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1.
Jan H. Blohm Eckhard Melcher Marie T. Lenz Gerald Koch Uwe Schmitt 《Wood material science & engineering》2014,9(3):186-191
AbstractThe natural durability of timber is an important property in order to assess its performance in service. For numerous species grown in primary forests, this property has already been determined. As plantation-grown timber becomes more and more important, detailed information on its properties is needed, because increasing amounts of this material are coming to the market. The majority of planted Douglas fir (Pseudotsuga menziesii [Mirb.] Franco) in Germany is around 40 years old. In the present study, representative material of totally ten trees from two different sites in the south of Germany was investigated with regard to natural durability. In laboratory tests based on European standard DIN EN 350-1, inner and outer heartwood zones were exposed to basidiomycetes. Density measurements were additionally used for further characterisation of this material. Results showed a lower durability of the plantation-grown Douglas fir wood as compared with wood from natural sites. Significant differences for both durability and density were found between inner and outer heartwood, even though no correlation between the parameters was recognised. Data illustrate that for a better understanding of durability variations, chemical, topochemical and electron microscopic studies are needed. 相似文献
2.
《Wood material science & engineering》2013,8(3-4):204-210
Abstract Untreated Scots pine (Pinus sylvestris) and Norway spruce (Picea abies) samples were exposed above ground in a durability test for 6 years. The samples consisted of three pieces of wood, 22×95×500 mm, screwed together; two pieces lengthwise with a third piece overlapping. Weight was measured, to calculate moisture content (MC), and samples checked regularly for cracks and fungal growth. Parameters investigated were heartwood/sapwood (pine), annual ring orientation (spruce), stand site, annual ring width and density. Stand site, annual ring width and density had no influence on MC or fungal growth for either pine or spruce. Spruce samples with vertical annual rings had fewer cracks than samples with horizontal annual rings. Pine sapwood samples had a high MC and a large amount of rot fungi, while heartwood had a lower MC and no rot. Most spruce samples were similar to pine heartwood, except from a few samples that had high MC and fungal growth. Those were all sawn from the outer part of the log. Therefore, it can be stated that spruce sawn from the inner part has almost the same properties as pine heartwood, while spruce from the outer part of the log has similar properties to pine sapwood. 相似文献
3.
[目的]通过测定和分析广西融水种源红心杉木优树材质性状指标,以了解该地区红心杉木材性状变异规律。[方法]以广西融水种源60株20年生的红心杉木优树为研究材料,测定单株材积、红心率、基本密度、组织比量、管胞性状、微纤丝角等10个材质性状指标,分析各材性性状指标分布和变异规律及性状间的相关关系。[结果]表明:红心率、基本密度、木射线比量、管胞比量、管胞长、管胞宽、管胞长宽比等性状数据分布服从正态分布。融水两个地区红心杉优树轴向薄壁细胞比量的变异系数分别为35.08%和44.97%,变异较大。管胞比量变异系数分别为3.28%和3.56%,变异较小。红心率、木射线比量、管胞长、管胞宽、微纤丝角等性状差异极显著(P0.01),轴向薄壁细胞比量差异显著(P0.05)。10个材质性状间存在12对表型显著相关。[结论]测定的10个性状均是连续性数量性状。早、晚材的管胞长度、管胞宽度和管胞长宽比等性状数据呈从心材至边材逐渐增加的规律。作为重要经济性状的红心率与木射线比量呈极显著正相关(P0.01),单株材积与轴向薄壁细胞比量呈显著正相关(P0.05),而单株材积与基本密度的相关性不显著,这使红心杉木生长量与材性相结合的遗传改良成为可能。 相似文献
4.
