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  • 1
    Language: English
    In: Geoderma, 01 June 2016, Vol.271, pp.50-62
    Description: Higher solute input due to stemflow infiltration causes enhanced soil acidification near the tree base. Infiltration-driven alteration of chemical soil properties like pH, and carbon to nitrogen ratio (C/N) and particle surface properties like oxygen to carbon ratio (O/C), may also affect soil wettability with a trend to increased soil water repellency (SWR) with increased acidity. Our study provides a link between chemical soil quality and physical behavior with respect to soil water infiltration and SWR, respectively in a beech forest soil. The spatial variability of soil properties was analyzed within a grid (Δ = 1 m, 5 m × 8 m = 40 m ) and, to reveal direct effects of stemflow influence on soil properties, we sampled along a tree row (Δz = 0.8 m, l = 46.60 m) with varying sampling points to tree distances. All samples were taken in a beech ( L.) forest Bws/Bw-horizon in 0.1–0.2 m depth (dystric cambisol). Analysis of spatial variability by standard statistics and geostatistical methods revealed no substantial differences between grid and transect samples for pH and sulfate, Al, and Fe (aluminum and iron oxalic acid extractable) concentration and SWR in terms of contact angle (CA, sessile drop method) measured for bulk soil samples. According to standard statistics, the total variance of chemical soil properties and SWR was independent of stemflow infiltration pattern. Results of spectral variance analysis showed that the spatial variability of acidification (pH, Al content) as well as SWR was strongly affected by the pattern of patches with and without stemflow infiltration or the distribution of beech trees, respectively. In a more or less regularly planted beech forest this caused a cyclic variation of soil acidification and SWR with a strong trend to increased SWR (CA ranges 17°–72°) with increased soil acidity. Specific chemical surface properties, analyzed via X-ray photoelectron spectroscopy, like O/C ratio ( = 0.782) and the amount of nonpolar C species ( = 0.768) as well as surface Al concentration ( = 0.867) clearly showed a strong relation to CAs. Hence, SWR was strongly affected by stemflow infiltration patterns into soil. For C/N, sulfate, and Fe content no significant relations to SWR or soil acidity were found.
    Keywords: Soil Water Repellency ; Geostatistics ; Spectral Variance Analysis ; X-Ray Photoelectron Spectroscopy ; Element Composition ; Agriculture
    ISSN: 0016-7061
    E-ISSN: 1872-6259
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  • 2
    Language: English
    In: Journal of Hydrology and Hydromechanics, 01 June 2016, Vol.64(2), pp.100-110
    Description: Most recent studies on soil water repellency (WR) were limited to the humous topsoil or to shallow subsoil layers slightly below the main root zone to approximately 0.5 m depth. Hence, the main objective of the present study was to investigate the wettability pattern of a forest soil including the deeper subsoil. The selected site was a 100 years old beech forest on a well-drained sandy Cambisol in northern Germany which showed moderate to partly extended acidification. Results obtained from three sampling transects (3 m length, 2 m depth; sampling grid 8 × 8 samples per transect; minimum distance of sampling locations to nearest tree about 0.5 m) show that contact angles (CA) were always in the subcritical WR range (0° 〈 CA 〈 90°). Significant impact of the tree distance on WR was not observed for any of the transects. A prominent feature of two transects was the minimum WR level (CA 〈 10°) for samples with soil organic carbon (SOC) contents around 0.25–0.4%. For the topsoils it was observed that CA increased with SOC content from that minimum to a maximum CA of 60–75° for transects 1 and 2 with mean pH values 〈 3.5. For transect 3 with slightly higher average pH close to 4.0, average CA of samples were always 〈 10° and showed no trend to increase with increasing SOC content or other soil parameters like N content or C/N ratio. Subsoil samples, however, behave differently with respect to SOC: for these samples, generally low in SOC, the CA increase with decreasing SOC occurred at all transects for approximately 50% of the samples but did not show any clear tendencies with respect to further parameters like texture, pH or N content. We conclude that the SOC content is the most prominent parameter determining wettability, either positively correlated with WR for topsoils or negatively correlated for subsoil samples very low in SOC. We finally conclude for moderately acid beech forest stands that emerging WR starts in the A horizon after reaching a pH lower than 3.5, whereas subsoil WR might appear already at higher pH values. Even SOC contents of ~0.01–0.02% turned out to be very effective in increasing the CA up to 70°, which points out clearly the importance of small amounts of soil organic matter in affecting subsoil wettability. With respect to site hydrology we conclude that ongoing acidification as well as predicted higher frequencies of extended droughts due to climate change will promote the occurrence of WR with corresponding implications for site and catchment hydrology.
