Abstract: Natural decay resistance of the heartwood of Cunninghamia lanceolata, Phoebe sheareri, Sassafras tzumu, Quercus fabri, and Catalpa bungei was determined by the soil-block method with Coriolus versicolor (white rotter) and Gloeophyllum trabeurn (brown rotter) in the laboratory. The changes in amounts of major components during decay of samples were analysed. The results showed that decay resistance of the heartwoods was very resistant or resistant to both C. versicolor and G. trabeum, but Populus deltoides as control sample was very susceptive to these two fungi. This reflects that these heartwood contain active antifungal substance. C. versicolor decomposes holocellulose and lignin at approximately the same relative rates, and the solubility of wood in 1% NaOH solution drops progressively. G. trabeum mainly degradates the polysaccharides in wood and causes only a small loss in lignin, and the solubility of wood in 1% NaOH solution increases substantially on attack by G. trabeum in early stages of brown rot. In later stages, the partially degraded carbohydrate fragments are utilized by the brown rot, so the solubility of wood in 1% NaOH solution quickly declined drop by drop.

Key words: Natural decay resistance, Coriolus versicolor, Gloeophyilum trabeum