Quality of timber products from Norway spruce

Summary In a previous paper in this series it was concluded that the warp (twist, crook and bow) of structural timber products is of utmost importance for end-user satisfaction. In this paper, a study of the spatial variation of warp of fast-grown Norway spruce is presented. The material, 372 studs (45 × 70 × 2900 mm²), was cut from different radial and longitudinal positions in trees from two stands.The results indicated that twist and crook were at maximum near the pith. However, twist decreased much more rapidly with the distance from pith compared with crook. Crook associated with core studs was larger in the butt log than in the top log, while twist and bow in core studs appeared not to vary longitudinally. Heartwood formation in the butt log juvenile core did not diminish warp propensity. Twist was rather well correlated to the distance between pith and centroid of cross section. The ratio of grain angle to pith distance was the best parameter to predict twist. Presence of compression wood increased bow and crook significantly, while ring width, density and knot area ratio did not substantially contribute to explain warp variation.A moisture content change from 18% to 12% decreased the overall acceptability, expressed by stud grade yield, from 76% to 43%. Thus, timber products should be delivered at a moisture level close to the one expected in the finalized building in order to avoid excessive warp after delivery.The authors gratefully acknowledge the support from EEC Forest programme, Contract No MA2B-0024, from NUTEK project No 9100554 and from Södra Timber AB     

Quality of timber products from Norway spruce

Summary The overall aim of this study and series of papers is to address the key variables for timber quality and to optimize the utilization of Norway spruce timber with respect to construction purposes. It is the end-user's degree of overall satisfaction that determines the quality of a product. Therefore, the performance of structural timber cannot solely be defined by mechanical properties. Geometric performance (warp) must be improved if timber is to continue as an important building material.An experimental study of the spatial variation in warp and bending properties of fast-grown Norway spruce is introduced. In this paper, the growth characteristics are presented as a function of stand and location in the tree. The knot area ratio (KAR) was considerably higher in the core (0.31) compared with timber closer to bark (0.21). The top log studs had higher KAR (0.38) than the corresponding butt log studs (0.31). The average grain angle was 3.5% ( 2°) and appeared not to vary radially. The presence of compression wood was much more common in the top log timber (75%) than in the butt log (44%). However, no consistent radial variation in compression wood was found.The authors gratefully acknowledge the support from EEC Forest programme, Contract No. MA2B-0024 and from Södra Timber AG from NUTEK project No. 9100554     

Optimal timing of early genetic selection for sawn timber traits in <Emphasis Type="Italic">Picea abies</Emphasis>

In breeding Norway spruce, selection for improved growth and survival is performed at age 10–15 years in order to optimize genetic gain per year. We investigated whether a selection based on wood traits such as density and grain angle, measured under bark in the field at the same age would be informative enough with respect to structural quality traits of sawn boards. To achieve this objective, a sawing study was conducted on the butt logs of 401 trees from a 34-year-old Norway spruce progeny trial situated in southern Sweden. Stem discs were excised from the top of the logs and radial profile data of grain angle, and wood density was recorded for specific annual rings. The sawn and dried boards were assessed for structural traits such as twist, board density, bending stiffness (static modulus of elasticity, sMoE) and bending strength (modulus of rupture, MoR). Additive genetic correlations (r_a) between single annual ring density measurements and board density, sMoE and MoR were consistently strong (r_a>?0.7) for annual rings 5–13. Genetic correlations of similar magnitude between grain angle and board twist were estimated for all investigated annual rings (from 2 to around 26 under bark). Consequently, it was found that indirect selection for wood density and grain angle at the tree age 10–16 years would result in more genetic gain per year than selection at later ages. This makes it feasible to perform simultaneous selection of progeny in the field for both growth and wood traits at similar ages.     

