The state of China's ecological environment has improved to some extent since the Chinese government initiated the Natural Forest Protection Program (NFPP) in 1998. The logging prohibition and limitation policies adopted by the NFPP, however, have reduced domestic timber supply. Together with the thriving economy, decreasing domestic timer supply continues to widen the gap between supply and demand. Importation is considered to be the primary solution to this issue, making China the world's largest timber importer. China's major timber suppliers are Russia, Malaysia, Papua New Guinea, New Zealand, and Gabon, among which Russia accounts for more than 61 percent of China's total timber imports. The relatively cheaper conifers imported from Russia account for more than 60 percent of all imported timber, with volumes continually increasing because of the rapid pace at which China has been implementing its infrastructure projects. In addition, as living standards continue to improve, requirements for home decor and furniture also grow, further increasing the demand for tropical to temperate timber. In the long term, imports will remain the main solution to the insufficient domestic timber supply in China.

The influence of the lunar phase of tree felling on the properties of wood has been debated for centuries, but it is only recently that it has been the subject of rigorous study. These scientific studies have essentially focused on softwoods, leaving unanswered the question of whether hardwoods follow the same pattern.

This article presents the results of the analysis of the lunar influence of the felling date on the humidity, specific weights, and shrinkage of wood. The random sample analyzed consists of 60 oaks (Quercus humilis Mill.) felled during the four lunar phases (15 trees per phase) throughout one lunar period. No significant differences were detected in any of the cases.

The production cost of lumber is a key factor when determining the price of logs at a sawmill gate. Some of the production costs are also manageable elements in price setting. There is a lack of exact knowledge of how the costs really act when some factor of production varies. This study introduces an activity-based costing (ABC) method for a large-scale sawmill that produces approximately 200,000 m³ of sawn lumber annually. Production processes were identified and their cost structures were analyzed in detail. The identified processes were log receiving, unloading and log sorting, log debarking, sawing and edging, green sorting and stickering, drying, quality sorting, and packing and storing with shipping. Resources, activities, and cost drivers were defined for each process. Sensitivity and applicability of the costing model were analyzed with two case studies in a virtual sawmill. Results indicate that the sawing pattern is an important variable in the production cost formation: a 16 percent decrement in the volume of sawn lumber led to a 4.5 percent cost reduction with the same log distribution. The findings of this study support the ABC method being a useful tool in controlling cost at a sawmill and a cost structure of a sawmill having an effect on the logistic chain of timber procurement.

The least-cost lumber grade mix solution has been a topic of interest to both industry and academia for many years due to its potential to help wood processing operations reduce costs. A least-cost lumber grade mix solver is a rough mill decision support system that describes the lumber grade or grade mix needed to minimize raw material or total production cost (raw materials plus processing cost). Because raw material costs in typical rough mills comprise 40 to 70 percent of total rough mill manufacturing expenses, the least-cost lumber grade mix problem, as it is referred to, is important.

An existing second-order polynomial least-cost lumber grade mix model integrated into the US Department of Agriculture (USDA) Forest Service's rough mill simulator, ROMI-3.0, which uses SAS 8.2 for statistical calculations, was used for the research described in this article. For this existing model, the USDA Forest Service purchased a SAS server license to allow free use of the software to least-cost lumber grade mix users via the Internet. Several issues around this rather involved setup necessitated the search for an alternative, local solution for the statistical computations. The open source statistical package R 2.7.2 was tested to see if it is an equivalent replacement for SAS 8.2. Comparisons of the SAS-based and a newly developed R-based least-cost lumber grade mix solver indicate no statistically significant difference between the two decision support systems. Therefore, the new R-based least-cost lumber grade mix solver was incorporated into ROMI-3.0. Thus, rough mill operators now have a new version of ROMI-3.0 with the integrated least-cost lumber grade mix solver at their disposal that does not require their computers to communicate with an outside server.

Various factors and propagation trends of stress waves in cross sections of wood need study to improve accuracy in the quality evaluation of wood and decay detection in standing trees. In this study, a Fakopp Microsecond Timer was used to measure the stress wave transmission time of Euphrates poplar (Populus euphratica Oliv.). Velocity was calculated to find the trend and make wavefront maps of stress waves. Results indicated that stress waves travel fastest in the radial direction and that velocity decreased as the angle between the two sensors increased. Velocity also increased as the number of annual rings increased. At the same time, the velocity in normal wood was higher than it was in tension wood, and it gradually increased in normal wood as the radial distance increased from pith to bark. Different influences on the stress wave propagation in wood were found when holes were made in the center of a cross section. Velocity showed little change with the increase in hole diameter when the angle between impacting and receiving sensors was 90°. At 180°, velocity was affected by hole diameter and rapidly decreased. Successful simulated wavefront maps of stress waves in cross sections of sound, hole, crack, and decay wood using two-dimensional contours were made. Three-dimensional maps were also reconstructed using Kriging interpolation and showed high similarity between cross sections.

