Relationship between incipient decay, strength, and chemical composition of Douglas-fir heartwood

A new laboratory technique to simulate the initiation of wood decay and to assess the effects of incipient decay on material properties is described. Douglas-fir heartwood specimens were exposed to brown-rot (Postia placenta and Gloeophyllum trabeum) fungi for various periods. Bendlng properties were determined by nondestructive and destructive tests, and chemical composition of specimens was analyzed. Weight losses of 1 to 18% were linearly related to strength losses of 5 to 70%. Wood strength loss by brown-rot fungi was also closely related to degradation of hemi-cellulosic components. Hemicellulose sidechains, such as arabinose and galactose, were degraded in the earliest stages of decay; main-chain hemicellulose carbohydrates, such as mannose and xylose, were degraded in the later stages. Changes in glucose content, a measure of residual cellulose, were minimal. Our technique was effective for establishing and assessing brown-rot decay