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  • 1
    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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  • 2
    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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  • 3
    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...
    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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  • 4
    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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  • 5
    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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  • 6
    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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  • 7
    Language: English
    In: Vadose Zone Journal, 2011, Vol.10(1), p.169
    Description: The gradient method used to quantify gas fluxes in soils is based on Fick's second law. The production term is proportional to the second derivative of the concentration profile. Existing methods reveal important limitations, however. We suggest dividing the soil into homogeneous finite elements consisting of second-order polynomials for the gas concentration. A new statistical procedure combining the mechanistic constraints with quadratic splines was used to estimate the derivatives of scattered gas data. The method was tested in a Picea abies (L.) H. Karst. stand for CO (sub 2) and N (sub 2) O depth profiles. The field results yielded a mean annual efflux of 5.9 Mg ha (super -1) yr (super -1) CO (sub 2) -C, of which 86% originated from the mineral soil. The Ah horizon and the forest floor of both plots yielded around 0.8 kg ha (super -1) yr (super -1) N (sub 2) O-N. In the subsoil, N (sub 2) O-N production revealed a high spatial heterogeneity. To test for robustness, synthetic data sets were simulated for re-estimation of belowground gas fluxes with the new procedure and with linear and exponential fits. When only the efflux at the surface was considered, both the finite element method and the local linear fit yielded results close to the expected value. For the deeper soil, the finite element fit yielded unbiased results as long as the preconditions were fulfilled. Otherwise, and this applied also to the alternative methods, results were rather arbitrary. Until now, no alternative to the gradient method for gas flux estimation in the deeper soil has been available. Therefore, deep soil gas flux estimations are questionable as long as the preconditions for the differentiating method are not thoroughly confirmed. As an alternative, we suggest an inverse parameter optimization based on a numerical solution of Fick's second law.
    Keywords: Environmental Geology ; Air ; Algorithms ; Biogenic Processes ; Biota ; Boundary Conditions ; Carbon Dioxide ; Climate ; Climate Change ; Concentration ; Depth ; Diffusivity ; Fick'S Second Law ; Field Studies ; Finite Element Analysis ; Functions ; Gases ; Global ; Greenhouse Gases ; Inverse Problem ; Mechanism ; Nitrous Oxide ; Numerical Models ; Quantitative Analysis ; Regression Analysis ; Respiration ; Rhizosphere ; Simulation ; Soil Gases ; Soils ; Statistical Analysis ; Vegetation;
    ISSN: Vadose Zone Journal
    E-ISSN: 1539-1663
    Source: CrossRef
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  • 8
    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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  • 9
    Language: English
    In: Journal of Plant Nutrition and Soil Science, April 2012, Vol.175(2), pp.236-244
    Description: Several methods are used for the extraction of soil solution. The objective of this study was to find out to what extent the different extraction methods yield complementary or equivalent information. Soil solutions were sampled once at 10 different forest sites in Germany, with 4 sampling points per site, using 5 different extraction methods. Concentrations of the major ions in the 1:2 extracts and the equilibrium soil‐pore solutions (obtained from percolation of field‐fresh soil cores) were generally lower than in desorption solutions, suction‐cup solutions, and saturation extracts. Surprisingly, the latter three methods generally yielded equivalent results. However, possible systematic differences between these methods could have been masked by the high small‐scale spatial variability within the sites.
    Keywords: Soil Solution ; Suction Cup ; Saturation Extract ; Desorption Solution
    ISSN: 1436-8730
    E-ISSN: 1522-2624
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  • 10
    Language: English
    In: Soil & Tillage Research, November 2016, Vol.163, pp.14-20
    Description: Rutting caused by heavy machinery during logging operations can lead to loss of trafficability which is a considerable problem in designated skid trail systems. Wide base tires and bogie tracks are common accepted technical options to minimize rut formation. In this work the suitability of 940 mm super wide base tires on trafficability preservation was tested in comparison to 710 mm wide base tires and common used ECO-TRACK™ bogie tracks. An experiment with repeated passes by a heavy forest machine (forwarder) was conducted. Digital elevation models (DEM) of the ruts were created using photogrammetry to assess rut morphology parameters: rut depth, material displacement and erosion relevant depression storage capacity. Photogrammetry was discovered to be a time and cost efficient method to provide highly resolved 3D-data with high precision. Super wide base tires distinctly reduced rut formation compared to 710 mm tires and bogie tracks by more than 50% and 40%, respectively. Displacement of soil material led to the formation of prominent bulges that can be prone to erosion. 710 mm tires and bogie tracks caused the most voluminous bulges due to their strong rut formation. The investigated tire equipment differently affected the surface depression storage of water in the skid trails due to their different lug morphology. Ruts of bogie tracks could retain significantly more surface water than ruts produced by tires. Nonetheless, the absolute depression storage in all cases is rather low, implying that erosion would occur in case of heavy precipitation.
    Keywords: Skid Trail ; Logging ; Photogrammetry ; Agriculture
    ISSN: 0167-1987
    E-ISSN: 1879-3444
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