Variation of tensile strength with annual rings for lumber from the Japanese larch

To examine the effectiveness of long rotation forestry and the potential of complete utilization of Japanese larch (Larix kaempferi Carriere), we designed a tensile test using the lumber from six 87-year-old sample trees. Results showed that strength properties of lumber varied greatly in the radial direction within trees, but all sample trees showed a similar trend. There was little difference in dynamic Young's modulus but a large difference in tensile strength (TS) between the lumber and small clear specimens from undestroyed parts of the lumber. These differences decreased with an increase in ring number and became constant after 30 years. The presence and distribution of knots markedly affected the TS; and among the knot indices, the knot number (Kn) and knot area ratio of a maximum single knot (Km) proved to be effective for explaining the effect of knots. The distribution of Kn and Km in the radial direction agreed with the variation of TS in the radial direction. By investigating the variation patterns of lumber and small clear specimens in the radial direction, it was found that the strength properties of both required a long time, about 30 years, to reach a relatively constant state.Part of this report was presented at the 49th annual meeting of the Japan Wood Research Society, Tokyo, April 1999     

Using acoustic wave velocity to select fibre-managed plantation Eucalyptus nitens logs for laminated veneer lumber products

The aims and objectives of this study were to investigate the potential to predict laminated veneer lumber (LVL) stiffness from wood properties measured on trees and logs, and determine variation in log, wood and veneer properties as a function of tree height and age. Log selections were made from trees in three stands that were planned for harvesting at 14, 20 and 21 years of age. Rotary peeled veneer recovery from the logs was on average 65%. After drying, Metriguard testing showed over 50% of the veneer had an estimated dynamic modulus of elasticity (MOE_dyn) above 12 GPa, with 20% above 14 GPa, and that veneer from the second log by tree height had higher MOE_dyn values. In visual assessment to the AS/NZS 2269.0:2012 Standard, no veneer could be utilised in a panels face or subface positions and the older-age stand provided almost four times the volume of usable veneer. Standing-tree acoustic wave velocity (AWV) explained a moderate amount of variance in log MOE_dyn and Pearson correlation coefficients between the (Metriguard) veneer MOE_dyn, log AWV, log MOE_dyn and disc basic density were significant, positive and strong, with log AWV explaining most of the observed variance in log stiffness. A moderately strong and positive linear regression existed between log AWV and veneer MOE_dyn, supporting the use of log AWV tools for the ranking of stiffness in fibre-grown plantation E. nitens logs. Mechanical strength testing of LVL studs extracted from panels manufactured from the trial’s veneer indicated they equalled, and for some tested parameters exceeded, the characteristic design strength values previously published by commercial LVL manufacturers for equivalent size pine products.     

Stiffness gradients in radiata pine trees

A mill study of 62 trees, in which boards were reassembled into their original logs, permitted the construction of wood quality maps. In this instance stiffness profiles were obtained from butt to upper-top logs, based on machine stress grading of all boards and then averaging values from the 62 trees. Traditionally the butt log has been perceived to be the most valuable log in a tree, because it is bigger and gives a higher recovery of lumber. However, it is shown to contain a wide cone of very low stiffness wood that is confined to the first 2.4–2.7 m above ground level. Above this point stiffness gradients become cylindrical with no noticeable decrease in stiffness up the tree stem. Stiffness in all logs increased radially from pith to cambium with the greatest change being associated with the wood nearest the pith. The low stiffness at the base of the tree suggests that an alternative log bucking strategy should be considered, namely cutting a short 2.4–2.7 m butt log for plywood/LVL or for bolter sawing and only cutting standard length logs above this point.The least stiff logs (lowest 20%) yielded lumber that had an average stiffness that was over 1 GPa less than the average for the population. A case can be made for separating these logs and processing them differently.     

