Effects of woody weeds on fuels and fire behaviour in Eastern Australian forests and woodlands.

Abstract

Fire is a common feature in most ecosystems in Australia. Much of the native flora is well adapted to occasional fire and recovers over time in a variety of ways. Invasive species or ‘weeds’ are also a common feature in most Australian ecosystems, particularly in forests and woodlands close to urban settlements. Many invasive species have the potential to recover or recolonise more rapidly following disturbance than native species and may change the fuel load and structure of invaded areas. Invasive species can alter the fuel load and structure providing the fine fuel necessary for initiation and propagation of fire. Woody weeds can also provide elevated biomass to sustain fire and ‘ladder fuels’ allowing fire to reach the canopy. When both of these elements are considered there is the likelihood of alteration of fire behaviour in weed-infested areas of forests and woodlands. The research described in this thesis aims to investigate the effect of invasive species on fire in woodlands of eastern Australia. The fuel load, fuel structure and flammability of pristine (non-invaded) Cumberland Plain Woodland (Australian Botanical Garden, Mount Annan, New South Wales, Australia) and adjacent areas invaded with the woody weed, African Olive (Olea europaea subsp. cuspidata), was assessed and compared. Heavily-invaded areas are comprised of mature trees of African Olive present for more than 15 years, with a continuous canopy and a limited number of species in the understorey were contrasted with areas of ‘intermediate’ invasion, where immature trees of African Olive were interspersed among a grassy/shrubby matrix, and areas of pristine woodland.