Allocasuarina (Casuarinaceae) invasion of an unburnt coastal woodland at Ocean Grove, Victoria: Structural changes 1971-1996

Changes in vegetation structure in a long-unburnt (> 115 years) woodland at Ocean Grove, Victoria, were assessed by comparing density data collected i n 1971 by Withers and Ashton (1977) with comparable data from 1996. The cha nges in structure outlined by Withers and Ashton (1977) continued to operat e over the 25 year period, namely, a dramatic increase in the density of Al locasuarina littoralis (Salisb.) L.A.S.Johnson, and a continued decline in the once-dominant eucalypts, especially Eucalyptus ovata Labill. The densit y of A. littoralis increased from 911 trees ha(-1) in 1971 to 3565 trees ha (-1) in 1996. Most of the surviving E. ovata displayed extensive crown dieb ack, and appear likely to die in the near future. Many eucalypt seedlings w hich were planted into burnt and unburnt experimental plots in 1971 were st ill alive in 1996, but most were less than 0.5 m tall and suppressed by tal l regrowth of A. littoralis and Acacia pycnantha Benth. In the continued ab sence of fire and other disturbances, it is predicted that A. littoralis wi ll continue to dominate the reserve, leading to further declines in eucalyp ts. It appears unlikely that a single fire will prevent A. littoralis domin ance, and frequent burning at short intervals may be required to reinstate an open woodland structure.