Pattern and process of heartrot inEucalyptus microcorys

Summary Interactions between organisms and between organisms and the host during heartrot in Eucalyptus microcorys were investigated. As decay progressed, basic density, moisture content and the pH of tissues decreased significantly, levels of magnesium rose minimally but significantly while those of sodium, potassium, calcium, manganese and ash altered little. These findings suggest a very different heartrot process in tallowwood as compared to that recorded in many deciduous hardwoods. Since alterations of wood properties during heartrot were in general minimal, and since such changes occurred only in regions of decay and not in those of discolouration, it is likely that the heartwood of this eucalypt is quite unresponsive to microbial invasion. The lack of intense discolouration about areas of rot supports this hypothesis. This unresponsiveness is probably manifested in passive compartmentalisation of microbial invasions. While fungal successions may occur in the heartrot process, these do not include bacteria.