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1.
The wood quality from 50- to 70-year-old Tectona grandis trees from an unmanaged forest in East Timor was assessed. The aim was to evaluate teak in mature stands that had undergone
uncontrolled disturbances, e.g., fire and local community usage. Heartwood represented 91% of the tree radius at a height
of 1.7 m, and sapwood contained on average nine rings. The mean ring width showed within-tree and between-tree variability.
The chemical compositions of heartwood and sapwood were similar. Within-tree chemical variation occurred only in terms of
extractives, which increased from the pith (8.3%) to the heartwood-sapwood transition (12.7%) and decreased in the sapwood
(9.2%). Overall, the wood properties of teak from a unmanaged forest in East Timor were comparable to those reported for plantation
teaks of other origin: 607 kg/m3 basic density, 3.5% and 5.2% radial and tangential shrinkage, 141 N/mm2 modulus of rupture, 10684 N/mm2 modulus of elasticity, and 50 N/mm2 maximum crushing strength in compression parallel to the grain. Disturbances on individual tree growth arising from the unmanaged
status of the stand were evidenced by higher within-tree variability of ring width. However, the longitudinal and radial variations
of wood density and mechanical properties were of low magnitude and in a degree that did not negatively impact on timber quality. 相似文献
2.
The aim of this study is to characterise the properties of juvenile and mature heartwood of black locust (Robinia pseudoacacia L.). Content, composition and the subcellular distribution of heartwood extractives were studied in 14 old-growth trees from
forest sites in Germany and Hungary as well as in 16 younger trees of four clone types. Heartwood extractives (methanol and
acetone extraction) were analysed by HPLC-chromatography. UV microspectrophotometry was used to topochemically localise the
extractives in the cell walls. The natural durability of the juvenile and mature heartwood was analysed according to the European
standard EN 350-1. Growth as well as chemical analyses showed that, based on extractives content, the formation of juvenile
wood in black locust is restricted to the first 10–20 years of cambial growth. In mature heartwood, high contents of phenolic
compounds and flavonoids were present, localised in high concentrations in the cell walls and cell lumen of axial parenchyma
and vessels. In juvenile wood, the content of these extractives is significantly lower. Juvenile wood had a correspondingly
lower resistance to decay by Coniophora puteana (brown rot fungus) and Coriolus versicolor (white rot fungus) than mature heartwood. 相似文献
3.
《Wood material science & engineering》2013,8(4):242-244
Abstract This study assessed the decay resistance of Pinus leucodermis wood to the brown-rot fungus Coniophora puteana. Based upon the median weight losses of 30.65% for heartwood and of 34.68% for sapwood obtained in the biological tests, both the heartwood and sapwood material examined was classified as not durable (durability class 5) according to the CEN/TS 15083-1 classification. Total extractives were low, 3.93% in heartwood and 1.00% in sapwood, while lignin content was 22.60% and 25.41% in heartwood and sapwood, respectively. It is highly recommended to use protective treatments before using P. leucodermis wood in outdoor conditions. 相似文献
4.
Ahmed Mohareb Peter Sirmah Lyne Desharnais Stéphane Dumarçay Mathieu Pétrissans Philippe Gérardin 《Annals of Forest Science》2010,67(5):504-504
5.
《Wood material science & engineering》2013,8(1):50-52
Abstract The present work reports on the main physical and mechanical properties of Pinus leucodermis mature wood, one of the least studied coniferous species in south-east Europe. Pinus leucodermis heartwood specimens were found to have average density values of 0.73 g cm?3 at equilibrium moisture content of 11.5% and average density of 0.64 g cm?3 under oven-dry conditions. The overall tangential shrinkage was 3.4% and the radial shrinkage was 1.9%. The modulus of rupture was on average 77 N mm?2, while the static modulus of elasticity averaged 7087 N mm?2. The hardness of P. leucodermis heartwood using the modified Janka test was 33.4 N mm?2 in the transverse direction and 48.0 N mm?2 in the longitudinal direction, while its compression strength parallel to grain was approximately 41.6 N mm?2. 相似文献
6.
