Relationship between radial variations in shrinkage and drying defects of tree disks

This study was conducted to investigate the relationship between radial variations in shrinkage and drying behavior of larch disks during radio-frequency/vacuum (RF/V) drying. Despite considerable variations in shrinkage both within and between logs, some trends were observable for each log. Actual radial shrinkage was much larger than free radial shrinkage with a ratio of tangential shrinkage ( _T) to radial shrinkage ( _R) ranging from 1.27 to 1.62. If the _T/ _R ratio of larch was about 2.5, the relative displacement was theoretically estimated to be 1.6 to 1.65, showing good agreement with the experimental results. The results showed that the formation of V-cracking was closely related to the actual differential shrinkage, which is the difference between the estimated tangential shrinkage and actual radial shrinkage after drying.     

Effect of compressive load on the dimensional changes of the Japanese larch dried in a radio-frequency/vacuum drier

This study investigated the effect of a compressive load of 0.092 MPa on the dimensional changes of Japanese larch in a humidity chamber after continuous radio-frequency/vacuum drying. The dimensional changes in the loading directions were significantly increased while those perpendicular to the loading directions were decreased. The shrinkages showed higher values in continuous drying than in intermittent drying. For the specimens loaded on their tangential sections, the radial shrinkages were even higher than the tangential shrinkages; thus, the tangential/radial shrinkage ratio was decreased by 0.27. The transverse hygroscopicity was reduced for the specimens loaded on their cross sections, but increased for the specimens loaded on their tangential sections.     

大花序桉种源间木材物理性质变异研究

以广西东门林场18年生的11个大花序桉(Eucalyptus cloeziana)种源木材为研究对象,对它们的木材基本密度、弦向干缩率、径向干缩率等物理性质进行了测定分析,发现不同种源间、相同种源不同树干高度间所测定的物理性质指标均存在显著的差异。木材基本密度最大的种源是B85,然后依次是D47、B82,其值分别是0.7530、0.7386、0.7274 g/cm3;参试的11个种源中有8个种源的差异干缩都小于1.5,属于差异干缩小的类型;只有14425、12195和B55这3个种源的差异干缩超过1.5,但小于1.6,属于差异干缩中等类型;种源的树高、胸径生长性状与木材基本密度、差异干缩、体积全干缩率物理性状相关关系不密切,据此分别对树高、胸径等生长性状和木材基本密度、干缩率等木材物理性状进行独立选择可望获得较好的生长、物理性状改良效果。     

Shrinkage properties of second-growth southern yellow pine

Summary Several factors which may affect the shrinkage of wood had been studied using loblolly pine (Pinus taeda L.). It was observed that volumetric, tangential and radial shrinkages decreased as the height increased. Longitudinal shrinkage increased with height. Only tangential shrinkage was significantly affected by the distance from the pith factor. All shrinkages were found to vary significantly according to cardinal directions. For the trees studied, lower volumetric, tangential and radial shrinkages were observed for specimens from the south side of the pith. Longitudinal shrinkage was noticeably higher in this direction.Although shrinkage of wood for any given specific gravity was found to vary somewhat with trees, it was, in general, significantly affected by specific gravity. Volumetric, tangential and radial shrinkages increased with increasing specific gravity. The opposite was true for longitudinal shrinkage. According to regression equations derived from this study, tangential, radial and longitudinal shrinkage values were not zero but 2.79–3.45, and 0.526 percent, respectively, at zero specific gravity. Above 0.72 specific gravity, radial shrinkage of the species studied was found to be greater than tangential shrinkage.The effect of growth rate (number of rings per inch) on shrinkage was found to be insignificant.

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Zusammenfassung Verschiedene, die Schwindung beeinflussende Faktoren wurden an Holz von Loblolly pine (Pinus taeda L.) untersucht. Es wurde festgestellt, daß die Volumenschwindung, die tangentiale und die radiale Schwindung mit zunehmender Höhenlage der Proben im Stamm abnahmen, während die Längsschwindung größer wurde. Nur die tangentiale Schwindung wurde deutlich vom Abstand der Probe von der Markröhre beeinflußt. Es zeigte sich ferner, daß alle Schwindungswerte in Abhängigkeit von den Himmelsrichtungen beträchtlich schwankten. Bei den untersuchten Bäumen waren die Volumenschwindung, die tangentiale und die radiale Schwindung von Probestücken aus dem nach Süden liegenden Stammteil geringer, wogegen die Längsschwindung in dieser Richtung merklich größer war.Trotz gewisser Schwankungen von Stamm zu Stamm erwies sich die Schwindung deutlich von der Dichte abhängig. Die Volumenschwindung, die tangentiale und radiale Schwindung nahmen mit zunehmender Dichte ebenfalls zu, wohingegen die Längsschwindung abnahm. Die mit den erhaltenen Werten aufgestellten Regressionsgleichungen ergaben für die Tangential-, Radial- und Längsschwindung bei einer Dichte von 0 nicht ebenfalls 0, sondern 2,79%,-3,45% und 0,527%. Für Dichten über 0,72% wurde die radiale Schwindung der untersuchten Proben größer als die tangentiale.Die Wachstumsgeschwindigkeit (Anzahl der Jahrringe pro cm) hatte keinen signifikanten Einfluß auf die Schwindung.

