Biogeosciences, 11, 4099-4114, 2014
https://doi.org/10.5194/bg-11-4099-2014
© Author(s) 2014. This work is distributed under
the Creative Commons Attribution 3.0 License.
Research article
04 Aug 2014
Biomass uptake and fire as controls on groundwater solute evolution on a southeast Australian granite: aboriginal land management hypothesis
J. F. Dean1,2,*, J. A. Webb1,2, G. E. Jacobsen3, R. Chisari3, and P. E. Dresel4 1Agricultural Sciences Department, La Trobe University, Bundoora, Victoria, Australia
2National Centre for Groundwater Research and Training, Australia
3Institute for Environmental Research, ANSTO, Sydney, Australia
4Department of Environment and Primary Industries, Bendigo, Victoria, Australia
*now at: Biological and Environmental Sciences, University of Stirling, Scotland
Abstract. The chemical composition of groundwater and surface water is often considered to be dominated by water–rock interactions, particularly weathering; however, it has been increasingly realised that plant uptake can deplete groundwater and surface water of nutrient elements. Here we show, using geochemical mass balance techniques, that water–rock interactions do not control the hydrochemistry at our study site within a granite terrain in southwest Victoria, Australia. Instead the chemical species provided by rainfall are depleted by plant biomass uptake and exported, predominantly through fire. Regular landscape burning by Aboriginal land users is hypothesized to have caused the depletion of chemical species in groundwater for at least the past 20 000 yr by accelerating the export of elements that would otherwise have been stored within the local biomass. These findings are likely to be applicable to silicate terrains throughout southeast Australia, as well as similar lithological and climatic regions elsewhere in the globe, and contrast with studies of groundwater and surface water chemistry in higher rainfall areas of the Northern Hemisphere, where water–rock interactions are the dominant hydrochemical control.

Citation: Dean, J. F., Webb, J. A., Jacobsen, G. E., Chisari, R., and Dresel, P. E.: Biomass uptake and fire as controls on groundwater solute evolution on a southeast Australian granite: aboriginal land management hypothesis, Biogeosciences, 11, 4099-4114, https://doi.org/10.5194/bg-11-4099-2014, 2014.
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