Effects of ﬁre on the structure and composition of open eucalypt forests
RICKY-JOHN SPENCER1,2* AND GREGORY S. BAXTER1
1 Fraser Island Fire Ecology Group (FIFEG), School of Natural and Rural Systems Management, University of Queensland, Gatton, Qld 4343, Australia (Email: )
2 Pestat Ltd. LPO Box 5055, University of Canberra, Bruce, ACT 2617, Australia
Fires are integral to the healthy functioning of most ecosystems and are often poorly understood in policy and management, however, the relationship between ﬂoristic composition and habitat structure is intrinsically linked, particularly after ﬁre. The aim of this study was to test whether the variability of habitat structure or ﬂoristic composition and abundance in forests at a regional scale can be explained in terms of ﬁre frequency using historical data and experimental prescribed burns. We tested this hypothesis in open eucalypt forests of Fraser Island off the east coast of Australia. Fraser Island dunes show progressive stages in plant succession as access to nutrients decreases across the Island. We found that ﬁre frequency was not a good predictor of ﬂoristic composition or abundance across dune systems; rather, its affects were dune speciﬁc. In contrast, habitat structure was strongly inﬂuenced by ﬁre frequency, independent of dune system. A dense understorey occurred in frequently burnt areas, whereas infrequently burnt areas had a more even distribution of plant heights. Plant communities returned to pre-burn levels of composition and abundances within 6 months of a ﬁre and frequently burnt areas were dominated by early successional species of plant. These ecosystems were characterized by low diversity and frequently burnt areas on the east coast were dominated by Pteridium. Greater midstorey canopy cover in low frequency areas reduces light penetration and allows other species to compete more effectively with Pteridium. Our results strongly indicate that frequent ﬁres on the Island have resulted in a decrease in relative diversity through dominance of several species. Prescribed ﬁre represents a powerful management tool to shape habitat structure and complexity of Fraser Island forests.