Air-coupled ultrasound and electrical impedance analyses of normally dried and thermally modified Scots pine (Pinus sylvestris)

Wood is graded according to strength in various applications. The ultimate strength can only be determined by breaking the specimen, and thus other characteristics like density and modulus of elasticity (MOE) are used for estimation of the strength. In this study, the properties of normally dried and thermally modified Scots pine were studied using electrical impedance and air-coupled ultrasound (ACU) methods. Density, hardness, MOE and strength were analysed and compared with the electrical and ultrasonic responses. The measurements were conducted in stable laboratory conditions with well equilibrated samples and the moisture content was not determined. Both the ultrasonic and electrical parameters correlated with the density and mechanical properties. Using multivariate analysis, density could be estimated with accuracy of 21 kg/m³ (SD) for normally dried timber and 13 kg/m³ (SD) for thermally modified timber (TMT; N = 15). MOE could be estimated with accuracy of 0.7 kN/mm² (SD) for normally dried timber and 1 kN/mm² (SD) for TMT (N = 14). According to the study, electrical impedance spectroscopy combined with ACU measured across the grain is a potential non-destructive technique for the strength estimation of wood.     

Shrinkage-related degrade and its association with some physical properties in Eucalyptus regnans F. Muell

Summary Assessments of internal checking and the physical properties of 124 trees of Eucalyptus regnans F. Muell. have shown that for material dried under relatively mild predryer conditions (30 °C, 65% RH) internal checking was highly positively correlated with each of collapse, moisture content and normal shrinkage, and weakly negatively correlated with total external shrinkage. Collapse alone explained 47% of the variation in internal checking. Incidence of internal checking in sample boards could be estimated with moderate success by each of the following properties measured on board ends: collapse, the number of internal checks and initial moisture content. Material with high mean basic density above 530 kg/m³ was associated with low levels of internal checking and collapse. However, the maximum naturally occurring density of E. regnans was not high enough to obviate collapse and internal checking. It was observed that growth rings in 100 × 50 mm backsawn boards in which the earlywood air-dry density was below 450 kg/m³ showed internal checking. The size and number of internal checks increased with a decrease in earlywood density. It was shown that drying E. regnans below temperatures of 24–30 °C does not eliminate collapse, thus raising doubt about the validity of a temperature threshold concept in that range. Received 17 September 1997     

Dielectric spectroscopy of Scots pine

Dielectric properties of Scots pine (42 trees) were compared with density, moisture content (MC), and resin acid content (RAC) (of heartwood). The samples were measured in frozen, green, conditioned and non-conditioned dry moisture states to evaluate the potential of dielectric spectroscopy in determining the wood characteristics at different stages of wood processing. Heartwood and sapwood parts of each sample were measured separately, and through-transmission measurement was conducted in longitudinal and tangential direction at frequencies from 1 MHz to 1 GHz. The MC and density correlated significantly with the dielectric parameters in both measurement directions but especially in longitudinal direction. The RAC of the heartwood correlated significantly with tanδ and ε″/(ε′ ? 1) of the green samples measured in the tangential direction at frequencies above 200 MHz. The correlation at 1 GHz was ?0.56 for green samples, ?0.66 for conditioned samples and ?0.61 for non-conditioned samples (P < 0.001, for all). The study suggests that the extractives also affect radio-frequency dielectric responses, which might be used for extractive analyses of pine heartwood.     

Variation in wood density and ring width in Acacia melanoxylon at four sites in Portugal

The radial variation in wood density in Acacia melanoxylon R. Br. was studied using microdensitometry by sampling 20 trees with a 40-cm diameter class at four sites in Portugal. The measurements were taken from pith to bark at breast height. A. melanoxylon had an average ring density of 0.607 g cm^?3, ranging from 0.556 to 0.630 g cm^?3. The mean growth was 6.0 mm year^?1. Latewood corresponded, on average, to 34 % of the ring width. Between-tree variability at each site was the main source of variation in the density components, representing between 30 and 54 % of the total variation. Between-sites variability represented from 0 to 21 % of the total variation in density components. The environmental effects (site related) were more pronounced on latewood, while the genetic effect (tree related) was more evident in earlywood. Ring width, latewood percentage and heterogeneity index were independent from site, trees in site and age effects. The values of wood density and radial growth revealed that A. melanoxylon can be important as a commercial timber species in Portugal.     

