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  • 1
    Online Resource
    Online Resource
    Wiley ; 2012
    In:  Vadose Zone Journal Vol. 11, No. 3 ( 2012-08), p. vzj2011.0120-
    In: Vadose Zone Journal, Wiley, Vol. 11, No. 3 ( 2012-08), p. vzj2011.0120-
    Type of Medium: Online Resource
    ISSN: 1539-1663
    Language: English
    Publisher: Wiley
    Publication Date: 2012
    detail.hit.zdb_id: 2088189-7
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  • 2
    In: Ecohydrology, Wiley, Vol. 11, No. 6 ( 2018-09)
    Abstract: By applying the newly developed flow cell (FC) concept, this study investigated the impact of small‐scale spatial variations (millimetre to centimetre) in organic matter (OM) composition (diffusive reflectance infrared Fourier transform spectroscopy), biological activity (zymography), and wettability (contact angle [CA]) on transport processes (tracer experiments, radiography). Experiments were conducted in five undisturbed soil slices (millimetre apart), consisting of a sandy matrix with an embedded loamy band. In the loamy band increased enzyme activities and OM (10 mm apart) were found compared with the sand matrix, with no interrelations although spatial autocorrelation ranges were up to 7 cm. CAs were increased (0–110°) above the loamy band and were negatively correlated with acid phosphatase. Missing correlations were probably attributed to texture variations between soil slices. A general correlation between CA and C content (bulk) were confirmed. Variability in texture and hydraulic properties led to the formation of heterogeneous flow patterns and probably to heterogeneously distributed interfacial properties. The new FC concept allows process evaluation on the millimetre scale to analyse spatial relations, that is, between small‐scale textural changes on transport processes and biological responses. The concept has been proved as a versatile tool to analyse spatial distribution of biological and interfacial soil properties in conjunction with the analysis of complex micro‐hydraulic processes for undisturbed soil samples. The concept may be improved by additional nondestructive imaging methods, which is especially challenging for the detection of small‐scale textural changes.
    Type of Medium: Online Resource
    ISSN: 1936-0584 , 1936-0592
    URL: Issue
    Language: English
    Publisher: Wiley
    Publication Date: 2018
    detail.hit.zdb_id: 2418105-5
    SSG: 12
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  • 3
    In: European Journal of Soil Science, Wiley, Vol. 73, No. 1 ( 2022-01)
    Abstract: Soil functions, including climate regulation and the cycling of water and nutrients, are of central importance for a number of environmental issues of great societal concern. To understand and manage these functions, it is crucial to be able to quantify the structure of soils, now increasingly referred to as their “architecture,” as it constraints the physical, chemical and biological processes in soils. This quantification was traditionally approached from two different angles, one focused on aggregates of the solid phase, and the other on the pore space. The recent development of sophisticated, non‐disturbing imaging techniques has led to significant progress in the description of soil architecture, in terms of both the pore space and the spatial configuration of mineral and organic materials. We now have direct access to virtually all aspects of soil architecture. In the present article, we review how this affects the perception of soil architecture specifically when trying to describe the functions of soils. A key conclusion of our analysis is that soil architecture, in that context, imperatively needs to be explored in its natural state, with as little disturbance as possible. The same requirement applies to the key processes taking place in the hierarchical soil pore network, including those contributing to the emergence of a heterogeneous organo‐mineral soil matrix by various mixing processes, such as bioturbation, diffusion, microbial metabolism and organo‐mineral interactions. Artificially isolated aggregates are fundamentally inappropriate for deriving conclusions about the functioning of an intact soil. To fully account for soil functions, we argue that a holistic approach that centres on the pore space is mandatory while the dismantlement of soils into chunks may still be carried out to study the binding of soil solid components. In the future, significant progress is expected along this holistic direction, as new, advanced technologies become available. Highlights We highlight the crucial importance of the temporal dynamics of soil architecture for biological activity and carbon turnover. We reconcile controversial concepts relative to how soil architecture is formed and reshaped with time. Soil is demonstrated to be a heterogeneous porous matrix and not an assembly of aggregates. Biological and physical mixing processes are key for the formation and dynamics of soil architecture.
