21 Les/Wood, Vol. 69, No. 2, December 2020 WOOD IDENTIFICATION OF CHARCOAL WITH CONFOCAL LASER SCANNING MICROSCOPY IDENTIFIKACIJA LESA OGLJA S POMOČJO KONFOKALNE LASERSKE VRSTIČNE MIKROSKOPIJE Ang ela Balz ano 1* , K a t arina Čuf ar 1 , Luk a K rž e 1 , Mak s Mer ela 1 UDK 630*811:62-663.8 Original scien tific article / Iz virni znans tv eni članek R eceiv ed / Prispelo : 5. 10. 2020 Accep t ed / Spr eje t o: 4. 11. 2020 V ol. 69, No. 2, 21-35 DOI: h ttp s://doi.or g /10.26614/les-w ood.2020. v69n02a02 Abstract / Izvleček Abstract: Wood identification of barbecue charcoal from commercial packages of three retailers (B1, B2, B3) in Slove- nia and Croatia was performed with help of Confocal Laser Scanning Microscopy (CLSM). CLSM enabled us to image key identification features of charcoal wood that were compared with light micrographs of wood from the reference collection. Product B1 contained charcoal made exclusively of beech wood (F agus s ylv a tic a) and the declaration indi- cated the address of the producer, in Serbia which allowed traceability of the wood. The selection of wood species in product B2, consisted of red oak (Quer cus cerris or Q. rubr a), black locust (R obinia p seudoac acia), and cherry (Prunus a vium), which could originate from Serbia, and it did not contain tropical wood as stated on the package. Product B3 contained wood from at least four (sub)topical species which could not be exactly identified to species/genus level. The declaration on the product did not allow traceability of wood. As the risks of illegal logging are high for wood of (sub)tropical origin, our results support the initiative that the monitoring of the charcoal trade should be covered by the EUTR - European Timber Regulations. Keywords: charcoal, confocal laser scanning microscopy (CLSM), wood anatomy, wood identification, domestic wood species, tropical wood species, illegal logging Izvleček: Identifikacijo lesa oglja iz treh trgovin v Sloveniji in na Hrvaškem smo opravili s pomočjo konfokalne laserske vrstične mikroskopije (CLSM). Predstavili smo slike in opise ključnih znakov za identifikacijo lesa oglja in lesa iz refe- renčne zbirke. Izdelek B1 je vseboval oglje iz lesa bukve (F agus s ylv a tic a) in deklaracijo z natančnim naslovom proizva- jalca iz Srbije, ki omogoča sledenje izvora lesa. Izdelek B2 je vseboval oglje iz lesa enega od rdečih hrastov (Q. cerris ali Q. rubr a), robinije (R obinia p seudoac acia) in češnje (Prunus a vium). To potrjuje, da pošiljka ne vsebuje tropskega lesa, kot je navedeno na deklaraciji in da verjetno prihaja iz Srbije. Izdelek B3 je vseboval les iz vsaj štirih (sub)tropskih lesnih vrst, ki jih ni bilo mogoče natančno določiti. Ker so tropske vrste za oglje pogosto nezakonito posekane, se prid- ružujemo pobudi, da bi v Evropi nadzor trgovine z ogljem morali vključiti v Uredbo EU o lesu - EUTR. Ključne besede: oglje, konfokalna laserska vrstična mikroskopija (CLSM), anatomija lesa, identifikacija lesa, domače lesne vrste, tropske lesne vrste, nezakonita sečnja 1 INTRODUCTION 1 UVOD Char c oal is mainly used as a solid fuel f or hea t - ing. It is made thr ough the pr ocess of c arbonisa - tion, wher e w ood is burned in a lo w o xy g en en vi- r onmen t and v ola tile c omponen ts ar e r emo v ed thr ough p yr oly sis. The lo w er the per cen t ag e of v ol - a tile c omponen ts in the char c oal is, the higher its 1 Univ er sity of Lju bljana, Biot echni c al F aculty , Departmen t of W ood Science and T echnology , Ljubljana, Slo v enia * e-mail: ang ela.balz ano@b f .uni-lj.si Angela Balzano, Orcid ID: https://orcid.org /0000-0002-6494-5850 K atarina Čuf ar , Or cid ID: https:// or cid.or g /0000-0002-7403-3994 Maks Mer ela, Or cid ID: https:// or cid.or g /0000-0001-7927-2049 quality bec ause in this w a y char c oal burns cleaner , with little or no smok e (Oy edun e t al., 2012). W ood char c oal as a sour ce of ener gy has pla y ed an im- port an t r ole in human his t or y . In palaeobot an y it is ther e f or e an import an t macr obot anic al r emain pr o viding in f orma tion on the pas t en vir onmen t, plan t c ommunities, and e xploit a tion of r esour ces (Chabal, 1994; Asouti & Aus tin, 2005). In ar chae- ology it pr o vid es in f orma tion r ela t ed t o the use of w oo d b y pas t socie ties, in domes tic and ritual c on t e x ts (Scheel- Ybert e t al., 2010) and indic a t or s of hum an mob ility in the landsc ape (B yrne e t al., 2013). Char c oal fr om ar chaeologic al sit es (Begin & Mar guerie, 2002) and in na tur al soils is s tudied t o 22 Les/Wood, Vol. 69, No. 2, December 2020 Balz ano , A., Čuf ar , K., K rž e, L., & Mer ela, M.: Iden tifik acija lesa oglja s pomočjo k onf ok alne laser sk e vr s tične mikr osk opije under s t and the ec onomics of the fuel, which de- scribes the r ela tionship be tw een humans and the f or es t (Mar guerie & Hunot, 2006). A clear e x ample ar e the s tudie s c onduct ed in P ompei, wher e the char c oal analy sis w as particularly f ocused t o fir e - w ood (Coubr a y , 2013; V eal, 2014). In Eu r ope, especially lar g e amoun ts of char c oal w er e used in pr e-indus trial times, be f or e it w as r e - placed b y the massiv e use of c oal and other sour c- es of ener gy . Fr om the w orldwide per spectiv e it s till r emains a crucial sour ce of ener gy in man y r egions. Acc or ding t o the F ood and Agricultur e Or g aniz a- tion of the Unit ed Na tions (F A O), half the w ood e x - tr act ed fr om f or es ts w orldwide is used t o pr oduce ener gy and about 17% is c on v ert ed in t o char c oal (F A O 2017; Haag e t al., 2020; Z emk e e t al., 2020). In Eur ope, char c oal is curr en tly mainly used f or barbe- ques, and Ger man y has the big g es t c onsump tion, with o v er 230 .000 t ons in 2018. Slo v enia is cur - r en tly not among the big pr oducer s or c onsumer s of char c oal, bu t in ancien t times gr ea t amoun ts of beech w ood char c oal w er e pr oduced and used in me t allur gy (Brus & Jarni, 2012; Cimper šek, 2012). Char c oal is oft en sold withou t tr aceability and the c ou n tr y of origin is not indic a t ed. As its tr ade is not y e t c o v e r ed b y the Eur opean Timber R egula- tions, EUTR, (EU) No. 995/201 0, it is suspect ed tha t c onsider able amoun ts of ille g ally cut timber fr om all ar ound the w orld ma y be sold in f orm of char - c oal. Th e r ecen t s tudy of Haag e t al. (2017; 2020) e x amined se v er al Eur opean c oun tries and sho w ed tha t char c oal on the mark e t, especially pr oducts without F SC or PEF C certific a t es (Hansen e t al., 1997), oft en c on t ains timber fr om sub tr opic al or tr opic al origin, and the declar a tions on the pack ag- ing w er e oft en inc orr ect and/ or inc omple t e, as also c on firmed b y the German c onsumer associa tion (Stiftung W ar en t es t, 2019). Char c oal fr om illeg al log ging c on tribut es t o f or es t degr ada tion, de f or - es t a tion, desertific a tion and soil er osion. During char c oal pr oduction high t emper a tur es and c arbonisa tion modif y the s tructur e of w ood (Leme e t al., 2007; Z emk e e t al., 2020). Despit e this, char c oal ma y pr eser v e crucial ana t omic al f ea tur es f or w ood iden tific a tion, especially in c ase of w ell- kno wn species with clear dia gnos tic f ea tur es (Prior & Alvin, 1983, 1986; Prior & Gasson, 1993; K w on e t al., 2009; Leme e t al., 2010; Gonç alv es e t al., 2012; Hubau e t al., 2013; Haag e t al., 2020; Z emk e e t al., 2020). Ho w e v er , g ood kno wledg e of w ood ana t om y c ombined with r e f er ence c oll ections and da t abases is needed f or the t a x onomic iden tific a tion of char - c oal w ood. As r eport ed in the lit er a tur e, the anal - y sis and iden tific a tion of char c oal based on w ood ana t om y ar e widely applied (e. g. Scheel- Ybert, 2000; Thér y -P arisot e t al., 2010; Dott e-Sar out e t al., 201 5; Andrič e t al., 2016). When w ood ana t om- ic al f ea tur es ar e not sufficien tly pr eser v ed, char c oal c ollections ar e especially imp ort an t sour ce of r e f er - ence ma t erial t o impr o v e iden tific a tion (Z emk e e t al., 2020). The iden tific a tion of char c oal w ood based on ana t omic al char act eris tics is thus an import an t w a y t o tr ack its origin and pr e v en t illeg al log ging and black mark e t sales. This c an be of gr ea t import ance f or ec os y s t em c onser v a tion and c an mak e an e ff ec - tiv e c on tribution not only t o the en vir onmen t but also socioec on omics, b y incr e asing the sus t ainabil - ity of the char c oal pr oduction chain (Gonç alv es & Scheel- Ybert, 2012). Although char c oal iden tific a tion is r ela tiv ely f easible f or t emper a t e and bor eal w ood species, the iden tific a tion of tr opic al and sub tr opic al spe- cies is mor e c omplic a t ed due t o the gr ea t biodiv er - sity and number of t a x a (Haag e t al., 2020). Iden tific a tion of ana t omic al tr aits in char c oal is g ener ally made on fr agmen ts not big g er than a f e w cen time tr es (Moser e t al., 2018). R e flect ed ligh t micr osc op y is oft en used t o the t a x on. The char - c oals ar e class ic ally iden tified based on ana t omi - c al f ea tur es ob ser v ed under the r e flect ed ligh t on pr epar ed surf aces (i.e., tr ans v er se, r adial, t ang en- tial). T o ob t ain thin sections f or ob ser v a tion under the tr ansmitt ed ligh t, time-c onsuming embedding me thods and adv anced equip men t such as sledg e-, r ot a tion- or cr y o-micr ot ome ar e needed (Lude - mann & Nelle, 2002; Di P asquale, 2009; Sch w e- ingruber , 2012 ; Beeckman e t al., 2020). Sc anning electr on micr osc op y with adequa t e sample pr epa- r a tion is also used t o visualise de t ailed ana t omi - c al tr aits (e. g., Bout ain e t al., 2010; Hubau e t al., 2013). R ecen tly , modern me thods lik e 3D-r e flect ed ligh t micr osc op y (Z emk e e t al., 2020) and Con f oc al Laser Sc anning Micr osc op y (CLSM) (Balz ano e t al., 2019; Čufar a t al., 2019) ha v e pr o v ed t o be use ful f or ob t aining thr ee-dimensional in f orma tion on the ana t omic al s tructur e of w ood, allo wing species iden tific a tion. 23 Les/Wood, Vol. 69, No. 2, December 2020 Balz ano , A ., Čuf ar , K., K rž e, L., & Mer ela, M.: W ood iden tific a tion of char c oal with Con f oc al Laser Sc anning Micr osc op y The main adv an t ag e of CLSM is the possibility t o dir ectly ob ser v e the surf ace of in t er es t without time-c onsuming sample pr epar a tion, and a t the same time, thank s t o the 3D imag e acquisition, t o ob t ain an adequa t ely high r esolution t o r ec ognise w ood ana t omic al f ea tur es. A r e cen t s tudy of the quality of barbeque char - c oal (St ar e & Prislan, 2020) sho w ed tha t 10 out of 11 pr od ucts on the Slo v enian mark e t did not mee t the s t andar d f or char c oal quality SIS T EN 1860-2 (2005). Ho w e v er , St ar e and Prislan (2020) do not r eport on w ood iden tific a tion. In this article, w e c ollect ed and analy sed barbe- que char c oal sold b y thr ee r e t ailer s in Slo v enia and Cr oa tia. W e used CLSM t o iden tif y the char c oal w ood and show the pot en tial of the me thod f or iden ti- fic a tion on fr actur e plains without specific sample pr epar a tion. Furthermor e, w e aimed t o iden tif y which w ood species c an be f ound in select ed bar - beque char c oal pr oducts, if the w ood is of Eur opean origin or also import ed fr om (sub)t opic al ar eas, and finally , if the selection of w ood species agr ees with the declar a tions on the c ommer cial pr oducts. 