《Scandinavian Journal of Forest Research》2012,27(1):88-96
The aim of the study was to investigate the possibility of strength grading Norway spruce [Picea abies (L.) Karst.] saw logs on the basis of simulated X-ray LogScanner measurements and to evaluate the potential accuracy of X-ray LogScanner measurements of green heartwood density and percentage of heartwood. The study was based on 272 logs for strength grading and 29 logs for measurements of green heartwood density and percentage of heartwood. The logs were scanned using computed tomography (CT). After sawing, the modulus of elasticity (MOE) of the centre boards was measured using a strength-grading machine. The CT images were used for simulations of an X-ray LogScanner, resulting in simulated measurements of different variables such as diameter, taper, percentage of heartwood, density and density variations. Multivariate models for prediction of MOE were then calibrated using partial least squares (PLS) regression. The MOE of a log was defined as the mean value of the MOE of the two centre boards. The study showed that the simulated X-ray LogScanner measured the percentage of heartwood and green heartwood density with relatively high accuracy (R 2 = 0.94 and R 2 = 0.73, respectively, after removing two outliers) and that these and other variables measured by the simulated X-ray LogScanner could be used to predict the stiffness of the centre boards. These predictions were used to sort the logs according to the predicted MOE. When sorting out 50% of the logs (''high-strength'' logs), the percentage of C30 boards increased from 73% (all logs in the study) to 100% (only ''high-strength'' logs). The rest of the logs could then be divided into two groups, one of them with 100% C24 and C30 boards. 相似文献
5.
There are indications that the drying process may have negative effects on the natural durability of wood. The impact of various
drying processes on the durability of Scots pine lumber has been evaluated with mass loss in a decay test with brown rot fungus,
Coniophora puteana, as measure of the decay resistance of sapwood and inner and outer heartwood. Drying with or without steam conditioning was
performed in six different series: air drying, kiln drying at temperature ranges commonly used in Swedish sawmills at 70°C
and 90°C with two different regulation principles, and one high-temperature drying at 110°C. Durability varied considerably
both between and within boards. Sapwood showed considerable less durability than heartwood. No difference in durability was
found between inner heartwood and outer heartwood. Air-dried heartwood showed the highest durability compared to other drying
series. The lowest durability in sapwood and heartwood was found for series dried at the 90°C temperature level with high
material temperature early in drying. The interpretation is that the duration of high material temperature at high moisture
content (MC) is the critical combination for decay resistance in heartwood. Steam conditioning after drying decreased durability
in sapwood. 相似文献
6.
Rubidium solution was injected in the sapwood of a Japanese cedar cultivar in the growing period, and its radial movement
in stem was traced to investigate the accumulation of alkali metals in the heartwood. Sapwood-injected Rb was detected in
outer heartwood at 10 days after the treatment, and continued increasing at 20 days after. Radial movement of Rb toward heartwood
was considered to occur soon after the treatment, and to decline at a certain point of the time after Rb injection ceased.
However, Rb continued moving in heartwood probably by diffusion even after the cease of Rb injection. In a series of injection
experiment, radial movement of injected Rb is not corresponding to the seasonality of both cambial activity and cytological
changes of ray parenchyma accompanied with heartwood formation. From the results on Rb’s behavior, we conclude that accumulation
of K and other alkali metals in heartwood of Japanese cedar has two steps, active transport from sapwood to outer heartwood
via ray, and diffusion in heartwood, and that these processes proceed independently from both cambial activity and cytological
changes of ray parenchyma. 相似文献
7.
We evaluated heartwood, sapwood and bark content in teak trees. A total of 27 sample plots were laid out in teak plantations raised by State Forest Department in Karnataka covering different age groups... 相似文献
8.
Two activable tracers, Rb and Eu, were injected into the sapwood of Japanese cedars (Cryptomeria japonica D. Don) to investigate the radial movement of minerals in their stems in the resting period. Eight trees of four cultivars,
two of which genetically form wet heartwood, were treated near the end of the growing period. At 40 days after the treatment,
Rb was detected in the outer heartwood, whereas Eu was not. Radial movement of Rb was more rapid in trees with wet heartwood
than in those with normal heartwood. At 204 days after the treatment, more Rb was detected in the heartwood than was found
on the first sampling, whereas no Eu was detected in the heartwood. The difference in radial movement between Rb and Eu was
considered mainly to be the result of selective transport of beneficial minerals by Japanese cedar. The difference in the
rate of radial movement of Rb between wet and normal heartwood became more conspicuous at 204 days after treatment. We concluded
that the movement of Rb from the sapwood to the outer heartwood was by active transport through the rays, whereas that in
the heartwood was by diffusion due to the gradient of Rb concentration. 相似文献
9.
