Elias Voulgaridis

Variation of certain chemical properties within the stemwood of black locust (Robinia pseudoacacia L.)

From the bottom, middle, and top of three mature 35 to 37-year old black locust tree discs were cut and analysed to determine the variation within the stem of certain chemical properties. Hot-water extractive content was greater in heartwood than in sapwood, while the reverse occurred for the dichloromethane extractive content. Vertical stem analysis of hot-water extractives showed that they increased in heartwood but decreasedin sapwood from the bottom to the top of the stems while the reversal occurred for dichloromethane extractive content of sapwood. At the bottom and the middle of the stems, ash content was greater in sapwood than in heartwood, but at the top no difference was found between heartwood and sapwood. Ash content of both heartwood and sapwood was found to increase in the axial direction with respective values of 0.36% (bottom) and 0.76% (top) for heartwood and of 0.65% (bottom) and 0.76% (top) for sapwood. Ash analysis showed that considerable variations were found for the inorganic elements K and P being greater in sapwood than in heartwood. Heartwood was more acid than sapwood except for the top of the stems. Acidity mean values were found to increase from the bottom to the top of the stems in heartwood while they slightly decreased in sapwood. Total buffering capacity of heartwood was greater than that of sapwood and total buffering capacity of sapwood exhibited an inverse relationship to height. Very small acid equivalent values were determined only in sapwood. At the bottom, lignin content in heartwood (25.73%) was greater than in sapwood (18.13%). Lignin content of heartwood decreased from 25.73% at the bottom to 18.33% at the top, while that of sapwood was 18.13% at the bottom, 21.42% at the middle and 19.64% at the top. Zusammenfassung Vom unteren, mittleren und oberen Teil der Stämme von drei ausgewachsenen 35–37 Jahre alten Robinien wurden Stammscheiben herausgeschnitten und analysiert, um die Variation bestimmter chemischer Eigenschaften innerhalb des Stammes zu bestimmen. Insgesamt war der Heisswasser-Extraktstoffgehalt im Kernholz höher als im Splintholz, während für den Di-Chlormethan-Extraktstoffgehalt das Gegenteil der Fall war. Die senkrechte Stammanalyse der Heisswasser-Extraktstoffe ergab, dass der Extraktstoffgehalt im Kernholz vom unteren Stammende zum Zopf hin zunahm, aber im Splintholz abnahm, während der Di-Chlormethan-Extraktstoffgehalt im Splintholz zum Zopf hin zunahm. Die unteren und mittleren Stammteile wiesen im Splintholz einen höheren Aschegehalt auf als im Kernholz. Im oberen Teil unterschied sich der Aschegehalt zwischen Kern- und Splintholz nicht. Der Aschegehalt stieg sowohl im Kern- als auch im Splintholz in Stammlängsrichtung an, im Kernholz von 0.36% (unten) auf 0.76% (oben) und im Splintholz von 0.65% (unten) auf 0.76% (oben). Die Aschenanalyse ergab beträchtliche Schwankungen bei den anorganischen Elementen K und P. Im Splintholz waren diese höher als im Kernholz. Das Kernholz lag mit Ausnahme des oberen Stammbereichs mehr im sauren Bereich als Splintholz. Die durchschnittlichen Säurewerte nahmen im Kernholz in Stammlängsrichtung von unten nach oben zu und im Splintholz leicht ab. Die Gesamtpufferkapazität im Kernholz war grösser als im Splintholz, wo sie mit zunehmender Stammhöhe abnahm. Der Ligningehalt war im unteren Stammbereich im Kernholz höher (25.73%) als im Splintholz (18.13%). Im Kernholz verringerte sich der Ligningehalt von 25.73% im unteren Stammbereich auf 18.33% im Zopfbereich, während der Ligningehalt im Splintholz im unteren Teil bei 18.13% lag, in der Mitte bei 21.42% und im Zopfbereich bei 19.64%.

