Physiological basis of wood production: A review

The theoretical background to wood production is outlined and the factual background is given by reviewing measured rates of wood production. It is recommended that differences in wood production be analysed, not by statistical methods, traditional growth analysis or by comprehensive models, but by using a ‘light use analysis’, where wood production is determined by (1) the amount of light intercepted by the canopy, (2) the light use efficiency, net of respiration, (3) the proportion of assimilates partitioned to wood, and (4) mortality losses. These four components are discussed.     

Physiological effects in humans induced by the visual stimulation of room interiors with different wood quantities

To clarify the visual effects of room interior with wooden materials on humans, pulse rate, blood pressure, and brain activity were measured while the subjects were exposed to visual stimuli using actual-size model rooms. The wood ratios (the ratio of the area covered with wooden material to the whole area of the ceiling, walls, and floor) of the rooms were 0%, 45%, and 90%. Subjective evaluation was also conducted. In the 0% room, diastolic blood pressure decreased significantly, but the observed change in the autonomic nervous activity was relatively small. In the 45% room, a significant decrease in the diastolic blood pressure and a significant increase in pulse rate were observed. This room tended to have the highest scores in subjective “comfortable” feeling. The 90% room caused significant and large decreases in systolic blood pressure and diastolic blood pressure at the beginning of the test, but the large coverage of wood appeared to cause a rapid decrease in brain activity and an increase in pulse rate. The present study demonstrated that a difference in wood ratio in the interior caused different physiological responses, especially in the autonomic nervous activity, by using actual-size rooms for the first time.     

Duration of load effects of solid wood: A review of methods and models

Abstract

Test methods for studying the effect of long-term loading on the load-carrying capacity of structural wood are discussed. The impact of sampling procedures on test results is investigated and is exemplified. It is concluded from this investigation that the sampling method has a significant impact on the test results. A number of mathematical models for estimation of the effect of load duration are also presented and brief outlines of the theoretical background for five categories of models are given. No attempt is made to compare the models in order to nominate the best model. Effort is, however, made to illustrate the futility of calibrating models against one type of test when the model is redundant to the test type.     

Stand,stem and log segregation based on wood properties: a review

There are many log and wood properties of interest to wood processors. There is also high variability in important attributes between and within growing regions and between and within individual stems which influence financial returns to wood processors. This review summarises recent studies of segregation technologies and techniques which have shown that:

• regional or stand level attribute models will facilitate a coarse level of segregation but not account well for the between and within stem variation;

• many tools and techniques are available for segregating wood based on internal properties but few have been implemented commercially. Some are better suited for application in mills than in forests;

• the benefits of segregating stands, stems and logs based on wood properties are not clear due to high variability in wood properties, poor market signals (in terms of price) for wood with superior properties, and poor understanding of the costs across the value chain; and

• most of the existing economic models tend to look at the economics of segregation from the perspective of a single participant in the value chain, e.g. a structural mill or a central processing yard. Only a few models look across the value chain and these have limitations often poorly representing some participants in the value chain.

     

Swelling of acetylated wood II: effects of delignification on solvent adsorption of acetylated wood

To clarify the role of lignin in the affinities of acetylated wood for organic solvents, the effects of delignification on the solvent adsorption of acetylated wood were investigated. Acetylated wood meals rapidly adsorbed organic solvents that were hardly adsorbed by unmodified wood. For nonpolar and low-polarity organic solvents, a clear positive correlation was observed between the amount of adsorption and the lignin content. This indicated that acetylated lignin was responsible for the excellent affinities of acetylated wood for hydrophobic organic solvents. On the other hand, for lower alcohols and water, the amount of adsorption reduced with an increase in the lignin content. It was suggested that the adsorption of such polar solvents was dominated by insufficiently acetylated hydrophilic polysaccharides.     

Potential use of wood ash in South African forestry: a review

The use of landfills as a disposal method for wood ash is costly, environmentally detrimental and is pitted against increasingly stern environmental regulations. Literature has shown that wood ash has the potential to be used as a forest fertiliser and the effects tend to be highly site-specific. Wood ash contains a combination of carbonates, hydroxides and other calcium-containing minerals that are responsible for the liming effect observed following application to soils. In addition, it contains significant magnesium and potassium concentrations, but little nitrogen and sulphur. The phosphorus availability of wood ash varies considerably and in effect can limit soil phosphorus uptake and may affect subsequent nutrient balance in plants. Short-rotation forestry practices and whole-tree harvest systems can induce periodic or persisting nutrient deficiencies and acidify the soil. This may affect the ability of a site to sustain adequate nutrient levels over successive rotations. Utilising wood ash as a soil amendment can offset or correct some nutrient deficiencies and imbalances induced by intensively managed plantation forests. This review covers the international literature on ash applications to forest land, including the effect of ash-beds remaining after slash burning (as a useful analogy for the effects of wood ash on soil properties and tree growth). The results show that ash applications to forest land can be done safely and can potentially stimulate microbial activity and improve pine and eucalypt growth. Safe ash application rates should be determined after consideration of (1) soil buffer capacity and ash alkalinity (expressed as calcium carbonate equivalence) and (2) an evaluation of the concentrations of heavy metals existing in soils and present in the available ash, particularly from cadmium, chromium, lead and arsenic.     

