaščite lesa in enakomernega sušenja lesa. Medtem ko se obdelava z mikrovalovi večinoma uporablja na svežem lesu, izkazuje tehnika obdelave lesa s plazmo potencialne koristi za sinergistično izboljšanje učinkov obdelave z mikrovalovi, vendar se doslej plazma še ni uporabljala za obdelavo svežega lesa. Ta študija je prvi korak k raziskovanju učinkov plazemske obdelave na vzorcih svežega lesa ter kombinacije mikrovalovne in plazemske obdelave. Kot preliminarna študija se osredotoča na meritve stičnega kota kapljic vode, saj se metoda uporablja kot indikator učinkovitosti površinske obdelave tudi v industriji. Na raziskanih vzorcih smrekovine (Picea abies Karst.) je bila ugotovljena eksponentna odvisnost stičnega kota od trajanja omočenja. Začetni stični kot po nanosu kapljic vode se je povečal zaradi sušenja lesa in migracij organskih molekul na površino lesa. V primerjavi z navedbami iz literature je bil učinek plazme na svežih vzorcih lesa bistveno manj izrazit. Začetni stični kot je imel najmanjšo statistično variabilnost po obdelavi z mikrovalovi, medtem ko je plazma povečala nehomogenost. Končni stični kot je bil najnižji pri vzorcih, ki so bili obdelani samo s plazmo, kot tudi pri vzorcih, obdelanih s kombinacijo mikrovalov in plazme. V nasprotju z začetnim stičnim kotom je končni stični kot pokazal najmanjšo spremembo po obdelavi s plazmo. Stopnja omočitve je bila s plazmo neznatno izboljšana, z zmanjšano statistično variabilnostjo po vseh obdelavah. Ključne besede: les navadne smreke, sušenje lesa, mikrovalovna obdelava, drsna obločna plazma Vol. 71, No. 1, 5-14 DOI: https://doi.org/10.26614/les-wood.2022.v71n01a01 1 Wood Preservation Discipline, Forest Products Division, Forest Research Institute, Dehradun 248006, India 2 Department of Wood Science and Technology, Biotechnical Faculty, University of Ljubljana, Jamnikarjeva 101, 1000 Ljubljana, Slovenia * e-mail: sebastian.dahle@bf.uni-lj.si 6 Les/Wood, Vol. 71, No. 1, June 2022 Ganguly, S., Žigon, J., Srinivasa, K., Petrič, M., & Dahle, S.: Sinergistični učinek mikrovalovnega sušenja in obdelave s plazmo na omočljivost svežega lesa 1 INTRODUCTION 1 UVOD Frequent availability, versatility, aesthetics and many other favourable characteristics made wood the most important biomass derived mate- rial for a varied range of end uses. The diverse na- ture of several wood species has resulted in their specific uses, which in the present day is difficult to maintain due to the depleting supplies of tim- ber resources worldwide. Wood modification is the most suitable solution to this, where using various methods secondary and non-durable wood can be made suitable for specific uses and its sustainability thus ensured for longer periods. Among these tech- niques, thermal and chemical modifications of tim- ber have become relatively common (Hansmann et al., 2005; Despot et al., 2008; Esteves & Perei- ra, 2009; Sefc et al., 2009; Hom et al., 2020; Treu et al., 2020) across the globe due to their ease of processing and satisfactory commercial and labora- tory performance. However, extensive energy con- sumption and the utilisation of non-environmen- tally-friendly chemicals are the two most common drawbacks associated with these methods. In the last few decades treating and modifying wood with microwaves (MW) has become more popular (Kol & Çayır, 2021) in the niche research domain of wood modification with a variety of use cases (Oloyede & Groombridge, 2000; Torgovnikov & Vonden, 2010; Balboni et al., 2018; Samani et al., 2019; Weng et al., 2021). For timber drying, for example, it has been shown to have a lower level of energy consumption (Brodie, 2010; Sethy et al., 2016) in comparison to the conventional methods, with an increased drying rate of timber and subsequently reduced the drying time (Awoyemi, 2004; Gamben et al., 2005). Several studies demonstrated strongly increased liquid permeability and preservative up- take in refractory and moderately refractory timber species after several levels of MW modification and pre-treatment (Liu et al., 2005; Treu & Gjolsjo, 2008; Torgovnikov & Vinden, 2009; Ramezanpour et al., 2015; Xu et al. 2015; Hermoso & Vega, 2016; Samani et al., 2019; Ganguly et al., 2021a). This was shown to originate primarily in the rupture of weak anatomical elements leading to the generation of micropores and microcracks (Mekhtiev & Torgov- nikov, 2004; Terziev et al., 2020; Weng et al., 2020; Ganguly et al., 2021b) as well as an increment in pore diameters along with destruction of pit mem- branes and damage to cell walls. However, this change in the wood microstructure upon exposure to higher intensities of MW often compromises the strength of timber (He et al., 2014), although there have been cases where the reduction is not statistically significant (Kol & Çayır, 2021). During the MW treatment of wooden materials, the build- up of internal gas pressure from vapourized water and volatile organic compounds needs to be con- sidered, as it can increase permeability through mi- crocracks in the cell walls (Hong-Hai et al., 2005) or negatively impact the workpiece’s mechanical properties through material cracking (Ouertani et al., 2015) and other issues related to inhomogene- ous rises in temperature (Bartoli et al., 2019). As such, the optimization of the treatment parameters is of utmost importance when using MW for wood modification. Another kind of modification technique with the potential to increase the permeability of wood and uptake of liquids is the use of non-thermal plas- mas (Žigon et al., 2018; Žigon et al., 2020a; Wascher et al., 2021). Plasma treatments (PT) have been used to improve wetting and uptake of both water and non-polar liquids (Rehn et al., 2003; Žigon et al., 2018; Haase et al., 2019), to improve coatings’ adhesion strengths (Riedl et al., 2014) and to en- hance the performance of adhesive joints (Žigon et al., 2020b; Krapež Tomec et al., 2021). Moreover, PT have been reported to remove volatile organic compounds (VOCs) and moisture from the parts of wooden specimens near the surface (Avramidis et al., 2016; Dahle et al., 2020a). The main impact of PT, however, is yielded through chemical modifica- tion of the wood’s lignin and cellulose (Klarhöfer et al., 2010). In contrast to MW treatments depositing a larger proportion of energy inside the workpiece due to the drying gradient, PT almost exclusively modifies the workpiece’s surface, reportedly with a maximum modification depth of ca. 3300 nm (Král et al., 2015). While the majority of research on the PT of wood over the past two decades uti- lizes dielectric barrier discharge (DBD) plasma de- vices (Žigon et al., 2018), the gliding arc jet plasma technology is much more widespread across most industrial fields and has been successfully utilized on wood and wood-based materials before (Mela- 7 Les/Wood, Vol. 71, No. 1, June 2022 Ganguly, S., Žigon, J., Srinivasa, K., Petrič, M., & Dahle, S.: The synergistic effect of microwave drying and plasma surface treatments on the wettability of green wood mies, 2014; Hämäläinen & Kärki, 2013). Therefore, this study focuses on gliding arc jet PT. In this study, we provide the first results on the combined effects of MW and PT to modify wetting and liquid uptake. In addition to this, the study ex- pands the insights from the PT of dried or condi- tioned wood specimens to green (i.e. wet) wood, which is most commonly used for MW modifica- tions. The impact of combined modifications of green Norway spruce wood using PT either before or after MW is evaluated against the effect of single modifications of only PT or MW, as well as unmodi- fied control specimens. These relations are investi- gated through water contact angle (WCA) measure- ments, as these are the most common indicator for applied surface processes that represent surface functionality, chemistry, morphology, roughness and so on (Kalnins et al., 1988; Boehme & Hora, 1996; Papp & Csiha, 2017). 2 MATERIALS AND METHODS 2 MATERIALI IN METODE Norway spruce (Picea abies Karst.) wood, 35 years old, cut in the north-eastern part of Slo- venia, was used in this study. Conversion of the logs to planks was performed at a local sawmill. Processing (sawing, planing) of the samples was done three weeks after cutting the tree. Separate sets of samples, mostly semi-radial in orientation, were prepared from the heartwood portions. The initial moisture content (IMC) was deter- mined by the gravimetric method according to the EN 13183-1 standard for 10 randomly select- ed parallel heartwood samples, yielding an IMC of 27–38 %. The dimensions of the samples were l×w×h = 5×2.5×1.5 cm³ for all treatment combina- tions. The treatment of wood with microwaves (MW) was carried out using a MW oven (Mod- el: M020MW, Gorenje, Velenje, Slovenia) with a frequency of 2.45 GHz and a maximum output of 700 W at a power consumption of 1500 W. One en- ergy level of 1260 MJ/m ³ was applied to the wood samples for all the treatments involving MW in the study. The duration of MW irradiation was 36 s. The parameters of MW treatments were defined based on MW power and volume of the samples as pro- posed by (Kol & Çayir, 2021) and our preliminary experiments. After MW treatment, the samples were cooled in a desiccator at room temperature and subjected to further analysis. A gliding arc plasma jet device was used to treat the specimens’ surfaces as depicted in Figure 1. The device consists of a computerized numerical control (CNC) positioning system (SainSmart Gen- mitsu CNC Router 3018 DIY , Vastmind LLC, Dela- ware, USA) moving the head with attached plasma jet in three directions. Copper electrodes (ROLOT 605, Rothen-berger Werkzeuge GmbH, Kelkheim, Germany) are mounted to a 42 mm diameter cy- lindrical epoxy (Herpelin Epoksi 1000, Amal d.o.o., Ljubljana, Slovenia) nozzle with an 8 mm diameter centred hole as the gas channel. The gas is sup- plied from an internal compressor (Hailea ACO 208, Guangdong Hailea Group Co., Ltd., Guangdong, Chi- na) at a flow rate of approx. 35 l/min. The plasma discharge is generated between the two electrodes within the nozzle using a commercial high voltage module (ZVS_Driver_20A_kit_AC, Voltagezone Electronics e.U., Graz, Austria) operated at an input voltage (20 V) and current (5 A) from a combination of a commercial switch-mode power supply (Joylit S-240-24, Shenzhen Zhaolan Photoelectric Technol- ogy Ltd., Shenzhen, China) and a digital power sup- ply control unit (RD DPS5020 BT/USB, Hang-zhou Ruideng Technology Co., Ltd., Zhejiang, China). The afterglow of the gliding arc jet extends approx. 2 cm out below the nozzle. During the treatment process, the specimens were placed on the stage with a gap distance between the nozzle outlet and sample surface of 10 mm. The entire surfac- es of the samples were treated by the plasma jet scanning in seven lines of 80 mm length, offset by 5 mm, thus covering an area of 80 mm × 30 mm at a moving speed of 60 mm/min. The power consump- tion of the plasma device is 57 W for the electron- ic components (SainSmart controller, Raspberry Pi 4B with touchscreen, and power supply standby consumption), up to 14 W for the stepper motor movements, 18 W for the compressor unit and up to 100 W for the plasma discharge, yielding an overall power consumption during the treatment of up to 189 W. The entire construction details are available in Dahle et al. (2020b). The G-code file is provided together with the raw and analysed data of this publication in Dahle et al. (2021). 8 Les/Wood, Vol. 71, No. 1, June 2022 Ganguly, S., Žigon, J., Srinivasa, K., Petrič, M., & Dahle, S.: Sinergistični učinek mikrovalovnega sušenja in obdelave s plazmo na omočljivost svežega lesa WCA were measured using a Theta optical goniometer (Biolin Scientific Oy, Espoo, Finland). Apparent WCAs were evaluated by Young–Laplace analysis using proprietary software (OneAttension version 2.4 [r4931], Biolin Scientific). For each sam- ple type, three specimens were prepared. On each specimen, three droplets were automatically ana- lysed within 63 s, with 1.7 images per second. The measurement started immediately after the first contact of the drop with the surface of the sample. No stable drop shape or equilibrium was achieved within a reasonable time, as opposed to typical findings on dried wood samples (c.f. Kalnins et al., 1988), thus an analysis of time-dependent data was carried out. The data was analysed using OriginPro 2018G 64bit SR1 (OriginLab Corp., Northampton, MA, USA) by numerical fitting a first order expo- nential decay according to eq. (1), thus yielding the initial contact angles and the subsequent wetting rates. The function was chosen empirically due to the measured data strongly deviating from other published slopes, such as the linear regression with the square root of time reported by Boehme and Hora (1996). yAexp xt y =− + () 11 0 */ (1) Figure 2 depicts the curve according to eq. 1 as a bold black line, with the corresponding pa- rameters indicated by coloured lines. Parameter y 0 , shown as dashed blue horizontal line, represents the value after indefinitely long equilibration times (t → ∞). Due to penetration into the wood, this val- ue cannot be physically reached on real specimens, but is suitable as a quantitative indicator for the Figure 1. Gliding arc jet device on a CNC positioning stage. Slika 1. Naprava z drsnim obločnim plazemskim curkom in računalniško krmiljeno pozicionirno mizico. Figure 2. Example curve with exponential decay ac- cording to equation 1. Slika 2. Primer eksponentno pojemajoče krivulje po enačbi 1. 9 Les/Wood, Vol. 71, No. 1, June 2022 Ganguly, S., Žigon, J., Srinivasa, K., Petrič, M., & Dahle, S.: The synergistic effect of microwave drying and plasma surface treatments on the wettability of green wood Figure 3. Example WCA measure- ment and exponential curve fit for MW-treated specimens. Slika 3. Primeri časovnega spre- minjanja izmerjenega stičnega kota vode in prilagojene ekspo- nentne krivulje za vzorce, obdela- ne z mikrovalovi. droplet’s behaviour and this is referred to as the final WCA. Parameter A 1 , shown as vertical green arrow line, represents the difference between the contact angle at t 0 = 0s and the value for t → ∞. The intuitive value discussed in the manuscript, howev- er, is the WCA directly upon the first contact of the droplet with the specimen’s surface (t 0 = 0s), which is given by A 1 +y 0 , shown as dashed red horizontal line, and this is referred to as the initial WCA. The third parameter t 1 , shown as a dashed brown verti- cal line, represents the time, after which the value of the function has fallen from F(0s)=(A 1 +y 0 ) down to F(t 1 )=(A 1 /e+y 0 ), i.e. by approx. 63.2% of A 1 . The smaller parameter t 1 , the faster the droplet spreads across the surface, i.e. the higher the wetting rate. Parameter t 1 is thus referred to as the time con- stant of wetting. 3 RESULTS AND DISCUSSION 3 REZULTATI IN RAZPRAVA Figure 3 shows the measurement data and corresponding fits of exponential decay functions (eq. 1) on different spots of two MW-treated spruce specimens. The time-dependent progression of the measured WCAs varied strongly between individu- al points on all specimens regarding the initial con- tact angles directly after droplet deposition and the slope of the curve (i.e. time-dependent wetting), as well as the final WCA. Moreover, all measurements show deviations from the continuous curvature be- yond the statistical variations of individual values. Figure 4 shows a statistical analysis of the final WCA as given by parameter y 0 in eq. 1. The results are displayed such that the small square marks in- dicate the statistical mean value averaged over all measurements and specimens of the correspond- ing sample type, the coloured boxes enclose the 25%-75% medians, and the metering lines indicate 1.5 IQR (interquartile range), whereas outliers are marked by black diamonds. It is noteworthy that the smallest final WCAs were determined for the untreated control speci- mens with an average of 33.1°, which can be ac- counted for by the high IMC. Both MW and PT yield a drying of the specimens or their surfaces, thereby reducing the proportion of polar molecules with- in the surface. The highest final WCAs were found for specimens directly after MW treatment with an average of 48.4° and 48.6° for MW-only and MW after PT, respectively. This effect might be due to the drying, which is known to change the charac- ter of wood from hydrophilic to hydrophobic, with surfaces becoming more hydrophobic particularly at increased temperatures due to the migration of extractives to the surface (c.f. Šernek, 2002). Direct- ly after PT, the average final WCA amounts to 33.1° and 44.5° for plasma-only and PT after MW, respec- 10 Les/Wood, Vol. 71, No. 1, June 2022 Ganguly, S., Žigon, J., Srinivasa, K., Petrič, M., & Dahle, S.: Sinergistični učinek mikrovalovnega sušenja in obdelave s plazmo na omočljivost svežega lesa Figure 4. Statistical analysis of final WCA on differ- ently treated specimens. Slika 4. Statistična analiza končnega stičnega kota vode s površino lesa na različno obdelanih vzorcih. Figure 5. Statistical analysis of initial WCA on differ- ently treated specimens. Slika 5. Statistična analiza začetnega stičnega kota vode s površino lesa na različno obdelanih vzorcih. tively. Although this presents a reduction of the WCA by PT again after MW, the WCA does increase in all cases compared to the untreated control spec- imens. This indicates a stronger effect of drying and evaporation of VOCs towards larger WCAs than the impact of PT through the chemical production of additional polar groups on the structural constit- uents of the wood material. This increase of WCA on green wood after PT is contrary to most pub- lished literature (c.f. Žigon et al., 2018) and might not only be related to a drying of the outermost surface layers through enhanced evaporation of moisture induced by the plasma, but it might well relate further to a change in plasma-chemical re- actions due to the water vapour above the wood surface. From various literature sources, it is well known that the plasma chemistry that occurs here changes with varying humidity levels in non-ther- mal air plasmas. In particular, the amount of oxy- gen radicals and consequently the production rate of ozone is reduced with the increasing presence of water molecules in the atmosphere, mainly via two effects: on the one hand, oxygen radical production and hydroxyl radical generation are competitive processes, both originating from dissociation after resonant energy transfer from metastable excit- ed nitrogen molecules. On the other hand, water molecules act as scavengers for oxygen radicals to form hydroxyl radicals. Both mechanisms lead to the reduced production of ozone and the corre- spondingly increased production of hydroxyl radi- cals, which further contribute to the formation of nitric oxide (Herron & Green, 2001; Prysiazhnyi et al., 2012). Moreover, these effects increase with the gas temperature (Sakiyama et al., 2012) and are thus more pronounced, for example, in gliding arc plasmas than in DBDs. These effects need to be further verified, e.g. by future measurements with Optical Emission Spectroscopy and X-ray Photo- electron Spectroscopy, in order to provide insights into both the plasma discharge and their effect on the yielded chemical changes on the surface. From the final WCA results, it is also noteworthy that the PT decreases statistical variations compared to the control specimens in terms of standard deviation, 1.5 IQR, and the ranges from first to third quartile medians. In contrast to that, standard deviation and 1.5 IQR are increased significantly by MW treatment, both on the untreated control and the previously plasma-treated specimens. Figure 5 shows a statistical analysis of the ini- tial WCA after droplet deposition as given by (y 0 +A 1 ) with parameters from eq. 1. The untreated control specimens exhibit the lowest initial WCA upon con- tact with the water droplet with an average of 48.7°. Both MW and PT increased the initial WCA, yielding average values of 91.6° and 89.5° for MW-only and PT-only, respectively. Notably MW-only significant- 11 Les/Wood, Vol. 71, No. 1, June 2022 Ganguly, S., Žigon, J., Srinivasa, K., Petrič, M., & Dahle, S.: The synergistic effect of microwave drying and plasma surface treatments on the wettability of green wood Figure 6. Statistical analysis of the time constant for wetting on differently treated specimens. Slika 6. Statistična analiza časovne konstante omo- čenja na različno obdelanih vzorcih. ly reduced the standard deviation, but increased the 1.5 IQR, whereas PT-only strongly increased both indicators of statistical variation. This can like- ly be attributed to the heterogeneous nature of the PT due to its filamentary structure and a high- er intensity for denser or more conductive parts of the surface, such as on latewood as compared to earlywood. Combined treatments yield compara- ble initial WCAs with average values of 77.3° and 74.1° for PT+MW and MW+PT, respectively. For both combined treatments, the standard deviation and 1.5 IQR are comparable, whereas the range be- tween first and third quartile medians is lower for the specimens treated first with plasma and subse- quently by MW. Figure 6 shows a statistical analysis of the time constant t 1 as defined in eq. 1, representing the change in WCA over time as the droplet spreads across the sample surface, i.e. the wetting rate, whereas the concurrent penetration does not im- pact the measured WCA. The MW-only treated specimens exhibit an average wetting time of 19 s, equal to the untreated control specimens. The PT-only specimens show a lower wetting time of 15 s, whereas the combined treatments yield in- creased wetting times of 20 s and 23 s for PT follow- ing MW and MW after PT, respectively. However, all these values fall into each other’s standard devia- tion and 1.5 IQR, and thus are not statistically sig- nificant. It does appear, though, that all MW-treat- ed specimens show the lowest ranges between first and third quartile medians, whereas PT further re- duces the 1.5 IQR. This might be an indication that the high degree of variation could be correlated with the moisture content at the wood surface. 4 CONCLUSIONS 4 SKLEPI The study confirmed the effects of PT and MW as well as combinations of the two on the initial WCA after droplet deposition, the final WCA, and the time constant of the wetting process for green or wet wood. The final WCA was negatively affected by all treatments, yielding highest values for MW-on- ly treatments. It was theorized that this negative effect is due to drying of the specimens, which is more strongly pronounced for MW than for PT treatments. Additional measurements are foreseen in the future to investigate the relation of the dif- ferent methods’ drying effects with regard to the measured contact angles. Combinations of MW and PT combinations might indicate a negative ef- fect of MW on a previously plasma-treated surface, and hence suggests an ideal treatment procedure of first MW followed by PT to utilize complementa- ry or synergistic effects. The initial WCA upon droplet contact was in- creased after all of the treatments as compared to the untreated control specimens. Among the different treatment procedures, both combined treatments showed ideal and generally comparable results, regardless of the sequence of PT and MW. The change in wetting time constants was not statistically significant, but might indicate PT as the preferred final step of surface preparation, which should be conducted only after other bulk tech- niques such as modification via MW. Overall, the MW and PT results indicate syn- ergistic effects, but experiments using complemen- tary spectroscopic techniques will be required for further insights. The specific utilization of electric energy per specimen volume amounted to 2700 MJ/m³ for MW, 5645 MJ/m³ for PT and 8345 MJ/m³ for com- bined MW+PT and PT+MW treatments. It should be noted that the use of PT as a surface treatment 12 Les/Wood, Vol. 71, No. 1, June 2022 Ganguly, S., Žigon, J., Srinivasa, K., Petrič, M., & Dahle, S.: Sinergistični učinek mikrovalovnega sušenja in obdelave s plazmo na omočljivost svežega lesa strongly increases the energy efficiency for larger specimen volumes, thus being more favourable for industrial applications than small-scale laboratory experiments seem to indicate. However, the results clearly show that PT is not energy-efficient in terms of drying wood material, but its energy utilization and CO 2 equivalent should be evaluated in com- parison to the surface finishing techniques and the corresponding materials replaced by PT. SUMMARY 5 POVZETEK Stični kot kapljic vode s površino lesa ni pokazal odvisnosti v obliki kvadratnega korena od trajanja omočitve, kot sta prej poročala Boehme in Hora (1996), tako da je bila za prileganje izmerjenim podatkom uporabljena eksponentno pojemajoča funkcija (glej eq. 1). Navidezni končni ali ravnotežni stični kot (y 0 ) se je močno povečal pri vzorcih, ob- delanih z mikrovalovi, ob hkratnem povečanju va- riabilnosti. Obdelava s plazmo je povzročila rahlo povečanje stičnega kota, vendar zmanjšanje sta- tistične variabilnosti. Kombinacije obdelave lesa s plazmo in mikrovalovi so povzročile manjše po- večanje stičnega kota. V primerih, ko se je obdela- va s plazmo izvajala na koncu, pa se je statistična variabilnost ponovno zmanjšala. Zmanjšan učinek obdelave s plazmo v primerjavi z navedbami v lite- raturi je verjetno posledica spremenjene kemijske sestave površine lesa. Iz svežega lesa pri obdelavi s plazmo prihaja do izhajanja vodne pare, kar vodi do zmanjšane tvorbe ozona in kisikovih radikalov, vendar povečane tvorbe hidroksilnih radikalov in dušikovega oksida. Začetni stični koti vode neposredno po odlaga- nju kapljice na površino lesa (A 1 +y 0 ) so bili največji v primerih, ko smo les posamično obdelali bodisi z mikrovalovi ali plazmo. Kombinacija obdelave z mikrovalovi in plazmo je povzročila nižji začetni stični kot, ki je bil primerljiv ne glede na vrstni red obdelave. Statistična variabilnost začetnega stične- ga kota je bila zmanjšana na vzorcih, obdelanih le z mikrovalovi, obdelava s plazmo pa je le-to močno povečala. To je verjetno posledica dejstva, da smo les obdelali z mikrovalovi v surovem, t.j. svežem stanju, kar je s tokom vlage na površino lesa omo- gočilo tudi migracijo organskih snovi, zlasti slad- korjev in ekstraktivov, s tem pa povzročilo homo- genizacijo površine. V nasprotju s tem plazemska obdelava deluje heterogeno z večjo intenzivnostjo na območjih z večjo gostoto ali višjo električno pre- vodnostjo, kot je kasni les v primerjavi z ranim le- som, tako da plazma prispeva k povečanju kemične nehomogenosti površin. Časovno konstanto omočenja, določeno v ek- sponentno pojemajočem modelu, najmočneje po- veča obdelava z mikrovalovi, medtem ko so vzorci, obdelani s plazmo, pokazali krajši čas omočenja. Časovna konstanta omočenja je podobna za neob- delane vzorce in vzorce, obdelane z mikrovalovi, medtem ko so vzorci, obdelani s plazmo, pokazali krajši čas omočenja, vzorci, obdelani s kombinaci- jo plazme in mikrovalov, pa so imeli podaljšan čas omočenja. Statistična variabilnost je bila najnižja pri vzorcih, obdelanih najprej z mikrovalovi in nato s palzmo. Vendar pa je bila statistična variabilnost na splošno tako velika, da ugotovljene razlike v kon- stanti omočenja niso statistično značilne. Na splošno rezultati obdelave z mikrovalovi in plazmo kažejo na sinergijske učinke, vendar bodo za podrobnejšo interpretacijo rezultatov potrebni poskusi z uporabo komplementarnih spektroskop- skih tehnik. Specifična poraba električne energije na pro- stornino vzorca znaša 2700 MJ/m³ za mikrovalovno obdelavo, 5645 MJ/m³ za plazemsko obdelavo in 8345 MJ/m³ za kombinirano obdelavo z mikrovalo- vi in plazmo. Treba je opozoriti, da plazma kot po- vršinska obdelava močno poveča energijsko učin- kovitost za večje količine vzorcev, kar je ugodno za industrijsko uporabo, kot nakazujejo majhni labo- ratorijski poskusi. Poleg tega rezultati jasno kažejo, da plazemska obdelava ni energetsko učinkovita za sušenje lesnega materiala, vendar je treba izrabo energije in ekvivalent CO 2 ovrednotiti v primerjavi s tehnikami površinske obdelave in ustreznimi mate- riali, ki jih plazma nadomesti. 