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Effects of fire on the structure and composition of open eucalypt forests

Spencer, R & Baxter, GS 2006, Austral Ecology, vol. 31, pp. 638-646.

Fires can result in dramatic changes to habitat structure and complexity. This study showed that frequent fires on Fraser Island influenced habitat structure and led to a decrease in diversity due to an increase in the dominance of certain plant species. A change in habitat structure is likely to have negative effects on species that depend on certain plants or structural layers in an environment for habitat, shelter or food.

  This study tested how the variability of habitat structure and composition, and abundance of plant species, in the open eucalypt forests of Fraser Island respond to fire frequency. Fires are used in this environment as a management tool predominantly for back burning and wildfire prevention. A total of 37 sites over 19 blocks that had been burnt once or twice between 1982 and 1996 were sampled. At each site, five (10 m x 2 m) vegetation transects were surveyed to identify and quantify all individual plant species, leaf litter, log cover and measure habitat structure. Statistical analysis showed that areas with high fire frequency produced significantly different floristic composition and abundance levels to their pre-burn levels, but also differed between dune systems. For this region, fire frequency was not an accurate predictor of plant composition and abundance due to the presence of dune-specific species. The authors also suggested that nutrient levels were affected by fires, and competition between species impacted the relative diversity and evenness of plant species across the sites. The habitat structure and characteristics of the forest showed a stronger relationship to fire frequencies across the sites, generally with higher numbers of understorey plants in areas frequently burnt and a more even structure of understorey, shrub and canopy cover in areas with lower fire frequency.

  The results of this study demonstrate the impact of frequent fires on the structural characteristics of eucalypt forests, which also have the potential to impact animal species in any location with a frequent fire regime. Generally, small ground-dwelling mammal communities respond well to successional changes in forests and thrive on the increase in understorey plants and grasses that follow these frequent fires. Frequent fire has the potential to negatively impact larger arboreal mammals such as the koala, however, as they depend upon canopy species for food and shelter. Although koalas are not present on Fraser Island, they inhabit the Fraser coast and areas with similar fire regimes such as North Stradbroke Island.

  Fire is an important land management tool and is integral to most Australian ecosystems; however, too high of a fire frequency in some areas can negatively alter the habitat structure and complexity with consequences for wild animals such as the koala. To aid in conservation efforts, the frequency and effects of fires in koala habitat should be assessed to better understand the impacts structural habitat change has on the koala.


Summarised by Robyn Boldy


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