Fire behaviour on engineered landforms stabilised with high biomass buffel grass

- Rehabilitation method has a significant impact on fire behaviour in semi-arid Australia.
- Grass dominates replaced topsoil; trees and shrubs dominate unamended mine spoil.
- Total fuel loads on topsoil are 43% greater than those on spoil.
- Fireline intensities in grassland on topsoil are double those for woodland on spoil.

Rehabilitated lands created by open-cut coal mines are generally protected by land managers from fire and grazing disturbances. This practice is employed to reduce negative impacts, such as erosion, on the developing ecosystems. However, fire exclusion over long periods inadvertently contributes to increased fire risk on rehabilitated landforms, particularly when high biomass, mono-dominant grasses form a major component of these new ecosystems. In May 2015, an experimental fire burnt 117 ha of rehabilitation at a coal mine site in the Bowen Basin, Australia. Standing grass fuel loads, dominated by buffel grass (Cenchrus ciliaris L.), were up to 9.3 t/ha in grassland areas and 5.3 t/ha in areas of open woodland. Average litter fuel loads were 2.4 and 3.6 t/ha for grassland and open woodland, respectively. Calculated fire intensity was higher in grassland (4612 ± 502 kW m−1) than open woodland areas (1977 ± 804 kW m−1) indicating that rehabilitated landforms dominated by buffel grass may represent a higher fire risk to mine sites and regional areas in the Bowen Basin when compared to the original vegetation. Fire behaviour reflected the varying underlying terrain, fuel loads and surface soil or overburden conditions. Further research is recommended to investigate fire behaviour in buffel grasslands across a range of fuel load and curing conditions, with the aim to develop an invasive grass fire spread model that can be used inform both landscape reconstruction prescriptions for ecological engineers and more broadly in managing the fire risk across landscapes dominated by these vegetation types.