Treesearch

The hymenochaetoid clade is dominated by wood-decaying species previously classified in the artificial families Corticiaceae, Polyporaceae and Stereaceae. The majority of these species cause a white rot. The polypore Bridgeoporus and several corticioid species with inconspicuous basidiomata live in association with brown-rotted wood, but their nutritional strategy is not known. Mycorrhizal habit is reported for Coltricia perennis but needs confirmation. A surprising element in the hymenochaetoid clade is a group of small white to brightly pigmented agarics earlier classified in Omphalina....

North American log markets function on different principles -- a profit allowance for the wood processor plays a role in timber pricing in Canada, while in the United States, it is a byproduct of the give and take of arm’s-length market negotiations. The former is characterized by high elasticities of price transmission and, at times of market weakness, by low elasticities of product supply; the other, by the opposite of these benchmarks. This can result in asymmetric supply responses in weak markets to the detriment of U.S. producers. Whether this is a subsidy in the sense of conferring a...

The United States has a century of experience with the development of models that describe markets for forest products and trends in resource conditions. In the last four decades, increasing rigor in policy debates has stimulated the development of models to support policy analysis. Increasingly, research has evolved (often relying on computer-based models) to increase understanding of consumer demands, producer behavior, landowner behavior, and conditions of the timber resource. Greater computational power available since the mid 1970s has allowed the evolution of bioeconomic models that...

Efficient and economical utilization of various bio-based materials is an effective way to improve forest management, promote long-term sustainability, and restore native ecosystems. However, the dilemma is how to deal with lesser used, undervalued or no-value bio-resources such as small diameter trees, agricultural residues (wheat straw, rice straw, and corn stalk), exotic-invasive species, recycled biofibers, and hazardous fuels and residues from fire-prone forests. This paper will present results from a number of research projects that have been conducted at USDA Forest Service, Forest...

When untreated wood is exposed to adverse outdoor conditions, nature has a series of chemistries to degrade it to its original building blocks of carbon dioxide and water. Fungi, termites, heat, moisture, ultraviolet (UV) energy, and chemicals take their toll on the performance properties of wood. We tend to study each of these degradation chemistries as individual events but, in fact, they are all connected by five basic chemistries: hydrolysis, oxidation, dehydration, reduction, and free radical cleavage. If we look more broadly at the commonalities involved in these chemistries, we can...

Although moisture sorption in woodfiber-thermoplastic composites (WPCs) is slower than in unmodified solid wood, it still affects strength and ultimately results in decay of the material in moist outdoor exposure conditions. Chemical modification of the hydroxyl groups of wood with acetic anhydride esterifies the hydroxyl making the wood more hydrophobic and dimensionally stable. Coupling agents are known to promote bonding between the plastic and unmodified wood fibers when added to WPCs. The objective of this study was to investigate several methods of decreasing moisture sorption and,...

Near infrared (NIR) spectroscopy has been previously used in our laboratory to predict copper, chromium, and arsenic levels in samples of chromated copper arsenate (CCA)-treated wood. In the present study, we utilized our custom-made NIR scanning system, NIRVANA (near infrared visual and automated numerical analysis), to scan cross sections of ACQ (alkaline copper quat)- treated timbers to assess whether this technology can be used as a quality control tool for wood treaters. Models for CuO retention were created using ACQ-treated and untreated southern yellow pine (SYP) wood blocks....

When wood fiber is exposed to significant heat, its strength decreases. It has long been known that prolonged heating at temperatures over 66°C (150°F) can cause a permanent loss in strength. The National Design Specification (NDS) provides factors (Ct) for adjusting allowable properties when structural wood members are exposed to temperatures between 38°C (100°F) and 66°C (150°F) for extended periods of time. The NDS Commentary further states that the use of structural wood members in applications involving prolonged exposure to over 66°C (150°F) should be avoided. Where such exposures do...

Wood-based composites represent a continuously increasing share of the wood products market. Commercial construction will be important for future expansion of the structural panels market. Use of engineered wood products as an alternative to traditional solid wood lumber is also increasing. A recent series of cone calorimeter tests evaluated the performance of several composite rim board materials, including three oriented strandboard (OSB) products, a com-ply product, a laminated veneer lumber product, plywood, and lumber. Although initial behavior was similar, the 300-s average heat...

A two-dimensional finite element model was used to study the effects of structural features on transient heat transfer in softwood lumber with various orientations. Transient core temperature was modeled for lumber samples “cut” from various locations within a simulated log. The effects of ring orientation, earlywood to latewood (E/L) ratio, and ring density were related to transient heat transfer. Quartersawn lumber was predicted to have a higher heat transfer rate than that of plainsawn lumber, and lumber containing pith may have a lower hear transfer rate than peripheral lumber. The...