     

长江滩地杨木密度和干缩性的研究

对安庆段长江滩地I-72杨的密度和干缩性进行了研究。结果表明:I-72杨的气干密度、全干密度和基本密度分别为0.454 g/cm3、0.415 g/cm3和0.364 g/cm3;I-72杨木材密度的径向变异为自髓心向外,最初递减,然后再向外层递增;轴向变异为沿树干向上逐渐增加;I-72杨的径向、弦向和体积全干缩率分别为3.917%、8.093%和12.138%,体积干缩系数为0.169,差异干缩为2.107;I-72杨5.3 m高度处的径向、弦向和体积全干缩率测量值均大于1.3 m高度处的测量值。     

Transverse shrinkage variations within tree stems of <Emphasis Type="Italic">Melia azedarach</Emphasis> planted in northern Vietnam

This study quantified variations within tree stems in tangential shrinkage (α_T), radial shrinkage (α_R), and tangential/radial shrinkage ratio (α_T/α_R) of Melia azedarach grown in two different sites in northern Vietnam. The overall values of α_T, α_R, and α_T/α_R were 7.05%, 4.38%, and 1.64, respectively. The variation pattern in α_T and α_R was found to increase gradually from pith to bark and this trend was similar on both sites. In radial direction, the α_T/α_R decreased significantly from 10 to 50% of the radial length from pith before approaching a constant value toward the outside. The transverse shrinkage variation with height was very small and without statistical significance. There were strong positive relationships between transverse shrinkage and basic density (BD). This implies that the selection for high wood density may lead to increase wood transverse shrinkage. In addition, the α_T and α_R had significant positive linear relationships with both acoustic wave velocity (V_L) and dynamic modulus of elasticity of log (DMOE_log). This result suggests that it might be possible to sort lumber with large transverse shrinkage by stress wave method for M. azedarach planted in northern Vietnam.     

Tangential and radial shrinkage variation within trees in sugi (<Emphasis Type="Italic">Cryptomeria japonica</Emphasis>) cultivars

The transverse shrinkage variation within trees was examined for five sugi cultivars. The within-tree trends of tangential shrinkage (α _T) were different by cultivar, whereas radial shrinkage (α _R) increased from pith to bark in most cultivars. The tangential/radial shrinkage ratio (α _T/α _R) decreased from pith to bark in most cultivars, because the radial variation of α _R was larger than that of α _T. The cultivars showed significant differences among cultivars in α _T, α _R, and α _T/α _R, but the difference among cultivars for α _T/α _R was smaller. The relationships between transverse shrinkage and microfi bril angle (MFA), basic density (BD), tree ring parameters, and modulus of elasticity were examined. The α _T and α _R showed positive relationships with BD, latewood percentage, latewood density, and modulus of elasticity, and negative relationships with MFA and ring width. The relationships with earlywood density were weak. Sugi exhibited variation in transverse shrinkage within stem and among cultivars, with the variation affected by MFA, density, and tree ring parameters. Part of this article was presented at the 56th Annual Meeting of the Japan Wood Research Society, Akita, Japan, August 2006, and the 57th Annual Meeting of the Japan Wood Research Society, Hiroshima, Japan, August 2007     

Early prediction of basic density, shrinking, presence of growth stress, and dynamic elastic modulus based on the morphological tree parameters of Tectona grandis

Significant efforts have been made to improve teak; however, evaluation in juvenile step is limited. The objective of this study was to conduct an early assessment of the wood properties of 4-year-old Tectona grandis. Samples of 36 clones were collected to determine their morphological tree parameters [diameter a breast height (DBH), diameter of the second log, tree height, and log quality]. Presence of growth stress, heartwood percentage, shrinkage (radial, tangential, and volumetric), basic density, and ultrasound velocity (USV) were determined for standing trees, logs, green lumber, and dry lumber. The results indicate that DBH and USV in standing trees can be used to predict elastic module (ED), mainly ED of the standing tree and dry lumber, as well as the possible presence of growth stress. Additionally, growth stress can be predicted by UVS in standing tree. Tangential and volumetric shrinkage were not predicted by tree morphology, but radial shrinkage was predicted by diameter and UVS was not affected by any shrinkage. Basic density was predicted by DBH and UVS measured in log.     