2 MATERIALS AND METHODS 2 MATERIAL IN METODE W e r andomly c ollect ed char c oal fr om thr ee c onsignmen ts fr om loc al r e t ailer s. W e inspect ed the c on t en t of thr ee bags, B1, B2 and B3, and their declar a tion lab els (T able 1). The fir s t pr oduct B1 w as bou gh t in a small shop f or g ar dening pr oducts in Cr oa tia, kno wn f or high quality pr oducts fr om trus tw orth y sour ces; the lab el r eport ed the c oun - tr y of origin and e x act addr ess of the pr oducer in Serbia. The bag B2 w as boug h t in a small shop f or chemic al pr od ucts in Slo v enia. Its label r eport ed the c ou n tr y of origin – Serbia, and declar ed tha t the pr oduct did not c on t ain tr opic al w ood. The thir d bag B3 w as bough t in a supermark e t in Slo - v enia, which belongs t o an in t erna tional disc oun t chain tha t oper a t es thousand s of s t or es acr oss Eu - r ope and the Unit ed St a t es. Its label only r eport ed tha t the char c oal w as made f or the giv en chain. W e check ed the c on t en t of each bag and mac- r osc opic ally pr e-iden tified w ood species with help of a magnific a tion lens and gr ouped the char c oal pieces which pr esumably belong ed t o the same species. Finally , lar g er samples, possibly c on t aining ma tur e w ood of the s t em (a v oiding twigs and juv e- nile w ood), w er e select ed f or de t ailed inspection. The samples w er e split with a cutt er , t o ob t ain sub-samples of typic al w ood ana t omic al surf aces (tr ans v er se, t ang en tial and r adial) (Scheel- Ybert, 2004). The sub -samples of the same char c oal piece w er e labelled. The samples w er e put in a pe tri dish with t a- ble salt , and placed on the s t ag e of the Con f oc al Laser Sc anning Micr osc ope (CLSM) Olympus LEXT OLS5000 (Olympus Corpor a tion T oky o 163-0914, Japan) (Figur e 1) t o ob ser v e ana t omic al f ea tur es with the f ollo wing objectiv es: MPLFLN5x (nu - meric al apertur e 0.15, w ork ing dis t ance 20 mm), MPLFLN10xLEXT (numeric al apertur e 0.3, w orking dis t ance 10.4 mm), and LMPLFLN20XLEXT (numer - ic al apertur e 0.45, w orking dis t ance 6.5mm). B y mo ving the s t ag e in r eal-time, w e fir s t used the op - tic al s y s t em t o g e t a panor amic o v er vie w t o inspect the en tir e surf ace. Then, onc e w e de t ect ed the k e y iden tific a tion f ea tur es, high r esolution laser c on - f oc al imag es w er e acquir ed a t diff er en t f ocus po - sitions using the s tit ching fun ction. Measur emen ts of the ana t omic al tr aits w er e perf ormed with the OLS5000 imag e analy sis softw ar e. W ood iden tific a tion w as perf ormed with the a v ailable iden tific a tion k e y s and w ood ana t omic al lit er a tur e, dichot omous micr osc opic k e y s and il- lus tr a t ed descriptions of the species (e. g., Gr osser , 1977; Sch w eingruber , 1978, 1990; W ag en führ , 1996, 1999; Schoch e t al., 2004; Čufar & Zupančič, 2009; Signorini e t al., 2014). W ood iden tific a tion softw ar e such as DEL T A/ INTKEY f or micr osc opic and macr o- sc opic iden tific a tion of c ommer cial har dw oods and CITE S species (Rich t er & T r ock enbr odt, 1995; Rich t er & Dallwitz, 2000; Rich t er e t al., 2002, 2005), or pr o- gr ammes a v ailable online such as InsideW ood (IA W A c ommitt ee, 1989; InsideW ood, 2004 on w ar ds; Wheeler , 2011), and an a tlas and macr osc opic w ood iden tific a tion softw ar e pack ag e f or It alian timber species ( Ruffina tt o e t al., 2017, 2019; Ruffina t o & Criv ellar o , 2019) w er e used. W ood samples and ana- t omic al sections of the c ollection of the Departmen t of W ood Science and T echnology w er e used as a r e f er ence ma t erial. R e f er ence slides w er e ob ser v ed with a Nik on E clip se E 800 ligh t micr osc ope, and the micr ogr aphs w er e t ak en with a Nik on DS- fi1 digit al c amer a and NIS Elemen ts Br 3.0 softw ar e. 24 Les/Wood, Vol. 69, No. 2, December 2020 Balz ano , A., Čuf ar , K., K rž e, L., & Mer ela, M.: Iden tifik acija lesa oglja s pomočjo k onf ok alne laser sk e vr s tične mikr osk opije 3 RESULTS AND DISCUSSION 3 REZULTATI IN RAZPRAVA CLSM enabled us t o ob ser v e the main w ood ana t omic al f ea tur es f or pr ecise iden tific a tion of the char c oal samples. Sample pr epar a tion only t ook f e w minut es t o split the char c oal and g e t an ori- en t ed fr actur e plain. It w as the mos t challenging t o ob t ain a clear cr oss-section. The 3D s y s t em of the micr osc ope all o w ed us t o c ap tur e high r esolution and sharp imag es, e v en if the surf aces of the sam- ples w er e not c omple t ely fla t. In this w a y w e c ould find k e y f ea tur es f or the iden tific a tion of domes tic species fr om t emper a t e Eur ope. W e r ec or ded also f our (sub)tr opic al t a x a wher e e x act w ood iden tifi- c a tion t o the le v el of species or g enus w as not pos - sible (T able 1). Figure 1. Charcoal observation: (A) Confocal Laser Scanning Microscope (CLSM) Olympus LEXT OLS5000 (Olympus Corporation Tokyo 163-0914, Japan), and (B) a detailed view of charcoal sample in a petri dish with table salt placed on the stage, under the objective of 20x magnification. Slika 1. Opazovanje oglja: (A) konfokalni laserski vrstični mikroskop (CLSM) Olympus LEXT OLS5000 (Olym- pus Corporation Tokyo 163-0914, Japonska) in (B) vzorec oglja v petrijevki s kuhinjsko soljo, na mizici mikroskopa pod objektivom 20-kratne povečave (podroben pogled). Consignment / Pošiljka Declaration label / Navedba na embalaži Taxon / Takson B1 small shop f or g ar dening pr oducts, Cr oa tia / manjša tr g o vina z a vrtne potr eb ščine, Hr v ašk a pr oduce d in Serbia, pr oduce r ’ s addr ess kno wn / pr oiz v e deno v Srbiji, naslo v pr oiz v ajalc a znan Fagus sylvatica B2 small shop f or cle aning pr oducts, Slo v enia / manjša tr g o vina s čis tili, Slo v enija dis tribut er ’ s addr e ss in Slo v e nia kno wn, made in Se rbia, no tr opic al w ood / dis tribut erje v naslo v v Slo v eniji znan, nar eje no v Srbiji, ni tr op ski les Prunus avium Quercus sp. Robinia pseudoacacia B3 supe rmark e t of an in t erna tional disc oun t chain, Slo v e nia / v eleblag o vnic a mednar odne disk on tne v e rig e , Slo v e nija made f or the chain / pr oiz v e deno z a pr odajno v e rig o T1 (sub)tr opic al spe cie s / (sub)tr op sk a