Environment and
History Environment and
History
Environment and History 2(1996): 97-114
The present environment of Australia represents a palimpsest which records a history of past climates, nutrient poor soils, burning, and increasing aridity. The details of the history are not readily disentangled.
The weathering profiles and the nutrient-poor soils associated with their surficial expression may be of great age. Adaptive responses of plants to the nutrient status of the soils may be contemporaneous with and of the same age as the weathering, leaching and initial leached soil formation. Adaptations that developed initially in response to one selective force, e.g., nutrient-poor soils, may subsequently have been co-opted to another purpose such as sclerophylly in resisting wilting during drought, or lignotubers in surviving drought, grazing and burning. The sclerophylly developed by plants in response to nutrient-poor soils makes them fire-prone in the sense of Mutch (1970) which is an adaptation in so far as it promotes sterile ash beds on which seeds germinate free from fungal attack.
Present observations cannot readily be used to interpret past environments. In order to infer the nature of past environments it is necessary to consider geological, climatic and weathering histories as well as the physiological development of the structures being used as evidence to infer past environmental conditions.
It is argued that the origins of fire adaptations may pre-date the arrival of Aborigines, whose influence on the biota may then have been to produce the patterns observed by the early settlers and to eliminate or winnow out those fire sensitive species unable to cope with their cultural practices. Aboriginal use of fire in cultural and hunting practices has only influenced the biota for about 50,000 years which is too short a time to have influenced the biota other than to eliminate, or winnow out, those elements unable to cope with the fire regimes imposed by their cultural practices.
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