Use of wood shrinkage characteristics in breeding of fast-grown Acacia auriculiformis A. Cunn. ex Benth in Vietnam

u| li]? Genotypic variation in wood total and partial shrinkage, basic density and growth traits was estimated in 51÷2 year old Acacia auriculiformis trees in a clonal test. li]? In the tangential, radial and longitudinal directions, the mean values were 2.64%, 1.64% and 0.77% for partial shrinkage, and 5.92%, 3.23%, and 0.96% for total shrinkage, respectively. Total and partial transverse shrinkage were significantly greater in sapwood than in heartwood. li]? Clonal repeatability (H _C ² ) estimates for partial shrinkage were lower than those for total shrinkage, and heartwood shrinkages had lower H _C ² than those for sapwood. Estimates of H _C ² were from 0.32 to 0.38 for total transverse shrinkage, comparable to H _C ² for both total and partial volumetric shrinkages (0.40 and 0.32, respectively). However, H _C ² for longitudinal shrinkages, total and partial coefficients of anisotropy were only from 0.09 to 0.18. li]? The genotypic coefficients of variation of all shrinkage traits varied from 5.45% to 8.02%. Total shrinkage was strongly positively correlated with partial shrinkage in each dimension. Genotypic correlations were not significant between shrinkage and growth traits or density. Strong and significant correlations between transverse shrinkage in heartwood and sapwood (0.87) indicated that juvenile shrinkage is a good genetic indicator of this trait in older trees. Utilisation du retrait du bois dans l’amélioration de l’Acacia auriculiformis A. Cunn. ex Benth à croissance rapide au Vietnam.     

Relationships of anatomical characteristics versus shrinkage and collapse properties in plantation-grown eucalypt wood from China

To explore the influence of the basic density on collapse-type shrinkage properties and to quantify the relationships of the main anatomical features with shrinkage and collapse properties, all above-mentioned parameters were determined and analyzed for three species of collapse-susceptible eucalypts, Eucalyptus urophylla, Eucalyptus grandis, and E. urophylla × E. grandis, planted in South China. The correlation coefficients were also determined and the corresponding regression equations were established with the anatomical parameters measured by using multiple linear regression. The results indicated that: (1) basic density was strongly positively linearly related to both unit tangential shrinkage (r = 0.970) and unit radial shrinkage (r = 0.959), weakly positively related to total shrinkage (r = 0.656 and 0.640 for tangential and radial, respectively), and weakly negatively related to residual collapse (r = 0.632 and 0.616 for tangential and radial, respectively). (2) The main factors affecting unit shrinkage were cell wall proportion (WP), microfibril angle (MFA), and double fiber cell wall thickness (DWT); factors playing an important role in total shrinkage were WP, ray parenchyma proportion (RP), and MFA, while RP had the highest effect on residual collapse (r = 0.949 and 0.860 for tangential and radial, respectively). (3) All corresponding regression models obtained were very suitable for the evaluation of relationships between the anatomical parameters and unit shrinkage, total shrinkage, and residual collapse, as measured using a moisture content of 28% as the fiber saturation point for all specimens.     

Some studies on the shrinkage behaviour of wood

Summary Shrinkage observed on small clear specimens in radial and tangential directions and volumetric shrinkage obtained under the evaluation of physical and mechanical properties of wood have been analysed with reference to specific gravity and fibre-saturation point (FSP). It is observed that tangential shrinkage is 1.4 to 3 times that of radial shrinkage. The difference between FSP in radial and tangential direction is not so predominant; it is possibly governed by variation in specific gravity of the wood substance. The volumetric shrinkage is noted to be approximately equal to the sum of radial and tangential shrinkages. Shrinkage is found to depend on both the specific gravity of wood and FSP. Unlike Stamm's theory, their effect is found to be additive. The effect of specific gravity is found to be more than the effect of FSP.

