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  • 1
    Language: English
    In: Geoderma, 2004, Vol.120(1), pp.137-153
    Description: In this study, we exploit dye patterns to identify flow types in macroporous soils as a step forward from using dye patterns simply as qualitative pictures that illustrate preferential flow. Dye tracer experiments at different irrigation rates and initial soil moisture conditions were carried out on three hillslope sites. Several vertical and horizontal soil sections were prepared after each experiment to analyze the patterns of the dye tracer Brilliant Blue FCF. Photographs of the soil sections were processed by image analysis to discriminate between stained and unstained areas and to classify stained areas into three classes of dye concentration. The images of the vertical sections were first analyzed according to conventional approaches (e.g., dye coverage). Then, a new approach was developed using the extent and distribution of the stained objects to classify flow into five types, two of these flow types occur only in the soil matrix, and three of them are related to the degrees of water flow between macropores and soil matrix (interaction). From horizontal sections, the macropore distribution was classified and, in combination with the dye pattern, the interaction quantified based on statistical description of the spatial relationship between macropores and stained areas. Categorized flow type profiles showed a logical sequence in each of our experiments, and we think the concepts will have broad application in soil science and infiltration research to compare the infiltration regimes of soils.
    Keywords: Dye Pattern ; Unsaturated Zone ; Image Analysis ; Flow Types ; Macropore Flow ; Preferential Flow ; Agriculture
    ISSN: 0016-7061
    E-ISSN: 1872-6259
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  • 2
    Language: English
    In: Journal of Hydrology, 2010, Vol.393(1), pp.1-2
    Description: Includes references ; p. 1-2.
    Keywords: Geography
    ISSN: 0022-1694
    E-ISSN: 1879-2707
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  • 3
    Language: English
    In: Journal of Hydrology, 2001, Vol.247(1), pp.100-115
    Description: Irrigation experiments using the tracers Brilliant Blue (BB) and Bromide (Br) were conducted on three plots of 1.4 x 1.4 m(2) (plot scale) and a field scale subsurface drained test site (900 m(2)) to clarify mechanisms causing rapid transport of surface applied Isoproturon (IPU) during preferential flow events. One of the small plots (site 10) and the field scale test site are located on the same field. One day after irrigation of the plot scale sites the Br and IPU concentration in two vertical soil profiles as well as the macroporousity on separate profiles and hydraulic properties of single macropores were determined. During irrigation of the field scale test site discharge, soil moisture as well as the concentration of IPU and Br in the drainage outlet were measured. Preferential flow in deep penetrating earthworm burrows caused a fast breakthrough of IPU and Br into the tile drain (1.2 m depth) at the field scale site as well as leaching of IPU into the subsoil (〉0.8 m) at site 10. The results suggest a hierarchy of preconditions for the occurrence of preferential flow events of which a sufficient number of deep penetrating macropores interconnected to the soil surface seems to be the most important one. Moreover there is evidence that facilitated transport of IPU attached to mobile soil particles occurred during the preferential flow events at the field scale site and site 10. The susceptibility for preferential flow as well as the susceptibility for facilitated transport appear to be intrinsic properties of the investigated soil. ; p. 100-115.
    Keywords: Pesticide ; Facilitated Transport ; Preferential Flow ; Subsurface Drainage ; Experiments ; Geography
    ISSN: 0022-1694
    E-ISSN: 1879-2707
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  • 4
    Language: English
    In: Vadose Zone Journal, 2010, Vol.9(3), p.747
    Description: Silvicultural operations increasingly aim to achieve desired water-related ecological services of forests and forest soils. Therefore, the effects of forest stand density, site, and soil depth on the water flow types were studied by conducting dye tracer experiments in two montane beech (Fagus sylvatica L.) forests located in the Western Carpathian Volcanic Range, Central Slovakia. Prevalent flow types were identified under usual weather conditions. Brilliant Blue FCF dye tracer was periodically applied in powder form on 1-m2 plots in forest stands with natural and reduced stand densities, as well as in clear-cuts. When cumulative precipitation reached approximately 100 mm, soil pits were excavated. The dye patterns on the exposed profiles were photographed, and dye coverage, relative dye concentration, and stain widths were determined at various soil depths using image analysis. These patterns were used to discriminate two flow types. Continuous vertical dye plumes were interpreted as an indicator of surface-controlled flow type, which includes heterogeneous infiltration and macropore flow. The matrix-controlled flow type includes both homogeneous and heterogeneous matrix flow, as well as fingering. The log-linear analysis revealed that forest stand density and soil depth were significantly related to the soil water flow type. Preferential flow resulted from heterogeneous infiltration and fingering in the clear-cuts, from heterogeneous infiltration in the natural stands, and from macropore flow in the shelterwood stands. Distinct humus forms and skeleton fraction played a crucial role for various flow patterns observed in these beech stands. ; Includes references ; p. 747-756.