    Type of Medium: Online Resource
    ISSN: 1351-0754 , 1365-2389
    URL: Issue
    Language: English
    Publisher: Wiley
    Publication Date: 2022
    detail.hit.zdb_id: 240830-2
    detail.hit.zdb_id: 2020243-X
    detail.hit.zdb_id: 1191614-X
    SSG: 13
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  • 4
    In: Vadose Zone Journal, Wiley, Vol. 10, No. 3 ( 2011-08), p. 988-998
    Abstract: Recent studies have shown that rhizosphere hydraulic properties may differ from those of the bulk soil. Specifically, mucilage at the root–soil interface may increase the rhizosphere water holding capacity and hydraulic conductivity during drying. The goal of this study was to point out the implications of such altered rhizosphere hydraulic properties for soil–plant water relations. We addressed this problem through modeling based on a steady‐rate approach. We calculated the water flow toward a single root assuming that the rhizosphere and bulk soil were two concentric cylinders having different hydraulic properties. Based on our previous experimental results, we assumed that the rhizosphere had higher water holding capacity and unsaturated conductivity than the bulk soil. The results showed that the water potential gradients in the rhizosphere were much smaller than in the bulk soil. The consequence is that the rhizosphere attenuated and delayed the drop in water potential in the vicinity of the root surface when the soil dried. This led to increased water availability to plants, as well as to higher effective conductivity under unsaturated conditions. The reasons were two: (i) thanks to the high unsaturated conductivity of the rhizosphere, the radius of water uptake was extended from the root to the rhizosphere surface; and (ii) thanks to the high soil water capacity of the rhizosphere, the water depletion in the bulk soil was compensated by water depletion in the rhizosphere. We conclude that under the assumed conditions, the rhizosphere works as an optimal hydraulic conductor and as a reservoir of water that can be taken up when water in the bulk soil becomes limiting.
    Type of Medium: Online Resource
    ISSN: 1539-1663 , 1539-1663
    Language: English
    Publisher: Wiley
    Publication Date: 2011
    detail.hit.zdb_id: 2088189-7
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  • 5
    Online Resource
    Online Resource
    Wiley ; 2015
    In:  Vadose Zone Journal Vol. 14, No. 5 ( 2015-05), p. 1-9
    In: Vadose Zone Journal, Wiley, Vol. 14, No. 5 ( 2015-05), p. 1-9
    Abstract: In porous media, the nonwetting phase is trapped on water saturation due to capillary forces acting in a heterogeneous porous structure. Within the capillary fringe, the gas phase is trapped and released along with the fluctuation of the water table, creating a highly active zone for biological transformations and mass transport. We conducted column experiments to observe and quantify the magnitude and structure of the trapped gas phase at the pore scale using computed microtomography. Different grain size distributions of glass beads were used to study the effect of the pore structure on trapping at various capillary numbers. Viscous forces were found to have negligible impact on phase trapping compared with capillary and buoyancy forces. Residual gas saturations ranged from 0.5 to 10%, while residual saturation increased with decreasing grain size. The gas phase was trapped by snap‐off in single pores but also in pore clusters, while this single‐pore trapping was dominant for grains larger than 1 mm in diameter. Gas surface area was found to increase linearly with increasing gas volume and with decreasing grain size.
    Type of Medium: Online Resource
    ISSN: 1539-1663 , 1539-1663
    Language: English
    Publisher: Wiley
    Publication Date: 2015
    detail.hit.zdb_id: 2088189-7
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  • 6
    In: Soil Science Society of America Journal, Wiley, Vol. 77, No. 2 ( 2013-03), p. 403-411
    Type of Medium: Online Resource
    ISSN: 0361-5995
    RVK:
    Language: English
    Publisher: Wiley
    Publication Date: 2013
    detail.hit.zdb_id: 241415-6
    detail.hit.zdb_id: 2239747-4
    detail.hit.zdb_id: 196788-5
    detail.hit.zdb_id: 1481691-X
    SSG: 13
    SSG: 21
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  • 7
    Online Resource
    Online Resource
    Wiley ; 2013
    In:  Vadose Zone Journal Vol. 12, No. 4 ( 2013-11), p. 1-17
    In: Vadose Zone Journal, Wiley, Vol. 12, No. 4 ( 2013-11), p. 1-17
    Abstract: The hydraulic behavior of soil is determined by its hydraulic properties and their variability in space. In agricultural soils, this heterogeneity may stem from tillage or may have natural origin. The root distribution of plants will adapt to some extent to this soil heterogeneity. However, the combined impact of soil heterogeneity and root water uptake (RWU) on long‐term soil water budgets has not received much attention. Numerical experiments helped identify how soil heterogeneity affects plant transpiration, soil evaporation, and groundwater recharge. Two‐dimensional virtual soils with hierarchical heterogeneity, both natural and tillage induced, served as a basis for modeling soil water dynamics for a 10‐yr climate record from two weather stations in Germany that vastly differ in annual precipitation. The complex interactions between soil and vegetation were explored by (i) comparing different RWU strategies (depth‐, structure‐, and time‐dependent root profiles), (ii) land use types (perennial grass and annual winter crops), (iii) a combination of textures (silt above sand and sand above loam), and (iv) RWU with or without a compensation mechanism. The simulations were repeated with one‐dimensional, effective representations of these virtual soils. In the framework of hydropedology, this study shed some light on the interaction between plants and pedological features and its impact on the macroscopic soil water budget. We demonstrated that land use has a major impact on the annual water balance through the partitioning of evapotranspiration into bare soil evaporation and plant transpiration. Compensational RWU becomes important for the annual water balance when the root zone comprises contrasting materials with respect to water holding capacity. Soil heterogeneity has in fact a minor impact on long‐term soil water budgets. As a consequence, the relative contribution of plant transpiration, soil evaporation, and groundwater recharge to the total soil water loss was well reproduced by simulations in one‐dimensional effective soil profiles. This advocates the application of one‐dimensional soil–atmosphere–vegetation transfer (SVAT) models at larger scales. These findings only hold for assumptions made in our numerical simulations including flat area without lateral flow and no macropore flow.
