Earth, rain and fire – a trinity of the Australian landscape

Aboriginal Australians used fire to improve productivity of the landscape and to clear land for easier travel or hunting. Different parts of the landscape were burned at different frequencies and at different times, depending on soil characteristics and climate.

In grasslands on the fertile basalt plains in Victoria the starchy root of the daisy Microseris scapigera was an important food for the Koori people. The daisy was encouraged with frequent burning to lower competition from the dominant kangaroo grass (Themeda australis). In contrast, nutrient-poor heathlands were burned less frequently to stimulate ephemeral grasses and herbs that attracted grazing animals.

Plant reproductive traits in fire-prone environments are attuned to the season when fire occurs. In the southern heathlands fires occur mainly in summer or autumn at intervals of 10–30 years. Many species have seed banks either in persistent fruits or ‘cones’ (serotinous seed banks) or in the soil. Serotinous cones release seeds when the plant is burned and killed. Smoke chemicals frequently break seed dormancy so soil-stored seeds germinate when moisture is available (Chapter 12). This happens soon after summer or autumn fires. However, if fires occur in spring, seeds released are exposed to possible predation and desiccation for over 6 months before rainfall. Spring fires favour ‘resprouter’ species.