Shrub recruitment response to intensity and season of fire in a semi-arid woodland.
Abstract
The effect was studied of prescribed fire on the pattern and level of seedling recruitment of 7 shrubs (Eremophila mitchellii, E. sturtii, Geijera parviflora, Acacia aneura, A. excelsa, Cassia eremophila var. eremophila and var. zygophylla) and Dodonaea viscosa subsp. spatulata in Eucalyptus intertexta/E. populnea dominated woodland in New South Wales from 1977 to 1979. Germination of C. eremophila and D. viscosa was enhanced by fire. The level of shrub recruitment increased only slightly or not at all with higher fire-line intensities. The mortality rate of a fire-enhanced cohort of Cassia eremophila was density-dependent and decreased exponentially over time. The pattern of shrub recruitment across the landscape was 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 about 3000 kW/m (depending on the season of the fire). Spring, summer and autumn fires enhanced germination more than winter fires; the amount and time of post-fire rainfall influenced the proportion of shrub seedlings that established. It is concluded that the density and frequency of fire-recruited shrubs can be manipulated by selecting the season of, and environmental conditions for, prescribed fires.