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Zusammenfassung Die Radial- und Tangentialschwindung kleiner fehlerfreier Proben sowie die Volumenschwindung, die während der Bestimmung der physikalischen und mechanischen Eigenschaften der betreffenden Hölzer beobachtet werden konnten, wurden hinsichtlich ihres Zusammenhanges mit Dichte und Fasersättigungspunkt untersucht. Die Beobachtungen zeigten gegenüber der Radialschwindung eine 1,4... 3,0-fach größere Tangentialschwindung. Der Unterschied bei Erreichen des Fasersättigungspunktes in radialer und tangentialer Richtung ist nicht so auffällig; möglicherweise wird er überwiegend von der Dichte der Holzsubstanz bestimmt. Es konnte weiterhin festgestellt werden, daß die Volumenschwindung etwa gleich der Summe aus Tangential- und Radialschwindung ist und sowohl von der Dichte der Holzart als auch vom Fasersättigungspunkt abhängt. Entgegen der Theorie von A. J. Stamm wurde deren Wechselwirkung als additiv erkannt, wobei der Anteil der Dichte etwas größer als derjenige des Fasersättigungspunktes sein dürfte.

     

Prediction of transverse shrinkages of young-growth Sitka spruce (Picea sitchensis) and western hemlock (Tsuga heterophylla) with ultrasonic measurements

Abstract

The objective of this study was to examine the potential of acoustic measurement as a rapid and nondestructive method to predict the dimensional stability of young-growth Sitka spruce and western hemlock. Ultrasonic velocity, peak energy, specific gravity, and radial and tangential shrinkages were measured on twenty-four 25-×102-×y 25-mm specimens obtained from a 58-year-old stand in Southeast Alaska. We found that specific gravity and peak energy of ultrasonic signals were not good predictors of transverse shrinkage, as indicated by poor correlations. Ultrasonic velocity, on the other hand, was found to be a significant predictor of transverse shrinkage and therefore has good potential to be used as a field method to evaluate dimensional stability. The single-parameter prediction model explained 86% of transverse shrinkages in western hemlock and 71% of transverse shrinkages in Sitka spruce. Further study is needed to test the capability and feasibility of using acoustic velocity to predict both longitudinal and transverse shrinkages of wood in standing trees.     

竹材热解及炭化收缩特征分析

对四种竹材的热解行为及炭化收缩现象进行了分析研究,结果表明:(1)竹材的种类和年龄对其热解特征和炭化收率有重要影响;(2)炭化过程中竹材收缩率随温度升高而增大;(3)竹材的炭化收缩率在不同年龄、不同部位也有差异.在相同炭化温度下,竹材炭化过程中切向和径向的收缩率高于轴向.     

Annual growth rhythm of Larix sibirica and Larix gmelinii provenances in a field trial in southern Finland

Abstract

The aim of this study was to analyse how the growth onset and shoot elongation of seedlings differ in field conditions in Finland for 20 Russian larch provenances and five comparison entries, and if they could be explained by the geographic and climatic conditions of the provenance origins. In this work, the Dahurian larch (Larix gmelinii Rupr.) provenances had the earliest growth onset and the northern Siberian larches (Larix sibirica Ledeb.) slightly earlier bud burst. The temperature sum and latitude of the provenances explained the differences in shoot elongation. The time needed for shoot elongation and the temperature sum needed to obtain 50% of total shoot elongation were quite equal in the years 2008 and 2009 (larger difference with the 90% level). The growth cessation was affected by photoperiod regardless of provenance. However, it was affected in the southern provenances also by declining temperatures in autumn. The final height was in 2009 largest in southern Dahurian larches. Despite our findings, the use of seed sources of domesticated Raivola origin is the safest choice for regeneration in Finland. We should still study more in detail the performance of other provenances and their adaptation capacity and suitability to Finnish forestry.     

Walnut demonstrates strong genetic variability for adaptive and wood quality traits in a network of juvenile field tests across Europe

Adaptive and wood quality trait data were collected and analyzed on commercially available Juglans regia and J. regia×J. nigra provenances and progenies planted across Europe in a multi-site network. A total of 19 seed sources, replicated 35 times per site, were planted at 13 sites from 5 European countries, encompassing the potential distribution area of timber production plantation sites. The following traits were evaluated: survival, height, diameter at breast height, stem form, apical dominance, vegetative budbreak, along with biotic and abiotic damage. Mean values were significantly different both among provenances/progenies and sites. Most common damage was late spring and early autumn frost. Bud break ranking was significantly correlated with provenance and progeny origin. Although J. regia is fast growing, southern European early budbreak plant material should not be planted under most middle European conditions where late spring frost can be expected, as it has a significant negative impact on architectural (and thus wood quality) traits. Hybrid J. regia×J. nigra progeny performed better than J. regia provenances/progenies for most traits measured. Differences were significantly in favor of hybrids at sites with medium to low fertility, although some locally selected seed sources tended to perform as well as hybrids on high fertility sites.     

