Quantification of colloidal and aqueous element transfer in soils: The dual-phase mass balance model

Bern, Carleton R.; Thompson, Aaron; Chadwick, Oliver A.

doi:10.1016/j.gca.2014.12.008

Cited by 33 publications

(26 citation statements)

References 73 publications

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“…We observed significant illuvial clay throughout this pit. The other pits at the wet site support the deep chemical weathering inferred from the collapsed saprolite observed at the crest (Khomo et al, ; Bern et al, ). Chemical weathering rates inferred from the wet site's CDF values range from about 0.5 m/Ma at the slope base to 2.2 m/Ma above the seep zone and average 1.4 m/Ma.…”

Section: Resultssupporting

confidence: 64%

“…In this case, the ratio of chemically immobile [Zr] in saprolite to the parent material [Zr], which is the [Zr] of unweathered rock, yields the fraction of denudation due to chemical weathering (Dixon et al, ; Riebe and Granger, ). At the intermediate and wet sites this methodology is complicated by extensive downslope clay translocation (Khomo et al, ; Khomo et al, ; Bern et al, ) such that the isovolumetric weathering assumption necessary to apply this factor may be violated by either removal or by deposition. We therefore estimate losses due to chemical weathering using the average [Zr] for the fine fraction most susceptible to weathering (see Supplementary Materials).…”

Section: Methodsmentioning

confidence: 99%

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Quantifying erosional equilibrium across a slowly eroding, soil mantled landscape

Heimsath

Chadwick

Roering

et al. 2020

Earth Surf Processes Landf

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The textbook concept of an equilibrium landscape, which posits that soil production and erosion are balanced and equal channel incision, is rarely quantified for natural systems. In contrast to mountainous, rapidly eroding terrain, low relief and slow‐eroding landscapes are poorly studied despite being widespread and densely inhabited. We use three field sites along a climosequence in South Africa to quantify very slow (2‐5 m/My) soil production rates that do not vary across hillslopes or with climate. We show these rates to be indistinguishable from spatially invariant catchment‐average erosion rates while soil depth and chemical weathering increase strongly with rainfall across our sites. Our analyses imply landscape‐scale equilibrium although the dominant means of denudation varies from physical weathering in dry climates to chemical weathering in wet climates. In the two wetter sites, chemical weathering is so significant that clay translocates both vertically in soil columns and horizontally down hillslope catenas, resulting in particle size variation and the accumulation of buried stone lines at the clay‐rich depth. We infer hundred‐thousand‐year residence times of these stone lines and suggest that bioturbation by termites plays a key role in exhuming sediment into the mobile soil layer from significant depths below the clay layer. Our results suggest how tradeoffs in physical and chemical weathering, potentially modulated by biological processes, shape slowly eroding, equilibrium landscapes. © 2019 John Wiley & Sons, Ltd.

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Section: Resultssupporting

confidence: 64%

Section: Methodsmentioning

confidence: 99%

Quantifying erosional equilibrium across a slowly eroding, soil mantled landscape

Heimsath

Chadwick

Roering

et al. 2020

Earth Surf Processes Landf

Self Cite

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“…Mass fraction lost or gained, τ j ,s , for each element was calculated as (Bern et al. ):

{italicτ}_{j, s} = (\frac{C_{j, s}}{C_{j, p}} \times \frac{C_{i, p}}{C_{i, s}}) - 1

…”

Section: Methodsmentioning

confidence: 99%

Controls on carbon storage and weathering in volcanic soils across a high‐elevation climate gradient on Mauna Kea, Hawaii

