RELATIONSHIP BETWEEN INCIPIENT DECAY, STRENGTH, AND CHEMICAL COMPOSITION OF DOUGLAS-FIR HEARTWOOD

Abstract

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 (Po'orrra p l ~r r n r a and Glo~oph.~Uumrruhcum) iungi for various penods.Bendlng properties were determined by nondestructive and destructive tests, and chem~cal composilion of spec~men~ was analyzed.Welght losses of I lo 18% were Innearl?related to strength losses of5 tu 70%.Wood strength loss bv hrou11-rot fungi was also closel!relaled to desradatron of hem~ccllulosr.comDonents.Hemscellulose sidechains, such as arahinose 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.