Intratree Variability of Cleavage Resistance of Chinese Fir from Plantation

INTRODUCTION Chinese fir (Cunninghamia lanceolata) is a very important timber species in the southern China (Shi Jisen et al. 1987). It is good, fast-growing, and exempts from serious plant diseases. Its plantation is big in terms of size in the South of China and its storage stock is very rich, which is about 20% of the national commodity wood (Zhou Shuangquan et al. 2000). And the lumber becomes mainly commercial construction materials in China because of straight grain, light and so…     

Gremmeniella-infected Pinus contorta as raw material in the production of kraft pulp

Pinus contorta, logs with occluded cankers caused by the pathogen Gremmeniella abietina, as well as logs from unaffected trees were sampled from a 23-year-old plantation in Sweden and compared in terms of their paper properties. Damaged wood gave kraft pulp with poor paper properties: it required a larger amount of beating energy and resulted in paper with low tear strength, air permeability, tensile stiffness, burst strength, and poor light-scattering properties. However, small amounts of damaged wood mixed in with a large amount of healthy wood can pass almost unnoticed. The use of trees with a larger content of damaged wood will lead to serious processing problems and give a pulp with poor paper properties. Thus, wood damaged by Gremmeniella should be sorted out and classed as low-grade raw material.     

Models for predicting microfibril angle variation in Scots pine

Context

Microfibril angle (MFA) is one of the key determinants of solid timber performance due to its strong influence on the stiffness, strength, shrinkage properties and dimensional stability of wood.

Aims

The aim of this study was to develop a model for predicting MFA variation in plantation-grown Scots pine (Pinus sylvestris L). A specific objective was to quantify the additional influence of growth rate on the radial variation in MFA.

Methods

Twenty-three trees were sampled from four mature Scots pine stands in Scotland, UK. Pith-to-bark MFA profiles were obtained on 69 radial samples using scanning X-ray diffractometry. A nonlinear mixed-effects model based on a modified Michaelis–Menten equation was developed using cambial age and annual ring width as explanatory variables.

Results

The largest source of variation in MFA (>90 %) was within trees, while between-tree variation represented just 7 % of the total. Microfibril angle decreased rapidly near the pith before reaching stable values in later annual rings. The effect of ring width on MFA was greater at higher cambial ages.

Conclusion

A large proportion of the variation in MFA was explained by the fixed effects of cambial age and annual ring width. The final model is intended for integration into growth, yield and wood quality simulation systems.     

Inter-tree and intra-tree variations in ring width and wood density components in balsam fir (Abies balsamea)

This study quantified and compared intra-tree and inter-tree variations in ring width and wood density components in balsam fir (Abies balsamea) grown in Quebec, Canada. In addition, the study examined correlations between ring width and wood density components at different stem positions from the stump level to the stem top. Ring width and wood density components of individual rings were measured by X-ray densitometry. Both the intra- and inter-tree variations in balsam fir are large, but the inter-tree variation is relatively smaller than the intra-tree variation. Much of the intra-tree variation is due to the radial variation, whereas the axial variation is much smaller. Compared to ring width and its components, wood density characteristics show a considerably smaller variation at both the inter- and intra-tree level. In almost all wood characteristics studied (except for latewood width), the intra- and inter-tree variations are more or less influenced by tree age. Cambial age explains more intra-tree variation in wood density components than ring width, whereas more intra-tree variation in ring width components is due to ring width. Cambial age and ring width explain a comparable percentage of variation in ring density. Only a few of the correlations between ring width and wood density components vary significantly with stem position from the stump to the stem top at the inter-tree level. In balsam fir, a negative correlation between ring density and ring width is significant in the butt log, but the correlation decreases to an insignificant level at and above a height of 3.0 m.     

马尾松人工林管胞长度的株间和株内变异

林木株间变异和株内变异是木材的两个主要变异来源,由于木材性状具有较强的遗传性以及育林措施对木材的可塑性,人们可以培育出材质优异的木材,然而因变异的存在,在如何充分利用木材时却遇到了许多困难。林学家的一个主要目的就是在充分掌握木材变异规律的基础上,采用有效方法提高材质的均匀性。     

