The use of an acoustic technique to assess wood decay in laboratory soil-bed tests

This study assesses the changes in elastic behaviour (i.e. modulus of elasticity – MOE) and mass loss of different hardwood and softwood species exposed to decay in laboratory soil-bed tests. Elasticity moduli were determined using conventional static methods as well as a dynamic method based on flexural vibration. The results obtained show a high correlation between dynamic and static bending measurements for all the timber species tested at different stages of fungal decay. Furthermore, the non-destructive MOE assessment proved to be a good tool for the early detection of wood decay. Received 5 January 1999     

Studies on the control of subterranean termites by inorganic pesticides

Studies on the wood preserving techniques against subterranean termites have been undertaken with a view to promote the use of inorganic indigenous pesticides in our country. The thin films of gelatine solution (glue of animal hides) containing 10% calcium carbonate or 5% copper sulphate as well as sodium silicate solution containing 12% calcium carbonate +10% zinc oxide coated separately on wooden stakes prevented termite attack in soil up to 2, 4 and 5 years, respectively. Whereas control wooden stakes were found to be severely damaged by termites within 6 months. Stakes coated with Solignum^®-white used as standard wood preservative for comparison remained free from termite infestation for a period of 5 years.     

Genetics of wood quality attributes in Western Larch

Context

Wood quality traits are important to balance the negative decline of wood quality associated with selection for growth attributes in gymnosperm breeding programs. Obtaining wood quality estimates quickly is crucial for successful incorporation in breeding programs.

Aims

The aims of this paper are to: (1) Estimate genetic and phenotypic correlations between growth and wood quality attributes, (2) Estimate heritability of the studied traits, and (3) Assess the accuracy of in situ non-destructive tools as a representative of actual wood density.

Methods

Wood density (X-ray densitometry), tree height, diameter, volume, resistance drilling, acoustic velocity, and dynamic modulus of elasticity were estimated, along with their genetic parameters, for 1,200, 20-year-old trees from 25 open-pollinated families.

Results

Individual tree level heritabilities for non-destructive evaluation attributes were moderate ( $ {\widehat{h}}_i^2=0.37-0.42 $ ), wood density and growth traits were lower ( $ {\widehat{h}}_i^2=0.23-0.35 $ ). Favorable genetic and phenotypic correlations between growth traits, wood density, and non-destructive evaluation traits were observed. A perfect genetic correlation was found between resistance drilling and wood density (r _G ?=?1.00?±?0.07), while acoustic velocity and dynamic modulus of elasticity showed weaker genetic correlations with wood density (r _G ?=?0.25?±?0.24;?0.46?±?0.21, respectively).

Conclusion

This study confirmed that resistance drilling is a reliable predictor of wood density in western larch, while the weak genetic correlations displayed by acoustic velocity and dynamic modulus of elasticity suggest limited dependability for their use as fast in situ wood density assessment methods in this species.     

木塑复合材料性能影响因素分析

采用无损检测方法和静压试验,对由不同物料配比所得到的木塑复合材料动态弹性模量和静态弹性模量性能指标进行了检测,并分析了不同因素对材料弹性模量的影响程度,从而获知各因素对材料性能影响的主次顺序。由相关性分析得知,动态弹性模量与静态弹性模量之间具有很强的相关性。     

Comparative effectiveness of two alkylammonium compounds as wood preservatives

This study describes a laboratory evaluation of the efficacy of two alkylammonium compounds [didecyldimethylammonium tetrafluoroborate (DBF) and didecyldimethylammonium chloride (DDAC)] when applied via vacuum impregnation or superficial treatment. Treated wood specimens were tested for their termite and microbial resistance under controlled laboratory conditions. The higher chemical retentions were needed to suppress the feeding by Coptotermes formosanus ≦3% mass loss in the multichoice test than in the no-choice test. The DBF and DDAC retention levels necessary to meet the performance requirement ≦3% mass loss after 12-week fungal exposure varied with wood species. The retention level of 3 kg/m³ for DBF and DDAC was generally high to keep the nondurable wood species free of decay. Although there was no difference between DBF and DDAC in the efficacy against decay and termite attack, the former slightly outperformed the latter as an antimold and antisapstain agent.     

