Volume 58, Issue 2

Lignin content and composition are important traits in several tree breeding programs, but very little is known about their natural variation. This study compares the lignin content in 1-year-old plants and 9-year-old trees of Norway spruce belonging to the same full-sib families. It is shown that the lignin content, according to the modified acetyl bromide method, does not vary significantly within or among the different full-sib families either as plants or as young trees. There is, however, on average 4.0% higher lignin content (31.4% versus 27.4%) and lower standard error for the trees than for the plants. The number of C9-units g −1 lignin, analyzed by thioacidolysis, ranges from 516 to 1186 μmmol C9-units g −1 lignin in plants and from 716 to 953 μmmol C9-units g −1 lignin in trees, with no significant differences among the families. However, the extent of change in C9-units g −1 lignin varies among the families with age. The ratio of erythro and threo stereoisomers does not vary significantly among the families. However, the ratio changes differently with age among the families similar to the C9-units g −1 lignin. Additionally, the content of p -hydroxyphenyl (H) lignin is 0.6% higher in the trees than in the plants (1.4% versus 0.8%), estimated indirectly from GC-MS data by a novel subtractive technique, indicating a higher degree of compression wood in the young trees. In conclusion, the amount and composition of lignin does not vary within or among the families at the same age. However, the amount of lignin increases with age while the change in lignin composition varies between family and age.

The effect of lignin-biopolymer structure on the mechanism of its oxidative depolymerization by polyoxometalates (POMs) was investigated by reacting an equilibrated POM ensemble with a series of ring-substituted benzyl alcohols. Under anaerobic conditions in mixed water/methanol, observed pseudo-first order reaction rates (150°C) of 8.96 × 10 −3 and 4.89 × 10 −3 sec −1 were obtained for oxidations of 1-(3,4-dimethoxyphenyl) ethanol ( 1 ) and 1-(3,4,5-trimethoxyphenyl)ethanol ( 2 ), respectively. Organic products from the oxidation of 2 (95% recovery) indicate the reaction proceeds via successive oxidations of the benzylic carbon atom; aromatic-ring cleavage was not observed. A primary kinetic-isotope effect of 1.6 and 1.7 was observed for the reactions of 1 and 2 deuterated at the benzylic-carbon atoms. This combined with the relatively large activation energies, indicate that C-H bond breaking (either H-atom or proton-coupled electron transfer) occurs late along the reaction coordinate of the rate-determining step. Replacing the 4-CH 3 O-group in 2 by CH 3 CH 2 O- to give 1-(4-ethoxy-3,5-dimethoxyphenyl)ethanol ( 3 ), had a substantial effect on the temperature dependence of the observed reaction rate, suggestive of a possible change in mechanism.

This paper reports on the influence of independent variables in the ethylene glycol/soda pulping of olive wood trimmings (165–195°C, 30–90 min, ethylene glycol concentration 5–15%, soda concentration 2.5–7.5% and liquid/solid ratio 4–6), on the yield and Kappa index of the pulps and the strength properties (breaking length, burst index and tear index) of paper sheets. By using a central composite factorial design, equations that relate each dependent variable to the different independent variables were obtained which reproduced the experimental results for the dependent variables with errors less than 12%. Using a temperature of 184°C, ethylene glycol and soda concentrations of 15% and 7%, respectively, a liquid/solid ratio of 5:1 and a cooking time of 30 min results in yield, Kappa index, breaking length, burst index and tear index values that depart by 14.3%, 8.2%, 17.1%, 17.0% and 2.3%, respectively, from their optimum levels. These conditions result in substantial savings in power consumption and immobilised capital investments as they involve a lower temperature, a lower liquid/solid ratio, and a shorter time than the maximum values tested.

This paper demonstrates the applicability of cooperativity analysis for the glass transition of lignin in wood. In ethylene glycol plasticized wood, the coupling model of relaxation proposed by Ngai allows for quantifying intermolecular coupling associated with the lignin glass transition. The method utilizes Time-Temperature Superposition of viscoelastic properties measured by submersion dynamic mechanical analysis. It is shown that the coupling model by Plazek and Ngai adequately describes segmental relaxation above the lignin glass transition temperature only. No significant difference in intermolecular coupling was found between spruce and yellow-poplar.

This work calculates the parameters that can be fitted to experimental data on compressive tests of selected softwoods and hardwoods. The woods were subjected to temperatures between 0°C and 100°C during severe radial compression. The parameters of m, c and k under the different conditions can be expressed by a constitutive equation. For most woods, parameter k (related to the Poisson's ratio) is approximately 1 except for Carpinus tschonoskii Maxim (inushide) and Aesculus turninata Blume (tochinoki). Parameter m ranges between 0.8–1 except for Pinus densiflora Seib. et Zucc. (akamatsu pine) (1.2–1.6) and Pinus elliottii Engelm (slash pine) (from 2.1 down to 1.8). Parameter c ranges between 0.2–1.5 depending on the viscoelastic properties of the cell wall for both hardwood and softwood.

