The effect of fire on natural resources is termed "fire severity" and is related to the energy output of the fire. Recently the term "burn severity" has been introduced to identify the impacts of fire on soil and plants when the fire has been extinguished. This study addresses the assessment of a large wildfire in Gibraltar Range National Park, Australia, through remote sensing of fire severity and explores the spatial relationships between, fire severity and biophysical factors. Burn severity indices were developed from Landsat TM satellite images using pre-fire and post-fire images. Reflectance values computed from Landsat Enhanced Thematic Mapper (ETM) images acquired before and after the fire were used to estimate the Normalised Burn Ratio (NBR), which incorporates the near and mid infrared bands. Spatial distribution of ANBR data were calibrated with field observations and threshold values of burn severity were used to classify fire severity into 5 severity classes per vegetation type. ANBR values were extracted from different representative fire severities and spatial relationships were developed between ANBR and vegetation type, fuel type, fire danger index, time since fire, fire frequency, slope and rockiness in order to account for variables influencing fire severity patterns. General linear models and tests of significance were used to ascertain whether the effects of individual factors were statistically significant. The various models tested showed that no single factor (weather, fuel or landscape) accounted for the burn severity pattern. Fire weather and vegetation type Were found to be the key factors in the models.

Questions: Do endogenous (landscape/vegetation) or exogenous (weather) factors control fire severity? During severe fire weather, is there convergence in fire severity across rain forest, forests and heathlands such that all locations burn with similarly high severity? Are there long-term effects of fire severity in temperate crown-fire ecosystems? Location: Montane rain forests, eucalypt forests and heaths in the temperate climate zone of eastern Australia (Washpool/Gibraltar Range National Park). Methods: The immediate and longer-term effects of fire weather and landscape (terrain, previous fire history and vegetation type) factors on fire severity and ecosystem response were measured using remote sensing and ground measures of microclimate, productivity and plant resprouting at 45 sites. Results: Fire weather strongly interacted with terrain, antecedent fire history and vegetation type, resulting in complex mosaics of mixed fire severity rather than convergence to uniform fire severity. Vegetation type influenced the effects of time-since-fire and fire frequency on fire severity, suggesting differential fire feedbacks. High fire severity left a long-term imprint on total reflectance, ground temperatures and productivity of the vegetation, but these effects were not uniform across vegetation types. The abundance of resprouting species was not strongly affected by fire severity. Conclusions: There was evidence for strong weather control of fire severity but fire history, terrain and vegetation shape the immediate effect due to the contrasting pyrogenic vs pyrophobic nature of the vegetation mosaic. The short-term dominance of weather as a driver of fire severity is only weakly related to the longer-term ecosystem response because of the strong resprouting ability of the canopy dominants, even in rain forest. The forest complexes of eastern Australia appear highly resilient to high fire severity in both structure and floristics, which may influence long-term feedbacks.