Cavity sizes and types in Australian eucalypts from wet and dry forest types - a simple of rule of thumb for estimating size and number of cavities

We describe the relationships between the number, size and type of cavities in six species of eucalypt trees from southern New South Wales (south-east ern Australia) and tree diameter, tree height, tree species and other measu res. The eucalypt species studied were:-Narrow-leave Peppermint (Eucalyptus radiata), Mountain Swamp Gum (Eucalyptus camphora), Mountain Gum (Eucalypt us dalrympleana), Red Stringybark (Eucalyptus macrorhyncha), Ribbon Gum (Eu calyptus viminalis), and, Broad-leaved Peppermint (Eucalyptus dives). E. radiata and E. macrorhyncha supported almost twice the proportion of bra nch-end hollows than cavities assigned to other categories. Cavities in the main trunk were the predominant hollow class in E. viminalis and E. dalrym pleana. Large diameter trees were characterised by more branch-end hollows, whereas main trunk cavities were typically the most prevalent cavity type in smaller diameter stems. We identified a simple, general rule that highlights the relationships betw een cavities and readily measured tree attributes. Our data show that, in g eneral, both the number of cavities and cavity size were directly proportio nal to tree diameter, but inversely proportional to the square root of tree height. This proportionality changed between different tree species. E. di ves and E. viminalis supported, on average, larger cavities than other spec ies, whereas the cavities in E. macrorhyncha were smaller than the other ta rs sampled. This simple general relationship may make it possible to make r apid crude estimates of cavity abundance across large areas of forest by me asuring simple tree attributes such as tree diameter and tree height. (C) 2 000 Elsevier Science B.V. All rights reserved.