Mapping and spatial analysis for savanna wildfire history in northern Australia by remotely sensed data and GIS

This paper presents the results of a study that investigates the implications of bushfires for the pattern of vegetation in the tropical savannas of northern Australia. Fire history maps for a dry season were produced using Landsat Thematic Mapper (TM) data for an area containing typical savanna landscape characteristics, and analysis of pattern was conducted using GIS and landscape ecological measures. Three images captured in the early, middle and late dry season in 1997 were used to produce an unsupervised classification which delineated the extent of burnt patches. These patches were labelled by using a mixture of ground truthing and on-screen assessment of the raw data and signature files for previously confirmed fire scars. Spectral overlap between fire scars, water bodies, shadows and miscellaneous geological features were observed and eliminated by using of a binary spatial mask and the Digital Elevation Model (DEM) for the area. To provide preliminarily an analysis of the spatial changes to pattern in this landscape during the fire season, binary grid fire maps were generated in a GIS and these were used to compute the following spatial pattern indices: number of patches, mean patch size, mean shape index, and mean patch fractal dimension. The fluctuations of these indices illustrate the changes in spatial patterning of vegetation in a savanna landscape that is significantly affected by dry season burning