13 Les/Wood, Vol. 71, No. 1, June 2022 Ganguly, S., Žigon, J., Srinivasa, K., Petrič, M., & Dahle, S.: The synergistic effect of microwave drying and plasma surface treatments on the wettability of green wood ACKNOWLEDGEMENTS ZAHVALA The authors acknowledge the financial sup- port from the Slovenian Research Agency (research program funding No. P4–0015, “Wood and ligno- cellulose composites”). Avtorji se zahvaljujemo Javni agenciji za razi- skovalno dejavnost (ARRS), ki financira programsko skupino P4-0015. 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Enhancement of strength of adhesive bond between wood and metal using atmospheric plasma treatment. Cellulose, 27, 6411-6424. DOI: https://doi. org/10.1007/s10570-020-03212-8 15 Les/Wood, Vol. 71, No. 1, June 2022 SORPTION PROPERTIES OF WOOD IMPREGNATED WITH THE FIRE RETARDANT BURNBLOCK SORPCIJSKE LASTNOSTI LESA, IMPREGNIRANEGA Z OGNJEZADRŽEVALNIM SREDSTVOM BURNBLOCK Miha Humar 1* , Boštjan Lesar 1 , Davor Kržišnik 1 UDK 630*843:630*812.7 Received / Prispelo: 21. 12. 2021 Original scientific article / Izvirni znanstveni članek Accepted / Sprejeto: 14. 2. 2022 . Abstract / Izvleč ek Abstract: The sorption properties of wood have a characteristic influence on some of its properties, such as the mechanical properties and susceptibility to fungal decay. Moist wood is more susceptible to fungal decay, and wood is often impregnated in order to protect it from fungal decomposition, photodegradation or fire. In particular, inorganic salts affect the sorption properties of wood. For this purpose, the sorption properties of Norway spruce wood impregnated with Burnblock refractory (uptake 38 kg/m³) were investigated. The microscopic analysis confirmed the presence of crystals of this in the cell lumina of wood tissue. Sorption properties were determined using an instrument capable of dynamic vapour sorption (DVS) assessment. DVS analysis confirmed that the sorption properties of impregnated spruce wood are comparable to those of non-impregnated spruce wood. However, the higher hysteresis at higher relative humidity is probably due to the presence of crystals in the cell lumina. Keywords: fire retardants, Burnblock, wood, sorption properties, laser confocal microscopy Izvleček: Sorpcijske lastnosti lesa imajo značilen vpliv na nekatere njegove lastnosti. V največji meri vplivajo na mehanske lastnosti in dovzetnost lesa na glivni razkroj. Vlažnejši les je bolj dovzeten za glivni razkroj, zato ga pred glivnim razkrojem, fotodegradacijo ali gorenjem pogosto impregniramo. Predvsem anorganske soli vplivajo na sorpcijske lastnosti lesa. S tem namenom smo preiskali sorpcijske lastnosti smrekovine, impregnirane z ognjezadrževalnim sredstvom Burnblock (navzem 38 kg/m³). Mikroskopska analiza je potrdila prisotnost kristalov sredstva v celičnih lumnih lesnega tkiva. Sorpcijske lastnosti smo določili z opremo, ki vrednoti dinamično sorpcijo vodne pare (DVS). DVS analiza je potrdila, da so sorpcijske lastnosti impregniranega smrekovega lesa primerljive s sorpcijskimi lastnostmi neimpregnirane smrekovine. Večja histereza pri višjih relativnih zračnih vlažnostih je verjetno posledica prisotnosti kristalov anarganskih soli, ki so se izločili v celičnih lumnih po impregnaciji. Ključne besede: ognjezadrževalna sredstva, Burnblock, les, sorpcijske lastnosti, laserska konfokalna mikroskopija 1 INTRODUCTION 1 UVOD Wood is hygroscopic due to its specific chem- ical composition and large internal surface area. Therefore, the moisture content of wood oscillates depending on the varying climatic conditions. Un- der stable conditions, wood reaches hygroscopic equilibrium or equilibrium moisture content (EMC). The interactions between wood and water have been studied scientifically for more than a centu- ry (Engelund et al., 2013). The moisture content of wood has a significant effect on some relevant properties, especially the mechanical properties (Gerhards, 1982) and service life of wood used out- doors (Meyer et al., 2016). Fungi can decompose wood if the moisture content is above a certain limit. The moisture content of wood must be high enough to promote the flow path for the reaction products of the enzymes, but low enough to pre- vent waterlogging. A wide variety of data on this is available in the literature. In the first set of data, it is indicated that the MC limits for fungal decay de- Vol. 71, No. 1, 15-22 DOI: https://doi.org/10.26614/les-wood.2022.v71n01a02 1 Univerza v Ljubljani, Biotehniška fakulteta, Jamnikarjeva 101, 1000 Ljubljana, SLO * e-mail: miha.humar@bf.uni-lj.si 16 Les/Wood, Vol. 71, No. 1, June 2022 Humar, M., Lesar, B., & Kržišnik, D.: Sorpcijske lastnosti lesa, impregniranega z ognjezadrževalnim sredstvom Burnblock pend predominantly on the fungal species. For ex- ample, Schmidt (2006) reported that the minimum MC of wood was 25% for Coniophora puteana and Serpula lacrymans and 30% for Fibroporia vaillantii and Gloeophyllum trabeum. However, recent data suggest that the limiting moisture content for fun- gal growth depends on the wood species and fun- gal species studied. For example, the limiting mois- ture content for C. puteana growth on thermally modified Scots pine (Pinus sylvestris L.) sapwood is 12.1%, while the limiting moisture content for fungal decay on the same species of wood is 24.4% (Meyer et al., 2016). Similar to wood-decaying fungi, MC has a sig- nificant effect on the growth and development of sap stain fungi. Sap stain fungi are mainly associat- ed with Ascomycetes and Fungi imperfecti, and are characterised by the pigmentation of the hyphae walls, which leads to discolouration of the wood. Suitable conditions for the growth and reproduc- tion of the various mould and sap stain fungi vary. Some thrive at relatively low air relative humidity (RH = 75%), while most fungi require higher RH lev- els and consequently higher wood MC for optimal growth. Different building materials have different susceptibilities to mould growth (Isaksson et al., 2010). The relationship between the EMC and RH is expressed by sorption isotherms obtained by progressive equilibration in the adsorption or de- sorption process. Differences in hygroscopic and sorption isotherms result from the wood species, chemical composition of the wood, the amount of microcracks in the cell walls, density, possible hydrothermal and chemical treatment, and stress conditions (Hartley et al., 1992; Willems, 2018). Sorption isotherms can be divided into three regions. The first represents the EMC from an abso- lutely dry state to the equilibrium state reached at RH between 20% and 30% (Mitchell, 2018). In this interval, the adsorption of water molecules con- tinues gradually until the outer surface of the cell wall is completely covered by a water monolayer. The wood MC changes more rapidly in the upper part of the region, but slows as it approaches a dry state (Lesar et al., 2009). The second region begins when the first layer is saturated. The adsorption of water molecules on the first layer and the result- ing formation of additional layers is a feature of this region, and the isotherms here are quasi-lin- ear (Mangel, 2000). In the third region, capillary condensation of water occurs in microcapillaries. Water molecules form large groups, while the bonds between hydroxyl groups and the first layer of water molecules become weaker, and thus the water molecules can move in clusters (Khali & Ra- wat, 2000). The water concentration in this region is sufficient for liquid water to form in the pores by capillary condensation, so the microcapillary water forms a continuous phase. In the third hygroscopic region, sorption properties are also influenced by low-molecular secondary heartwood compounds such as polyphenols (flavonoids, lignans, tannins), biocides (boric acids) and fire retardants (Blahovec & Yanniotis, 2008). As mentioned earlier, the hygroscopic proper- ties of wood can be affected by various treatment processes, like the use of wood biocides and fire re- tardants. Wood impregnated with various inorgan- ic salts is usually more hygroscopic than untreated wood, especially at high RH. The increase in EMC of such wood depends on the chemicals used, re- tention, and wood species (White & Dietenberger, 2010). The EMC of impregnated wood and the ef- fects of preservative retention on the equilibrium point are still unknown. High EMC is problematic because it promotes leaching of active ingredients, corrosion of metals, and the creation of favourable conditions for the growth of fungi and especially moulds, and presents difficulties in surface treat- ment and gluing of moist wood (Lesar et al., 2009). In this study, the sorption properties of wood im- pregnated with the fire retardant Burnblock were investigated throughout the hygroscopic range dur- ing the adsorption and desorption process. 2 MATERIAL AND METHODS 2 MATERIALI IN METODE The analysis was carried out on wood treat- ed with fire-retardant, and specifically on Norway spruce (Picea abies (L.) Karst.) planks treated with Burnblock (Burnblock, København, Denmark) in a commercial impregnation plant using the full cell impregnation method. Five planks were delivered. The cross-section of the planks was approximately 23 mm × 100 mm and length 200 mm. The reten- tion of Burnblock was 38 kg/m³. Burnblock is made 17 Les/Wood, Vol. 71, No. 1, June 2022 Humar, M., Lesar, B., & Kržišnik, D.: Sorption properties of wood impregnated with the fire retardant Burnblock of ingredients that can be found in nature and are considered environmentally friendly. Treated wood is biodegradable and has no adverse environmental effects (Medved et al., 2019). Five parallel samples were conditioned at laboratory conditions (21 °C; RH 65%), then measured and weighted. The nomi- nal density of the wood was then calculated. Microscopic analysis was performed on cross-sections of the treated wood. The outer 6 mm of the wood that was fully impregnated with the fire retardant was analysed. Microscopic anal- ysis was performed using a confocal laser scanning microscope (Olympus OLS50-BSW, Tokyo, Japan) and a digital microscope (Olympus DSX1000, To- kyo, Japan). The surface was planed with a stainless steel blade. The MC of the wood was approximate- ly 12%. Dynamic water vapour sorption of treated and native (i.e. reference, non-treated) samples was performed using a gravimetric dynamic sorption analyser (DVS Intrinsic, Surface Measurement Sys- tems Ltd., London, UK). Samples were ground and homogenised into fractions smaller than 1 mm pri- or to analysis using a SM 2000 mill (Retsch GmbH, Haan, Germany) and a perforated sieve with a per- foration of 1 mm (Conidur˝). The ground samples were conditioned at 20 °C and 1 ± 1% RH. A small amount of the ground sample (≈400 mg) was used. The measurement was performed at a constant temperature of 25 ± 0.2 °C. A total of two sorption and desorption cycles were measured from 0% RH to 95% RH, and vice versa. 3 RESULTS AND DISCUSSION 3 REZULTATI IN RAZPRAVA The cross-sections of the wood planks indicate the typical structure of Norway spruce wood. The annual rings are about 2 mm to 3 mm wide (Fig- ure 1). The anatomical structure (Figure 2) shows the gradual transition between earlywood and latewood cells. The respective resin canals are bor- dered by 8 to 12 or more thick-walled epithelial cells (Wagenführ, 2014). The density of the air-dry planks examined was 420 kg/m³ (st. dev. 17 kg/m³). This is in line with the data in the literature (Gryc et al., 2011; Humar, 2013). As seen from microscopic analysis (Figure 3, Figure 4), Burnblock crystals are seen in the cell lu- mina. The presence of the crystals was confirmed using two independent microscopy techniques, confocal laser scanning microscopy and digital mi- croscopy. The presence of the crystals in the cell lumina is not surprising, as the retention of Burn- block and other fire-retardants is higher than the retention of wood preservatives. For example, the retention of typical copper-ethanol wood preserva- tives is about 20 kg/m³ (Nordic Wood Preservation Council 2021) (for in-ground use), while the reten- tion of classical CCA barely reaches 12 kg/m³ (Wil- leitner, 2001). The crystals in the cell lumina are rather significant. It can be assumed that they were at least partially damaged during cutting. In the graphs (Figure 5), the sorption curves of the untreated and treated spruce wood are plotted. As can be seen, both the untreated and Figure 1. Cross-section of spruce wood plank, used for microscopic and sorption analysis. Slika 1. Prečni prerez deske, uporabljene za mikroskopsko in sorpcijsko analizo. 18 Les/Wood, Vol. 71, No. 1, June 2022 Humar, M., Lesar, B., & Kržišnik, D.: Sorpcijske lastnosti lesa, impregniranega z ognjezadrževalnim sredstvom Burnblock Burnblock-treated wood show typical sorption isotherms of type II. The differences between the EMC at 95% RH of untreated and treated wood are negligible. For example, in the first sorption cycle, the EMC of untreated spruce wood (23.09%) is slightly higher than the EMC of Burnblock-treated Figure 2. Annual ring of spruce wood plank Slika 2. Branika v lesu smrekove deske Figure 3. Cell lumina of all cells are filled with crys- tals of the fire retardant Burnblock. Microscopy was performed with a digital microscope. Colours are not always representative. Slika 3. Mikroskopska slika, ki prikazuje zapolnje- nost vseh celičnih lumnov z ognjezadrževalnim sredstvom Burnblock. Slika je posneta z digitalnim mikroskopom. Barve niso vedno reprezentativne. Figure 4. Cell lumina filled with crys- tals of the fire retardant Burnblock. The image was obtained with confocal scanning laser microscope (field of view 128 µm × 128 µm). Colours are not al- ways representative. Slika 4. Celični lumni, zapolnjeni s kristali ognjezadrževalnega sredstva Burnblock. Slika je bila posneta s konfokalnim la- serskim vrstičnim mikroskopom (vidno polje = 128 µm × 128 µm). Barve niso vedno reprezentativne. 19 Les/Wood, Vol. 71, No. 1, June 2022 Humar, M., Lesar, B., & Kržišnik, D.: Sorption properties of wood impregnated with the fire retardant Burnblock wood (22.79%). However, in the second sorption cycle, the EMC of Burnblock-treated wood was slightly higher (23.70%) than that of untreated spruce wood (22.47%). Normally, the second EMC at 95% RH for lignocellulosic materials is lower than the first (Glass et al., 2018), but in this case it was slightly higher for the Burnblock-treated sample. As DVS analysis was performed in controlled condi- tions it enables a reliable comparison, but statisti- cal analysis was not performed due to low number of measurements (Glass et al., 2018). The interpretation of the sorption curves is that the surfaces of the analysed wood samples are more polar than water molecules, and therefore Figure 5. Results of the sorption analysis of the (A) reference Norway spruce wood (PiAb), (B) Burnblock-im- pregnated Norway spruce wood (BB) in two sorption and desorption cycles. In graph (C), hysteresis is plotted. In contrast, in graph (D) differences in equilibrium wood moisture content between treated and untreated spruce in the first and second sorption cycles are presented. Negative values indicate that the MC of treated wood was lower than that of untreated wood. Slika 5. Rezultati sorpcijske analize (A) referenčne smrekovine (PiAb), (B) smrekovine, impregnirane z og- njezadrževalnim sredstvom Burnblock v dveh sorpcijskih in desorpcijskih ciklih. Slika C prikazuje histerezo, slika D pa razliko v vlažnosti med impregnirano in neimpregnirano smrekovino v prvem in drugem sorp- cijskem ciklu. Negativne vrednosti nakazujejo, da je bila vlažnost impregniranega lesa nižja od vlažnosti neimpregniranega lesa. 20 Les/Wood, Vol. 71, No. 1, June 2022 Humar, M., Lesar, B., & Kržišnik, D.: Sorpcijske lastnosti lesa, impregniranega z ognjezadrževalnim sredstvom Burnblock show increased water uptake at low RH (0 to 10%). Once a single (mono-)layer of water has formed, additional adsorption increasingly resembles the condensation of water. At high RH, i.e. above 70%, adsorption is enhanced due to the presence of tiny surface pores (mesopores, with pore diameters of 2 to 50 nm). These attract water molecules on more than one side, i.e. by capillary condensation. This leads to hysteresis in this humidity region caused by the reluctant release of the adsorbed water (Mangel, 2000). As the hysteresis between the sorption and desorption curves for Burnblock-treated wood in- creases at the higher sorption range (Figure 5), this indicates that there are more condensation sites present in the Burnblock-treated wood than in the reference spruce wood. This can be ascribed to the presence of crystals in cell lumina, as clearly seen from microscopic analysis (Figure 4). 4 CONCLUSIONS 4 ZAKLJUČKI The sorption properties of Burnblock-treated wood are comparable to those of untreated wood, while the moisture content of Burnblock-treated wood is comparable to that of untreated Norway spruce. The only difference can be found in the hysteresis between the sorption and desorption curves at higher relative humidities. This can be as- cribed to the presence of the crystals of Burnblock in the wood cell lumina. It can be thus presumed that the Burnblock-treated wood with retentions up to 38 kg/m³, exhibits the same susceptibility to- wards staining fungi. 5 SUMMARY 5 POVZETEK Sorpcijske lastnosti lesa imajo značilen vpliv na nekatere lastnosti lesa. V največji meri vplivajo na mehanske lastnosti in dovzetnost lesa na gliv- ni razkroj. Vlažnejši les je bolj dovzeten za glivni razkroj. Mejna vrednost za glivni razkroj je tri do pet odstotnih točk pod točko nasičenja celičnih sten. Po drugi strani dovzetnost lesa na pojav gliv plesni in gliv modrivk pogosto opišemo s kritično relativno zračno vlažnostjo, pri kateri se pojavijo plesni. Za večino lesnih vrst ta meja znaša okoli 75 %. V prime- ru bolj higroskopnih lesnih vrst je ta meja lahko tudi nižja. Za zaščito pred glivnim razkrojem, fotode- gradacijo ali gorenjem les pogosto impregniramo. Predvsem anorganske soli vplivajo na sorpcijske lastnosti lesa. To je še posebej značilno za les, im- pregniran z borovo kislino, boraksom ali natrijevim kloridom. Zelo higroskopna so tudi nekatera ognje- zadrževalna sredstva. S tem namenom smo prei- skali sorpcijske lastnosti smrekovine, impregnirane z ognjezadrževalnim sredstvom Burnblock (navzem 38 kg/m³). Burnblock sodi med okolju prijazne re- šitve, brez znanih negativnih vplivov na okolje. Impregniran les smo preiskali z dvema mikroskop- skima tehnikama (konfokalna laserska vrstična mi- kroskopija in digitalna mikroskopija). Mikroskopska analiza je potrdila prisotnost kri- stalov v celičnih lumnih. Sorpcijske lastnosti smo določili z opremo, ki omogoča dinamično sorpcijo vodne pare (DVS). Les smo zmleli in homogenizirali ter ga izpostavili dvema cikloma navlaževanja in su- šenja v območju med 0 % in 95 % relativne zračne vlažnosti pri 25 °C. Rezultati so pokazali, da so sorp- cijske lastnosti lesa, obdelanega z Burnblockom, primerljive s sorpcijskimi lastnostmi neobdelanega lesa smreke. Vsebnost vlage v lesu, impregniranim z Burnblockom, je primerljiva z vsebnostjo vlage neobdelane smrekovine. Edina razlika je v histerezi med sorpcijskimi in desorpcijskimi krivuljami pri viš- ji relativni vlažnosti. To lahko pripišemo prisotnosti kristalov v lumnih lesnih celic. Tako lahko domne- vamo, da je les, obdelan z Burnblock, z navzemom do 38 kg/m³, primerljivo dovzeten za delovanje gliv modrivk in plesni kot neimpregniran les. ACKNOWLEDGEMENT ZAHVALA The authors acknowledge the financial sup- port of the Slovenian Research Agency (ARRS) within the research program P4-0015 (Wood and lignocellulosic composites) and the infrastructural centre (IC LES PST 0481-09). 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DOI: https://doi.org/10.1007/ s00226-018-0998-x 22 Les/Wood, Vol. 71, No. 1, June 2022 Humar, M., Lesar, B., & Kržišnik, D.: Sorpcijske lastnosti lesa, impregniranega z ognjezadrževalnim sredstvom Burnblock 23 Les/Wood, Vol. 71, No. 1, June 2022 PHYSICAL AND CHEMICAL PROPERTIES OF THREE WILD ALMOND WOOD SPECIES GROWN IN ZAGROS FORESTS FIZIKALNE IN KEMIJSKE LASTNOSTI LESA TREH DIVJIH VRST MANDLJEVCA, KI RASTEJO V GOZDOVIH ZAGROSA Leila Fathi 1* , Redžo Hasanagić 2 , Yaghoob Iranmanesh 3 , Mohammad Dahmardeh Ghalehno 4 , Miha Humar 5 , Mohsen Bahmani 1 UDK 630*812:634.55 Received / Prispelo: 7. 3. 2022 Original scientific article / Izvirni znanstveni članek Accepted / Sprejeto: 4. 5. 2022 . Abstract / Izvleč ek Abstract: In this study, the physical properties (oven-dry density, basic density, volumetric shrinkage, and swelling) and structural components (cellulose, lignin, and extractives content) of three wild almond wood species from southwestern Iran, namely Amygdalus arabica, Amygdalus eburna, and Amygdalus scoparia, were investigated. Wild almond is a valuable wood species in the Zagros forests of Iran, but there is a lack of data on their wood properties. Three adult trees of each species were chosen, and samples were prepared from the breast height diameter to measure the focal properties. Results of analysis of variance (ANOVA) showed that the wood species had a significant effect on the wood density and volumetric shrinkage. Maximum oven-dry density and volumetric shrinkage of wood were identified in Amygdalus scoparia. The highest and lowest content of structural components were found in Amygdalus scoparia and Amygdalus arabica wood species, respectively. A deep understanding of the almond wood characteristics will provide a fresh insight into the relationship between the properties and conservation of these special, as well as applications of their wood. Keywords: Amygdalus, wood, density, volume shrinkage, cellulose, lignin, Zagros, Iran Izvleček: V študiji so bile raziskane fizikalne lastnosti (gostota, osnovna gostota, prostorninsko krčenje in nabrekanje) in kemijska sestava (celuloza, lignin in ekstraktivne snovi) lesa treh divjih vrst mandljev, in sicer Amygdalus arabica, Amygdalus eburna in Amygdalus scoparia iz jugozahodnega Irana. Divji mandelj je dragocena drevesna vrsta v gozdovih Zagrosa v Iranu, podatki o lastnostih lesa pa so pomanjkljivi. Izbrana so bila tri sestojna drevesa vsake vrste, za merjenje omenjenih lastnosti pa so bili pripravljeni vzorci iz nivoja v prsni višini. Rezultati analize variance (ANOVA) so pokazali, da vrsta pomembno vpliva na gostoto lesa in prostorninsko krčenje. Največje vrednosti gostote absolutno suhega lesa in prostorninskega skrčka so bile ugotovljene pri vrsti Amygdalus scoparia. Najvišje in najnižje vsebnosti kemijskih komponent pa so bile ugotovljene pri lesnih vrstah Amygdalus scoparia in Amygdalus arabica. Poglobljeno razumevanje značilnosti mandljevega lesa bo omogočilo nov vpogled v povezavo med lastnostmi in ohranjanjem ter uporabo lesa raziskanih vrst. Ključne besede: Amygdalus, les, gostota, prostorninsko krčenje, celuloza, lignin, Zagros, Iran 1 INTRODUCTION 1 UVOD Almond species grow with a large geographi- cal distribution from the southwest to the centre of Asia (Gradziel, 2011). Iran is thought to be the cen- tre of the origin and growth of almonds (Zohary & Hopf, 2000). As such, Iran is an important region for the world almond gene pool and the distribution of wild almond species due to its suitable climate (Bal- vardi et al., 2015; Nikoumanesh et al., 2011). Twen- Vol. 71, No. 1, 23-30 DOI: https://doi.org/10.26614/les-wood.2022.v71n01a03 1 Department of Natural Resources and Earth Science, Shahrekord University, Shahrekord, Iran 2 Department of Wood Science and Technology, Faculty of Technical Engineering, University of Bihać, Bihać, Bosnia and Herzegovina 3 Research Division of Natural Resources, Charmahal and Bakhtiari Agriculture and Natural Resources and Education Center, AREEO, Iran 4 Department of Wood and Paper Sciences and Technology, University of Zabul, Zabol, Iran 5 Department of Wood Science, Biotechnical Faculty, University of Ljubljana, Ljubljana, Slovenia * e-mail: leila.fathi@sku.ac.ir 24 Les/Wood, Vol. 71, No. 1, June 2022 Fathi, L., Hasanagić, R., Iranmanesh, Y ., Ghalehno, M. D., Humar, M., & Bahmani, M.: Fizikalne in kemijske lastnosti lesa treh divjih vrst mandljevca, ki rastejo v gozdovih Zagrosa ty-one wild species and seven inter-specific hy- brids have been identified and reported in Iran, of which ten are supposed to be endemic (Khatamsaz, 1998). Zagros forests represent about 40% of Irani- an forests and are the most extensive forest area (Sagheb-Talebi et al., 2004). Almonds are decid- uous shrubs and small trees adapted to arid or semi-arid environments. They exist as a relatively pure and dominant stand or scattered between 600 to 2200 meters above sea level. This plant is a shrub with a height of 2 m that sometimes reaches a height of 6 m and a stem diameter of 5-20 cm. Most studies regarding almond tree species are related to their distribution, ecological re- quirements, and morphological properties, while wood properties such as the physical and chemi- cal properties have not been reported yet. Funda- mental studies in these cases can reveal the pos- sibility of the wood’s use in various applications or lead to creating a database of different wood species (Bahmani et al., 2020; Dong et al., 2021). Kiaei and Samariha (2011) investigated the physical properties of five important hardwood plants from the forests of north Iran and found that the high- est wood density was determined for hornbeam, beech, ash, and oak. Most studies regarding Zagros forest wood species are related to their distribu- tion and ecological factors, and few have examined the wood properties. For example, Bahmani et al. (2018) investigated oak wood’s physical and chemi- cal properties in Zagros forests. They found that the density of the Persian oak (Quercus brantii Lindl.) is between 0.85 g·cm -3 and 1.01 g·cm -3 , and volu- metric shrinkage ranges from 11.32% to 14.15%. Moreover, their results indicated that the cellulose content increased with increasing diameter, and the lignin content decreased. Nazari et al. (2020) studied the geographic variations of wood density and fibre dimensions of Persian oak wood, and re- ported a significant statistical effect of altitude and slope on the volumetric swelling of this material. In another study by Nazari et al. (2021), the influence of site conditions on the physical and morpholog- ical properties of hawthorn (Crataegus azarolus) wood grown in the Zagros forests of Iran was inves- tigated. They reported that there were statistically significant differences in the oven-dry density of hawthorn wood at various altitudes, while no sig- nificant differences were found between the values of volumetric shrinkage. Understanding the proper- ties of almond wood is important for utilizing wood resources. To the best of our knowledge, there are no published studies relevant to the properties of wild almond wood. Considering the valuable po- sition of these wood species in the Zagros forests of Iran, this study aims to investigate the physical properties, including dry-density, basic density, vol- umetric shrinkage and swelling, and chemical com- ponents (cellulose, lignin, extractives, and ash) of three wild almond wood species. 