The occurrence of hollows in eucalypts and Ironwood Erythrophleum chlorostachys in the Gulf region of the Northern Territory and its implications for timber harvesting

Abstract

The occurrence of hollows in eucalypts and Ironwood Erythrophleum chlorostachys was examined in different habitats in Limmen National Park in the Gulf Falls and Uplands bioregion of the Northern Territory. For each tree sampled, the diameter of the trunk at breast height (DBH) and numbers of hollows in three size categories were recorded. It was found that the riparian zone had the highest density of hollows per unit land area, followed by the rocky hill zone, and then the sandy flat zone. The relationship between hollows per tree and DSH was compared for four species: Eucalyptus camaldulensis (the dominant riparian tree), Eucalyptus leucophloia (the dominant tree on rocky hills), Eucalyptus miniata (the dominant tree on sandy flats), and Ironwood. E. miniata and Ironwood were found to have fewer hollows for a given DBH. It is suggested that the low incidence of hollows in Ironwood is a result of the species' know resistance to termites. The low number of hollows per Ironwood tree, the scarcity of Ironwood in the study area, and the small size of Ironwood trees relative to most of the eucalypts resulted in very few Ironwood hollows overall. This considered, harvesting of Ironwood (a preferred timber species) in this area is unlikely to have an impact on the availability of hollows to fauna. Further research is required to clarify discrepancies with other studies, and assess whether these results apply more broadly, for instance to wetter areas with larger Ironwood trees.