薄板类中密度纤维板动静态弹性模量的检测

植物挥发物在植食性昆虫的寄主选择和产卵选择中起着重要作用(杜家纬,2001).薄板类中密度纤维板的弹性模量(MOE)是表征其力学性能的主要指标之一.传统都是采用简支静曲测试方法,该方法过程繁琐、消耗时间长(赵仁杰等,2003;Ross et al.,1998).依据振动法测定木质材料的力学性能,过去几十年来已经被证明是一种成功的方法(Moslemi,1967;Ross et al.,1994),测定结果显示振动法测得的力学性质与传统静态弯曲测得的弹性模量间有非常好的一致关系.     

Biological effectiveness of didecyl dimethyl ammonium tetrafluoroborate (DBF) against basidiomycetes following preconditioning in soil bed tests

Evaluation of wood preservatives in soil-contact tests is becoming an important issue since detoxification of wood-protecting compounds by fungi and bacteria found in soil may decrease the resistance of treated wood. In this study, the decay resistance of wood treated with didecyl dimethyl ammonium tetrafluoroborate (DBF), a recently developed quaternary ammonia compound, was evaluated in both soil bed and laboratory decay resistance tests. Small specimens (5×10×100 mm³) of DBF-treated and untreated sugi sapwood were subjected to decay in laboratory soil bed tests (DIN ENV 807 (2001)) followed by Basidiomycetes tests (DIN EN 113 (1996)). Exposure in field soil and compost soil substrates was used to observe the effects of wood degrading and other soil-inhabiting micro-organisms on the decay resistance of the specimens. Soil bed tests showed that DBF-treated wood specimens at 7.7 kg/m³ retention level (1% DBF solution concentration) showed better performance compared to 0.01 and 0.1% DBF treatments. The 7.7 kg/m³ retention level was also effective to protect the wood specimens against Coniophora puteana and Coriolus versicolor in Basidiomycetes tests. It is concluded that detoxification of wood preservatives in soil contact is an important factor to determine protective properties of treated wood in ground contact applications. Further experiments with larger specimens are needed to observe the performance of DBF-treated wood at higher retention levels in field above ground and ground contact tests. Dedicated to Prof. Dr. H.C. Mult. Walter Liese on the occasion of his 80th birthday.     

Evaluation of standing tree quality of Japanese cedar grown with different spacing using stress-wave and ultrasonic-wave methods

The quality of wood in 47-year-old standing trees of Japanese cedar grown in five plantation sites with different spacing (A, 1×1m; B, 2×2m; C, 3×3m; D, 4×4m; E, 5×5m) was evaluated using stress-wave and ultrasonicwave propagation methods. The magnitude of the velocities of these waves and the calculated dynamic modulus of elasticity (MOE) were used as indexes for assessing wood quality in standing trees. Results indicated that plantation spacings had moderate influence on the stress-wave and ultrasonic-wave velocities, and the degree of influence varied with the wave-propagating direction. Regardless of the testing method used, the velocities of waves propagated parallel to the grain in the standing trees with medium and poor growth conditions were significantly greater than those with superior growth conditions. The dynamic MOE of the trunk of standing trees of Japanese cedar was calculated by adjusting the effective mobility of free water and effective density in the trunk at various moisture contents. Results indicated that the dynamic MOE of wood in the standing trees of Japanese cedar was affected somewhat by the testing methods used. Furthermore, the dynamic MOE of the wood in the standing trees varied with the growth conditions imposed.Part of this report was presented at the World Conference on Timber Engineering, Montreax-Lausanne, Switzerland, August 17–20, 1998     

Tree growth performance and estimation of wood quality in plantation trials for Maesopsis eminii and Shorea spp.

