A post-wildfire response in cave dripwater chemistry

Surface disturbances above a cave have the potential to impact cave dripwater discharge, isotopic composition and solute concentrations, which may subsequently be recorded in the stalagmites forming from these dripwaters. One such disturbance is wildfire; however, the effects of wildfire on cave che...

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Main Authors: G. Nagra, P. C. Treble, M. S. Andersen, I. J. Fairchild, K. Coleborn, A. Baker
Format: Article
Language:English
Published: Copernicus Publications 2016-07-01
Series:Hydrology and Earth System Sciences
Online Access:http://www.hydrol-earth-syst-sci.net/20/2745/2016/hess-20-2745-2016.pdf
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author G. Nagra
P. C. Treble
M. S. Andersen
I. J. Fairchild
K. Coleborn
A. Baker
author_facet G. Nagra
P. C. Treble
M. S. Andersen
I. J. Fairchild
K. Coleborn
A. Baker
author_sort G. Nagra
collection DOAJ
description Surface disturbances above a cave have the potential to impact cave dripwater discharge, isotopic composition and solute concentrations, which may subsequently be recorded in the stalagmites forming from these dripwaters. One such disturbance is wildfire; however, the effects of wildfire on cave chemistry and hydrology remains poorly understood. Using dripwater data monitored at two sites in a shallow cave, beneath a forest, in southwest Australia, we provide one of the first cave monitoring studies conducted in a post-fire regime, which seeks to identify the effects of wildfire and post-fire vegetation dynamics on dripwater <i>δ</i><sup>18</sup>O composition and solute concentrations. We compare our post-wildfire <i>δ</i><sup>18</sup>O data with predicted dripwater <i>δ</i><sup>18</sup>O using a forward model based on measured hydro-climatic influences alone. This helps to delineate hydro-climatic and fire-related influences on <i>δ</i><sup>18</sup>O. Further we also compare our data with both data from Golgotha Cave &ndash; which is in a similar environment but was not influenced by this particular fire &ndash; as well as regional groundwater chemistry, in an attempt to determine the extent to which wildfire affects dripwater chemistry. We find in our forested shallow cave that <i>δ</i><sup>18</sup>O is higher after the fire relative to modelled <i>δ</i><sup>18</sup>O. We attribute this to increased evaporation due to reduced albedo and canopy cover. The solute response post-fire varied between the two drip sites: at Site 1a, which had a large tree above it that was lost in the fire, we see a response reflecting both a reduction in tree water use and a removal of nutrients (Cl, Mg, Sr, and Ca) from the surface and subsurface. Solutes such as SO<sub>4</sub> and K maintain high concentrations, due to the abundance of above-ground ash. At Site 2a, which was covered by lower&ndash;middle storey vegetation, we see a solute response reflecting evaporative concentration of all studied ions (Cl, Ca, Mg, Sr, SO<sub>4</sub>, and K) similar to the trend in <i>δ</i><sup>18</sup>O for this drip site. We open a new avenue for speleothem science in fire-prone regions, focusing on the geochemical records of speleothems as potential palaeo-fire archives.
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spelling doaj.art-1af6343d40f24224afb570873140cb7b2022-12-21T22:25:04ZengCopernicus PublicationsHydrology and Earth System Sciences1027-56061607-79382016-07-012072745275810.5194/hess-20-2745-2016A post-wildfire response in cave dripwater chemistryG. Nagra0P. C. Treble1M. S. Andersen2I. J. Fairchild3K. Coleborn4A. Baker5Connected Waters Initiative Research Centre, University of New South Wales, Sydney, NSW, 2052, AustraliaConnected Waters Initiative Research Centre, University of New South Wales, Sydney, NSW, 2052, AustraliaConnected Waters Initiative Research Centre, University of New South Wales, Sydney, NSW, 2052, AustraliaSchool of Geography, Earth and Environmental Sciences, University of Birmingham, Edgbaston, Birmingham, UKConnected Waters Initiative Research Centre, University of New South Wales, Sydney, NSW, 2052, AustraliaConnected Waters Initiative Research Centre, University of New South Wales, Sydney, NSW, 2052, AustraliaSurface disturbances above a cave have the potential to impact cave dripwater discharge, isotopic composition and solute concentrations, which may subsequently be recorded in the stalagmites forming from these dripwaters. One such disturbance is wildfire; however, the effects of wildfire on cave chemistry and hydrology remains poorly understood. Using dripwater data monitored at two sites in a shallow cave, beneath a forest, in southwest Australia, we provide one of the first cave monitoring studies conducted in a post-fire regime, which seeks to identify the effects of wildfire and post-fire vegetation dynamics on dripwater <i>δ</i><sup>18</sup>O composition and solute concentrations. We compare our post-wildfire <i>δ</i><sup>18</sup>O data with predicted dripwater <i>δ</i><sup>18</sup>O using a forward model based on measured hydro-climatic influences alone. This helps to delineate hydro-climatic and fire-related influences on <i>δ</i><sup>18</sup>O. Further we also compare our data with both data from Golgotha Cave &ndash; which is in a similar environment but was not influenced by this particular fire &ndash; as well as regional groundwater chemistry, in an attempt to determine the extent to which wildfire affects dripwater chemistry. We find in our forested shallow cave that <i>δ</i><sup>18</sup>O is higher after the fire relative to modelled <i>δ</i><sup>18</sup>O. We attribute this to increased evaporation due to reduced albedo and canopy cover. The solute response post-fire varied between the two drip sites: at Site 1a, which had a large tree above it that was lost in the fire, we see a response reflecting both a reduction in tree water use and a removal of nutrients (Cl, Mg, Sr, and Ca) from the surface and subsurface. Solutes such as SO<sub>4</sub> and K maintain high concentrations, due to the abundance of above-ground ash. At Site 2a, which was covered by lower&ndash;middle storey vegetation, we see a solute response reflecting evaporative concentration of all studied ions (Cl, Ca, Mg, Sr, SO<sub>4</sub>, and K) similar to the trend in <i>δ</i><sup>18</sup>O for this drip site. We open a new avenue for speleothem science in fire-prone regions, focusing on the geochemical records of speleothems as potential palaeo-fire archives.http://www.hydrol-earth-syst-sci.net/20/2745/2016/hess-20-2745-2016.pdf
spellingShingle G. Nagra
P. C. Treble
M. S. Andersen
I. J. Fairchild
K. Coleborn
A. Baker
A post-wildfire response in cave dripwater chemistry
Hydrology and Earth System Sciences
title A post-wildfire response in cave dripwater chemistry
title_full A post-wildfire response in cave dripwater chemistry
title_fullStr A post-wildfire response in cave dripwater chemistry
title_full_unstemmed A post-wildfire response in cave dripwater chemistry
title_short A post-wildfire response in cave dripwater chemistry
title_sort post wildfire response in cave dripwater chemistry
url http://www.hydrol-earth-syst-sci.net/20/2745/2016/hess-20-2745-2016.pdf
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