Past fires and post-fire impacts reconstructed from a southwest Australian stalagmite

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dc.contributor.authorMcDonough, LKen_AU
dc.contributor.authorTreble, PCen_AU
dc.contributor.authorBaker, AAen_AU
dc.contributor.authorBorsato, Aen_AU
dc.contributor.authorFrisia, Sen_AU
dc.contributor.authorCampbell, Men_AU
dc.contributor.authorNagra, Gen_AU
dc.contributor.authorColeborn, Ken_AU
dc.contributor.authorGagan, MKen_AU
dc.contributor.authorPaterson, DJen_AU
dc.date.accessioned2023-03-27T05:39:15Zen_AU
dc.date.available2023-03-27T05:39:15Zen_AU
dc.date.issued2021-12-17en_AU
dc.date.statistics2023-01-27en_AU
dc.description.abstractStalagmites 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. Plain-language Summary Fires have the potential to be recorded in stalagmites as pulses of ash-derived elements that leach intro dripwater above the cave. These ash-derived elements can then be incorporated into stalagmites as they grow. We analysed a stalagmite from a shallow cave in south-west Western Australia which revealed increases in phosphorus and metals including copper, lead, aluminium and zinc during years when fires are documented to have occurred over the cave. We use peaks in these elements to extend the fire record back to the 1760’s and identify a particularly large fire event in 1897 ± 5. This fire event was intense enough to cause not only an increase in ash-derived elements, but also an increase in the transmission of rainfall between the surface and the cave due to fracturing of the limestone as a result of intense heating and cooling. This event occurred at the end of a known drought period and was likely enhanced by the dry conditions. We also identify evidence for lower-intensity cultural burning by Indigenous Australians in the pre-European period compared to the post-European period, suggesting that changes in land management may also be recorded in stalagmites.en_AU
dc.identifier.articlenumberA45U-2148en_AU
dc.identifier.booktitleAGU Fall Meeting Abstractsen_AU
dc.identifier.citationMcDonough, L., Treble, P. C., Baker, A., Borsato, A., Frisia, S., Campbell, M., Nagra, G., Coleborn, K., Gagan, M. K & Paterson, D. (2021). Past fires and post-fire impacts reconstructed from a southwest Australian stalagmite. Paper presented at the AGU Fall Meeting 2021, New Orleans, Louisiana and Online, 13-17 December 2021. In AGU Fall Meeting Abstracts, Vol. 2021, A45U-2148. Retrieved from: https://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/876004en_AU
dc.identifier.conferenceenddate17 December 2021en_AU
dc.identifier.conferencenameAGU Fall Meeting 2021en_AU
dc.identifier.conferenceplaceNew Orleans, Louisiana and Onlineen_AU
dc.identifier.conferencestartdate13 December 2021en_AU
dc.identifier.urihttps://agu.confex.com/agu/fm21/meetingapp.cgi/Paper/876004en_AU
dc.identifier.urihttps://apo.ansto.gov.au/dspace/handle/10238/14734en_AU
dc.identifier.volume2021en_AU
dc.language.isoenen_AU
dc.publisherAmerican Geophysical Union (AGU)en_AU
dc.subjectCavesen_AU
dc.subjectRecords managementen_AU
dc.subjectClimatic changeen_AU
dc.subjectPlantsen_AU
dc.subjectWateren_AU
dc.subjectMineralsen_AU
dc.subjectFiresen_AU
dc.subjectWestern Australiaen_AU
dc.titlePast fires and post-fire impacts reconstructed from a southwest Australian stalagmiteen_AU
dc.typeConference Presentationen_AU
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