Polysaccharides in some industrially important hardwood species

The amount and composition of sugar units comprising polysaccharides in sapwood and heartwood, or stemwood, of 11 industrially important pulpwood species were analysed. The polysaccharide content was between 60 and 80% (w/w) for all species, with cellulose as the predominant polysaccharide type and glucuronoxylans as the main non-cellulosic polysaccharides. The second most abundant non-cellulosic polysaccharides were either pectins, i.e. polygalacturonic acids, or glucomannans. The amount of acidic sugar units were 15–23% of the total amount of non-cellulosic sugar units in all samples, with the Acacia species in the high end. The amount and composition of water-soluble carbohydrates from ground wood samples were also analysed, since these are important in mechanical and chemimechanical pulping, and as a possible source of bioactive polymers. Sapwood released more carbohydrates than heartwood for most species. It is to be noted that the relative amount of dissolved acidic sugar units was larger from the heartwood than from the sapwood for all species. Probably due to the mild treatment conditions, the main dissolved polysaccharides were xylans only for a few samples, while easily soluble galactans, arabinogalactans, or mannans dominated in most species. Pectins dominated in heartwood of Populus grandidentata. Generally, pectins and acidic xylans were the main acidic polysaccharides.     

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.     

Effect of heat treatment intensity on some conferred properties of different European softwood and hardwood species

Effect of heat treatment intensity on some conferred properties like elemental composition, durability, anti-swelling efficiency (ASE) and equilibrium moisture content (EMC) of different European softwood and hardwood species subjected to mild pyrolysis at 230 °C under nitrogen for different durations has been investigated. Independently of the wood species studied, elemental composition is strongly correlated with the mass losses due to thermal degradations which are directly connected to treatment intensity (duration). In all cases, an important increase in the carbon content associated with a decrease in the oxygen content was observed. Heat-treated specimens were exposed to several brown rot fungi, and the weight losses due to fungal degradation were determined after 16 weeks, while effect of wood extractives before and after thermal treatment was investigated on mycelium growth. ASE and EMC were also evaluated. Results indicated important correlations between treatment intensity and all of the wood conferred properties like its elemental composition, durability, ASE or EMC. These results clearly indicated that chemical modifications of wood cell wall polymers are directly responsible for wood decay durability improvement, but also for its improved dimensional stability as well as its reduced capability for water adsorption. All these modifications of wood properties appeared simultaneously and progressively with the increase in treatment intensity depending on treatment duration. At the same time, effect of extractives generated during thermal treatment on Poria placenta growth indicated that these latter ones have no beneficial effect on wood durability.     

Dielectric properties of hardwood species at microwave frequencies

Dielectric measurements at 9.8GHz and 2.45GHz were made for the three hardwoods Euramerican hybrid poplar, alder, and oriental beech. The method used was based on Von Hippels transmission line method. The measurements were carried out at room temperature of 20°–24°C. The dielectric properties of the wood species were determined for the three principal structural directions at six different moisture conditions, covering the range of 0% to 28% moisture content. Results indicated that the behavior of all wood species studied is quantitatively similar. In general, the dielectric properties increase within the range studied with rising moisture content. The grain direction of the wood also plays a significant role.     

Shear stiffness and its relation to the microstructure of 10 European and tropical hardwood species

In this study, shear stiffness properties of 10 different hardwood species and their relation to the corresponding species-specific microstructure are investigated. For this purpose, shear stiffness of 10 different hardwood species is experimentally measured by means of ultrasonic testing. In addition, a micromechanical model for hardwood is applied in order to illustrate the influence of certain microstructural characteristics such as mass density and volume fractions of vessels and ray cells on the shear stiffness. Comprehensive microstructural and mechanical data from previous investigations of the same hardwood material support the interpretation of the microstructure–shear stiffness relationships. Mass density was confirmed to be the dominant microstructural characteristic for shear stiffness. Also, ultrasound shear wave propagation velocity increases with density, particularly in the radial-tangential (RT) plane. In addition to density, comparably higher shear stiffness G_LR can be explained by comparably higher ray content and lower vessel content. As for G_LT, a ring porous structure seems to lead to higher shear stiffness as compared to a diffuse porous structure. For this shear stiffness, vessel and ray content were found to have a less impact. Also, the rolling shear stiffness G_RT was found to be higher for a diffuse porous structure than for a ring porous one. Moreover, the data supports that ray cells act as reinforcements in the RT plane and lead to higher G_RT.     

