Gustoća i mehanička svojstva drva bjeljike hrasta u usporedbi s drvom srži

The aim of this study was to investigate the main mechanical properties of sapwood and heartwood in white and red oaks. Samples of wood were taken from 26 oak beams prepared to be used for railway sleepers, of which 62 % were from white oak (either Quercus petraea or. Q. robur) and 38 % from red oak group, represented by Q. cerris. For both oak groups, the following parameters were determined: the density, bending strength, modulus of elasticity (MOE), compression strength and Brinell hardness of sapwood and heartwood. Multiple analyses were done to compare the properties of sapwood and heartwood, as well as the properties of white vs. red oaks. The results revealed no significant differences between sapwood and heartwood properties but statistically significant differences were found between the properties of white and red oaks. The research results contradict the common opinion of users that the mechanical properties of sapwood are inferior to those of heartwood. Investigations revealed that Q. cerris had even better mechanical properties than Q. robur or Q. petraea, which also contradicts the common opinion that its mechanical properties are inferior to those of white oaks. The results help to understand better wood variability for optimal selection of timber for construction.Cilj ovog istraživanja bio je ispitati osnovna mehanička svojstva drva bjeljike i srži bijeloga i crvenog hrasta. Uzorci su uzeti od 26 hrastovih greda spremnih za izradu željezničkih pragova, od čega je 62 % greda od bijelog hrasta (Quercus petraea ili Q. robur ), a 38 % od skupine crvenih hrastova, čiji je predstavnik Q. cerris. Za drvo bjeljike i drvo srži obiju skupina hrasta određena je gustoća, čvrstoća na savijanje, modul elastičnosti (MOE), tlačna čvrstoća i tvrdoća prema Brinellu. Napravljene su višestruke analize radi usporedbe svojstava bjeljike i srži, kao i usporedbe svojstava drva bijelih i crvenih hrastova. Rezultati su pokazali da nema značajne razlike između svojstava drva bjeljike i srži, ali statistički značajne razlike pokazale su se između svojstava drva bijeloga i crvenog hrasta. Rezultati istraživanja proturječe uvriježenome mišljenju korisnika da su mehanička svojstva bijeljike lošija od mehaničkih svojstava drva srži. Istraživanja su pokazala da drvo Q. cerris ima čak i bolja mehanička svojstva nego drvo Q. robur i Q. petraea, što je također suprotno ustaljenom mišljenju da su njegova svojstva lošija od svojstava drva bijelog hrasta. Rezultati će pridonijeti boljem razumijevanju varijabilnosti svojstava drva i optimalnom izboru drva za gradnju

Density and mechanical properties of oak sapwood versus heartwood in three different oak species

The aim of this study was to investigate the main mechanical properties of sapwood and heartwood in white and red oaks. Samples of wood were taken from 26 oak beams prepared to be used for railway sleepers, of which 62% were from white oak (either Quercus petraea or Q. robur) and 38% from red oak group, represented by Q. cerris. For both oak groups, the following parameters were determined: the density, bending strength, modulus of elasticity (MOE), compression strength and Brinell hardness of sapwood and heartwood. Multiple analyses were done to compare the properties of sapwood and heartwood, as well as the properties of white vs. red oaks. The results revealed no significant differences between sapwood and heartwood properties but statistically significant differences were found between the properties of white and red oaks. The research results contradict the common opinion of users that the mechanical properties of sapwood are inferior to those of heartwood. Investigations revealed that Q. cerris had even better mechanical properties than Q. robur or Q. petraea, which also contradicts the common opinion that its mechanical properties are inferior to those of white oaks. The results help to understand better wood variability for optimal selection of timber for constructions

S projektom APPLAUSE od prepoznave do širše uporabe invazivnih rastlin z vključevanjem prebivalcev

