Comparison of the occurrence of rot in sawlogs from regrowth and mature stands of Eucalyptus diversicolor (karri)

Abstract

SummaryKarri (Eucalyptus diversicolor) timber from old-growth forest has been highly valued for heavy engineering construction, special purpose rail track timbers, scantling for housing, mine guides, joinery, furniture and flooring. With changes to forest management, sawlogs from mature stands have been supplemented by sawlogs from regrowth stands. A survey was conducted to compare the quality of sawlogs from mature and regrowth stands in relation to incipient rot, established rot, other defects and market expectations for this species. Sawmill surveys of sawlogs from regrowth and mature stands were carried out in 1987 and 1992 respectively. These surveys showed that there was significantly more incipient rot, known locally as brown wood, and or wood rot in regrowth sawlogs than in sawlogs from mature stands, while there was significantly less kino in regrowth sawlogs. The most common defects in both log classes were the presence of kino and incipient rot. The most frequent infection points for wood rot fungi were branch stubs, borer galleries and scars (which may have been caused by Armillaria infection, fire damage or mechanical damage). Infection associated with branching was more common in regrowth sawlogs than in sawlogs from mature stands. In both log classes, scattered pockets of incipient rot and or established rot were most frequently associated with borer galleries. In regrowth sawlogs, when at least two-thirds of the whole cross-section of the log was affected by incipient rot and or established rot, it was associated with scars resulting from fire, Armillaria or mechanical damage. Since this survey was conducted, changes in Western Australian government policy have resulted in only regrowth forest being available for harvest.