Past fires and post-fire impacts reconstructed from a southwest Australian stalagmite
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Date
2021-07-09
Journal Title
Journal ISSN
Volume Title
Publisher
Australasian Quaternary Association (AQUA)
Abstract
Stalagmites provide records of past changes in climate, vegetation, and surface events, with cave dripwaters shown to respond to fires. It is, therefore, most likely that these cave mineral deposits capture the environmental effects of palaeo-wildfires in their chemical and physical properties, as well as the climate conditions antecedent to palaeo-fire events. We analysed multiple proxies in stalagmite (YD-S2) from a shallow cave in south-west Western Australia. Principal Component Analysis revealed that short term peaks in combinations of phosphorus, copper, aluminium, lead and zinc in the stalagmite correspond to the timing of documented fire events occurring in the modern portion of the record. One particularly significant fire event is identified at 1897 ± 5 CE and shows a clear peak in P interpreted to be derived from ash, and a peak in 𝛿18O interpreted to indicate evaporation of sub-surface water during the heat of the fire. A post-fire threshold rise in organic matter content and a shift in calcite fabric associated with higher and more variable drip rates are consistent with a post-fire changes in surface-cave hydrology resulting from heat-induced deformation of the shallow karst bedrock brought about by the intensity of this fire. The combination of climate and fire sensitive proxies in YD-S2 indicates that the 1897 ± 5 CE wildfire was preceded by a multi-decadal dry period. We also identify lower and less variable peak phosphorus concentrations in the pre-European period that are consistent with low-intensity cultural burning by Indigenous Australians. The YD-S2 record shows the potential of stalagmites in capturing the climate-fire relationship and the effects of land-management practices on wildfire frequency and intensity.
Description
Keywords
Fires, Caves, Stable isotopes, Climates, Plants, X-ray fluorescence analysis, Minerals, Environment, Organic matter, Australia
Citation
McDonough, L. K., Treble, P. C., Baker, A., Borsato, A., Frisia, S., Nagra, G., Coleborn, K., Gagan, M, K., Fakra, S. C., & Paterson, D. (2021). Past fires and post-fire impacts reconstructed from a southwest Australian stalagmite. Paper presented to the Australasian Quaternary Association/Friends of the Pleistocene Pop-up Conference 2021, 8-9th July 2021. Retrieved from: http://aqua.org.au/wp-content/uploads/2021/07/Abstract-book-2021-1.pdf