2 MATERIALS AND METHODS 2 MATERIALI IN METODE 2.1 MATERIALS 2.1 MATERIALI This research was done on three wild almond wood species – desert almond (Amygdalus arabi- ca; H=2.58 m, DBH=6 cm), grey almond (Amygdalus eburna; H=2.45 m, DBH=7.5 cm), and mountain al- mond (Amygdalus scoparia; H=2.00m, DBH=4.7cm), which were all cut from natural forests in Karebass and choliche-Charmahal and Bakhtiari province in the southwest of Iran. The research area is locat- ed between 31°31′36″ N and 31°33′55″ N and be- tween 51°1920″ E and 51°12′15″. Disks from each sampled tree were cut at breast height. The annu- al rainfall and annual average temperatures were 555 mm and 16.7 °C, respectively. December and November are high-rain months and June and July are low-rain months. The temperature reaches its maximum level in June, July and August. The alti- tude of this site was 1580 m. 2.2 PHYSICAL PROPERTIES 2.2 FIZIKALNE LASTNOSTI Discs, 5 cm in thickness, were taken from logs to determine physical properties such as oven-dry density, basic density, volumetric shrinkage, and volumetric swelling. Determination of wood densi- ty was carried out based on the ISO-3131 (2016) standard. For determining the physical proper- ties, testing samples were obtained following ASTM-D143 (2000) and used for measuring the ov- en-dry and basic density, volumetric swelling and volumetric shrinkage. For this propose, thirty sam- ples were prepared from different parts of the disks (10 samples from each disk) with the dimensions of 25 Les/Wood, Vol. 71, No. 1, June 2022 Fathi, L., Hasanagić, R., Iranmanesh, Y ., Ghalehno, M. D., Humar, M., & Bahmani, M.: Physical and chemical properties of three wild almond wood species grown in Zagros forests 30 × 20 × 20 mm³ (tangential × radial × longitudinal). The samples were oven dried at 103 °C to reach a constant weight. Dimensions and dry weight were then measured, with the former Measured in all three principal directions with a digital caliper to the nearest 0.001 mm. The digital balance used for the measurement had an accuracy of 0.01 g. After- wards the samples were immersed in water (one week) and the weight and dimensions of the sam- ples were re-measured. The physical properties of the samples were calculated using the following equations: ρ 0 =m 0 /V 0 R = m 0 /V s α v = (V g – V 0 )/V 0 β v = (V g – V 0 )/V s where: ρ 0 is oven dry density (g·cm -3 ), R is basic density (g·cm -3 ), β- volumetric shrinkage (%), α is volumetric swelling (%), V g - volume in green state (g·cm -3 ), V 0 - volume in oven-dry state (g·cm -3 ), m 0 - weight in oven-dry state (g), m g - weight in green state. 2.3 CHEMICAL PROPERTIES 2.3 KEMIJSKE LASTNOSTI The chemical components were determined according to the TAPPI Tests Methods: Cellulose (T 257 om-85), lignin (T 222 om-98), extractives (T 204 om-88) (Table 1). The cellulose content of almond wood was determined according to the ni- tric acid method (Rowell et al., 1997). All measure- ments were repeated three times, and the mean value was used. 2.4 STATISTICAL ANALYSIS 2.4 STATISTIČNE ANALIZE To determine the physical properties (dry-den- sity, basic density, volumetric shrinkage, and swell- ing) and chemical components (cellulose, lignin, extractives, and ash), statistical analysis was con- ducted using the SPPS 23 (IBM, Armonk, NY , USA) program in conjunction with the analysis of vari- ance (ANOVA). Duncan’s multiple range test (DMRT was used to test the statistical significance at the α = 0.05 level. All data were checked for normality with a Shapiro–Wilk’s test. 3 RESULTS AND DISCUSSION 3 REZULTATI IN DISKUSIJA 3.1 MACROSCOPIC CHARACTERISTICS OF WOOD 3.1 MAKROSKOPSKA ZGRADBA LESA The wood has a yellow to light brown colour with dark heartwood. Cross-sections indicate a semi-ring-porous distribution of vessels (Figure 1a, b, c). The presence of the vessels can be seen in all of the wood species investigated. As can be found from in literature (Allué et al., 2018), ray cells are uniseriate to 3- and 7-seriate depending on the species. Vessels show spiral thickenings with sim- ple perforation plates. As seen on cross-sections, the wood is characterized by relatively wide annual rings, with clearly visible growth ring borders (Fig- ure 1a, b, c). An attractive macroscopic appearance has made almond wood an excellent choice for furniture production in the past (Britannica Online Encyclopaedia, 2022). Due to the small dimensions of the trees, however, furniture applications are rare nowadays. The wood is now mainly used for high-quality end products such as knife handles, pencils, souvenirs and decorative boxes. Chemical components Standard Description Cellulose (%) Pettersen (1984) Concentrated nitric acid Lignin (%) T 222 om-98 Sulfuric acid 72% Extractives (%) T 222 om-88 Alcohol / acetone Table 1. Applied methods for measuring the structural components of wood Preglednica 1. Metode, uporabljene za določitev kemijske zgradbe lesa 26 Les/Wood, Vol. 71, No. 1, June 2022 Fathi, L., Hasanagić, R., Iranmanesh, Y ., Ghalehno, M. D., Humar, M., & Bahmani, M.: Fizikalne in kemijske lastnosti lesa treh divjih vrst mandljevca, ki rastejo v gozdovih Zagrosa a Cross-section / Prečni prerez Radial section / Radialni prerez Tangential section / Tangencialni prerez b Cross-section / Prečni prerez Radial section / Radialni prerez Tangential section / Tangencialni prerez c Cross-section / Prečni prerez Radial section / Radialni prerez Tangential section / Tangencialni prerez Figure 1. Macroscopic appearence of wild almond wood species: (a) Amygdalus arabica, (b) Amygdalus eburna, (c) Amygdalus scoparia Slika 1. Prerezi lesa divjih mandljevcev (a) Amygdalus arabica, (b) Amygdalus eburna, (c) Amygdalus scoparia 27 Les/Wood, Vol. 71, No. 1, June 2022 Fathi, L., Hasanagić, R., Iranmanesh, Y ., Ghalehno, M. D., Humar, M., & Bahmani, M.: Physical and chemical properties of three wild almond wood species grown in Zagros forests 3.2 PHYSICAL PROPERTIES 3.2 FIZIKALNE LASTNOSTI The oven-dry density and basic density val- ues for the three wild almond species – Amygda- lus arabica (0.92 g·cm -3 ; 0.79 g·cm -3 ), Amygdalus eburna (0.91 g·cm -3 ; 0.78 g·cm -3 ), and Amygdalus scoparia (0.96 g·cm -3 ; 0.93 g·cm -3 ) – are given in Table 2. The analysis of variance (ANOVA) showed a significant difference between species regarding oven-dry density and basic wood density. The high- est and lowest oven-dry density and basic density were found in Amygdalus scoparia and Amygda- lus arabica wood, respectively. It is reported that there are several factors affecting the density of the wood, such as anatomical properties, e.g. ves- sel and fibre morphology, provenance, moisture content, and chemical composition (Wagenführ & Scheiber, 1995; Pásztory et al., 2014; Zeidler & Borůvka, 2016; Bahmani et al., 2020). Wood den- sity classification is grouped according to Wong (2002): light (<0.5 g·cm -3 ), moderately dense (be- tween 0.5–0.8 g·cm -3 ), including the almond wood species examined in this study, heavy (between 0.8–1.0 g·cm -3 ), very dense >1.0 g·cm -3 ). The values of oven-dry density and basic densi- ty obtained in this study for the three species of al- mond were lower than those of other hardwoods, such as Persian oak and hawthorn growing in the Zagros forests, as reported by Bahmani et al. (2018) and Nazari et al. (2021). From the ANOVA test, there is a significant difference between wood species and volumetric shrinkage and volumetric swelling. Maximum and minimum volumetric shrinkage and swelling were identified in Amygdalus scoparia and Amygdalus arabica, respectively. As is well known, the relationship between wood density and vol- umetric shrinkage is positive (Sousa et al., 2018). Wood density is generally variable and is related to many factors such as anatomical characteristics, e.g., vessel and fibre morphology, ecological site, moisture content and chemical constitutes. Fibres are the most important elements affecting wood density, followed by vessels, as (for instance) re- ported by Kiaei (2012) for Carpinus betulus. 3.3 CHEMICAL COMPOSITION 3.3 KEMIJSKA ZGRADBA Table 3 illustrates the mean values of the chemical constituents of the three wood species of almond. The analysis of variance (ANOVA) showed sig- nificant differences between the tested species and the chemical components they contain. The highest and lowest content of cellulose, lignin and extractives were found in Amygdalus scoparia and Amygdalus arabica wood, respectively Such differ- ences could be related to site, growth conditions and forest management practices (Zobel & Buijte- nen, 1989; Bahmani et al., 2018). On average, hard- wood comprises 40-45% cellulose, 17-25% lignin, and less than 10% extractives. Overall, the cellulose lignin content of Amygdalus scoparia is higher than the average of most hardwoods, whereas the lignin content does not differ significantly. Wood species / Lesna vrsta Oven-dry density / Gostota lesa (g·cm -3 ) Basic density / Osnovna gostota (g·cm -3 ) Volumetric shrinkage / Prostorninski skrček (%) Volumetric swelling / Prostorninski nabrek (%) Amygdalus arabica 0.92a (0.07) 0.79a (0.09) 0.10a (0.05) 0.11a (0.06) Amygdalus eburna 0.91a (0.06) 0.78a (0.06) 0.12a (0.08) 0.14a (0.01) Amygdalus scoparia 0.96b (0.02) 0.93b (0.01) 0.14b (0.02) 0.16b (0.02) Table 2. The average values of physical properties in the three studied species. Standard deviations are given in the parenthesis. The different letters indicate a different statistical group. Preglednica 2. Povprečne vrednosti fizikalnih lastnosti preučevanih vrst lesa. V oklepajih so podani standar- dni odkloni. Različne črke označujejo različne statistične skupine. 28 Les/Wood, Vol. 71, No. 1, June 2022 Fathi, L., Hasanagić, R., Iranmanesh, Y ., Ghalehno, M. D., Humar, M., & Bahmani, M.: Fizikalne in kemijske lastnosti lesa treh divjih vrst mandljevca, ki rastejo v gozdovih Zagrosa 4 CONCLUSIONS 4 SKLEPI Wild almonds are valuable tree species in Ira- nian Zagros forests, although there is limited data on their wood properties. As such, in this study the wood properties of three wild almond species were examined. The results indicated that the studied wood is moderately heavy with a density between 0.91 g·cm -3 to 96 g·cm -3 and can be classified into moderate-volumetric swelling species. In addition, the cellulose content (39.92-49.83 %), lignin con- tent (17.96-25.71 %), and extractive content (3.89- 5.12 %) were determined. Considering the valua- ble position of tree wood species in Zagros forests, the results obtained in this study can provide basic information about the conservation and rehabilita- tion of almond wood. Further studies will address other properties such as the fibre dimensions and natural durability of wild almond wood against fun- gi, moulds, insects, and termites. ACKNOWLEDGEMENT ZAHVALA We are grateful for financial support from Shahrekord University and the University of Zabol (Grant IR-UOZGR-5071). 5 SUMMARY 5 POVZETEK Divji mandelj je dragocena lesna vrsta v gozdo- vih Zagrosa v Iranu, podatki o lastnostih lesa pa so pomanjkljivi. Različne vrste mandljev so geografsko razširjene od jugozahoda do osrednje Azije (Grad- ziel, 2011). Iran naj bi bil središče izvora mandljev (Zohary & Hopf, 2000) in je zaradi primernega pod- nebja pomembna regija za svetovni genski sklad in razširjenost divjih vrst mandljev (Balvardi et al., 2015; Nikoumanesh et al., 2011). Mandlji so listo- padni grmi in majhna drevesa, prilagojena na sušna ali polsušna okolja. Večina študij mandljev se nana- ša na njihovo razširjenost, ekološke zahteve, mor- fološke lastnosti, o lastnostih lesa, kot so fizikalne in kemijske lastnosti, pa še niso poročali. Temelj- ne raziskave bi lahko ovrednotile možnost njihove uporabe in omogočile oblikovanje podatkovne zbir- ke različnih vrst lesa (Bahmani et al., 2020; Dong et al., 2021). Bahmani et al. (2018) so raziskovali fizikalne in kemijske lastnosti hrastovega lesa v goz- dovih Zagrosa. V literaturi ni podatkov o lastnostih lesa divjega mandlja, zato je namen te študije raz- iskati fizikalne in kemijske lastnosti treh divjih vrst mandljev Amygdalus arabica, Amygdalus eburna in Amygdalus scoparia. Les je bil posekan v naravnih gozdovih v provincah Karebass, Choliche-Charma- hal in Bakhtiari na jugozahodu Irana. Raziskovalno območje se nahaja med 31°31′36″ S in 31°33′55″ S ter med 51°1920″ V in 51°12′15″. Iz hlodov so bili odvzeti 5 cm debeli diski za do- ločanje fizikalnih lastnosti, kot so gostota absolutno suhega lesa, osnovna gostota, ter prostorninsko kr- čenje in nabrekanje. Gostota lesa je bila določena na podlagi standarda ISO-3131 (2016). Za določanje fizikalnih lastnosti so bili po standardu ASTM-D143 (2000) pridobljeni preskusni vzorci z dimenzijami 2 × 2 × 2 cm³, ki so bili uporabljeni za merjenje go- stote absolutno suhega lesa in osnovne gostote ter prostorninskega krčenja. Kemične sestavine so bile določene v skladu s preskusnimi metodami TAPPI: Celuloza (T 257 cm- 85), lignin (T 222 om-98), pepel (T 211 om-93) in Wood species Cellulose (%) Lignin (%) Extractives (%) Amygdalus arabica 39.92a (2.86) 17.96a (1.6) 3.89a (0.6) Amygdalus eburna 43.18a (3.13) 18.52a (1.8) 4.01a (0.7) Amygdalus scoparia 49. 83b (4.18) 25.71b (2.10) 5.12b (0.9) Table 3. The average chemical composition in the three studied species. Standard deviations are given in parentheses. The different letters indicate different statistical groups. Preglednica 3. Povprečna kemijska sestava preučevanih lesnih vrst. V oklepajih so podani standardni odklo- ni. Različne črke označujejo različne statistične skupine. 29 Les/Wood, Vol. 71, No. 1, June 2022 Fathi, L., Hasanagić, R., Iranmanesh, Y ., Ghalehno, M. D., Humar, M., & Bahmani, M.: Physical and chemical properties of three wild almond wood species grown in Zagros forests topnost v alkohol-acetonu (T 204 cm-88). Vsebnost celuloze v mandljevem lesu je bila določena po me- todi z dušikovo kislino (Rowell et al., 1997). Vse me- ritve so bile ponovljene trikrat, uporabljena pa je bila povprečna vrednost. Za ugotavljanje razlik med vrstami mandljev- ca z vidika fizikalnih in kemijskih lastnosti je bila opravljena statistična analiza variance (ANOVA) s programom SPPS 23 (IBM, Armonk, NY , ZDA). Za preverjanje statistične značilnosti na ravni α = 0,05 je bil uporabljen Duncanov test več razponov (DMRT). Les je rumene do svetlo rjave barve s temno jedrovino. Prečni prerezi kažejo na (pol)venčasto porozno razporeditev trahej (slika 1a, b, c). Kot je mogoče razbrati iz literature (Allué et al., 2018), so trakovi 1-3 in 7-redni, odvisno od posamezne vrste. Traheje imajo spiralne odebelitve in enostavne per- forirane ploščice. Kot je razvidno iz prečnih prere- zov, so za les značilne razmeroma široke branike z jasno vidnimi mejami (slika 1a, b, c). Zaradi de- korativne teksture je bil mandljev les v preteklosti zaželen za izdelavo pohištva (Spletna enciklopedija Britannica, 2022). Zaradi manjših dimenzij dreves je danes uporaba za pohištvo redka. Les se večinoma uporablja za izdelke višjega cenovnega razreda, kot so ročaji nožev, svinčniki, spominki in okrasne ška- tle. Vrednosti gostote absolutno suhega lesa in osnovne gostote so: Amygdalus arabica (0,92 g·cm -3 ; 0,79 g·cm -3 ), Amygdalus eburna (0,91 g·cm -3 ; 0,78 g·cm -3 ) in Amygdalus scoparia (0,96 g·cm -3 ; 0,93 g·cm -3 ) (Tabela 1). Analiza varian- ce (ANOVA) je pokazala značilno razliko med vrsta- mi za obe gostoti. Najvišja in najnižja gostota je bila ugotovljena pri lesu Amygdalus scoparia oziroma Amygdalus arabica. Iz testa ANOVA je razvidna pomembna razli- ka med vrstami lesa v prostorninskem krčenju in nabrekanju. Največje in najmanjše prostorninsko krčenje in nabrekanje je bilo ugotovljeno pri vrstah Amygdalus scoparia in Amygdalus arabica. Analiza variance (ANOVA) je pokazala po- membno razliko med vrstami in kemijskimi kom- ponentami. Največja vsebnost celuloze, lignina in ekstraktivov je bila ugotovljena v lesu Amygdalus scoparia in najmanjša pri Amygdalus arabica. Raz- like bi lahko bile povezane z rastiščem, pogoji rasti in praksami gospodarjenja z gozdom (Zobel & Buij- tenen, 1989; Bahmani et al., 2018). V povprečju les listavcev vsebuje 40-45 % celuloze, 17-25 % lignina in manj kot 10 % ekstraktivnih snovi. Na splošno je vsebnost celuloze in lignina v drevesu Amygdalus scoparia višja od povprečja večine listavcev, med- tem ko se vsebnost lignina bistveno ne razlikuje. Rezultati so pokazali, da so preučevane vrste lesa srednje goste, z gostoto med 0,91 g·cm -3 in 96 g·cm -3 , in jih uvrščamo med vrste z zmernim volu- menskim nabrekanjem. Poleg tega je bila določena vsebnost celuloze (39,92-49,83 %), lignina (17,96- 25,71 %) in pepela (3,89-5,12 %). Nadaljnje študije bodo obravnavale druge lastnosti, kot so dimenzije vlaken in naravno odpornost lesa divjega mandlja proti glivam, plesnim, žuželkam in termitom. REFRENCES VIRI Allué, E., Expósito, I., Tumung, L., Ollé, A., & Bazgir, B. (2018). Early evidence of Prunus and Prunus cf. amygdalus from Palaeolithic sites in the Khorramabad Valley, western Iran. Comptes Ren- dus Palevol, 17(6), 335-345. ASTM D 143-94 (2000). Standard Test Methods for Small Clear Speci- mens of Timber, Philadelphia, PA., USA. Bahmani, M., Fathi, L., Koch, G., Kool, F., Aghajani, H., & Humar, M. (2020). Heartwood and sapwood features of Sorbus torminalis grown in Iranian forests. Wood Research, 65, 195-204. Bahmani, M., Saeidi. S., Humar, M., & Kool, F. (2018). Effect of tree diameter classes on the properties of Persian oak (Quercus brantii lindl.) wood. Wood Research, 63, 755-762. Balvardi, M., Mendiola, J. A., Castro-Gómez, P ., Fontecha, J., Rezaei, K., & Ibáñez, E. (2015). 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Zohary, D., & Hopf, M. (2000). Domestication of plants in the Old World: The origin and spread of cultivated plants in West Asia, Europe and the Nile Valley (No. Ed. 3). Oxford university press. 31 Les/Wood, Vol. 71, No. 1, June 2022 TREE-RING CHRONOLOGIES OF PICEA ABIES, LARIX DECIDUA AND FAGUS SYLVATICA ALONG ALTITUDINAL GRADIENTS KRONOLOGIJE ŠIRIN BRANIK DREVESNIH VRST PICEA ABIES, LARIX DECIDUA IN FAGUS SYLVATICA VZDOLŽ GRADIENTOV NADMORSKE VIŠINE Klemen Novak 1* , Martin de Luis 2 , Nina Škrk 1 , Aleš Straže 1 , Katarina Čufar 1 UDK 630*561.24:630*111 Received / Prispelo: 31. 5. 2022 Original scientific article / Izvirni znanstveni članek Accepted / Sprejeto: 9. 6. 2022 . Abstract / Izvleč ek Abstract: The dendrochronological climate signal of Norway spruce (Picea abies), European larch (Larix decidua), and European beech (Fagus sylvatica), among others, depends on altitude, therefore we have to collect dendrochronological data systematically for each species along altitude gradients. To this end, we established local tree-ring chronologies for the three species along two elevation gradients: (1) Kokra – Jezersko with sites at 750, 780, 950, 1200, 1250, 1380, 1600 m a.s.l., and (2) Bled – Radovna – Krma with sites at 518, 550, 580, 700, 750, 900, 950, 1000, 1200, 1400, 1600, 1760, 1900, 2040 m a.s.l. We present the main characteristics of the chronologies and the results of the dendroclimatological analyses, which show how the climatic factors influence the variation of the tree rings in dependence of altitude and species. We also present the agreement of the different chronologies in terms of standard dendrochronological parameters such as the t-value and discuss the potential use of the presented database. Keywords: Norway spruce (Picea abies), European larch (Larix decidua), European beech (Fagus sylvatica), tree rings, dendrochronology, altitudinal gradients, climate, Slovenia Izvleček: Dendrokronološki signal navadne smreke (Picea abies), evropskega macesna (Larix decidua) in navadne bukve (Fagus sylvatica) je med drugim odvisen od nadmorske višine, zato moramo za razumevanje dendrokronološkega signala sistematično zbirati podatke o posamezni vrsti vzdolž višinskih gradientov. V ta namen smo zbrali vzorce lesa in sestavili lokalne kronologije širin branik omenjenih treh vrst z območij vzdolž dveh gradientov: (1) Kokra – Jezersko, ki vključuje lokacije na 750, 780, 950, 1200, 1250, 1380 in 1600 m nadmorske višine, in (2) Bled – Radovna – Krma z rastišči na 518, 550, 580, 700, 750, 900, 950, 1000, 1200, 1400, 1600, 1760, 1900, 2040 m n. v. Predstavljamo glavne značilnosti kronologij in rezultate dendroklimatoloških analiz, ki so potrdile, da se podnebni dejavniki, ki vplivajo na variiranje širin branik, spreminjajo z nadmorsko višino in da je to spreminjanje širin branik različno pri posamezni drevesni vrsti. Predstavljamo tudi ujemanje različnih kronologij z vidika standardnih dendrokronoloških parametrov, kot je t-vrednost, in razpravljamo o možni uporabi predstavljene podatkovne baze. Ključne besede: navadna smreka (Picea abies), evropski macesen (Larix decidua), navadna bukev (Fagus sylvatica), branike, dendrokronologija, gradient nadmorske višine, podnebje, Slovenija 1 INTRODUCTION 1 UVOD Norway spruce (Picea abies), European larch (Larix decidua), and European beech (Fagus syl- vatica) in Slovenia have particular species-specific tree-ring characteristics in relation to climatic fac- tors which affect the importance of each species in dendrochronology. Since the climatic signal de- pends on altitude, the construction of local chro- nologies of trees from known sites along altitudi- Vol. 71, No. 1, 31-46 DOI: https://doi.org/10.26614/les-wood.2022.v71n01a04 1 Univerza v Ljubljani, Biotehniška fakulteta, Oddelek za lesarstvo, Jamnikarjeva 101, 1000 Ljubljana, SLO * e-mail: klemen.novak@bf.uni-lj.si 2 Universidad de Zaragoza, Departamento de Geografia, Calle de San Juan Bosco 7, 50009 Zaragoza, ES 32 Les/Wood, Vol. 71, No. 1, June 2022 Novak, K., de Luis, M., Škrk, N., Straže, A., & Čufar, K.: Kronologije širin branik drevesnih vrst Picea abies, Larix decidua in Fagus sylvatica vzdolž gradientov nadmorske višine nal gradients represents an important step in their dendrochronological characterization, including the issues of teleconnection (similarity of the den- drochronological signal of the same species over longer distances) and heteroconnection (similarity of the dendrochronological signal between differ- ent species). European beech has a wide natural range and grows on a great variety of sites (Euforgen, 2022), and is important for dendroecological studies throughout Europe (e.g., Di Filippo et al., 2007; Martinez del Castillo et al., 2022). The dendrochron- ological signal of beech shows a variable response to climatic factors depending on altitude and lat- itude (Čufar et al., 2008; Di Filippo et al., 2007; Martinez del Castillo et al., 2018). In temperate zones of Central Europe, including Slovenia, low- land beech responds mainly negatively to hot and dry late spring and early summer (May, June, July) weather, while at higher elevations and cold sites it responds positively to summer temperatures (e.g., Čufar et al., 2008; Di Filippo et al., 2007). Numerous studies have also shown that frequent climatic ex- tremes such as ice storms, late frosts, and excessive summer heat negatively affect beech growth (Bas- cietto et al., 2018; Decuyper et al., 2020; Gazol et al., 2019; Martinez del Castillo et al., 2022; Rožen- bergar et al., 2020). It is thus assumed that beech might decline at numerous sites as climate change progresses (Martinez del Castillo et al., 2022). Beech is currently the most common forest tree species in Slovenia, accounting for 32.9% in the wood stock (ZGS, 2021). Its wood is a highly val- ued industrial timber for numerous uses (Čufar et al., 2017). Despite this, it is rarely found in historical objects, and we do not have long composed region- al chronologies for dating (Čufar et al., 2012). Norway spruce is one of the most important coniferous tree species with a wide distribution area (Euforgen, 2022). Basically, it is a species of cold environments, which has been widely artifi- cially spread in Central Europe (including Austria, Germany, Czech Republic, Switzerland, Slovenia) even in lowland areas (e.g., Caudullo et al., 2016; Jansen et al., 2017; Kolář et al., 2020; Marincek et al., 2003). It is an important wood species for vari- ous uses (Straže et al., 2022), wood formation and dendroecology (e.g., Kolář et al., 2020; Martinez del Castillo et al., 2018), dendrochronology and for dating historical objects, including musical instru- ments (Bernabei et al., 2017; Cherubini, 2021; Wil- son et al., 2004). Norway spruce is currently the second most common forest tree species in Slovenia, accounting for 30.2% of the wood stock (ZGS, 2021). Its natu- ral range in Slovenia is restricted to high altitudes, mainly in the Alps and the Dinaric Mountains (Brus, 2012; ZGS, 2022). Since the early 19 th century, the species has been artificially spread throughout Slo- venia, including the lowlands (ZGS, 2022), where it is currently severely affected by climate change and associated bark beetle infestations (e.g., de Groot et al., 2021). The dendroclimatological signal of spruce is strongly influenced by local climatic conditions and varies considerably with altitude. This variability is particularly high in Slovenia, where we lack an ad- equate collection of chronologies for dating histor- ical objects (e.g., Bernabei et al., 2018; Čufar et al., 2020). In Slovenia, spruce is found in numerous ob- jects that are often difficult to date, therefore the knowledge of its signal along elevational gradients is particularly important. European larch is a pioneer tree species, able to colonize open land on disturbed soils; it can tolerate very cold temperatures during winter. Its natural range is mainly limited to high mountains, especially the Alps (Euforgen, 2022). In Slovenia it has a share of 1.2% in the wood stock (ZGS, 2021). Its wood is highly valued for its high density and durable heartwood (Čufar, 2006; Gričar & Prislan, 2021). It is and was valued for modern and histori- cal constructions, and can be found in many prom- inent buildings of the Venetian Republic (Levanič et al., 2001). Therefore, long composed tree-ring chronologies have been constructed for this spe- cies, based on wood from trees and historical con- structions (Bebber, 1990; Nicolussi, 1995; Sieben- list-Kerner, 1984). Using subfossil stems preserved in bogs and glaciers it was possible to construct one of the longest multimillennial chronologies of conifers, including Larix decidua, Pinus cembra and Picea abies, spanning 9,111 years (7109 BC to AD 2002) (Nicolussi et al., 2009). Larch from high elevation shows excellent teleconnection over larger areas (Levanič, 2005a; Levanič et al., 2001). However, detailed studies in Slovenia have shown that its dendrochronological 33 Les/Wood, Vol. 71, No. 1, June 2022 Novak, K., de Luis, M., Škrk, N., Straže, A., & Čufar, K.: Tree-ring chronologies of Picea abies, Larix decidua and Fagus sylvatica along altitudinal gradients signal also depends on altitude (Levanič, 2005b) which often makes the dating of historical objects made of “lowland larch” extremely difficult. The main objective of this study is to present the tree-ring chronologies of Norway spruce (Picea abies), European larch (Larix decidua), and Euro- pean beech (Fagus sylvatica) along two altitudinal gradients in the Kamnik-Savinja Alps and the Julian Alps, starting from the lowlands to the altitudinal limit of species distribution in the studied areas. We present (1) the constructed tree-ring chronolo- gies and their main characteristics, (2) how climatic Figure 1. Sampling areas with (a) map of Slovenia, (b) Kokra – Jezersko, and Bled – Radovna – Krma with sampling locations and (c) detailed views of site locations along the altitudinal gradients for three tree spe- cies: European beech (Fagus sylvatica) – FASY; European larch (Larix decidua) – LADE; and Norway spruce – (Picea abies), PCAB. For details see Tables 1 and 2. Source of maps: Esri, DigitalGlobe, GeoEye, Earthstar Geographics, CNES/Airbus DS, USDA, USGS, AeroG- rid, IGN, and the GIS User Community. Slika 1. Mesta vzorčenja (a) zemljevid Slovenije, (b) Kokra – Jezersko in Bled – Radovna – Krma z oznakami lokacij vzorčenja ter (c) mesta vzorčenja vzdolž višinskih gradientov za tri vrste: navadno bukev (Fagus syl- vatica)–FASY, evropski macesen (Larix decidua)–LADE in navadno smreko (Picea abies)–PCAB. Za podrob- nosti primerjajte preglednici 1 in 2. Vir zemljevidov: Esri, DigitalGlobe, GeoEye, Earthstar Geographics, CNES/Airbus DS, USDA, USGS, AeroG- rid, IGN, and the GIS User Community. 