Connectivity and percolation of structural pore networks in a cultivated silt loam soil quantified by X-ray tomography

Jarvis, Nicholas; Larsbo, Mats; Koestel, John

doi:10.1016/j.geoderma.2016.06.026

Cited by 117 publications

(70 citation statements)

References 42 publications

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“…However, K s was only marginally affected in the two remaining samples (Babko, ). As also found by Jarvis et al () and predicted by percolation theory, the connectivity of the structural pore space in our data set decreases significantly as the imaged porosity decreases toward a threshold value for long‐range continuity (or percolation; Figure ). Furthermore, during saturation entrapped air will tend to collect in the larger pores (Sněhota et al, ).…”

Section: Resultssupporting

confidence: 89%

“…The first assumption may be reasonable for many naturally structured soils, although some of our samples may not have met this requirement (e.g., the packed sands amended by organic matter and the natural sandy loam soils; Table ). With regard to the second assumption, it seems highly probable that for the size of our samples, the structural pore space imaged by X‐ray cannot be adequately described as the outcome of a spatially uncorrelated (random) arrangement of pore space (see the examples in Figures a–d; Jarvis et al, ). If these assumptions are not met, flow may be less localized than is envisioned in classical CPA (e.g., Bernabé & Bruderer, ; Friedman & Seaton, ; Skaggs, , ) and theoretical predictions of the relative electrical conductivity (effective porosity) and the coefficient G will be less reliable.…”

Section: Resultsmentioning

confidence: 99%

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Estimating the Permeability of Naturally Structured Soil From Percolation Theory and Pore Space Characteristics Imaged by X‐Ray

Koestel

Dathe

Skaggs

et al. 2018

Water Resources Research

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The saturated hydraulic conductivity of soil, Ks, is a critical parameter in hydrological models that remains notoriously difficult to predict. In this study, we test the capability of a model based on percolation theory and critical path analysis to estimate Ks measured on 95 undisturbed soil cores collected from contrasting soil types. One parameter (the pore geometry factor) was derived by model fitting, while the remaining two parameters (the critical pore diameter, dc, and the effective porosity) were derived from X‐ray computed tomography measurements. The model gave a highly significant fit to the Ks measurements (p < 0.0001) although only ~47% of the variation was explained and the fitted pore geometry factor was approximately 1 to 2 orders of magnitude larger than various theoretical values obtained for idealized porous media and pore network models. Apart from assumptions in the model that might not hold in reality, this could also be attributed to experimental error induced by, for example, air entrapment and changes in the soil pore structure occurring during sample presaturation and the measurement of Ks. Variation in the critical pore diameter, dc, was the dominant source of variation in Ks, which suggests that dc is a suitable length scale for predicting soil permeability. Thus, from the point of view of pedotransfer functions, it could be worthwhile to direct future research toward exploring the correlations of dc with basic soil properties and site attributes.

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Section: Resultssupporting

confidence: 89%

Section: Resultsmentioning

confidence: 99%

Estimating the Permeability of Naturally Structured Soil From Percolation Theory and Pore Space Characteristics Imaged by X‐Ray

Koestel

Dathe

Skaggs

et al. 2018

Water Resources Research

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“…() and Jarvis et al . (2017b) who showed that CT resulted in larger X‐ray resolvable porosities in samples taken closer to the soil surface. This was not the case for samples taken under natural vegetation (grass and herbs) where the X‐ray‐derived porosity was more constant with depth (Munoz‐Ortega et al ., ).…”

Section: Resultsmentioning

confidence: 99%

Effects of tillage and liming on macropore networks derived from X‐ray tomography images of a silty clay soil

