WOOD CHEMICAL COMPONENTS AND DECAY RESISTANCE OF FOUR COMMON MONGOLIAN SOFTWOODS

To utilize wood resources in Mongolia, amounts of wood chemical components (hot-water extracts, 1% NaOH extracts, ethanol-toluene extracts, holocellulose, -, -, and -cellulose, Klason lignin, and ash) were determined in four common Mongolian softwoods, Pinus sylvestris, Pinus sibirica, Picea obovata, and Larix sibirica. In addition, decay resistance of heartwood was evaluated against a white-rot fungusTrametes versicolor, and a brown-rot fungusFormitopsis palustris. Among the four species, heartwood of Larix sibiricawas chemically characterized by higher amounts of hot-water and 1% NaOH extracts, and lower amounts of holocellulose and Klason lignin. These characteristics may be related to thepresence of arabinogalactan which is easily extracted with cold water. Mean mass loss in each softwood ranged from 6.9% to 28.1% in white-rot fungus, and from 24.8% to 48.3% in brown-rot fungus. Among four species, Pinus sibiricashowed the highest decay resistance against both fungi. By the linear mixed-effects model analysis, negative relationships were found between mass loss and amounts of extracts in heartwood, suggesting that heartwood having larger amounts of extracts showed higher natural decay durability.