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  • 1
    Language: English
    In: Soil Science Society of America Journal, March-April, 2005, Vol.69(2), p.343(4)
    Description: The need exists for a measurement technique to accurately determine the depth of surface runoff on natural soil surfaces. The objective of this note was to determine the sensitivity to the immersion depth of commercially available frequency-domain probes. Within the range of 0 to 25 mm, measurement accuracies better than 0.5 mm were reached. Interestingly, soiling of the rods or droplets did not influence the results significantly. The influence of the electrical conductivity of the water or internal characteristics of different probes did not lead to a bias of more than 1 mm. A field test with grid-like mounted frequency-domain probes showed a stable output signal and a high sensitivity to hydrograph changes. We concluded that frequency-domain probes were well suited for tracking shallow depths of surface runoff in field studies and allow high spatial and time resolution. They provide higher accuracy than alternative systems in the water-level range 〈5 mm. However, when the measurement precision must be higher than 0.5 mm, an individual calibration of the probes is necessary as well as a correction for salinity.
    Keywords: Soil Chemistry
    ISSN: 0361-5995
    E-ISSN: 14350661
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  • 2
    Language: English
    In: Forest Ecology and Management, 15 November 2015, Vol.356, pp.136-143
    Description: Phosphorus is an essential yet scarce macronutrient, and as such forest nutrition often relies on cycling of P between biomass and soils through litterfall and roots. For technical and soil protection reasons, modern harvesting systems create thick brash mats on skid trails by depositing residues, thus concentrating P there. What portion of this redistributed P is immobilized, lost, or recycled could be significant to forest nutrition and management. However, open questions exist regarding the quantity and fate of P deposited on skid trials. The aim of this study was to determine how much P is redistributed to skid trails and what happens to that P. We modeled the amount of P deposited on a skid trail during a whole-tree thinning of an Mill. stand, and quantified P stocks in the forest floor and mineral soil five years after the operation. An estimated 60% of harvested P from the encatchment was deposited on the skid trail. Five years after the harvest, forest floor P stocks in the skid trail dropped from an extrapolated 8.9 to 4.4 g m . The difference of 4.5 g m of P was not evident in mineral soil stocks, and loss through runoff or leaching would be minimal. With the greatest concentration of roots in the forest floor on the middle of the skid trail, mineralization and uptake of the missing P was the most likely explanation. This suggests that accumulated P on skid trails can be recycled through uptake by trees. Further testing in other stands and on which vegetation takes up accumulated P is still needed.
    Keywords: Nutrient Cycling ; Plant Uptake ; Whole-Tree Harvesting ; Brash Mats ; Allometric Modeling ; Forestry ; Biology
    ISSN: 0378-1127
    E-ISSN: 1872-7042
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  • 3
    Language: English
    In: Remote Sensing, 01 August 2010, Vol.2(8), pp.1941-1961
    Description: Topography is a crucial surface characteristic in soil erosion modeling. Soil erosion studies use a digital elevation model (DEM) to derive the topographical characteristics of a study area. Majority of the times, a DEM is incorporated into erosion models as a given parameter and it is not tested as extensively as are the parameters related to soil, land-use and climate. This study compares erosion relevant topographical parameters—elevation, slope, aspect, LS factor—derived from 3 DEMs at original and 20 m interpolated resolution with field measurements for a 13 km2 watershed located in the Indian Lesser Himalaya. The DEMs are: a TOPO DEM generated from digitized contour lines on a 1:50,000 topographical map; a Shuttle Radar Topography Mission (SRTM) DEM at 90-m resolution; and an Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) DEM at 15-m resolution. Significant differences across the DEMs were observed for all the parameters. The highest resolution ASTER DEM was found to be the poorest of all the tested DEMs as the topographical parameters derived from it differed significantly from those derived from other DEMs and field measurements. TOPO DEM, which is, theoretically more detailed, produced similar results to the coarser SRTM DEM, but failed to produce an improved representation of the watershed topography. Comparison with field measurements and mixed regression modeling proved SRTM DEM to be the most reliable among the tested DEMs for the studied watershed.
    Keywords: Dems ; Aster ; Srtm ; Topographical Parameters ; Soil Erosion Modeling ; Geography
    ISSN: 2072-4292
    E-ISSN: 2072-4292
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  • 4
    Language: English
    In: Plant and Soil, 1998, Vol.199(1), pp.167-176
    Description: Biologic activity is one of the main factors controlling the floating equilibrium between loosening and compacting forces in humic forest soils. Therefore it can be expected that both acid deposition and compensatory liming indirectly influence the soil structure and soil aeration. To measure macro-pore structure, CO 2 concentrations in the soil air, and respiration rates we used naturally structured soil cores from the “Höglwald” forest-ecosystem research plots with experimental acid deposition and liming, but standardized water supply. Results are integrated in an one-dimensional soil-aeration model. Compared to the control plot, in the top soil of the limed plot both gaseous diffusion coefficients and respiration rates are increased. Since the CO 2 concentration in the soil air is decreased at the same time, the soil aeration status of the whole profile can be regarded as stabilized. On the acid irrigated plot, gas-diffusion coefficients are not significantly changed with regard to the control. In the top-mineral soil, in contrast to the working hypothesis, they are tendencially increased. In the case of liming, a stimulation of biologic activity and a positive feedback on the soil structure could be attributed to an increased earth-worm activity due in turn to decreased acidity and enhanced feeding conditions. The acid irrigation leads to increased Al 3+ activity, which can stabilize the soil structure.
