Izmerjena je bila vsebnost pepela in silicijevega dioksida za 28 tropskih afriških listavcev in ene enokaličnice (Dracaena mannii). Vsebnost pepela je močno variirala. Večina zabeleženih vrednosti se je gibala med 0,3-1,4 %. Najvišja vrednost je bila zabeležena pri Desplatsia floribunda (4,54 %) in najnižja pri Pachyleasma tessmannii (0,07 %). Pri večini vrst je bil SiO2 določen le v sledeh (manj kot 0,01 %). Njegova vsebnost nad 0,1 % je bila izmerjena le pri Gambea beguei (0,128 %) in Manilkara fouilloyana (0,138 %).Data on ash and silica content of 28 Central African hardwoods and one monocotyledon (Dracaena mannii) are presented. Ash content varied considerably. Most of the values were in the range 0.3 - 1.4 %. The highest value was noted for Desplatsia floribunda (4.54 %) and the lowest for Pachyleasma tessmannii (0.07 %). In most species, silica was present only in trace amounts (less than 0.01 %). More than 0.1 % silica was found only in theGambea beguei (0.128 %) and Manilkara fouilloyana (0.138 %)

Piškur, Mitja

Tišler, Vesna

Torelli, Niko

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Zbornik gozdarstva in lesarstva 72, s. 53 - 61  GDK  174 + 175 . (67) + 813.3 : 813.5 Prispelo / Received: 05.01.2003 Izvirni znanstveni članek Sprejeto / Accepted: 21.11.2003 Original scientific paper  WOOD SPECIES OF THE CENTRAL AFRICAN REPUBLIC: ASH AND SILICA CONTENT   Niko TORELLI*, Mitja PIŠKUR*, Vesna TIŠLER**  Abstract  Data on ash and silica content of 28 Central African hardwoods and one monocotyledon (Dracaena mannii) are presented. Ash content varied considerably. Most of the values were in the range 0.3 - 1.4 %. The highest value was noted for Desplatsia floribunda (4.54 %) and the lowest for Pachyleasma tessmannii (0.07 %). In most species, silica was present only in trace amounts (less than 0.01 %). More than 0.1 % silica was found only in the Gambea beguei (0.128 %) and Manilkara fouilloyana (0.138 %). Key words: Central African wood species, ash content, silica content, Albizzia adianthifolia, Anthostema aubryanum, Blighia welwitschii, Celtis zenkeri, Combretodendron africanum, Croton aubrevillei, Desplatsia floribunda, Detarium macrocarpum, Dracaena mannii, Ficus sp., Gambea beguei, Gambea boukokoensis, Macaranga barteri, Manilkara fouilloyana, Marquesia excelsa, Morinda lucida, Oldfieldia africana, Pachyleasma tessmannii, Parkia filicoidea, Polyalthia suaveolens, Rauvolfia macrophylla, Stemonocoleus micranthus, Swartzia fistuloides, Tessmannia africana, Tessmannia lescrauwetii, Treculia africana, Tridesmostemon omphalocarpoides, Xylopia hypolampsa  LESNE VRSTE CENTRALNOAFRIŠKE REPUBLIKE: VSEBNOST PEPELA IN SILIKATOV  Izvleček Izmerjena je bila vsebnost pepela in silicijevega dioksida za 28 tropskih afriških listavcev in ene enokaličnice (Dracaena mannii). Vsebnost pepela je močno variirala. Večina zabeleženih vrednosti  se  je gibala med 0,3-1,4 %. Najvišja vrednost je bila zabeležena pri Desplatsia floribunda (4,54 %) in najnižja pri Pachyleasma tessmannii (0,07 %). Pri večini vrst je bil SiO2 določen le v sledeh (manj kot 0,01 %). Njegova vsebnost nad 0,1 % je bila izmerjena le pri Gambea beguei (0,128 %) in Manilkara fouilloyana (0,138 %). Ključne besede: Centralnoafriške lesne vrste, vsebnost pepela, vsebnost silikatov, Albizzia adianthifolia, Anthostema aubryanum, Blighia welwitschii, Celtis zenkeri, Combretodendron africanum, Croton aubrevillei, Desplatsia floribunda, Detarium macrocarpum, Dracaena Mannii, Ficus sp., Gambea beguei, Gambea boukokoensis, Macaranga barteri, Manilkara fouilloyana, Marquesia excelsa, Morinda lucida, Oldfieldia africana, Pachyleasma tessmannii, Parkia filicoidea, Polyalthia suaveolens, Rauvolfia macrophylla, Stemonocoleus micranthus, Swartzia fistuloides, Tessmannia africana, Tessmannia lescrauwetii, Treculia africana, Tridesmostemon omphalocarpoides, Xylopia hypolampsa                                             * Gozdarski inštitut Slovenije, Večna pot 2, 1000 Ljubljana, SVN ** Biotehnična fakulteta, Oddelek za lesarstvo, Rožna