Plantations of tropical species are becoming an increasingly important source of wood.However, it is important that research trials focus not only on tree growth performance, but also on wood quality.The aims of this study were to assess the growth performance of six commercially and ecologically important tree species from separate plantation trials in Indonesia and to determine the relationships between tree growth and wood quality in terms of the dynamic modulus of elasticity(MOE) and wood density.Forty-eight 7-year Maesopsis eminii Engl.and thirty-five 9-year specimens(7 each of 5 Shorea spp.)were selected from two trials.The MOE, based on acoustic velocity, was indirectly measured to evaluate wood stiffness.Tree-growth performance was evaluated, and correlations between growth traits and acoustic velocity as well as density and wood stiffness properties were estimated.The growth performance of M.eminii in terms of tree volume was significantly different in three different categories of growth(i.e.fast, medium, slow).Of the five Shorea spp.studied, Shorea leprosula Miq.had the highest growth rate, as expected since it is known to be a fastgrowing Shorea species.Indirect measurement of wood quality by means of non-destructive ultrasonic methods showed a weak negative correlation between tree volume and acoustic velocity and dynamic MOE.Although each fast-growing tree could reach a merchantable size faster than other varieties or species, wood traits of various species tested were not significantly different based on tree growth rate performance.The findings from this study could be used to improve selection criteria in future breeding trials; indirect measurements of the dynamic modulus of elasticity can be used in mass pre-selection of genetic materials, to choose the most-promising material for in-depth evaluation.     

Decay Detection of Ancient Wood Rafters in Tibet by Stress Wave Testing Method

Visual classification and stress wave non-destructive testing technology were adopted to evaluate the decay status of ancient Populus wood members （rafters） replaced from the Potala Palace. The decay status of wood members was evaluated by stress wave testing and visual observation. For most of the ancient wood members, the evaluation results by two methods were consistent with each other. Also stress wave testing techniques can find the internal wood member decay to eliminate the hidden hazard for ancient wood members, and offer relatively accurate quantitative information for the safety status of ancient wood members. Thus during the maintaining for ancient architectures, visual observation combined with stress wave testing techniques is a good way to evaluate the degradation of ancient wood members.     

Variation in selected solid wood properties of young Pinus patula from diverse sites in the Mpumalanga escarpment area in South Africa

Regression analyses identified ‘Growth Days’ (an index expressing site moisture availability) as the only site variable contributing significantly to the prediction to wood density (R² = 0.57), whereas the model predicting grain angle included only ‘Altitude’ (R² = 0.60). These results surfaced during an investigative study to quantify various sources of variation in wood properties and to quantify the effect of a number of site factors on wood properties of Pinus patula grown in the Mpumalanga escarpment area of South Africa. For this purpose, 10 trees were sampled from each of 17 diverse sites for wood property analyses. The effects of site, distance from the pith and differences between trees within site on wood density, transverse shrinkage, grain angle and dynamic modulus of elasticity were investigated. The site factors considered included a wide variety of soil and climatic factors. The effect of radial distance from the pith and differences between individual trees within sites were highly significant, accounting for most of the variation in wood properties. Although the effects of a number of site factors were statistically significant, they generally explained relatively small but important variation in wood properties among sites. The study not only quantified the effects of important sources of variation on a few key wood properties, but it also revealed that the extent of differences between sites can be explained in terms of some specific site factors. It is envisaged that the results will contribute significantly towards the refinement of current forest site classification systems for improved decision-making with respect to wood quality in intensively managed plantation systems.     