    Keywords: acidification ; aeration ; gas concentration gradients ; liming ; soil respiration ; soil structure
    ISSN: 0032-079X
    E-ISSN: 1573-5036
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  • 5
    Language: English
    In: Communications in agricultural and applied biological sciences, 2012, Vol.77(1), pp.139-43
    Keywords: Ecosystem ; Oxygen Consumption ; Soil Microbiology ; Trees -- Physiology
    ISSN: 1379-1176
    Source: MEDLINE/PubMed (U.S. National Library of Medicine)
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  • 6
    Language: English
    In: Forests, 01 September 2017, Vol.8(10), p.358
    Description: Forest harvesting removes and redistributes nutrients through felling and forwarding. Substantial quantities of nutrients can accumulate in brash mats on permanent skid trails, but their availability and uptake after multiple thinnings on soils susceptible to leaching are unknown. In this study, we modeled the deposition of base cations and phosphorus on a permanent skid trail after five thinnings of a Picea abies (L.) Karst. stand, and measured the resulting nutrient stocks in both the forest floor and mineral soil. An estimated 35%, 44%, 41%, and 61% of harvested Ca, K, Mg, and P, respectively, were redistributed to the skid trail. Of those deposited stocks, 32–65% of nutrients remained in decomposed brash material on the skid trail. Mineral soil stocks for Ca, K, and P were significantly higher in the skid trail than in the stand, which included minor increases in bioavailable pools. Skid trail root densities were not lower than the stand while bulk densities were only partially higher. Both would not limit nutrient uptake. There were no significant relations between needle nutrient concentrations and distance to the skid trail. Altogether, these results indicate that nutrient uptake from the skid trail was minimal despite their accumulation, chemical availability, and physical accessibility. This suggests that other factors such as liming and frequent thinning disturbances can repress uptake of available nutrients on skid trails.
    Keywords: Soil Management ; Picea Abies ; Brash Mats ; Needle Nutrition ; Whole-Tree Harvesting ; Liming ; Forestry
    E-ISSN: 1999-4907
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  • 7
    Language: English
    In: Agricultural and Forest Meteorology, May 15, 2014, Vol.188, p.45(13)
    Description: To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.agrformet.2013.11.005 Byline: Stephanie Goffin, Marc Aubinet, Martin Maier, Caroline Plain, Helmer Schack-Kirchner, Bernard Longdoz Abstract: acents We estimate soil CO.sub.2 & [delta].sup.13CO.sub.2 source profiles with the Flux-Gradient Approach (FGA). acents FGA gave consistent results except in Ol which is influenced by turbulent transport. acents Local temperature is the main driver of intra-day & inter-day variability of CO.sub.2 sources. acents Humidity was the main driver of surface [delta].sup.13CO.sub.2 source inter-day variability. acents Variability of [delta].sup.13CO.sub.2 sources was not detected from the [delta].sup.13C of surface fluxes ([delta].sup.13Fs). Author Affiliation: (a) University of Liege-Gembloux Agro-Bio Tech, Unit of Biosystem Physics, 5030 Gembloux, Belgium (b) University of Freiburg, Chair of Soil Ecology, 79085 Freiburg im Breisgau, Germany (c) INRA, Unite d'Ecologie et Ecophysiologie Forestieres, UMR1137, 54280 Champenoux, France (d) Universite de Lorraine, Unite d'Ecologie et Ecophysiologie Forestieres, UMR1137, 70239, 54506 Vandoeuvre les Nancy, France Article History: Received 19 March 2013; Revised 15 November 2013; Accepted 18 November 2013
    Keywords: Soil Ecology – Chemical Properties ; Fibrin – Chemical Properties ; Forest Soils – Chemical Properties ; Soil Carbon – Chemical Properties
    ISSN: 0168-1923
    Source: Cengage Learning, Inc.
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  • 8
    Language: English
    In: Soil Science Society of America Journal, 2012, Vol.76(5), pp.1518-1528
    Description: Atmospheric turbulence can affect soil gas transport, and thus violates the assumption that molecular diffusion is the only relevant transport mechanism in the soil. Due to the oscillating character of turbulence-induced pressure pumping the net vertical air flow into/out of the soil is...