    Type of Medium: Online Resource
    ISSN: 1539-1663 , 1539-1663
    Language: English
    Publisher: Wiley
    Publication Date: 2013
    detail.hit.zdb_id: 2088189-7
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  • 8
    Online Resource
    Online Resource
    Wiley ; 2018
    In:  Vadose Zone Journal Vol. 17, No. 1 ( 2018-01), p. 1-7
    In: Vadose Zone Journal, Wiley, Vol. 17, No. 1 ( 2018-01), p. 1-7
    Abstract: Water can be quantitatively detected in soil with X‐ray radiography. We developed an easy calibration method to correct for beam hardening. We also eliminated drift of X‐ray attenuation values due to detector latency. X‐ray radiography is a suitable approach to study water dynamics in undisturbed soil. However, beam hardening impairs the deduction of soil moisture changes from X‐ray attenuation, especially when studying infiltration of water into cylindrical soil columns. We developed a calibration protocol to correct for beam hardening effects that enables the quantitative determination of changing average water content in two‐dimensional projections. The method works for a broad range of materials and is easy to implement. Moreover, we studied the drift of X‐ray attenuation values due to the detector latency and eliminated its contribution to the quantitative analysis. Finally we could visualize the dynamics of infiltrating water into undisturbed cylindrical soil samples.
    Type of Medium: Online Resource
    ISSN: 1539-1663 , 1539-1663
    Language: English
    Publisher: Wiley
    Publication Date: 2018
    detail.hit.zdb_id: 2088189-7
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  • 9
    Online Resource
    Online Resource
    Wiley ; 2023
    In:  Vadose Zone Journal Vol. 22, No. 2 ( 2023-03)
    In: Vadose Zone Journal, Wiley, Vol. 22, No. 2 ( 2023-03)
    Abstract: Soils are rarely in hydraulic equilibrium. We show consequences for their effective hydraulic conductivity. We present a physically based concept how to better describe the unsaturated conductivity function. The new approach describes pressure overshoot across fronts and the emergence of preferential during infiltration.
    Type of Medium: Online Resource
    ISSN: 1539-1663 , 1539-1663
    URL: Issue
    Language: English
    Publisher: Wiley
    Publication Date: 2023
    detail.hit.zdb_id: 2088189-7
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  • 10
    In: Geoarchaeology, Wiley, Vol. 30, No. 4 ( 2015-07), p. 369-378
    Abstract: Roman cisterns served as rainwater storage devices for centuries and are densely distributed in parts of northern Jordan. A major earthquake hit the region ca . A.D. 750 and in a short time many settlements were abandoned. As a consequence, most cisterns were not maintained, and they filled with sediments that today provide a postabandonment depositional record. In two field surveys, we mapped the locations of more than 100 cisterns in the Wadi Al‐Arab basin and selected two for detailed stratigraphic analysis that included 14 C and optically stimulated luminescence dating. Catchment basin area for each cistern was determined by differential GPS. Both cisterns filled with sediments after the great earthquake and consequent abandonment of the region. Calculated sediment volumes are translated to long‐term average sediment export rates of 2.6–6.6 t ha −1 a −1 , which are comparable to erosion and sediment yield rates from other studies within the Mediterranean region. Our pilot study suggests that this approach can be applied elsewhere to calculate long‐term sediment export rates on hill slopes containing relict cisterns.
    Type of Medium: Online Resource
    ISSN: 0883-6353 , 1520-6548
    URL: Issue
    Language: English
    Publisher: Wiley
    Publication Date: 2015
    detail.hit.zdb_id: 1479950-9
    SSG: 6,14
    SSG: 13
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