乔木柳无性系木材基本朱内变异的研究

利用乔木柳12年生无性系对比试验林的材料，研究了13个柳树无性系木材基本密度株内径向和纵向的变异模式，并对密度选择的时期和取样位置进行了探讨。结果表明：（1）在1.3m高度，乔木柳无性系各年轮组木材戏向变异多数为“M”型曲线，即从木芯向外第、至第3年轮组（1－6a）的木材密度逐渐增加，第4年轮组（7－8a）略有下降，第5年轮组（9－10a）又有明显增加，至最外侧年轮（11－12a）木材密度则显著下降，根据各无性系的变异特点，分成3种类型，其中无性系221的变异较为独特，为典型的“N”型；（2）乔木柳无性系生长期密度变化的规律为：1－2年生时木材基本密度相对较低，3－4a以后密度相对稳定并接近无性系加权平均密度，3－4年生时木材基本密度与5－12年生时的测定值相关系数为0.789－0.985，均达到极显著相关水平（α＝0.01），5－12年生乔木柳无性系木材基本密度的变异为62.2％－97.0％与3－4年生时木材基本密度的值有关，3－4a作为5百木柳木材基本密度的选择年龄最为合适；（3）供试群体木材密度株内纵向变异模式大多也可用“M”型曲线加以描述，具典型的苴孔材绷向密度变异特征，根据各无性系的变异特点，分成4种变异类型；树干高1.3，3.6和7.2m处的木材基本密度与无性系平均密度的相关系数达到显著和极显著水平，可以在树干1.3m处取样以推测无性系平均值；（4）在供试群体中，有的无性系木材基本密度纵向和径向变异的幅度均很小，木材较为均一，如苏柳791，表明在乔木柳杂种后代中选择木材均一的柳树新品种是可能的。     

Heart splitting at crosscutting of eucalypt logs

The occurrence of heart splitting during the crosscutting of logs was discussed in relation to the released strain on Eucalyptus spp. logs. The strains released in the longitudinal and tangential directions were measured by the strain-gauge method and were correlated with the length of the heart split measured on the same logs. There were differences in the longitudinal strain; however, no significant correlation was found with the diameter that could be converted to a mean annual increment (i.e., a relation with the growth rate). The initial splits expand with the time after felling. The longer the initial split, the longer is the length 1 week after felling. The split length was significantly smaller at the butt end of the first log of every tree than at the other end, but there were no significant differences between the split length at the top of the first logs and at either end of the second logs, although there were differences among individual trees. The length of the heart split correlated with the released strain near the pith, which was estimated using Kublers equation. The longitudinal released strain measured on the surface of logs is a good indicator of the heart splitting when crosscutting logs.Part of this paper was presented at the 52nd Annual Meeting of the Japan Wood Research Society     

The effects of heavy thinning on stem quality and timber properties of silver birch (Betula pendula Roth)

A study was carried out into the effects of heavy thinning onstem quality and timber properties of silver birch (Betula pendulaRoth). Comparisons were made with lightly thinned and unthinnedbirch stands. Birch stands from the UK were also compared withsimilarly managed stands from Germany and Denmark. In general,trees from lightly thinned and unthinned stands had similarcharacteristics. Heavy thinning enhanced diameter incrementthrough greater ring width in comparison with the other treatments.The timber properties of basic density, grain angle and shrinkagecoefficients in the radial, tangential and longitudinal directions,however, were largely unaffected. More and bigger branches andgreater stem taper were found on trees from heavily thinnedstands, but these stems still met the current Finnish veneerbirch quality and dimension standards. Comparisons between birchstands, managed by heavy and light thinning, from the UK andGermany and Denmark revealed no meaningful differences in timberproperties. The results suggest that veneer dimension and qualitylogs could be produced in the UK in rotations as short as 40years on good sites if heavy thinning is adopted.     