Collapse and internal checking in the latewood of Eucalyptus regnans F.Muell

Summary Tangential shrinkage was measured on longitudinal-tangential slices of separate earlywood and latewood from one board of Eucalyptus regnans F.Muell. at various temperatures. Large amounts of collapse shrinkage were measured in the latewood slices, and lesser amounts in the earlywood slices. Collapse shrinkage in the earlywood was found only when the slices were dried at temperatures above a minimum temperature (the collapse threshold temperature). End-coated board sections approximately 200 mm long were rapidly dried at dry-bulb temperatures below the collapse threshold temperature for earlywood. Incipient internal checks were found in the latewood of these boards. Board sections dried at higher temperatures showed internal checks starting in both early and latewood. A non-linear drying simulation model was modified to take the heterogeneous nature of wood into account. This model predicted that internal checks would form in this wood even if it were dried sufficiently slowly to avoid surface checking.Symbols D Diffusion coefficient - e_c Creep strain - e_i Instantaneous strain - e_m Mechano-sorptive strain - e_n Net strain - e_u Unconfined shrinkage strain - EW Earlywood - FSP Fibre saturation point - LW Latewood - L-T Longitudinal-tangential slice - MC Moisture content (kg water/kg dry wood) - q Moisture concentration - R-T Radial-tangential slice - t Time - y Depth in board The author is pleased to acknowledge the assistance of Emeritus Professor A. R. Oliver, Associate Professor P. E. Doe, University of Tasmania, and the Australian Furniture Research and Development Institute     

Climatic significance of tree-ring width and intra-annual density fluctuations in Pinus pinea from a dry Mediterranean area in Portugal

In Mediterranean climates trees may go through two periods of dormancy, resulting in special anatomical features such as false rings and other intra-annual density fluctuations (IADFs). In this paper, ring growth and the presence of IADFs were studied in Pinus pinea L. growing in the coastal and inland regions of Alentejo (southern Portugal). In order to identify the triggering factors associated with the IADFs, a new classification was proposed for the IADFs in P. pinea: Type E (latewoodlike cells within earlywood); Type E+ (transition cells between earlywood and latewood); Type L (earlywoodlike cells within latewood) and Type L+ (earlywoodlike cells between latewood and earlywood of the next tree ring). Response function analyses showed that radial growth of P. pinea was strongly correlated with precipitation in southern Portugal. The climatic response of P. pinea was higher in the inland area where the summer drought is more severe, the winter temperatures are lower and the soils have low water-holding capacity, in comparison with the coastal area. IADFs were frequent in P. pinea and most of the IADFs were observed in latewood. The presence of IADFs was correlated with fluctuations in climate parameters during the growing season. The IADF type E+ was linked to precipitation events early in summer. The IADF type L and L+ were associated with above-average precipitation in early autumn.     

Variation of indole acetic acid (IAA) amounts in cambial-region tissues in 7- and 24-year-old sugi (Cryptomeria japonica) trees

Recently, breeding programs have attempted to produce high growth rates for shorter rotation cycles in plantation trees. In these trees, the ratio of juvenile wood increases; thus, the juvenile wood properties should be improved for structural use. To this end, it is important to understand the influences on juvenile wood properties precisely. In this study, we report on the indole acetic acid (IAA) amounts of juvenile sugi (Cryptomeria japonica) trees in September and compare the IAA amounts to those in mature trees. The IAA amounts at the lower trunks in juvenile trees were significantly larger than those in mature trees and the IAA amounts decreased with tree height. In each stand, except a mature tree stand, there is no significant effect of IAA amounts on latewood width and MFA. However, put together all samples, the latewood width and MFA increased with IAA amounts in samples with IAA <200 ng/cm². The samples at lower trunk in juvenile trees had significantly larger IAA amounts, larger MFA and larger latewood width than the samples in mature trees (p < 0.01). The very large IAA amounts may have a certain relation with juvenile wood properties.     

