Treesearch

Following damage caused by Hurricane Hugo (September 1989) we monitored inorga­nic nitrogen availability in soil twice in 1990, leaf area index in 1991 and 1993, and litter production from 1990 through 1992 in subtropical wet forest of eastem Puerto Rico. Experimental removal of litter and woody debris generated by the hurricane (plus any standing stocks present before the hurricane) increased soil nitrogen availability and above-ground productivity by as much as 40% compared to unmanipulated contro! plots. These increases were similar to those created by quarterly fertilization with...

Laccase is one of the ligninolytic enzymes found in liquid cultures of the fungus Ceriporiopsis subvermispora in defined medium. As an approach to a clarification of the role of laccases during the attack on lignin by the fungus, the enzyme has been characterized further. The levels of this phenol oxidase increase 2-fold in the presence of p-anisidine and are severely affected when addition of either Mn(II) or Cu(II) ions to the medium is omitted. Isoelectrofocusing allowed the resolution of two laccase isoenzymes, with pIS of 3.65 and 3.59. In rich medium, laccase activity is 10-fold...

Moisture accumulation and extreme fluctuations in moisture levels can adversely affect the service life of components, such as wood siding and windows. Adverse moisture conditions can induce checking, warping, paint failure, and in severe cases, rotting of the wood.

Geotextiles are any textile like material used to enhance soil structural performance. Biobased geotextiles are used for short term (6 months to 10 year) applications where biodegradability is a positive attribute, such as mulching and erosion control. Fiber options for biobased geotextiles include cereal straws, coir, jute, kenaf, flax, sisal, hemp, cotton, woodfiber and others. This report documents research the USDA Forest Service is conducting using biobased geotextiles to increase tree seedling survival rates, establish vegetation, and control erosion.

Six room/comer tests of common wall linings were conducted with gypsum-lined ceiling exposed to propane burning at 100 kW for 10 min followed by 300 kW for 10 min. This test protocol is an option provided by ISO 9705. The flashover event occurred at 1,000 kW rate of heat release within several seconds of observing flames out the doorway. The time to flashover of the fire-retardant-treated polyurethane foam was 10.5 rein, which contrasts with no flashover for some melting materials exposed to propane burning at 40 and 160 kW. The time to flashover for all the wood materials tested ranged...

Quantities of paper and wood recovered annually for recycling were estimated for all principal commercial uses in the United States, based on material consumption and end-use data. Principal categories of commercial uses were identified and relative quantities were compared. Some innovative or novel commercial product developments were identified. The potential for additional recovery from municipal solid waste, construction and demolition debris, primary timber processing residues, and other sources was also identified.

Stress-laminated timber bridges were first introduced in the United States in the late 1980s. Since that time, the concept of stress-laminating has received a great deal of attention and hundreds of bridges have been built. Most of these bridges are located on rural low-volume roads. To evaluate the performance of stress-laminated bridges, the United States Department of Agriculture (USDA) Forest Service, Forest Products Laboratory, implemented a nationwide bridge monitoring program in 1988 that was subsequently expanded in 1992 to include a cooperative program with the Federal Highway...

Researchers at the Forest Products Laboratory, USDA Forest Service, have been studying nondestructive techniques for evaluating the strength of wood. This report describes the results of a pilot study on using these techniques to determine the quality of large dimensional lumber cut from switch ties. First, pulse echo and dynamic (transverse vibration) techniques were used to determine the modulus of elasticity (MOE) of 12 untreated red oak switch ties. The ties were then sawn into nominal 2 by 8 specimens, which were later resawn into nominal 2 by 4 specimens. Pulse echo and transverse...

Recent studies on the effects of chromated copper arsenate (CCA) treatment on lumber design properties have primarily evaluated the effects of such treatment at or near 12% moisture content and at failure times of 1 to 10 min. The influence of various moisture contents and faster loading rates is unknown. This report discusses the influence of moisture content and its interaction with time-to failure on the bending strength of CCA- treated (0.4 lb/ft 3 (6.4 kg/m 3 )) lumber. The factors studied were moisture contents of 10, 15, and ³23% (green lumber) and ramp-load failure times in bending...