dolina c. VIII/34, Ljubljana, SVN 54 Zbornik gozdarstva in lesarstva, 72  VSEBINA CONTENTS  1 INTRODUCTION ..........................................................................55  UVOD 2 MATERIAL AND METHODS .....................................................56  MATERIAL IN METODE 3 RESULTS AND DISCUSSION .....................................................56  REZULTATI IN DISKUSIJA 4 POVZETEK ....................................................................................59 5 REFERENCES ...............................................................................60  VIRI 6 ACKNOWLEDGEMENTS ...........................................................61  ZAHVALA  55 Torelli N., Piškur M., Tišler V.: Lesne vrste Centralnoafriške republike ...  1 INTRODUCTION  UVOD  In general, wood possesses a characteristic composition. The same major components are present in all woods. The kinds and amounts of certain minor components are determined to a great extent by species. Small variations are found from tree to tree and in different parts of the same tree (BROWNING 1967).  In summative analysis, ash is often not included but just lignin, cellulose, hemicelluloses and extractives. Summation of ash changes the result from about 99 % to 101 % for most temperate-zone woods. Greater error could arise for tropical woods.  Inorganic substances largely appear in the ash, but some could be volatilised during ashing. In the absence of volatile components, the residue after incineration should be used as test sample, and the major inorganic constituents can be determined by conventional gravimetric or volumetric methods.  It is possible to use some spectrophotometric methods, atomic absorption spectroscopy, potentiometric, complexometric and redox titrimetry, etc. More sophisticated methods include activation analysis and ray emission spectroscopy. By combination of different analytical techniques, special studies can be done (SJÖSTROM / ALEN 1998).  The inorganic components in wood are various salts of carbonates, silicates, phosphates and oxalates, so that the major components of wood ashes are calcium, potassium, sodium, magnesium, iron, silica, phosphate, sulphate, chloride, and carbonate. The components are not distributed uniformly throughout the tissue, but are typically localised with respect to cell structure.  Silica is rarely present in more than trace amounts in temperate climate woods, but can vary in tropical woods from a mere trace to as much as 9 % (SANDERMANN 1966, TORELLI / ČUFAR 1995). More than 0.5 % of silica in wood is harmful to cutting tools (PETTERSON 1984, GOTTWALD 1973), and the machinability of wood is decisively influenced if the silica content is 1-3%. Silica has similar effect on the boring apparatus of marine animals. Even low-density woods are difficult to machine when their silica content is high (NOACK / FRÜHWALD 1977). The cutting process is affected chiefly by basic density, silica content and moisture content. Their influence, however, is intensified by a number of accompanying parameters, such as wood texture (interlocked grain), bark, accessory substances and by 56 Zbornik gozdarstva in lesarstva, 72  various anomalies. Silica often results in nasal irritation on many people. Some investigators have attempted to evaluate the diagnostic value of siliceous inclusions (AMOS 1952, WELLE 1976). It is recognized that silica levels can vary within a single tree and within one species depending on location and growth conditions.    2 MATERIAL AND METHODS  MATERIAL IN METODE  Test trees were taken from the extreme southwest part of the République Centrafricaine near the triple border with the République Populaire du Congo and République Fédérale du Cameroun. The location is situated approximately between 2º46'' and 3º00'' north latitude and east of the Sangha River (left bank) and covers the regions of the Kenie, Massapoula and Yobe river basins. For each randomly selected test tree, 10 samples were taken from the peripheral part of the heartwood when present or from stem periphery in species without colored heartwood (Table 1). The number of test trees is given in Table 1.   