Moisture content profiles with high spatial pixel resolution, 21 μm, were measured in Scots pine heartwood while drying from wet conditions to near equilibrium in the surface layer, (0–300 μm). The measuring technique used was Magnetic Resonance Imaging. In order to obtain magnetic resonance profiles with a high pixel resolution at both high and low moisture contents, a highg-radient permanent magnet was used. The results presented show one-dimensional moisture content profiles and mean moisture content development in the surface layer. In Scots pine heartwood, almost flat moisture content profiles were observed when the moisture content was above the fibre saturation level. When the mean moisture content in the surface layer decreases to the fibre saturation level, gradients start to build up from the surface towards the bulk of the sample although the bulk moisture content is far above the fibre saturation. Furthermore, the results presented in this study imply that a dry shell forms in the surface layer shortly after drying has begun. This dry shell controls the drying rate until the mean moisture content in the bulk decreases to the fibre saturation level.

The influence of temperature on the modulus of elasticity (MOE) and on the flexural stiffness of Pinus sylvestris L. was determined under temperature conditions ranging from 25 to 300°C for samples with a water content of about 6.0%. The experiments were carried out on microsamples, with a thermomechanical analyser, in isothermal conditions and under temperature ramping rates. The behaviour of the curves of the MOE is explained by wood drying and by the behaviour of the wood polymers as a function of temperature. The results obtained by thermomechanical analysis were validated by the results obtained by centre-point bending tests on small scale samples, which therefore allows for its use in modelling the behaviour of timber structures during a fire.

A method to determine the internal stress state across the grain of glued laminated wood (glulam), as well as the experimental equipment for measuring released deformation are described in this paper. The internal stress state is calculated from measured released deformations, which are measured by a contact free method based on a digital camera technique. Non-destructive measurement of the modulus of elasticity in the cross-grain direction is presented and the correlation between dynamic and static modulus of elasticity is shown. Results for a single specimen with induced moisture gradient show that the largest stress found in the tests was about 0.57 MPa, which is higher than the characteristic value of tensile strength perpendicular to the grain. This stress is based on released strain over the total length of the slices cut from the specimens. FEM-simulations evaluating the stress distribution within the specimen to account for end effects indicate that the maximum stress is about 30% higher.

Results are presented from an experimental investigation to determine internal stress states perpendicular to grain in glulam induced by moisture variations. The stresses are determined by measuring the released strains before and after cutting. Stress distributions are determined for specimens seasoned in constant humidity, specimens exposed to an artificial single climate change, specimens exposed to cyclic climate change and for specimens exposed to natural climate outdoors under shelter. Results for seasoned specimens show that internal stresses exist in glulam without the presence of moisture gradients. Stresses in specimens with an induced moisture gradient become larger when moistening from a specific climate A to another climate B than when drying from B to A. Tests in an outdoor sheltered climate show large variations in strains and stresses. The tensile stress level in the inner part of the glulam cross section exceeds the characteristic strength of 0.5 MPa during a period of approximately 80 days.

The microfibril angle of the S 2 layer in wood fibres is an ultra-microscopical feature that influences important properties affecting the utilisation of timber. However, this characteristic is as yet little studied, and this is especially true of the genus Eucalyptus . The microfibril angle of the S2 layer of the secondary wall was measured in fibres taken from eight-year-old trees of 11 Eucalyptus clones growing in four sites in Brazil. The overall mean microfibril angle measured was 8.8°. While the angle seemed to decrease slightly from pith to bark in a non-linear fashion, this decrease was not statistically significant. The microfibril angle showed statistically significant differences between sites and between clones, although the broad sense heritability of the microfibril angel was low (h 2 =0.293). Various theories attempt to explain the microfibril orientation, but we conclude that environmental stresses play an important role in defining the angle in Eucalyptus wood.

Moisture dynamics and durability during weather exposure as affected by origin and production method were studied for nine years on 113 untreated spruce samples. The moisture content was measured on 67 occasions. The weight loss was determined for each sample at the end of the sampling period. The most important factors, affecting both moisture content and weight loss, were origin and drying technique. The samples originating from central Sweden had the best durability, followed by the southern stand, while the northern stand had the lowest durability in terms of weight loss. Air-drying had a negative impact on the performance of samples from all three stands, but to different degrees. Samples from the northern stand were most sensitive to air-drying, in terms of both weight loss and moisture content, followed by the southern stand, while the central stand was least sensitive. Why the samples from the northern stand were more sensitive to air-drying and showed the largest weight losses is unknown; it can only be suggested that the origin of the wood can be of importance for the durability.

