Geophysical imaging of regolith in landscapes along a climate and vegetation gradient in the Chilean coastal cordillera

Bo, Igor Dal; Klotzsche, Anja; Schaller, Mirjam; Ehlers, Todd A.; Kaufmann, Manuela Sarah; Fuentes, Juan Pablo; Vereecken, Harry; Kruk, Jan van der

doi:10.1016/j.catena.2019.04.023

Cited by 25 publications

(39 citation statements)

References 51 publications

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“…The mean differences in bulk densities between NFS and SFS are pronounced but not significant, supporting the results of recent studies which did not find significant differences in most present-day physical and chemical properties of regolith on NFS and SFS in the Coastal Cordillera of Northern Chile (Bernhard et al, 2018;Oeser et al, 2018). Measured soil bulk densities and/or soil depths derived from study sites in the semiarid natural reserve of Santa Gracia, located ~120 km NNE of our study area, are very similar to those derived in this study (Bernhard et al, 2018;Dal Bo et al, 2019;Oeser et al, 2018;555 Owen et al, 2011).…”

Section: Aspect-related Density Contrasts In the Altos De Talinaysupporting

confidence: 84%

“…The tendency towards lower values for ρB,f (and ρB,d, ρd in C1 and C2) and higher values for z on SFS than on NFS might be linked to slope exposure with respect to insolation, causing contrasting microclimatic conditions and thus the observed 540 differences in vegetation cover and presumed differences in soil properties (e.g. Bockheim and Hartemink, 2017;Dal Bo et al, 2019;Gutiérrez-Jurado and Vivoni, 2013;Jenny, 1994;Pelletier and Swetnam, 2017). We found that the aspect-related contrasts in measured densities are especially pronounced close to the thalwegs.…”

Section: Aspect-related Density Contrasts In the Altos De Talinaymentioning

confidence: 99%

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A photogrammetry-based approach for soil bulk density measurements with an emphasis on applications to cosmogenic nuclide analysis

Mohren¹,

Binnie²,

Rink³

et al. 2020

Preprint

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Abstract. The quantification of soil bulk density (ρB) is a cumbersome and time-consuming task when traditional soil density sampling techniques are applied. However, it can be important for terrestrial cosmogenic nuclide (TCN) production rate scaling when deriving ages or surface process rates from buried samples, in particular when short-lived TCN such as in situ 14C are applied. Here we show that soil density determinations can be made using structure-from-motion multi-view stereo (SfM-MVS) photogrammetry-based volume reconstructions of sampling pits. Accuracy and precision tests as found in the literature and as conducted in this study clearly indicate that photographs taken from both a consumer-grade digital single lens mirrorless (DSLM) and a smartphone camera are of sufficient quality to produce accurate and precise modelling results, i.e. to regularly reproduce the true volume and/or density by > 95 %. This finding holds also if a freeware-based computing workflow is applied. The technique has been used to measure ρB along three small-scale (

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Section: Aspect-related Density Contrasts In the Altos De Talinaysupporting

confidence: 84%

Section: Aspect-related Density Contrasts In the Altos De Talinaymentioning

confidence: 99%

A photogrammetry-based approach for soil bulk density measurements with an emphasis on applications to cosmogenic nuclide analysis

Mohren¹,

Binnie²,

Rink³

et al. 2020

Preprint

View full text Add to dashboard Cite

show abstract

“…The amplitude of recycling varies from nutrient to nutrient and site to site. In the arid Pan de Azùcar, nutrients are primarily recycled via photodegradation of shrubs (e.g., Gallo et al, 2006;Day et al, 2015). In the remaining sites Rec X occurs through all organic-bearing soil horizons and increases from Santa Gracia to Nahuelbuta and is highest for Ca (increasing from 1 to 6), K (increasing from 6 to 15), and P (increasing from 5 to 30; Table 5).…”

Section: An Increase In Nutrient Recycling With Nppmentioning

confidence: 99%

Do degree and rate of silicate weathering depend on plant productivity?

