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Keywords:

  • eucalypt forest;
  • fire ecology;
  • flammability;
  • giant trees;
  • old-growth forest;
  • plant height;
  • rain-forest;
  • succession

Contents

 Summary1001
I.Introduction1001
II.Giant eucalypts in a global context1002
III.Giant eucalypts – taxonomy and distribution1004
IV.Growth of giant eucalypts1006
V.Fire and regeneration of giant eucalypts1008
VI.Are giant eucalypts different from other rain-forest trees?1009
VII.Conclusions1010
 Acknowledgements1011
 References1011

Summary

Tree species exceeding 70 m in height are rare globally. Giant gymnosperms are concentrated near the Pacific coast of the USA, while the tallest angiosperms are eucalypts (Eucalyptus spp.) in southern and eastern Australia. Giant eucalypts co-occur with rain-forest trees in eastern Australia, creating unique vegetation communities comprising fire-dependent trees above fire-intolerant rain-forest. However, giant eucalypts can also tower over shrubby understoreys (e.g. in Western Australia). The local abundance of giant eucalypts is controlled by interactions between fire activity and landscape setting. Giant eucalypts have features that increase flammability (e.g. oil-rich foliage and open crowns) relative to other rain-forest trees but it is debatable if these features are adaptations. Probable drivers of eucalypt gigantism are intense intra-specific competition following severe fires, and inter-specific competition among adult trees. However, we suggest that this was made possible by a general capacity of eucalypts for ‘hyper-emergence’. We argue that, because giant eucalypts occur in rain-forest climates and share traits with rain-forest pioneers, they should be regarded as long-lived rain-forest pioneers, albeit with a particular dependence on fire for regeneration. These unique ecosystems are of high conservation value, following substantial clearing and logging over 150 yr.