Thérèse Sergent Stéphane Kohnen Benoit Jourez Cécile Beauve Yves-Jacques Schneider Caroline Vincke 《Wood Science and Technology》2014,48(5):1005-1017
Robinia pseudoacacia L. heartwood is characterized by a very high natural durability. However, a significant difference was observed between the mature and juvenile heartwood, the latter presenting less durability against fungi decay, which could be attributed to lower extractive content. In order to elucidate this idea, extractives from mature and juvenile heartwoods of black locust trees were investigated. Results showed that extractive and phenolic contents were higher in mature than in juvenile heartwoods. The identification of phenolic compounds by UPLC–DAD–MS/MS revealed, for the first time, the presence of resveratrol and piceatannol. These two stilbenes as well as the flavonoid dihydrorobinetin were present at the highest level in mature heartwood, and as they are known antifungals, they could account for the great durability of mature heartwood. The stilbenes were detected in significant amounts particularly in mature heartwood where piceatannol reached a level tenfold higher than that reported for Japanese knotweed roots, the primary natural source of these stilbenes, whereas resveratrol level was comparable with reported values. As resveratrol and piceatannol receive increasing demand for nutraceutical, cosmetic and, possibly, pharmaceutical purposes, due to their beneficial health effects, this study underlines the use of R. pseudoacacia as a promising sustainable and economical source of resveratrol and piceatannol. 相似文献
7.
Helmut P. J. Gottwald 《Wood Science and Technology》1972,6(2):121-127
Summary Since the discovery of tyloses in the secondary xylem of angiosperms, their occurence has been noted only for vessels, although
parenchyma cells necessary for their formation are also associated with fibriform elements. Sporadic remarks about tyloses
in tracheids related to gymnosperm species, and the only observation on tyloses in angiosperm tracheids has been identified
as an error. An anatomical investigation of various magnoliaceous timbers has now demonstrated that a development of tyloses
in fibre-tracheids can also be regarded as a part of the normal transition from sapwood to heartwood in angiosperms. More
than half of the 22 species studied were characterized not only by tyloses in the vessels but also in the fibretracheids.
All the main genera with the exception of Liriodendron show the development of tyloses in the two different xylem elements. Distribution, frequency, and type of tyloses in the
fibretracheids are comparable with those in the vessels.—Further investigations on other species of Magnoliaceae are undertaken
in order to clarify possible anatomical relations regarding the development of tyloses. 相似文献
8.
The quantities of some extractives in the heartwood of 25 plus tree clones of Japanese cedar (Cryptomeria japonica) from two different sites were investigated to clarify the differences in antitermite properties in relation to clones and
environmental factors. The measured compounds were cubebol, epicubebol, sandaracopimarinol, and ferruginol. The total amounts
of extractives were calculated from gas chromatogram peak areas. The heartwoods from Tano (Tano Forest Research Station, Miyazaki
University; 31° N, 131° E, 130 m asl) tended to contain more of the individual extractives and total extractives than those
from Komenono (Komenono Forest Research Station, Ehime University; 33° N, 132° E, 700 m asl). There was a significant difference
(calculated by analysis of variance) at the 1% level among clones at both sites in quantities of total and individual extractives.
This result suggests that the qualities and quantities of heartwood extractives are largely affected by genetic factors. Spearman’s
rank correlation with the average of the extractive quantities at the sites was investigated. The correlation coefficients
of total extractives, cubebol, epicubebol, sandaracopimarinol, and ferruginol were 0.61, 0.85, 0.76, 0.67, and 0.74, respectively.
This result means that the order of the amounts of these compounds among the cultivars could be maintained at different sites.
It is apparent that both environmental and genetic factors affected the quantities of these extractives in the heartwoods
of Japanese cedar. 相似文献
9.
