Jarrah forest fire history from stem analysis and anthropological evidence

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Abstract
Fire frequencies before and after European settlement were compared by studying stem sections from large, old jarrah (Eucalyptus marginata)trees for fire injury and by relating this to the documented historical evidence. The resilience of jarrah to injury by fire and the limitations of ring counting as an ageing technique, prevented an accurate and definitive reconstruction of the fire frequency prior to European settlement. However, the chronological pattern of fire-caused bole injury supports historical descriptions of fire history and can be explained by broad eras of human activity in the forest. Prior to European settlement, the incidence of fire injury was very low with the average interval between injurious fires being about 81 years. Following European settlement, the frequency of fire injuries increased and the average interval between injuries decreased to about 17 years. The pre-European fire regime in the drier jarrah forest and the forest margin was probably one of frequent, non-injurious, low intensity fires set mainly in summer and autumn, with occasional long intervals between fires ending in high intensity, injurious fires. The increase in fire injury to trees immediately following European settlement and up to the 1950s is probably due to the higher frequency of intense wildfires associated with increased fuel levels resulting from logging and long periods of fire exclusion.