Projekt APPLAUSE (Alien PLAnt SpEcies - from harmful to useful with citizens' led activities / od škodljivih do uporabnih tujerodnih rastlin z aktivnim vključevanjem prebivalcev), je bil izbran na evropskem razpisu pobude Urban Innovative Action (UIA). Skupno enajst partnerjev je zasnovalo model projekta APPLAUSE za celovit pregled lastnosti in primerno uporabo invazivnih rastlin, ki so čedalje bolj prisotne v našem okolju in nam izpodrivajo avtohtono rastje. Na razpis UIA je prispelo skupno 206 projektnih prijav iz 21 različnih držav Evropske unije, za financiranje pa je bilo izbranih 16 projektov. Evropska komisija UIA podpira inovativne pilotske projekte na področju trajnostnega urbanega razvoja, zato je v ta namen iz Evropskega sklada za regionalni razvoj namenila del sredstev lokalnim oblastem, ki bodo na nov način iskale rešitve dane tematike. Komisija je na izboru upoštevala stopnjo inovativnosti, kvaliteto partnerstva, merljivost rezultatov, možnost širitve rešitve na druga urbana območja in kakovost delovnega načrta projekta. Ocenjena vrednost projekta APPLAUSE je okoli 5,2 mio EUR, sofinanciranje iz EU sredstev znaša nekaj več kot 4,1 mio EUR. Projekt bo trajal 3 leta in sicer od 1. novembra 2017 do 31. oktobra 2020. Projekt v sklopu krožnega gospodarstva izpostavlja nerešena vprašanja glede ravnanja z invazivnimi tujerodnimi rastlinami v smislu zero-waste pristopa. V pilotnem projektu predelave japonskega dresnika v papir so že dokazali, da je tovrstno surovino mogoče izkoriščati veliko bolj racionalno kot zgolj za sežig. Tako se v okviru projekta predlaga sistem ravnanja s tujerodnimi invazivnimi rastlinami, ki temelji na izobraževanju in sodelovanju prebivalcev Ljubljane po treh principih delovanja: »Naredi sam«, »Predelaj z nami« in »Oddaj v zbirnem centru«. Poleg prijavitelja (Mestne občine Ljubljana) in Biotehniške fakultete (Oddelek za lesarstvo, Odd. za biologijo, Odd. za agronomijo in Odd. za gozdarstvo) sodelujejo še Fakulteta za kemijo in kemijsko tehnologijo; Naravoslovnotehniška fakulteta, Kemijski inštitut,  javno podjetje Snaga, Institut Jožef Stefan, Inštitut za celulozo in papir, Tisa d. o. o., GDi GISDATA d. o. o., društvo Trajna, Zavod tipoRenesansa in Center odličnosti Vesolje, znanost in tehnologije. Oddelek za lesarstvo ima ključno vlogo pri raz­iskavah zgradbe in relevantnih lastnosti  olesenelih tujerodnih rastlin, sodeluje pri razvoju, projektiranju in trženju novih izdelkov, izdelovanju prototipov in končnih izdelkov ter razvoju novih pilotnih produktov iz ostankov v lesnopredelovalni verigi. Oddelek s podjetjem Snaga sodeluje tudi pri projektiranju in pripravi lesnoobdelovalne (mizarske) delavnice. Celoten projekt je v osnovi oblikovan in zastavljen zeleno in inovativno, kar pomeni, da bo model prenosljiv na nova mednarodna območja oziroma okolja, pri čemer bodo omogočena nova delovna mesta, nova znanja in vključevanje težje zaposljivih ljudi z raznimi oviranostmi. V centrih ponovne uporabe bi se izvajale različne spretnostne in rokodelske delavnice s ciljemohranjati in razvijati tradicionalno obrt, kulturno dediščino ter znanje