The variation in extractives content in sapwood and heartwood was investigated among 12 trees in each of four commercial plantations of Eucalyptus globulus in central Portugal. The study was carried out at the 15% height level and extractions used successively dichloromethane, ethanol and water. At all sites, heartwood had significantly more extractives than sapwood, on average 3.8 and 2.4%, respectively. Most extractives consisted of ethanol soluble material (on average 52% of total extractives). Among the sites, there was a statistically significant difference in the content of extractives but the most important source of variation was the within-tree variation between sapwood and heartwood. Differences in the content of extractives were also observed among trees. A strong relation between extractives content and heartwood proportion was found. The potential loss of pulp yield and problems associated with accumulation of extractives are directly related to the heartwood proportion in the eucalypt stems. Forest management should take into account heartwood development and selection for minimising heartwood extractives. 相似文献
10.
Ana Lourenço Isabel Baptista Jorge Gominho Helena Pereira 《Journal of Wood Science》2008,54(6):464-469
The pulping wood quality of Acacia melanoxylon was evaluated in relation to the presence of heartwood. The sapwood and heartwood from 20 trees from four sites in Portugal
were evaluated separately at 5% stem height level in terms of chemical composition and kraft pulping aptitude. Heartwood had
more extractives than sapwood ranging from 7.4% to 9.5% and from 4.0% to 4.2%, respectively, and with a heartwood-to-sapwood
ratio for extractives ranging from 1.9 to 2.3. The major component of heartwood extractives was made up of ethanol-soluble
compounds (70% of total extractives). Lignin content was similar in sapwood and heartwood (21.5% and 20.7%, respectively)
as well as the sugar composition. Site did not influence the chemical composition. Pulping heartwood differed from sapwood
in chemical and optical terms: lower values of pulp yield (53% vs 56% respectively), higher kappa number (11 vs. 7), and lower
brightness (28% vs 49%). Acacia melanoxylon wood showed an overall good pulping aptitude, but the presence of heartwood should be taken into account because it decreases
the raw-material quality for pulping. Heartwood content should therefore be considered as a quality variable when using A. melanoxylon wood in pulp industries 相似文献
11.
W. E. Hillis 《Wood Science and Technology》1971,5(4):272-289
Summary In the future, wood will be used largely for the manufacture of fibre products and particle board. The quality of wood used to meet increasing world demand will vary considerably. One feature of quality that can affect utilisation is the amount and type of wood extractives present. The distribution and variation in composition of extractives in the tree, as well as their effect on pulp manufacture, durability and surface films, are summarized. Methods to reduce the effects of some extractives in existing trees are described. Extractives can be reduced in plantation material by minimizing heartwood formation and by using silvicultural methods which result in small amounts of extractives being formed in this tissue. Current knowledge on heartwood formation is summarized.Paper presented to the 3rd Plenary Meeting of the International Academy of Wood Science held at the N. C. State University, Raleigh, March 11, 1971. 相似文献
12.
Eucalyptus globulus sapwood and heartwood were delignified at 130°, 150°, or 170°C by kraft pulping. Pulp yields of heartwood were lower than
those of sapwood (46.5% vs. 50.4% at 170°C). Delignification was modeled using consecutive and simultaneous kinetic models.
The modeling was similar for heartwood and sapwood, and either approach could be used, with both yielding good correlations
between experimental and model data. The consecutive model identified two delignification phases with similar reaction rates
and activation energies for heartwood and sapwood at 150° and 170°C. At 130°C only one phase was identified. Three reactive
types of lignin fractions were identified using the simultaneous model, without differences between heartwood and sapwood.
Their reaction rates were 0.152, 0.138, and 0.003 min−1 at 170°C, and the activation energies were 132, 119, and 102 kJ.mol−1. The presence of heartwood did not influence the kinetic development of delignification. The negative impact of heartwood
in pulping is related to the higher content of extractives (9.8% vs. 3.9% in heartwood and sapwood) and to their influence
on the process, namely in the heating-totemperature phase when a substantial mass loss occurs (30% vs. 20% for heartwood and
sapwood). 相似文献
13.
