Treesearch

Conifer resin and phloem tissue contain several phytochemical groups, composed primarily of monoterpenes, diterpene acids, and stilbene phenolics. The effects of monoterpenes and phenolics on stem-colonizing bark beetles and their associated microorganisms have been studied to some extent, but the roles of diterpene acids are largely unknown. Diterpene acids are known to have substantial feeding deterrent and growth inhibiting effects on a variety of insect groups and are known to inhibit a variety of fungi. We tested three diterpene acids present in red pine, Pinus resinosa, at various...

An appreciation of rheology, material science, organic chemistry, polymer science, and mechanics leads to better understanding of the factors controlling the performance of the bonded assemblies. Given the complexity of wood as a substrate, it is hard to understand why some wood adhesives work better than other wood adhesives, especially when under the more severe durability tests. In general, wood is easy to bond to compared to most substrates, but it is harder to make a truly durable wood bond. A main trend in the wood industry is increased bonding of wood products as a result of the use...

The traditional question at the start of a class on thermal properties of wood is, “Does wood burn?” The students have all been warmed in front of a wood-burning fire before, so they are sure the answer is yes—but since the professor asked the question, there must be some hidden trick to the obvious answer. Going with their experience, their answer is “yes, wood burns.” But, the actual answer is no, wood does not burn. In short, wood undergoes thermal degradation as it heats up, giving rise to volatile, flammable gases which burn when they contact a source of ignition. So it is the...

Wood was designed by nature over millions of years to perform in a wet environment. The wood structure is formed in a water-saturated environment in the living tree, and the water in the living tree keeps the wood elastic and able to withstand environmental strain such as high wind loads. We cut down a tree, dry the wood, and mainly use it in its dry state. But wood in use remains a hygroscopic resource. Wood’s dimensions and mechanical, elastic, and thermal properties depend on the moisture content. Wood is also anisotropic, which means that its properties vary according to its growing...

Brown rot basidiomycetes have long been thought to lack the processive cellulases that release soluble sugars from crystalline cellulose. On the other hand, these fungi remove all of the cellulose, both crystalline and amorphous, from wood when they degrade it. To resolve this discrepancy, we grew Gloeophyllum trabeum on microcrystalline cellulose (Avicel) and purified the major glycosylhydrolases it produced. The most abundant extracellular enzymes in these cultures were a 42-kDa endoglucanase(Cel5A), a 39-kDa xylanase (Xyn10A), and a 28-kDa endoglucanase (Cel12A). Cel5A had significant...

There are numerous biological degradations that wood is exposed to in various environments. Biological damage occurs when a log, sawn product, or final product is not stored, handled, or designed properly. Biological organisms, such as bacteria, mold, stain, decay fungi, insects, and marine borers, depend heavily on temperature and moisture conditions to grow. A higher number means a greater decay hazard. The southeastern and northwest coasts have the greatest potential and the southwest has the lowest potential for decay. This chapter will focus on the biological organisms and their...

Inspection of the genome of the ligninolytic basidiomycete Phanerochaete chrysosporium revealed an unusual peroxidase-like sequence. The corresponding full length cDNA was sequenced and an archetypal secretion signal predicted. The deduced mature protein (NoP, novel peroxidase) contains 295 aa residues and is therefore considerably shorter than other Class II (fungal) peroxidases, such as lignin peroxidases and manganese peroxidases. Comparative modeling of NoP was conducted using the crystal structures of Coprinus cinereus and Arthromyces ramosus peroxidases as templates. The model was...

The Rancho La Brea tar pit fossil collection includes Juniperus (C3) wood specimens that 14C date between 7.7 and 55 thousand years (kyr) B.P., providing a constrained record of plant response for southern California during the last glacial period. Atmospheric CO2 concentration ([CO2]) ranged between 180 and 220 ppm during glacial periods, rose to 280 ppm before the industrial period, and is currently approaching 380 ppm in the modern atmosphere. Here we report on [delta]13C of Juniperus wood cellulose, and show that glacial and modern trees were operating at similar leaf- intercellular...

In chemical terms, wood is best defined as a three-dimensional biopolymer composite composed of an interconnected network of cellulose, hemicelluloses, and lignin with minor amounts of extractives and inorganics. The major chemical component of a living tree is water, but on a dryweight basis, all wood cell walls consist mainly of sugar-based polymers (carbohydrates, 65–75%) that are combined with lignin (18–35%). Overall, dry wood has an elemental composition of about 50% carbon, 6% hydrogen, 44% oxygen, and trace amounts of inorganics. Simple chemical analysis can distinguish between...

The research presented in this report was conducted to evaluate the accuracy and reliability of a commercially available micro-drilling resistance device, the IML RESI F300-S (Instrument Mechanic Labor, Inc., Kennesaw, Georgia), in locating deteriorated areas in timber bridge members. The device records drilling resistance as a function of drilling depth, which allows the operator to assess the location of deterioration in the member cross section. Bridge components containing different levels of natural decay were used as test specimens in this study. The IML RESI F300-S was first used to...