Determination of ash content of the oven-dry wood and silica content is described in the literature (BROWNING 1967, SIEBER 1951).   3 RESULTS AND DISCUSSION  REZULTATI IN DISKUSIJA  The results of ash content and silica content are shown in Table 1. Ash content varied considerably. Most of the values were in the range of 0.30 to 1.40 % and rarely above 2.00 %. Especially high values were noted for Desplatsia floribunda Burret (4.54 %), Oldfieldia africana Benth. & Hook. f. (2.42 %) and monocotyledon Dracaena mannii Baker (2.08 %). Two species had low ash content: Pachyleasma tessmannii Harms (0.07 %) and Stemonocoleus micranthus Harms (0.17 %). Most of the species tested contained an insignificant amount of silica, less than 0.01 % based on the oven-dry weight of the wood. Somewhat higher values were determined in Oldfieldia africana Benth. & Hook. f. (0.02 %), and Desplatsia floribunda Burret (0.04 %). Only two species contained significant, though not critical, amounts of silica: Manilkara fouilloyana Aubrev. & Pellegr. (0.14 %) and Gambea beguei Aubrev. & Pellegr. (0.13 %). 57 Torelli N., Piškur M., Tišler V.: Lesne vrste Centralnoafriške republike ...  Table 1: Wood species of the Central African Republic: ash and silica content Preglednica 1: Lesne vrste centralnoafriške republike: vsebnost pepela in silikatov  Density Ash content of the oven-dry wood Silica content Botanical and common names Family No. of trees testedOblig. colored heartwood ρ0 kg/m3 Average [%] of the ash  Average [%] of the oven-dry wood  Average [%] Albizzia adianthifolia (Schumach.) W.F. Wight ebamba, sakandi Mimosaceae 1 * 590 0.77 0.71 0.005 Anthostema aubryanum Baill - Euphorbiaceae 1 — 317 1.20 0.81 0.010 Blighia welwitschii(Hiern) Radlk. botoko, wotoko Sapindaceae 1 * 897 1.33 0.95 0.012 Celtis zenkeri Engl. Ngombe, gbolo, kakala, ohia Ulmaceae 5 — 707 0.67 0.87 0.006 Combretodendron africanum (Welw.) Exell dosso, mbosse, abale Lecythidaceae 5 * 841 0.32 0.82 0.003 Croton aubrevillei J. Leonardi molinga, tesso Euphorbiaceae 5 — 673 0.48 0.83 0.004 Desplatsia floribunda Burret korou Tiliaceae 1 — 492 4.54 0.92 0.042 Detarium macrocarpum Harms eboto, alen Caesalpiniaceae 5 * 647 0.68 0.86 0.006 Dracaena mannii Baker geke, lobe Dracaenaceae 5 — 338 2.08 0.66 0.014 Ficus sp.  - Moraceae 1 — 604 1.84 0.76 0.013 Gambea beguei Aubr. Et Pellegr. - Sapotaceae 1  662 1.23 10.85 0.128  58 Zbornik gozdarstva in lesarstva, 72  Table 1: Wood species of the Central African Republic: ash and silica content - continuation Preglednica 1: Lesne vrste centralnoafriške republike: vsebnost pepela in silikatov - nadaljevanje  Density Ash content of the oven-dry wood Silica content Botanical and common names Family No. of trees testedOblig. colored heartwood ρ0 kg/m3 Average [%] of the ash Average [%] of the oven-dry wood  Average [%] Gambea boukokoensis Aubr. Et Pellegr. libele-yongue Sapotaceae 1 — 710 0.46 0.88 0.004 Macaranga barteri Műll.-Arg. - Euphorbiaceae 1 — 442 0.80 1.15 0.009 Manilkara fouilloyana Aubrev.&Pellegr fou, mounguinza Sapotaceae 5 * 904 0.61 18.28 0.138 Marquesia excelsa (Pierre) R.E. Fries - Dipterocarpaceae 1 — 607 1.77 0.51 0.010 Morinda lucida Benth. dongbolongoya Rubiaceae 1 — 654 1.12 0.70 0.008 Oldfieldia africana Benth.&Hook. f. ndombo Euphorbiaceae 5 — 370 2.42 0.81 0.020 Pachylesma tessmannii Harms duoma ya zaba, dogabela, gabela Caesalpiniaceae 5 * 751 0.07 1.95 0.002 Parkia filicoidea Welw. zigna ou zien Mimosaceae 1 — 471 1.12 0.93 0.010 Polyalthia suaveolens Engler et Diels bapo, etounga Annonaceae 1 — 783 0.86 0.87 0.007 Rauvolfia macrophylla Stapf. - Apocynaceae 1 — 564 0.73 1.03 0.008 Stemonocoleus micranthus Harms tengi Caesalpiniaceae 1 * 586 0.17 1.44 0.002 59 Torelli N., Piškur M., Tišler V.: Lesne vrste Centralnoafriške republike ...  