Water repellent efficiency of organic solvent extractives from Aleppo pine leaves and bark applied to wood

Summary Natural wax-like materials were extracted from leaves and bark of Aleppo pine (Pinus halepensis Mill.) by using toluene as organic solvent. Experimental water repellent formulations (WRFs) were prepared using 10% gum rosin as the resin constituent and 0%, 1% and 2% paraffin wax, pine needle/bark extracts or mixtures of paraffin wax and needle/bark extracts in proportion 1 : 1 as hydrophobic substance. All experimental WRFs applied to small, cross-sectional wood specimens of Scots pine (Pinus sylvestris L.) and beech (Fagus sylvatica L.). Wood specimens were impregnated by a simple immersion technique and the water repellent effectiveness (WRE) was assessed by using tangential swelling data. Toluene soluble extracts from needles and bark applied to wood provided hydrophobic properties to pine and beech wood specimens but to a lesser degree when compared to paraffin wax. Bark extracts appeared to be stronger hydrophobic materials than needle extracts. Both needle and bark extracts can be successful substitutes for paraffin wax in WRFs up to 50 %. The degree of protection provided by WRFs and the differences between treatments were smaller in pine heartwood and beech sapwood than in pine sapwood.

Experimental particleboards from Kenaf plantations grown in Greece

Hibiscus cannabinus L.) plantation grown in N.Greece during the period June–October 1996 provided the raw material for experimental particleboards. After harvesting, the kenaf stems were storaged under shelter for a week, the core of each stem was separated from bark and both were dried at about 20% and 10% moisture content, respectively, and chipped by a hammermill. Kenaf core, bast fibers and industrial wood chips were mixed in various proportions in order to produce three-layer E2 grade UF bonded particleboards. Kenaf core chips were characterized by a lower slenderness ratio than wood chips of the middle layer. Bulk density of both core chips and fibers was lower than that of wood chips. Substitution of wood chips with kenaf core chips in the middle layer up to 75% slightly affects static bending and internal bond of the boards, but reduces screw holding strength and increases water absorption and thickness swelling; a 100% substitution deteriorates all properties except static bending. In boards with surface layers from kenaf bast fibers or from fibers:wood chips (50:50), static bending and surface roughness are improved, while the other properties tested are deteriorated. Substitution of kenaf core chips in the middle layer with fibers in proportion 50% negatively affects the board properties except static bending. It can be concluded that core chips and bast fibers from kenaf stems may substitute industrial wood chips in the middle and surface layers of the boards, respectively, up to 50%.Hibiscus cannabinus L.) in N. Griechenland. Nach der Ernte wurden die Kenafstengel für eine Woche unter Dach gelagert, dann wurde das Holzgewebe im Stengelinneren von der Rindenschicht getrennt, anschliessend auf ca. 20% bzw. 10% Feuchtigkeit getrocknet und beides in einer Hammermühle zerkleinert. Die Herstellung dreischichtiger harnstoffharzverleimter (E2 Typ) Spanplatten erfolgte unter Verwendung verschiedener Beimischungen aus Kenafholzspänen, Kenaffasern und Industrieholzspänen. Kenafholzspäne und Kenaffasern zeichnen sich durch eine niedrigere Streudichte als Industrieholzspäne aus; darüberhinaus weisen Kenafholzspäne einen niedrigeren Schlankheitsgrad auf im Vergleich zu den Mittelschichtspänen der Industrie. Der Ersatz von Industrieholzspänen durch Kenafholzspäne in der Plattenmittelschicht bis zu einem Anteil von 75% beeinflusst unwesentlich die Biege-, und Querzugfestigkeit der Platten, hat aber eine negative Auswirkung auf das Schraubenhaltevermögen, die Dickenquellung und die Wasseraufnahme; ein Zusatz von 100% Kenafholzspänen zur Mittelschicht bewirkt eine Verschlechterung aller Spanplatteneigenschaften mit Ausnahme der Biegefestigkeit. Spanplatten, deren Deckschichten aus reinen Kenaffasern oder aus einer Beimischung von Kenaffasern und Industrieholzspänen in einem Verhältnis von 50:50 bestehen, weisen höhere Qualität bezüglich Biegefestigkeit und Oberflächenrauhigkeit auf, aber niedrigere hinsichtlich der übrigen Eigenschaften. Der Ersatz von Kenafholzspänen durch Kenaffasern in der Plattenmittelschicht hat, abgesehen von der Biegefestigkeit, einen negativen Einfluss auf alle Platteneigenschaften. In ihrer Gesamtheit führte die Untersuchung zu dem Resultat, dass der Zusatz von Kenafholzspänen und Kenaffasern in der Mittelschicht bzw. der Deckschicht von Spanplatten bis zu einem Anteil von 50% möglich ist.