34 Les/Wood, Vol. 71, No. 1, June 2022 Novak, K., de Luis, M., Škrk, N., Straže, A., & Čufar, K.: Kronologije širin branik drevesnih vrst Picea abies, Larix decidua in Fagus sylvatica vzdolž gradientov nadmorske višine factors influence tree-ring variations, (3) the vari- ation of their dendrochronological signal, and (4) the potential of the database for future studies ad- dressing various issues related to ecology, climate, and cultural heritage. 2 MATERIALS AND METHODS 2 MATERIAL IN METODE 2.1 STUDY SITES AND TREES 2.1 RAZISKOVALNE PLOSKVE IN DREVESA The experimental design was based on a se- lection of mature dominant or codominant trees of Norway spruce, European larch, and European beech felled in the areas of Kokra – Jezersko, be- tween the Karawanks and Kamnik-Savinja Alps, and Bled – Radovna – Krma, Julian Alps in northwestern Slovenia (Figure 1). The sampling area Kokra – Jezersko is orient- ed south-east in the Kamnik-Savinja Alps. The sam- pling was performed on localities at 750, 780, 950, 1200, 1250, 1380, 1600 m a. s. l.) (Figures 1, 2a, Table 1). The area Bled – Radovna – Krma included lo- calities on 518, 550, 580, 700, 750, 900, 950, 1000, 1200, 1400, 1600, 1760, 1900, 2040 m a. s. l. (Fig- ures 1, 2b, Table 2). 2.2 SAMPLE COLLECTION AND PREPARATION 2.2 VZORČENJE IN OBDELAVA VZORCEV The fieldwork with the collection of samples was carried out from March until November 2019 in cooperation with forest owners, the Slovenia For- est Service, local foresters, the Triglav National Park in the area Bled – Radovna – Krma, and the Munic- ipality of Jezersko in the area Kokra – Jezersko with corresponding permissions. We aimed to collect 15 trees per site. After regular felling we collect- ed discs at the lower part of the trees (mainly 4 m above ground level). If the number of felled trees was not sufficient, additional samples were collect- ed by coring from the nearby living trees. For this purpose, two cores per tree were extracted at the breast height, perpendicular to the tree axis from the bark to the pith using a Haglöf increment corer combined with a Haglöf increment borer chuck and a cordless drilling machine (Milwaukee, M18 FDD2- 502X FUEL-135 Nm). The samples were labelled with the identifying system of the codes, which contained information on sampling site, tree species, tree number and the radius. The sampled discs and cores fixed on wooden supports were transported to the workshop and air dried. Their transversal surfaces were sanded with the belt sander using progressively finer sandpa- per, from 80, 120, 180, 220, 280, and 360 grit until the tree rings and individual cells in the wood on the transversal section were perfectly visible under a stereo microscope. The wood surface was scanned with a Mustek S-series 2400 Plus flatbed scanner with the reso- lution set at 1200 dpi and the images were pro- cessed with Adobe Photoshop Elements 2020. In the case of extremely narrow rings the structure of Figure 2. Selected locations from two areas with similar site characteristics: (a) Kokra – Jezersko with sam- pling locations J02, J03, J04 and J06, and (b) Krma with sampling locations KR1, KR2, KR3 and KR4. Slika 2. Izbrane lokacije z dveh območij s podobnimi rastiščnimi razmerami: (a) Kokra – Jezersko z lokacija- mi vzorčenja J02, J03, J04 in J06 in (b) Krma z lokacijami vzorčenja KR1, KR2, KR3 and KR4. 35 Les/Wood, Vol. 71, No. 1, June 2022 Novak, K., de Luis, M., Škrk, N., Straže, A., & Čufar, K.: Tree-ring chronologies of Picea abies, Larix decidua and Fagus sylvatica along altitudinal gradients wood was additionally checked under an Olympus stereo microscope S2 11 or images were obtained with the help of confocal laser scanning microscope CLSM (Balzano et al., 2019). 2.3 DATA ACQUISITION AND PROCESSING 2.3 ZAJEM IN OBDELAVA PODATKOV Tree-ring widths were measured using calibrat- ed high-resolution digital photos along two radii of each tree, to the nearest 0.01 mm using the CDen- dro / CooRecorder 9.5 image analysis program (Cy- bis Elektronik, 2022 http://www.cybis.se/forfun/ dendro/helpcoorecorder7/index.php). The TSAP- Win program (Frank Rinn, Heidelberg, Germany) and R Studio program using the dplR library (Bunn, 2010) were used for visual and statistical cross-dat- ing and verification. Cross-dated tree-ring series were assembled into local chronologies using R Studio and the dplR package (Bunn, 2008). 2.4 TREE RING CHRONOLOGIES AND CLIMATE 2.4 KRONOLOGIJE ŠIRIN BRANIK IN KLIMA The climatic influence on tree growth was ana- lysed using the residual version of each chronology with R Studio. For this purpose, the original tree- ring width series were standardized in a two-step procedure. First, the long-term trend was removed by fitting a negative exponential function (regres- sion line) to each tree-ring series. Second, more flexible detrending was carried out by applying a cubic smoothing spline with a 50% frequency re- sponse of 30 years to further reduce non-climatic variance. Subsequently, autoregressive modelling of the residuals and bi-weight robust estimation of the mean were applied (Cook & Peters, 1997). Local climatic data for calculation were ob- tained from the SLOCLIM data base (Škrk et al., 2021) which is a publicly available modelled climat- ic database which contains a daily gridded dataset of maximum and minimum temperature and pre- cipitation data with 1×1 km spatial resolution cov- ering the entire territory of Slovenia from 1950 to 2018. The data are available on zenodo (Škrk et al., 2020, 2021) and on the web page www.sloclim.eu. For each sampling location we extracted the climat- ic data of the nearest grid point and aggregated the daily data into monthly mean values. Pearson correlation function coefficients (CFC) were calculated by using the residual version of each tree-ring chronology as a dependent variable and the regressors monthly minimum and maxi- mum temperatures and the monthly sums of pre- cipitation for each biological year from the previous January to current December, as well as for the past and current spring, summer, autumn and current winter for the period 1950-2018. The climate and growth relationships were calculated using the pro- gram packages library(“dplR”), library(“stringr”), and library(“plyr”). The CFC values were considered statistically significant when p<0.05. 2.5 TELECONNECTION AND HETEROCONNECTION 2.5 TELEKONEKCIJA IN HETEROKONEKCIJA To test the potential of the chronologies with regard to establishing regional chronologies for dat- ing purposes, we made basic comparisons among the chronologies by calculating standard statistical values, including the t-value after Baillie and Pilcher (tBP) and sign test (Gleichläufigkeit–Glk) using the TSAP-Win program. We also tested the chronologies for telecon- nection (agreement between the chronologies of the same species from different sites) and for het- eroconnection (agreement between different tree species from the same site). 3 RESULTS AND DISCUSSION 3 REZULTATI IN RAZPRAVA 3.1 TREE-RING DATA AND THE CHRONOLOGIES 3.1 KRONOLOGIJE ŠIRIN BRANIK The database consists of 47 chronologies of three species along two altitudinal gradients in the Alps of Slovenia. We present their locations and time spans (Table 1 and 2). The local chronologies had average lengths of 156 (69-296) years for Euro- pean beech, 139 (57-355) years for Norway spruce, and 191 (56-378) years for European larch. At Kokra – Jezersko the corresponding averag- es (minimum-maximum) for seven beech chronol- ogies were 133 (69-296) years, for seven spruce chronologies 135 (57-246) years, and for six larch chronologies 156 (56-214) years (Table 1). At Bled – Radovna – Krma the averages (min- imum-maximum) for seven beech chronologies 36 Les/Wood, Vol. 71, No. 1, June 2022 Novak, K., de Luis, M., Škrk, N., Straže, A., & Čufar, K.: Kronologije širin branik drevesnih vrst Picea abies, Larix decidua in Fagus sylvatica vzdolž gradientov nadmorske višine Code / Koda Spe- cies / Dre- vesna vrsta Alti- tude / Nad- mor- ska višina Latitude / Zemljepisna širina Longitude / Zemljepisna dolžina Num- ber of trees / Število dreves Chro- nology Length / Kro- nologija Razpon Start / Zače- tek End / Konec m N / S E / V Years / leta Year / leto Year / leto J01A FASY 750 46.380118° 14.457731° 7 121 1899 2019 J01B FASY 780 46.389231° 14.483326° 10 122 1898 2019 J02 FASY 950 46.410676° 14.505766° 12 78 1941 2018 J12 FASY 1200 46.378934° 14.530259° 18 130 1890 2019 J03 FASY 1250 46.411992° 14.494944° 8 151 1869 2019 J04 FASY 1380 46.419799° 14.499313° 11 169 1850 2018 J06 FASY 1600 46.413493° 14.479713° 10 160 1860 2019 J01B LADE 780 46.389231° 14.483326° 10 162 1858 2019 J02 LADE 950 46.410676° 14.505766° 5 163 1856 2018 J03 LADE 1250 46.411992° 14.494944° 4 153 1866 2018 J04 LADE 1380 46.419799° 14.499313° 10 214 1805 2018 J06 LADE 1600 46.413493° 14.479713° 13 189 1832 2020 J24 LADE 1600 46.396635° 14.550305° 10 56 1964 2019 J01A PCAB 750 46.380118° 14.457731° 18 145 1874 2018 J01B PCAB 780 46.389231° 14.483326° 15 174 1846 2019 J02 PCAB 950 46.410676° 14.505766° 30 89 1930 2018 J12 PCAB 1200 46.378934° 14.530259° 17 138 1882 2019 J03 PCAB 1250 46.411992° 14.494944° 14 133 1887 2019 J04 PCAB 1380 46.419799° 14.499313° 15 97 1922 2018 J06 PCAB 1600 46.413493° 14.479713° 12 246 1774 2019 Table 1. Kokra – Jezersko, ba- sic information on the sites and chronologies along the gradient (short code, species, altitude, latitude, longitude, number of trees, useful length of the chro- nology and its start and end date) for three tree species: European beech (Fagus sylvatica) – FASY: European larch (Larix decidua) – LADE, and Norway spruce (Picea abies) – PCAB. Preglednica 1. Kokra – Jezersko, osnovni podatki o rastiščih in kro- nologijah vzdolž gradienta nad- morske višine (kratka koda, dre- vesna vrsta, nadmorska višina, zemljepisna širina, zemljepisna dolžina, število dreves, uporab- na dolžina kronologije ter prvo in zadnje leto) za tri drevesne vrste: navadna bukev (Fagus syl- vatica)–FASY, evropski macesen (Larix decidua)–LADE in navadna smreka (Picea abies)–PCAB. were 179 (69-296) years, for 11 spruce chronologies 142 (81-355) years, and for nine larch chronologies 215 (84-378) years. The oldest trees were sampled in Krma (KR*) (Table 2). 3.2 TREE-RINGS AND CLIMATE 3.2 ŠIRINE BRANIK IN KLIMA Correlation function coefficients (CFCs) for re- sidual chronologies and monthly minimum (Tmin) and maximum temperatures (Tmax) and precipita- tion (PCP) (Figures 3 and 4) from the previous Jan- uary to current December and from the previous and current spring, summer, autumn and current winter show that each of the species has a unique response to climate and that the response varies with elevation. For example, in Kokra – Jezersko (Figure 3) beech shows a negative response to June temper- atures (especially Tmax) and a positive response to June precipitation. The values of the CFCs gener- ally decrease from lower to higher altitude, while at 1600 m a.s.l. we observe a positive response to temperatures in July, August and September. Spruce shows a negative response to tempera- tures in July and August and a positive response to precipitation in July at the same gradient, while at 1600 m a.s.l. a positive response to temperatures in May and August is observed. Larch shows a neg- ative response to Tmax in March and a positive re- sponse to summer temperatures, while at altitudes above 1250 m a.s.l. we observe a positive response to May temperatures, especially Tmax, and a pos- 37 Les/Wood, Vol. 71, No. 1, June 2022 Novak, K., de Luis, M., Škrk, N., Straže, A., & Čufar, K.: Tree-ring chronologies of Picea abies, Larix decidua and Fagus sylvatica along altitudinal gradients itive response to August temperatures with lower values of correlation coefficients. Species responses along the Bled – Radovna – Krma slope differ from those at Jezersko. Beech shows a negative response to June temperatures in Hom (518 a.s.l.), while the Radovna and Krma sites respond mainly positively to May temperatures and negatively to March temperatures. Spruce at lower elevations shows a positive influence of January, February and March temperatures, while at ele- vations above 1000 m a positive influence of May temperatures is observed. Larch shows a negative response to Tmax in March and a positive response to temperatures in May. Code / Koda Spe- cies / Dre- vesna vrsta Alti- tude / Nad- mor- ska višina Latitude / Zemljepisna širina Longitude / Zemljepisna dolžina Num- ber of trees / Število dreves Chro- nology Length / Krono- logija Razpon Start / Zače- tek End / Konec m N / S E / V Years / leta Year / leto Year / leto HOM FASY 550 46.401975° 14.117478° 15 146 1874 2019 RA01 FASY 700 46.430571° 13.952667° 14 69 1951 2019 RA02 FASY 750 46.423824° 13.938677° 15 115 1905 2019 RA03 FASY 900 46.435654° 13.928797° 20 188 1833 2020 KR01 FASY 1000 46.386683° 13.907620° 18 239 1780 2018 KR02 FASY 1200 46.370348° 13.888781° 10 198 1822 2019 KR03 FASY 1400 46.366540° 13.879257° 10 296 1724 2019 RA01 LADE 700 46.430571° 13.952667° 20 174 1846 2019 RA02 LADE 750 46.423824° 13.938677° 12 195 1824 2018 RA03 LADE 900 46.435654° 13.928797° 7 84 1936 2019 KR01 LADE 1000 46.386683° 13.907620° 15 181 1833 2013 KR02 LADE 1200 46.370348° 13.888781° 10 154 1866 2019 KR03 LADE 1400 46.366540° 13.879257° 16 141 1880 2020 KR04 LADE 1600 46.366383° 13.869982° 7 328 1692 2019 KR05 LADE 1760 46.368392° 13.867702° 12 378 1642 2019 KR06 LADE 1900- 2040 46.370559° 13.861593° 12 303 1717 2019 HOM PCAB 518 46.359262° 14.110083° 11 110 1910 2019 BLS PCAB 580 46.399197° 14.117837° 12 98 1922 2019 RA01 PCAB 700 46.430571° 13.952667° 20 107 1913 2019 RA02 PCAB 750 46.423824° 13.938677° 23 155 1864 2018 RA03 PCAB 900 46.435654° 13.928797° 12 110 1909 2018 PER PCAB 950 46.402138° 14.021151° 15 81 1939 2019 KR01 PCAB 1000 46.386683° 13.907620° 19 164 1855 2018 KR02 PCAB 1200 46.370348° 13.888781° 9 172 1848 2019 KR03 PCAB 1400 46.366540° 13.879257° 15 116 1904 2019 KR04 PCAB 1600 46.366383° 13.869982° 11 355 1665 2019 KR05 PCAB 1760 46.368392° 13.867702° 4 95 1925 2019 Table 2. Bled – Radovna – Krma, basic information on the sites and chronologies along the gra- dient (short code, species, alti- tude, latitude, longitude, num- ber of trees, useful length of the chronology and its start and end date) for three tree species: European beech (Fagus sylvati- ca) – FASY, European larch (Lar- ix decidua) – LADE, and Norway spruce (Picea abies) – PCAB. Preglednica 2. Bled – Radovna – Krma, osnovni podatki o ras- tiščih in kronologijah vzdolž gra- dienta nadmorske višine (kratka koda, drevesna vrsta, nadmor- ska višina, zemljepisna širina, zemljepisna dolžina, število dre- ves, uporabna dolžina kronolo- gije ter prvo in zadnje leto) za tri drevesne vrste: navadna bukev (Fagus sylvatica)–FASY, evropski macesen (Larix decidua)–LADE in navadna smreka (Picea abies)– PCAB. 38 Les/Wood, Vol. 71, No. 1, June 2022 Novak, K., de Luis, M., Škrk, N., Straže, A., & Čufar, K.: Kronologije širin branik drevesnih vrst Picea abies, Larix decidua in Fagus sylvatica vzdolž gradientov nadmorske višine Figure 3. Kokra-Jezersko correlation function coefficients between tree-ring width indices and climate var- iables (for details, see Figure 4 caption). Slika 3. Kokra – Jezersko korelacijski koeficienti med indeksi širin branik in klimatskimi spremenljivkami (za podrobnosti glejte napis pod sliko 4). 39 Les/Wood, Vol. 71, No. 1, June 2022 Novak, K., de Luis, M., Škrk, N., Straže, A., & Čufar, K.: Tree-ring chronologies of Picea abies, Larix decidua and Fagus sylvatica along altitudinal gradients 40 Les/Wood, Vol. 71, No. 1, June 2022 Novak, K., de Luis, M., Škrk, N., Straže, A., & Čufar, K.: Kronologije širin branik drevesnih vrst Picea abies, Larix decidua in Fagus sylvatica vzdolž gradientov nadmorske višine The presented complex response to climatic parameters with similarities and differences among species and sites requires confirmation with fur- ther studies using principal component analysis (e.g., Čufar et al., 2014, 2008) or other methods. 3.2 COMPARISONS OF CHRONOLOGIES 3.2 PRIMERJAVA KRONOLOGIJ The comparison of chronologies using tBP values shows that at the Kokra – Jezersko gradi- ent most of the chronologies of the same species showed tBP≥4, which is considered to indicate sta- tistically significant similarity (Table 3). Comparison of the chronologies J2, J3, J4 and J6 from locations on the same slope (Figure 2a) showed the highest similarity between nearby altitudes and smallest between the two extreme altitudes at 950 and 1600 m a.s.l. Heteroconnection, i.e. similarity be- tween the chronologies of different species, is ob- served only occasionally (Table 3). The cross-correlations at the Bled – Radov- na – Krma gradient of the same species generally show some similarity between nearby locations and no similarity between lowest and highest el- evations (Table 4). Highest similarity between the chronologies KR1, KR2, KR3 and KR4 could be partly explained by the location of the sites in the valley (Figure 2b) Heteroconnection is observed only oc- casionally (Table 4). 4 CONCLUSIONS 4 ZAKLJUČKI The 47 tree-ring chronologies of Norway spruce (Picea abies), European larch (Larix decid- ua), and European beech (Fagus sylvatica) for two altitudinal ranges in the Kamnik-Savinja Alps and the Julian Alps, starting from the lowlands to the altitudinal limit of species distribution, show varia- bility in tree-ring response to climate. Correlation function coefficients (CFCs) for re- sidual chronologies and monthly minimum (Tmin) and maximum temperatures (Tmax) and precip- itation from the previous January to current De- cember and from the previous and current spring, summer, autumn and current winter vary along the altitudinal gradient. Figure 4. Bled – Radovna – Krma: correlation function coefficients for the residual chronologies of Euro- pean beech (FASY), Norway spruce (PCAB), European larch (LADE) from various elevations and monthly minimum (Tmin, gray lines) and maximum temperatures (Tmax, orange lines) and precipitation (PCP, bars) from the previous January (01p) to current December (12) and the past and current spring (pSPR, SPR), summer (pSUM, SUM), autumn (pAUT, AUT) and current winter (WIN) for the period 1950-2018. CFC val- ues are statistically significant (p<0.05) if >0.2084 or <-0.2084 (for legend, see Figure 3). Slika 4. Bled – Krma: korelacijski koeficienti med rezidualnimi verzijami kronologij za navadno bukev (FASY), navadno smreko (PCAB) in evropski macesen (LADE) ter mesečnimi minimalnimi (Tmin, sive črte) in maksi- malnimi temperaturami (Tmax, oranžne črte) ter padavinami (PCP, stolpci) od preteklega januarja (01p) do decembra (12) tekočega leta, ter za preteklo in tekočo pomlad (pSPR, SPR), poletje (pSUM, SUM), jesen (pAUT, AUT) in zimo (WIN) za obdobje 1950–2018.Vrednosti koeficientov so statistično značilne (p<0,05), če so manjše od -0,2084, ali večje od 0,2084 (za legendo glejte sliko 3). 41 Les/Wood, Vol. 71, No. 1, June 2022 Novak, K., de Luis, M., Škrk, N., Straže, A., & Čufar, K.: Tree-ring chronologies of Picea abies, Larix decidua and Fagus sylvatica along altitudinal gradients Standard dendrochronological parameters (tBP) calculated between the chronologies from the Kokra–Jezersko gradient showed that most of the chronologies of the same species along the gra- dient showed similarity (tBP≥4). In the subset of chronologies from locations on the same slope the greatest similarity was found between the nearby altitudes and smallest between the two extreme al- titudes at 950 and 1600 m a.s.l. Heteroconnection, i.e. similarity between the chronologies of different species, was observed only occasionally. The rela- tionships between the Bled – Radovna – Krma chro- nologies seem to be more complex, and require a detailed study. The presented results show that the relation- ship between tree growth and climate is not only affected by altitude and the corresponding climatic conditions. The complex relationships need to be further investigated with an appropriate methodol- ogy, such as principal component analysis. The database shows great potential for future studies of spruce, larch, and beech from cold envi- ronments in the southern Alps in a time of chang- ing climate. The local chronologies with average lengths of 156 (69-296) years for beech, 139 (57- 355) years for spruce, and 191 (56-378) years for larch also provide a basis for the construction of master chronologies for dating cultural heritage ob- jects. In Slovenia and in the surrounding areas such Table 3. Cross-correlation values of tBP (t-value after Baillie and Picher) between Kokra – Jezersko raw chronologies (J1A-J6, maximum overlap) of Norway spruce, Picea abies, PCAB, European larch, Larix decid- ua, LADE, and European beech, Fagus sylvatica, FASY, from different altitudes. Values tBP≥4 with statisti- cally significant similarity are marked. Preglednica 3. Korelacijske vrednosti tBP (t-vrednost po Baillieju in Picherju) med surovimi kronologijami Kokra – Jezersko (J1A-J6, maksimalno prekrivanje) smreke, Picea abies, PCAB, evropskega macesna, Larix decidua, LADE in evropske bukve, Fagus sylvatica, FASY, z različnih nadmorskih višin. Vrednosti tBP≥4 so statistično značilne in so označene. 42 Les/Wood, Vol. 71, No. 1, June 2022 Novak, K., de Luis, M., Škrk, N., Straže, A., & Čufar, K.: Kronologije širin branik drevesnih vrst Picea abies, Larix decidua in Fagus sylvatica vzdolž gradientov nadmorske višine chronologies are particularly needed for spruce (e.g., Bernabei et al., 2017; Čufar et al., 2020). The sampling material and data are stored in the archive of the Chair for Wood Science at the Department of Wood Science and Technology, Bio- technical Faculty, University of Ljubljana. 5 SUMMARY 5 POVZETEK Predstavljamo mrežo lokalnih kronologij na- vadne smreke (Picea abies), evropskega macesna (Larix decidua) in navadne bukve (Fagus sylvatica) vzdolž dveh gradientov nadmorskih višin na obmo- čju Kokra – Jezersko v Kamniško Savinjskih Alpah in Bled – Radovna – Krma v Julijskih Alpah v Sloveniji. Vsaka od izbranih vrst ima svoje posebnosti z vidika dendrokronologije. Bukev, ki je v Evropi in Sloveniji zelo razširjena, pogosto uporabljamo kot modelno vrsto v dendroekologiji ter za proučevanje učinkov klimatskih sprememb na vegetacijo (npr. Čufar et al., 2008; Di Filippo et al., 2007; Martínez del Castillo et al., 2019, 2022). Redkeje se srečamo z bukovimi predmeti iz preteklih obdobij, ki bi jih želeli dendro- kronološko datirati (Čufar et al., 2012). Smreka je prav tako zelo razširjena v Evropi in Sloveniji. V splošnem je to vrsta hladnih okolij, ki so jo v zadnjih dvesto letih razširili tudi na manj primerna rastišča na nižjih nadmorskih višinah. Pogosto jo proučuje- mo kot modelno drevesno vrsto v dendroekologiji (npr. Martinez del Castillo et al., 2018). Smreka je pogosta v zgodovinskih konstrukcijah, predmetih Table 4. Cross-correlation values of tBP (t-value after Baillie and Picher) between Bled – Radovna – Krma raw chronologies (HOM-KR6, common period 1900-2020) of Norway spruce, Picea abies, PCAB, European larch, Larix decidua, LADE, and European beech, Fagus sylvatica, FASY, from different altitudes. Values of tBP≥4 with statistically significant similarity are marked. Preglednica 4. Korelacijske vrednosti tBP (t-vrednost po Baillieju in Picherju) med surovimi kronologijami Bled – Radovna – Krma (HOM-KR6, skupno obdobje 1900–2020) smreke, Picea abies, PCAB, evropskega macesna, Larix decidua, LADE, in evropske bukve, Fagus sylvatica, FASY, z različnih nadmorskih višin. Vred- nosti tBP≥4 so statistično značilne in so označene. 43 Les/Wood, Vol. 71, No. 1, June 2022 Novak, K., de Luis, M., Škrk, N., Straže, A., & Čufar, K.: Tree-ring chronologies of Picea abies, Larix decidua and Fagus sylvatica along altitudinal gradients in glasbenih inštrumentih. Dendrokronološki signal smreke po Sloveniji zelo variira, ker je v veliki meri odvisen od nadmorske višine, zato za Slovenijo še nismo uspeli sestaviti dobrih referenčnih krono- logij za datiranje (npr. Bernabei et al., 2017; Čufar et al., 2020). Macesen je v Sloveniji manj razširjen kot bukev in smreka (ZGS, 2021), a je pomemben z vidika uporabe lesa, ter tudi za dendrokronološke raziskave. Kot cenjena lesna vrsta je pogost tudi v predmetih kulturne dediščine. Macesen z visokih nadmorskih višin, ki je bil uporabljen za prestižne konstrukcije Benečanov, ima dobro telekonekcijo (Levanič et al., 2001). Tudi dendrokronološki signal macesna je zelo odvisen od nadmorske višine, zato za nižje nadmorske višine še nimamo ustreznih kro- nologij za datiranje. Cilj te študije je bil predstaviti (1) kronologije in njihove glavne značilnosti, (2) kako podnebni de- javniki vplivajo na variiranje širin branik, (3) kako se dendrokronološki signal posamezne vrste spremi- nja z nadmorsko višino in (4) kakšen potencial ima predstavljena podatkovna zbirka za bodoče raziska- ve na področju ekologije in kulturne dediščine. Vzorce lesa za raziskave smo pridobili na različ- nih nadmorskih višinah: (1) Kokra-Jezersko, na 750, 780, 950, 1200, 1250, 1380 in 1600 m in (2) Bled – Radovna – Krma z rastišči na 518, 550, 580, 700, 750, 900, 950, 1000, 1200, 1400, 1600, 1760, 1900, 2040 m n. v. Na vsakem rastišču smo v času redne sečnje iz posekanih dreves na nivoju 4 m od baze drevesa odžagali kolut. V kolikor število posekanih dreves ni bilo zadostno, smo iz rastočih dreves na posame- znem rastišču odvzeli izvrtke. Prečne prereze vzorcev smo gladko zbrusili in jih skenirali pri ločljivosti 1200 dpi. Na slikah smo izmerili širine branik s programom CDendro / Cooo Recorder 9.5 (Cybis Elektronik, 2022 http://www. cybis.se/forfun/dendro/helpcoorecorder7/index. php). Za vizualno in statistično sinhronizacijo smo uporabili program TSAP-Win (Frank Rinn, Heidel- berg, Nemčija) in paket dplR v programu R Studio (Bunn, 2010). Sinhronizirana in datirana zaporedja širin bra- nik smo uporabili za sestavo lokalnih kronologij s programom R Studio z uporabo paketa dplR (Bunn, 2008). Izračunali smo tri različice kronologij: kro- nologijo širin branik ter standardno in rezidualno kronologijo. Za proučevanje vpliva klime na rast dreves smo uporabili rezidualno kronologijo z upo- rabo programa R Studio. Lokalni vremenski podatki za izračune so bili pridobljeni iz podatkovne baze SLOCLIM (Škrk et al., 2021). Opravili smo osnovne primerjave med krono- logijami z izračunom standardnih statističnih vred- nosti (predvsem t-vrednost Baillie in Pilcher, tBP) s programom TSAP-Win. Kronologije smo testirali tudi z vidika teleko- nekcije (ujemanje med kronologijami iste vrste z različnih lokacij) in heterokonekcije (ujemanje med kronologijami različnih drevesnih vrst z istega ob- močja). Za vseh 47 kronologij za 3 drevesne vrste smo predstavili natančne zemljepisne koordinate, števi- lo dreves, uporabno dolžino ter prvo in zadnje leto kronologije (preglednica 1 in 2). Za vseh 47 kronologij 3 drevesnih vrst smo predstavili korelacijske koeficiente (CFC) med inde- ksi širin branik (rezidualne kronologije) ter meseč- nimi minimalnimi (Tmin) in maksimalnimi tempe- raturami (Tmax), padavinami (PCP) od preteklega januarja do decembra tekočega leta, ter za preteklo in tekočo pomlad, poletje, jesen in zimo za obdobje 1950–2018. Rezultati za Kokro – Jezersko (slika 3) kažejo, da se bukev negativno odziva na junijske tempera- ture (zlasti Tmax), pozitivno pa na junijske padavi- ne. Vrednosti korelacijskih koeficientov (CFC) se na splošno zmanjšujejo od nižje proti višji nadmorski višini, medtem ko na nadmorski višini 1600 m opa- žamo pozitiven odziv na temperature v juliju, avgu- stu in septembru. Smreka se negativno odziva na temperature julija in avgusta ter pozitivno na pa- davine julija na večini gradienta, medtem ko je na 1600 m nadmorske višine opazen pozitiven odziv na temperature v maju in avgustu. Macesen kaže negativen odziv na Tmax v marcu in pozitiven odziv na poletne temperature, medtem ko na nadmorski višini nad 1250 m opažamo pozitiven odziv na maj- ske temperature, zlasti Tmax, in pozitiven odziv na avgustovske temperature z nižjimi vrednostmi ko- relacijskih koeficientov. Rezultati na območju Bled – Radovna – Krma se razlikujejo od rezultatov na Jezerskem. Bukev kaže negativen odziv na junijske temperature na Homu (518 m n. v.), medtem ko se na rastiščih v Ra- dovni in Krmi drevesa odzivajo večinoma pozitivno na majske temperature in negativno na marčevske. 