vr s t a T2 (sub)tr opic al spe cie s / (sub)tr op sk a vr s t a T3 (sub)tr opic al spe cie s / (sub)tr op sk a vr s t a T4 (sub)tr opic al spe cie s / (sub)tr op sk a vr s t a Table 1. Wood identification of the investigated barbecue charcoal Preglednica 1. Identifikacija lesnih vrst raziskanega oglja za žar 25 Les/Wood, Vol. 69, No. 2, December 2020 Balz ano , A ., Čuf ar , K., K rž e, L., & Mer ela, M.: W ood iden tific a tion of char c oal with Con f oc al Laser Sc anning Micr osc op y In the f ollo wing w e pr esen t the w ood ana t om y of the in v es tig a t ed char c oal as ob ser v ed with CLMS and imag es of the r e f er ence ma t erial fr om the c ol - lection ob ser v ed with a ligh t micr osc ope. 3.1 EUROPEAN BEECH, Fagus sylvatica, FAGACEAE 3.1 NAVADNA BUKEV, Fagus sylvatica, FAGACEAE The cr oss-section of the select ed sample c on- t ains dis tinct gr owth rings and gr owth ring boundar - ies demar c a t ed by thick er -w alled fibr es, r a y s of tw o dis tinct siz es, and lar g er r a y s nodded a t the gr owth ring boundaries. The dis tribution of v essels is dif - fuse-por ous t o semi-ring-por ous. A v er ag e t ang en tial v essel diame t er is up t o 80 µm. Axial par ench yma is apotr acheal, diffuse and diffuse-in-ag gr eg a t es (Fig- ur e 2 A , B). On the tangential section we can observe r a ys of two distinct siz es and vessels with simple perf or ation plates (Figur e 2 C, D). Small r a ys ar e mor e fr equent than the multiseriate ones (> 10 cells wide and com- monly >1000 µm high). The r adial section shows heter - ogenous r a ys (with body r a y cells pr ocumbent and one r ow of squar e mar ginal cells), and vessels with simple and scalarif orm perf or ation plates (Figur e 2 E, F). Figure 2. European beech F agus s ylv a tic a (A, C, E) wood from the collection of the Department of Wood Sci- ence and Technology, light microscopy and (B, D, F) charcoal, CLSM. (A, B) Cross-sections with diffuse-po- rous to semi-ring-porous distribution of vessels; (C, D) tangential section with rays of two sizes; (E, F) radial section with heterogenous rays (body ray cells procumbent with generally one row of square marginal cells) and vessels with simple perforation plates. Scale bars = 250 µm. Slika 2. Les navadne bukve F agus s ylv a tic a (A, C, E) iz zbirke Oddelka za lesarstvo; svetlobna mikroskopija in (B, D, F) oglje, tehnika CLSM. (A, B) prečna prereza, difuzen do polvenčast razpored trahej; (C, D) tangenci- alni prerez, dve velikosti trakov; (E, F) radialni prerez s heterogenimi trakovi (celice trakov ležeče, ob robu običajno ena vrsta kvadratnih robnih celic) in traheje z enostavnimi in lestvičastimi perforacijami. Merilne daljice = 250 µm. 26 Les/Wood, Vol. 69, No. 2, December 2020 Balz ano , A., Čuf ar , K., K rž e, L., & Mer ela, M.: Iden tifik acija lesa oglja s pomočjo k onf ok alne laser sk e vr s tične mikr osk opije 3.2 CHERRY , Prunus avium, ROSACEAE 3.2 ČEŠNJA, Prunus avium, ROSACEAE The char c oal sample pr esen ts a cr oss-section with dis tinct gr o wth ring boundaries and semi-ring- por ous v essel dis tribution. A v er ag e t ang en tial diam- e t er of early w ood v essels is up t o 70 µm. Fibr e cell w alls ar e of medium w all thickness. Axial par ench y - ma is ab sen t or e x tr emely r ar e (Figur e 3 A , B). On the t ang en tial section w e c an see mainly up t o 4-se- ria t e and 15-30 cells high r a y s (Figur e 3 C , D). The r a- dial section c on t ains v essels with simple perf or a tion pla t es and dis tinct spir al thick enings thr oughout the en tir e bodies of the v essel elemen ts. Ra y s ar e main- ly he t er og enous with squar e cells mainly r es trict ed t o one mar ginal r o w (Figur e 3 E, F). The described ana t om y and g ood agr eemen t with the r e f er ence ma t erial indic a t es tha t the w ood belongs t o cherr y (Prunus avium) fr om the f amily R osaceae. Figure 3. Cherry, Prunus a vium (A, C, E) wood from the collection of the Department of Wood Science and Technology, light microscopy and (B, D, F) charcoal, CLSM. (A, B) Cross-section of semi-ring-porous wood, vessels solitary or in small clusters; (C, D) tangential section with mainly 3-seriate rays; (E, F) radial sec- tions with heterogeneous rays containing one marginal row of square cells, vessels with simple perforation plates and distinct spiral thickenings. Scale bars = 250 µm. Slika 3. Les češ nje Prunus a vium (A, C, E) iz zbirke Oddelka za lesarstvo; svetlobna mikroskopija in (B, D, F) oglje, tehnika CLSM. (A, B) prečna prereza polvenčasto poroznega lesa, traheje posamezne ali v manjših skupinah; (C, D) tangencialni prerez s pretežno 3-rednimi trakovi; (E, F) radialni prerezi s heterogenimi tra- kovi, ki vsebujejo po eno robno vrsto kvadratastih celic, traheje z enostavnimi perforacijami in spiralnimi odebelitvami. Merilne daljice = 250 µm. 27 Les/Wood, Vol. 69, No. 2, December 2020 Balz ano , A ., Čuf ar , K., K rž e, L., & Mer ela, M.: W ood iden tific a tion of char c oal with Con f oc al Laser Sc anning Micr osc op y 3.3 RED OAK, Quercus sp., FAGACEAE 3.3 RDEČI HRAST, Quercus sp., FAGACEAE The sample is ring-por ous w ood, v essels ar e e x clusiv ely solit ar y and in la t e w ood arr ang ed in diag onal and/ or r adial pa tt ern. La t e w ood v essels ar e r ou nd and thick -w alled. E arly w ood v essels oc- c asionally c on t ains thin w alled tyloses. Gr ound tissue c onsis ts of v asicen tric tr acheids (ar ound the v essels) and librif orm fibr es of medium cell w all thickness. Axial par ench yma is pr edominan tly apo - tr acheal, diffus e and diffuse -in-ag gr eg a t es (Figur e 4 A , B). On the t ang en tial sec tion w e see homog e- nous r a y s of tw o dis tinct siz es. The y ar e uniseria t e and multiseria t e; the lar g e r a y s ar e >10 cells wide and > 1mm high (Figur e 3 C , D). V essels ha v e simple perf or a tions, r a y s ar e homog eneous (Figur e 3 C , D). The described f eatur es ar e typical f or r ed oaks, which ar e in our r egion (Slovenia and surr ounding countries) r epr esented by the native T urk ey oak (Q. cerris) or by artificially intr oduced American r ed oak (Q. rubra). The two r ed oaks can be distinguished fr om the white oaks in the r egion mainly r epr esented by the pedunculate (Q. robur) and sessile oak (Q. petraea) oak (Richter & Dallwitz, 2000; Mer ela & Čufar, 2013). Figure 4. Red oak, Turkey oak Quer cus cerris or American red oak Q. rubr a. (A, C, E) wood from the collection of the Department of Wood Science and Technology, light microscopy and (B, D, F) charcoal, CLSM. (A, B) cross-sections of ring porous wood with exclusively solitary vessels. In the latewood vessels are round, thick walled, and arranged in diagonal and/or radial pattern. Earlywood vessels contain few tyloses (B), ground tissue consists of tracheids (around the vessels) and fibres. Apotracheal axial parenchyma is diffuse and dif - fuse-in-aggregates; (C, D) tangential section with uniseriate to very large multiseriate rays; (E, F) radial sec- tion with homogeneous rays and vessels with simple perforation plates. Scale bars = 250 µm. Slika 4. Rdeči hrast, cer Quer cus cerris ali ameriški rdeči hrast Q. rubr a. (A, C, E) les iz zbirke Oddelka za lesarstvo; svetlobna mikroskopija in (B, D, F) oglje, tehnika CLSM. (A, B) prečna prereza venčasto poroznega lesa z izključno posameznimi trahejami. V kasnem lesu so traheje okrogle, debelostene in diagonalno in / ali radialno razporejene. Traheje ranega lesa vsebujejo malo til (B), osnovno tkivo je sestavljeno iz traheid (okoli trahej) in vlaken. Apotrahe - alni aksialni parenhim je difuzen in difuzen v agregatih; (C, D) tangencialni prerez z enorednimi in velikimi trakovi; (E, F) radialni prerez s homogenimi trakovi in traheje z enostavnimi perforacijami. Merilne daljice = 250 µm. 28 Les/Wood, Vol. 69, No. 2, December 2020 Balz ano , A., Čuf ar , K., K rž e, L., & Mer ela, M.: Iden tifik acija lesa oglja s pomočjo k onf ok alne laser sk e vr s tične mikr osk opije 3.4 BLACK LOCUST, Robinia pseudoacacia, FABACEAE 3.4 ROBINIJA, Robinia pseudoacacia, FABACEAE The w ood is ring-por ous with early - and espe- cially la t e w ood v essels arr ang ed in clus t er s. T yloses ar e particularly abundan t in early w ood v essels. Fi - br es ha v e medium thick cell w alls. Axial par ench y - ma is par a tr acheal, sc an ty , v asicen tric, and alif orm (Figur e 5 A , B , C). On the t ang en tial section w e c an ob ser v e 3- or 4-cell wide r a y s, a xial par ench yma and v essel elemen ts ar e s t oried (Figur e 5 D , E, F). On the r adial section w e c an see v essels with sim- ple perf or a tion pla t es filled with tyloses and ho - mog eneous r a y s (Figur e 5 G, H, I). These f ea tur es helped us t o iden tif y black locus t, Robinia pseudoa- cacia fr om the f amily F abaceae-F aboideae. Figure 5. Black locust, R obin ia p seudoac acia (A, D, G) wood from the collection of the Department of Wood Science of Technology, light microscopy and (B, C, E, F, H, I) charcoal, CLSM. (A, B, C) Cross-section with ring porous wood, vessels arranged in clusters, earlywood vessels contain tyloses, axial parenchyma paratracheal vasicentric and aliform; (D, E, F) tangential sections with 3 or 4 seriate rays and storied axial parenchyma (D); (G, H, I) radial sections, vessels with simple perforation plates filled with tyloses and ho- mogeneous rays. Scale bars = 250 µm. Slika 5. Les robinije, R obinia p seudoac acia (A, D, G) iz zbirke Oddelka za lesarstvo; svetlobna mikroskopija in (B, C, E, F, H, I) oglje, tehnika CLSM. (A, B, C) prečna prereza venčasto poroznega lesa, traheje razporejene v gnezdih, traheje ranega lesa močno otiljene, aksialni parenhim paratrahealen, vasicentričen in krilast; (D, E, F) tangencialni prerezi s 3 - 4-rednimi trakovi in etažnim aksialnim parenhimom (D); (G, H, I) radialni pre- rezi, traheje z enostavnimi perforacijami, zapolnjene s tilami, trakovi homogeni. Merilne daljice = 250 µm 29 Les/Wood, Vol. 69, No. 2, December 2020 Balz ano , A ., Čuf ar , K., K rž e, L., & Mer ela, M.: W ood iden tific a tion of char c oal with Con f oc al Laser Sc anning Micr osc op y 3.5 CHARCOAL MADE OF WOOD OF TROPICAL OR SUBTROPICAL WOOD ORIGIN 3.5 OGLJE IZ LESA TROPSKEGA ALI SUBTROPSKEGA IZVORA The B3 pack ag e of barbeque char c oal mainly c on t ained char c oal made of w ood species of (sub) tr opic al origin. W e c ould r ec ognise f our diff er en t t a x a (T1, T2, T3, T4) with se v e r al diagnos tic f ea tur es which do not appear in species of t emper a t e or bo - r eal f or e s ts. Ho w e v er , due t o the gr ea t number and ana t omic al v arie ty of sub tr op ic al or tr opic al species and lack of r e f er ence ma t erial, the ob ser v ed fr ag- men ts c ould not be assigned de finitiv ely t o either a sub tr opic al or tr opic al r egion. As e x act iden tific a- tion t o le v el of g enus or species w as not possible, and w e only pr esen t the w ood s tructur e of f our typic al samples (Figur es 6, 7). In T1 and T2 w e c ould obser v e all thr ee an- Figure 6. Diffuse porous species T1 and T2 of sub-tropical or tropical origin with diagnostically important anatomical features: (A) large vessels in radial multiples, axial parenchyma aliform, thick-walled fibres, (B) heterogenous ray with numerous crystals and vessels with simple perforations, (C) uniseriate rays, in- tervessel pits alternate to opposite, (D) large vessels, axial parenchyma aliform and banded, thick-walled fibres, (E) rays heterogenous, (F) rays and axial parenchyma storied. Scale bars = 250 µm. Slika 6. Difuzno porozni (sub)tropski vrsti T1 in T2 z diagnostično pomembnimi anatomskimi znaki: (A) veli- ke traheje v radialnih skupinah, aksialni parenhim krilast, vlakna z debelimi stenami, (B) heterogeni trak s številnimi romboidnimi kristali in stiloidi, traheje z enostavnimi perforacijami, (C) enoredni trakovi, interva- skularne piknje izmenične in nasprotne, (D) velike traheje, aksialni parenhim je krilast in v