Wood in the Banʼs house at Artiče, Slovenia, as a historical archive

Opravili smo raziskave lesa in dendrokronološko datiranje brun iz zunanjih sten stare Banove hiše iz vasi Artiče pri Brežicah. Bruna so bila iz lesa različnih hrastov - gradna (Quercus petraea), doba (Quercus robur) in cera (Quercus cerris), domačega kostanja (Castanea sativa) in navadne smreke (Piceaabies). Z dendrokronološkim datiranjem smo bruna razvrstili v skupine z leti zadnje branike 1535 (2 bruni - cer in dob/graden), 1563-1592 (8 brun - 5 cer in 3 dob/graden), 1613-1720 (3 bruna - dob/graden), 1779-1792 (7 brun - 4 dob/graden in 3 kostanj) in Ž 1913 (10 brun smreke). Les različnih lesnih vrst in datumov poseka je bil premešan po celotnem ostenju, kar nakazuje, da je bila hiša večkrat predelana, pri predelavah pa so ponovno uporabili les iz iste hiše ali drugih objektov. Ugotovitve o starosti in vrsti lesa smo dopolnili s podatki iz gozdarskih virov, ki kažejo, da je vgrajeni les najverjetneje lokalnega izvora.We conducted a survey of wood and performed dendrochronological dating of beams from the external walls of the old Banʼs House in the village of Artiče near Brežice. The logs were made of different wood species, with different oaks among them, i.e. sessile oak (Quercus petraea), pedunculate oak (Quercus robur) and Turkey oak (Quercus cerris), as well as sweet chestnut (Castanea sativa) and Norway spruce (Picea abies). Based on dendrochronological dating of the outermost tree-rings, the beams were divided into groups having the end dates of 1535 (2 beams - Turkey oak and pedunculate / sessile oak), 1563-1592 (8 logs - 5 Turkey oak and 3 pedunculate / sessile oak), 1613-1720 (3 logs - pedunculate / sessile oak), 1779-1792 (7 logs - 4 pedunculate / sessile oak and 3 chestnuts) and Ž 1913 (10 spruce logs). The beams of different wood species and with different end dates were mixed across the walls, indicating that the house had been rebuilt several times and that the timber from the same house or other buildings was re-used. Our assessments concerning different end dates and selection of several wood species were supplemented with information from forestry sources. They showed that the wood was very likely of local origin

Anatomy of reaction zones in beech (Fagus sylvatica L.)

Pri bukvi (Fagus sylvatica L.) smo raziskovali mejne kompartmentalizacijske plasti izvotljenih ter razkrajajočih se debelnih sredic. Mejne plasti pri vsehpreiskanih drevesih anatomsko ustrezajo reakcijskim conam in ne bariernim conam kot jih predpostavlja model CODIT. V osrednjem delu reakcijske cone so bile traheje intenzivno okludirane z gumoznimi snovmi in suberiziranimi tilami. Lumni trakovnega in aksialnega parenhima, vlaknastih traheid in vse pikenjske odprtine so bili zapolnjeni z netopnimi depoziti. Za notranji del reakcijskih con je značilen razkroj celičnih sten in depozitov, suberizirane strukture pa so ostale nespremenjene. Pri reakcijskih conah, ki mejijo neposredno na duplino, je ta del manjkal, na površini reakcijske cone v duplini so vidna trosišča gliv. Povečana količina škroba v parenhimskih celicah in različne razvojne faze til v zunanjem delu reakcijske cone kažejo na aktivne kompartmentalizacijske procese. Aktivna obrambna in pasivna zaščitna funkcija reakcijskih con v živem drevesu sta podrobneje analizirani.Compartmentalization boundary layers surrounding hollow and decaying stem cores were investigated in beech (Fagus sylvatica L.). In all investigated trees, boundary layers corresponded anatomically to the reaction zones and notto the barrier zones as proposed by the CODIT model. In the central part ofreaction zones, vessels were heavily occluded with deposits of gums and suberised tyloses, whereas the lumina of ray and axial parenchyma, fibre tracheids and all pit apertures were filed with insoluble deposits. The inner part of reaction zones exhibited decay of cell walls and deposits, leaving suberized structures intact. This part was absent in the reaction zones bordering directly on the hollow, although fungal fruit bodies were present onthe surface of the reaction zone. Increased amount of starch grains and different growing stages of tyloses in the outer part of reaction zones indicated active compartmentalization processes. The paper discusses in detailthe active defensive and passive protective function of reaction zones in the living trees

Optimalna priprema površine drva za istraživanje anatomije invazivnih vrsta drva pretražnim elektronskim mikroskopom

