Bushfire history from grasstrees at Eneabba, Western Australia

摘要

A method for reconstructing bushfire history from fire marks on grasstree stems (Xanthorrlweaspecies) has been suggested for south-western Australia. Depending on the grasstree age, thehistory can extend back for over two centuries. Such history is important in understanding thebehaviour of bushfires and their effect on ecology; in managing them to protect people and theirassets; and for nature conservation. Two critiques of the grasstree method have been published,based on its application in kwongan heath, a few hundred kilometres north of Perth. Both papersextrapolate their criticism to previous grasstree work in vegetation south of Perth, such as thejarrah forest. This paper addresses the second paper, dealing with kwongan data from Eneabba. Ishow that the pattern of agreement between fire intervals derived from grasstrees and satelliteimages, over a thirty year period, is unlikely to occur by chance. Data from grasstrees dating backto the 1920s show a clear lengthening of fire intervals over the twentieth century. Reasons fordisagreement between grasstree and satellite data are discussed. These include the omission ofsome grasstree data, possible errors in grasstree interpretation, and possible errors in satelliteimage interpretation.