pasovih, vlakna z debelimi stenami, (E) heterogeni trakovi, (F) trakovi in aksialni parenhim v etažah. Merilne daljice = 250 µm 30 Les/Wood, Vol. 69, No. 2, December 2020 Balz ano , A., Čuf ar , K., K rž e, L., & Mer ela, M.: Iden tifik acija lesa oglja s pomočjo k onf ok alne laser sk e vr s tične mikr osk opije Figure 7. Species of sub-tropical or tropical origin T3 and T4 with diagnostically important anatomical fea- tures: (A) large vessels filled with tyloses, axial parenchyma aliform - lozenge, thick-walled fibres, (B) rays homogenous mainly 2 cells wide, vessels with simple perforations and intervessel pits alternate, (C) large vessels, axial parenchyma banded, bands more than 3 cells wide, fibres very thick walled, (D) rays mainly 2 or 3 cells wide. Scale bar= 250 µm. Slika 7. Difuzno porozni (sub)tropski vrsti T3 in T4 (sub)tropskega ali tropskega izvora z diagnostično po- membnimi anatomskimi znaki: (A) velike traheje zapolnjene s tilami, aksialni parenhim krilast – romboidne oblike, vlakna z debelimi stenami, (B) homogeni trakovi široki pretežno 2 celici, traheje z enostavnimi per- foracijami in intervaskularne piknje izmenične, (C) velike traheje, aksialni parenhim v pasovih, širokih več kot 3 celice, vlakna debelostena, (D) trakovi v glavnem šir oki 2-3 celice. Merilne daljice = 250 µm 31 Les/Wood, Vol. 69, No. 2, December 2020 Balz ano , A ., Čuf ar , K., K rž e, L., & Mer ela, M.: W ood iden tific a tion of char c oal with Con f oc al Laser Sc anning Micr osc op y a t omic al sections. T1 (Figur e 6 A , B , C) has lar g e v essels in r adial multiples, par a tr acheal alif orm a xial par ench yma, thick -w alled fibr es, he t er og e - nous r a y s with numer ous prisma tic and elong a t ed s tyloid cry s t als and v essels with simple perf or a- tions. Ra y s ar e uniseria t e, in t er v essel pits ar e al- t erna t e t o opposit e. T2 also has lar g e v essels, a xial par ench yma is par a tr acheal alif orm and banded, fibr es ar e thick w alled, r a y s ar e he t er og enous and 2 or 3 cells wide. Ra y s and a xial par ench yma ar e s t oried (Fig- ur e 6 D , E, F). Acc or ding t o the r ec ognised f ea tur es the w ood r esembles Dicorynia guianensis (An- g élique, basr alocus), F abaceae-Caesalpinioideae f amily with g eogr aphic al dis tribution in tr opic al South Americ a. On samples T3 and T4 w e c ould only obser v e tr ans v er se and t ang en tial surf aces. Both species ar e diffuse por ous with lar g e v essels and other f ea tur es indic a ting sub-tr opic al or tr opic al origin (Figur e 7). T3 has lar g e v essels filled with tyloses, a xial par ench yma alif orm - lo z eng e, thick -w alled fibr es, homog enous r a y s ar e mainly 2 cells wide, v essels ha v e simple perf or a tions and in t er v essel pits alt erna t e (Figur e 7 A , B). The s tructur e c an be described as Afzelia-lik e w ood type. Afzelia spp. (Af z elia, doussie), F abaceae-Ceasilpinoidae, fr om tr opic al Afric a. T4 has lar g e v essels and banded a xial par en- ch yma with bands mor e than 3 cells wide and thick - w alled fibr es (Figur e 7 C , D). Ra y s ar e mainly 2 or 3 cells wide. The w ood c ould be described as Lo- phira alata lik e type. Lophira alata (az obe, bong os- si), Ochnaceae, gr o w s in tr op ic al Afric a. Haag e t al. (2020) described w ood with similar v essel and a xial par ench yma char act eris tics as Milletia type w ood, ho w e v er in their c ase the w ood also had s t oried r a y s which w er e not f ound in our c ase. The a ttribution of f our har dw oods t o (sub) tr opic al origin is assumed on a c ombina tion of typic al w ood ana t omic al f ea tur es which do not ap- pear in t emper a t e or bor eal species (e. g., diffuse dis tribution of v ery lar g e v essels, no clear gr owth rings, no early - and la t e- w ood, abundan t par a tr a- cheal a xial par ench yma, s t oried s tructur es). Lack of f ea tur es lik e c olour , sapw ood/heartw ood dif - f er en tia tion, density , odour and pot en tial de f or - ma tion or loss of minut e s tructur es hamper mor e pr ecise iden tific a tion. 4 DISCUSSION AND CONCLUSIONS 4 RAZPRAVA IN ZAKLJUČKI As pr e viously demons tr a t ed, CLSM enables the r ec ognition of f ea tur es crucial f or w ood iden tific a- tion on v arious objects (Balz ano e t al., 2019; Čufar e t al., 2019), and this s tudy c on firms tha t the me th- od is also use ful f or iden tific a tion of char c oal w ood without special sample pr epar a tion. R eg ar ding the origin of w ood species and the issue of tr acea bility , our s tud y sho w s tha t the char - c oal fr om tw o r e t ailer s, pr od ucts B1 and B2, pr e- sumably origin a t ed in Serbia. Pr oduct B1 pr o v ed t o be e x clusiv ely made of beech w ood, as declar ed b y the label on the pack ag e, which also enabled tr ace - ability . Pr oduct B2 c on t ained r ed oak (Q. cerris or Q. rubra), blac k locus t (Robinia pseudoacacia ) and cherr y (Prunus avium). The species gr o w in Serbia and ar e not tr opic al, ther e f or e the s t a t emen t on the label “mad e in Serbia” and “no tr opic al w ood” c an be c on firmed. Ho w e v er , the declar a tion did not enable tr aceability of w ood sour ce. The declar a tion on pr oduct B3 fr om the big in t erna tional disc oun t supermark e t chain only r e - port ed tha t char c oal w as pr oduced f or the giv en chain. Ho w e v er , the c on t en t of a t leas t f our tr op - ic al species r e v ealed tha t w e w er e dealing with a pr oduct of the global mark e t, wher e the c oun tr y of w ood origin is not kno wn and the possibility of ille - g al log ging c annot be e x cluded. Char c oal is g ener ally c onsider ed of high qual - ity if it is dr y , solid, with pieces of unif orm siz e, does no t crumble e x cessiv e ly , emits hea t e v enly and bu rns (or smoulder s) with a small amoun t of smok e (St ar e & Prislan, 2020). The Eur opean s t an- dar d SIS T EN 1860-2: 2005 de fines pr ecise crit eria f or the quality of char c oal f or