44 Les/Wood, Vol. 71, No. 1, June 2022 Novak, K., de Luis, M., Škrk, N., Straže, A., & Čufar, K.: Kronologije širin branik drevesnih vrst Picea abies, Larix decidua in Fagus sylvatica vzdolž gradientov nadmorske višine Smreka na nižjih nadmorskih višinah kaže pozitiven odziv na januarske, februarske in marčevske tem- perature, medtem ko je na nadmorskih višinah nad 1000 m opazen pozitiven vpliv majskih temperatur. Macesen kaže negativen odziv na Tmax v marcu in pozitiven odziv na temperature v maju. Ker je odziv različnih vrst na različnih nadmor- skih višinah na dveh območjih zelo kompleksen, bi bilo dobljene podatke treba analizirati še z drugimi metodami, na primer z analizo glavnih komponent (npr. Čufar et al., 2008, 2014). Navzkrižne korelacije z izračunom parametra tBP (kjer tBP≥4 pomeni statistično značilno podob- nost), kažejo, da je na Jezerskem večina kronologij vsaj v določeni meri podobnih (tBP≥4) (pregledni- ca 3). Primerjava kronologij J2, J3, J4 in J6 z lokacij z enako ekspozicijo (slika 2a) je pokazala največjo podobnost med bližnjimi nadmorskimi višinami in najmanjšo med dvema skrajnima nadmorskima višinama na 950 in 1600 m. Heterokonekcija, tj. primerjava kronologij različnih vrst, je pokazala, da imajo različne vrste na isti lokaciji podoben dendro- kronološki signal samo v posameznih primerih (pre- glednica 3). Korelacije med kronologijami vzdolž gradienta Bled – Radovna – Krma kažejo nekaj podobnosti iste vrste na bližnjih lokacijah. Med kronologijami z najnižjih in najvišjih nadmorskih višin pa ni bilo po- dobnosti v dendrokronološkem signalu (pregledni- ca 4). Najbolj so si bile podobne kronologije KR1, KR2, KR3 in KR4, kar bi lahko delno pojasnili z lego rastišč v isti dolini (slika 2b). Podobnost dendrokro- noloških signalov med vrstami (heterokonekcija) je bila zabeležena le v nekaj primerih (preglednica 4). Predstavljeni rezultati kažejo, da na rast (vari- iranje širin branik) ne vplivajo le nadmorska višina in pripadajoče podnebne razmere. Kompleksne odnose med kronologijami bi bilo treba dodatno raziskati. Prikazani rezultati kažejo na velik potencial po- datkovne zbirke za prihodnje študije dendrokrono- loških posebnosti vrst navadne smreke (Picea abi- es), evropskega macesna (Larix decidua) in navadne bukve (Fagus sylvatica) iz hladnih okolij v južnih Al- pah v spreminjajočem se podnebju. Lokalne krono- logije, ki so v povprečju dolge 156 (69-296) let za bukev, 139 (57-355) za smreko in 191 (56-378) let za macesen, predstavljajo tudi osnovo za izdelavo sestavljenih referenčnih kronologij, ki jih zlasti za smreko potrebujemo za datiranje lesenih predme- tov kulturne dediščine (prim. Čufar et al., 2020). Vzorci za to raziskavo in podatki so shranjeni v arhivu Katedre za tehnologijo lesa na Oddelku za lesarstvo Biotehniške fakultete Univerze v Ljubljani. Pri terenskem in laboratorijskem delu smo bili deležni velike podpore posameznikov, ustanov in podjetij, ki se jim zahvaljujemo za njihovo izjemno pomoč. Zahvaljujemo se tudi za finančno podporo projekta. Podrobnosti so navedene v zahvali. ACKNOWLEDGEMENTS AND FUNDING ZAHVALA IN FINANCIRANJE We would like to thank the numerous individ- uals, organizations, and companies who assisted us in conducting this research: Jeles, proizvodnja in trgovina z lesom (Rok Jelenc and Peter Mohorič), Triglav National Park, Oddelek za varstvo narave (Andrej Arih and Tan- ja Menegalija), Slovenia Forest Service, Območna enota Bled (Janja Lukanc, Rudi Kunstelj and his son Peter, Ferdinand Kokalj), Slovenski državni gozdovi (SiDG) (Štefan Bezovnik) and Gozdno gospodarstvo Bled (Iztok Soklič, Uroš Ambrožič and Matija Ben- edičič), Novomeška nadškofija (Janko Tavčar, Ben- eficij d.o.o.), Ljubljanska nadškofija, forests owners and loggers (Bojan Ambrožič, Matija Pretnar, Luka Karlin, Marko Janša, Janez Lipovec – Psnak), Trgo- vina in servis Resman – Vrbnje, Trgovina in servis Brinca – Lesce, Zavod za varstvo kulturne dediščine Slovenije, Območna enota Kranj (Saša Roškar), The Municipality of Jezersko (Drejc Karničar), Slove- nia Forest Service, Krajevna enota Preddvor (Ivan Srečnik, Tomaž Polajnar, Rolando Nardoni, Igor Nahtigal), Šenkova domačija (Polona V. Karničar in Drejc Karničar), Roblekova Domačija, (Marko Šink- ovec, Matic Šinkovec, Roblek les), Kmetija Spodnji Kovk (Janez Smrtnik), Posek in spravilo lesa Gozd Kokra (Anton Povšnar) We would like to thank Miha Rakar for process- ing the majority of the samples, the members of the Chair for Wood Science for their co-operation and continuous support, Luka Krže, Aleš Straže, Maks Merela, Denis Plavčak, Angela Balzano, Željko Gorišek, Jože Planinšič, Daša Krapež Tomec and the staff of the Department of Wood Science and Tech- nology BF UL for their great support. 45 Les/Wood, Vol. 71, No. 1, June 2022 Novak, K., de Luis, M., Škrk, N., Straže, A., & Čufar, K.: Tree-ring chronologies of Picea abies, Larix decidua and Fagus sylvatica along altitudinal gradients Funding. This study was supported by the project of Ad-Futura (Raziskovalno gostovanje v okviru Javnega razpisa sofinanciranja gostovanj na slovenskih visokošolskih zavodih, 257. 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Poročilo zavoda za gozdove Slovenije o gozdovih za leto 2020. Zavod za gozdove Slovenije. Ljubljana. ZGS. (2022). Karte. Pridobljeno s http://www.zgs.si/gozdovi_sloveni- je/o_gozdovih_slovenije/karte/index.html (20.5.2022) 47 Les/Wood, Vol. 71, No. 1, June 2022 CRITICAL STEPS AND TROUBLESHOOTING IN SAMPLE PREPARATION FOR WOOD AND PHLOEM FORMATION: FROM SAMPLING TO MICROSCOPIC OBSERVATION KRITIČNI KORAKI IN REŠEVANJE TEŽAV PRI PRIPRAVI VZORCEV ZA SPREMLJANJE NASTAJANJA LESA IN FLOEMA: OD VZORČENJA DO OPAZOVANJA POD MIKROSKOPOM Angela Balzano 1* , Katarina Čufar 1 , Luka Krže 1 , Maks Merela 1 UDK 630*811.7:543.456 Received / Prispelo: 9. 6. 2021 Original scientific article / Izvirni znanstveni članek Accepted / Sprejeto: 14. 6. 2022 . Abstract / Izvleč ek Abstract: We present a technical note that supplements published procedures on optimal sample preparation for performing wood and phloem formation analyses. Before beginning sampling, it is important to learn about the characteristics of the tree or shrub species to be investigated. Some tips are given how to use the Trephor tool in the best way, how to remove the outer hard bark (periderm), how microcores should be handled after removal from the tree, and how they should be oriented for embedding in paraffin, and cutting thin sections for microscopy. Possible defects that may result from improper handling are illustrated and discussed. We also present optimal images to accurately identify different cell development stages in phloem and xylem, which is particularly challenging in hardwoods and Mediterranean tree and shrub species. Keywords: tissue sampling, tissue preparation, microscopic slides, microscopy, xylogenesis, phloem formation, troubleshooting Izvleček: Predstavljamo tehnična navodila, ki dopolnjujejo objavljene postopke za optimalno pripravo vzorcev za izvajanje analiz nastajanja lesa in floema. Pred začetkom vzorčenja je potrebno poznati značilnosti drevesne ali grmovne vrste, ki jo želimo preiskovati. Podanih je nekaj nasvetov, kako najbolje uporabiti orodje Trephor, kako odstraniti zunanjo trdo skorjo (periderm), kako ravnati z mikro izvrtki po odvzemu iz debla in kako jih orientirati za vklapljanje v parafin in rezanje tankih rezin za mikroskopske preiskave. Prikazane in razložene so možne napake, ki lahko nastanejo zaradi neustreznega ravnanja v različnih korakih postopka. Predstavljamo tudi optimalne slike tkiv za prepoznavanje različnih razvojnih faz celic v floemu in ksilemu, ki je še posebej zahtevno pri listavcih ter sredozemskih drevesnih in grmovnih vrstah. Ključne besede: odvzem vzorcev tkiva, priprava vzorcev, mikroskopski preparati, mikroskopiranje, nastajanje lesa, nastajanje floema, odpravljanje težav 1 INTRODUCTION 1 UVOD The microcoring technique is increasingly used to obtain samples for monitoring tree responses to changing environmental conditions and assess- ing tree plasticity in the context of climate change. Analysis of microscopic specimens makes it possible to monitor cambial activity and wood and phloem formation in real time, and to distinguish the differ- ent phases of cell division, differentiation, and mat- uration and determine how and when they occur. To this end, samples (usually microcores) contain- ing phloem, cambium, and xylem are taken weekly or biweekly from living trees, for at least one calen- dar year, with particular emphasis on the growing season. The most effective tool for sampling micro- Vol. 71, No. 1, 47-56 DOI: https://doi.org/10.26614/les-wood.2022.v71n01a05 1 Univerza v Ljubljani, Biotehniška fakulteta, Oddelek za lesarstvo, Jamnikarjeva 101, 1000 Ljubljana, SLO * e-mail: angela.balzano@bf.uni-lj.si 48 Les/Wood, Vol. 71, No. 1, June 2022 Balzano, A., Čufar, K., Krže, L., & Merela, M.: Kritični koraki in reševanje težav pri pripravi vzorcev za spremljanje nastajanja lesa in floema: od vzorčenja do opazovanja pod mikroskopom cores is the Trephor tool (Rossi et al., 2006), which was developed for this purpose and first used in 2004. Since its first use, several protocols for sam- pling of microcores and sample preparation have been developed to monitor the different stages of wood and phloem formation (e.g., Rossi et al., 2006; Deslauriers et al., 2015; Prislan et al., 2014a, b, 2022; De Micco et al., 2019; Pace, 2019). In addition, various protocols for preparing anatomical slides (including embedding, cutting and staining) have been developed and improved to achieve high-quality slides for microscopy and quantitative anatomy, including image analysis (Deslauriers et al., 2015; De Micco et al., 2019; Pris- lan et al., 2014a, b, 2022). Appropriate microscopy techniques are critical to accurately identify xylem and phloem cells during differentiation. Various histological and microscopic techniques are used to analyse and identify the different stages of cell divi- sion and differentiation (e.g., Balzano et al., 2021a). Despite the availability of detailed protocols, mistakes can still happen, especially if one is a nov- ice and there are no experts available to help with critical steps. Many technical errors can occur at all stages of the process, from sampling to quan- tification errors. Errors in live tissue collection can jeopardise the entire research. Repeating system- atic errors at this stage runs the risk of collecting hundreds of samples over the course of a year that later prove useless for analyses. The quality of thin sections can also be influ- enced by many factors: the tissue sample (micro- core) itself (density, hardness, homogeneity, etc.), its storage (appropriate solution), sample prepara- tion (possible trimming), orientation (anatomical orientation and orientation of the sample during sectioning), type and sharpness of the blade, and last but not least, the experience and skills of the operator. Such errors may affect the measurement of cells, especially if it is done automatically, making it difficult to count cell number and measure cell dimensions, or leading to inaccurate results and in- terpretations. In our experience, methods should be slightly adjusted on a case-by-case basis, as each species is different. It is also very important to document the species under study well (density, wood and phloem anatomy…) and to perform technical tests before starting the actual experiment. Most of the techniques developed for the study of xylogenesis have been applied to conifers grow- ing in temperate climates, characterized by fairly regular cambial activity and relatively homogene- ous wood structure. In Mediterranean and tropical species, whose wood is often characterized by high density and hardness, the sampling of microcores can be technically challenging. Precautions must also be taken, and existing protocols adapted when sampling shrubs. The goal of this study is to improve the pub- lished protocols, help novices with critical steps, and focus on technical issues that are not neces- sarily addressed in detail in existing protocols. We want to report on the most common mistakes that are made and show possible solutions to over- come them, as well as share our own tips. We want to note some bad examples and explain their caus- es and solutions. 2 MATERIALS AND METHODS 2 MATERIALI IN METODE The standard sample preparation protocol for wood and phloem formation analyses consists of: (1) collection of tissues (microcores) from living trees using a Trephor tool, (2) fixation of tissues with a solution of ethanol, formalin, and acetic acid, (3) storage in ethanol, (4) trimming of micro- cores, (5) dehydration and infiltration with paraffin, (6) embedding in paraffin, (7) trimming and cutting of (transverse) sections with a rotary microtome, (8) staining, (9) embedding of slides on objective glasses, (10) microscopy (different light modes), (11) image acquisition, (12) recognition of tissues and tissue parts, including determination of differ- ent stages of cell and cell wall development, (13) measurement of cells and cell parts (e.g. cell walls) – image analysis, (14) interpretation of results. This article is a technical note describing the critical steps in the sample preparation protocol for wood and phloem formation analyses, and how to better handle the most critical steps in the process that often lead to poor quality microscopic slides and problems in measuring tissue elements (image analysis) and interpreting results. 49 Les/Wood, Vol. 71, No. 1, June 2022 Balzano, A., Čufar, K., Krže, L., & Merela, M.: Critical steps and troubleshooting in sample preparation for wood and phloem formation: from sampling to microscopic observation 3 RESULTS 3 REZULTATI 3.1 SAMPLING AND SAMPLE FIXATION – CRITICAL POINTS 3.1 VZORČENJE IN FIKSIRANJE VZORCEV – KRITIČ- NE TOČKE Before taking tissue samples from trees, one should carefully study the characteristics of the tree species to be studied: its wood and bark anat- omy (how dense and hard is the wood, peculiarities and thickness of the bark) as well as the time and duration of the growing season. Before starting the actual experiment, collect additional specimens for practice. Both novice and experienced scientists may otherwise collect a large number of unsuitable specimens, limiting the possibility of making suita- ble sections. During the experiment it is desirable to collect specimens throughout the calendar year to avoid missing crucial milestones, such as the be- ginning and end of cell production by the cambium. The procedure for sampling and processing microcores is described in Prislan et al. (2022), and this article also includes some critical points and potential errors to avoid. During sampling the use of a Trephor tool wounds the tissue, resulting in the production of wound tissue that is different from the tissues of in- terest. To avoid wounding effects, successive sam- ples for wood and phloem formation should be tak- en in a spiral pattern along the stem, with sampling sites at least 10 cm apart. Two microcores are usu- ally taken from each tree on a given day to have a reserve in case one of the two cores is not suitable. In the case of small trees or shrubs, such as grape- vine (Vitis vinifera) (Figure 1), the sample is taken from a lower location and it is not possible to take two microcores because the sampling would cause too much damage. In this case, it is recommended to select several individuals for analysis and sample them in turn. The quality of thin sections depends on the quality of the microcores, which is influenced by the sharpness of the Trephor cutting edge. A blunt cutting edge will cause damage to the microcores (e.g., compressed, partially crushed, broken, or twisted cores), which directly affects the quality of the thin sections (Figures 1, 2, 3). Choose the correct size of Trephor depend- ing on the species studied. A standard size cutting dimeter (1.9 mm) is appropriate for conifers and hardwoods with small vessels and homogeneous wood structure. A larger Trephor (cutting diameter Figure 1. Sampling tissues from the stem of grapevine (Vitis vinifera): removal of the outer bark (left) and taking microcores with a Trephor tool (right). Slika 1. Vzorčenje tkiv iz stebla vinske trte (Vitis vinifera): odstranitev zunanje skorje (levo) ter odvzem mikro izvrtka z orodjem Trephor (desno). 50 Les/Wood, Vol. 71, No. 1, June 2022 Balzano, A., Čufar, K., Krže, L., & Merela, M.: Kritični koraki in reševanje težav pri pripravi vzorcev za spremljanje nastajanja lesa in floema: od vzorčenja do opazovanja pod mikroskopom Figure 2. Damaged microcores due to errors in sampling tissues from a living tree: (a) sam- ple consisting only of bark (more bark tissue should be removed before sampling), (b) bro- ken sample with crushed cambium (blunt edge of Trephor), (c) sample with too little wood tis- sue. Slika 2. Poškodovani mikro izvrtki zaradi napak pri odvzemu vzorcev iz živih dreves: (a) vzorec vsebuje samo skorjo (pred vzorčenjem bi bilo treba odstraniti več skorje), (b) zlomljen vzorec s porušenim kambijem (topo rezilo Trephorja), (c) vzorec s premalo lesnega tkiva. Figure 3. Sampling errors reflected in the quality of thin sections: (a) cross-section of holm oak (Quercus ilex), whose wood and bark are mainly ray tissue (white arrows) (larger diameter Trephor should be used), (b) sample of stone pine (Pinus pinea) not taken perpendicular to the stem, (c) sample of strawberry tree (Arbutus unedo) which was not properly stored in the fixation medium (the sample was dried out, cambi- um is crushed, phloem is shrunken – white arrows). Slika 3. Napake pri vzorčenju, ki se odražajo v kakovosti tankih rezin: (a) preparat tkiv črničevja (Quercus ilex) večinoma zavzema širok trak (beli puščici), (uporabiti bi bilo treba Trephor večjega premera), (b) vzo- rec pinije (Pinus pinea) ni bil odvzet pravokotno na deblo, (c) vzorec navadne jagodičnice (Arbutus unedo), po odvzemu iz drevesa ni bil pravilno shranjen v fiksacijskem mediju (vzorec se je posušil, kambij je porušen, floem se je skrčil (beli puščici)). 51 Les/Wood, Vol. 71, No. 1, June 2022 Balzano, A., Čufar, K., Krže, L., & Merela, M.: Critical steps and troubleshooting in sample preparation for wood and phloem formation: from sampling to microscopic observation > 2 mm) would help to obtain wider tissue sections for analyses. This is especially important when studying species with wider rays such as beech (Fa- gus) and oaks (Quercus) (Balzano et al., 2021b). Too narrow sections and large rays hinder the analyses, as in the case of Quercus ilex (Figure 3a). Figures 1, 2, and 3 show sampling and com- mon sampling errors and their effects on thin sec- tions. Care must be taken to remove the correct amount of bark to avoid the risk of collecting only bark tissue (Figures 2a, c). The depth of the flap to be removed must be based on the depth of the bark, leaving the uncollapsed phloem and cambi- um intact. If the Trephor is not sharp enough, the bark and wood may separate (Figure 2b). It is very important to pierce the stem perpendicularly in the spot where the bark has been removed (Figure 3b). Hold the Trephor securely and then hammer firm- ly and vigorously until the entire tip of the Trephor penetrates the tissues. It is important to place specimens in the fix- ation medium (FAA) immediately after collection. Since the purpose of fixation is to immobilize pro- teins and cellular components to maintain the structural integrity of the tissues, it is imperative that this step is done quickly. If the sample is not stored properly, the softer tissues such as the cam- bium and parenchyma cells will rapidly collapse and be unusable for measurements (Figure 3c). 3.2 SAMPLE PREPARATION AND CUTTING – CRITI- CAL POINTS 3.2 PRIPRAVA VZORCEV IN REZANJE – KRITIČNE TOČKE Before dehydration and infiltration with paraf- fin, the microcores must be perfectly oriented using a scale magnifier to identify the transverse plane and mark it with a waterproof pencil. In this way, we can easily arrange the sample in the desired ori- entation for cutting after the paraffin embedding. The transverse plane often appears dark- er than the radial plane. If there is any doubt about the orientation, it can be determined by placing a dot in the centre of the end of the mi- crocore. In this way, the ink will follow the fi- bre orientation and reach the cross section. If the sample is not well oriented on the thin sec- tions, the tissue will appear disoriented and will not match the normal structure of the cross-sec- tion, making it impossible to identify and properly measure the cells (Figure 4a). The microcore is later placed at an angle to the mould and with the bark down so that the blade encounters the least possi- ble resistance when cutting. There are several problems when cutting. Be- cause of the very heterogeneous tissue, consisting of thin- and thick-walled cells with different lumen sizes, the microcore often breaks in the area of the cambium with extremely thin-walled cells, which is then destroyed. Therefore, it is extremely difficult to produce thin sections without defects such as cracked and collapsed areas. Perfectly sharp blades for cutting are also es- sential to avoid the specimen splitting, collapsing, tearing off cells and leaving a blade track (Figure 4b, c, d). This is especially true for very dense and hard tissue, where it is often necessary to change the position of the blade for each cut, so that a pre- viously unused, perfectly sharp part of the blade can be used. To achieve perfect cuts, it is also important to properly adjust the angle of the blade correctly. The greater the angle, the less the impact on the specimen; therefore, it is advisable to increase the angle when the bark is harder. The optimum angle is usually between 5 and 10°. Cutting speed is also an important factor when cutting. Cutting too slowly hinders the formation of the “wax ribbon”, while cutting too fast can result in highly compressed sections that are difficult to expand. A cutting thickness of 9 μm is sufficient for studying wood and phloem formation. However, if the bark or wood is too hard, it is recommended to prepare smaller cutting blocks and make thin- ner sections. This will provide less resistance to the knife and allow better sections to be made. A slight variation in the thickness of the section can often solve cutting problems. When it comes to preparing the slide, we can save space by placing as many sections as possi- ble on it. This can only be achieved if the ribbon consisting of paraffin and thin sections is straight. Before cutting, it is useful to trim away any excess wax and tissue to maximize the number of sections that can be placed on a slide. The smaller the block area, the easier it is to make a ribbon. During sec- tioning, water is applied with a fine brush to con- 52 Les/Wood, Vol. 71, No. 1, June 2022 Balzano, A., Čufar, K., Krže, L., & Merela, M.: Kritični koraki in reševanje težav pri pripravi vzorcev za spremljanje nastajanja lesa in floema: od vzorčenja do opazovanja pod mikroskopom stantly keep both the sample and edge of the blade wet, which helps the section to slide across the blade when cutting. The ribbons containing the cross-sections of microcore should be checked under the microscope to be sure you are selecting the best one. Although this is time consuming, it will facilitate and expedite further analyses. Another critical step in sample preparation is the application of glycerine albumin to the slide. The key here is to apply the right amount of glyc- erine albumin; if we apply too much, the end re- sult will be an opaque sample, if we apply too little, the section will be washed away from the slide in further steps. One drop from a generic disposable pipette to measure 3 ml of liquid is more or less the right amount. Excess paraffin must be properly removed from the slides. The clearing agent (e.g., D-limonene) should be changed frequently to avoid dirty sam- ples (Figure 4c). Also, be sure to leave the sample in the staining solution for as long as necessary (15 minutes) to avoid weak staining or overstain- ing. The safranin and astra blue aqueous solution is optimal for this purpose, as it allows observation in brightfield, polarized light, and epi-fluorescence modes (Balzano et al., 2021a). During dehydration prior to embedding in Eu- paral, the alcohol used must not contain water, oth- erwise the slide will fog (Figure 4d). In addition, the Euparal embedding medium must be well dosed to avoid stains on the coverslip, which prevent obser- vation (Figure 4e). If not enough Euparal is applied, air bubbles will form. 3.3 EXPECTED RESULTS 3.3 PRIČAKOVANI REZULTATI Following the protocol (Prislan et al., 2022) and considering the tips suggested here should help to Figure 4. Sample preparation errors: (a) microcore was not well oriented, (b) section with knife marks due to a blunt blade (white arrows), (c) section contaminated, overstained and split due to a blunt blade, (d) “foggy” slide due to presence of water in alcohol, (e) section split due to a blunt blade and traces of Euparal on the coverslip (white arrows). Black bars = 500 µm, white bar = 200 µm. Slika 4. Napake pri pripravi vzorcev in preparatov: (a) mikro izvrtek ni bil dobro orientiran, (b) rezina s po- škodbami zaradi topega rezila (beli puščici), (c) preparat vsebuje nečistoče, preveč obarvan in razcepljen zaradi topega rezila, (d) rezina motna zaradi nepopolne dehidracije (vode v alkoholu), (e) s poškodbami zaradi topega rezila in sledovi euparala na krovnem steklu (beli puščici). Črne merilne daljice = 500 µm, bela merilna daljica = 200 µm. 53 Les/Wood, Vol. 71, No. 1, June 2022 