Chemical modification of wood: A short review

Abstract

For most markets for wood, it is used without any treatments or modifications. When wood is used in adverse environments, it may be treated with chemicals to help prevent decay, improve water resistance, reduce the effects of ultraviolet radiation or increase fire retardancy. Many of these treatments involve the use of toxic or corrosive chemicals that can harm the environment. Chemical modification of wood provides an alternative by providing protection against water, decay, UV and thermal degradations by bonding chemicals to the cell wall polymers that do not leach out. Dimensional stability and decay resistance are two major properties that can be greatly improved by simple reactions with acetic anhydride.     

Chemical modification of wood: A short review

For most markets for wood, it is used without any treatments or modifications. When wood is used in adverse environments, it may be treated with chemicals to help prevent decay, improve water resistance, reduce the effects of ultraviolet radiation or increase fire retardancy. Many of these treatments involve the use of toxic or corrosive chemicals that can harm the environment. Chemical modification of wood provides an alternative by providing protection against water, decay, UV and thermal degradations by bonding chemicals to the cell wall polymers that do not leach out. Dimensional stability and decay resistance are two major properties that can be greatly improved by simple reactions with acetic anhydride.     

红外光谱技术在我国木材科学领域的应用研究进展

红外光谱法是分析化合物结构与化学组成的重要手段,该文综述了中红外与近红外光谱技术在木材物理与化学性质测试、木材种属分类与鉴定、木材加工领域、林木病虫害预测等木材科学相关方向的国内最新研究进展。今后应在推广红外光谱技术实践应用、方法标准提升、多技术联用等方面开展深入研究。     

Transient moisture effects on wood creep

To gain insight into the physical nature of the coupling between mechanical stress and humidity variations, the behaviour of thin wood strips was studied using specially developed apparatus for creep/recovery and relaxation/blotting-out tests in a controlled humidity environment. The load time and the rate of viscoelastic creep were found to have little influence on mechano-sorptive creep. Moreover, creep trajectory curves for specimens with continuous and interrupted humidity cycles indicated divergence from simple creep-limit behaviour. The effect of transient moisture was also modelled numerically at the molecular level using an idealized cellulose-based composite. Preliminary results suggest that: (i) during free shrinkage, the cellulose chains in elementary fibrils may bend perpendicular to the planes of the hydrogen bonded sheets which form the crystalline lattice; (ii) transient hydrogen bonding between the crystalline cellulose and amorphous polymer owing to the introduction or removal of water may accelerate shear slip between the two phases in the presence of an external load. Received 6 July 2000 The financial support of the Swiss Federal Office for Education and Science is gratefully acknowledged.     

Eucalyptus wood decay: effects on productivity and quality of cellulose

We evaluated the effect of wood decay, caused by fungi Hypoxylon spp., on pulp productivity and quality. Wood samples with different proportions of contamination (0, 25, 50, 75, and 100%) were used to produce Kraft pulp under the same pulping conditions. In the second step, cookings were performed to achieve the same Kappa number (Kn = 17 ± 1), varying only the alkali charge. Wood and pulp were also analysed by scanning electron microscope (SEM). The risk of occurrence of wood decay reached its maximum between September and October, under inappropriate storage conditions and juvenile wood without bark. It was observed that the increase in the decayed content (DC) of wood chips affected the Kappa number (Kn), according to the model Kn = 1/(0.0595?0.00324*DC^0.34102). An increase of 38.7% of alkali charge was necessary to reach the same Kappa number with decayed wood. The yield for the contaminated wood was lower (48%) when compared to non‐contaminated wood (53%). Once contaminated, the wood chips demand more severe cooking conditions because of the difficulty of impregnation. This condition affected the pulp quality, reducing its viscosity by 30% and hemicelluloses content by 5%. In addition, losses of resistance were also observed in the final pulp, where the zero span and tensile indexes were reduced by 5 and 16%, respectively. The SEM observations showed that the ascostroma fungi tissue was not totally degraded during the Kraft process, resulting in the deposition of pitch on fibres. Considering the results achieved, it was possible to conclude that the eucalyptus wood decay, caused by the fungi Hypoxylon spp., significantly affects the pulp process and quality.     