    Keywords: Forest Soils ; Stand Density ; Environmental Factors ; Soil Profiles ; Ecosystem Services ; Soil Pore System ; Fagus Sylvatica ; Forest Trees ; Logging ; Preferential Flow ; Soil Water Movement ; Spatial Variation ; Macropore Flow ; Spatial Distribution ; Soil Depth ; Humus ; Labeling Techniques ; Montane Forests ; Precipitation ; Temperate Forests ; Clearcutting ; Infiltration (Hydrology) ; Image Analysis ; Matrix-Controlled Flow ; Fingering (Hydrology) ; Andic Soils;
    ISSN: Vadose Zone Journal
    E-ISSN: 1539-1663
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  • 5
    Language: English
    In: Journal of Hydrology, 2005, Vol.309(1), pp.66-84
    Description: In spring, snowmelt releases huge quantities of meltwater, affecting the hydrology of Alpine areas. Seasonal soil frost influences these water fluxes by locally decreasing the infiltration capacity of the soil, resulting in an increased amount of surface runoff. The main goal of this study was to investigate the spatial variability of the seasonal frost depth and to quantify by how much this seasonal soil frost affects the snowmelt discharge. For this purpose, an extensive field study was run for two winter seasons (2000/2001 and 2001/2002) at Gd St Bernard (2470 m) and Hannigalp (2090 m) in the southern Swiss Alps. The different components of the water balance (lateral runoff, deep percolation, liquid soil water content) were measured on delimited plots of 5 m . The two winters investigated had opposing weather and soil frost conditions: in the first winter a thick snowpack prevented the formation of soil frost, whereas in the second winter little snow fell until January, which produced a deep and persistent soil frost. We classified the snowmelt events into several classes (mid-winter, late winter, spring and post-spring) and analysed the significance of the different water flow components for each melt situation. While 90–100% of melt water infiltrated into the ground during the first winter, 25–35% of melt water ran off laterally in the second, mainly during late winter and spring snowmelt events. In that second winter, the soil infiltration capacity was primarily reduced by the presence of a basal ice sheet after mid-winter melt events.
    Keywords: Snowmelt ; Runoff ; Seasonal Soil Frost ; Water Balance ; Alps ; Geography
    ISSN: 0022-1694
    E-ISSN: 1879-2707
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  • 6
    Language: English
    In: Forest Ecology and Management, 1998, Vol.101(1), pp.177-185
    Description: Two small experimental headwater catchments (approx. 1500 m 2 ) were set up in an alpine spruce forest in the Alptal valley (central Switzerland). They are located at an altitude of 1200 m and receive an average of 2300 mm precipitation a year. The site is moderately impacted by atmospheric nitrogen deposition (12 kg N ha −1 yr −1 bulk deposition of inorganic N). Two different gley soils occur as patches atop a Flysch substratum. The spatial heterogeneity of the soil is related with both the microtopography of the site and the vegetation. The catchments were made by digging 80-cm deep trenches into the shallow gleyic soils. Because of the low permeability of the clay-rich subsoil, these trenches collect the lateral water flow generated in the plots. The catchments were equipped with gauging stations (V-notch weirs) and automatic runoff-proportional water samplers. Meteorological parameters, deposition, water and solute discharge were monitored during one year. A correct water balance was obtained from the experimental catchments. The leaching of inorganic nitrogen was estimated to be 4 kg N ha −1 yr −1 , mainly as nitrate. It is, however, not clear if this nitrate is leached because the ecosystem is nitrogen saturated (N in surplus of the maximal ecosystem retention). Quick preferential water flow occurs through the soil, and this may prevent nitrate from rain or snowmelt to be removed by the soil matrix before entering the water runoff pathways. Both mini-catchments showed similar biogeochemical cycles, especially for nitrogen. The time series obtained will be used as reference period for a paired-catchment experiment simulating an increased nitrogen (ammonium nitrate) deposition.