Effect of size and geometry on strength values and MOE of selected hardwood species

The total hardwood timber stock of German forests is fast growing. The lack of knowledge concerning test standards, product standards and sorting criteria makes it difficult to expand the processing and marketing of hardwoods into the field of construction usage. Strength and stiffness data derived from small, defect-free specimens do mostly exist, but in order to be able to insert hardwoods into building applications, data derived from real size specimens is needed. Subsequently, the results of these two different specimen categories need to be correlated and the so-called size effect needs to be quantified and qualified. This paper aims to analyze the size effect of defect-free compression, bending and tensile specimens for the six European hardwood species maple (Acer spp.), birch (Betula pendula), beech (Fagus sylvatica), ash (Fraxinus excelsior), oak (Quercus spp.) and lime (Tilia spp.). They are tested exclusively parallel to grain. Regarding the compression strength for maple, birch and ash, the specimen dimensions did not influence the compression strength value. For beech, oak and lime, it was observed that compression strength increased as the specimen volume was increased. The bending strength of all species decreased as the specimen dimensions increased. Concerning the tensile strength, a clear statement on whether dimensions influence the tensile strength value is not possible. Further research with adjusted specimen sizes, specimen shapes and machine set-ups is needed. Regarding the compression and bending MOE, in most cases, the dimensions did not influence the MOE values. In tensile testing, MOE values differed significantly for the different specimen sizes. Whether these differences were due to slightly different test set-ups in the different sizes or a true size effect could not be answered conclusively.     

Log sawing positioning optimization and log bucking of tropical hardwood species to increase the volume yield

The sawmill industry is a very important link in the Mozambique forest products value chain, but the industry is characterized by undeveloped processing technology and high-volume export of almost unrefined logs. The low volume yield of sawn timber has been identified as a critical gap in the technological development of the industry. To improve the profitability of the industry, there is thus a need to develop methods and techniques that improve the yield. In this paper, different positioning of logs prior to sawing and the possibility of increasing the volume yield of crooked logs by bucking the logs before sawing have been studied. A computer simulation was used to study the cant-sawing and through-and-through sawing of the logs to determine the volume yield of sawn timber from the jambirre (Millettia stuhlmannii Taub.) and umbila (Pterocarpus angolensis DC.) species. The optimal position, i.e. the position of the log before sawing that gives the highest volume yield of sawn timber for a given sawing pattern when the positioning parameters, offset, skew and rotation, are considered gave a considerable higher volume yield than the horns-down position. By bucking very crooked logs and using the horns-down positioning before sawing, the volume yield can be of the same magnitude as that obtained by optimal positioning on full-length (un-bucked) logs. The bucking reduces the crook of the logs and hence increases the volume yield of sawn timber.     

Effect of the lateral growth rate on wood properties in fast-growing hardwood species

We investigated the feasibility of using several fast-growing tropical or subtropical hardwood species for timber production by measuring key wood qualities in relationship to the high rates of lateral growth. The trees tested were sampled from even-aged plantations of Acacia mangium, A. auriculiformis, hybrid Acacia (A. mangium × A. auriculiformis), Eucalyptus grandis, E. globulus, and Paraserianthes falcataria (Solomon and Java origin) that had already reached commercial harvesting age. The released strain of the surface growth stress (RS), xylem density (XD), microfibril angle (MFA), and fiber length (FL) were measured at the outermost part of the xylem at breast height in each tree. Results were then compared to the lateral growth rate (radius/age) at breast height, which provides a relative indicator of the amount of tree growth per year. Our findings indicated that RS was constant, regardless of lateral growth rate in each species. Similar results were observed for XD, MFA, and FL, with a few exceptions, suggesting that high growth rates do not intrinsically affect the wood properties of fast-growing tropical or subtropical species that have reached harvesting age. However, special attention must be paid to patterns of xylem maturation when developing plantations of such species.     

Physical properties of two tropical wood species from Mozambique

Abstract

The aim of this study was to reveal some important physical properties of two lesser used wood species from Mozambique. Density of wood, green moisture content (MC), shrinkage, swelling, sorption–desorption behaviour and quantitative colour analyses were carried out to facilitate the potential use of Icuria dunensis (ncurri) and Pseudolachnostylis maprounaefolia (ntholo). The study found that the average densities at 12% MC were 907.1 kg m^?3 for ncurri and 1023.4 kg m^?3 for ntholo. The average values of green MC were 31.4% for ncurri and 39.2% for ntholo. Ncurri and ntholo wood showed low coefficients of anisotropy for heartwood, 1.3 and 1.4, respectively. The colour measurements described the patterns of radial and longitudinal variations in wood colour. In conclusion, ntholo and ncurri are characterized by high density and dimensional stability. Ntholo can be used where small dimensional changes are required, e.g. in joinery, flooring and furniture.     

