Treesearch

The effects of historical land use on tropical forest must be examined to understand present forest characteristics and to plan conservation strategies. We compared the effects of past land use, topography, soil type, and other environmental variables on tree species composition in a subtropical wet forest in the Luquillo Mountains, Puerto Rico. The study involved stems > 10 cm diameter measured at 130 cm above the ground, within the 16-ha Luquillo Forest Dynamics Plot (LFDP), and represents the forest at the time Hurricane Hugo struck in 1989. Topography in the plot is rugged, and soils...

Intensive forest management, with a heavy emphasis on ecosystem management and restoring or maintaining forest health, will result in the removal of smaller diameter materials from the forest. This increases the probability of higher juvenile wood content in the harvested materials. The purpose of this study was to compare the performance of loblolly pine juvenile and mature wood unbleached thermomechanical pulp (TMP). The TMPs were prepared without screening (unscreened TMP) and after screening (screened TMP). Pulp and paper properties were tested. Paper made from screened juvenile and...

This paper describes the development of a microsssay for boron and the application of this microassay for evaluating leachability of boron by post-treatment of southern pine with the calcium precipitating agent NHA (N'N-napthaloylhydroxylamine). The microsssay method for quantitative estimation of boron content in treated wood and leachates is a microadaptation of the colorimetric azomethine-H method. The primary advantages of this microassay method are that it uses fewer reagents, uses smaller sample volumes, and conserves time for analysis when a large number of tests are required. Wood...

The term wood-plastic composites refers to any composites that contain wood (of any form) and thermosets or thermoplastics. Thermosets are plastics that, once cured, cannot be melted by reheating. These include resins such as epoxies and phenolics, plastics with which the forest products industry is most familiar. Thermoplastics are plastics that can be repeatedly melted, such as polyethylene and polyvinyl chloride (PVC). Thermoplastics are used to make many diverse commercial products such as milk jugs, grocery bags, and siding for homes. Wood-thermoset composites date to the early 1900s....

Smooth-planed western redcedar bevel siding was exposed outdoors (preweathered) for 1, 2, 4, 8, and 16 weeks. The weathered boards were separated into two end-matched groups. One group was painted with only primer paint and tested for paint adhesion following preweathering. The second group was painted with a primer and topcoat, exposed outdoors for an additional 17 years, and evaluated during this period for paint cracking and flaking. There was a direct correlation between the amount of time the siding was preweathered and the long-term paint performance. Those boards preweathered for 16...

In previous research, it was shown that decreasing either press temperature or press time generally resulted in decreased volatile organic compound (VOC) emissions during the hot-pressing of southern pine particleboard. However, because it is impossible to reduce both pressing time and temperature while maintaining panel physical and mechanical properties, this study evaluated two sets of conditions to determine whether it might be more advantageous, from an emissions perspective, to hot-press at a lower temperature for a longer pressing time or at a higher temperature for a shorter...

This paper presents a stress analysis of the off-axis tension test of clear wood specimens based on orthotropic elasticity theory. The effects of Poisson's ratio and shear coupling coefficient on stress distribution are analyzed in detail. The analysis also provides a theoretical foundation for the selection of a 10° grain angle in wood specimens for the characterization of shear properties. The Tsai-Hill failure theory is then applied to derive a formula for predicting shear strength. Existing strength data for Sitka spruce (Picea sitchensis Carr.) were used in a numerical analysis....

Research programs throughout North America are increasingly focusing on understanding and defining the salient issues of wood durability and maintaining and extending the serviceability of existing wood structures. This report presents the findings and implications of a 10-year research program, carried out at the USDA Forest Service, Forest Products Laboratory, to develop kinetics-based service-life models for untreated and fire-retardant- (FR) treated plywood roof sheathing exposed to elevated in-service temperatures. This program was initiated because some FR-treated sheathing products...

To help meet the need for sustainable forest management tools, the USDA Forest Products Laboratory is developing an economically viable process to produce three-dimensional structural fibreboard products that can utilize a wide range of lignocellulosic fibres contained in the forest undergrowth and in underutilized timber. This will encourage the public and private sector to undertake thinning or clearing of these components from the forest thereby reducing or removing dangerous fuels and minimizing costs to the federal government for fire mitigation. The proposed product consists of a...

What materials will emerge from today’s research ideas to become the commonly accepted building products of 2020? What will durable materials look like in 2020? This paper attempts to address these questions by considering some current trends and then presenting a series of ideas of what the next 2 decades may hold from an emerging materials standpoint for North American light-frame construction. Still, no one can predict the future. This paper reviews a series of recent trends in materials usage, construction engineering, and laboratory research. It also attempts to explicitly state its...