Fallout radionuclide tracers identify a switch in sediment sources and transport-limited sediment yield following wildfire in a eucalypt forest

Wilkinson, Scott N.; Wallbrink, Peter; Hancock, Gary; Blake, William H.; Shakesby, Richard A.; Doerr, Stefan H.

doi:10.1016/j.geomorph.2009.04.001

Cited by 96 publications

(81 citation statements)

References 45 publications

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“…from surface soil and subsurface/channel bank material) to the fluvial sediment samples collected from the two study watersheds were determined using a two-source unmixing model based on that described by Collins et al (1997) and Walling et al (1999), and used in other similar studies in Australia (e.g. Wilkinson et al 2009;Smith et al 2011b). The goodness-offit provided by the unmixing model was determined by comparing the actual FRN concentrations for the sediment samples with corresponding values predicted by the unmixing model (cf.…”

Section: Study Sitementioning

confidence: 99%

“…Collins et al 1997;Walling et al 1999). This approach to estimate uncertainty differs from that used by Wilkinson et al (2009) and Smith et al (2011b) who used a Monte Carlo-based approach.…”

Section: Study Sitementioning

confidence: 99%

“…Their use within wildfire studies is relatively limited, and work to date has been almost exclusively based within Australia (e.g. Wallbrink et al 2005;Blake et al 2009;Wilkinson et al 2009;Smith et al 2011b). Those studies have shown that these FRNs offer potential to determine changes in sediment sources following wildfire events and furthermore, when coupled with watershed monitoring, to provide a comprehensive evaluation of the response of landscapes to wildfires Smith et al 2011b).…”

Section: Introductionmentioning

confidence: 99%

“…Recent Australian studies (e.g. Wilkinson et al 2009;Smith et al 2011b) have reported: (1) a marked increase (e.g. from ca.…”

Section: Introductionmentioning

confidence: 99%

“…20% pre-fire to ca. 86% immediately post-fire; Wilkinson et al 2009) in the relative contribution from hillslope surface soil materials immediately after wildfire, followed by (2) a decrease in the relative contribution of surface materials after 2-3 years. Against this background, this study aims to determine if post-fire sediment sources in the forests of BC follow a similar pattern.…”

Section: Introductionmentioning

confidence: 99%

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Determining the effects of wildfire on sediment sources using 137Cs and unsupported 210Pb: the role of landscape disturbances and driving forces

et al. 2012

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Purpose Wildfires represent one of the major natural disturbances within forested landscapes and have potential implications for the quality and function of downstream aquatic ecosystems. This study aimed to determine if a wildfire in a mountainous, forested watershed in British Columbia, Canada, caused a change in the dominant sediment source in the immediate 1-2 years following the wildfire, and if the sediment sources changed over the medium term (3-7 years) as the landscape recovered. Materials and methods Source materials (surface soil, subsurface soil and channel bank material) and fluvial (suspended and channel bed) sediment samples were collected over the period 2004 to 2010 from a watershed burnt by a wildfire in 2003, and from an adjacent watershed that was not impacted (FRNs) caesium-137 ( 137 Cs) and unsupported lead-210 ( 210 Pb un ). An unmixing model was used to calculate the relative source contributions of the fluvial sediment samples. Results and discussion 137 Cs and 210 Pb un were concentrated in the upper layers of surface soils in both watersheds and were statistically different to concentrations in subsurface and channel bank material. In the burnt watershed, FRN concentrations were greatest in the ash layer. Sediment sources as determined by the unmixing model were 100% subsurface/channel bank material in the unburnt watershed, while in the burnt watershed 8.5±2.5% was derived from surface soils. In both watersheds, there were no major changes in the relative contributions from surface soil and from subsurface/channel bank material over the period 2004 to 2010. Thus, while the wildfire did cause a change in sediment sources, it was fairly subtle and did not conform to the effects following wildfire described for other studies in contrasting environments, which typically document a major increase in hillslope contributions relative to channel bank sources. Conclusions There was a limited response in terms of finegrained sediment sources (and also sediment fluxes) in the burnt watershed. The reason for this muted response to a severe wildfire is likely to be the lack of precipitation, especially winter precipitation and the associated snowmelt, in the first year following the wildfire. Thus while the landscape was primed for erosion and sediment transport, the lack of a driving force meant that there was a limited immediate postfire sediment response.Keywords Caesium-137 . Wildfire . Disturbance response . Fallout radionuclides . Sediment sources . Unsupported lead-210

