Reducing the abundance of Banksia grandis in the jarrah forest by the use of controlled fire

Summary

The role of fire in reducing the abundance of Banksia grandis, a forest understorey species which is susceptible to the dieback disease Phytophthora cinnamomi, was investigated by lighting small experimental fires in jarrah forests (Eucalyptus marginata) over the dry summer months of 1980. The effect of a range of fire intensities on mortality and sprouting ability of B. grandis was examined two years after burning.

The number and size of stems killed to ground level by fire was directly related to fire intensity and varied from little effect of low intensity fires (<350 kW/m) on population density and basal area, to a large effect of moderate intensity fires (1001–1500 kW/m) in which all plants were killed to ground level. The ability of B. grandis to resprout from a lignotuber declined with increasing stem size and plant age.

A combination of moderate intensity fire (~ 1000 kW/m) to kill most stems to ground level, followed by herbicide treatment of residuals is proposed as a cost-effective method of reducing the abundance of B. grandis. The initial moderate intensity fire would be best achieved by allowing forest litter fuels to accumulate and then by burning these fuels under mild weather conditions in summer or early autumn when fuels are dry. Thereafter, further regrowth would be controlled by the periodic low intensity fuel reduction fires, provided stem diameter of the regrowth did not exceed 4 cm.