Table 1: Wood species of the Central African Republic: ash and silica content - continuation Preglednica 1: Lesne vrste centralnoafriške republike: vsebnost pepela in silikatov - nadaljevanje  Density Ash content of the oven-dry wood Silica content Botanical and common names Family No. of trees testedOblig. colored heartwood ρ0 kg/m3 Average [%] of the ash  Average [%] of the oven-dry wood  Average [%] Swartzia fistuloidesHarms pau rossa Caesalpiniaceae 5 * 1017 0.37 0.94 0.003 Tessmannia africana Harms paka, wamba, tou-nzeng Caesalpiniaceae 5 * 910 0.47 0.77 0.004 Tessmannia lescrauwaetii (De Wild.) Harms gama, tou-nzeng Caesalpiniaceae 5 * 910 0.47 0.72 0.004 Treculia africana Decaisne - Moraceae 1 — 674 1.04 0.97 0.010 Tridesmostemon omphalocarpoides Engl. bongoforo Sapotaceae 1 * 1093 0.62 0.77 0.005 Xylopia hypolampsa  Mildbr.&Diels  - Annonaceae 5 — 790 0.88 0.68 0.006 Legend: * = Oblig. colored heartwood present;  - = Oblig. colored heartwood not present   4 POVZETEK  V okviru slovensko ameriškega projekta YO-FS-74-JB-10 so bile raziskane biološke, fizikalne, kemične in mehanske lastnosti lesov 28 neznanih in manj znanih lesnih vrst iz Centralnoafriške republike. Silikati se le izjemoma pojavljajo v lesovih zmernega pasu, medtem ko so pri tropskem drevju redna akcesorna sestavina, ki lahko v ekstremnih primerih doseže 9 % mase absolutno suhega lesa. Vsebnost, večja od 0,5 %, že škodljivo deluje na rezila, vsebnost nad 1 % pa je ekonomsko kritična zaradi visoke obrabe. Silikati 60 Zbornik gozdarstva in lesarstva, 72  se v lesu lahko pojavljajo v najrazličnejših oblikah, ki imajo lahko tudi določeno lesno diagnostično oziroma identifikacijsko vrednost (AMOS 1952, WELLE 1976). Najdemo jih v aksialnem in trakovnem parenhimu in le redko v trahejah in vlaknih.   Raziskane vrste iz ekvatorialne Afrike imajo zelo nizko vsebnost silikatov, ki je z vidika obdelave in predelave lesa neškodljiva. Vsebnost pepela preiskanih vrst je bila med 0,07 % (Pachyleasma tessmannii Harms) in 4,54 % (Desplatsia floribunda Burret). Vsebnost silicijevega dioksida je bila med 0,002 % (Pachyleasma tessmannii Harms) in 0,138 % (Manilkara fouilloyana Aubrev. & Pellegr.).   5 REFERENCES  VIRI  AMOS, L., 1952. Silica in timbers.- Commonwealth Scientific and Industrial Research Organization, Australia, Bulletin No. 267:55 s. BROWNING, B. L., 1967. Methods of wood chemistry.- New York, John Wiley and Sons, s. 12, s. 302. GOTTWALD, H., 1973. Die Bedeutung der Holzanatomie für die Voraussage von Holzeigenschaften.- Holzforschung 27,2: 48-51. NOACK, D. A. / FRÜHWALD, A., 1977. The influence of wood properties on wood processing.-  IUFRO - Joint Meeting of the Subject Group S 5.04 and the Project Group 5.01. Merida, Venezuela. PETTERSEN, R. C., 1984. The chemical Composition of Wood.- V: ROWELL, R. (ed.), The Chemistry of Solid Wood. Washington, D. C., American Chemical Society, s. 57-126. SANDERMANN, W., 1966. Holzinhaltstoffe, ihre Chemie und Biochemie.- Naturwissenschaften 53,20: 513-525. SIEBER, R., 1951. Die Chemisch-Technischen Untersuchungs-Methoden der Zellstoff- und Papier-Industrie.- Berlin, Springer-Verlag, s. 13. SJÖSTRÖM, E. / ALEN, R., 1998. Analytical methods in wood chemistry, pulping, and papermaking.- Springer, s. 287-288. TORELLI, N. / ČUFAR, K., 1995. Mexican tropical hardwoods. Comparative study of ash and silica content.- Holz als Roh - und Werkstoff 53: 61-62. 61 Torelli N., Piškur M., Tišler V.: Lesne vrste Centralnoafriške republike ...  WELLE, B. J. H. ter 1976. Silica grains in woody plants of the Neotropis, especially Surinam.- V: Wood Structure in Biological and Technological Research: 107-142.   6 ACKNOWLEDGEMENTS  ZAHVALA  We wish to express our appreciation to the National Institute of Chemistry, Analytical Chemistry Laboratory, Ljubljana and Faculty of Chemistry and Chemical Technology, University of Ljubljana and particularly to Dr S. Gomišček and Dr J. Golob for providing us with most valuable advice and laboratory support. 62 Zbornik gozdarstva in lesarstva, 72       

Lesne vrste centralnoafriške republike : vsebnost pepela in silikatov

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