The taxonomy and ecology of wood decay fungi in Eucalyptus obliqua trees and logs in the wet sclerophyll forests of southern Tasmania

The wet sclerophyll forests in southern Tasmania are dominated by Eucalyptus obliqua and are managed on a notional silvicultural rotation length of 80 to 100 years. Over time, this will lead to a simplified stand structure with a truncated forest age and thus reduce the proportion of coarse woody debris (CWD), such as old living trees and large diameter logs, within the production forest landscape. Course woody debris is regarded as a critical habitat for biodiversity management in forest ecosystems. Fungi, as one of the most important wood decay agents, are key to understanding and managing biodiversity associated with decaying wood. In Australia, wood-inhabiting fungi are poorly known and the biodiversity associated with CWD has not been well studied. This thesis describes two studies that were undertaken to examine the importance of CWD as habitat for wood-inhabiting fungi in the wet sclerophyll forests of Tasmania. Study one examined the effect of changing tree age on the fungal species richness, fungal community composition and rotten wood associations within the tree. Six living E. obliqua trees in each of three age-classes (69, 105 and >150 years old) were felled. Each tree was cross-cut at nine standard sampling points and the decay profile was mapped. Fungi were isolated from rotten wood at each sampling point, and from control samples of clear heartwood and sapwood. Samples of each rotten wood type were collected and classified, based on their colour and texture. Wood-inhabiting fungi in Australia are not well known, making the identification of fungal cultures problematic. In study one, cultures of wood-inhabiting fungi were grouped into putative species groups and identified using both morphological techniques and polymerase chain reaction (PCR) and sequencing of the internal transcribed spacer (ITS) region of the ribosomal DNA. Ninety-one species of wood-inhabiting fungi were isolated from the 18 trees examined in study one. Eight different rotten wood types were identified and studied. The community composition of wood-inhabiting fungi in trees greater than 150 years old (the oldest age-class examined) was very different compared with those found in the younger two age-classes; more than half of all species were only found in these older trees. In addition, trees in the oldest age-class contained greater volumes and proportions of rotten wood habitat. The second study examined the wood-inhabiting fungi that had been isolated in a previous study by Z-Q Yuan (University of Tasmania) from large (>85 cm) and small (30-60 cm) diameter E. obliqua logs in mature, unlogged forests and 20-30 year-old logged forests that were regenerating after clearfelling. The previously described morphospecies were tested using PCR-sequencing of the ITS region of ribosomal DNA and a consensus final species groupings was obtained. This study determined that a total of 60 species of wood-decay fungi had been commonly isolated from the 36 logs examined. Significant differences in fungal community structure were found between mature forests and regenerating forests. Some differences in fungal species richness and community composition were also found between logs of different sizes. These studies are among the first to examine wood-inhabiting fungi in mature E. obliqua trees and logs in Tasmania. The ecological information obtained from this research will assist in the development and deployment of strategies for the management of mature living trees and logs in wet eucalypt forests in Tasmania. This research suggests there is a need for forest managers to consider instigating measures that allow for some trees in the production forest landscape to live long enough to develop decayed wood habitat. This will provide important habitat for fungi as both trees and large diameter logs, sustaining an important component of forest biodiversity.