ANATOMICAL CHARACTERISTICS AND PROPERTIES OF KENAF STEMS (HIBISCUS CANNABINUS)

From a kenaf plantation (Hibiscus cannabinus L.) established in North Greece, a number of stem sections were taken from three positions (base, middle and top) and cell morphology, anatomical appearance under SEM and basic technical properties were observed and determined. Kenaf plants had a maximum height of 2.53 m, with a mean basal diameter of 1.91 cm. The wood is the most abundant tissue with proportions up to 77% in cross-section area and up to 61.5% in weight. Wood proportions decrease, pith proportions increase and bark proportions remain constant from the base to the top of the stems. The dry density of stems ranged between 0.27–0.31 g /cm3, while that of wood ranged between 0.22–0.43 g /cm3 along the stems. The contents of hot water soluble extractives ranged between 10.6% and 20.4% and those of dichloromethane soluble extractives ranged between 0.7% and 1.2% for bark, wood and pith. Microscopic examination of stems and of macerated material showed that bark consists of thick and long (2,330 μm) fibres whilst pith consists of polygonal parenchymatous cells. Wood is diffuse- porous, fibres average 840 μm long, vessel members average 330 μm long and 45 μm in diameter and orthogonal parenchymatous cells are 90 μm long. Fibre lengths in both bark and wood increase from the base to the top of stem. Vessel diameters decrease from base to top, while vessel member lengths remain constant from base to middle but decrease at the top of the stem.

WITHIN-TREE VARIATION IN GROWTH RATE AND CELL DIMENSIONS IN THE WOOD OF BLACK LOCUST (ROBINIA PSEUDOACACIA) *

Black locust (Robinia pseudoacacia L.) is regarded as an important natural resource almost throughout the world but relatively little is known about the within-tree variability of the anatomical characteristics of its wood. Discs 2 cm thick were cut at 2.25 m intervals, from the ground level to the top from ten black locust trees, 18–37-years-old, from the University Forest of Taxiarchi, Chalkidiki, Greece. The discs were used for the determination of growth rate and cell dimensions (fiber length and vessel member length and diameter) and their withintree variability (radial, oblique, vertical). Growth rate increased within the first 5–9 growth rings from the pith and then gradually decreased. Oblique variation of growth rate did not exhibit any clear tendency but a decrease at the top. In the case of vertical variation, growth rate decreased gradually with the year of cambium formation. Radial variability curves were found to be typical for the dimensions of cells (fibers, vessel members) especially for the fiber length. A rapid increase in cell dimensions was observed in the first 7–11 growth rings, the juvenile zone. Oblique and vertical variation of cell dimensions did not exhibit any clear tendencies.

Oleoresin and gum rosin from Pinus halepensis Mill. as basic constituents in water repellent formulations applied to wood

