bluuebunny/crossref_metadata_2025_split huggingface dataset:
Turnover of Detrital Organic Carbon in a Nutrient‐Impacted Everglades Marsh
Authors: DeBusk W. F. , Reddy K. R. 
Published: July 2010

AbstractPhosphorus loading to the Everglades from nearby agricultural areas has become a major concern, and is considered to be a significant factor in the encroachment of cattail (Typha domingensis Pers.) and other rapidly growing vegetation into endemic sawgrass (Cladium jamaicense Crantz) marsh. The objectives of this research were to evaluate the variability in turnover of organic C in plant and soil detrital pools along a P enrichment gradient in an Everglades marsh and to identify substrate characteristics and environmental factors controlling C turnover. Potential rates of C mineralization in plant litter and peat were determined by measuring aerobic and anaerobic microbial respiration under controlled conditions in laboratory incubations. Potential C mineralization decreased with depth and, consequently, substrate age, in the plant‐soil profile. Within individual detrital pools [standing dead plant material, soil litter layer, surface peat (0–10 cm depth) and subsurface peat (10–30 cm depth)], potential C mineralization decreased down gradient from the source of nutrient loading to WCA‐2A. Overall, 91% of the variability in aerobic C mineralization in peat and plant litter was accounted for by substrate P concentration and lignocellulose composition. Anaerobic C mineralization rates were consistently about one‐third of aerobic rates. Results indicated that organic C turnover in detrital pools in WCA‐2A is significantly affected by accelerated P loading, but is also controlled by O2 availability and substrate C quality.
Scaling Water Retention Curves for Soils with Lognormal Pore‐Size Distribution
Authors: Kosugi K. , Hopmans J. W. 
Published: July 2010

AbstractThe scaling theory approach has been widely used as an effective method to describe the variation of soil hydraulic properties. In conventional scaling, reference retention curves and scaling factors are determined from minimization of residuals. Most previous studies have shown that scaling factors are lognormally distributed. In this study, we derived physically based scaling factors, assuming that soils are characterized by a lognormal pore‐size distribution function. The theory was tested for three sets of retention data. Two data sets included samples of a sandy loam soil, and one set included samples of a loamy sand soil. Individual soil water retention data were fitted to the retention model proposed by Kosugi (1996). The parameters of the model are the mean and variance of the log‐transformed poreradius distribution. Scaling factors and parameters of the reference curve were computed directly from the parameters of individual soil water retention functions. Assuming that (i) the soil pore radius of a study area is lognormally distributed and (ii) soil samples are obtained from random sampling of effective soil pore volume from the study area, we have proposed a theoretical interpretation of the lognormal scaling factor distribution. Scaling results for all three data sets compared well with those obtained using the conventionals caling method.
The Significance of Hysteresis in Modeling Solute Transport in Unsaturated Porous Media
Authors: Mitchell Robert J. , Mayer Alex S. 
Published: July 2010

AbstractPrevious investigations disagree as to the appropriateness of neglecting hysteresis with regard to predicting solute transport under transient conditions, primarily because of the unique porous media and conditions used in these studies. In the present study, the significance of hysteresis in predicting solute transport in the near‐surface region is investigated using one‐dimensional, homogeneous numerical experiments with a fully hysteretic flow and transport model. The experiments involve introduction of a solute pulse, followed by intermittent cycles of infiltration, redistribution, and evaporation. Comparisons are made between transient hysteretic simulations and simulations ignoring hysteresis. Hysteretic and nonhysteretic simulations conducted with porous media that have large differences between wetting and draining characteristic curves exhibited the greatest variation in solute migration behavior. Larger differences between maximum and minimum water contents also produced greater impacts when hysteresis was considered. However, the results indicate that the magnitude of the deviations between hysteretic and nonhysteretic simulations is not a simple function of each independent parameter, but rather depends on the combined values of many or all of the hydraulic parameters. As the solute travels further into the vadose zone, the effects of hysteresis are reduced. In general, hysteresis had a minor effect on solute transport in the systems considered in this work.
Stratigraphic Approach to Alteration in Mineral Soils: The Heavy Metal Example
Authors: Kleber Arno , Mailänder Reiner , Zech Wolfgang 
Published: July 2010

