Hollow formation in eucalypts from temperate forests in southeastern Australia

We examined factors associated with the occurence of tree hollows in four eucalypt species from temperate forest in southeastern New South Wales and East Gippsland. A total of 1 256 standing trees and 328 felled trees was examined. The proportion of trees containing hollows with small entrances (2-5 cm) was significantly negatively associated with dbh, while the proportion of trees containing hollows with medium (5-10 cm) and large (>10 cm) entrances was positively associated with dbh. There was a significant, but weak, relationship between hollow depth and minimum entrance width that was improved with the addition to the model of the variables branch diameter and branch health. Trees of all sizes and ages contained hollows, although larger and older trees had a higher probability of doing so. For two tree species (Brown Barrel or Cuttall Eucalyptus fastigata and Messmate E. obliqua), the probability of live trees containing hollows remained below 0.5 for stems less than 180 years of age. Unlogged forest supported, on average, 22.0 hollow-bearing trees per ha - 18.5% of which were dead trees. For all values of dbh, trees were more likely to contain hollows if either dead or In poor physiological condition, indicating the potential for hollow development to be accelarted in eucalypts by killing or injuring suitably-sized trees