Chemical characteristics of endemic oak-wood Quercus vulcanica Boiss

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Chemical characteristics of endemic oak-wood Quercus vulcanica Boiss Article in Holz als Roh- und Werkstoff · April 1999 DOI: 10.1007/s001070050032

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Kurz-Originalia á Brief Originals

Holz als Roh- und Werkstoff 57 (1999) 152±153 Ó Springer-Verlag 1999

Chemical characteristics of endemic oak-wood Quercus vulcanica Boiss

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M. Balaban, N. YilgoÈr È . Orman FakuÈltesi, 80895 BahcekoÈy, Istanbul, Turkey I. U C. Strobel Institute for Woodresearch, Winzererstr 45, 80797 MuÈnchen, Germany Introduction Vulcanic oak or, ``riddle-frame oak'' as named by the natives, occupies an area over 8000 ha's near the province Isparta in southern Turkey. In the so called ``Kasnak Forest'' it forms few pure stands but the tree itself frequently occurs in the companionship of its natural neighbours (Quercus cerris, Q. libani, Q. coccifera, Q. infectoria, Acer platanoides, A. monspessulanum, A. hyrcanum, Fraxinus ornus, F. oxycarpa, Sorbus torminalis, Populus tremuloides, Salix alba, Ostrya carpinifolia, Ulmus glabra, Cedrus libani, Pinus nigra, P. brutia, Abies cilicica, Juniperus oxycedrus, J. foetidissima, J. excelsa, etc.). Except for some solitary groups living on the western Taurus mountains in Anatolia there is no other place known where the vulcanic oak still naturally exists. The rich ¯ora makes the Kasnak Forest a true arboretum and the Kovada Lake within the forest completes the area to its full beauty. Because of intensive utilization of oak wood in the 80's and encountered dif®culties in reforestation and for reasons mentioned above, Kasnak Forest was declared as one of the famous national parks of Turkey in 1989. Hence, a very limited number of specimens can be taken for scienti®c purposes only and with an of®cial permission. Material and methods Two trees, 101 and 87 years old, from pure oak stands, both about 18 m high, were felled in the summer of 1997. The diameters of stems at the breast height were about 35 and 30 cm respectively. Every 2 meters, disks were cut out beginning at 40 cm from the bottom of each stem. After removing the bark, ®rst the sap- and heartwood were separated. The chipped wood was milled and screened from 40 to 100 mesh for the analysis. The determination of ash and extractives soluble in ethanol/ benzene, ethanol, hot water and in 1% NaOH was performed using TAPPI standards. Ultimate analyses of unextracted woods were carried out in a rapid analyzer (Hereaus). The Klason-Lignin contents were estimated acc. to the method by Runkel und Wilke (1952). Using acidi®ed NaClO2 solutions, the holocelluloses were prepared. After the successive extractions of holocelluloses with 5 and 24% KOH-solutions the alpha-celluloses were obtained. For the determination of pentosan the ISO-method using 3.2 M HBr solutions was applied to convert the pentoses in wood and holocellulose into furfural. The furfural was then measured spectroscopically at 277.3 nm. To determine the sugar-composition of holocelluloses the quantitave sacchari®cation following the TFA-hydrolysis (Fengel and Wegener 1979) was accomplished by means of ion exchange chromatography.

Table 1. Elementary composition and minor components of sapand heartwood of Quercus vulcanica Boiss. (all values are based on unextracted original wood) Substance Elementary Composition: C H O Ash Extractives: Cyclohexane Ethanol/Benzene (1.step) Ethanol (2. step) Hot water 1% NaOH

Sapwood (%)

Heartwood (%)

47.32 6.23 46.45 0.72

46.84 6.36 46.80 0.44

0.32 4.07 0.49 6.74 20.74

0.32 4.67 1.46 8.97 23.30

In the elementary composition of wood, nitrogen was found in traces and beyond the detectable amounts. The oxygen content was then calculated as a difference to 100 percent. As shown in Table 1, sap-as well as heartwood have very few extractives of unpolar character. In contrast, the woods exhibit large amounts of polar substances which is proven by the high solubility in hot water. Most of the 7±9% of wood soluble in water probably derives from tannins which generally occur in oak woods. On the other hand, rather uncommonly high amounts of substances are dissolved from woods with 1% NaOH which could be explained by easily soluble polyoses, especially pentosans. The NaClO2 deligni®cation increases the solubility of lignin in acids. Thus, the standard determination of lignin in holocellulose always results in lower yields. Due to this effect, the sum of contents of holocellulose corrected by the residual lignin and the lignin still exceeds 100 percent. Furthermore, Table 2 reveals that the sapwood contains slightly more cell wall components, i.e. cellulose, polyoses and lignin than heartwood, wheras the opposite holds true as far as the extractives are concerned. This is also in accordance with the earlier works (Fengel, Wegener 1988).

Table 2. The distrubution of main components in wood (data based on extracted wood) Substance

Lignin Holocellulose: with residual lignin (1) Results and discussions Though determined separately, the data residual lignin in holocel.(2) of the analyses from both trees were averaged for sap- and Holocel. calculated (1) ± (2) heartwood. Table 1 and 2 show the results of basic analyses Alpha-cellulose obtained in this way. Pentosan: in extracted wood in Holocellulose Correspondence to: M. Balaban

Sapwood (5)

Heartwood (%)

23.10

23.06

85.82 6.99 78.83 51.43

83.64 5.33 78.31 50.56

20.97 21.15

20.10 20.27

Table 3. The monosaccharide composition of woods (based on extracted wood)

Wood

Sapwood Heartwood

Monosaccharides ( % ) Rhamnose

Mannose

Arabinose

Galactose

Xylose

Glucose

0.33 0.29

2.14 2.50

0.79 0.77

0.89 0.91

20.36 19.76

49.40 48.82

analysis. In: Brown Jr., R. D. Jurassek, L. (Eds.): Hydrolysis of The comparison of pentosan data found in wood and holocellulose; mechanism of enzymatic and acid catalysis. Adcellulose indicates that almost imperceptible losses of these easily vances in chemistry series no:181. Am. Chem. Soc. Washingsoluble polysaccharides had occurred during the deligni®cation. ton, pp. 145±158 To visualize the distribution of cellulose and polyoses in sapFengel D, Wegener G (1988) Wood ± Chemistry, ultrastructure, and heartwood quantitative sacchari®cation was conducted in reactions. Walter de Gruyter, Berlin, New York holocelluloses. The data in Table 3 show the composition of Runkel ROH, Wilke KD (1951) Zur Kenntnis des thermoplassugars typical for hardwoods. tischen Verhaltens von Holz. II. Mittl. Holz Roh- Werkstoff 9: 260±270 References Fengel D, Wegener G (1979) Hydrolysis of polysaccharides with tri¯uoroacetic acid and its application to rapid wood and pulp

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