Duration-of-load and creep effects in strand-based wood composite: a creep-rupture model

In order to investigate the creep and duration-of-load (DOL) effects in thick strand-based wood composite products, a creep-rupture model is proposed linking the accumulated damage to creep deformation. Results from long-term constant load tests have been interpreted by means of this creep-rupture model, which is capable of representing the time-dependent deflection and time-to-failure data at different stress levels. The predictions of the model have been verified using results from ramp load test at different rates of loading. The creep-rupture model incorporates the short-term strength of the material, the load history and predicts the deflection history as well as the time-to-failure. As it is a probabilistic model, it allows its incorporation into a time-reliability study of wood composites’ applications.     

A review of wood thermal pretreatments to improve wood composite properties

The objective of this paper is to review the published literature on improving properties of wood composites through thermal pretreatment of wood. Thermal pretreatment has been conducted in moist environments using hot water or steam at temperatures up to 180 and 230 °C, respectively, or in dry environments using inert gases at temperatures up to 240 °C. In these conditions, hemicelluloses are removed, crystallinity index of cellulose is increased, and cellulose degree of polymerization is reduced, while lignin is not considerably affected. Thermally modified wood has been used to manufacture wood–plastic composites, particleboard, oriented strand board, binderless panels, fiberboard, waferboard, and flakeboard. Thermal pretreatment considerably reduced water absorption and thickness swelling of wood composites, which has been attributed mainly to the removal of hemicelluloses. Mechanical properties have been increased or sometimes reduced, depending on the product and the conditions of the pretreatment. Thermal pretreatment has also shown to improve the resistance of composites to decay.     

A review on natural products as wood protectant

Traditional wood protection methods employ chemicals that are considered toxic and can adversely affect human health and the environment. Fortunately, serious efforts are being made globally to develop alternative protection methods based on natural products with little or no toxicity, but the progress in implementation of the technologies has been slow because of certain limitations, including discrepancies between laboratory and field performance of natural products, variability in their efficacy related to exposure/environmental conditions, and legislation difficulties due to disagreements globally on setting standards defining the quality of their performance and use. The focus of this review is to present information on the natural compounds that have shown promise for wood protection, and the information is presented under defined interactive categories. In closing, some thoughts are presented on potential use of rapidly evolving technologies, such as nano- and gene-technologies that can lead to significant advances, particularly from the consideration of specificity of natural products and their economic value.     

Cultivation of shiitake in sugi wood meal II: effects of seasoning treatment for wood meal on mycelial growth

The effects of seasoning treatment for fresh sugi wood meal on the mycelial growth of shiitake was investi-gated. The mycelial growth of shiitake in sugi wood meal increased to the same level as that in extract-free sugi wood meal on the 12th day and to approximately 70% of that in konara wood meal on the 28th day of the seasoning treatment. A drastic decrease in extracts of fresh sugi wood meal occurred during the early stage of treatment, and the neutral fraction of methanol extracts decreased to less than 2%. The drainage of sugi wood meal media significantly increased during the later stage of treatment. No changes in the chemical components of sugi wood meal were detected during the seasoning treatment. The mycelial growth of shiitake in the fully seasoned sugi wood meal, which was prepared for commercial mushroom cultivation, was at almost the same level as that in the extract-free sugi wood meal. All of the seasoned sugi wood meals contained a neutral fraction of less than 1%. These results suggested that seasoning treatment can promote mycelial growth of shiitake in sugi wood meal by eliminating inhibitors and improving the physical properties of sugi wood.Part of this paper was presented at the 49th Annual Meeting of the Japan Wood Research Society, Tokyo, April 1999     

Physiological influences on wood-destroying insects of wood compounds and substances produced by microorganisms

Summary Wood-destroying insects react to and depend regarding their nutrition on compounds contained in wood or produced by microorganisms in wood. This relation is a complex matter in the biology of the insects and the chemistry of wood and of the metabolism of woodinhabiting microorganisms. Results on the reaction of Coleoptera and Isoptera to attractive or repellent compounds in wood species or substances produced by fungi in wood are reviewed with emphasis to differences among various insect species. Nutrition of wood-destroying insects depends on nitrogen compounds of the wood; the content of nitrogen can be increased by the presence of fungi. Existing results on the relation between microorganisms and insects are also summarized including toxicity or parasitic influence of part of the microorganisms on insects. The survey may stimulate further investigations which are necessary for better knowledge of the complex interrelations.Prepared for the Convention of the International Academy of Wood Science at Raleigh (S.-Carol., USA) in March 1971.