    Keywords: Nitrogen Cycling ; Nitrogen Deposition ; Forest Ecosystem ; Headwater Catchment ; Nitrex Project ; Forestry ; Biology
    ISSN: 0378-1127
    E-ISSN: 1872-7042
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  • 7
    Language: English
    In: Journal of Plant Nutrition and Soil Science, April 2009, Vol.172(2), pp.180-185
    Description: Time domain reflectometry (TDR) trace analysis aims at extracting the water content profile along TDR probes. This can be done by applying a TDR forward solver inversely. Thus, TDR‐trace inversion is basically an optimization problem. As in any optimization procedure, it is worthwhile to include as much information as possible about the problem to be solved. In this study, we discuss the feasibility to use the apparent electrical conductivity as constraint for the TDR inversion. The resistors‐in‐parallel circuit can be used to integrate a multislice soil model to obtain the apparent electrical conductivity. We apply additionally Archie's law to link the water content of a particular slice with its electrical conductivity. We compare the results from this approach with measured TDR traces and show that the problem is solved exactly. Finally, we address the thin‐layer issue because thin layers with a high permittivity contrast result in a delay of the run time of an electromagnetic pulse. We test numerically whether a similar behavior can be observed for a thin layered electrical conductivity profile. Our results show that the thickness of the soil layer with respect to electrical conductivity has no effect on the apparent electrical conductivity. We conclude that the apparent electrical conductivity is appropriate as boundary condition in TDR inversion as long as a procedure is known to convert the water content of a slice to its electrical conductivity
    Keywords: Tdr ; Electrical Conductivity ; Water Content ; Transmission Line
    ISSN: 1436-8730
    E-ISSN: 1522-2624
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  • 8
    Language: English
    In: Arctic, Antarctic, and Alpine Research, 01 February 2004, Vol.36(1), pp.128-135
    Description: Snowmelt infiltration into alpine soils can be severely reduced and even impeded by soil frost. In order to learn more about the true nature of infiltration pathways into alpine soils, dye tracer experiments were set up at 2 locations in southern Switzerland: at Hannigalp (2100 m) and at Gd St Bernard. Over the course of two winters (2000-2001 and 2001-2002) we excavated vertical soil profiles during snowmelt to examine the distribution of a dye tracer (Brilliant Blue FCF) that had been applied on the surface of a 7-m 2 plot at the beginning of the winter. Soil conditions varied between the winters, with the soils remaining unfrozen during the first and a significant frozen layer forming during the second. With this method the dominant infiltration processes at these 2 sites were identified. During the first winter the water infiltration at Hannigalp showed a pronounced preferential behavior, whereas at Gd St Bernard we found a more homogeneous front-like infiltration. During the second winter the impeding impact of the frozen soil was clearly seen at the Hannigalp site-however, only in the first stage of the snowmelt. More decisive for the formation of lateral surface runoff was the buildup of an ice layer on the soil surface due to melting and refreezing. Cold-chamber experiments, in which intact soil columns were irrigated with a dye tracer and a fluorescent tracer solution, confirmed our in situ observations with regard to heterogeneity and soil frost effect on the infiltration pattern. Our study showed that both tracers can be applied to frozen soil in the laboratory, whereas at the remote alpine locations only the dye tracer method was applicable.