汽蒸处理对小径落叶松干缩性能的影响

对小径落叶松髓心至树皮各径向位置上干缩性能的变化规律,以及汽蒸处理对这一规律的影响的研究结果表明:小径落叶松弦向、径向干缩率的径向变化有其独特性,而且汽蒸处理对弦径向干缩的影响也不尽相同。处理后弦向干缩率增大,而径向干缩率减小,结果使木材的开裂势增大,说明干缩性能的变化在汽蒸处理减缓横弯缺陷过程中未起到积极作用;本文也证实使用弦径向干缩差来反映开裂势是可行的。     

落叶松木材API胶粘剂弦径面胶接强度的差异

对落叶松木材水性高分子异氰酸酯 (API)胶粘剂弦径面胶接强度进行了研究。结果表明 :落叶松木材API胶粘剂弦径面胶接强度存在着差异 ,落叶松木材API胶粘剂径切板胶合强度试件的常态压缩剪切强度是弦切板的 1 4 1倍 ,而反复煮沸压缩剪切强度径切板的却比弦切板的低。落叶松木材本身弦径面顺纹抗剪强度和剪切强度率的试验结果表明 :造成落叶松胶合强度试件弦径面常态压缩剪切强度存在差异的根本原因在于落叶松木材本身弦径向的强度存在差异 ,木材径向的强度比弦向的大 ,文中对这造成这种差异的原因进行了分析     

Variability in physical properties of plantation-grown progenies of Melia composita and determination of a kiln-drying schedule

Plantation-grown progenies of Melia composita Willd.were studied for variability in several physical properties: density,radial and tangential shrinkage,longitudinal permeability of heartwood and sapwood.Furthermore,flat-sawn planks from each of the progeny were subjected to a quick-drying test for determination of kilndrying schedule.The mean density of the species was 0.39 g cm~(-3) and the wood may be categorized as light wood.Mean radial shrinkage(%) for the species was 2.8% with progeny-wise variation in radial shrinkage from 1.56 to 4.11%.Mean tangential shrinkage(%) for the species was 5.54% with progeny-wise variation in tangential shrinkage from 3.69 to 7.71%.The resultant tangentialradial shrinkage ratio was 1.98(less than two),which suggests that the wood is relatively stable with respect to drying behavior.Mean sapwood and heartwood longitudinal permeability of the species were 3.38 and 2.02 Darcy,respectively.Higher longitudinal permeability of sapwood and heartwood indicate better drying and preservative properties of the species.Terazawa quick-drying test method suggests that the species is less susceptible to drying defects.During the test,only moderate checks and cracks were observed.A tentative kiln-drying schedule was recommended based on these results.     

桉属树种与种源、家系比较试验

以９个桉属树种，其中８个种泊来自原产地，７个家系和７个杂种后代来自国内次生资源进行混合比较，５年生评价结果表明：树种、种源、家系呈极显著差异；尾叶桉及其两个种源、尾巨桉杂交种细叶桉的１３５４４种源适合本试验区戒严和格短轮伐期经营，可获得适应性和生长指标平均值超过平均水平３５％的选择效应。其中最优为１４５３４号尾叶桉种源，５年生单株材积０．０５０．６１ｍ＾３／株（８９．０３ｍ＾３／ｈｍ＾２）。种子采     

Characterization of viscoelastic,shrinkage and transverse anatomy properties of four Australian hardwood species

Abstract

Several key wood properties of four Australian hardwood species: Corymbia citriodora, Eucalyptus pilularis, Eucalyptus marginata and Eucalyptus obliqua, were characterized using state-of-the-art equipment at AgroParisTech, ENGREF, France. The wood properties were measured for input into microscopic (cellular level) and macroscopic (board level) vacuum-drying models currently under development. Morphological characterization was completed using a combination of environmental scanning electron microscopy and image analysis software. A clear difference in fibre porosity, size, wall thickness and orientation was evident between species. Viscoelastic properties were measured in the tangential and radial directions using dynamic mechanical analysis instrumentation. The glass transition temperature was markedly different for each species owing to anatomical and chemical variations. The radial direction showed higher stiffness, internal friction and glass transition temperature than the tangential direction. A highly sensitive microbalance and laser technology were used to measure loss of moisture content in conjunction with directional shrinkage on microsamples. Collapse shrinkage was clearly evident with this method for E. obliqua, but not with other species, consistent with industrial seasoning experience. To characterize the wood–water relations of E. obliqua, free of collapse, thinner sample sections (in the radial–tangential plane) are recommended.