At present tapped wood of black pines (Pinus nigra var. austriaca) is mainly combusted. The priority of material use over thermal recycling has led to some considerations regarding the utilization of tapped wood. The high content of extractives suggests a higher natural durability, and therefore, the suitability for outdoor applications. Tapped and not tapped wood boards from black pine (sapwood and heartwood) were subjected to weathering tests to find out its resistance against abiotic stress. Additionally tapped wood particles with a high content of resin were exposed to weathering and to composting. Weathering caused roughness to increase. Infrared spectral characteristics revealed the differences before and after tapping and weathering. Principal component analyses supported the grouping according to the chemical changes. In heartwood the lignin band at 1510 cm??1 disappears and the typical resin band at 1688 cm??1 decreases considerably. The lignin band of resinous parts is affected neither by weathering nor by composting. However, the resin band shows an intensity decrease and broadening due to weathering and disappears during composting. 相似文献
14.
Yoshio Kijidani Noriko Sakai Keita Kimura Yoshitake Fujisawa Yuichiro Hiraoka Junji Matsumura Shinya Koga 《Journal of Wood Science》2012,58(6):471-478
Hinoki (Chamaecyparis obtusa) wood has been used as a structural material in Japan because of its superior mechanical properties, its excellent durability and the beautiful color of its heartwood. Variations of termite resistance and compositions of extractives among hinoki trees have been reported. However, genetic variation of termite resistance and the effect of heartwood color on termite resistance remain unknown. In this study, we report the characteristics of termite resistance and color indexes (L*, a* and b*) of heartwood of hinoki half-sib families in a progeny test stand. The survival days of termites and the mass loss of samples of hinoki heartwood differed significantly among hinoki families. Families with red-color heartwood had larger termite resistance than families with yellow-color heartwood. The termite resistances of individual samples from two families with yellow-color heartwood were as small as that of Pinus densiflora. Larger a* and smaller b* induced larger termite resistance of heartwood. The effect of DBH (diameter at breast height) of hinoki trees on termite resistance of hinoki families was small. 相似文献
15.
Nobumasa Bito Ryogo Nakada Eitaro Fukatsu Yasuyuki Matsushita Kazuhiko Fukushima Takanori Imai 《Annals of Forest Science》2011,68(6):1049-1056
• Introduction
In Cryptomeria japonica, heartwood properties are considered to be affected by specific extractives. It remains unclear whether traits of specific heartwood compounds are under genetic control. 相似文献16.
Chuanshuang Hu Guifen Jiang Min Xiao Jianhui Zhou Zhao Yi 《Journal of Wood Science》2012,58(5):465-469
Merbau is widely used for indoor finishing, outdoor constructions, and furniture. However, it has a disadvantage in some applications in that part of its extractives is water-soluble and can be readily leached out to stain adjacent materials. This study examined whether heat treatment could overcome the above-mentioned problem. Effects of the treatment temperature and time on water-soluble extractives and color changes of merbau heartwood were studied. CIELAB ΔL *, Δa *,Δb *, and ΔE * parameters and absorbance spectra were used to evaluate color change and water-soluble extractive solutions, respectively. The results show that heat treatment is an efficient technique to overcome the problem caused by water-soluble extractives of merbau heartwood. Surface color of the treated samples tends to become darker and color of the extractive solution becomes fading to transparent when the treatment temperature and time increased. The absorbance of UV light decreases in intensity and the dominant absorption peak appears around 350 nm when the treatment temperature and time increase. The optimized parameters of treatment temperature and time are 170 °C and 4 h. Modulus of rupture and modulus of elasticity of the heat treated samples under the optimized parameters decrease by 29.6 and 12.9 %, respectively, compared with those of the untreated samples. 相似文献
17.
