Regeneration and Survival of Indigenous Dry Sclerophyll Species in the Brisbane Ranges, Victoria, After a Phytophthora cinnamomi Epidemic

Abstract

Changes in the distribution of both pathogen and flora provided data on pathogen decline and on survival, colonisation and regeneration of plant species in defined plots in open dry sclerophyll forests of the Brisbane Ranges 23-30 years after invasion by Phytophthora cinnamomi. The density of the stringybark eucalypts (Eucalyptus informal subgenus Monocalyptus) which dominate the overstorey was halved on some plots. The survivors now show vigorous crown growth but few seedlings are present. Regeneration of the understorey occurred in three stages. Firstly, resistant sedges and then seedlings of resistant opportunists rapidly colonised ground left vacant by the destruction of the dominant understorey species, Xanthorrhoea australis. In the second stage, moderately susceptible species such as Banksia marginata and Grevillea steiglitziana resprouted from old stumps and prostrate legumes increased their ground cover. In the third stage some highly susceptible species, such as X. australis, Dillwynia glaberrima, Hibbertia stricta and Monotoca scoparia have regenerated from seed on sites previously badly affected by the pathogen. Some plants of these species have survived for 10 years, despite the continued presence of scattered pockets infected with of P. cinnamomi. However, Isopogon ceratophyllus, frequent in the understorey of the plot prior to disease, has not regenerated.