    Keywords: Geography ; Ecology
    ISSN: 1523-0430
    E-ISSN: 1938-4246
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  • 9
    Language: English
    In: Soil Science Society of America Journal, 2002, Vol.66(3), p.774
    Description: To identify soil properties that control transport of adsorbing solutes in natural soil, we carried out leaching experiments in undisturbed soil cores taken from three soil layers of a Stagni-Humic Cambisol. Breakthrough curves (BTCs) of [Cl.sup.-] and two adsorbing fluorescent dye tracers, brilliant sulfaflavine (BF; 1H-Benz(de)isoquinoline-5-sulfonic acid, 2,3-dihydro-6-amino-1,3-dioxo-2-(p-tolyl)-, monosodium salt) and sulforhodamine B (SB; xanthylium, 3,6-bis(diethylamino)-9-(2,4-disulfophenyl)-, inner salt, sodium salt), were measured. Three cores were scanned with x-rays to determine the three-dimensional (3-D) structure of large pores. After the leaching experiment, soil cores were horizontally sliced and dye concentration distributions on cross sections were derived from fluorescence signal images. Transport was investigated using BTCs and concentration maps, adsorption isotherms, and predictions by three different transport models: convection dispersion model (CDM), stream tube model (STM) and physical nonequilibrium model (PNEM). The dense network of large pores in the two upper soil layers induced a uniform lateral spreading of dyes and the CDM described the transport fairly well. In cores from the deeper layer, the large pore network was considerably less dense and dye patterns followed closely the few large pores without lateral mixing indicating preferential flow and explaining the fast dye breakthrough. Predictions by the STM revealed that the fast SB breakthrough could not be explained solely by preferential flow. Fitting the PNEM to breakthrough data and the low total dye concentration in the preferential flow region suggested a small sorption capacity of the preferential flow region for SB. Therefore, preferential leaching of dyes resulted from small-scale variations in physical and chemical soil properties.
    Keywords: Sediment Transport -- Measurement ; Tracers (Chemistry) -- Usage ; Soil Chemistry -- Research ; Soil Research -- Methods;
    ISSN: Soil Science Society of America Journal
    ISSN: 03615995
    E-ISSN: 1435-0661
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  • 10
    Language: English
    In: Vadose Zone Journal, 2003, Vol.2(3), p.338
    Description: Dye tracer experiments have often been used to study the prevailing flow regime, such as in investigating the role and extent of preferential flow of water. Flow patterns in two-dimensional profiles provide qualitative information on the infiltration regime but are difficult to analyze and compare quantitatively. The scope of this study was to develop a quantitative method to analyze the spatial distribution of the stained areas in vertical profiles, to identify differing transport mechanisms on the basis of the pattern information, and to analyze how the discriminated patterns correspond with soil properties and structure. Dye tracer infiltration experiments were performed on 25 plots at eight sites. The spatial distribution of the stained areas in vertical profiles was analyzed and compared using digital image processing. We first split the flow patterns into similarly stained horizontal layers based on the width distribution of stained areas. All of these layers identified in the flow patterns of all 25 plots were then partitioned into groups of layers with similar patterns by hierarchical clustering. The sequence of layers found in the pattern was finally interpreted with respect to transport mechanisms and qualitatively compared with the sequence of morphological layers observed in the soil profiles. The obtained classification reliably distinguished between zones of homogeneous infiltration and zones of preferential flow, but also between zones of narrow stained structures and zones of lateral spreading (e.g., sand or gravel lenses). Dye coverage and mean width of stained structures were the most indicative factors for the different clusters. We often found an agreement between the sequences of layers found in the flow patterns and the soil horizons. However, in all profiles we observed layers in the flow patterns that did not correspond to textural and structural layers observed in the filed. It seems that knowing the pedological horizons is important but not sufficient to understand the observed flow patterns. Since the flow pattern in a given layer always depends on the overlying soil layers, similarly textured soil layers do not necessarily exhibit equal patterns. However, soil layers with a given textural sequence (e.g., fine-course-fine) are reflected by typical flow patterns. ; Includes references
    Keywords: Soil Profiles ; Soil Water Movement ; Infiltration (Hydrology) ; Spatial Variation ; Dyes;
    ISSN: Vadose Zone Journal
    E-ISSN: 1539-1663
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