Early assessment of density features for 19 Eucalyptus species using X-ray microdensitometry in a perspective of potential biomass production

Eucalyptus plantations have been considered for bioenergy production and hence their biological characteristics that make them amenable to intensive short-rotation forestry. Wood density is an important parameter that directly affects fuel production. This study focuses on the early assessment of density features for 19 Eucalyptus species using X-ray microdensitometry in a perspective of potential biomass production. Average ring density, earlywood density, latewood density, latewood percentage and the heterogeneity index were studied. E. polyanthemos registered the highest mean wood density value (0.84 g cm^?3), and E. viminalis showed the lowest value (0.53 g cm^?3). An indicator for the potential wood biomass (PWB) was calculated, with E. maculata displaying the highest biomass production index (13.4 kg). Comparison of radial growth of these species showed appreciable differences. The PWB indicator points to the prospective good aptitude for short-rotation cycle for biomass production of E. maculata, E. botryoides, E. globulus, E. nitens and E. sideroxylon.     

Characterization of raffia palm fiber for use in polymer composites

Raffia palm fibers are potential reinforcement materials for making cost-effective polymer-based composite. This paper presents the results obtained from a study of physical, chemical, thermal and mechanical properties of raffia palm fibers (RPFs) derived from the raffia palm tree (Raphia farinifera). The as-received RPFs had their remnant binders manually removed and was subsequently cleaned in a 2% detergent solution before drying in an air oven at 70 °C for 24 h. Evaluation of the properties of the dried samples was carried out using a combination of characterization techniques including chemical composition determination, density measurement, moisture adsorption and water absorption measurements, tensile testing, scanning electron microscopy (SEM), differential scanning calorimetry (DSC), Raman spectroscopy, X-ray diffractometry, and Fourier transform infrared spectromicroscopy. The main constituents of RPFs were found to be cellulose, hemicellulose and lignin. The average diameter and average density were 1.53?±?0.29 mm and 1.50?±?0.01 g/cm³, respectively. The average breaking strength of the fibers ranged from 152?±?22 to 270?±?39 MPa; it did not vary significantly with fiber length and cross-head speed during tensile testing. The results of scanning electron microscopic investigation of the fibers showed that they comprise several elemental fibers which are tightly packed together with each having its own lumen. Synchrotron-based Fourier-transform infrared spectromicroscopy of a cross-section of the fiber showed that lignin is concentrated mostly on the outside while cellulose and pectin are concentrated in the mid-section. A two-stage water sorption behavior was observed for the fibers.     

Wood properties of young Douglas-fir in Southern Italy: results over a 12-year post-thinning period

This paper describes the study of a 31-year-old Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) stand located in Southern Italy, which was thinned 19 years after planting. The aim of the study is to evaluate the influence of three thinning treatments (unthinned, selective, and geometrical) performed twelve years later on wood density (WD), moisture content, shrinkage, ring width (RW), latewood proportion (LW%), modulus of elasticity, compression (CS), and bending strength (BS). The WD was higher in the unthinned stand. LW% and BS were lowest in the selective thinning and in the geometrical thinning, respectively. No significant differences were found in other variables. In addition, the thinning processes mostly affected the medium tree class more than the dominant and suppressed ones. Regression analysis established a correlation between mechanical characteristics and WD, RW and LW%. Mechanical strength is strongly correlated with WD than other variables. The stepwise model showed that WD and RW are most closely related to the behavior of CS, whereas only WD explained variation in BS. Stand density reduction may improve the development of stands without greatly affecting wood quality.     

Microwave and steam injection drying of CO2 laser incised Sugi lumber

To investigate the effect of CO₂ laser incising under five drying methods on drying characteristics of Sugi lumber, the squares (120 mm × 120 mm) of Sugi lumber with length of 650 mm were used. A half of samples were incised by CO₂ laser with incising density of 2,500 holes/m². Five types of drying methods were used: microwave drying, steam injection drying, and three combinations of microwave heating and steam injection drying. Steam injection drying was conducted by injecting superheated steam of 120 °C through a perforated plate heated to 140 °C of an injection press. Microwave was irradiated with the power of 3 kW at frequency of 2.45 GHz. The results indicated that incising helps heat through a specimen and thus the whole temperature raised rapidly, which was up to threefolds compared to that of no-incised one. Incised specimens dried by a combination of microwave heating for 1 h and steam injection showed the highest drying rate, which was up to 5.3 %/h. Incising and microwave heating contributed positively to dry lumber under more uniform distribution of moisture content and to reduce surface and internal checks. Incised specimen dried by microwave showed the most uniform distribution of moisture content without surface and internal checks.     