    Keywords: Beech Forest ; Soil Organic Carbon ; Subsoil ; Water Repellency ; Geography
    E-ISSN: 0042-790X
    E-ISSN: 13384333
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  • 3
    Language: English
    In: Catena, November 2017, Vol.158, pp.46-54
    Description: Aggregate stability (AS) is an important property controlling erodibility of volcanic ash soils and is known to be strongly affected by fine-grained iron (Fe) and aluminum (Al) minerals. Assuming that frequency dependence of magnetic susceptibility (MS) is related to the amount of fine-grained Fe minerals and considering that formation of fine-grained Fe and Al minerals is closely coupled in volcanic ash soils, we hypothesized that the measurement of MS can be used to evaluate AS of these soils. To verify this, we investigated volcanic ash soils along a 120-km transect in southern Chile, reaching from the Andean Southern Volcanic Zone (SVZ) to the Pacific coastal range. Stability of 1-cm macroaggregates from topsoil (0–5 cm) and subsoil (20–25 cm) was determined by wet-sieving, combining long-term water immersion and subsequent ultrasonic treatment. MS was measured at 465 and 4650 kHz to calculate its frequency dependence. We found an increasing amount of organic matter, fine-grained Fe and Al minerals, and clay and decreasing bulk density with increasing distance from the SVZ, indicating progressing soil development along the transect. Likewise, AS increased with increasing distance from the SVZ and was found to be controlled primarily by soil organic matter and fine-grained Fe and Al minerals. While MS itself showed only slight variation, its frequency dependence continuously increased with increasing distance from the SVZ, indicating an increasing fraction of fine-grained ferrimagnetic particles. Accordingly, frequency dependence of MS was found to be linearly related to the amount of fine-grained Fe minerals as quantified by dithionite extraction, and moreover, due to the close linear relationship between fine-grained Fe and Al phases, it revealed to be suitable for estimating the total amount of both fine-grained Fe and Al minerals. Analysis of underlying material (60–65 cm) indicated that the increase in frequency dependence of MS with increasing distance from the SVZ was caused by fine-grained ferrimagnetic particles of pedogenic and lithogenic origin. Although overall organic matter content turned out to be more closely related to the stability of the investigated aggregates, we conclude that frequency dependence of MS can be used as an easily obtainable proxy for assessing the contribution of fine-grained Fe and Al minerals to AS.
    Keywords: Andosols ; Iron Oxides ; Magnetic Susceptibility ; Mineral Magnetism ; Pedogenesis ; Soil Aggregate Stability ; Sciences (General) ; Geography ; Geology
    ISSN: 0341-8162
    E-ISSN: 1872-6887
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  • 4
    In: Ecohydrology, September 2018, Vol.11(6), pp.n/a-n/a
    Description: 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.
    Keywords: Drift Spectroscopy ; Extracellular Enzyme Activity ; Flow Cell ; Soil Water Repellency ; Transport Processes ; Undisturbed Soil ; X‐Ray Radiography
    ISSN: 1936-0584
    E-ISSN: 1936-0592
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  • 5
    Language: English
    In: 2015
    Keywords: Forest Soils ; Soil Ph ; Oxygen ; Soil Heterogeneity ; Contact Angle ; Iron ; Soil Sampling ; B Horizons ; Carbon ; Aluminum ; Analysis Of Variance ; Element Composition ; Cambisols ; Soil Water Repellency ; Infiltration (Hydrology) ; Forests ; X-Ray Photoelectron Spectroscopy ; Oxalic Acid ; Geostatistics ; Sulfates ; Solutes ; Variance ; Fagus Sylvatica ; Geostatistics ; Stemflow ; Acidity ; Water Repellent Soils ; Soil Water ; Soil Acidification ; Carbon Nitrogen Ratio ; Soil Quality ; Wettability ; Trees ; Acidification ; Spectral Variance Analysis
    Source: AGRIS (Food and Agriculture Organization of the United Nations)
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  • 6
    Language: English
    Description: Most recent studies on soil water repellency (WR) were limited to the humous topsoil or to shallow subsoil layers slightly below the main root zone to approximately 0.5 m depth. Hence, the main objective of the present study was to investigate the wettability pattern of a forest soil including the deeper subsoil. The selected site was a 100 years old beech forest on a well-drained sandy Cambisol in northern Germany which showed moderate to partly extended acidification. Results obtained from three sampling transects (3 m length, 2 m depth; sampling grid 8 × 8 samples per transect; minimum distance of sampling locations to nearest tree about 0.5 m) show that contact angles (CA) were always in the subcritical WR range (0° 〈 CA 〈 90°). Significant impact of the tree distance on WR was not observed for any of the transects. A prominent feature of two transects was the minimum WR level (CA 〈 10°) for samples with soil organic carbon (SOC) contents around 0.25–0.4%. For the topsoils it was observed that CA increased with SOC content from that minimum to a maximum CA of 60–75° for transects 1 and 2 with mean pH values 〈 3.5. For transect 3...
    Keywords: Beech Forest ; Soil Organic Carbon ; Subsoil ; Water Repellency ; Dewey Decimal Classification::500 | Naturwissenschaften::550 | Geowissenschaften
    Source: DataCite
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