The influence of rate of growth on the density and heartwood extractives content of eucalypt species
J. Wilkes 《Wood Science and Technology》1984,18(2):113-120
Summary Basic density and extractives content, of the sapwood and outer heartwood respectively, were compared for a fast-and a slow-grown tree in five, 40 year old, coppice clumps of each of six eucalypt species. Rate of growth did not appreciably influence extracted wood density, although outer heartwood extractives levels were significantly (P<0.05) higher in the larger stems. The juvenile core, as defined by radial variation in basic density, occupied a similar proportion of the tree diameter in the fast-and slow-grown trees, suggesting that sampling was effected in tissues of similar maturity in both tree groups.Helpful discussions with Dr. W. A. Heather, a co-worker, and Dr. W. E. Hillis, Visiting Fellow of this Department, are gratefully acknowledged 相似文献
10.
《Wood material science & engineering》2013,8(4):177-184
Abstract Mechanical properties are very important in structural uses of wood. In the case of larch wood, shear strength (SS) may be a limiting property, because the wood is brittle and it splinters easily. In this study, SS of Siberian larch (Larix sibirica) wood was studied in relation to its axial and radial location and to some other wood properties in the part of the trunk that produces logs of good carpentry quality. SS increased by 21–23% from the pith to the outer heartwood at each studied height (butt, 4.5 and 9 m), and it was at its most approximately 7% higher at the butt than at the other studied heights. The main reason for the radial increase in SS was the increase in density caused by wood maturation, but other factors also affected SS, depending on the grouping mode (combined material, radial/axial location). An exception was sapwood, for which no factors affecting SS could be identified. Thus, sapwood may behave differently from heartwood regarding use, even unexpectedly. The results suggest that mature heartwood, but not juvenile wood and sapwood, of Larix sibirica should primarily be used in products that require high SS. 相似文献
11.
Binderless particleboards were manufactured from sugi (Cryptomeria japonica D. Don) heartwood and sapwood by hot-pressing (pressure: 5 MPa; temperatures: 180°, 200°, and 220°C; times: 10, 20, and 30
min), and the board properties [internal bonding (IB), thickness swelling (TS), water absorption (WA)] were investigated to
evaluate the self-bonding ability. The IB, TS, and WA of the boards from sugi heartwood were better than those of the boards
from sugi sapwood at any hot-pressing condition. Therefore, it was suggested that the self-bonding ability of sugi heartwood
was superior to that of sugi sapwood. Then, sugi heartwood and sapwood powder with grain size 10 βm were used as a binder
for plywoods. Four kinds of plywood were manufactured from the combination of powder and veneer, both of which were prepared
from sugi heartwood and sapwood under the same hot-pressing conditions as the binderless particleboard, and the adhesive shear
strength and wood failure of the plywood were investigated. As a result, the plywood composed of sugi heartwood veneer met
the second grade of JAS for plywood, when either powder was used as a binder, when they were pressed at 200°C for 20–30 min
and 220°C for 10 min. 相似文献
12.
《Wood material science & engineering》2013,8(2):139-144
Abstract The heartwood and sapwood from Scots pine (PS), Norway spruce (PA), and Oriental spruce (PO) were tested for susceptibility to discoloring fungi and water uptake. In addition, annual ring width and density were measured. The methods used were Mycologg for testing growth of fungi and a modified version of EN 927-5 to investigate water uptake. For pine, the heartwood showed a lower water uptake and no discoloring fungi growing in the tests. The heartwood had a significantly higher density and smaller annual ring width than the sapwood. In PA the heartwood had significantly lower discoloration than sapwood. The total water uptake in g/m2 was significantly higher in sapwood, but not the calculated moisture content. As for wood properties, the density was significantly higher in sapwood compared to heartwood, although there were no differences in annual ring width. Regarding PO, differences in water uptake could be seen between sapwood and heartwood although the densities were similar. These results show that susceptibility to discoloring fungi and water uptake is hard to correlate to a single inherent property when looking at different wood species. 相似文献
13.