Summary The influence of pre-steaming on the drying rate, wood anatomy and shrinkage of regrowth Eucalyptus pilularis (blackbutt) was determined. Pre-steaming increased the drying rate by 7–16%. This resulted from a mobilisation and partial removal of heartwood extractives, probably allowing greater access of water molecules to cell walls, and therefore increased radial and tangential diffusion. Longitudinal permeability is unlikely to be significantly increased by pre-steaming, as tyloses appeared unaltered. Volumetric shrinkage was unchanged.The authors wish to thank K. W. Groves of the Department of Forestry, Australian National University for his comments, J. F. Marchant and R. Colley for technical assistance, and P. Lind for some of the statistical analyses. The New South Wales Timber Advisory Council Ltd provided financial support. The work reported in this paper formed part of a post-graduate research programme undertaken by the senior author at the Department of Forestry, Australian National University 相似文献
18.
Iris Brémaud Nadine Amusant Kazuya Minato Joseph Gril Bernard Thibaut 《Wood Science and Technology》2011,45(3):461-472
Extractives can affect the vibrational properties tanδ (damping coefficient) and E′/ρ (specific Young’s modulus), but this
is highly dependent on species, compounds, and cellular locations. This paper investigates such effects for African Padauk
(Pterocarpus soyauxii Taub.), a tropical hardwood with high extractives content and a preferred material for xylophones. Five groups of 26 heartwood
specimens with large, yet comparable, ranges in vibrational properties were extracted in different solvents. Changes in vibrational
properties were set against yields of extracts and evaluation of their cellular location. Methanol (ME) reached most of the
compounds (13%), located about half in lumen and half in cell-wall. Water solubility was extremely low. tanδ and E′/ρ were
very strongly related (R
2 ≥ 0.93), but native wood had abnormally low values of tanδ, while extraction shifted this relation towards higher tanδ values.
ME extracted heartwood became in agreement with the average of many species, and close to sapwood. Extractions increased tanδ
as much as 60%, irrespective of minute moisture changes or initial properties. Apparent E′/ρ was barely changed (+2% to −4%)
but, after correcting the mass contribution of extracts, it was in fact slightly reduced (down to −10% for high E′/ρ), and
increasingly so for specimens with low initial values of E′/ρ. 相似文献
19.
Focussing on four types of parenchyma cell around pith regions of branches of Robinia pseudoacacia L. var. inermis, we examined the timing and role of cell death during heartwood formation. Large parenchyma cells that were located in the
inner part of the pith died within a year. By contrast, other parenchyma cells died within 4 years, with the timing of cell
death depending on the type of cell. Axial parenchyma cells of the xylem close to the pith died first. Then, small parenchyma
cells died in the perimedullary zone in the outer part of the pith. Finally, ray parenchyma cells in the xylem close to the
pith died. Variations in the autofluorescence of cell walls, which might have been due to deposition of heartwood substances,
were observed first in xylem ray parenchyma cells and small parenchyma cells in the perimedullary zone. Our results indicate
that the initiation of heartwood formation occurs within 4 years in pith regions of branches in Robinia pseudoacacia L. var. inermis. Moreover, it appears that not only xylem ray parenchyma cells but also small parenchyma cells in the perimedullary zone
might be involved in the synthesis of heartwood substances. 相似文献
20.
《Wood material science & engineering》2013,8(3-4):83-93
Abstract Differences in durability between heartwood and sapwood of Norway spruce [Picea abies (L.) Karst.] were investigated to determine wood qualities most favourable for use in outdoor constructions above ground. Trees grown on sites with either good or poor access to water were used. Seventy-eight specimens measuring 20 × 50 × 300?mm3 separated into heartwood and sapwood, half untreated, half painted, were exposed horizontally outdoors above ground for 5.5?years with the pith side up and the bark side down. Crack length and crack number were measured. Fungus growth and surface changes were visually estimated. Fungus type was determined by microscopic analysis. The main finding was that spruce heartwood had fewer and shorter cracks and less surface-discolouring fungus growth than sapwood. This was valid for both painted and untreated wood. After 2?years’ exposure, the cracks in sapwood (upper surface) were more than three times longer and about five times more numerous than in heartwood for both painted and untreated boards. Microscopic study showed that surface discoloration was due mainly to Aureobasidium pullulans, together with a few other discolouring fungi. After 5.5?years, initial decay was established on the surface and in the end grain of four untreated test objects. 相似文献