THE ABUNDANCE AND DEVELOPMENT OF CAVITIES IN EUCALYPTUS TREES - A CASE-STUDY IN THE MONTANE FORESTS OF VICTORIA, SOUTHEASTERN AUSTRALIA

A study of the abundance of cavities in Eucalyptus regnans, Eucalyptus delegatensis, Eucalyptus nitens, Eucalyptus obliqua and Eucalyptus cy pellocarpa is described. The investigation used a database of 2315 liv ing and dead trees with cavities, measured on 523 sites each of 3 ha t hroughout the montane ash forests of the Central Highlands of Victoria , southeastern Australia. Poisson regression analysis was used to exam ine the relationships between the number and type of cavities and a ra nge of attributes of trees. These analyses demonstrated that, for all species of trees, the abundance of holes, fissures and hollow branches increased with tree diameter. Log-linear analysis of contingency tabl es demonstrated that various combinations of cavity types typically oc cur. Patterns of co-occurrence of cavities changed significantly accor ding to the diameter, height and form of trees. The application of res tricted maximum likelihood estimation (REML) for examining multi-level data, enabled the relationships between the number of cavities, tree characteristics and site parameters to be analysed concurrently. The c haracteristics of trees that were important were height, diameter and form. Site parameters that had a significant influence on the total nu mber of cavities in trees included slope, latitude and stand age. This highlights the range of factors, at several measured spatial scales, that may influence the development of cavities in Eucalyptus trees. Al though the various relationships derived in this study were highly sig nificant, the statistical models had limited predictive ability. Thus, for any given tree the development of cavities will be influenced by site and tree attributes as well as highly stochastic episodic events that may occur during its lifetime. The key findings from the study ar e discussed in terms of their relevance to forest wildlife management.