Kramer

Chadwick

2016

Ecology

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Abstract. Volcanic ash soils retain the largest and most persistent soil carbon pools of any ecosystem. However, the mechanisms governing soil carbon accumulation and weathering during initial phases of ecosystem development are not well understood. We examined soil organic matter dynamics and soil development across a high-altitude (3,560-3,030 m) 20-kyr climate gradient on Mauna Kea in Hawaii. Four elevation sites were selected (~250-500 mm rainfall), which range from sparsely vegetated to sites that contain a mix of shrubs and grasses. At each site, two or three pits were dug and major diagnostic horizons down to bedrock (intact lava) were sampled. Soils were analyzed for particle size, organic C and N, soil pH, exchangeable cations, base saturation, NaF pH, phosphorous sorption, and major elements. Mass loss and pedogenic metal accumulation (hydroxlamine Fe, Al, and Si extractions) were used to measure extent of weathering, leaching, changes in soil mineralogy and carbon accumulation. Reactivephase (SRO) minerals show a general trend of increasing abundance with increasing rainfall. However carbon accumulation patterns across the climate gradient are largely decoupled from these trends. The results suggest that after 20 kyr, pedogenic processes have altered the nature and composition of the volcanic ash such that it is capable of retaining soil C even where organic acid influences from plant material and leaching from rainfall are severely limited. Carbon storage comparisons with lower-elevation soils on Mauna Kea and other moist mesic (2,500 mm rainfall) sites on Hawaii suggest that these soils have reached only between 1% and 15% of their capacity to retain carbon. Our results suggest that, after 20 kyr in low rainfall and a cold climate, weathering was decoupled from soil carbon accumulation patterns and the associated influence of vegetation on soil development. Overall, we conclude that the rate of carbon supply to the subsoil (driven by coupling of rainfall above ground plant production) is a governing factor of forms and amount of soil organic matter accumulation, while soil mineralogy remained relatively uniform.

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“…Those lithologies that form soils with low plasma : skeleton ratios are more likely to have Plimited ecosystems (Hahm et al, 2014) and therefore be influenced by differences in dust inputs (Aciego et al, 2017). Such low plasma : skeleton lithologies are also more likely to develop strong local P gradients due to hydrological redistribution along hillslopes Bern et al, 2015). This can in turn create local patchiness in vegetation type and productivity (Venter et al, 2003).…”

Section: Hypothesismentioning

confidence: 99%

Reviews and syntheses: on the roles trees play in building and plumbing the critical zone

et al. 2017

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Abstract. Trees, the most successful biological power plants on earth, build and plumb the critical zone (CZ) in ways that we do not yet understand. To encourage exploration of the character and implications of interactions between trees and soil in the CZ, we propose nine hypotheses that can be tested at diverse settings. The hypotheses are roughly divided into those about the architecture (building) and those about the water (plumbing) in the CZ, but the two functions are intertwined. Depending upon one's disciplinary background, many of the nine hypotheses listed below may appear obviously true or obviously false. (1) Tree roots can only physically penetrate and biogeochemically comminute the immobile substrate underlying mobile soil where that underlying substrate is fractured or pre-weathered. (2) In settings where the thickness of weathered material, H , is large, trees primarily shape the CZ through biogeochemical reactions within the rooting zone. (3) In forested uplands, the thickness of mobile soil, h, can evolve toward a steady state because of feedbacks related to root disruption and tree throw. (4) In settings where h H and the rates of uplift and erosion are low, the uptake of phosphorus into trees is buffered by the fine-grained fraction of the soil, and the ultimate source of this phosphorus is dust. (5) In settings of limited water availability, trees maintain the highest length density of functional roots at depths where water can be extracted over most of the growing season with the least amount of energy expenditure. (6) Trees grow the majority of their roots in the zone where the most growth-limiting resource is abundant, but they also grow roots at other depths to forage for other resources and to hydraulically redistribute those resources to depths where they can be taken up more efficiently. (7) Trees rely on matrix water in the unsaturated zone that at times may have anPublished by Copernicus Publications on behalf of the European Geosciences Union. 5116 S. L. Brantley et al.: Reviews and syntheses: on the roles trees play in building and plumbing the critical zone isotopic composition distinct from the gravity-drained water that transits from the hillslope to groundwater and streamflow. (8) Mycorrhizal fungi can use matrix water directly, but trees can only use this water by accessing it indirectly through the fungi. (9) Even trees growing well above the valley floor of a catchment can directly affect stream chemistry where changes in permeability near the rooting zone promote intermittent zones of water saturation and downslope flow of water to the stream. By testing these nine hypotheses, we will generate important new cross-disciplinary insights that advance CZ science.

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Quantification of colloidal and aqueous element transfer in soils: The dual-phase mass balance model

Cited by 33 publications

References 73 publications

Quantifying erosional equilibrium across a slowly eroding, soil mantled landscape

Quantifying erosional equilibrium across a slowly eroding, soil mantled landscape

Controls on carbon storage and weathering in volcanic soils across a high‐elevation climate gradient on Mauna Kea, Hawaii

Reviews and syntheses: on the roles trees play in building and plumbing the critical zone

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