Characterization of the correlation structure of lumber strength properties

Spatially averaged data from the literature for along-the-length correlation of lumber flatwise bending modulus of elasticity and tensile strength was analyzed to determine the correlation of the base process for each property. The cross correlation between the two properties was also examined. The exponential correlation function, equivalent to a first-order auto-regressive process, was the best model for both correlation and cross correlation, based on the sum of squared errors between the correlations from the test data and the fitted model. The fitted functions can be used to generate correlation and cross correlation information for spatially averaged processes averaged over lengths different from the lengths used to obtain the test data.     

Liquid penetration in different cells of two hardwood species

Two experimental techniques were used to test the water permeability of two Korean hardwood species: diffuse porous Populus tomentiglandulosa T. Lee (eunsasi poplar) and ring porous white oak, Quercus serrata Thunb (konara oak). The first technique measured the void volume filled at different moisture content (MC) levels. Samples were treated with water via a schedule of full-cell impregnation. A significant relation between MC and permeability (the fractional void volume) was found. A reduction in liquid permeability was observed at MC above the fiber saturation point (FSP), whereas the opposite result was observed at MC below FSP due to the effect of the voids available in the wood. However, the differences of increased permeability from MC level 20% to 0% were found satistically the same in either wood species. The second technique measured the speed of liquid penetration in vessels, fibers, and rays with no application of external pressure. In this method, liquid flow was captured via video and the penetration speed was measured. Vessels, fibers, and rays in poplar were found to be more permeable than those in oak. Different anatomical factors such as cell diameter, cell length, pit number, pit aperture area, and thickness of the pit membrane seemed to be responsible for the variation of liquid flow rate in different cells of the two hardwood species.     

Variation in crushing strength and some related properties of a red pine

Summary Below-crown radial and height variations in maximum crushing strength parallel to grain, relative density and tracheid length of an immature, 55 year old, red pine were studied. All properties showed pronounced trends with radial age and increased from pith to bark. A radial age of 16 years was estimated as the age from which mature stem wood is formed. All properties studied varied with height above ground. Strong correlations were observed among properties. The study tree exhibited noticeably lower average crushing strength than is reported in the literature for wood from mature red pines.This work was undertaken with financial support from Karadeniz Technical University, Trabzon, Turkey, and the Natural Sciences and Engineering Research Council of Canada, Operating Grant 0GP0004417     

Theoretical and experimental deflections of glued laminated timber beams made from a tropical hardwood

Abstract

Nondestructive testing (NDT) can play an important role in improving the quality and reliability of tropical hardwood as an engineering material. By means of these methods, the stiffness of the material can be determined and the information used to improve its structural performance. Although, it is a usual approach for qualifying the material used to manufacture engineered wood products made mainly from softwoods, it is not so common for tropical hardwoods. Additionally, the lack of information regarding properties of glulam beam made from these kinds of wood is evident. In this context, the paper aimed at evaluating the theoretical and experimental deflection of glulam beams made from the Brazilian hardwood louro-vermelho (Sextonia rubra). Initially, the stiffness of each lamina was determined nondestructively using transverse vibration method (E _dtv), which has been demonstrated to be the most suitable method for this wood species. Then, ten 5-lamina glulam beams were assembled according to descending lamina E _dtv values. The experimental evaluation was performed using a four-point bending schedule. In general, the theoretical values of deflection were 2% higher than the experimental ones. The transverse vibration showed to be a suitable method to both measure lamina stiffness and predict glulam beam deflection.     

Stiffness moduli of various softwood and hardwood species determined with ultrasound

Abstract

Comprehensive data sets of the elastic constants are available for only a few European wood species. The goal of this study was to provide stiffnesses for the principal directions and planes for further selected European softwoods and hardwoods, to extend the currently existing data sets. For this purpose, a dynamic technique was chosen: the moduli were estimated on the basis of sound velocity and density measurements. The collected data may be helpful for specialists in the relevant research and practical fields, particularly when stresses and strains of structural elements have to be calculated using modelling approaches.     