AbstractQuantifying post‐depositional alteration of mineral soil material is complicated by the fact that many soils consist of layered parent materials with varying indigenous composition. Part of our study site in the Steigerwald Mountains of northern Bavaria was cultivated during the Middle Ages and later reforested. Soil erosion removed the upper materials, exposing a deposit to contamination from the surface, whereas nearby, the deposit remained protected by overlying layers. We compared heavy metal concentrations within that deposit across this boundary of varying protection. No significant results were obtained for Cd; however, the concentrations of Pb and Cu increase by about 100% or more where the protecting cover thins. The Pb and Cu values provide a measure of the gross post‐depositional alteration of that deposit. We expect this procedure can help quantify various pedogenic alterations by comparison with essentially the same, unaltered parent material.
Origin and Acceptance of the Term Pedology
Authors: Simonson Roy W. 
Published: July 2010

AbstractAfter F.A. Fallou (1794–1877) introduced the term pedology in Saxony in 1862, it was dormant for some decades. Acceptance and general use of the term began in Russia following development of a new approach to the study of soils by Dokuchaiev and his students in the late 1870s and early 1880s. Soil scientists elsewhere in the world did not pick up the term, however, before the 20th century. Widespread use followed the First International Congress of Soil Science, held in the USA in 1927. The Congress and associated activities gave the term a big boost, not only in the USA. In 1929, the American Soil Survey Association, precursor of the Soil Science Society of America, adopted a resolution urging that pedology be accepted as the proper name for scientific investigations of soils. Teaching of the Dokuchaiev factors of soil formation, which began soon afterward, promoted progressively wider acceptance of the term, especially in the USA. These trends culminated in adoption of pedology as the name for a division of the Soil Science Society of America in 1994. During the same period, acceptance of the term was underway in all parts of the world.
Soil Shrinkage Characteristic Curve in Clay Soils: Measurement and Prediction
Authors: Crescimanno Giuseppina , Provenzano Giuseppe 
Published: July 2010

AbstractLaboratory determination of soil hydraulic characteristics (HC) is performed on cylindrical confined soil cores, while resin‐coated small natural aggregates are prevalent for determining the Soil Shrinkage Characteristic Curve (SSCC). Because of the different geometry and volume of clods and cores, incorporation of shrinkage in HC of clay soils could be affected by the use of SSCC determined on natural aggregates or on confined cores. The objectives of this study were (i) to investigate differences between the SSCC obtained on resin‐coated natural aggregates (volume V = 20–30 cm3) and on cylindrical confined cores having a volume (650 cm3) close to that of cores used for HC laboratory determination, (ii) to test the performance of different models proposed for analytical interpretation of the SSCC, and (iii) to derive regression equations predicting the SSCC from routinely measured soil physical properties. Using twenty‐one Sicilian soils of variable shrink‐swell behavior, we found significantly larger specific volume (n), indicating less shrinkage, in the cylindrical confined cores. The investigation also proved the good fitting of a two‐line model to the measured SSCC and the possibility to predict the basic shrinkage line from the clay content. These results suggest that incorporation of shrinkage in HC of clay soils should be based on the SSCC measured or predicted on cores with geometry and dimensions as those used for routine laboratory measurement of HC.
The Colding Equation for Soil Drainage: Its Origin, Evolution, and Use
Authors: van der Ploeg R. R. , Marquardt Maria , Kirkham M. B. 
Published: July 2010

AbstractThe derivation of the ellipse equation by the Danish engineer Colding in 1872 marked the beginning of a new epoch in the field of soil drainage. Little is known about the circumstances that led to the derivation of this equation or about the evolution of the Colding equation in later years. Therefore, we decided to survey the early European literature on these subjects. The survey revealed that Colding's derivation was based mainly on research published by the French engineer Delacroix in 1859 and by the Danish engineer Hannemann in 1870. Although Colding used soil water flow concepts as developed earlier by Darcy and Dupuit, it is possible he was not familiar with the work of these French engineers. After Colding's equation had been widely used for drainage design purposes in Denmark, his equation appeared in the German literature around the turn of the century. From Germany, the Colding equation spread to other European countries and to the USA. In the 1930s and the 1940s, the Colding equation was modified by Hooghoudt in the Netherlands and by Aronovici and Donnan in the USA. The Hooghoudt equation is used today as a drainage design standard in various parts of the world.
A Capacitance Sensor with Planar Sensitivity for Monitoring Soil Water Content
Authors: Ruth B. 
Published: July 2010