Sapwood wafer and long specimens (6 mm and 15 cm in length, respectively) were prepared from air-dried wood sticks of poplar, beech, fir and pine and impregnated with a number of water repellent formulations (WRFs) by using a simple immersion technique or by application of vacuum. Water repellent components included oleoresin and gum rosin extracted from Aleppo pine trees, a synthetic resin, paraffin wax and, in some cases, the preservative TBTO. Water repellent effectiveness (WRE) was based on swelling or absorption data. All WRFs were found to afford a significant degree of protection against liquid water uptake in treated sapwood specimens. Differences in WRE were observed between wood species and between WRFs based either on oleoresin and gum rosin or on a synthetic resin but they were practically unimportant. No particular WRF tested showed a superiority in all cases. A general comparison between performance results of WRFs for each wood species and group of specimens suggests that the natural products oleoresin and gum rosin (grade WG, WW, N) can be regarded as successful substitutes for the synthetic resin tested when incorporated as basic constituents in WRFs.ZusammenfassungKleine und große Splintholzproben (6 mm und 15 cm Länge) wurden von luftgetrockneten Schnitthölzern der Holzarten Pappel, Buche, Tanne und Kiefer hergestellt und mit verschiedenen Wasserschutzmitteln durch Eintauchen oder Anwendung von Vakuum imprägniert. Die Komponenten der Wasserschutzmittel waren Naturharz und Kolophonium der Aleppokiefer, ein Kunstharz, Paraffin und in einigen Fällen das Schutzmittel TBTO. Die wasser-abweisende Wirksamkeit wurde anhand von Quellungs- und Wasseraufnahmebestimmungen ermittelt. Alle Wasserschutzmittel gewährten einen bedeutsamen Schutz der behandelten Splintholzproben gegen Wasseraufnahme. Es wurden Unterschiede hinsichtlich der wasserabweisenden Wirksamkeit zwischen den Holzarten und zwischen den Wasserschutzmitteln auf der Basis entweder von Naturharz und Kolophonium oder von Kunstharz festgestellt, die aber praktisch unbedeutend waren. Von den erprobten Wasserschutzmitteln zeigte keines eine Überlegenheit in allen untersuchten Fällen. Ein allgemeiner Vergleich zwischen der Wirksamkeit der getesteten Wasserschutzmittel hinsichtlich der Holzart und Probenform weist darauf hin, daß die Naturprodukte Harz und Kolophonium (Sorte WG, WW, N) als geeignete Ersatzstoffe für den erprobten Kunstharz angesehen werden können, wenn sie als Hauptkomponenten in Wasserschutzmitteln verwendet werden.

Wood cell morphology characteristics of some oak species and mediterranean shrubs

Some characteristics of wood cell morphology of three oak species (Quercus conferta, Q. ilex, Q. coccifera) and five Mediterranean shrubs (Arbutus andrachne, A. unedo, Erica arborea, Phillyrea media, Pistacia terebinthus) were investigated at height 30 cm above ground. The mean fiber length of oak species ranged between 1.10 and 1.35 mm and that of Mediterranean shrubs between 0.56 and 0.82 mm. The mean values of vessel dimensions ranged as follows: 0.22–0.31 mm (vessel length) and 0.080–0.087 mm (vessel diameter) for oaks and 0.19–0.40 mm (vessel length) and 0.033–0.043 mm (vessel diameter) for Mediterranean shrubs. The pith to bark variation of fiber length appeared to follow the general patterns of length variation but differences were observed between the species tested with regard to the rate of fiber length increase and to the number of years necessary to reach a typical length. The horizontal variation of vessel length and diameter was not consistent between the species; from pith to bark, vessel length and diameter increased in a few species and decreased or remained more or less unchanged in the others. For each species, a similar horizontal variation pattern of fiber length and, to a lesser extent, of vessel length was observed between the trees. The greatest pith to bark variation of three-ring mean values relative to the first three growth rings occurred in Quercus conferta for fiber and vessel length and in Quercus coccifera and Q. ilex for vessel diameter.ZusammenfassungEs wurden einige Kennzeichen der Zellmorphologie von drei Eichenarten (Quercus conferta, Q. ilex, Q. coccifera) und fünf Mittelmeersträuchern (Arbutus andrachne, A. unedo, Erica arobea, Phillyrea media, Pistacia terebinthus) in einer Höhe von 30 cm über dem Stammfuß untersucht. Der Mittelwert der Faserlänge der Eichenarten schwankte zwischen 1,10 und 1,35 mm und der Mittelmeersträucher zwischen 0,56 und 0,82 mm. Die Mittelwerte der Dimensionen der Gefäßglieder schwankten wie folgt: Länge und Durchmesser der Eichenarten von 0,22 bis 0,31 mm bzw. von 0,080 bis 0,087 mm und der Mittelmeersträucher von 0,19 bis 0,40 mm bzw. von 0,033 bis 0,043 mm. Die Variabilität der Faserlänge vom Mark zur Rinde entsprach dem allgemeinen Variabilitätsprofil der Faserlängen. Zwischen den untersuchten Holzarten wurden jedoch Unterschiede beobachtet hinsichtlich der Wachstumsgeschwindigkeit der Fasern und der Zeit, bis zu der die Fasern ihre typische Länge erreichen. Die horizontale Variabilität der Gefäßdimensionen zwischen den untersuchten Holzarten war nicht gleichmäßig; bei einigen Holzarten nahmen Länge und Durchmesser der Gefäßglieder vom Mark zur Rinde zu, während sie bei anderen abnahmen oder unverändert blieben. Die untersuchten Bäume jeder Holzart zeigten ein ähnliches Variabilitätsprofil in horizontaler Richtung bezüglich der Faserlänge und in geringerem Maße auch der Länge der Gefäßglieder. Die Mittelwerte der Zelldimensionen, bezogen auf den Mittelwert der ersten drei Wachstumsringe, zeigten ihre größte Variabilität vom Mark zur Rinde bei Quercus conferta hinsichtlich der Länge der Fasern und der Gefäßglieder sowie bei Quercus coccifera und Q. ilex hinsichtlich des Durchmessers der Gefäßglieder.

