Understanding how silvicultural treatments and changes in the forest resource will affect wood quality characteristics, including heartwood natural durability, is a critical need for forest managers. Because heartwood properties can be affected by environmental disturbances, including silvicultural practices used to grow trees faster, we need to know if increased growth...
The air permeability of western hemlock from coastal forests in western Oregon was assessed. Permeability varied widely among trees, as well as by position within individual trees. Permeability tended to decrease with distance inward from the bark, a trend implying that this species produces a heartwood zone. These variations may...
The high decay resistance of western redcedar (Thuja plicata Donn) is due to the presence of toxic extractives, called tropolones, in the heartwood. Therefore, tropolone content may be used as an indicator of decay resistance. With increment core-sized samples of western redcedar heartwood, we used gas chromatography to measure tropolone...
While wood plastic composites have gained an increasingly large share of the market for decks and other outdoor structures, there are many questions about the long-term potential for biodeterioration of these materials. While the plastic does appear to retard moisture uptake, thereby slowing the rate of degradation, a number of...
High concentrations of the fumigant methylisothiocyanate (MITC) will effectively control decay fungi in large wood structures, but the fungitoxicity of low MITC concentrations and the influence of wood moisture content (MC) on its performance are not well understood. The MC of Douglas-fir heartwood greatly influenced the susceptibility of the decay...
Preservative treatment of whole, wood-based composite products (mainly panels) has disadvantages; problems largely stem from swelling, strength loss, and incomplete or inappropriate penetration during treatment, and distortion during redrying. Pretreatment of comminuted wood prior to mat lay-up is one alternative, though the addition of chemicals may affect bonding during subsequent...
Mylone@ and tridipam are two solid chemicals that decompose to produce methylisothiocyanate (MIT), a highly effective wood fumigant. In this study, two techniques -- a rapid, test-tube method and small-scale, wood-block assay -- were used to determine the effect of the pH of various chemical buffers on the decomposition of...
Adverse effects on mechanical properties from using a supercritical fluid (SCF) to increase preservative penetration of refractory woods were evaluated by treating small ponderosa pine sapwood specimens with supercritical carbon dioxide at 64 combinations of temperatures (35 to 80 C), pressure (1,000 to 4,000 psig), and time (0.5 to 2...
The effect of supercritical fluid treatment on superficial gas permeability of Douglas-fir was investigated by using carbon dioxide either alone or amended with methanol. Permeability increased in a majority of samples, although nearly one-third of the specimens declined in permeability. Improvements in permeability appeared to be unrelated to variations in...
The effects of moisture content, flow direction, concentration, and temperature on the diffusion of chloropicrin in Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) heartwood were investigated. Diffusion coefficients were strongly affected by wood moisture content. Coefficients for radial and tangential diffusion at the fiber-saturation point were twice as high as those at...
The resistance of three naturally durable heartwood species and a stranded giant bamboo product to fungal and termite (Coptotermes formosanus) attack was evaluated at a test site located near Hilo, Hawaii. Merbau (Intsia bijuga or I. palembanica) and ipe (Tabebuia spp.) were both exceptionally resistant to fungal and termite attack,...
A new laboratory technique to simulate the initiation of wood decay and to assess the effects of incipient decay on material properties is described. Douglas-fir heartwood specimens were exposed to brown-rot (Postia placenta and Gloeophyllum trabeum) fungi for various periods. Bendlng properties were determined by nondestructive and destructive tests, and...
The effect of pretreatment of Douglas-fir flakes with CCA-C, borate, and azaconazole on properties of flakeboard was studied. Flakes had higher retention levels of CCA-C and borate in their ends than in their centers. The distribution of chemicals was uniform in panels, which indicates that the chemicals did not migrate...
Studies of the effects of various chemicals on fungal growth are difficult to perform on filamentous fungi because of the difficulty of observing the protoplasm through the rigid hyphal wall, and because most activity occurs in the region near the hyphal tip. However, hyphae can be exposed to certain enzymes...
The ability to treat Scots pine (Pinus sylvestris) and Norway spruce (Picea abies) with oilborne copper-8-quinolinolate or with waterborne chromated copper arsenate, ammoniacal copper zinc arsenate, or ammoniacal copper quaternary was assessed using commercial treatment facilities in the Pacific Northwest. In general, Scots pine was more easily treated than was...
An aging electricity distribution system and reduced availability of naturally durable tropical hardwoods in Australia will
combine in the next decade to produce a major shortage of poles. One approach to mitigating this shortage is to utilize lower
durability species and improve the penetration of preservatives into the refractory heartwood...
The potential for using pretreatment with cinnamon leaf oil or juniper foliage oil to improve the durability of viscoelastic thermal compression (VTC)–treated hybrid poplar was explored in a field termite test and a laboratory mold test. The addition of oils prior to VTC processing had variable effects on resistance to...
The ability of white and brown rot fungi to colonize wood-plastic composites was investigated by measuring weight loss and anatomical changes. Three composite materials were evaluated. The material containing a 70/30 wood-high density polyethylene (HDPE) mixture was most susceptible to fungal attack, while two different 50/50 wood-HDPE composites experienced little...
The amounts of treated wood present at a wood recycling center in western Oregon were surveyed over a 10-year period. Treated wood was found at 106 of 112 inspections, but the levels never exceeded 2 percent of the volume present. The amount of treated wood averaged 0.15 percent of the...
The chemical composition of the boles of 14 Douglas-fir trees growing in the central Willamette Valley of western Oregon was examined to determine whether differences in various chemical component levels might help to explain arthropod or microbial colonization patterns. Levels of nearly all cations as well as N and P...