Decomposing stumps influence carbon and nitrogen pools and fine-root distribution in soils

Decomposing stumps could significantly increase soil resource heterogeneity in forest ecosystems. However, the impact of these microsites on nutrient retention and cycling is relatively unknown. Stump soil was defined as the soil fraction directly altered by the decomposition of the primary rooting system (e.g. taproots) and aboveground stumps. Study sites were located in mature hardwood stands within the Jefferson National Forest in the Ridge and Valley Physiographic region of southwest Virginia. The objectives of this study were to: (i) determine the total soil volume altered by the decomposition of stumps and underlying root system, (ii) compare and contrast total C and N, extractable ammonium (NH₄⁺) and nitrate (NO₃⁻), potentially mineralizable N, microbial biomass C (MBC), root length and root surface area between the bulk soil (i.e. O, A, B and C horizons) and stump soil and (iii) evaluate how nutrient concentrations and fine-root dynamics change as stumps decompose over time using a categorical decay class system for stumps. Potentially mineralizable N was 2.5 times greater in stump soil than the A horizon (103 mg kg⁻¹ vs. 39 mg kg⁻¹), 2.7 times greater for extractable NH₄⁺ (16 mg kg⁻¹ vs. 6 mg kg⁻¹) and almost 4 times greater for MBC (1528 mg kg⁻¹ vs. 397 mg kg⁻¹). Approximately 19% of the total fine-root length and 14% of fine-root surface area occurred in the stump soil. Significant differences occurred in C and N concentrations between all four decay classes and the mineral soil. This validated the use of this system and the need to calculate weighted averages based on the frequency and soil volume influenced by each decay class. In this forest ecosystem, approximately 1.2% of the total soil volume was classified as stump soil and contained 10% and 4% of soil C and N. This study illustrates that including stump soil in soil nutrient budgets by decay class will increase the accuracy of ecosystem nutrient budgets.     

Serial exposure technique for assessing performance of wood preservatives

Summary The performance of copper-chrome-arsenate (CCA) and two quaternary ammonium compounds as wood preservatives was compared using a serial exposure technique, involving successive 10-week exposures in conventional soil jars. All preservative treatments were successful in preventing decay of Pinus radiata sapwood after the first exposure, but successive 10-week exposures clearly distinguished those treatments likely to offer long-term protection. The progressively increasing times of exposure with test fungi overcame the time lag for decay initiation in wood treated to preservative retentions above the toxic threshold established by conventional laboratory methods. Consequently, an additional and higher toxic threshold could be calculated. Examination of data from field stake tests suggested that a series of toxic thresholds established by a serial exposure technique could be related to preservative retentions which protect wood in the field from decay for increasing periods of time. Results of all tests are discussed in relation to the development of a laboratory procedure which may predict field performance of wood preservatives.     

Using drill resistance to quantify the density in coarse woody debris of Norway spruce

To evaluate the mass of coarse woody debris (CWD), it is necessary to quantify its density. Drill resistance measurements are introduced as a approach to estimate the density of CWD in different stages of decay. Dead logs of Norway spruce [Picea abies (L.) Karst.] from a Central European mountainous site were used as a test system to compare the new method with conventional predictors of wood density such as fast quantitative field estimates (e.g., knife probe) and classification of decay classes based on a set of qualitative traits and quantitative estimates. The model containing only drill resistance as a predictor explained 65% of the variation in wood density and was markedly better than models containing one or more of several conventional predictors. However, we show that the relationship between drill resistance and gravimetric wood density relationship is sensitive to the decay status. Therefore, the best model combines drill resistance and decay class (adj. R2 = 0.732). An additional experiment showed that drill resistance is also sensitive to the moisture state (fresh vs. oven-dry) of the sample. The major potential of the method lies in its non-destructive nature which allows repeated sampling in long-term ecosystem studies or in protected areas where destructive sampling is prohibited. The limitations of the method are discussed and recommendations for applications are given.     