Mohammad Derikvand Nathan Kotlarewski Michael Lee Hui Jiao Gregory Nolan 《Wood material science & engineering》2020,15(3):172-181
ABSTRACTThe main goal of this study was to investigate the visual characteristics, recovery rate, and flexural properties of sawn boards from a fibre-managed plantation Eucalyptus globulus resource as a potential raw material for structural building applications. The impacts of the visual characteristics, strength-reducing features, and variation in basic density and moisture content on the bending modulus of elasticity (MOE) and modulus of rupture (MOR) of the boards were investigated. The reliabilities of different non-destructive methods in predicting MOE and MOR of the boards were evaluated, including log acoustic wave velocity measurement and numerical modellings. The MOE and MOR of the boards were significantly affected by the slope of grain, percentage of clear wood, and total number of knots in the loading zone of the boards. The normal variation in basic density significantly influenced the MOE of the boards while its effect on the MOR was insignificant. The numerical models developed using the artificial neural network (ANN) showed better accuracies in predicting the MOE and MOR of the boards than traditional multi-regression modelling and log acoustic wave velocity measurement. The ANN models developed in this study showed more than 78.5% and 79.9% success in predicting the adjusted MOE and MOR of the boards, respectively. 相似文献
14.
《Scandinavian Journal of Forest Research》2012,27(4):330-350
To study and model the variation of wood properties, sample trees were selected from 42 Norway spruce and 20 Scots pine stands covering a wide variation in climatic and site conditions, stand maturation and tree sizes. Plot and tree measurements were followed by sampling wood from different heights in each sample tree and laboratory measurements of wood properties. Mixed linear and non-linear prediction models were developed using diameters, number of annual rings and climatic indices as explanatory variables. The variation in spruce properties explained by these variables was: basic density 50%, latewood content 52%, juvenile wood diameter 85%, heartwood diameter 94% and bark thickness 76%. The corresponding values for pine were 59, 54, 79, 92 and 85%. Random among-tree variance was an important contributor to the remaining variation for density and latewood. In general, only a minor part of the random variation was related to variance between stands. Predictions derived from the models for density and juvenile wood in both species, and heartwood in pine showed good agreement when validated with data sets from two other studies. The resulting models may be used for predicting wood properties in forest planning and in bucking computers in harvesters, provided that the essential information is available. 相似文献
15.
Kana Yamashita Yasuhiko Hirakawa Shuetsu Saito Hiroshi Nakatani Motoyoshi Ikeda Masamitsu Ohta 《Journal of Wood Science》2012,58(3):259-266
To investigate the factors affecting the surface-check variation in boxed-heart square timber of sugi (Cryptomeria japonica), surface checks formed by the conventional kiln drying were compared for two stem heights of five cultivars with different wood properties. The total length and average length of the surface checks were greater at the upper part of the stems for all the cultivars. This might be caused by more sapwood at the upper part of the stem, and large drying stresses between the outer sapwood and the inner heartwood. The cultivars, in which tangential shrinkage was large owing to small microfibril angle, formed longer surface checks and smaller bow. There was a positive relationship between surface-check length and tangential shrinkage. The heartwood percentage and tangential shrinkage were thought to be important factors affecting the surface-check variation in sugi boxed-heart square timber. 相似文献
16.
17.
Understanding the green moisture content and wood density is important for effective forest management. Radial distribution
patterns in the green moisture content (MC) and basic density (BD) in stems of red cypress (Chamaecyparis formosensis) were investigated in 69 plantation trees that were 46 years old. An increment core was collected from each sample tree at
breast height (1.3 m). Five radial positions were defined: pith piece (Pith), inner heartwood (IHW), outer heartwood (OHW),
intermediate wood (TSH), and sapwood (SW). Results showed that the average MC was highly dependent on the individual tree. Average values of the MC obtained from the TSH were significantly lower than those for the other positions. The MC of heartwood was higher than that of SW. Distribution patterns of the MC in the radial direction varied among trees. Radial variations in MC and BD were greater than in between-tree variations. Six types of radial distribution patterns of MC were detected for sample trees. MC values increased with decreasing BD (except for the TSH). Positive correlations were found between adjacent sampling positions in both MC and BD. 相似文献
18.