Oeser

Blanckenburg

2020

Biogeosciences

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Abstract. Plants and their associated below-ground microbiota possess the tools for rock weathering. Yet the quantitative evaluation of the impact of these biogenic weathering drivers relative to abiogenic parameters, such as the supply of primary minerals, water, and acids, is an open question in Critical Zone research. Here we present a novel strategy to decipher the relative impact of these drivers. We quantified the degree and rate of weathering and compared these to nutrient uptake along the “EarthShape” transect in the Chilean Coastal Cordillera. These sites define a major north–south gradient in precipitation and primary productivity but overlie granitoid rock throughout. We present a dataset of the chemistry of Critical Zone compartments (bedrock, regolith, soil, and vegetation) to quantify the relative loss of soluble elements (the “degree of weathering”) and the inventory of bioavailable elements. We use 87Sr∕86Sr isotope ratios to identify the sources of mineral nutrients to plants. With rates from cosmogenic nuclides and biomass growth we determined fluxes (“weathering rates”), meaning the rate of loss of elements out of the ecosystems, averaged over weathering timescales (millennia), and quantified mineral nutrient recycling between the bulk weathering zone and the bulk vegetation cover. We found that neither the degree of weathering nor the weathering rates increase systematically with precipitation from north to south along the climate and vegetation gradient. Instead, the increase in biomass nutrient demand is accommodated by faster nutrient recycling. In the absence of an increase in weathering rate despite a five-fold increase in precipitation and net primary productivity (NPP), we hypothesize that plant growth might in fact dampen weathering rates. Because plants are thought to be key players in the global silicate weathering–carbon feedback, this hypothesis merits further evaluation.

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“…These four study areas were investigated to qualitatively and quantitatively describe the differences between the four settings. Our previous work in these areas has identified from field observations and GPR-based methods an increase in pedolith thickness from north to south and major and trace element compositional variations within pedons (e.g., Bernhard et al, 2018;Oeser et al, 2018;Dal Bo et al, 2019). However, in our previous GPR work (Dal Bo et al, 2019) we were not able to present a detailed comparison of physical, chemical, and regolith observations, which has yet to be reported for these areas.…”

Section: Introductionmentioning

confidence: 85%

“…Different geophysical techniques have provided a non-invasive or minimally invasive approach to view pedolith variations down to the saprolith and bedrock interface (e.g., Parsekian et al, 2015). Whereas high-frequency GPR has proven suitable for investigating pedolith layering and thickness (e.g., Doolittle et al, 2007;Gerber et al, 2010;Roering et al, 2010;Dal Bo et al, 2019), other methods such as seismics (e.g., Holbrook et al, 2014), electrical resistivity tomography (ERT, e.g., Braun et al, 2009), and low-frequency GPR (e.g., Aranha et al, 2002) are better suited to image saprolith and bedrock interfaces (e.g., Parsekian et al, 2015). GPR methods were also previously used to indirectly measure water flow (e.g., Zhang et al, 2014;Guo et al, 2020) as well as root density (e.g., Hruska et al, 1999;Guo et al, 2013).…”

Section: Introductionmentioning

confidence: 99%

Comparison of regolith physical and chemical characteristics with geophysical data along a climate and ecological gradient, Chilean Coastal Cordillera (26 to 38° S)

Schaller¹,

Bo²,

Ehlers³

et al. 2020

SOIL

Self Cite

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Abstract. We combine geophysical observations from ground-penetrating radar (GPR) with regolith physical and chemical properties from pedons excavated in four study areas spanning 1300 km of the climate and ecological gradient in the Chilean Coastal Cordillera. Our aims are the following: (1) to relate GPR observations to depth-varying regolith physical and weathering-related chemical properties in adjacent pedons and (2) to evaluate the lateral extent to which these properties can be extrapolated along a hillslope using GPR observations. Physical observations considered include regolith bulk density and grain size distribution, whereas chemical observations are based on major and trace element analysis. Results indicate that visually determined pedolith thickness and the transition from the B to C horizons generally correlate with maximums in the 500 and 1000 MHz GPR envelope profiles. To a lesser degree, these maximums in the GPR envelope profiles agree with maximums in weathering-related indices such as the chemical index of alteration (CIA) and the chemical index of mass transfer (τ) for Na. Finally, we find that upscaling from the pedon to hillslope scale is possible with geophysical methods for certain pedon properties. Taken together, these findings suggest that the GPR profiles down hillslopes can be used to infer lateral thickness variations in pedolith horizons in different ecologic and climate settings, and to some degree the physical and chemical variations with depth.

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Geophysical imaging of regolith in landscapes along a climate and vegetation gradient in the Chilean coastal cordillera

Cited by 25 publications

References 51 publications

A photogrammetry-based approach for soil bulk density measurements with an emphasis on applications to cosmogenic nuclide analysis

A photogrammetry-based approach for soil bulk density measurements with an emphasis on applications to cosmogenic nuclide analysis

Do degree and rate of silicate weathering depend on plant productivity?

Comparison of regolith physical and chemical characteristics with geophysical data along a climate and ecological gradient, Chilean Coastal Cordillera (26 to 38° S)

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