Selected mechanical and physical properties of Chilean tepa wood affected by butterfly stain

Tepa (Laureliopsis philippiana Looser) is a valuable Chilean temperate hardwood timber species. In anticipation of projected timber shortages in the United States, a request has been made to the Animal and Plant Health Inspection Service (APHIS) to permit importation of tepa logs. The only known major pathogen-related defect is a discoloration of the heartwood known as butterfly stain. This stain, which extends through the length of the bole, appears in cross section as a series of partially overlapping orange-brown arcs, each limited by a black zone line. The cause of the stain may be a compartmentalization-type of response to injury or small branch death and subsequent invasion by bacteria and/or bacterial invasion through the root system. This investigation examined stained wood versus nonstained wood for possible differences in mechanical strength, mineral content, pH, moisture content (MC), and density. Compression (n = 148) and static bending (n = 139) tests demonstrated that samples from stain-affected trees were significantly weaker than samples from nonaffected trees, regardless of whether the sample contained stained wood. There were no differences in shear strength (n = 119). Mineral content and pH suggest no pattern, but post-conditioning MC of stained and nonstained static bending samples from trees affected by stain was significantly greater than samples from trees unaffected by the stain. Density of compression samples from stained wood was significantly greater than that of nonstained samples from stain-affected trees. Data from this research together with a separate bacterial study support the hypothesis that tepa wood with butterfly stain has been bacterially degraded and that this produces a weakened wood matrix.

You must be logged in to download any documents. Please login (login accounts are free) or learn how to Become a Member