Balzano, A., Čufar, K., Krže, L., & Merela, M.: Critical steps and troubleshooting in sample preparation for wood and phloem formation: from sampling to microscopic observation obtain high-quality slides and images needed for subsequent analyses (Figure 5). For successful analysis of wood and phloem formation, it is critical to obtain high-quality im- ages to accurately identify the different cell devel- opment stages in phloem and xylem, which is par- ticularly challenging in Mediterranean and tropical hardwoods. For the analyses, we need to identify the following: (1) cambial cells and their division; (2) postcambial cell development with the cell enlargement phase; (3) secondary cell wall deposition and lignifi- cation; and (4) cell maturation ending with autolysis of the protoplast and complete lignification of the cell walls. Polarized light is commonly used to distinguish between primary and secondary cell walls and cel- lulose deposition (Figure 6a, b). It helps to distin- guish between enlarging cells that contain only a primary cell wall and those that are in the phase of cell wall thickening with the appearance of a bire- fringent secondary wall. Lignified and unlignified cell walls and tissues can be observed using epifluorescence techniques. Fluorescence imaging of sections stained with an aqueous solution of safranin and astra blue (or oth- er combination of stains) can clearly highlight the contrast between lignified and unlignified cell walls to clearly show the boundary between postcam- bial cells with primary cell walls and those in the phase of secondary cell wall deposition, as well as the progression of lignin deposition in the areas of secondary wall thickening and maturation phases (Figure 6c). Fluorescence also highlight the pres- ence of cytoplasm in the cell lumen, facilitating dif- ferentiation between mature and non-mature cells. Figure 5. Examples of high-quality cross-sections for quantitative image analyses of wood, cambium and phloem of: (a) Pinus halepensis, (b) Fagus sylvatica, and (c) Vitis vinifera. Scale bars = 200 µm. Slika 5. Primeri visokokakovostnih prečnih prerezov za kvantitativno analizo slik tkiv lesa, kambija in floema pri vrstah: (a) Pinus halepensis, (b) Fagus sylvatica in (c) Vitis vinifera. Merilna daljica = 200 µm. 54 Les/Wood, Vol. 71, No. 1, June 2022 Balzano, A., Čufar, K., Krže, L., & Merela, M.: Kritični koraki in reševanje težav pri pripravi vzorcev za spremljanje nastajanja lesa in floema: od vzorčenja do opazovanja pod mikroskopom 4 CONCLUSIONS 4 ZAKLJUČKI Monitoring xylogenesis and phloem forma- tion provides useful information about xylem and phloem formation in real time, but requires specific tools, techniques, and skills for successful sampling, preparation of high-quality sections, and the abili- ty to recognize the cells and the different stages of cell differentiation. The aforementioned skills are preferably acquired with the help of experts. If this is not possible, experience using existing protocols and technical references must be gained to master the critical steps. Many errors can occur at all stag- es of the process, from sampling to sectioning and quantification errors, especially if one is a novice in this field. This article is designed to share our experiences and help novices to not get discour- aged and avoid the most common mistakes. First, we recommend acquiring knowledge of the species one intends to study. In our experience, protocol procedures should be adapted to it. Practicing on test samples can also help to gain the necessary experience without compromising the actual sam- ples used in the research. It is hoped that the tips we have provided in these technical notes will help beginners to deal with some of the critical steps in the procedure that are not addressed in existing protocols. Figure 6. Cross-section of phloem, cambium and xylem of Pinus halepensis: (a) under a light microscope, bright field mode, safranin-astra blue staining, (b) under polarized light allowing to distinguish between enlarging tracheids (white arrow) containing only a primary cell wall and tracheids in the phase of cell wall thickening, which contain a birefringent, shiny secondary wall, (c) progress of lignin deposition in the (shiny) areas of the middle lamella and secondary wall, starting from the middle lamella in the cell corners (white arrow). Scale bars = 500 µm. Slika 6. Prečni prerez floema, kambija in ksilema alepskega bora (Pinus halepensis): (a) s svetlobnim mi- kroskopom, svetlo polje, obarvanje s safranin-astra modrim, (b) s polarizirano svetlobo, ki omogoča raz- likovanje med traheidami v fazi rasti (bela puščica), ki vsebujejo le primarno celično steno, in traheidami v fazi odlaganja celične stene, ki vsebujejo optično aktivno sekundarno celično steno, ki se sveti, (c) potek odlaganja lignina (svetleča mesta) v srednji lameli in sekundarni steni, z začetkom v vogalih celic (bela puščica). Merilne daljice = 500 µm. 55 Les/Wood, Vol. 71, No. 1, June 2022 Balzano, A., Čufar, K., Krže, L., & Merela, M.: Critical steps and troubleshooting in sample preparation for wood and phloem formation: from sampling to microscopic observation 5 SUMMARY 5 POVZETEK Tehnika odvzema mikro izvrtkov in priprava preparatov za mikroskopijo se danes najpogoste- je uporablja za spremljanje kambijeve aktivnosti ter nastajanja lesa in floema, med drugim tudi za oceno plastičnosti dreves v kontekstu podnebnih sprememb. Mikroizvrtke iz debel dreves jemljemo z orodjem Trephor (Rossi et al., 2006), ki je bilo prvič uporabljeno leta 2004. Razvitih je bilo več protoko- lov za vzorčenje in pripravo vzorcev mikroizvrtkov za mikroskopske analize kambija, ksilema in floema (na primer Deslauriers et al., 2015; Prislan et al., 2014a, b, 2022; De Micco et al., 2019; Pace, 2019; Balzano et al., 2021a). Namen tega prispevka je nadgraditi objavljene protokole, da bi začetnikom pomagali pri premagovanju kritičnih korakov med postopkom, ki v obstoječih protokolih niso nujno podrobno obravnavani. Predstavljamo najpogostej- še napake in na podlagi naših izkušenj podajamo nasvete, kako se jim izogniti. Najnovejši protokol Prislan et al. (2022) pripo- ročamo kot referenco, kamor dodajamo naše nas- vete. Pred začetkom novega projekta predlagamo, da skrbno preučite značilnosti drevesne vrste, ki jo želite preučiti (anatomija lesa in skorje, čas in traja- nje rastne sezone ipd.). Po naših izkušnjah je treba protokol prilagoditi glede na značilnosti preisko- vane vrste. Predlagamo tudi odvzem nekaj doda- tnih vzorcev za preizkus metode. Da ne bi zamudili ključnih mejnikov (npr. začetek in konec kambijeve aktivnosti), je zaželen odvzem vzorcev preko ce- lotnega koledarskega leta. Da bi se izognili učinku poškodovanj, moramo mikro izvrtke odvzemati spiralno vzdolž debla, pri čemer morajo biti mesta vzorčenja med seboj oddaljena vsaj 10 cm. Običaj- no se z vsakega drevesa na določen dan odvzameta dva mikro izvrtka, da imamo enega za rezervo. Pri majhnih drevesih ali grmih, kot je na primer vinska trta (slika 1), se prvi vzorec odvzame spodaj in ni priporočljivo odvzeti dveh mikroizvrtkov na vzorče- nje, ker bi to povzročilo prevelike poškodbe. V tem primeru lahko za analizo izberemo več osebkov in jih vzorčimo izmenoma. Rezilo Trephorja mora biti ostro. Topo rezilo bi povzročilo poškodbe na mikro izvrtku, kar bi posre- dno vplivalo tudi na kakovost tankih rezin (prepara- tov) (slike 1, 2, 3). Glede na vrsto, ki jo proučujemo, izberemo pravo velikost Trephorja. Večji Trephor (premer rezila > 2 mm) omogoča, da odvzamemo širši pas tkiva za analize, kar je pomembno zlas- ti pri preučevanju vrst s širšimi trakovi. Odstraniti moramo ustrezno količino zunanje skorje, da se izognemo tveganju, da bi mikro izvrtek vseboval predvsem skorjo in premalo drugih tkiv (lesa) (sliki 2a, c). Vbod s Trephorjem opravimo pravokotno na deblo na mestu, kjer je bil odstranjen zunanji del skorje (slika 3b). Pomembno je, da vzorce takoj po odvzemu vložimo v fiksacijsko sredstvo (FAA), da preprečimo poškodbe mehkejših tkiv (slika 3c). Pred nadaljnjo obdelavo morajo biti mikro izvrtki pravilno orientirani, sicer bo tkivo na prepa- ratih deorientirano, kar bo onemogočilo prepozna- vanje in merjenje celic (slika 4a). Bistveno je tudi, da pri rezanju uporabimo popolnoma ostra rezila, da na preparatu ne bi prišlo do razpok, kolapsa, »iz- puljenih« celic ter da preparat ne bi vseboval sledi rezila, ki jih vidimo kot pas raztrganih celic (slike 4b, c, d). Pri rezanju je pomembno, da nastavimo pra- vilen kot rezil (med 5° in 10°) in prilagodimo hitrost rezanja. Težave pri rezanju lahko pogosto rešimo že z manjšo spremembo debeline rezine. Še en kritičen korak pri pripravi vzorca je nanos glicerin albumina na objektno steklo, ki »prilepi« preparat na steklo. Topila za zadnje korake pri dehi- draciji tkiv je treba pogosto menjavati, da se izogne- mo nečistočam v preparatu (slika 4c). Pri dehidraciji uporabljeni alkohol ne sme vsebovati vode, sicer se vklopni medij zamegli (slika 4d). Poleg tega je treba vklopni medij Euparal primerno dozirati, da se izog- nemo nastanku madežev na objektnem ali pokriv- nem steklu (slika 4e) in da se v preparat ne »uja- mejo« zračni mehurčki. Z upoštevanjem protokola (Prislan et al., 2022) in tukaj predlaganih nasvetov bi morali nastati visokokakovostni preparati in slike, primerne za kvantitativno analizo slike (slika 5). Pri analizah nastajanja lesa in skorje moramo prepoznati različne vrste celic in tkiv v lesu in skorji (floemu) ter njihovo razvojno stopnjo. Za razliko- vanje med primarnimi in sekundarnimi celičnimi stenami običajno uporabljamo mikroskopijo s po- larizirano svetlobo (slika6 a, b). Z epi-fluorescenčno mikroskopijo pa lahko poudarimo kontrast med lig- nificiranimi in nelignificiranimi celičnimi stenami, da prepoznamo potek odlaganja lignina na obmo- čjih srednje lamele in sekundarne stene ter nasta- nek popolnoma diferenciranih zrelih celic (slika 6c). Upamo, da bodo ob upoštevanju predstavljenih na- 56 Les/Wood, Vol. 71, No. 1, June 2022 Balzano, A., Čufar, K., Krže, L., & Merela, M.: Kritični koraki in reševanje težav pri pripravi vzorcev za spremljanje nastajanja lesa in floema: od vzorčenja do opazovanja pod mikroskopom vodil tudi začetniki lahko premostili kritična mesta v postopku in dosegli želene rezultate. ACKNOWLEDGEMENTS ZAHVALA The study was supported by the Slovenian Re- search Agency ARRS, program P4-0015. We thank Prof. Dr. Veronica De Micco, for providing samples of Vitis vinifera. REFERENCES VIRI Balzano, A., Čufar, K., & De Micco, V. (2021a). Cell-wall fluorescence highlights the phases of xylogenesis. IAWA Journal, 43 (1, 2), 80-91, DOI: https://doi.org/10.1163/22941932-bja10080 Balzano, A., Čufar, K., & De Micco, V. (2021b). Xylem and phloem for- mation dynamics in Quercus ilex L. at a dry site in Southern Italy. Forests, 12(2), 188, DOI: https://doi.org/10.3390/f12020188 De Micco, V., Carrer, M., Rathgeber, C. B., Camarero, J. J., Voltas, J., Cherubini, P ., & Battipaglia, G. (2019). From xylogenesis to tree rings: wood traits to investigate tree response to environmen- tal changes. IAWA journal, 40(2), 155-182, DOI: https://doi. org/10.1163/22941932-40190246 Deslauriers, A., Rossi, S., & Liang, E. (2015). Collecting and processing wood microcores for monitoring xylogenesis. In Plant micro- techniques and protocols (pp. 417-429). Springer, Cham. DOI: https://doi.org/10.1007/978-3-319-19944-3_23 Pace, M. R. (2019). Optimal preparation of tissue sections for light- microscopic analysis of phloem anatomy. In Phloem (pp. 3-16). Humana, New York, NY . DOI: https://doi.org/10.1007/978-1- 4939-9562-2_1 Prislan, P ., Gričar, J., & Čufar, K. (2014a). Wood sample preparation for microscopic analysis – protocol. URL: http://www.streess- -cost.eu/images/stories/Documents/protocol_wood_sample_ preparation_for_microscopic_analysis.pdf Prislan, P ., Martinez del Castillo, E., Krže, L., Habjan, P ., & Merela, M. (2014b). Wood sample preparation for microscopic analysis film. URL: https://www.youtube.com/watch?v=FUddCGVr0bY Prislan, P ., Martinez del Castillo, E., Skoberne, G., Špenko, N., & Gri- čar, J. (2022). Sample preparation protocol for wood and phlo- em formation analyses. Dendrochronologia, 73, 125959, DOI: https://doi.org/10.1016/j.dendro.2022.125959 Rossi, S., Anfodillo, T., & Menardi, R. (2006). Trephor: a new tool for sampling microcores from tree stems. Iawa Journal, 27(1), 89- 97, DOI: https://doi.org/10.1163/22941932-90000139 57 Les/Wood, Vol. 71, No. 1, June 2022 DENDROKRONOLOGIJA IN ABSOLUTNO DATIRANJE KOLIŠČ NA LJUBLJANSKEM BARJU DENDROCHRONOLOGY AND ABSOLUTE DATING OF PILE-DWELLINGS IN LJUBLJANSKO BARJE Katarina Čufar 1* , Maks Merela 1 , Luka Krže 1 , Anton Velušček 2 UDK 630*561.24:904 Prispelo / Received: 20. 6. 2021 Pregledni znanstveni članek / Review scientific article Sprejeto / Accepted: 29. 6. 2022 . Izvleček / Abstract Izvleček: Na 16 koliščih na Ljubljanskem barju v Sloveniji je bilo med leti 1995 in 2021 z arheološkimi izkopavanji zbranih več kot 8.800 vzorcev z vodo napojenega arheološkega lesa. Večina vzorcev je bilo odvzetih iz pilotov, zabitih v zemljo, na katerih so bila zgrajena bivališča. Približno 20 % vzorcev je bilo iz lesa hrasta (Quercus sp.) in jesena (Fraxinus sp.), z več kot 45 branikami, ki jih je bilo mogoče vključiti v dendrokronološke analize in sestaviti kronologije širin branik za večino najdišč. Datiranje z uporabo dendrokronologije, radiokarbonskega datiranja in metode wiggle matching ter telekonekcije z nemško-švicarsko referenčno kronologijo so omogočili na leto natančno absolutno datiranje hrasta v časovnem okviru 3771–3330 pr. Kr. (kronologija BAR-3330), medtem ko so bili natančni radiokarbonski datumi pridobljeni za kronologije, ki pokrivajo obdobji 3285–3109 ± 14 kal. pr. Kr. (SG-VO) in 2659– 2417 ± 18 kal. pr. Kr. (ZA-QUSP1). Potencial kronologij jesena, zlasti tistih iz 3. tisočletja pr. Kr., kjer ta vrsta prevladuje, še ni bil v celoti izkoriščen. Ključne besede: koliščarske naselbine, Ljubljansko barje, neolitik, eneolitik, arheološki les, dendrokronologija, C14 wiggle-matching, absolutno datiranje Abstract: Between 1995 and 2021, archaeological excavations at 16 sites in Ljubljansko barje, Slovenia, collected more than 8,800 samples of waterlogged archaeological wood, mostly from piles driven into the ground on which dwellings were built. About 20% of the samples were from oak (Quercus sp.) and ash (Fraxinus sp.) trees with more than 45 tree-rings, which could be included in the dendrochronological analyses, and tree-ring chronologies could be established for most sites. Dating by dendrochronology, radiocarbon dating, and wiggle matching, as well as teleconnection with the German-Swiss reference chronology, allowed absolute dating of oak in the time frame 3771–3330 BC (BAR-3330 chronology), while precise 14C dates were obtained for chronologies covering the periods 3285–3109 ± 14 cal BC (SG-VO) and 2659–2417 ± 18 cal BC (ZA-QUSP1). The potential of the ash wood chronologies, especially those of the 3rd millennium BC, when this wood species was predominant, has not yet been fully exploited. Keywords: pile dwellings, Ljubljansko barje, Neolithic, Eneolithic, archaeological wood, dendrochronology, radiocarbon wiggle-matching, absolute dating 1 UVOD 1 INTRODUCTION Ljubljansko barje je edino območje z ohranje- nimi arheološkimi ostanki prazgodovinskih koliščar- skih bivališč, odkritih v Sloveniji. Predstavlja plitvo mokrišče v bazenu tektonskega izvora s površino 163 kvadratnih kilometrov, ki je občasno lahko po- plavljeno zaradi taljenja snega ali obilnih padavin. Od poznega pleistocena do zgodnjega poznega ho- locena je območje prekrivalo plitvo jezero. Prva kolišča je leta 1875 odkril Karl Deschmann v bližini vasi Studenec, zdaj Ig (Leghissa, 2021). Po Vol. 71, No. 1, 57-70 DOI: https://doi.org/10.26614/les-wood.2022.v71n01a06 1 Univerza v Ljubljani, Biotehniška fakulteta, Oddelek za lesarstvo, Jamnikarjeva 101, 1000 Ljubljana, SLO * e-pošta: katarina.cufar@bf.uni-lj.si; telefon: 01-320-3645 2 Znanstvenoraziskovalni center SAZU, Inštitut za arheologijo, Novi trg 2, 1000 Ljubljana, SLO 58 Les/Wood, Vol. 71, No. 1, June 2022 Čufar, K., Merela, M., Krže, L., & Velušček, A.: Dendrochronology and absolute dating of pile-dwellings in Ljubljansko Barje odkritju in pionirskih izkopavanjih v letih 1875– 1877 je bilo izvedenih več raziskovalnih akcij, npr. 1907–1908 (W. Schmid), 1953–1989 (J. Korošec, T. Bregant) in več akcij po letu 1992 (Velušček, 2019). Leta 2011 je Unesco pomen dveh različnih skupin kolišč iz okolice Iga prepoznal z vpisom na seznam svetovne dediščine (slika 1b) (Unesco, 2022). Inštitut za arheologijo Znanstvenorazisko- valnega centra Slovenske akademije znanosti in umetnosti (IA ZRC SAZU) je koordiniral serijo razi- skav, ki so se začele leta 1995 in še vedno potekajo. V tej kampanji so bile uvedene sodobne metode vzorčenja, ki so jih razvili pri raziskavah koliščarskih naselbin na območju Alp. Tu imajo poseben pomen raziskave arheološkega lesa in uvajanje dendrokro- nologije, ki jo je bilo v Sloveniji potrebno vpeljati za raziskave v arheologiji (npr. Čufar et al., 1999). Interdisciplinarne raziskave so vključevale tudi ra- zvoj palinologije, arheobotanike in arheozoologije ter sodelovanje z drugimi področji, kot so arheome- trija, tekstilno inženirstvo, metalurgija, geologija in medicina (npr. Velušček 2004a, 2009). Slika 1. Koliščarske na- selbine: (a) replika ko- lišča iz 2. tisočletja pr. Kr. v koliščarskem mu- zeju Unteruhldingen ob Bodenskem jezeru v Nemčiji in (b) lokaci- je 111 prazgodovinskih koliščarskih najdišč v Alpah iz obdobja od leta 5000 do 500 pr. Kr. na Unescovem sezna- mu svetovne dediščine. Ljubljansko barje ima najbolj jugovzhodno lego. Zemljevid: Nina Škrk, Google Earth, 2020. Figure 1. Lake dwell- ings: (a) replica of a 2nd millennium BC pile dwelling at the Pile Dwelling Museum in Unteruhldingen on Lake Constance in Ger- many and (b) 111 pre- historic pile dwellings in the Alps dating from 5,000 to 500 BC that are on the World Her- itage List UNESCO. Lju- bljansko barje has the most southeastern lo- cation. Map: Nina Škrk, Google Earth, 2020. 59 Les/Wood, Vol. 71, No. 1, June 2022 Čufar, K., Merela, M., Krže, L., & Velušček, A.: Dendrokronologija in absolutno datiranje kolišč na Ljubljanskem barju Dendrokronološke raziskave, brez katerih si danes ne moremo zamišljati sodobnih arheoloških raziskav lesa v vlažnih okoljih, so opravili na Od- delku za lesarstvo Biotehniške fakultete Univerze v Ljubljani (OL BF) (npr. Čufar & Velušček, 2012; Ču- far et al., 2013; Velušček & Čufar, 2014). Od usta- novitve dendrokronološkega laboratorija leta 1993 so se za ta namen posvetili sestavljanju referenč- nih kronologij in proučevanju dendrokronološkega potenciala hrasta in drugih lesnih vrst v Sloveniji (npr. Čufar & Levanič, 1999; Čufar et al., 2008a), ter tudi temeljnim raziskavam na področju dendroeko- logije hrasta južno od Alp (npr. Čufar et al., 2014), dendroklimatologije (npr. Čufar et al., 2008b) ter lastnosti in možnosti konserviranja z vodo napo- jenega arheološkega lesa (npr. Čufar et al., 2002; Čufar et al., 2008c; Balzano et al., 2022), kar je vse prispevalo k celoviti obravnavi lesa in uporabi dendrokronologije v arheologiji. Po 27 letih dendrokronoloških raziskav na ko- liščih Ljubljanskega barja je bilo doseženih nekaj pomembnih uspehov, ki še niso bili sistematično predstavljeni domači javnosti. Ob velikem razisko- valnem potencialu tega materiala ostaja tudi več odprtih izzivov. Vse to predstavljamo v tem prispev- ku. 2 MATERIAL IN METODE 2 MATERIALS AND METHODS 2.1 ARHEOLOŠKE RAZISKAVE 2.1 ARCHAEOLOGICAL RESEARCH Med leti 1995 in 2021 je bilo na 16 koliščih na Ljubljanskem barju opravljenih 29 izkopavanj in te- renskih pregledov, kjer so pridobili les in druge ar- heološke najdbe (preglednica 1). Vse raziskave, ra- zen na koliščih Črnelnik, Špica in Veliki Otavnik Ib, je vodil Inštitut za arheologijo ZRC SAZU. Na zbranem arheološkem materialu so bile opravljene sistema- tične interdisciplinarne raziskave (npr. Velušček, 2004a, 2006, 2009, 2020). Da bi za dendrokronološke analize pridobi- li zadostno količino lesa, je zbiranje ostankov lesa in drugih najdb potekalo na predhodno izkopanih območjih, v rečnih strugah, drenažnih jarkih in z manjšimi izkopavanji ali vkopi na različnih lokacijah (slika 2). Območje nekaterih kolišč so izkopavali v več etapah (preglednica 1). 2.2 ANALIZE LESA–IDENTIFIKACIJA, DENDROKRO- NOLOGIJA, RADIOKARBONSKO DATIRANJE 2.2 WOOD ANALYSES–IDENTIFICATION, DENDRO- CHRONOLOGY , RADIOCARBON DATING Med leti 1995 in 2021 je bilo zbranih 8829 vzorcev z vodo napojenega arheološkega lesa, veči- noma iz pilotov kolišč (preglednica 1). Na Oddelku za lesarstvo smo les obdelali, tako da smo pripravili približno 10 cm debele odrezke s prečnim prere- zom. Tako pripravljene vzorce smo globoko zamr- Slika 2. Terensko delo in zbiranje arheološkega materiala na koliščarskih naselbinah na Ljubljanskem barju: (a) sonda, (b) drenažni jarek, (3) dno reke z vidnimi ostanki lesenih pilotov. Figure 2. Archaeological field work on pile-dwelling settlements to collect arcaheological material and wood in Ljubljansko barje: (a) excavation probe, (b) drainage ditch, (3) riverbed with visible remains of wooden piles. 60 Les/Wood, Vol. 71, No. 1, June 2022 Čufar, K., Merela, M., Krže, L., & Velušček, A.: Dendrochronology and absolute dating of pile-dwellings in Ljubljansko Barje Slika 3. Delo z arheološkim lesom s koliščarskih naselbin: (a) obdelava površine globoko zamrznjenega vzorca – izdelava preparata za identifikacijo lesa, (b) vzorci pilotov iz celih in cepljenih debel z obdelanimi prečnimi prerezi, (c) priprava arheološkega lesa za skladiščenje v napojenem stanju in vakuumu v zavar- jenih polietilenskih vrečkah. Prečni prerez lesa hrasta (Quercus sp.) pod: (d) stereo lupo, (e) svetlobnim mikroskopom in (f) elektronskim vrstičnim mikroskopom. (Foto: Andraž Benedik a-e, Angela Balzano f). Figure 3. Working with archaeological wood from pile-dwelling sites: (a) surface smoothing of a frozen sample – slide preparation for wood identification, (b) pile samples of whole and split logs with smoothed cross-sections, (c) preparation of archaeological wood for storage in water-saturated state under vacuum in polyethylene bags. Cross-section of oak wood (Quercus sp.) under (d) stereomicroscope, (e) light micro- scope, and (f) scanning electron microscope (photos: Andraž Benedik a-e, Angela Balzano f). Slika 4. Postopek datiranja: (a) merjenje širin branik, les je na merilni mizici pod stereo lupo, (b) oznake širin branik na posnetku lesa, (c) zaporedje širin branik enega kosa lesa z označenimi mesti odvzema dveh vzorcev za radiokarbonsko in wiggle-matching analizo – razlika v starosti je 86 let, (d) kalibriranje radiokar- bonskih datumov z metodo wiggle matching in rezultat datacije mlajše branike, (e) zaporedje “c” (rdeča črta) in zapredja širin branik drugih vzorcev iz kolišča (črne črte) v sinhronem položaju, vsi vzorci so datirani. Figure 4. Dating process: (a) measurement of tree-ring widths of wood on a measuring table under a ster- eomicroscope, (b) tree-ring widths on the image, (c) recording of the tree-ring series of a sample with the sampling points marked for radiocarbon and wiggle matching analysis–the age difference between two samples is 86 years, (d) the calibration of radiocarbon dates by the wiggle matching method and the result of dating of the last ring, (e) the series of ‘c’ (red curve) and other samples from the site (black lines) in cross-dated position – all of them are dated. 61 Les/Wood, Vol. 71, No. 1, June 2022 Čufar, K., Merela, M., Krže, L., & Velušček, A.: Dendrokronologija in absolutno datiranje kolišč na Ljubljanskem barju znili pri temperaturi -22 °C in nato na zamrznjenih vzorcih zgladili prečno površino za pregled pod ste- reo mikroskopom in makroskopsko identifikacijo lesa (slika 3a, b, c, d). V kolikor makroskopska iden- tifikacija lesa ni bila mogoča, smo pripravili tanke preparate za mikroskopsko identifikacijo lesa (slika 3e) in jih identificirali ob uporabi standardnih klju- čev za identifikacijo lesa (npr. Schoch et al., 2004; Čufar, 2006; Čufar & Merela, 2014). Na vseh vzorcih lesa smo najprej prešteli bra- nike in izmerili oz. ocenili premer debla. Dendro- kronološko merjenje širin branik smo opravili na vzorcih hrasta, jesena, bukve in jelke, ki so imeli 45 ali več branik. Sledilo je sinhroniziranje zaporedij širin branik posameznih vzorcev in združevanje v kronologije za posamezno lesno vrsto in koliščarsko naselbino. Za vsako kronologijo smo iz enega ali več repre- zentativnih vzorcev odvzeli les za radiokarbonsko datiranje (Čufar & Kromer, 2004). Ob naraščanju števila radiokarbonskih datumov in dendrokronolo- ški določitvi razlike v številu branik oz. let med radi- okarbonsko datiranimi vzorci je bila možna uporaba metode wiggle-matching in bolj natančna umesti- tev kronologij v čas, v najboljšem primeru ± 10 let (Čufar et al., 2010). Absolutno dendrokronološko datiranje nam je po 20 letih raziskav uspelo z dendrokronološko tele- konekcijo z nemško-švicarsko referenčno kronologi- jo; tako smo na leto natančno datirali več kronologij iz sredine 4. tisočletja pr. Kr. (Čufar et al., 2015). 3 REZULTATI IN RAZPRAVA 3 RESULTS AND DISCUSSION Med 8829 vzorci arheološkega lesa so bile iden- tificirane vrste lesa veliki jesen (Fraxinus excelsior), hrast (Quercus robur in Quercus petraea), črna jelša (Alnus glutinosa), javor (Acer sp.), vrba (Salix sp.), topol (Populus sp.), leska (Corylus avellana), beli gaber (Carpinus betulus), bukev (Fagus sylvatica), jelka (Abies alba), brest (Ulmus sp.) in posamezni predstavniki drugih vrst (slika 5a) (prim. Čufar & Ve- lušček, 2012). Nabor in odstotni deleži uporabljenih lesnih vrst so se med kolišči zelo razlikovali (preglednica 1, slika 5b). Jesen je skupno predstavljal dobro polovi- co vzorcev, hrast dobro četrtino. Hrasta je najmanj na koliščih Resnikov prekop (0 %), Parte-Iščica (2 %) in Dušanovo (2 %), na ostalih koliščih je bil delež hrasta 16–72 %. Odstotni deleži jesena so znašali 20–72 % in so bili največji tam, kjer je bilo hrasta Slika 5. Izbor lesa na koliščarskih naselbinah: (a) deleži lesnih vrst (rodov), raziskanih med leti 1995-2021 in (b) variiranje deležev vzorcev hrasta (Quercus) in jesena (Fraxinus) na koliščarskih naselbinah (za pomen kratic in obdobja kolišč glejte preglednico 1). Figure 5. Selection of wood in the pile-dwelling settlements: (a) proportions of wood species (genera) ana- lysed between 1995-2021 and (b) variation in the proportions of oak (Quercus) and ash (Fraxinus) samples from the oldest to the youngest pile dwelling (for the meaning of the abbreviations and the time of the dwellings, see Table 1). 