grilling and c on t ains fiv e k e y quality indic a t or s: (1) char c oal humidity (as lo w as poss ible or ≤ 8%), (2) quan tity of ash, (3) v ola tile c ompo und c on t en t (r ela t ed t o the amoun t of smok e,) (4) the amoun t of bound c arbon (pr o- portional t o the amoun t of hea t ener gy emitt ed per unit w eigh t of c oal and long er and cleaner c ombus - tion), and (5) the particle siz e of the char c oal. St ar e and Prislan (2020) t es t ed char c oal fr om 11 dis tribut er s in Slo v enia and f ound tha t only the Slo v enian pr oduct fr om the “ oglar sk a de ž ela” , or “ char c oal c oun tr y ” , had adequa t e quality . This pr oduct is pr obably c ompar able t o our B1 char c oal made of beech w ood. Our pr oduct B2 c on t ained a 32 Les/Wood, Vol. 69, No. 2, December 2020 lot of dus t, especially bec ause oak (due t o its w ood s tructur e) typic ally disin t egr a t ed in t o lamella lik e particles. Our B3 w as a lo w -price pr oduct fr om a big sup ermark e t chain; anot her pr oduct fr om the same chain tha t w as t es t ed f or char c oal quality w as f ound not t o mee t the s t andar d EN 1860-2 (2005) (St ar e & Prislan, 2020). The iden tific a tion of f our Eu r opean and f our (sub)tr opic al w ood species and inc omple t e in f or - ma tion on w oo d origin sho wn in this s tudy ar e in line with the si tua tion ob ser v ed in other Eur opean c oun tries. Ther e f or e, the g ener al public and pr o- f essionals should be notified tha t w ood fr om c om- mer cial pr oduc ts tha t is sold without pr oper dec- lar a tions c anno t be tr aced and ma y origina t e fr om illeg al lo g ging in dis t an t ar eas. As such, w e support the initi a tiv e tha t char c oal tr ading should be c on - tr olled and included in the c orr esponding anne x of the EU Timber R egula tion (EUTR). 5 SUMMARY 5 POVZETEK Z upor abo laser sk e k on f ok alne vr s tične mi- kr osk opije (Co n f oc al Laser Sc anning Micr osc op y – CLSM) smo r azisk ali lesno oglje z a ž ar . Pr e v erili smo upor abnos t me t ode z a pr epo zna v anje ana t omskih znak o v lesnih vr s t, iz k a t erih je oglje nar ejeno. Ž e- leli smo ug ot o viti, k a t er e lesne vr s t e v sebuje oglje v pr oda ji, če je les lok alneg a iz v or a ali uv o ž en in če iz vir a tudi iz g o z do v (sub)tr op sk eg a pasu. Z anima - lo nas je tudi, k ak šne poda tk e v sebujejo na v edbe (deklar acije) na pr oiz v odih. Pr e v erili smo pomen iden tifik acije lesa oglja z a ug ot a vljanje iz v or a lesa in ocenili, če je tudi v Slo v eniji mor da napr odaj oglje iz ileg alno posek aneg a tr op sk eg a lesa. Razisk ali smo 3 vr eče oglja iz tr eh tr g ovin. Pr vi iz- delek (B1) je bil k upljen v majhni tr g ovini z vrtnar skimi potr ebščinami na Hr v ašk em. Na embalaži je bil na v e- den t očen naslov pr oiz v ajalc a iz Srbije, k ar omog oč a sledljiv os t iz v or a lesa. Iz delek B2 smo k upili v manjši tr g ovini v Slov eniji. Na embalaži je bilo na v edeno , da iz delek ne vsebuje tr opsk eg a lesa in da je bil nar ejen v Srbiji. V r eč a B3 je bila k upljena v Slov eniji, v disk on tni tr g ovini v elik e mednar odne v erig e, ki upr a vlja tr g o- vine po E vr opi in ZD A. Napis na embalaži je na v ajal samo , da je iz delek nar ejen z a omenjeno v erig o. Oglje v sak e po same zne vr eče smo pr egledali pod lupo. Z a po dr obnejši pr egled smo izbr ali najpri - mernejše k ose, ki so po mo žnos ti v sebo v ali zr el (adult en) les debla in jih je bilo mog oče pripr a viti z a opaz o v anje z gr adbe lesa na v seh tr eh ana t om- skih r a vninah. Iz ogibali smo se lesu dr obnih v ej in juv enilnemu lesu. Izbr ane v z or ce smo r azlomili ali r az cepili z no ž em, da smo lahk o opaz o v ali pr ečno , r adialno in t ang encialno lomno po vr šino. Razlomljeno oglje smo pos t a vili v pe trije vk o s k uhinjsk o soljo in g a pr egledali s k on f ok alnim vr s tič- nim mikr osk opom (Con f oc al Laser Sc anning Mi- cr osc ope, CLSM) Olympus LEXT OLS5000 (Olympus Corpor a tion T oky o 163-0914, Japonsk a) z objek - tivi: MPLFLN5x (numerična odprtina 0,15, delo v - na r az dalja 20 mm), MPLFLN10xLEXT (numerična odprtina 0,3, delo vna r az dalj a 10,4 mm) in LMPL- FLN20XLEXT (numerična od prtina 0,45, delo vna r az dalja 6,5 mm) (slik a 1). S pr emik anjem mizice smo z op tičnim sis t emom najpr ej pridobili pano - r amsk o slik o z a pr egled celotne po vr šine. P oisk ali smo ključne lesnoana t omsk e iden tifik acijsk e znak e in s pomočjo funk cije ses t a vljanja slik z ajeli laser sk e k on f ok alne slik e visok e ločljiv os ti z v elik o globinsk o os trino. Meritv e dimenzij ana t omskih znak o v smo iz v edli s pr ogr amom z a analiz o slik e OLS5000. Iden tifik acijo lesa smo opr a vili s pomočjo r az- ličnih iden tifik acijskih ključe v in specialne lesno ana t omsk e lit er a tur e (npr . Gr osser , 1977; Sch w ein- gruber , 1978, 1990; W ag en füh r , 1996, 1999; Schoch e t al., 2004; Ču f ar & Zupančič , 2009; Signorini e t al., 2014). Z a mikr osk op sk o in makr osk op sk o iden tifik a- cijo lesa lis t a v ce v in lesnih vr s t s se znama CITE S smo upor abili pr ogr am DEL T A / IN TKEY (Rich t er & T r oc- k enbr odt, 1995 ; Rich t er & Dallwitz; Rich t er e t al., 2002, 2005) in sple tni r ačuna lniški ključ InsideW o- od (Insi deW oo d, 2004; Wheeler , 2011), ki t emelji na naboru mikr osk op skih znak o v z a iden tifik acijo lesa lis t a v ce v (IA W A c ommitt ee, 1989). V pomoč nam je bil tudi pr ogr amski pak e t z a makr osk op sk o iden tifik acijo lesa na it alijansk em tr gu (Ruffina tt o e t al., 2017, 2019) in a tlas z a makr osk op sk o iden tifi- k acijo lesa (Ruffina t o & Criv ellar o , 2019). K ot r e f e - r enčni ma t erial smo upor abi li les in mikr osk op sk e pr epar a t e iz zbirk e na Oddelk u z a lesar s tv o. R e f e- r enčne pr epar a t e smo opaz o v ali s s v e tlobnim mi- kr osk opom Nik on E clip se E 800, mikr of ot ogr a fije pa smo po sneli z digit alno k ame r o Nik on DS - fi1 in pr o- gr amom z a analiz o slik e NIS Elemen ts Br 3.0. Pr eds t a vljena š tudija je ena pr vih r azisk a v oglja z no v o mikr osk op sk o me t odo CLSM, ki se je izk az a- Balz ano , A., Čuf ar , K., K rž e, L., & Mer ela, M.: Iden tifik acija lesa oglja s pomočjo k onf ok alne laser sk e vr s tične mikr osk opije 33 Les/Wood, Vol. 69, No. 2, December 2020 la z a primerno , čepr a v se z gr adba lesa z ar adi viso - kih t em per a tur in k arboniz acije med iz dela v o oglja spr emeni. Domače vr s t e smo lahk o na t ančno iden - tificir ali, tudi z a t o , k er jih dobr o po znamo in imamo z anje na r azpolag o r e f er enčni ma t erial. V oglju so bile z as t opane tudi vr s t e, ki r as t ejo v sub tr op sk em in tr op sk em pasu. Oglje doba vit elja B1 je bilo nar ejeno iz lesa bukv e (Fagus sylvatica) (slik a 2, pr eglednic a 1). Pr odajalna na Hr v ašk em, kjer smo g a k upili, ž e le t a ponuja oglje is t eg a manjšeg a pr oiz v ajalc a iz Srbije, ki sl o vi po visoki k ak o v os ti. N a embalaži je bil na- t ančen naslo v pr oiz v ajalc a, k ar omog oč a sledljiv os t. Buk e v je tr adicionalna in najbolj cenjena vr s t a z a oglje v Slo v eniji in šir ši r egiji (Brus & Jarni, 2012; Cimper šek, 2012). V vr eči B2 smo iden tificir ali les eneg a od r de- čih hr as t o v , ce r a ali amerišk eg a r dečeg a hr as t a (Q. cerris ali Q. rubra), r obinije (Robinia pseudoacacia) in češnje (Prunus avium ). V se vr s t e, ki jih podr obno pr eds t a vljamo (slik e 3, 4, 5), uspe v ajo tudi v Srbiji, k ar je v skladu z napisom na embalaži „nar ejeno v Srbiji“ . N apis na embalaži tud i na v aja, da iz delek ne v sebuje tr op sk eg a lesa, k ar smo potr dili. Na emba- laži ni poda tk o v o pr oiz v ajalcu. V vr eči B3 iz tr g o vine v elik e mednar odne di- sk on tne v erig e je bilo oglje v saj š tirih tr op skih vr s t ne znaneg a iz v or a, na embalaži pa je bilo na v edeno samo , da je iz delek nar ejen z a omenjeno tr g o v sk o v erig o. Da gr e z a les (sub)tr op skih vr s t (slik a 6, 7) smo ug ot o vili na osno vi znak o v , ki jih naše domače vr s t e iz zmerno celinsk eg a ali hladneg a podnebneg a pasu nimajo. Pr eisk ane (sub)tr op sk e vr s t e so difuzno por o zni lis t a v ci z z elo v elikimi tr ahejami in obilnim par a tr ahealnim krilas tim ali tr ak as tim ak sialnim pa- r enhimom. Pri nobeni nismo z aznali jasno vidnih pri- r as tnih plas ti (br anik in le tnic) t er r aneg a ali k asneg a lesa. Dv e vr s ti s t a imeli ak sialne elemen t e r azpor e- jene v e t až ah. Ug ot o vljeni znaki niso z adošč ali, da bi na t ančno določili vr s t o , r od ali r egijo iz v or a, saj je na- bor (sub)tr op skih vr s t izr edno v elik, lesnoana t omsk e r azlik e med vr s t ami in r odo vi pa so pog os t o majhne. Pri iden tifik aciji smo pogr ešali znak e k ot so bar v a, r azlik a med belja v o in jedr o vino , v onj in g os t ot a, ki so se iz gubili pri pr edela vi lesa v oglje. Glede na na- v edeno smo lahk o samo na v edli znane tr op sk e vr s t e, ki imajo podobno z gr adbo k ot r azisk ani les. Razisk ana vr s t a T1 (slik a 6 A , B , C) ima diagno - s tično pomem bne znak e: v elik e tr aheje v r adialnih sk upinah, ak sialni par enhim krilas t, vlakna z debeli - mi s t enami, he t er og eni tr ak o vi s š t e vilnimi r ombo - idnimi kris t ali in s tiloidi, tr aheje z enos t a vnimi per - f or acijami, enor edni tr ak o vi, in t er v ask ularne piknje izmenične in naspr otne. V r s t a T2 je po naboru znak o v podobna lesu v r ste Dicorynia guianensis (Ang élique, basr alocus) iz družine F abaceae-Caesalpinioideae, ki uspe v a v tr op ski južni Ameriki. T3 ima podobno z gr adbo k ot vr s t e iz r odu Afzelia sp. (a f z eli a, doussie), F abaceae - -Ceasilpinoidae iz tr op sk e Afr ik e. T4 pa je podoben vr s ti Lophira alata (az obe, bo ng ossi), Ochnaceae iz tr op sk e Afrik e. Pri ug ot o vljenem naboru lesnih vr s t in popol - nem po manjk anju na v edb o iz v oru lesa, je B3 ti- pičen iz delek globalne tr g o vine, kjer sledljiv os t ni mog oč a. T o vr s tni iz delki so pog os t o tudi slab še k a- k o v os ti, k ar s t a pok az ala St ar e in Prislan (2020), ki s t a pr eisk ala iz delek iz is t e v erig e k ot je B3 in njeg o- v a k ak o v os t ni bila skladna s s t andar dom EN 1860-2 (2005). V gla vnem v elja, da je k ak o v os tno oglje suho , tr dno , s k osi enak omerne v elik os ti in se pr e tir ano ne dr ob i, t oplo t o oddaja enak omerno in g ori (o zir o- ma tli) z z elo malo dima (St ar e & Prislan, 2020). Pri t em E vr op ski s t andar d SIS T EN 1860-2:2005 opr e - deljuje na t ančna merila z a k ak o v os t oglja z a ž ar in na v aja pe t ključnih k az alnik o v z vidik a: (1) vlažnos ti oglja (čim nižja ali ≤ 8 %), (2) k oličine pepela, (3) v sebnos ti hlapnih sno vi (po v e z ane s k oličino dima), (4) k olič ine v e z aneg a ogljik a (sor azmerno s k oličino oddane t oplotne ener gije na enot o t e ž e oglja t er daljšim in čis t ejšim iz g or e v anjem) in (5) v elik os ti delce v oglja. St ar e in Prislan (2020) ug ot a vlja t a, da je imelo k ak o v os t skladno s s t andar dom samo slo - v ensk o oglje iz oglar sk e de ž ele, ki je po naši oceni primerljiv o z našim iz delk om B1. Čepr a v vr s t a lesa z a oglje ni vključena v krit erije s t andar da, se v Slo - v eniji prič ak uje, da je najbol jše oglje iz buk o vine. Ug ot o vljeni šir ok nabor dom ačih in tr op skih vr s t v pr eisk anih iz delkih s polic tr g o vin z a t o nak az uje, da bi bilo tr eba splošno in s tr ok o vno ja vnos t vključno z nadz ornimi slu žbami v Slo v eniji in šir ši r egiji o z a v es- titi, da tudi v primeru oglja po manjk anje sledljiv os ti po v ečuje ne v arnos t nedo v olj ene tr g o vine z lesom. Na osno vi ug ot o vit e v r azisk a v e se pridruž ujemo po ziv om ob se žnejših pr ojek t o v v E vr opi, da bi bilo tudi tr g o vino z ogljem tr eba nadz or o v a ti v skladu z Ur edbo EU o lesu (EUTR). 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