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Section: Study Sitementioning

confidence: 99%

Section: Study Sitementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

“…Recent Australian studies (e.g. Wilkinson et al 2009;Smith et al 2011b) have reported: (1) a marked increase (e.g. from ca.…”

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Determining the effects of wildfire on sediment sources using 137Cs and unsupported 210Pb: the role of landscape disturbances and driving forces

et al. 2012

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Illuminating wildfire erosion and deposition patterns with repeat terrestrial lidar

et al. 2016

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Erosion following a wildfire is much greater than background erosion in forests because of wildfire-induced changes to soil erodibility and water infiltration. While many previous studies have documented post-wildfire erosion with point and small plot-scale measurements, the spatial distribution of post-fire erosion patterns at the watershed scale remains largely unexplored. In this study lidar surveys were collected periodically in a small, first-order drainage basin over a period of 2 years following a wildfire. The study site was relatively steep with slopes ranging from 17 ∘ to > 30 ∘ . During the study period, several different types of rain storms occurred on the site including low-intensity frontal storms (2.4 mm h −1 ) and high-intensity convective thunderstorms (79 mm h −1 ). These storms were the dominant drivers of erosion. Erosion resulting from dry ravel and debris flows was notably absent at the site. Successive lidar surveys were subtracted from one another to obtain digital maps of topographic change between surveys. The results show an evolution in geomorphic response, such that the erosional response after rain storms was strongly influenced by the previous erosional events and pre-fire site morphology. Hillslope and channel roughness increased over time, and the watershed armored as coarse cobbles and boulders were exposed. The erosional response was spatially nonuniform; shallow erosion from hillslopes (87% of the study area) contributed 3 times more sediment volume than erosion from convergent areas (13% of the study area). However, the total normalized erosion depth (volume/area) was highest in convergent areas. From a detailed understanding of the spatial locations of erosion, we made inferences regarding the processes driving erosion. It appears that hillslope erosion is controlled by rain splash (for detachment) and overland flow (for transport and quasi-channelized erosion), with the sites of highest erosion corresponding to locations with the lowest roughness. By contrast, in convergent areas we found erosion caused by overland flow. Soil erosion was locally interrupted by immobile objects such as boulders, bedrock, or tree trunks, resulting in a patchy erosion network with increasing roughness over time.

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Peatland restoration: controls on sediment production and reductions in carbon and pollutant export

Shuttleworth

Evans

Hutchinson

et al. 2014

Earth Surf Processes Landf

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Peatlands are an important store of soil carbon, and play a vital role in global carbon cycling, and when located in close proximity to urban and industrial areas, can also act as sinks of atmospherically deposited heavy metals. Large areas of the UK's blanket peat are significantly degraded and actively eroding which negatively impacts carbon and pollutant storage. The restoration of eroding UK peatlands is a major conservation concern, and over the last decade measures have been taken to try to control erosion and restore large areas of degraded peat. This study utilizes a sediment source fingerprinting approach to assess the effect of restoration practices on sediment production, and carbon and pollutant export in the Peak District National Park, southern Pennines (UK). Suspended sediment was collected using time integrated mass flux samplers (TIMS), deployed across three field areas which represent the surface conditions exhibited through an erosion-restoration cycle: (i) intact; (ii) actively eroding; and (iii) recently re-vegetated. Anthropogenic pollutants stored near the peat's surface have allowed material mobilized by sheet erosion to be distinguished from sediment eroded from gully walls. Re-vegetation of eroding gully systems is most effective at stabilizing interfluve surfaces, switching the locus of sediment production from contaminated surface peat to relatively 'clean' gully walls. The stabilization of eroding surfaces reduces particulate organic carbon (POC) and lead (Pb) fluxes by two orders of magnitude, to levels comparable with those of an intact peatland, thus maintaining this important carbon and pollutant store. The re-vegetation of gully floors also plays a key role in decoupling eroding surfaces from the fluvial system, and further reducing the flux of material. These findings indicate that the restoration practices have been effective over a relatively short timescale, and will help target and refine future restoration initiatives.

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Fallout radionuclide tracers identify a switch in sediment sources and transport-limited sediment yield following wildfire in a eucalypt forest

Cited by 96 publications

References 45 publications

Determining the effects of wildfire on sediment sources using 137Cs and unsupported 210Pb: the role of landscape disturbances and driving forces

Determining the effects of wildfire on sediment sources using 137Cs and unsupported 210Pb: the role of landscape disturbances and driving forces

Illuminating wildfire erosion and deposition patterns with repeat terrestrial lidar

Peatland restoration: controls on sediment production and reductions in carbon and pollutant export

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