This is the first of a three-paper series that reports on the abundance, identity, and diversity of microorganisms isolated from dead-stacked yellow-poplar lumber in four time periods during the spring and summer of 2000. This paper focuses on filamentous fungi. Over the entire period, a total of 427 fungal isolates were obtained and 14 species representing 12 genera were identified. Nearly 15% of the fungal isolates were not identified. In total, fungal colonies accounted for 41% of the total abundance of microorganisms that were isolated from samples during this entire study. Penicillium implicatum and Aspergillus versicolor were the predominant fungal species identified and accounted for 29.7% and 14.5%, respectively, of the total fungal isolates. Penicillium sp was the most commonly isolated genera. Other fungi isolated at lower frequencies include Graphium penicilliodes , Cladosporium cladosporioides , Trichoderma harzium , Alternaria alternata , A. tenuissima , Epicoccum purpurscens , Hormoconis resinae , Fusarium monoilforme , Geotrichum sp, Chaetomium globosum , and Exophiala jeanselmi .

This paper reports on the identity and frequency of isolation of bacteria colonizing freshly-sawn (green) yellow-poplar lumber dead-stacked for 60 days in spring and summer of 2000. Total abundance of bacteria comprised 43% of the total population of isolated microorganisms and 14 different species of bacteria were identified. Bacillus sp was the predominant species and accounted for 42% of the total bacteria positively identified. Abundance of bacteria on each sampling date increased with increasing average ambient temperature in the period leading up to sampling.

Antifungal activity of constituents from the heartwood of the Malaysian Gmelina arborea against Trametes versicolor and Fomitopsis palustris was investigated. A sensitive bioassay system for antifungal activity against basidiomycetes was developed which uses a medium in which homogenized hyphae were dispersed. Ethyl acetate- solubles from the heartwood showed the highest activity against both fungi, although the activity against F. palustris was quite weak. Spots exhibiting antifungal activity against T. versicolor were specified by autobiography of ethyl acetate-solubles, and five constituents were isolated and identified as (+)-7′- O -ethyl arboreol, (+)-paulownin, (+)-gmelinol, (+)-epieudesmin and (−)-β-sitosterol. The four lignans showed antifungal activity, whereas β-sitosterol did not. From the comparison of antifungal activity, it was concluded that the piperonyl nucleus contributed to the activity of lignans. Of the four lignans isolated, gmelinol appeared to be an important antifungal constituent, since it was rich in the heartwood of G. arborea . Furthermore, the synergism by coexistence of these five compounds was confirmed.

This paper describes an experiment to identify volatile organic compounds (VOCs) from a range of three bacteria and one yeast strain that had previously been shown to be inhibitory to selected sapstain fungi. The bacteria and yeast were cultured on two media, malt extract (ME) and tryptone soya (TS) and the VOCs trapped on chromatographic adsorbant before being analysed by Integrated Thermal Desorption—GC-MS. Since sapstain fungi were only inhibited by VOCs produced on the TS media, it was possible to use Principle Component Analysis to highlight the individual VOCs that are most likely to be responsible for the inhibition. A number of ketones together with dimethyl disulphide and dimethyl trisulphide were highlighted. The importance of VOC production by organisms during the biological control of sapstain is discussed.

We have approached species identification of wood decay fungi in construction wood by means of sequencing ribosomal DNA. Sequencing of the Internal Transcribed Spacer (ITS), which includes the 5.8S rDNA, is straightforward and provides a basis for species identification. Identification was either by BLAST search on sequences in GenBank or phylogenetic analysis. A number of important wood decay fungi such as Serpula lacrymans, S. himantioides, Antrodia serialis, A. sinuosa, Gloeophyllum sepiarium, Fomitopsis pinicola, Resinicium bicolor and Junghuhnia collabens have been successfully identified from fruitbodies and directly from wood samples. Sequence variants were found within the species sampled including S. himantioides , the close relative of S. lacrymans. But, among 27 samples from fruitbodies and mycelium of S. lacrymans , unexpectedly, no sequence variation was detected.

The effect of wood/plastic ratio and the presence of a boron compound on resistance to biodegradation of wood plastic composites (WPC's) by the brown rot fungus Gloeophyllum trabeum was investigated in a soil block exposure. Weight losses of all WPC's were generally lower than those of solid wood, even when only the wood component of the WPC was used in calculating weight loss. Higher wood content was associated with greater weight losses, suggesting that the plastic encapsulated wood at lower wood levels. Borates markedly reduced weight losses at all wood/plastic ratios. Weight losses tended to be slightly lower with a Na/Ca borate than with similar levels of zinc borate. Mechanical properties did not correlate well with weight losses under the conditions evaluated, but these effects may have been masked by moisture sorption. The causes and implications of these differences are discussed.