62 Les/Wood, Vol. 71, No. 1, June 2022 Čufar, K., Merela, M., Krže, L., & Velušček, A.: Dendrochronology and absolute dating of pile-dwellings in Ljubljansko Barje malo. Na vseh koliščih so uporabljali predvsem les listavcev, ki na Ljubljanskem barju in v okoliškem hribovju uspevajo tudi danes. Od iglavcev so občas- no uporabili samo jelko in v redkih posebnih prime- rih tiso (na sliki 5a med ostalimi vrstami), ki smo ju tako kot bukev in brest našli samo na posameznih koliščih (Čufar & Velušček, 2012). Izbor lesnih vrst je bil praviloma odvisen od lege kolišča, če se je to nahajalo bliže jezeru oz. poplavni ravnici ali bliže kraškim pobočjem na jugu Ljubljanskega barja (To- lar et al., 2011). Na izbor je vplivala tudi razpoložlji- vost lesa, ki so ga, če je bilo mogoče, posekali v bli- žini kolišč. Največ dreves za pilote je imelo premer 7–10 cm (Čufar et al., 1999; Out et al., 2020). Če je bil premer dreves večji od 14 cm, so debla po dol- gem razcepili na 4 ali več delov (slika 3b), tako da so pridobljene pilote lahko zabili v zemljo oz. jezersko dno. Čeprav številni viri poročajo, da so prebivalci kolišč zaradi velikih potreb po lesu gospodarili z gozdovi (npr. Bleicher & Staub, 2022), tega do sedaj za Ljubljansko barje še nismo mogli dokazati, kar kaže tudi raziskava, v katero je bila vključena nasel- bina Stare gmajne (Out et al., 2020). Le manjši delež (približno 20 %) vzorcev hrasta in jesena je imel 45 ali več branik, kar je bil naš krite- rij, da smo jih vključili v dendrokronološke raziska- ve. V prvi fazi raziskav smo se osredotočili predvsem na hrast, ki je najpogostejši in najpomembnejši les Št. / No. Kolišče / Site Koda / Code Leta izkopavanj / Years of excavations Število vzorcev / No. of Wood Samples Quercus % / Quercus % Fraxinus % / Fraxinus % Zadnji da- tum pr.Kr. / End Date BC Metoda / Dating Method 1 Resnikov prekop RP 2002 34 0 24 ~4600 14C 2 Črnelnik CEN 2014 39 72 26 3694 Dendro 3 Trebež TR 2017 83 25 47 3649 Dendro 4 Strojanova voda STV, SV 2012 351 16 62 3578 Dendro 5 Hočevarica HOC, HO 1995, 1998 361 37 51 3570 Dendro 6 Maharski prekop MP 2005 234 35 30 3487 Dendro 7 Črešnja pri Bistri CR 2003 124 49 20 3407 Dendro 8 Spodnje mostišče SM1+2 1996, 1997 690 59 22 3351 Dendro 9 Stare gmajne SG 2002, 2004, 2006, 2007, 2021 984 36 44 3109±14 Wiggle 10 Veliki Otavnik Ib VO 2006 30 57 20 3108±14 Wiggle 11 Blatna Brezovica BB 2003 170 51 32 ~3071 14C 12 Parte-Iščica PI 1997, 1998 1265 2 70 ~2610 14C 13 Dušanovo (in Črn graben) DU, CG 2010, 2013, 2017 305 2 72 ~2490 14C 14 Parte PAR 1996 242 33 62 2458±18 Wiggle 15 Špica SPC 2009, 2010 2452 21 60 ~2450 16 Založnica ZAL, ZA 1995, 1999, 2001, 2009 1465 30 55 2417±18 Wiggle Preglednica 1. Koliščarske naselbine na Ljubljanskem barju: leta izkopavanj, število zbranih vzorcev lesa, odstotni delež vzorcev hrasta (Quercus) in jesena (Fraxinus) ter končni datumi kronologij posameznih ko- lišč, datiranih s pomočjo dendrokronologije (Dendro), radiokarbonskih analiz (14C) ali metode wiggle-ma- tching (Wiggle). Table 1. Pile-dwelling settlements in Ljubljansko barje, with years of excavation, number of wood samples collected, percentages of oak (Quercus) and ash (Fraxinus), and end dates of the tree-ring chronologies based on dendrochronology (Dendro), radiocarbon (14C) or radiocarbon wiggle-matching (Wiggle). 63 Les/Wood, Vol. 71, No. 1, June 2022 Čufar, K., Merela, M., Krže, L., & Velušček, A.: Dendrokronologija in absolutno datiranje kolišč na Ljubljanskem barju v evropski arheologiji in za katerega obstaja mre- ža dolgih referenčnih kronologij (npr., Baillie, 1995; Haneca et al., 2009; Tegel et al., 2022), ki v neka- terih primerih izkazujejo podobnost (telekonekci- jo), tudi če izvirajo iz oddaljenih regij (npr., Čufar & Martinelli, 2004; Čufar et al., 2008a, 2014; Kolář et al., 2012; Wazny et al., 2014). Za skupino kolišč iz sredine 4. tisočletja pr. Kr. (Strojanova voda, Hočevarica, Maharski prekop, Črešnja pri Bistri, Spodnje mostišče in starejši del najdišča Stare gmajne) smo sestavili hrastove kro- nologije, ki so se delno medsebojno prekrivale, tako da smo jih lahko združili v 442-let dolgo kro- nologijo BAR-3330 (slika 6). To kronologijo smo najprej datirali s pomočjo metode wiggle-matching Slika 6. Časovni razponi glavnih kronologij hrasta (QUSP), jesena (FRSP) in bukve (PI98- FAG) ter končni datumi koliščarskih naselbin (polna imena v preglednici 1). Kronologije, ki se končajo z letom 3330 pr. Kr. ali prej, so datirane z dendrokronološko telekonekcijo in so vključene v kronologijo BAR-3330 (3840-3330 pr. Kr.). Kronologije SG-QU-young, VO-QUSP1 in ZAL-QUSP1 temeljijo na radiokarbonskem datiranju, pod- prtim z metodo wiggle matching. Za ostale kronologije so končni datumi manj natančni in so večinoma ocenjeni na podlagi enega samega radiokarbonskega datuma. Figure 6. Time spans of the main chronologies of oak (QUSP), ash (FRSP), and beech (PI98- FAG) and end dates of pile dwellings (see Table 1 for complete names). Chronologies dated to 3330 BC or earlier are dat- ed by dendrochronology (teleconnection) and are included in the chronology BAR-3330 (time span 3840- 3330 BC). Chronologies SG-QU-young, VO-QUSP1, and ZAL-QUSP1 are dated by 14C and wiggle matching. For the others, end dates are estimated primarily on the basis of a single radiocarbon date. 64 Les/Wood, Vol. 71, No. 1, June 2022 Čufar, K., Merela, M., Krže, L., & Velušček, A.: Dendrochronology and absolute dating of pile-dwellings in Ljubljansko Barje z natačnostjo ± 10 let (zadnje leto 3332 ± 10 kal. pr. Kr.) (Čufar et al., 2010), v letih za tem, pa je sledilo dendrokronološko datiranje s pomočjo telekonek- cije z nemško-švicarsko kronologijo, tako da smo BAR-3330 določili časovni razpon 3771-3330 pr. Kr. (Čufar et al., 2015). Kronologija je v času objave temeljila na 106 sinhroniziranih serijah širin branik lesa iz šestih kolišč, po tem smo raziskali še kolišči Črnelnik in Trebež ter kronologijo podaljšali na 511 let (razpon 3840 – 3330 pr. Kr.) (slika 6). V tem prispevku (preglednica 1, sliki 6 in 7) za kolišča vedno navajamo zadnji datum kronologije, ki običajno sovpada z zaključkom poseka dreves in s tem gradbenih aktivnosti na kolišču, ki smo jih lahko ugotovili s pomočjo raziskanega lesa. Barje je bilo v različnih obdobjih različno intenzivno po- seljeno. V grobem lahko obstoj kolišč delimo v štiri časovne skupine (slika 7). Kronologije s končnimi datumi, mlajšimi od 3330 pr. Kr., so bile datirane samo z radiokar- bonskim ujemanjem (wiggle-matching), njihovo dendrokronološko datiranje še ni bilo uspešno. Takšni sta kronologiji Stare gmajne (mlajši del) in Veliki Otavnik Ib–njuna skupna kronologija SG-VO pokriva obdobje 3285-3108 ± 14 kal. pr. Kr. Za koliščarske naselbine iz 3. tisočletja pr. Kr. na Ljubljanskem barju smo sestavili predvsem je- senove (FRSP) kronologije (preglednica 1, slika 6), saj je bil hrast v tem času redko uporabljen. Edina daljša in dobro pokrita hrastova kronologija za ob- dobje 2659-2417 ± 18 kal. pr. Kr. je ZAL-QUSP1 iz Založnice. Slika 7. Ljubljansko barje in mesta raziskanih koliščarskih naselbin: (a) iz 5. tisočletja, (b) iz sredine 4. tisoč- letja, (c) iz konca 4. tisočletja ter (d) iz 3. tisočletja pr. Kr. Zemljevidi: Nina Škrk, GURS (2021). Figure 7. Map of Ljubljansko barje and the locations of the investigated pile dwellings: (a) from the 5th, (b) from the middle of the 4th, (c) from the end of the 4th, and (d) from the 3rd millennium BC. Maps: Nina Škrk, GURS (2021). 65 Les/Wood, Vol. 71, No. 1, June 2022 Čufar, K., Merela, M., Krže, L., & Velušček, A.: Dendrokronologija in absolutno datiranje kolišč na Ljubljanskem barju Ob začetku raziskav je bilo datiranje jesenovih kronologij malo verjetno, danes pa bi sodobne ra- diokarbonske metode omogočile njihovo datiranje (Capano et al., 2020), vendar ta možnost še ni bila izkoriščena. Dendrokronološko datiranje jesenovih kronologij s hrastovimi referencami s severa Alp ni verjetno, obstaja pa možnost njihovega datiranja s pomočjo hrastovih kronologij iz istega območja (heterokonekcija). Jesenove kronologije so večino- ma kratke (slika 6), njihovo variiranje širin branik pa odraža odziv na lokalne razmere in motnje, kot je obvejevanje dreves za prehrano živali. Datacije vseh jesenovih kronologij na Ljubljanskem barju bi zato morali izboljšati. To bi pripomoglo k boljšemu poznavanju poselitev kolišč Dušanovo, Parte in Za- ložnica, ki označujejo konec bakrene dobe na Lju- bljanskem barju (Velušček & Čufar, 2003; Velušček et al., 2011). Med mlajša kolišča uvrščamo tudi ko- lišče Špica, kjer smo pridobili kar 2452 vzorcev, a doslej nismo mogli sestaviti kakovostnih kronologij in podati prepričljivega datiranja lesa. Prikazani končni datumi kronologij označujejo zadnji (datirani) posek na posameznem kolišču oz. najdišču (preglednica 1, sliki 6 in 7), sicer smo na podlagi datumov sečnje posameznih dreves na ve- čini kolišč lahko določili eno ali več gradbenih faz. Na gradbene dejavnosti in popravila bivališč je bilo mogoče sklepati na podlagi velikega števila dreves, posekanih v istem letu ali v ozkem obdobju nekaj let. Nekatere koliščarske naselbine so bile poselje- ne več desetletij, medtem ko so druge delovale le 20 let ali manj (npr. Velušček, 2005). Raziskana koliščarska naselja se (z izjemo naj- dišča Špica) nahajajo na južnem delu Ljubljanskega barja in tvorijo dve skupini, ki sta med seboj od- daljeni 10-15 km (slika 7). Skoraj v vseh preučeva- nih obdobjih smo lahko zaznali sočasne gradbene dejavnosti na več koliščih, na primer Strojanova voda–Hočevarica, Spodnje mostišče–Stare gmajne (starejši del) in Parte – Založnica–Dušanovo. V na- selbinah, kjer je bila sočasnost dokazana z dendro- kronologijo, to potrjujejo tudi skoraj identične ar- heološke najdbe, kot je na primer keramika, orodje in orožje. V obdobju, 4600 do 2400 pr. Kr., ko so se na Ljubljanskem barju pojavljale koliščarske naselbine, je bila poselitev večkrat prekinjena. Prekinitve smo zabeležili med približno 4600 in 3700 pr. Kr., med 3300 in 3150 pr . Kr ., ter po letu 3100 pr . Kr . Razlogov za to še ne znamo v celoti pojasniti, verjetno so bile prekinitve poselitve posledica gospodarskih in pod- nebnih dejavnikov (Velušček, 2004b). Dendrokronološke ugotovitve se dopolnjujejo z ugotovitvami o materialni kulturi, kjer je bilo na podlagi keramike mogoče razmejiti več kulturnih horizontov oziroma poselitvenih obdobij. 4 ZAKLJUČKI 4 CONCLUSIONS Arheološka izkopavanja in raziskave lesa iz ko- liščarskih naselbin so omogočila datiranje kolišč. Na leto natančno smo lahko ugotovili gradbene dejavnosti (posek lesa) in ocenili trajanje naselitev. Umestitev v čas je omogočila vpogled o domnev- nem stanju okolja in gozdnih virov. Izbor in raba lesa nam povesta veliko tudi o življenju, razmišlja- nju in tehničnem znanju koliščarjev in njihovi rabi okolja (Tolar et al., 2011; Out et al., 2020). Izbira, obdelava in raba lesa so pokazali, da so imeli ko- liščarji bogato znanje o lesnih vrstah in lastnostih lesa. Znali so na najboljši možni način izbrati, obde- lati in uporabiti les iz neposredne okolice naselij ali iz bolj oddaljenih gozdov (Tolar et al., 2011). V drugi polovici 4. tisočletja pr. Kr. so si koliščarji znali izde- lati voz, katerega ohranjeni leseni ostanki z najdišča Stare gmajne predstavljajo najstarejše znano kolo z osjo na svetu, ki je mojstrovina prazgodovinske obrti (Velušček et al., 2009). Poleg znanja o lesu so za to potrebovali tudi znanje o materialih, saj so si iz razpoložljivih virov (kamen, les, roženina, baker) morali sami izdelati orodje in ga vzdrževati. Raziskave lesa so bile le manjši, a bistveni del multidisciplinarnih raziskav, ki so omogočile rekon- struirati celostno sliko človekovega življenja, okolja in povezav z drugimi najdišči. V zadnjih 27 letih razi- skav smo preučevali najdišča iz različnih obdobij in z različnimi kulturnimi ozadji. Analize peloda in mak- robotaničnih ostankov so pokazale, da so bili naj- zgodnejši prebivalci kolišč lovci, ribiči in nabiralci, tudi poljedelci in kmetje, ki so vzrejali domače živali (npr. Andrič et al. 2008; Tolar et al. 2011; Toškan et al. 2020). Obdobje koliščarskih naselbin je povezano z začetki lokalne metalurgije, ki so jo naše raziskave postavile v prvo polovico 4. tisočletja pr. Kr., upora- bo arzenovega bakra v 4. tisočletje, antimonovega bakra v začetek 3. tisočletja pr. Kr. (Trampuž-Orel 66 Les/Wood, Vol. 71, No. 1, June 2022 Čufar, K., Merela, M., Krže, L., & Velušček, A.: Dendrochronology and absolute dating of pile-dwellings in Ljubljansko Barje & Heath, 2008). Raziskovanje pasjega koprolita je omogočilo tudi vpogled v vlogo človekovega prve- ga živalskega spremljevalca v skupnosti (Tolar et al., 2021; Velušček et al., 2020). Za prikaz oziroma razumevanje prazgodo- vinskega vsakdanjega življenja na Ljubljanskem bar- ju je bila pomembna tudi rekonstrukcija tlorisa hiš v koliščarski naselbini Parte-Iščica, ki je potrdila, da je na koliščih stalo več manjših hiš s pretežno usmerit- vijo od JZ proti JV (Velušček et al., 2000). Tematika raziskav arheološkega lesa je obja- vljena tudi v video posnetkih, filmih in intervjujih, dostopnih na spletu. Predstavljeno je, kako je arhe- ološki les občutljiv, če ga izpostavimo zraku (Drying characteristics, 2014a, b), širša tematika najstarej- šega kolesa (Skrivnost barjanskega kolesa, 2015) in druga vprašanja v zvezi z lesom koliščarskih nasle- bin (Podobe znanja 2016, 2021; Vrhunci slovenske znanosti, 2020). 5 POVZETEK 5 SUMMARY Ljubljansko barje is the only area with pre- served archaeological remains of prehistoric pile-dwellings that has been discovered in Slovenia. In 2011, two groups of pile dwellings from the sur- roundings of the village of Ig were inscribed to the list of “Prehistoric Pile Dwellings around the Alps” on the UNESCO World Heritage List (Figure 1). We present some results of wood research from the excavations held between 1995 and 2021 and coordinated by the Institute of Archaeology, Scientific Research Centre of the Slovenian Acade- my of Science and Arts (IA ZRC SAZU). In this cam- paign particular attention was paid to the collec- tion of archaeological wood and the introduction of dendrochronology, which had to be newly de- veloped in this area (Figures 2, 3, 4). The interdis- ciplinary approach also included the development of palynology, archaeobotany and archaeozoology, and collaboration with numerous partners from other fields such as archaeometry, textile engineer- ing, etc. (e.g., Velušček 2004a, 2009). We performed 29 field studies on 16 sites of prehistoric pile dwellings (Table 1). At each of the sites we collected samples of all woody elements, and then conducted wood analysis. The most com- mon species were ash (Fraxinus excelsior), oak (Quercus robur and Quercus petraea), alder (Al- nus glutinosa), maple (Acer sp.), willow (Salix sp.), poplar (Populus sp.), hazel (Corylus avellana), horn- beam (Carpinus betulus), beech (Fagus sylvatica), silver fir (Abies alba), and elm (Ulmus sp.) (Figure 5a, b). Samples of oak, ash, and beech that con- tained more than 45 tree-rings were selected for dendrochronological analyses (Čufar & Velušček, 2012; Čufar et al., 2013; Velušček & Čufar, 2014). For each sample and site, the tree-ring series were cross-dated and assembled into floating chronol- ogies (Figure 4, 6). For their dating, we collected representative samples for radiocarbon and wig- gle-matching analyses (e.g. Čufar et al., 2010), and to teleconnect them with the existing references of the remote sites. Oak (Quercus sp.) chronologies from the 4th millennium BC could be assembled to form a 442- year long chronology BAR-3330; its time span of 3771-3330 BC was defined with dendrochronologi- cal teleconnection (Čufar et al., 2015). The chronol- ogy was later extended and is currently 511 years long (time span 3840 – 3330 BC). Other chronol- ogies with end dates younger than 3330 BC were dated using radiocarbon wiggle matching. These are Stare gmajne young and Veliki Otavnik Ib – their combined chronology SG-VO spans the period 3285-3108 ± 14 cal BC. In the pile dwellings of the 3rd millennium BC in Ljubljansko barje, ash chronologies predominat- ed. Their dating is currently mainly based on one radiocarbon date with lower accuracy and their dendrochronological dating is not very likely. While there exists a possibility to precisely date them by using modern radiocarbon methods supported by dendrochronology, this has not yet been fully at- tempted. The only longer and well replicated oak chronology of the 3rd millennium BC is the one from Založnica, ZAL-QUSP1, which spans the period 2659-2417 ± 18 cal BC. The sites of Založnica with Parte and Dušanovo mark the end of the Copper Age at Ljubljansko bar- je (Velušček & Čufar, 2003; Velušček et al., 2011). The presented end dates of the chronologies denote the last (dated) felling activity on the sites (Table 1, Figures 6, 7). Based on the felling dates of trees, we were also able to determine construc- tion phases at the dwellings. Building activities or 67 Les/Wood, Vol. 71, No. 1, June 2022 Čufar, K., Merela, M., Krže, L., & Velušček, A.: Dendrokronologija in absolutno datiranje kolišč na Ljubljanskem barju repairs could be inferred from a large number of trees felled in the same year or within a narrow pe- riod of a few years. Some pile-dwelling settlements were occupied for several decades or even longer, while others existed only 20 years or less (Velušček, 2005). The pile-dwellings from the Ljubljansko barje that were studied using dendrochronology existed in a time frame between ca. 4600 and 2400 BC. Dur- ing this long period, the occupation of the Ljubljan- sko barje basin also showed several interruptions, the exact reasons for which remain unknown. The dendrochronological findings complement each other with the findings on material culture, which helped to propose several cultural horizons delineated on the basis of the pottery. The introduction of dendrochronology helped to define the time of existence of these cultures, which was a significant achievement for Slovenian prehistoric archaeology. It is now possible to com- pare absolute dates with all kinds of archaeological finds. Dendrochronology also helped to obtain re- liable dates for specific finds, like the oldest pre- served wooden wheel with axle in the world, from the Stare gmajne site, aged around 5,150 years (Ve- lušček et al., 2009). The use of dendrochronology in the study of pile dwellings in Slovenia provides us with a num- ber of new opportunities to think about various topics, such as prehistoric woodland management, which has been studied by analysing the age and diameter of roundwood from the pile-dwelling site of Stare gmajne (Out et al., 2020). Among oth- er things, this work points to new possible future directions in the study of Ljubljansko barje as an archive of natural and anthropogenic history and human-environment interactions. ZAHVALA ACKNOWLEDGEMENTS Raziskave je financirala Javna agencija za razi- skovalno dejavnost Republike Slovenije, programa P4-0015 in P6-0064. Zahvaljujemo se sodelavkam in sodelavcem ter študentom in študentkam Od- delka za lesarstvo Biotehniške fakultete Univerze v Ljubljani ter Inštituta za arheologijo ZRC SAZU za izjemno pomoč na terenu, v laboratorijih in v vseh fazah raziskav. 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Copper finds from the Ljubljan- sko barje (Ljubljana Moor): a contribution to the study of pre- historic metallurgy. Arheološki vestnik, 59, 17-29. 69 Les/Wood, Vol. 71, No. 1, June 2022 Čufar, K., Merela, M., Krže, L., & Velušček, A.: Dendrokronologija in absolutno datiranje kolišč na Ljubljanskem barju Unesco, prehistoric pile dwellings around the Alps (2022). URL: https://whc.unesco.org/en/list/1363/ (20.5.2022) Velušček, A., Čufar, K., & Levanič, T. (2000). Parte-Iščica, archaeologi- cal and dendrochronological investigations. Arheološki vestnik, 51, 83-107. Velušček, A., & Čufar, K. (2003). Založnica near Kamnik pod Krimom on the Ljubljansko barje (Ljubljana Moor): a settlement of the Somogyvár-Vinkovci Culture. Arheološki vestnik, 54, 123-158. Velušček, A. (ur). (2004a). Hočevarica: eneolitsko kolišče na Ljubljan- skem barju = Hočevarica:an eneolithic pile dwelling in the Ljubljansko barje. (Opera Instituti archaeologici Sloveniae, 8). 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URL: https://www.rtvslo.si/rtv365/ar- hiv/174736192?s=tv (20.5.2022) 70 Les/Wood, Vol. 71, No. 1, June 2022 71 Les/Wood, Vol. 71, No. 1, June 2022 DR. JURE ŽIGON JE PREJEL JESENKOVO NAGRADO BIOTEHNIŠKE FAKULTETE UL ZA NAJBOLJŠEGA DIPLOMANTA DOKTORSKEGA ŠTUDIJA 3. STOPNJE 2021 DR. JURE ŽIGON RECEIVED THE JESENKO AWARD OF THE BIOTECHNICAL FACULTY UL FOR THE BEST PHD GRADUATE IN 2021 Sebastian Dahle 1* , Marko Petrič 1 . Izvleček / Abstract Izvleček: Jesenkove nagrade Biotehniške fakultete UL so najvišja priznanja za pedagoške, raziskovalne in strokovne dosežke ter za gospodarski in splošni družbeni napredek na področju biotehniških ved v Sloveniji. Biotehniška fakulteta jih podeljuje že vse od leta 1973, med njimi tudi Jesenkovo nagrado za najboljšega diplomanta doktorskega študija. Za leto 2021 je to nagrado na slovesnosti v marcu 2022 prejel asist. dr. Jure Žigon, ki je na Oddelku za lesarstvo BF zaposlen kot samostojni strokovni delavec. Ključne besede: Jesenkova nagrada, najboljši diplomant doktorskega študija, Biotehniška fakulteta, Univerza v Ljubljani Vol. 71, No. 1, 71-76 DOI: https://doi.org/10.26614/les-wood.2022.v71n01a07 1 Univerza v Ljubljani, Biotehniška fakulteta, Oddelek za lesarstvo, Jamnikarjeva 101, 1000 Ljubljana, SLO * e-pošta: sebastian.dahle@bf.uni-lj.si Slika 1. Dekanja Biotehniške fakultete prof. dr. Nataša Poklar Ulrih je nagrajencu dr. Juretu Žigonu podelila Jesenkovo nagrado za najboljšega diplomanta doktorskega študija. Figure 1. The Dean of the Biotechnical Faculty, Prof. Dr. Nataša Poklar Ulrih, presented the Jesenko Award for the best PhD graduate to Dr. Jure Žigon. 72 Les/Wood, Vol. 71, No. 1, June 2022 Dahle, S., & Petrič, M.: Dr. Jure Žigon received the Jesenko Award of the Biotechnical Faculty UL for the best PhD graduate in 2021 Abstract: The Jesenko Awards of the Biotechnical Faculty, University of Ljubljana, are the highest awards for pedagogical, research and professional achievements and for economic and general social progress in the biotechnical field in Slovenia. The Biotechnical Faculty has been giving these awards since 1973, including the Jesenko Award for the best doctoral studies graduate. For 2021 the recipient of this award was Assist. Dr. Jure Žigon, who received it at a celebration in March 2022. Dr. Žigon is employed at the Department of Wood Science and Technology at the Biotechnical Faculty as an independent professional associate. Keywords: Jesenko Award, the best graduate of doctoral studies, Biotechnical faculty, University of Ljubljana Jesenkove nagrade predstavljajo najvišja pri- znanja Biotehniške fakultete za pedagoške, razi- skovalne in strokovne dosežke ter za gospodarski in splošno družbeni napredek na področju bioteh- niških ved v Sloveniji. Jesenkovo nagrado, ustanov- ljeno leta 1973, podeli Biotehniška fakulteta vsako leto do trem posameznikom, in sicer za življenjsko delo, za najboljšega diplomanta doktorskega študija ter za najboljšega diplomanta magistrskega študija. Podelitev nagrade za najboljšega diplomanta dok- torskega študija v letu 2021 letošnjemu prejemniku dr. Juretu Žigonu je prikazana na sliki 1. Prejemnik se je rodil v Ljubljani, kjer je obi- skoval osnovno šolo in nato Srednjo lesarsko šolo, preden je začel s študijem lesarstva na Biotehniški fakulteti Univerze v Ljubljani. Le-tega je končal leta 2012 (BSc.) in 2014 (MSc.). Osnovno področje znanstvenega delovanja dr. Jureta Žigona je lesarstvo, s svojimi raziskavami pa deluje tudi na drugih povezanih področjih, tako znotraj Univerze v Ljubljani in tudi izven nje. Njego- ve objave vključujejo raziskave premazov za les, nji- hove oprijemnosti, vremenske vplive na obdelane površine, lepljenje lesa in drugih materialov, modi- fikacijo lesa z organskimi in anorganskimi pripravki, utekočinjanje lesa, odpornost proti glivam, lesne mikrostrukture, 3D tisk in celo oprijem bakterij na lignocelulozne podlage. Nagrajenec je doktoriral z izjemno bibliografijo, ki vsebuje 31 izvirnih znanstvenih objav, 1 pregled- ni znanstveni članek, 1 patentno prijavo ter vrsto drugih objavljenih del in znanstvenih uspehov. Od teh predstavlja 13 objav neposredni del njegove doktorske disertacije. Na področju lesarstva je kljub svoji mladosti že mednarodno priznan, tako s svo- jimi objavami, kot tudi zaradi gostovanj na drugih institucijah v okviru mednarodnih znanstvenih iz- menjav. Raziskovalno delo je izven dela na matični instituciji opravljal na šestih znanstvenih inštituci- jah v štirih evropskih državah (sliki 2 in 3). Tema doktorata Jureta Žigona je bila osredo- točena na tehnologijo, ki smo jo na Oddelku za Slika 2. Jure Žigon med udeleženci mednarodne šole inovacij Sprungbrett, 2016. Figure 2. Jure Žigon among the participants of the international Innovation School Sprungbrett, 2016. 73 Les/Wood, Vol. 71, No. 1, June 2022 Dahle, S., & Petrič, M.: Dr. Jure Žigon je prejel Jesenkovo nagrado Biotehniške fakultete UL za najboljšega diplomanta doktorskega študija 3. stopnje 2021 lesarstvo uvedli nedavno, in sicer na izkoriščanje netermičnih plazemskih razelektritev. Skupaj z mentorjem doc. dr. Sebastianom Dahlejem je dr. Žigon razvil in izdelal plazemsko napravo z novim principom delovanja za obdelavo lesa, tako da na- prava uporablja lesene obdelovance kot elektrode s plavajočim potencialom. To novo vrsto plazme z dielektrično barierno razelektritvijo s plavajočo ele- ktrodo je uspešno uporabil za modifikacijo površin lesa, npr. za večjo hidrofilnost in združljivost s pre- mazi na vodni osnovi. Čeprav te spremembe niso trajne, je bilo ugotovljeno, da trajajo dovolj dolgo in so zato uporabne za različne aplikacije, vključno z obdelavo lesa z notranjimi in zunanjimi premazi ter izboljšano trdnostjo lepilnega spoja. Poleg znanstvenoraziskovalnega dela se dr. Ži- gon aktivno ukvarja z vsakodnevnimi dejavnostmi na Oddelku za lesarstvo. Njegove odgovornosti se- gajo od upravljanja analitske opreme, npr. vrstič- nega elektronskega mikroskopa, do dejavnosti testiranja za komercialne partnerje in najrazličnej- ših tehničnih opravil v laboratorijih in v delavnici Oddelka, vključno s praktičnimi mizarskimi spret- nostmi obdelave lesa in z načrtovanjem in izdelavo najrazličnejših lesenih izdelkov v okviru raziskoval- nih projektov ter pedagoškega dela. Poleg tega dr. Žigon sodeluje v dejavnostih odnosov z javnostjo, vključno z dogodki za dijake (slika 4), pri poučeva- nju eksperimentalnih predmetov in pri nadzoru di- plomskega dela študentov. Z vso svojo angažiranostjo, motivacijo in znan- stveno odličnostjo se je dr. Žigon izkazal kot po- memben del Katedre za lepljenje, lesne kompozite, obdelavo površin in konstruiranje (slika 5) ter se je Slika 3. Jure Žigon med kratkim znanstvenim obiskom (COST action FP1407) na Tehniški univerzi Clausthal v Nemčiji, leta 2017. Figure 3. Jure Žigon during a short-term scientific mission (COST action FP1407) at Clausthal University of Technology, Germany, 2017. 74 Les/Wood, Vol. 71, No. 1, June 2022 Dahle, S., & Petrič, M.: Dr. Jure Žigon received the Jesenko Award of the Biotechnical Faculty UL for the best PhD graduate in 2021 Slika 4. Dr. Žigon dijakom predstavlja laboratorij za obdelavo površin lesa. Figure 4. Dr. Žigon presents the wood surface treatment laboratory to pupils. Slika 5. Skupina laboratorija za obdelavo površin, od leve: doc. dr. Pavlič, doc. dr. Dahle, dr. Žigon, prof. dr. Petrič. Figure 5. Work group of the surface treatment laboratory, from left: Assist. Prof. Dr. Pavlič, Assist. Prof. Dr. Dahle, Dr. Žigon, Prof. Dr. Petrič. 