Research was done to develop the optimal method of wood surface preparation for scanning electron microscopy (SEM). Since 2018, environmental scanning electron microscope (ESEM™) FEI Quanta 250 has been installed at the Department of Wood Science and Technology in Ljubljana. We tested several methods for the pre-preparation and cutting of wood surfaces for SEM analyses. The samples had been either dried, soaked in water and frozen, impregnated with paraffin or simply moistened before cutting. We analysed wood surfaces obtained by splitting, sawing, planing, sanding and cutting on a sliding microtome with different blades. The effect of gold coating on the SEM image quality was also evaluated. Best results were obtained by cutting a pre-moistened surface on a sliding microtome with a low profile replaceable blade and gold coated afterwards. Determined methodology is technically less demanding, not time consuming and obtains results that satisfy needs for wood anatomy research at magnifications up to 12.000x. Guidelines for the optimal preparation of samples were prepared, and theoretical and practical basis for investigations of wood anatomy using SEM were provided. The method was afterwards used in analyses of invasive alien plant species – investigating their anatomical structure in the framework of the AlienPLAntSpEcies - APPLAUSE project (Urban Innovative Actions initiative). It was demonstrated that the use of the SEM opened new scope in detailed investigations of the wood structure and properties.Istraživanje je provedeno kako bi se razvila optimalna metoda pripreme drvne površine za pretražnu elektronsku mikroskopiju (SEM). Od 2018. na Odsjeku za znanost i tehnologiju o drvu u Ljubljani instaliran je uređaj za pretražnu elektronsku mikroskopiju u uvjetima okoliša (ESEMTM) FEI Quanta 250. Proučavali smo nekoliko metoda za pripremu i rezanje površine drva za SEM analizu. Uzorci su sušeni, potapani u vodi i smrzavani te prije rezanja impregnirani parafi nom ili samo navlaženi. Analizirali smo površine drva dobivene cijepanjem, piljenjem, blanjanjem, brušenjem i rezanjem na mikrotomu različitim oštricama. Također je proučavan utjecaj zlatnog premaza na kvalitetu SEM fotografi ja. Najbolji rezultati dobiveni su rezanjem prethodno navlažene površine na mikrotomu, i to zamjenjivim noževima niskog profi la, nakon čega je površina drva pozlaćena. Primijenjena je metodologija tehnički manje zahtjevna, ne oduzima mnogo vremena, a dobiveni rezultati zadovoljavaju potrebe istraživanja anatomije drva pri povećanju i do 12 000 puta. Sastavljene su smjernice za optimalnu pripremu uzoraka te je postavljena teorijska i praktična osnova za istraživanje anatomije drva primjenom SEM-a. Metoda je potom primijenjena za istraživanje invazivnih biljnih vrsta – za ispitivanje njihove anatomske strukture u sklopu projekta AlienPLAntSpEcies – APPLAUSE (Urban Innovative Actions). Potvrđeno je da je upotreba SEM-a otvorila novo područje u detaljnim istraživanjima strukture i svojstava drva

Wood identification using non-destructive confocal laser scanning microscopy

Exact wood identification is usually based on observation of wood features under the microscope. For this, we have to take a sample of the wood from the object and cut thin slides, possibly of all three anatomical sections. Such destructive sampling is often not possible on valuable historical objects, and therefore there is a need for non-destructive approaches. The objective of the study is to present the potential of Confocal Laser Scanning Microscopy (CLSM) using an Olympus LEXT OLS5000 for the identification of wood. We present work on an example of a gothic sculpture, “St. George Defeating the Dragon”. Conventional sampling and microscopical wood identification showed that St. George is made of Norway spruce (Picea abies), and the dragon of poplar (Populus sp.) or willow (Salix sp.). We present crucial features needed for the identification of these species and the limitations with identification if the samples are too small. Finally, we demonstrate the possibility of wood identification of the abovementioned species using CLSM on wood samples without special preparation of the surfaces. CLSM enabled us to observe all the features needed for wood identification

Drying characteristics of wood of invasive tree species growing in an urban environment

Non-native tree species are increasingly growing in urban environments, where they are exposed to cultivation and pruning measures, and in many cases their growth becomes uncontrolled, even invasive. In such cases the structure of the wood is more heterogeneous, with more tyloses, discolorations and decay, and higher moisture content. The drying of such wood is more demanding and cannot rely on the standard drying schedules. Therefore, the drying kinetics of the boards (thickness 22 mm, 28 mm and 46 mm) of three wood species (black locust – Robinia pseudoacacia; box elder – Acer negundo and horse chestnut – Aesculus hippocastanum) were analysed at 20 °C and 40 °C. Additionally, the drying quality was assessed by determining the moisture content gradient, drying stresses and presence of typical drying defects. In the drying tests the moisture content gradients were relatively low in all species, so no high drying stresses were generated. Due to the expected high risk of collapse, careful drying of green maple was needed, to prevent board twisting when a pronounced number of knots and greater fibre deviation occurred. Half-drying times indicated the longer drying of thicker black locust boards, and very careful drying of maple. We confirmed the usability of the half-drying time to compare the drying kinetics of different wood species and assortments