23种广东常见阔叶树材的耐磨性质

本文报导23种广东常见阔叶树材的耐磨性试验结果,并对耐磨性与木材密度、硬度的关系及木材耐磨性各向异性问题作了讨论。     

五种福建阔叶树材的干燥特性

本文论述了利用百度试验法,查明福建五种阔叶树材的干燥特性,以进一步制定合理的干燥工艺。实验结果表明:这五种阔叶树材干燥特性差异显著,其中椆木干燥缺陷严重,干燥速度缓慢;润楠及枫香干燥缺陷中等;蓝果树及荷木干燥缺陷程度最轻,枫香干燥速度最快。     

Fuel properties and combustion characteristics of some promising bamboo species in India

We investigated the fuel characteristics of five important bamboo species viz., Dendrocalamus strictus, D. brandisii, D. stocksii, Bambusa bambos and B. balcooa. The selected species cover more than 85% of the total growing stock of bamboo in India. Basic density varied from 0.48 to 0.78 g?cm-3 among the bamboo species studied. Ash content, volatile matter content and fixed carbon content ranged between 1.4%-3.0%, 77.2%-80.8% and 17.6%-21.1%, respectively. Variation in calorific value(18.7-19.6 MJ?kg-1) was marginal. Fuel value index varied widely(586-2120) among bamboo species. The highest calorific value(19.6 MJ?kg-1) and fuel value index(2120) were found in B. balcooa. Ash elemental analysis revealed that silica and potassium are the major ash forming minerals in bamboo biomass. Silica content ranged from 8.7% to 49.0%, while potassium ranged from 20.6% to 69.8%. We studied combustion characteristics under oxidizing atmosphere. Burning profiles of the samples were derived by applying the derivative thermogravimetric technique which is discussed in detail. The five bamboo species were different in their combustion behaviour, mainly due to differences in physical and chemical properties. We compare fuel properties, ash elemental analysis and combustion characteristics of bamboo biomass with wood biomass of Eucalyptus hybrid(Eucalyptus tereticornis × Eucalyptus camaldulensis).     

Susceptibility of Corymbia species and hybrids to arthropod herbivory inAustralian subtropical hardwood plantations

Corymbia hybrids are becoming significant plantation varieties in subtropical and tropical Australian plantation forestry. Although primarily developed for disease resistance and amenability to clonal propagation, they have also proven to have good growth rates and site plasticity. Here we examined the susceptibility of pure Corymbia species and hybrids to pest attack. Three trial sites containing C. citriodora subsp. variegata, C. torelliana, and the hybrids C. torelliana × C. citriodora subsp. variegata, C. torelliana × C. citriodora subsp. citriodora and C. torelliana × C. henryi were assessed for pest identity, incidence and severity. Pests caused about three-quarters of the visible crown damage to trees in these trials. At the site that had the most arthropod damage, hybrid trees had higher damage scores and higher growth scores (height, diameter at breast height over bark, and volume) than pure species. Site was more important than taxon in explaining damage scores, and taxa performed differently for most traits between sites. Tree growth was negatively correlated with general crown damage, while arthropod damage alone showed no significant relationship with growth. Our results highlight the importance of establishing taxa trials across a range of sites when selecting for pest resistance.     

Tree species exhibit complex patterns of distribution in bottomland hardwood forests

?Context

Understanding tree interactions requires an insight into their spatial distribution.

?Aims

We looked for presence and extent of tree intraspecific spatial point pattern (random, aggregated, or overdispersed) and interspecific spatial point pattern (independent, aggregated, or segregated).

?Methods

We established twelve 0.64-ha plots in natural bottomland hardwood stands in the southeastern USA.

?Results

Spatial point pattern analyses (Ripley’s K, L, and L ₁₂) indicated that, when species were combined, trees were frequently aggregated and less commonly overdispersed. Plots with larger trees were more likely to exhibit overdispersion, confirming a shift to this pattern as trees grow. The intraspecific pattern of cherrybark oak and water oak was either aggregated or random. Sweetgum was aggregated on all plots and always at smaller distances (less than 5 m) than the two oak species. Intraspecific overdispersion was very rare. Interspecific segregation among the two oak species was more commonly observed (six plots) than aggregation (one plot). Cherrybark oak and sweetgum were segregated at some scale on seven of the 12 plots and aggregated on only two plots.

?Conclusion

The results from the analyses suggest that strong interspecific competition may result in segregation of trees from different species, while weaker intraspecific competition may lead to aggregations of conspecifics.