75 Les/Wood, Vol. 71, No. 1, June 2022 Dahle, S., & Petrič, M.: Dr. Jure Žigon je prejel Jesenkovo nagrado Biotehniške fakultete UL za najboljšega diplomanta doktorskega študija 3. stopnje 2021 med Jesenkove nagrajence gotovo uvrstil zasluženo (slika 6). Vsi na Oddelku za lesarstvo smo ponosni, da imamo v svoji sredini takega sodelavca kot je dr. Žigon in veseli, da lahko z njim delimo čast Jesenko- ve nagrade (slika 7). The Jesenko Awards represent the Biotechni- cal Faculty’s highest recognitions for pedagogical, research and professional achievements, as well as for economic and general social progress in the field of biotechnical sciences in Slovenia. Established in 1973, the Biotechnical Faculty honours up to three individuals a year with the Jesenko Award for Life- time Achievement, for the Best Doctoral Graduate, and for the Best Master’s Degree. The presentation of the award for the best doctorate to this year’s recipient, Dr. Jure Žigon, is shown in Figure 1. Dr. Žigon was born in Ljubljana, where he at- tended primary school, followed by the wood- working high school, before he began his studies in Wood Science and Technology at the Biotechnical Faculty of the University of Ljubljana, which he fin- ished in 2012 (B.Sc.) and 2014 (M.Sc.). The primary area of Dr. Žigon’s investigations is the field of wood science and technology, although he is active in a variety of other scientific fields across the University of Ljubljana and beyond. His published research includes work on wood coat- ings, adhesion and weathering, bonding of wood and other materials, organic and inorganic surface modification of wood, liquefaction of wood, re- sistance against fungi, wood microstructures, 3D printing, and even adhesion of bacteria on various lignocellulosic substrates. Dr. Žigon finished his doctorate with an excep- tional bibliography, presenting 31 original scientific publications, one review article, one patent appli- Slika 6. Dekanja prof. dr. Nataša Poklar Ulrih s tremi letošnimi nagrajenci Jesenkovih nagrad: dr. Jure Žigon (levo), Anja Kos, prejemnica Jesenkove nagrade za najboljšo diplomantko magistrskega študija (desno ob dekanji) in prof. dr. Jurij Diaci, prejemnik Jesenkove nagrade za življenjsko delo (desno) Figure 6. The dean, Prof. Dr. Nataša Poklar Ulrih, with this year’s three recipients of the Jesenko Awards: Dr. Jure Žigon (left), Anja Kos, recipient of the Jesenko Award for the best graduate of MSc studies (on the right side of the dean) and Prof. Dr. Jurij Diaci, recipient of the lifetime achievement Jesenko Award. 76 Les/Wood, Vol. 71, No. 1, June 2022 Dahle, S., & Petrič, M.: Dr. Jure Žigon received the Jesenko Award of the Biotechnical Faculty UL for the best PhD graduate in 2021 cation and a number of other published works and scientific successes. Out of these, 13 publications are a direct part of the doctoral dissertation. In spite of his youth, he is already internationally rec- ognised in the field of wood science and technol- ogy, both through his published works as well as through international scientific exchanges, includ- ing work performed at six scientific institutions in four European countries (Figs. 2 & 3). Dr. Žigon’s doctorate focused on a technology that was only recently introduced at the Depart- ment of Wood Science and Technology – the utili- sation of non-thermal plasma discharges. Together with his mentor, Assist. Prof. Dr. Sebastian Dahle, Dr. Žigon developed and built a plasma device with novel operating principle for wood treatments, uti- lising the wooden work pieces like electrodes at a floating potential. This new floating-electrode die- lectric barrier discharge plasma successfully modi- fied wood surfaces for increased hydrophilicity and compatibility with water-based coatings. Although these modifications were not permanent, they were found to last for durations long enough to be useful for various applications, including wood fin- ishing with indoor and outdoor coatings as well as improved adhesive bonding. In addition to scientific research, Dr. Žigon is ac- tively engaged in the daily activities at the Depart- ment of Wood Science and Technology. His respon- sibilities range from operating analytical equipment like the department’s Scanning Electron Micro- scope, to testing activities for commercial partners and technical activities in the department’s labora- tories and workshop, including practical carpenter skills and the construction and building of various wooden products in the frame of research projects and for pedagogical purposes. Moreover, Dr. Žigon participates in public relations activities, including events for pupils (Fig. 4), in teaching experimental courses and in support of students‘ diploma work. Through all his engagement, motivation and scientific excellence, Dr. Žigon has proven an impor- tant part of the department’s Chair of Adhesives, Wood Composites, Surface Treatment and Con- struction (Fig. 5) and a worthy recipient among the Jesenko awardees (Fig. 6). Together with the de- partment, we are glad to have such a colleague as Dr. Žigon in our midst, and happy for and with him to have received this well-deserved honour (Fig. 7). INTERNETNI VIRI WEB SOURCES COBISS, Kooperativni online bibliografski sistem Osebna bibliografija Jure Žigon za obdobje 2012-2022. URL: http://splet02.izum.si/ cobiss/bibliography?code=37804 (5.4.2022) Nacionalni portal odprte znanosti, avtor Jure Žigon. URL: http://www. openscience.si/NaprednoIskanje.aspx?q=1:12:Jure+%C5%BDi- gon (18.3.2022) Svečana podelitev Jesenkovih nagrad in priznanj fakultete, Zbornič- na dvorana Univerze v Ljubljani [Video]. YouTube, Biotehni- ška fakulteta. URL: https://youtu.be/9gnMR4CTcPA?t=3993 (18.3.2022) RUL- Repozitorij Univeze v Ljubljani, avtor Jure Žigon. URL: https:// repozitorij.uni-lj.si/Iskanje.php?type=enostavno&lang=sl- v&niz=jure+%C5%BEigon&vir=dk (5.4.2022) Slika 7. Dr. Jure Žigon, prejemnik Jesenkove nagra- de za najboljšega diplomanta doktorskega študija 3. stopnje 2021. Figure 7. Dr. Jure Žigon, recipient of the Jesenko Award for the best doctoral studies graduate in 2021. 77 Les/Wood, Vol. 71, No. 1, June 2022 Les/Wood Novice/News Srečanje mikroskopistov Slovenije – nagrada za najboljši poster dr. Angeli Balzano Meeting of Microscopists of Slovenia – Best Poster Award to Dr. Angela Balzano Maks Merela V mesecu maju 2022 se je v Ankaranu v orga- nizaciji Slovenskega društva za mikroskopijo (SDM) odvilo 4. slovensko posvetovanje mikroskopistov. Cilji posveta so povezovanje mlajših in že uveljavlje- nih raziskovalcev in drugih uporabnikov mikroskop- skih tehnik s področij znanosti o življenju in o mate- rialih ter industrije, predstavitve novejših dosežkov s področja mikroskopije, povezovanje laboratorijev, raziskovalnih skupin in predstavnikov industrije ter njihovih mikroskopskih metodologij na vseh nivojih ločljivosti. Namen predstavitev je tudi pregled nad dostopnimi mikroskopskimi tehnikami v Sloveniji, z namenom izboljšanja izkoriščenosti opreme ter iz- menjave znanja in izkušenj med različnimi vejami mikroskopije. Srečanja se je udeležila tudi razisko- valna skupina Biotehniške fakultete–Oddelka za lesarstvo. Z vodilno avtorico dr. Angelo Balzano je ekipa prejela priznanje za najboljši poster. Dr. Bal- zano je predstavila nov protokol priprave vzorcev mokrega arheološkega lesa za analizo z vrstičnim elektronskim mikroskopom “Scanning Electron Mi- croscopy protocol for the characterization of wa- terlogged archaeological wood”. Plakat je dostopen na povezavi: https://znc.si/dogodki/ostali-dogodki/ 4-slovensko-posvetovanje-mikroskopistov. Iskrene čestitke za odlično pripravljen in pred- stavljen poster! The 4th Slovenian meeting of microscopists, organized by the Slovenian Society of Microscopy (SDM), was held in Ankaran in May. The aim of the meeting was to bring together young scientists and established researchers as well as other users of microscopy techniques in the fields of life sciences, material sciences and industry, presenting the lat- est advances in microscopy, connecting laborato- ries, research groups and industry representatives and their microscopy methods at all resolution lev- els. The meeting also aimed to provide an overview of the microscopy techniques available in Slovenia in order to improve the use of the equipment and to share knowledge and experience among the dif- ferent fields of microscopy. The meeting was also attended by the research group of the Biotechnical Faculty–Department of Wood Science and Tech- nology. The team received the award for the best poster presented by the leading author, Dr. Angela Balzano. The poster, titled “Scanning Electron Mi- croscopy protocol for the characterization of wa- terlogged archaeological wood”, presented a new protocol for preparing waterlogged archaeological wood for scanning electron microscopy. The poster is available at: https://znc.si/dogodki/ostali-dogod- ki/4-slovensko-posvetovanje-mikroskopistov. Congratulations to Dr. Angela Balzano for an excellently prepared and presented poster! Vir / Reference Balzano, A., Krže, L., Čufar, K., & Merela, M. (2022). Scanning Electron Microscopy protocol for the characterization of waterlogged archaeological wood. V: Belec, B. (ur.), et al. 4. slovensko po- svetovanje mikroskopistov: knjiga povzetkov: 12.-13. maj, An- karan. 1. izd. Ljubljana: Slovensko društvo za mikroskopijo, 53. ISBN 978-961-94264-2-5. Slika 1. Dr. Angela Balzano z nagrajenim plakatom na srečanju 4. slovensko posvetovanje mikrosko- pistov, Ankaran, 12. in 13. maj 2022. Figure 1. Dr. Angela Balzano with the award-win- ning poster at the 4th SLOVENIAN MEETING OF MI- CROSCOPISTS, Ankaran, May 12-13, 2022. 78 Les/Wood, Vol. 71, No. 1, June 2022 Les/Wood Novice/News Katedra za management in ekonomiko lesnih podjetij (Oddelek za lesarstvo Biotehniške fakultete) je prejela prestižno priznanje mednarodne asociacije WoodEMA The Chair of Management and Economics of Wood Companies (Department of Wood Science and Technology, Biotechnical Faculty) receives the prestigious award of the international association WoodEMA Leon Oblak Na 15. mednarodni znanstveni konferenci Wo- odEMA, ki je potekala od 7. do 10. junija v Trnavi na Slovaškem, je aktualni predsednik združenja prof. dr. Roman Dudik iz Prage Katedri za management in ekonomiko lesnih podjetij (Oddelek za lesarstvo Biotehniške fakultete) podelil prestižno priznanje mednarodne asociacije WoodEMA. Združenje za ekonomiko in management v pre- delavi lesa in pohištvu WoodEMA je mednarodna, nepolitična, neprofitna in odprta znanstvena asoci- acija. Cilj združenja je promocija znanosti in rezulta- tov znanstvenega in strokovnega dela svojih članov, medsebojno znanstveno sodelovanje ter podpora znanosti in strokovnemu razvoju na področju dela asociacije. Združenje WoodEMA je bilo ustanov- ljeno leta 2007, danes pa ima člane, ki delujejo na širokem spektru ekonomskih in managerskih področij v gozdarstvu, predelavi lesa in proizvodnji pohištva. Združenje ima skoraj 100 aktivnih članov na treh celinah, od ZDA do Indije in Malezije ter v Evropi od Španije do Rusije ter od Finske do Sever- ne Makedonije. Vsako leto združenje WoodEMA na svoji skup- ščini podeli “štipendijo Roy Damary” za mlajše raziskovalce, v skladu s svojim statutom pa lahko podeli tudi posebno priznanje asociacije uglednim članom ali instituciji, ki so pomembno prispevali k znanstvenemu in strokovnemu razvoju združenja. Letos je priznanje prejela Katedra za management in ekonomiko lesnih podjetij, kar je prvi primer v zgodovini asociacije, da je nagrado prejela katera od institucij. V obrazložitvi je bilo zapisanih veliko razlogov za podelitev tega priznanja. Vsi člani Katedre za management in ekonomiko lesnih podjetij so tes- no vpeti v delo asociacije in nosilci številnih funkcij. Prof. dr. Leon Oblak je bil prvi predsednik asocia- cije, kasneje član upravnega, trenutno pa je član nadzornega odbora. Doc. dr. Jože Kropivšek je bil eden od ustanoviteljev združenja in dolgoletni član upravnega odbora. Doc. dr. Matej Jošt je trenutno član upravnega odbora, naslednje leto pa bo prev- zel mesto predsednika asociacije. Anton Zupančič, ki je bil do leta 2018 član katedre, pa sedaj skrbi za urejanje spletne strani asociacije, ki je bila v celo- 79 Les/Wood, Vol. 71, No. 1, June 2022 Les/Wood Novice/News ti razvita v tej katedri. Katedra je tudi dvakrat zelo uspešno organizirala vsakoletno znanstveno kon- ferenco, in sicer leta 2011 v Kozini in leta 2021 v Kopru, ki je zaradi covid epidemije potekala v hibri- dnem načinu in je bila po dveletnem obdobju pan- demije prva konferenca, izvedena v živo na Univerzi v Ljubljani. Zaradi vseh zgoraj navedenih in številnih dru- gih razlogov, zaradi prizadevanj in predanega dela članov katedre v korist združenja, je mednarodno Združenje za ekonomiko in management v prede- lavi lesa in pohištvu Katedri za management in eko- nomiko lesnih podjetij podelilo priznanje asociacije WoodEMA za pomemben prispevek k razvoju zdru- ženja. At the 15th international scientific conference WoodEMA, held in Trnava (Slovakia) from June 7 to 10, 2022, the current president of the associa- tion, Prof. Dr. Roman Dudik from Prague, Chair of Management and Economics of Wood Companies (Department of Wood Science and Technology, Bi- otechnical Faculty), received the prestigious recog- nition of the international association WoodEMA. WoodEMA, the International Association for Economics and Management in Wood Processing and Furniture Manufacturing, is an international, non-political, non-profit and open scientific asso- ciation. The aim of the association is to promote science and the results of the scientific and profes- sional work of its members, mutual scientific co- operation and support of science and profession- al development in the association’s field of work. WoodEMA was founded in 2007 and today has members working in a wide range of economic and management fields in forestry, wood processing and furniture manufacturing. The association has nearly 100 active members on three continents, from the United States to India and Malaysia, and in Europe from Spain to Russia and from Finland to Northern Macedonia. Each year at its meeting WoodEMA awards a “Roy Damary Scholarship” to young scientists and, in accordance with its statutes, may give special recognitions to prominent members or institutions that have made significant contributions to the sci- entific and professional development of the associ- ation. This year, the Chair of Management and Eco- nomics of Wood Companies received the award, marking the first time in the association’s history that an institution has received this honour. Numerous reasons were cited in the rationale for giving the award. All members of the Chair of Management and Economics of Wood Companies are closely involved in the work of the association and hold many positions. Prof. Dr. Leon Oblak was the first president of the association, later a mem- ber of the Executive Board, and is currently a mem- ber of the Supervisory Board. Doc. Dr. Jože Kropiv- šek was one of the founders of the association and a long-time member of the Executive Board. Doc. Dr. Matej Jošt is currently a member of the Execu- tive Board, and he will assume the position of pres- ident of the association next year. Anton Zupančič, who was a member of the department until 2018, is now taking care of editing the association’s web- site, which was entirely developed in this depart- ment. The Chair of Management and Economics of Wood Companies has also organised the annual scientific conference twice, both times very suc- cessfully, in 2011 in Kozina and in 2021 in Koper, with the latter held in a hybrid mode due to the COVID epidemic, and after the two-year pandemic the first conference was held live and in person at the University of Ljubljana. For all these and many other reasons, due to the efforts and dedicated work of the members of the Chair of Management and Economics of Wood Companies, the International Association for Eco- nomics and Management in Wood Processing and Furniture Industry has recognised the Chair of Management and Economics of Wood Enterprises for its important contributions to the development of the association itself. 80 Les/Wood, Vol. 71, No. 1, June 2022 Les/Wood Novice/News Gozdno-lesna veriga in podnebne spremembe: prehod v krožno biogospodarstvo Nov raziskovalni program, ki povezuje tri raziskovalne organizacije. Davor Kržišnik in Jožica Gričar Cilj novega raziskovalnega programa je identifi- kacija trenutnih izzivov znotraj gozdno-lesne verige vrednosti (od stoječih dreves do končnih izdelkov) in iskanje optimalnih rešitev na podlagi znanja in razpoložljivih virov treh raziskovalnih organizacij: Gozdarskega inštituta Slovenije, Univerze v Ljublja- ni, Biotehniške fakultete in Zavoda za gradbeništvo Slovenije. Raziskovalci teh treh organizacij prvič oblikujemo raziskovalno skupino z namenom za- gotavljanja medsektorskega (gozdarstvo, lesarstvo, gradnja z lesom) in inovativnega pristopa za dose- ganje zastavljenih ciljev ter povezovanje skupine z industrijo. Rezultati raziskovalnega programa se bodo kot inovativne rešitve prenesli tudi v prakso. S podporo trajnostnemu gospodarjenju, celovitemu varovanju gozdnih virov in biotske raznovrstnosti ter z uva- janjem okolju prijaznih, družbeno sprejemljivih in ekonomsko upravičenih izdelkov in delovnih proce- sov na osnovi lesa se bo povečal prispevek gozdno- lesne verige k nacionalnemu gospodarstvu. Na področju 4.01 (gozdarstvo, lesarstvo in papirništvo) v okviru vede biotehnika je s 1. janu- arjem 2022 začel delovati raziskovalni program P4-0430 Gozdno-lesna veriga in podnebne spre- membe: prehod v krožno biogospodarstvo. Javna agencija za raziskovalno dejavnost Republike Slove- nije (ARRS) bo raziskovalni program P4-0430 finan- cirala za obdobje šestih let v letnem obsegu 4250 raziskovalnih ur cenovne kategorije A letno. Program je organiziran v pet delovnih sklopov (DS): DS1: sodobno gojenje gozdov za višjo kakovost gozdnih proizvodov, DS2: lastnosti lesa in izboljšani materiali na osnovi lesa, DS3: učinkovita raba lesa v gradbeništvu, DS4: gozdno-lesni sektor v biogospo- darstvu ter DS5: projektno vodenje in diseminaci- ja. Teme, ki jih naslavljamo v novem programu, so slabo raziskane, vendar imajo velik aplikativni po- tencial. Zastavljeni cilji zahtevajo sodelovanje več institucij v smislu zagotovitve potrebnih kompetenc in raziskovalnih zmogljivosti. Vsak delovni sklop ses- tavljajo raziskovalci vseh treh raziskovalnih organi- zacij, da bi zagotovili izmenjavo znanja in razisko- valnih idej med raziskovalci z različnim ozadjem. Takšno ustvarjalno okolje je osnova za raziskovanje širokih interdisciplinarnih raziskovalnih vprašanj in uporabo novih tehnik v gozdno-lesni vrednostni verigi. Interdisciplinarni pristop ter nacionalno in mednarodno sodelovanje bo eden temeljnih kam- nov novega raziskovalnega programa. 81 Les/Wood, Vol. 71, No. 1, June 2022 Les/Wood Novice/News Klub alumnov lesarstva v letu 2022 Alumni Club Wood Science and Technology in 2022 Katarina Čufar, Boštjan Lesar Klub alumnov lesarstva, ki deluje kot sekcija v okviru kluba alumnov Univerze v Ljubljani Biotehni- ške fakultete in Društva lesarjev Slovenije, nadalju- je aktivnosti, ki jih je zavrla pandemija COVID, ko se alumni niso mogli zbirati in srečevati. Na Oddelku za lesarstvo smo v maju 2022 or- ganizirali akcijo seznanjanja študentk in študentov s klubom alumnov. Posvetili smo se spodbujanju vpisa v klub, kamor smo posebej povabili študentke in študente zaključnih 3. letnikov prvostopenjskega univerzitetnega študija lesarstva in visokošolskega študija Lesarsko inženirstvo, ki bodo polnopravni člani kluba lahko postali po diplomi. Še enkrat smo nagovorili študentke in študente 1. in 2. letnika ma- gistrskega študija lesarstva, v kolikor se še niso vpi- sali v klub po diplomi prve stopnje. Za zaključek akcije smo jih 12. 5. 2022 povabili tudi na skupno malico, ki smo jo priredili sredi de- lovnega četrtka v lepem vremenu pred Oddelkom za lesarstvo ob podpori tutork in tutorjev, mentoric in mentorjev letnikov in ostalih zaposlenih na od- delku. Malico je sponzoriralo Društvo lesarjev Slo- venije, predsednik Tomaž Kušar in tajnik Jure Žigon pa sta bila skupaj z avtorjema tega prispevka med glavnimi organizatorji dogodka, ki ima veliko pod- poro vodstva in zaposlenih na Oddelku za lesarstvo, ki so kot vedno z veseljem priskočili na pomoč. Inte- res študentk in študentov je bil velik. V juniju so Oddelek za lesarstvo obiskale alum- ne in alumni, ki so študij zaključili pred 40 leti. To je generacija, ki se je na univerzitetni študij lesarstva vpisala leta 1977 / 1978 in ga večinoma zaključila 1982. Organizator Janko Kebler je zbral imena in naslove 27 sošolcev in sošolk, od tega se jih je 19 udeležilo srečanja. V petek 10.6.2022 so se najprej zbrali na Oddelku za lesarstvo. Za mnoge je bil to prvi obisk fakultete po diplomi, ob čemer je treba poudariti, da so študij zaključili še v prostorih na Večni poti 2, v stavbi Gozdarskega inštituta Sloveni- je. Na Oddelku za lesarstvo jih je sprejel prodekan Marko Petrič, predstavitev Oddelka je pripravila Ka- tarina Čufar, laboratorije pa so jim razkazali Marko Petrič, Miran Merhar, Eli Keržič, Luka Krže in Angela Balzano ob podpori Urške Kovačič in ostalih zapo- slenih. »Alumni 40« so bili nad obiskom navdušeni. Obisk fakultete po tako dolgem času se jim je zdel zanimiv in nepozaben. Hvaležni so bili za gostolju- bje zaposlenih in se veselili, koliko novega in zani- mivega se dogaja na fakulteti, ki uživa velik medna- rodni ugled. »Alumni 40« so družabni del srečanja nadaljevali pri Čadu, mi pa smo veseli, da so uradni del lahko izpeljali skupaj z nami. Delo kluba alumnov Univerze v Ljubljani, ka- mor spada naša sekcija, je posebej vidno preko de- lovanja platforme https://alumniul.online, ki ima že več kot 11.000 članic in članov. Klub ponuja številne 82 Les/Wood, Vol. 71, No. 1, June 2022 Les/Wood Novice/News ugodnosti. Alumni lesarstva na platformi še nismo množično prijavljeni, na srečo pa smo povezani preko Društva lesarjev Slovenije in preko Facebook skupine Alumni klub Oddelka za lesarstvo. The Alumni Club of the Department of Wood Science and Technology, which functions as a sec- tion of the Alumni Club of the University of Ljublja- na, Biotechnical Faculty, and the Association of the 83 Les/Wood, Vol. 71, No. 1, June 2022 Les/Wood Novice/News Mednarodna delavnica »Manj znane lesne vrste v dendrokronologiji in kulturni dediščini« International workshop »Less known wood species in dendrochronology and cultural heritage« Maks Merela, Angela Balzano Od 14. do 16. junija 2022 je bila na Oddelku za lesarstvo Biotehniške fakultete Univerze v Lju- bljani organizirana mednarodna delavnica v okviru projekta Interdisciplinary, collaborative learning and teaching for resilient wood resources and innovations in a digital world (WooD+; 2020-1-CZ- 01-KA203-078483). Delavnica je pokrivala tema- tiko dendrokronologije manj znanih lesnih vrst na primeru dreves in elementov kulturne dediščine, tematiko različnih načinov vzorčenja in pripra- ve vzorcev, meritve in analize, različne pristope dendrokronologije ter moderne izzive v dendrokro- nologiji. Udeležence z Univerze Mendel Brno in Uni- verze za naravne vire in vede o življenju na Dunaju (BOKU) smo povabili k delavnici s pestrim progra- mom, ki ga je v uvodu predstavil izr. prof. dr. Maks Merela. Program je vseboval predavanja, delo na terenu, praktične vaje in družabne dogodke. Od- delek za lesarstvo je udeležencem predstavil prof. dr. Milan Šernek, razvoj dendrokronologije v Slove- niji pa je v uvodnem predavanju predstavila prof. Slovenian Wood Technologists, continues the activ- ities that were put on hold by the COVID pandem- ic, when alumni were unable to get together and meet in person. In May 2022, the Department of Wood Science and Technology organised a campaign to introduce the Alumni Club to students. The campaign was concluded with a joint brunch on May 12, 2022, in beautiful weather in front of the department. The event was supported by tutors, students, teachers, and the entire staff of the department. The brunch was sponsored by the Association of the Slovenian Wood Technologists. On June 10, 2022, a group of alumni who grad- uated 40 years ago visited the Department of Wood Science and Technology. This is the generation that started studying wood science and technology in 1977/78 and mainly graduated in 1982. For many of them, it was their first visit to the department since graduation. The “Alumni 40” were welcomed by Vice-Dean Marko Petrič. They visited the labora- tories, which were presented by the staff of the fac- ulty. The “Alumni 40” were enthusiastic and found the visit interesting and memorable. We are glad that they continued the tradition of celebrating graduation anniversaries within the Alumni Club. 84 Les/Wood, Vol. 71, No. 1, June 2022 Les/Wood Novice/News dr. Katarina Čufar. Doktorska študentka Nina Škrk in dr. Angela Balzano sta s kratkimi predstavitva- mi predstavili bazo podatkov in spletno platformo “SloClim”, ki vsebuje dnevne podatke o padavinah in temperaturah v visoki ločljivosti na mreži 1 x 1 km za celotno Slovenijo in je pomemben za dendrokro- nologijo in proučevanje podnebnih sprememb ter izzive na področju dendrokronologije pri sredozem- skih in tropskih vrstah. Terenske dejavnosti v okviru delavnice so vklju- čevale odvzem vzorcev za dendrokronološke prei- skave tako iz živih dreves v gozdnem sestoju, kot tudi iz objektov kulturne dediščine (lesene zgrad- be). Prikazani so bili različni načini priprave vzorcev ter različna merilna in analitična orodja, ki se upo- rabljajo v dendrokronologiji. Prikazana je bila tudi priprava vzorcev arheološkega lesa in izzivi, pove- zani z datiranjem (C14 in metode wiggle matching). Poleg dejavnosti delavnice so bili za boljše povezo- vanje udeležencev organizirani družabni dogodki, ki so vključevali tudi »brain storming«, razprave na prostem in ogled Ljubljane z rečno ladjo, kjer nam je na pomoč priskočil naš alumen Anže Logar in fir- ma Lakercraft. Intenzivna delavnica z delom v manj- ših skupinah se je izkazala za zelo uspešno tudi za izmenjavo izkušenj in predstavlja dobro osnovo za nadaljnje sodelovanje med vsemi udeleženci. As part of the project “Interdisciplinary, collab- orative learning and teaching for resilient wood re- sources and innovations in a digital world” (WooD+; 2020-1-CZ01-KA203-078483), the workshop “LKWS in dendrochronology & cultural heritage” was held at the Department of Wood Science and Technol- ogy, Biotechnical Faculty, University of Ljubljana from June 14 to 16, 2022. The workshop covered topics related to the dendrochronology of Less Known Wood Species (LKWS) and wood from cultural heritage. The pro- gram included sampling, new methods and tech- niques, measurements and data analysis, different tools and current challenges in dendrochronology. The participants from Mendel University Brno and the University of Natural Resources and Life Sciences, Vienna (BOKU) were welcomed to join the workshop with a program presented by Assoc. Prof. Maks Merela. The program included lectures, field sampling, practical exercises and social events. Prof. Dr. Milan Šernek presented the department, while Prof. Dr. Katarina Čufar gave an introductory lecture on the development of dendrochronology in Slovenia. PhD student Nina Škrk and Dr. Ange- la Balzano gave short presentations on “SloClim”, a high-resolution daily gridded precipitation and temperature dataset for Slovenia useful for com- bining dendrochronology and climatic conditions, and the challenges of applying dendrochronology to Mediterranean and tropical species. Field activities included coring for dendro- chronological purposes from both living trees in a forest stand and cultural heritage objects (wooden buildings). Various sample preparation methods were shown, and the measurement and analysis tools used in dendrochronology were demonstrat- ed. Sample preparation of archaeological wood and the challenges associated with dating (includ- ing C14 and wiggle matching methods) were also demonstrated. In addition to the workshop activ- ities, social events such as outdoor brainstorming discussions and a Ljubljana city tour by boat sup- ported by our alumni Anže Logar and Lakercraft were organised to better connect participants. The intensive small group workshop proved to be very successful with regard to sharing experiences, and we hope for further fruitful collaboration among all participants.