Radial and between-family variations of the microfibril angle and the relationships with bending properties in Picea jezoensis families

With emphasis on tree breeding for wood quality in Picea jezoensis, we aimed to evaluate radial and between-family variations in the microfibril angle (MFA) of the S₂ layer in the latewood tracheids in 10 open-pollinated families of 43-year-old P. jezoensis trees. In addition, the relationships between MFA/wood density with the modulus of elasticity (MOE) or modulus of rupture (MOR) were investigated. Significant differences in MFA between families were found from the pith toward the bark. MFA showed higher values around the pith area, although some families showed relatively lower values than others around this area. In addition, due to a larger coefficient of variations of MFA near the pith, the potential for juvenile wood MFA improvement may be greater compared with mature wood. MOE was correlated with MFA in juvenile wood and with wood density in mature wood, whereas MOR was mainly correlated with wood density at radial positions in both woods. Therefore, to improve the MOE and MOR of P. jezoensis wood, both MFA and wood density would be factors to consider in both juvenile and mature woods. On the other hand, there are indications that, only wood density would be an important criterion for improving mature wood properties.     

Genetic variation of wood tracheid traits and their relationships with growth and wood density in clones of <Emphasis Type="Italic">Pinus tabuliformis</Emphasis>

To improve wood quality for pulpwood industries, it is important to examine not only wood density but also its components, especially tracheid characteristics. We studied genetic variations in the following tracheid traits by earlywood (EW) and latewood (LW): tracheid length (TL), double wall thickness (WT), radial lumen diameter (R_D1), tangential lumen diameter (T_D1), radial central diameter (R_D2), and tangential central diameter (T_D2). We also studied the relationship with the following growth traits: diameter at breast height (DBH), height (H), crown breadth south-north axis (NSC), crown breadth east–west axis (EWC), ring width (RW), latewood percentage (LWP), and wood density (WD). All sample materials were collected from a 33-year old clonal seed orchard of Pinus tabuliformis Carr. Genetic variation among clones was moderate for all tracheid traits, 9.49–26.03%. Clones significantly affected WT, R_D1, R_D2, T_D1, T_D2, and the two ratios WT/R_D1 and TL/T_D2 in EW but had no effects in LW. Clones significantly affected TL in LW but had no effects in EW. \( H\frac{2}{C} \) was higher in LW (0.50) than in EW (0.20) for TL, while \( H\frac{2}{C} \) was higher in EW (0.27–0.46) for other tracheid traits and the two ratios (TL/T_D2 and WT/R_D1) than in EW (0.06–0.22). WD and TL were significantly positively correlated, but WT and TL were negatively correlated both at individual and clone levels; all tracheid diameters and the four ratio values (EW_WT/R_D1, LW_WT/R_D1, EW_TL/T_D2 and LW_TL/T_D2), were strongly positively correlated with DBH, H, NSC, WEC and RW, and strongly negatively correlated with WD both at individual and clone levels. The most important variables for predicting WD were LW_TL, EW_WT and R_D1 in both EW and LW (r² = 0.22). Selecting the top 10% of the clones by DBH would improve DBH growth by 12.19% (wood density was reduced by 0.14%) and produced similar responses between EW and LW for all tracheid traits: a reduction of 0.94 and 3.69% in tracheid length and increases in tracheid diameters (from 0.36 to 5.24%) and double wall thickness (0.07 and 0.87%). The two ratios WT/R_D1 and TL/T_D2 across tissues (EW and LW) declined 0.59 and 4.56%, respectively. The decreased tracheid length and the ratio between tracheid length and diameter is disadvantageous for pulp production. The unfavorable relationship of tracheid traits with wood density indicate that multiple trait selection using optimal economic weights and optimal breeding strategies are recommended for the current long-term breeding program for P. tabuliformis.     

