SHRUB RECRUITMENT RESPONSE TO INTENSITY AND SEASON OF FIRE IN A SEMIARID WOODLAND

(1) In a fire experiment involving different intensities and seasons over a 2-year period, fire enhanced the germination of two of the seven principal shrub species in a semi-arid shrub-invaded woodland site in eastern Australia. (2) The level of shrub recruitment increased slightly or not at all with higher fire-line intensities. (3) The mortality rate of a fire-enhanced cohort of Cassia eremophila was density-dependent and decreased exponentially over time. (4) The pattern of shrub recruitment across the landscape was strongly influenced by the fire-line intensity; the proportion of 9-m2 quadrats containing seedlings increased linearly with fire-line intensity from 0% for some controls to 100% when intensity reached c. 3000 kW m-1 (depending on the season of the fire). (5) Spring, summer and autumn fires enhanced germination more than winter fires, with the amount and time of post-fire rainfall being influential in governing the proportion of shrub seedlings that established. (6) The density and frequency of fire-recruited shrubs can be manipulated by selecting the season of, and environmental conditions for, prescribed fires.