AbstractA pair of isolated parallel wires in a frame were used as a capacitance sensor for soil water content determination. Due to the high dielectric constant of water, rising water content of th esoil between the wires increases the capacitance. As the frame and the wires have a horizontal position in the soil, no preferential vertical water flow is induced by the sensor. The total wire diameter of 1.1 mm and the separation of 2.5 mm leave enough space for undisturbed natural water flow. The sensitive volume has a thickness given by the wire separation of 2.5 mm and the open frame area of 5 by 5 cm. Measurements in two soil types (loamy sand and loamy silt) showed a rise of the capacitance from 15 to 65 pF when the water content increases from 0 to 0.45. A theoretical consideration exhibits the relationship between the measured dielectric constant εM and the volumetric water content θ given by εM = A(θ + Z)/(θ + N) with three parameters A, Z, and N depending only on the sensor geometry and dielectric constants. The corresponding fit function determined the parameters and approximated the calibration curve with a root mean square (RMS) deviation of 0.024, indicating the accuracy of the method. No significant difference in the εM‐θ relationship could be obtained between the two soils. Measurements with eight sensors at depths between 1 and 15 cm yield the time‐dependent water content profile with a resolution of 1 cm during the watering and drying of the soil.
Technical Note: Rapid Measurement of Soil Sorptivity
Authors: Smith Roger E. 
Published: July 2010

AbstractA simple and fast method is described for measuring surface soil sorptivity, S. Rather than measure the progress of infiltration flux for a long initial period, the cumulative infiltration is measured in the early stage in which the gravity effect is negligible. The theory behind the method is sound and simple, and measurements may be taken in only a few minutes using a small single ring. It is applicable to find S for both ponded and flux surface boundary conditions.
Atomic Force Microscopy and Surface Characteristics of Iron Oxides Formed in Citrate Solutions
Authors: Liu C. , Huang P. M. 
Published: July 2010

AbstractSurface geometry of minerals greatly influences the physical, chemical, and biological processes occurring on the surface. However, a quantitative or even a qualitative description of the surface geometry of minerals has proven to be extremely difficult. In our study, the fine‐scale morphology (1 by 1 µm scale) and surface geometry described by mean surface roughness and surface fractal dimension of Fe oxides formed at various concentrations of citrate, which is common in terrestrial and aquatic environments, were investigated by atomic force microscopy (AFM). Specific surface area and Point of Zero Salt Effect (PZSE) of the Fe oxides, as well as P adsorption, were also studied. Citrate present during the formation of Fe oxides significantly altered the fine‐scale morphology, surface geometry, and other surface characteristics of the products. The mean surface roughness and surface fractal dimension determined by AFM measured the degree of the disorder of surface structure of Fe oxides. The modification of the surface characteristics of the Fe oxides by coprecipitated citrate through fundamental structural changes and the blocking of P‐adsorption sites by citrate affected the P adsorption. Due to the hindrance of the crystallization process, P adsorption per unit weight of the Fe oxides formed at 10‐3 M citrate was very significantly enhanced. The fine‐scale morphology, surface geometry, and related surface characteristics of Fe oxides formed under the influence of organic acids merit close attention as we advance our understanding of their surface chemistry pertaining to dynamics and transformations of nutrients and pollutants in terrestrial and aquatic environments.
Amino Sugars in Native Grassland Soils along a Climosequence in North America
Authors: Amelung W. , Zhang X. , Flach K. W. , Zech W. 
Published: July 2010