Growth responses to climate in a multi-species tree-ring network in the Western Carpathian Tatra Mountains, Poland and Slovakia

We analyzed growth responses to climate of 24 tree-ring width and four maximum latewood density chronologies from the greater Tatra region in Poland and Slovakia. This network comprises 1183 ring-width and 153 density measurement series from four conifer species (Picea abies (L.) Karst., Larix decidua Mill., Abies alba (L.) Karst., and Pinus mugo (L.)) between 800 and 1550 m a.s.l. Individual spline detrending was used to retain annual to multi-decadal scale climate information in the data. Twentieth century temperature and precipitation data from 16 grid-boxes covering the 48-50 degrees N and 19-21 degrees E region were used for comparison. The network was analyzed to assess growth responses to climate as a function of species, elevation, parameter, frequency and site ecology. Twenty ring-width chronologies significantly correlated (P<0.05) with June-July temperatures, whereas the latewood density chronologies were correlated with the April-September temperatures. Climatic effects of the previous-year summer generally did not significantly influence ring formation, whereas site elevation and frequency of growth variations (i.e., inter-annual and decadal) were significant variables in explaining growth response to climate. Response to precipitation increased with decreasing elevation. Correlations between summer temperatures and annual growth rates were lower for Larix decidua than for Picea abies. Principal component analysis identified five dominant eigenvectors that express somewhat contrasting climatic signals. The first principal component contained highest loadings from 11 Picea abies ring-width chronologies and one Pinus mugo ring-width chronology and explained 42% of the network's variance. The mean of these 12 high-elevation chronologies was significantly correlated at 0.62 with June-July temperatures, whereas the mean of three latewood density chronologies, which loaded most strongly on the fourth principal component, significantly correlated at 0.69 with April-September temperatures (P<0.001 over the 1901-2002 period in both cases). These groupings allow for a robust estimation of June-July (1661-2004) and April-September (1709-2004) temperatures, respectively. Comparison with reconstructions from the Alps and Central Europe supports the general rule of the dominant influence of growing season temperature on high-elevation forest growth.     

Genetic parameters for early wood and latewood densities and development with increasing age in Scots pine

? Each annual ring in pines consists of earlywood and latewood with considerable difference in density and width. To get a better determination of the genetic regulation of total wood density in Scots pine (Pinus sylvestris L.), density and width of those ring sections were measured in annual ring numbers 12 to 21 of Scots pines in a full-sib progeny test. Tree height and stem diameter were also measured.

? Heritabilities for the annual ring sections increased with age for earlywood density from 0.08 to approximately 0.25; latewood density showed similar reductions. Heritability over all 10 annual rings was 0.25 for earlywood density, 0.22 for latewood density, 0.29 for height and 0.10 for stem diameter. Genetic correlations between earlywood and latewood density and growth traits were negative, while they were strongly positive between densities of adjacent annual rings (0.70–1.0).

? Despite the higher heritability of earlywood density, the strong positive genetic correlation between those traits indicates little benefit from focusing solely on earlywood density when selecting for wood density. Analysing earlywood and latewood separately does not benefit from including the width of the corresponding ring section as a covariate. Juvenile wood may possibly turn into mature wood 15–20 y from the pith.

     

Statics and kinetics of water vapor sorption of small loblolly pine samples

A better understanding of the sorption behavior of different wood structures could be useful in protecting wood against wood deterioration and fungal attack. The purpose of this study was to investigate the effect of differences among earlywood, latewood, and tree ring location within the stem cross-section of loblolly pine (Pinus taeda) on the sorption kinetics and statics of water vapor under ambient conditions. The water vapor sorption of earlywood and latewood in different tree rings was recorded using a dynamic contact angle analyzer under relative humidity changes from 11 to 89%, as provided by saturated salt solutions. Earlywood had higher sorption rates and diffusion coefficients than latewood, while outer tree rings had higher sorption rates and diffusion coefficients than inner tree rings. The sorption isotherms of earlywood, latewood, and different tree ring locations within the stem cross-section were fitted very well by a Hailwood–Horrobin model.     