Hellner

Koestel

Ulén

et al. 2018

Soil Use and Management

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Soil structure influences water infiltration, aeration and root growth and, thereby, also the conditions for sustainable crop production. Our objective was to quantify the effects of different soil management methods and land uses on the topsoil structure of a silty clay soil. We sampled 32 intact soil columns (18 cm high, 12.7 cm diameter) from an experimental silty clay field with four treatments: conventional tillage (CT), conventional tillage followed by liming (CTL), reduced tillage (RT) and unfertilized fallow (UF). The columns were analysed using 3‐D X‐ray tomography. The samples were taken in autumn after harvest, 7 yr after quick lime was applied to the CTL plots. Despite a relatively large number of replicates per treatment (8, 8, 8 and 6 (two UF samples were excluded), respectively), there were no significant differences between any of the investigated macropore network properties related to tilled treatments. The UF treatment, in contrast, exhibited more vertically oriented macropores, which were also better connected compared to the other treatments. This confirms previous findings that tillage may disrupt the vertical continuity of macropore clusters. The impact of liming on soil pore network properties may have been limited to pores smaller than the resolution in our X‐ray images. It is also possible that the effects of lime on soil structure were limited to a few years which means that any effect would have diminished by the time of this study. These matters should be further investigated in follow‐up studies to understand better the potential of lime amendments to clay soil.

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“…The different height changes corresponding to samples of different bulk density can be attributed to less compaction because of reduced pore volume, surface densification by close‐packing of particles after aggregate collapse (Bedaiwy & Rolston, ), and hydraulic conductivity of each sample. However, natural macro pore conductivity (Jarvis, Larsbo, & Koestel, ) is disturbed due to the artificial compaction of the samples. This should be taken into account when comparing laboratory results to field conditions as soil hydrodynamics are dependent on unimpaired grown pore structures on an interaggregate level (Alaoui, Lipiec, & Gerke, ).…”

Section: Resultsmentioning

confidence: 99%

Addressing uncertainties in interpreting soil surface changes by multitemporal high‐resolution topography data across scales

Kaiser

Erhardt²,

Eltner

2018

Land Degrad Dev

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Extensive amounts of water erosion combined with the magnitude of on‐site and off‐site impacts have led to considerable reduction in soil fertility and increased production costs in agriculture. Digital elevation models are a useful and established tool to better understand surface processes and to quantify damages. Ongoing developments in camera‐based 3D reconstruction allow non‐expert users to produce high‐quality elevation models. Multitemporal surveys allow geomorphic change detection serving as a valuable tool for geomorphologists and erosion researchers. Despite various benefits, these recent developments are accompanied by novel challenges in the form of small‐scale nonerosive surface processes (e.g., swelling/shrinking, consolidation/compaction, and aggregate breakdown). If neglected, these alterations can sum up to distinct errors in soil loss quantification. However, as yet, there have been no studies discussing their influence on surface data sets in erosion research. We present an across‐scales approach of visualising and quantifying detailed soil physical changes and their influence on surface morphology at submillimetre resolution. The data sets were acquired at field scale from an unmanned airborne vehicle, at plot scale during an artificial rainfall simulation on an agricultural site, and at microplot scale in a laboratory set‐up. Resulting high‐precision data sets enable the desired insights in soil movements and surface alterations without preceding particle transport and soil loss. Surface changes sum up to 260 m3/ha on an Andalusian test site and could be falsely interpreted as soil loss (of 286 t/ha). These results recommend cautious interpretation of high‐resolution topography in soil erosion research.

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Connectivity and percolation of structural pore networks in a cultivated silt loam soil quantified by X-ray tomography

Cited by 117 publications

References 42 publications

Estimating the Permeability of Naturally Structured Soil From Percolation Theory and Pore Space Characteristics Imaged by X‐Ray

Estimating the Permeability of Naturally Structured Soil From Percolation Theory and Pore Space Characteristics Imaged by X‐Ray

Effects of tillage and liming on macropore networks derived from X‐ray tomography images of a silty clay soil

Addressing uncertainties in interpreting soil surface changes by multitemporal high‐resolution topography data across scales

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