Fine-scale patchiness of different fire intensities in sandstone heath vegetation in northern Australia

We assessed the extent of burning and rockiness in 3712 5 × 5 m quadrats along 9.2 km of transects sampling five different fires in sandstone heaths where contemporary fire regimes are thought to be reducing the populations of many plants. All fires were patchy, with means of 64% burnt for early dry season and 84% for late dry season fires. Rockiness was strongly related to the presence of unburned patches, and some late dry season fires leave no patches in the absence of rocks. Half of the unburned patches were 10 m or less in length and of the 83 patches identified only three were still detectable when data were amalgamated into quadrats of 500 m2. Thus, very few patches could be recognised from satellite images. The results suggest that fires are much more patchy than satellite-derived fire maps indicate. This has important implications for understanding how populations of fire sensitive plants will respond to different fire regimes.