Cavitation in dehydrating xylem of Picea abies: energy properties of ultrasonic emissions reflect tracheid dimensions

Ultrasonic emission (UE) testing is used to analyse the vulnerability of xylem to embolism, but the number of UEs often does not sufficiently reflect effects on hydraulic conductivity. We monitored the absolute energy of UE signals in dehydrating xylem samples hypothesizing that (i) conduit diameter is correlated with UE energy and (ii) monitoring of UE energy may enhance the utility of this technique for analysis of xylem vulnerability. Split xylem samples were prepared from trunk wood of Picea abies, and four categories of samples, derived from mature (I: earlywood, II: 30-50% latewood, III: >50% latewood) or juvenile wood (IV: earlywood) were used. Ultrasonic emissions during dehydration were registered and anatomical parameters (tracheid lumen area, number per area) were analysed from cross-sections. Attenuation of UE energy was measured on a dehydrating wood beam by repeated lead breaks. Vulnerability to drought-induced embolism was analysed on dehydrating branches by hydraulic, UE number or UE energy measurements. In split samples, the cumulative number of UEs increased linearly with the number of tracheids per cross-section, and UE energy was positively correlated with the mean lumen area. Ultrasonic emission energies of earlywood samples (I and IV), which showed normally distributed tracheid lumen areas, increased during dehydration, whereas samples with latewood (II and III) exhibited a right-skewed distribution of lumina and UE energies. Ultrasonic emission energy was hardly influenced by moisture content until ～40% moisture loss, and decreased exponentially thereafter. Dehydrating branches showed a 50% loss of conductivity at -3.6 MPa in hydraulic measurements and at -3.9 and -3.5 MPa in UE analysis based on cumulative number or energy of signals, respectively. Ultrasonic emission energy emitted by cavitating conduits is determined by the xylem water potential and by the size of element. Energy patterns during dehydration are thus influenced by the vulnerability to cavitation, conduit size distribution as well as attenuation properties. Measurements of UE energy may be used as an alternative to the number of UEs in vulnerability analysis.     

Change in circularity index of cell lumen in a cross-section of wood induced by aqueous NaOH

We quantitatively examined changes in the morphological features of wood cells treated with aqueous NaOH and their relationship to changes in the micro-structure of wood components. Wood samples were treated with aqueous 0.00–0.20 (w/w) NaOH ([NaOH] = 0.00–0.20). Cross-sectional planes of samples were observed using confocal laser-scanning microscopy and the circularity index of cell lumens in cross-section was evaluated using digital image analysis. At [NaOH] < 0.11, the circularity index was unrelated to crystallinity, while at [NaOH] > 0.12 it was closely related to a decrease in crystallinity, as indicated by X-ray diffraction. Force balance analysis based on a cell model supported experimental results at higher concentrations. We concluded that cells appear circular in cross-section after treatment with NaOH because a decrease in crystallinity results in contraction along microfibrils, resulting in distribution of the central force of the three layers, S1, S2, and S3, in the secondary wall at the corners of cells in cross-section.     

Variations and correlations of various ring width and ring density features in European oak: implications in dendroclimatology

Summary Variations and correlations of various ring width and ring density features were analyzed in 18 European oak (Quercus petraea andQuercus robur) trees from northeastern France. In light of these analyses, the goodness of various tree-ring features as a climatic parameter was discussed. In general, ring density features (viz. earlywood density, latewood density, average ring density, minimum density and maximum density) show a stronger response to calendar year, a comprehensive climatic variable, than ring width features (viz. earlywood width, latewood width, total ring width and latewood percent). The response of latewood features (viz. latewood width, latewood density and maximum latewood density) is stronger than that of earlywood features (viz. earlywood width, earlywood density and minimum earlywood density). Average ring density seems to be the most sensible tree-ring feature in European oak in terms of the response to calendar year. Moreover, total ring width as a climatic parameter is not as good as latewood width, and maximum (latewood) density and minimum (earlywood) density appears not to contain as much climatic information as (average) latewood density and (average) earlywood density, respectively.This project was supported by the institut National de la Recherche Agromonique (INRA). Thanks are due to Dr. G. Nepveu for his constant encouragement and assistance during this study     

材性改良研究：Ⅰ.X射线木材密度测定

利用Ｘ射线衍射（Ｄ－ｍａｘ３Ｂ型）改装成直接扫描式Ｘ射线木材密度计，可快速、高效测定木材密度组成，即木材平均密度，平均早材密度，平均晚材密度，最大木材密度，最小木材密度，木材密度梯度和木材密度的变异幅度，为材性改良提供了新手段，本文用Ｘ射线木材密度计测定１７个树种木材密度。