Although higher treatment pressures have the potential to improve preservative penetration, higher pressures may possibly result in greater reduction in mechanical properties. The present study evaluated the effect of treatment pressure on the treatment quality and mechanical properties of red pine (Pinus resinosa Ait.) lumber. End-matched sections of red pine lumber were treated with an ethanolamine copper preservative at pressures of 1,207 kPa (175 psi), 1,379 kPa (200 psi), or 1,551 kPa (225 psi). Preservative uptake and penetration were measured, and small clear specimens were subsequently cut from the specimens for evaluation of bending properties. The average percentage of sapwood penetration increased slightly with increasing pressure, and this difference was statistically significant between the 1,207-kPa (175-psi) and 1,551-kPa (225-psi) pressures. In comparison to untreated specimens, treatment at all pressures caused small reductions in modulus of rupture and work to maximum load. However, there were no significant differences in bending properties between the pressures evaluated, indicating that higher pressures can be used without additional sacrifice of wood properties. These treatments were conducted at ambient temperature, and the findings do not necessarily apply to treatments conducted at elevated temperatures.

Pinus radiata specimens at a moisture content of 10 to 12 percent were heat treated at temperatures of 160°C, 180°C, and 210°C in commercial-grade raw linseed oil. The end-matched treated and untreated wood was exposed to an accelerated UV weathering environment for 2,100 hours using UV radiation and intermittent water spray. Changes in color and dimensional stability properties of the oil heat-treated wood were examined after (1) heat treatment and (2) accelerated UV weathering. The results show that the oil heat-treated wood turned darker and was more dimensionally stable. After oil heat treatment, the color of both the surfaces was uniform. Although color was darker on the surface than at the core, this contrast decreased with increasing treatment temperature. After the accelerated weathering test, the oil heat-treated wood retained its dimensional stability and color better than the untreated wood. No surface checks were observed in weathered treated wood, and volumetric swelling was also less compared with the untreated wood. Similarly, no color fading was observed in wood treated at 160°C and 180°C, while slight fading was noted for specimens treated at 210°C.

This study aimed to optimize manufacturing conditions when utilizing eastern white cedar (Thuja occidentalis L.) to increase the durability of structural panels with aspen (Populus tremuloides Michx.) strands in terms of resistance to mold and decay. Panels of three layers using eastern white cedar strands in two face layers and aspen in a core layer were made under different species ratios, temperatures, and pressing conditions. The physical and mechanical properties as well as mold and decay resistances of the panels were tested according to standard methods. Panels with white cedar strands in surfaces and aspen strands in the core at a ratio of 25:50:25 and pressed at 240°C for 180 seconds had the best mechanical and physical properties. Aspen panels with white cedar strands in surfaces at a ratio of 15:70:15 had similar internal bond (IB) and thickness swelling values, lower water absorption (WA), and higher modulus of rupture (MOR) and modulus of elasticity (MOE) compared with pure-aspen control panels. When the white cedar strand proportion in the two surface layers was increased from 15 to 25 percent, IB strength and WA of panels decreased, whereas MOR and MOE increased. Panels with white cedar strands in surfaces at a ratio of 15:70:15 had little infection from molds on the two surface layers but a moderate infection rate on all four sides. In terms of mold and decay resistance, panels made with 25 percent white cedar strands in surfaces performed better than those with 15 percent.

Wood plastic composite (WPC) materials are being developed for load-bearing structural applications; therefore, the strain rate-dependent mechanical properties of WPC materials need to be characterized. Extruded WPC Z-section sheet piles composed of 46 percent wood flour, 41 percent polypropylene, and additives were investigated. ASTM D6109 was adopted for assessing flexural properties of plastic lumber in a four-point loading configuration. Coupons were cut from the flanges of the sheet pile section and conditioned for 2 weeks at 21°C and 65 percent relative humidity. The flexural tests were conducted at three different strain rates: 0.55, 1.0, and 5.5 percent per minute. The mode of failure was in tension in the middle third of the bending span. It was found that the mean apparent modulus of elasticity (MOE) increased with the strain rate; e.g., the MOE increased 9.5 percent when the strain rate was increased from 1.0 to 5.5 percent per minute. The variations in mean strain at failure with the strain rate were not statistically significant based on analysis of variance testing. The variation in flexural MOE with the strain rate was compared with the published tensile and compressive MOE values for the same material. The effect of strain rate on the flexural MOE of the polypropylene WPC material was also correlated with the published results for WPC materials with other polymer matrices (high-density polyethylene and polyvinyl chloride). The strain rate effects in the MOE of the WPC material was predicted based on a viscoelastic standard solid model calibrated with the coupon level data.

The objective of this study was to investigate the effects of heat treatment on the physical and mechanical properties of sessile oak (Quercus petraea). Samples were exposed to three temperature levels of 120°C, 150°C, and 180°C for time periods ranging from 2 to 10 hours. Modulus of elasticity, modulus of rupture, compression strength parallel-to-grain, hardness, impact bending, tension strength, swelling in three sections, and surface roughness of the samples were evaluated. Based on the findings in this study, the results showed a significant difference between properties of control samples and heat-treated samples (P = 0.05). Mechanical properties of the samples were adversely influenced as a result of heat treatment; however, surface quality and dimensional stability of the samples improved with heat treatment. Changes in properties of the samples were more pronounced as temperature and exposure times were increased.