Ring width, latewood proportion and density relationships in black locust wood of different origins and clones.

Cross-sectional discs were cut at breast height from 19 black locust trees aged 18–39 years of different clones and origin (Greece, Bulgaria and Hungarian clones J, U and NY). Ring width, latewood proportion and dry density were measured according to standard laboratory techniques in order to examine their relationships. Latewood proportion was found to increase (except for one tree from Bulgaria) with increasing ring width and logarithmic equations were calculated with relatively high correlation coefficients. A positive relation between dry density and latewood proportion was found in black locust of Bulgarian origin and in the Hungarian clone NY while in all other cases no meaningful relationship was observed. In mature wood, improved positive linear correlations were observed between dry density and latewood proportion with the exception of the Hungarian clone U. Regression analysis revealed low correlations between dry density and ring width and only black locust from Bulgaria had a high positive correlation. The positive correlations between dry density and ring width were slightly improved in mature wood with the exception of clone J from Hungary.

Characteristics of Briarwood

Briarwood a tumor-likc outgrowth of Erica arborea was investigated with regard to anatomical structure, propcrtics, chcmical composition, and effects of treatments (boiling in water, cxposure to high temperatures). Comparisons were madc with stem and root wood of Erica, and some othcr temperatc and tropical wood specics. Briarwood was found to have shorter and irregulär fibers in comparison to stem wood; tissuc arrangement is usually irregulär, but some cross sections appear normal; cnclosurcs (amorphous, crystal) arc prcscnt in cell cavities. The density and hardncss of briarwood are a l i t t le higher than that of stem wood, Volumetrie shrinkage is higher, but dircetional shrinkage tends to bc isometric. Extractivc eontent is vcry high. Ash is higher, and silica low. Boiling in water (removal of cxtractives) reduccd the Volumetrie shrinkage of briarwood (the effcct is normally opposite), did not affect thc drying rate, but rcsulted in higher dimensional stability, and eliminatcd drying defects. Exposure to high temperatures (150—600 °C) showcd a higher rcsistance of briarwood, which could be attributed to cxlractivcs.

Wood quality and quantity of fir and beech natural forests in relation to site fertility in west-central Greece

Of the numerous environmental factors affecting tree growth, the relationship between site quality and tree growth seems to be the most important. In the present work, the wood production of fir (Abies borisii-regis Mattf.) and beech (Fagus sylvatica L.) natural forests on quantitative and qualitative basis was investigated in relation to site quality (II, III, IV for fir and II, III for beech). In this investigation, 268 hybrid fir and 228 beech trees growing in different site qualities were selected at the University forest of Pertouli and at the Aspropotamos forest district, Trikala, western-central Greece. For the grading of 559 (fir) and 787 (beech) produced logs, EN 1927-1:2008 and EN 1316-1:1997 standards were employed, respectively. The results showed that the site quality has an influence on both quantitative and qualitative production of both fir and beech produced wood. It was recorded that fir and beech trees grown in the better site quality (II), have attained the highest mean ring increment and produced the highest quantities of wood. Particularly, higher production and better quality of fir wood were obtained in the better site quality II, while in site quality III and, much more in site quality IV, the quantity and quality of roundwood produced were less and inferior. Beech roundwood production was higher and of better quality in site quality II than in the inferior site quality III.