Characterization of host–fungus interactions among wood decay fungi associated with Khaya senegalensis (Desr.) A. Juss (Meliaceae) in Singapore

Tree pruning creates wounds that are amenable for wood decay fungi colonization. To characterize the dynamic host–fungus interactions at this location in Senegal mahogany (Khaya senegalensis), in vitro and in vivo pathogenicity tests were conducted with wood decay fungi associated with this tropical tree species. Fomitiporella caryophylii, Hymenochaete murina and Phellinus noxius isolates were included in this experiment following their frequent isolation from Senegal mahogany pruning wounds. The evaluated isolates demonstrated unique host interactions in laboratory tests that suggest equally divergent prognoses for living Senegal mahoganies affected by these fungi. Although all evaluated fungal isolates successfully breached naturally induced reaction zones, P. noxius alone caused significant mass loss to incubated wood blocks. In addition, P. noxius caused extensive wood decay after inoculation in living hosts, successfully illustrating Koch's postulates for this host–fungus relationship. The wood decay ability, invasiveness and facultative parasitism demonstrated by P. noxius suggest its dominant role in wood decay columns below pruning wounds on living Senegal mahoganies. These results highlight the importance of characterizing specific host–fungus interactions and their implications for wood decay severity below pruning wounds in living trees.     

Assessment of resonance wood quality by comparing its physical and histological properties

The quality of wood used for music instrument making (resonance wood) is determined by assessing six physical properties: density, modulus of elasticity, sound velocity, radiation ratio, emission ratio, and loudness index. This can easily be done by means of measurements of the resonance frequency and the corresponding damping factor. The method described here is based on vibrational analyses, adapted from standard non-destructive testing of solid material, so as to provide information both for scientific studies and for violin making. The above six properties were assessed in samples of resonance wood of different quality and in normal (control) wood of Norway spruce and sycamore. The differences observed between the samples correlated with anatomical or histological characteristics of the wood. A sample of best-quality Norway spruce resonance wood showed a high radiation ratio in the axial direction, which correlated with the presence of small wood cells with thin cell walls. In “curly maple”, a high sound velocity in the radial direction correlated with the presence of broad xylem rays. The influence of external factors like wood moisture content or the geometry of the system is discussed within the context of the present study.     

Comparative study on three dynamic modulus of elasticity and static modulus of elasticity for Lodgepole pine lumber

The dynamic and static modulus of elasticity （MOE） between bluestained and non-bluestained lumber of Lodgepole pine were tested and analyzed by using three methods of Non-destructive testing （NDT）, Portable Ultrasonic Non-destructive Digital Indicating Testing （Pundit）, Metriguard and Fast Fourier Transform （FFT） and the normal bending method. Results showed that the dynamic and static MOE of bluestained wood were higher than those of non-bluestained wood. The significant differences in dynamic MOE and static MOE were found between bulestained and non-bluestained wood, of which, the difference in each of three dynamic MOE （Ep. the ultrasonic wave modulus of elasticity, Ems, the stress wave modulus of elasticity and El, the longitudinal wave modulus of elasticity） between bulestained and non-bluestained wood arrived at the 0.01 significance level, whereas that in the static MOE at the 0.05 significance level. The differences in MOE between bulestained and non-bluestained wood were induced by the variation between sapwood and heartwood and the different densities of bulestained and non-bluestained wood. The correlation between dynamic MOE and static MOE was statistically significant at the 0.01 significance level. Although the dynamic MOE values of Ep, Em, Er were significantly different, there exists a close relationship between them （arriving at the 0.01 correlation level）. Comparative analysis among the three techniques indicated that the accurateness of FFT was higher than that of Pundit and Metriguard. Effect of tree knots on MOE was also investigated. Result showed that the dynamic and static MOE gradually decreased with the increase of knot number, indicating that knot number had significant effect on MOE value.     