AbstractCharacterizing amino sugars is important for further understanding soil organic matter (SOM) dynamics in terrestrial ecosystems. This study was designed to evaluate the impact of climate on amino sugars in 18 surface soil (0–10 cm) samples along a climosequence of native grasslands from central Saskatchewan, Canada, to Southern Texas, USA. Mean annual temperature (MAT) ranged from 0.9 to 23.4°C and mean annual precipitation (MAP) from 300 to 1308 mm. In all samples, the contents of soil organic C, glucosamine, mannosamine, galactosamine, and muramic acid were determined. Both the ratios of glucosamine to galactosamine and of glucosamine to muramic acid were related to the moisture regime. With increasing MAP, increasing proportions of amino sugars were glucosamine. This glucosamine is possibly derived from the chitin of fungi. The proportion of bacterial‐derived amino sugars, such as muramic acid, declined as MAP increased. The relationship between amino sugar concentrations (mg kg‐1 soil organic C) and MAT followed a parabolic regression model; the maximum of the amino sugar concentration occurring at the mesic temperature regime. On the basis of hierarchical cluster analysis the sites could be divided into two groups, which coincided with the Northern‐central and Southern grasslands. We hypothesize that in the Northern‐central grasslands frost limits amino sugar production whereas in the Southern grasslands higher winter temperatures >0°C favor amino sugar decomposition.
Chloride Versus Sulfate Salinity Effects on Alfalfa Shoot Growth and Ionic Balance
Authors: Soltanpour P. N. , Ippolito J. A. , Rodriguez J. B. , Self J. , Gillaume M. , Al‐Wardy M. M. , Mathews D. 
Published: July 2010

AbstractInformation on Cl vs. SO4 salinity effects on alfalfa (Medicago sativa L) dry matter yield (DM) and cation‐anion balance is limited. Consequently, we compared Cl and SO4 salinity effects on shoot DM and ionic balance for Archer and Ladak varieties of alfalfa. A modified, flowing Hoagland solution, buffered with CaCO3, was the control: electrical conductivity (EC) = 0.7 dS m‐1. Chloride or SO4 salts of K, Ca and Mg were added to the control to get iso‐EC solutions (2–11 dS m‐1). Shoot cations (Ca, Mg, K, and Na) and their sum (C), anions (Cl, SO4, NO3 and H2PO4) and their sum (A), and DM were measured. Organic anions (C‐A) were calculated in mmolc kg‐1. The calculated hydroponic osmotic potentials (π) were from 1.4 to 1.7 times lower in Cl than in iso‐conductive SO4 solutions. As EC increased, DM decreased equally for both varieties in iso‐conductive Cl and SO4 solutions. Solution π decreased, shoot H2PO4 declined below its critical level of 65 mmolc kg‐1, shoot C stayed constant, shoot A increased; and therefore, shoot C‐A decreased. The shoot C‐A was lower in SO4 solutions. In Cl solutions shoot Cl exceeded the toxic level of 282 mmolc kg‐1. The DM was correlated positively with π, shoot H2PO4, and C‐A, and negatively with shoot Cl and SO4. We conclude that (i) iso‐conductive Cl or SO4 salinity depress DM equally, but isoosmotic SO4 is more depressive; (ii) the yield declines are probably due to any one or a combination of low water potential, toxic shoot Cl and possibly SO4, and deficiencies of shoot P and organic anions; (iii) neutral organic solutes were probably responsible for osmotic adjustment, since total ionic charges (2C) stayed constant; and (iv) P deficiency occurred despite high solution P, due to Cl or SO4 competition in saline environments.
Barometric Process Separation: New Method for Quantifying Nitrification, Denitrification, and Nitrous Oxide Sources in Soils
Authors: Ingwersen J. , Butterbach‐Bahl K. , Gasche R. , Richter O. , Papen H. 
Published: July 2010