    Keywords: Life Sciences ; Porous-Media ; Air Permeability ; Co2 Production ; Dispersion ; Diffusion ; Exchange ; Balance ; Fluctuations ; Atmosphere ; Equation ; Agriculture
    ISSN: 0361-5995
    E-ISSN: 1435-0661
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  • 9
    Language: English
    In: Journal of Plant Nutrition and Soil Science, April 2017, Vol.180(2), pp.220-230
    Description: Standard procedures to assess P availability in soils are based on batch experiments with various extractants. However, in most soils P nutrition is less limited by bulk stocks but by strong adsorption and transport limitation. The basic principle of root‐phosphate uptake is to strip phosphate locally from the solid phase by forming a radial depletion zone in the soil solution, optionally enhanced by release of mobilizing substances. Microdialysis (MD), a well‐established method in pharmacokinetics, is capable to mimic important characteristics of P root uptake. The sampling is by diffusional exchange through a semipermeable membrane covering the probes with their sub‐mm tubular structure. Additionally, the direct environment of the probe can be chemically modified by adding, ., carboxylates to the perfusate. This study is the first approach to test the applicability of MD in assessing plant available phosphate in soils and to develop a framework for its appropriate use.We used MD in stirred solutions to quantify the effect of pumping rate, concomitant ions, and pH value on phosphate recovery. Furthermore, we measured phosphate yield of top‐soil material from a beech forest, a non‐fertilized grassland, and from a fertilized corn field. Three perfusates have been used based on a 1 mM KNO solution: pure (1), with 0.1 mM citric acid (2), and with 1 mM citric acid (3). Additionally, a radial diffusion model has been parametrized for the stirred solutions and the beech forest soil.Results from the tests in stirred solutions were in good agreement with reported observations obtained for other ionic species. This shows the principal suitability of the experimental setup for phosphate tests. We observed a significant dependency of phosphate uptake into the MD probes on dialysate pumping rate and on ionic strength of the outside solution. In the soils, we observed uptake rates of the probes between 1.5 × 10 and 6.7 × 10 mol s cm in case of no citrate addition. Surprisingly, median uptake rates were mostly independent of the bulk soil stocks, but the P‐fertilized soil revealed a strong tailing towards higher values. This indicates the occurrence of hot P spots in soils. Citrate addition increased P yields only in the higher concentration but not in the forest soil. The order of magnitude of MD uptake rates from the soil samples matched root‐length related uptake rates from other studies. The micro‐radial citrate release in MD reflects the processes controlling phosphate mobilization in the rhizosphere better than measurements based on “flooding” of soil samples with citric acid in batch experiments. Important challenges in MD with phosphate are small volumes of dialysate with extremely low concentrations and a high variability of results due to soil heterogeneity and between‐probe variability. We conclude that MD is a promising tool to complement existing P‐analytical procedures, especially when spatial aspects or the release of mobilizing substances are in focus.
    Keywords: Plant Availability ; Diffusion Limitation ; Spatial Heterogeneity ; Carboxylates
    ISSN: 1436-8730
    E-ISSN: 1522-2624
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  • 10
    Language: English
    In: Journal of Plant Nutrition and Soil Science, February 2012, Vol.175(1), pp.34-45
    Description: Evidence of anisotropy is reported for advective air and water permeabilities in soils. Thus, anisotropy is likely to exist also for diffusive gas fluxes. Information about direction‐dependent soil gas diffusivity is scarce and most modeling approaches assume isotropy. At hundreds of closely lying positions in a compacted and adjacent undisturbed forest soil, gas diffusivity (/) was measured either in vertical or horizontal direction. The volume‐independent diffusion efficiency ( diffusivity divided by air‐filled porosity) was fitted by a generalized additive model (GAM). Significant regressors were air‐filled porosity (ϵ), soil depth, and the discrete diffusion direction. The model yields in all cases higher vertical diffusion efficiencies. The compaction factor did not yield a significant regressor of its own, the reduction of diffusivity in the compacted soil was the same as in low‐porosity samples of the undisturbed profile. To elucidate the role of sharing vertically and horizontally orientated pore space and a potential competition between diffusivity in different spatial directions, simple geometric models consisting of 3‐dimensionally crossed pores have been parameterized. These models provided a good explanation of the typical nonlinear /(ϵ) relationship. By simple one‐parameter correction (linear or power function), this mechanistic model could be fitted to the data. The one‐parameter correction of the geometric model could be a straightforward approach to consider direction dependence of measured diffusivities. However, by applying this approach to the observations the anisotropy effect was not clearly evident, which could be attributed to a changing /(ϵ) relationship with depth. As a reason for the preference of the vertical gas diffusion the dominance of vertical stresses and the activity of anecic earthworms are discussed. Direction dependency of gas diffusivity seems to be a basic feature of natural pore systems and has to be considered for modeling gas fluxes in soils. Generally, a preferential vertical diffusion direction reduces horizontal balancing and increases the heterogeneity of gas concentrations in the soil air.
    Keywords: Diffusion Efficiency ; Anisotropy ; Generalized Additive Model Gam ; Menger Sponge
    ISSN: 1436-8730
    E-ISSN: 1522-2624
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