Mapping fire severity and fire extent in forest in Victoria for ecological and fuel outcomes

This study shows how high-resolution (similar to 15cm) simultaneous colour and infra-red digital aerial photography can be used to map both fire severity and, particularly, fire extent, in forest in south-eastern Australia. The results show that this methodology is capable of detecting and mapping burnt and unburnt edges under unaffected forest canopy (i.e. still green) - that is, revealing the mosaic of burnt and unburnt areas that often result from planned landscape burning under mild weather conditions (i.e. with little of the brownish canopy scorch that results from more intense bushfires). This has important implications for both fuel management and ecology. It can answer the basic questions of fire and biodiversity managers following planned burning -'how much of the planned area burnt, and, within the burnt area, what aspects were burnt, and how hot did they burn?' The analysis of fire extent by aspect showed that about 80% of southern and eastern aspects remained unburnt during broadscale autumn prescribed burning, with many of these moister aspects potentially providing longer unburnt refuges over multiple burn rotations. The fire severity and extent mapping products, produced using the methodology outlined in this study, have the potential to substantially increase the understanding of the ecological and fuel outcomes of landscape-scale autumn prescribed burning.