AbstractA method (Barometric Process Separation, BaPS) was developed for the quantification of gross nitrification rates and denitrification rates in oxic soil using intact soil cores incubated in an isothermal gas tight system. Gross nitrification rates and denitrification rates are derived from measurements of changes (i) in air pressure within the closed system, which are primarily the result of the activities of nitrification (pressure decrease), denitrification (pressure increase), and respiration (pressure neutral), and (ii) of O2 and CO2 concentrations in the system. Besides these biological processes, the contribution of physicochemical dissolution of produced CO2 in soil water to the pressure changes observed is to be considered. The method allows collection of additional information about the contribution of nitrification and denitrification to N2O emission from soil, provided simultaneous measurements of N2O emission are performed. Furthermore, BaPS can be used to quantify the percentage of N2O lost from nitrification. The advantage of BaPS is that disturbance of the soil system is minimized compared with other methods such as the use of gaseous inhibitors (e.g., acetylene) or application of 15N compounds to the soil. We present the theoretical considerations of BaPS, results for nitrification rates, denitrification rates, and identification of soil N2O sources in a well‐aerated coniferous forest soil using BaPS. The suitability of BaPS as a method for determination of gross nitrification is demonstrated by validation experiments using the 15N‐pool dilution technique.
Structural Charge and Cesium Retention in a Chronosequence of Tephritic Soils
Authors: Chorover Jon , DiChiaro Marnie J. , Chadwick Oliver A. 
Published: July 2010

AbstractMineral transformation during the course of soil development is probably coupled to time‐dependent trends in surface‐charge and selective adsorption behavior, but the relationships are not well documented. The density of permanent (structural) charge is subject to change as a result of accretion or depletion of 2:1 layer‐type silicates. The objectives of this study were to measure changes in (i) Cs+ selectivity and (ii) structural charge as affected by pedogenic mineral transformations in an age sequence of Hawaiian soils. The Cs+ → Li+ exchange experiments were conducted on soils collected from six sites [basaltic parent material deposited 0.3, 20, 150, 400, 1400 and 4100 thousands of years (ky) ago]. Identical exchange experiments were performed with kaolinite, montmorillonite, and illite for comparison. Selectivity for Cs+ on soils and clays increased with adsorbed mole fraction of Cs+. Cesium‐accessible structural charge of the surface soils increased initially with soil age from 20 mmolc kg‐1 at the 0.3 ky site to 113 mmolc kg‐1 at the 400‐ky site. Increased weathering beyond 400 ky reduced structural charge to 21 mmolc kg‐1 for the oldest site. Parallel results were observed for subsurface soils with maximum structural charge of 138 mmolc kg‐1 measured for the 400 ky site. The magnitude of Cs retention in the soils is correlated with the presence of 2:1 layer‐type silicates detected by x‐ray diffraction (XRD) after removal of poorly crystalline constituents. The results indicate a modest accumulation of secondary 2:1 layer‐type silicates (with larger accumulations of poorly crystalline clays), followed by their subsequent decline, during the course of soil weathering.
Soil Organic Matter Changes in Intensively Cropped Dryland Systems
Authors: Bowman R. A. , Vigil M. F. , Nielsen D. C. , Anderson R. L. 
Published: July 2010

AbstractContinuous cropping or decreasing the frequency of summer fallow (F) in cereal‐based dryland rotations may have benefits other than greater water utilization and erosion control. We hypothesized that rotations with no fallow or minimum fallow frequency can produce more biomass and cover than the traditional winter wheat (Triticum aestivum L.)‐summer fallow systems (W‐F), and ultimately, greater amounts of soil organic matter (SOM). To this end, we evaluated changes in various pools of SOM at the 0‐ to 5‐ and 0‐ to 15‐cm depths on a Weld loam (fine, smectitic, mesic aridic Paleustolls) that were caused by (i) decreasing fallow or increasing cropping intensities, (ii) specific rotations of the same length but with different crop sequencing, and (iii) accumulated residue and roots from reduced‐ or notillage from 1993 to 1997. Total soil organic carbon (SOC) and N for the 0‐ to 5‐cm depth increased by =20% with continuous cropping rotations compared with W‐F rotations. Particulate organic matter‐carbon (POM‐C) doubled, while POM‐N, and soluble organic C (OC) increased by one third for the same comparison. At the 0‐ to 15‐cm depth, SOC, POM‐C, and POM‐N did not differ among systems with fallow, nor among systems with cropping intensities greater than W‐F. Thus, significant differences always existed between W‐F and continuous cropping. Generally, fallow had a negative influence on SOC accumulation, and continuous cropping a positive influence on surface SOM. Changes in SOC did not correlate with yields in the five‐year comparison of this ongoing study.