Influence of initial planting spacing and genotype on microfibril angle,wood density,fibre properties and modulus of elasticity in Pinus radiata D. Don corewood

Pinus radiata D. Don trees from six clones, grown at initial spacings of 2500 stems ha⁻¹ and 833 stems ha⁻¹ were destructively harvested. For these trees wood properties were measured on radial slices sampled at a height of 1.4 m above the ground. Relative to wide spacing, close initial stand spacing significantly reduced microfibril angle (MFA) and ring width and significantly increased dynamic modulus of elasticity (MOE), fibre length, latewood percentage and cell wall thickness. Density and fibre width were not significantly different between spacing treatments. Examination of the influence of genetic population on wood properties indicated that genotype significantly influenced MFA, MOE and ring width. The key wood properties MFA, MOE and fibre length were regressed against tree diameter, height and stem slenderness. All three wood properties were most strongly correlated with stem slenderness. Multiple regression models developed for MFA, MOE and ring width accounted for respectively 62%, 81% and 58% of the variation in these variables. The following changes occurred in sampled properties with increasing ring number: MFA and ring width declined markedly; MOE and fibre length increased markedly; latewood percentage and cell wall thickness increased slightly; and density and fibre width did not show any radial trend.     

Non-destructive assessment of <Emphasis Type="Italic">Pinus</Emphasis> spp. wafers subjected to <Emphasis Type="Italic">Gloeophyllum trabeum</Emphasis> in soil block decay tests by diffuse reflectance near infrared spectroscopy

The use of calibrated near infrared (NIR) spectroscopy for measuring and predicting the advancement of wood decay in Pinus spp. sapwood wafers that were subjected to Gloeophyllum trabeum for periods ranging from 1 to 10 days was investigated. NIR spectra were obtained from the center of the cross-sectional face of each sample before and after decay tests. Mass loss and compression tests were also used to measure the progression of decay. Calibrations were created from NIR spectra, mass loss, and compression strength data using untreated and mathematically treated (multiplicative scatter correction and first and second derivative) spectra. Strong relationships were derived from the calibrations with the strongest R ² values being 0.98 (mass loss) and 0.97 (compression strength). Calibrations for mass loss showed the strongest statistics for predicting wood decay of a separate test set (0.85 raw, second derivative to 0.76 multiplicative scatter correction (MSC), while predictions for compression strength of the decayed samples resulted in R ² of 0.69 (raw) to 0.54 (MSC). Calibrations created from the amount of time the samples were decayed showed strong statistics, indicating that NIR spectroscopy can predict the early stages of wood decay.     

Properties of flat-pressed wood plastic composites as a function of particle size and mixing ratio

This paper presents the effects of particle size and mixing ratio on the properties including physical, mechanical, and decay resistance of wood plastic composites (WPCs). In addition, it also presents the effects of immersion temperatures on water absorption (WA) and thickness swelling (TS) of the WPCs. WPCs with a thickness of 6 mm were fabricated from Albizia richardiana King & Prain wood particles and recycled polyethylene terephthalate (PET) by the flat-press method. To prepare the WPCs, two different wood particle sizes (0.5–1.0 and 1.01–2.0 mm) were used along with four different mixing ratios (w/w). Subsequently, the physical properties include density, moisture content, WA, and TS, and mechanical properties include modulus of elasticity (MOE) and modulus of rupture (MOR) of the produced WPCs was evaluated. Furthermore, decay resistance was evaluated by the weight loss percentage method. Moreover, the effects of immersion temperatures on WA and TS of WPCs after 24 h of immersion in water at three different temperatures, i.e., 25, 50, and 75 °C were investigated. Results showed that the wood particle size had impact on WPC’s density (only 6% decreased with the increase of particle size); however, the density decreased by 29% when the wood particle content increased from 40 to 70%. The WA and TS gradually increased with the increase of particle content and decrease of particle size. In addition, WA and TS increased proportionately with increasing immersion temperature from 25 to 75 °C. Furthermore, the highest MOE (2570 N/mm²) was found for the WPCs fabricated from large wood particles having the ration of 50:50 (wood particle:PET). For decay resistance, WPCs consisted of larger particles and higher PET content showed greater resistance against decay. Therefore, it is comprehensible that fabrication of the WPCs from 50% large particles and 50% PET is technically feasible and further improvement of WPC performance like enhancement of MOE and reduction of density using coupling agent and agricultural waste fibers, respectively, in the WPC formulation is recommended.