Tree growth stresses—Part IV: Visco-elastic strain recovery

Summary Experimental methods for the determination of visco-elastic strain recoveries in timber are described. Intensive studies were carried out on Eucalyptus regnans F. Muell., to determine the characteristics of visco-elastic, longitudinal strain recovery, and its distribution along radial limes, in wood from butt, middle and top logs of trees; and also to investigate the effect on strain recovery of different diameters of trees and tree ages. Much less extensive tests, made on three other eucalyptus species and on Pinus radiata D. Don, were undertaken to explore the possibility of strong species differences. It was found that the total visco-elastic strain recovery varied from maximum tensile values near the bark, through zero to maximum compressive values near the pit. It followed an exponential-rate curve commencing immediately after elastic strain release. Increments after 14 days were rarely measurable. An effect of increasing recoveries with age was proved highly significant. Large differences in recovery were evident between the softwood and the hardwood species. The authors wish to acknowledge the valuable assistance of the Division of Mathematical Statistics, CSIRO. In particular, their thanks are due to Miss N. Ditchburne of that Division, especially in connection with estimates of the significance of trends in the data. They also acknowledge the helpful suggestions of Dr. P. U. A. Grossman of this Division, that led to the theoretical development given in Appendix III.     

Effects of commercial thinning,log position in the stem,and cutting width on the surface quality of cants produced by a chipper-canter

Fifteen stems of jack pine (Pinus banksiana Lamb.) of 3 commercial thinned plots (control, moderate, and intensive thinning) and 15 stems of black spruce (Picea mariana (Mill.) B.S.P), both coming from the Abitibi-Témiscamingue region – Canada, were cross-cut into three 2.4?m length sections: bottom, middle, and top logs. Logs were processed with a chipper-canter at three cutting widths (12.7, 19.1, and 25.4?mm), producing chips and a three-faced cant. The middle section of the cant was used to evaluate surface quality across the grain on each face. Roughness and waviness parameters and depth of torn grain were recorded. Knot characteristics were assessed in the three cant faces. Poorer surface quality was found in the lower part compared to the upper part of the cant for both species. At larger cutting widths, jack pine logs coming from a natural stand showed lower surface quality compared to logs from thinned stands. Black spruce waviness increased with the cutting width and stem height. These results were attributed to the increase of forces and vibration when cutting at larger cutting widths, which was worsened by the presence of bigger, more numerous knots at the control plot and in the top logs. Black spruce had deeper torn grain compared to jack pine. Their differences in knot characteristics resulted in a maximum torn grain depth favored by the presence of more knots rather than by bigger knot size. Other knot characteristics, such as the position of the knots in the cant face, the insertion angle of the branch and the distribution of the knots around the log, should be studied to better understand the relationship between torn grain formation and knottiness.     

Wood properties of teak (<Emphasis Type="Italic">Tectona grandis</Emphasis>) from a mature unmanaged stand in East Timor

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.     

油松树干横截面面积年增长量的垂直分布及与材积年增长量和叶量的关系

【目的】揭示油松树干横截面面积年增长量(RAI)的垂直分布特征和主要控制机制,验证Cortini等(2013)建模方法和模型形式在油松上的应用效果,确定基于RAI模拟预测材积年增长量和单木叶生物量的理想模型和树干位置。【方法】在9个不同年龄和竞争状态的油松林内选取27株10~98年生样木,于不同树干位置截取312个圆盘测算并分析各样木的RAI垂直分布模式,比较其与各理论模式的异同,揭示相关机制;基于Cortini等(2013)建模方法和模型形式构建油松RAI垂直分布模型,根据拟合优度等验证并评价其应用效果;在不同RAI垂直分布模式和整体水平,比较分析不同树干位置RAI与全树干水平的差异及与材积年增长量和单木叶生物量的关系,确定理想模型和树干位置。【结果】油松RAI垂直分布包括2种模式,差异主要源自树干中间区,有效树冠区和膨大区RAI分布分别与水分传输和机械支持的理论模式相近,而中间区RAI分布与各理论模式的异同因样木而异;RAI垂直分布模型可解释其垂直变异的82.76%;不同模式和整体水平,有效树冠基部RAI与全树干水平的差异均小于其他位置,胸高处RAI与单木叶生物量的关系均优于其他位置,而与材积增长量的异同因模式而异,或优于其他位置或略差于理想位置。【结论】水分传输和机械支持需求分别决定有效树冠区和膨大区的RAI垂直分布,二者的相对重要性及生物环境等因子共同决定树干中间区的分布;Cortini等(2013)建模方法和模型形式在油松上的应用效果良好;有效树冠基部对全树干水平的代表性较高,在胸高处测算RAI并据此预测材积年增长量是有效但存有缺陷的方法,对单木叶生物量的模拟预测效果良好。     