采用高频真空干燥、常规窑干和高温干燥3种方法对杉木人工林木材的心、边板材进行干燥处理,用毛细管上升法评价干燥后试样的浸注性能,用半薄切片法测定干燥试样具缘纹孔的闭塞率,最后用扫描电子显微镜观察干燥试样微观构造的变化,比较分析3种干燥方法对杉木人工林木材浸注性的影响机理.结果表明:对于杉木边材,经高频真空干燥后试样的浸注性显著高于常规干燥和高温干燥后试样的浸注性,后2种干燥方法对试样浸注性影响的差异并不显著;对于杉木心材,高频真空干燥与高温干燥后试样的浸注性存在显著差异,而高频真空干燥与常规干燥之间、高温干燥与常规干燥之间对试样浸注性的影响差异均不显著;3种干燥方法处理后,杉木边材的浸注性均显著高于心材的浸注性;具缘纹孔的闭塞率较低以及部分具缘纹孔周缘破裂是高频真空干燥后木材浸注性提高的主要原因. 相似文献
19.
Heartwood, sapwood, and inner and outer bark of Port Orford cedar were extracted with methanol, and the extracts evaluated
for antioxidant activity. The total phenol content (TPC) of the extracts was determined by the Folin-Ciocalteu method and
expressed as gallic acid equivalent (GAE). Butylated hydroxytoluene was used as a positive control in the free-radical-scavenging
activity tests and ethylenediaminetetraacetic acid dihydrate disodium salt served as a positive control in the metal-chelating
activity assay. All wood extracts showed significant freeradical-scavenging activity. In the radical-scavenging assay of 2,2-azino-bis
(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (the ABTS assay), the inner bark extracts exhibited the strongest
free-radical-scavenging activity. The 50% inhibitory concentrations (IC50) in the radical-scavenging assay against 1,1-diphenyl-2-picrylhydrazyl hydrate radical (DPPH) of the heartwood, sapwood,
and inner and outer bark extracts were 64.77, 29.03, 10.31, 19.87 μg·ml−1, respectively. In the metal-chelating activity system, the sapwood extract demonstrated significant activity. The greatest
TPC, 537.5 mg GAE/g dry extract, was detected in the inner bark. The lowest TPC of 136.9 mg GAE/g dry extract was observed
in the heartwood dry extract. The results indicate that the antioxidant activities of the extracts are in accordance with
the amounts of phenolics present; the inner and outer barks of Port Orford cedar are rich in phenolics and may provide good
sources of antioxidants. 相似文献
20.
Binderless particleboards were manufactured from sugarcane (Saccharum officinarum L.) bagasse by steam-injection pressing and by using hot pressing as a reference method. The inner layer (core/pith) and
the outer hard fibrous layer (face/rind) of bagasse were used as raw materials. The effects of bagasse type, manufacturing
process, and storage method on the mechanical properties of binderless particleboards were investigated. The results showed
that the bagasse pith particles provided better board properties than bagasse rind particles. It seemed that bagasse pith
particles were more easily deformed than bagasse rind particles, enlarging the bonding contact area. The severe conditions
of steam-injection pressing caused delamination on the bagasse pith binderless boards with densities of 0.6 g/cm3 or higher, and gave poor bonding quality. However, steam-pressed boards showed relatively higher board properties than hot-pressed
boards. The storage method of sugarcane bagasse affected the chemical composition and the board properties. It was shown that
the extent of self-bonding formation depends on the chemical and morphological properties of lignocellulosic materials, as
well as on the manufacturing conditions.
Part of this paper was presented at the 5th International Wood Science Symposium, Kyoto, Japan, September 2004 相似文献