Variation in density of Picea sitchensis in relation to within-tree trends in tracheid diameter and wall thickness

The influences of cambial age and ring width on density of Sitkaspruce (Picea sitchensis (Bong.) Carr) were analysed in relationto within-tree trends in tracheid diameter and cell wall thickness.Discs were sampled at breast height from a total of 24 trees,from seven stands at three contrasting sites in Wales, and atbreast height, 30 per cent and 60 per cent total tree heightfrom one of the stands. Across the juvenile wood, ring density decreased with ring numberfrom the pith while radial tracheid diameter increased. Theseoverall trends were considered to be inherent to tree growth,presumably associated with cambial ageing, since they occurredin all trees on all sites. In juvenile wood, density also variedwith site growth rate (as indicated by ring width) at similarcambial age, wider rings being associated with more rapidrateof change in tracheid diameter with ring number and with decreasein tracheid wall thickness. Consequently, on a site having treeswith high growth rate density decreased more rapidly acrossthe juvenile wood, down to a lower minimum value, than on siteswith a slower growth rate. In mature wood, the decrease in densitywith increase in ring width was associated with differencesin both tracheid diameter and wall thickness. Density was slightly(though not significantly) higher at breast height than in comparablerings at 30 per cent total height, associated with significantlythicker tracheid walls at breast height. Changes in radial tracheid diameter (with ring number, or withring width) were associated with greater differences in theearlywood than towards the latewood end of each growth ring,while variations in wall thickness with ring width were associatedwith rate of increase in wall thickness towards the latewoodend. This may account for some previously conflicting reportson influence of silvicultural management on density, for densityis likely to vary with influence of environment on the seasonalcycle of cambial activity. The extent of the juvenile wood as delimited by the inner coreof wide growth rings does not necessarily correspond to theregion of varying tracheid dimensions in Sitka spruce.     

Butt rot ofChamaecyparis obtusa (Sieb. et Zucc.) Endlicher trees caused byPerenniporia subacida in Shikoku district, Japan: Pathogen, distribution of damaged trees in the stand, and soil investigation

The rot ofChamaecyparis obtusa (hinoki) trees was studied in the northern part of Kagawa Prefecture, Japan. Among 158 hinoki examined, butt rot was found in 28.6, 58.3, and 100% of trees in the 29, 30, and 34-year-old stands, respectively. All trees with butt rot, and 11 trees without it had rotted roots. Thirteen hinoki were peeled byCervus nippon (sika deer) and all of them were infected with butt rot. The maximum height of rot in deer-damaged trees was 2.6 m from the ground level, but was 1.9 m in undamaged trees. About eighty-two percent of rotted trees showed rotted areas of less than 40 cm² on the cross section of stems at the ground level. White mycelia and black flecks sometimes appeared in the rotted wood. Basidiocarps of polyporaceous fungus were often found on felled logs and rotted stumps of hinoki and identified asPerenniporia subacida. Basidiomycetous fungus was isolated frequently from rotted wood of roots and stems, and determined to beP. subacida by comparative study on cultural characteristics. An inoculation experiment and wood-decay test proved that the fungus was the cause of the rot of hinoki. Few absorbing roots of living trees were found in the clayey subsurface soil of the high dry bulk density and the less soil aeration. Some absorbing roots had root rot and the rot spread from the base of the absorbing root to the central part of the woody root. This is the first report on the rot of hinoki caused byP. subacida in Japan.