bluuebunny/crossref_metadata_2025_split huggingface dataset:
Nitrogen Incorporation and Flow Through a Coniferous Forest Soil Profile
Authors: Schimel Joshua P. , Firestone Mary K. 
Published: July 2010

AbstractOne of the major controls on N cycling in forest ecosystems is the dynamics of N in the forest floor. Uptake and movement of NH+4 by the microbial component of a mixed conifer forest soil in central California were examined by injecting 15NH+4 into either the O2 or the A horizon. Distribution of the tracer was constrained by 15 × 30 cm cylinders placed in situ 1.5 yr prior to the experiment. The 15N was followed over 1‐ and 31‐d periods to measure both the short‐term uptake and the longer‐term fate of N. Recovery of 15N was determined in coarse roots, coarse woody detritus, fine detritus, fungal strands, and the bulk soil in each horizon; microbial biomass 15N was determined in the A horizon only. Nitrogen‐dynamics in the forest floor were characterized by a period of rapid microbial NH+4‐uptake after which transformations were slower. The rate of NH+4 immobilization was approximately 200 mg m−2 d−1, giving a turnover time for the NH+4 pool of less than 1 d. In the A horizon, there was no conversion of microbial 15N into soil organic 15N, but there was extensive lateral translocation of 15N from microbial biomass in the bulk soil into coarse dead roots and coarse detritus. There was little vertical translocation up the profile from either the O2 or the A horizons. This work indicates the rapidity of N turnover in the forest floor and suggests that N sequestering in woody residues may be an important fate of N in this forest soil.
Effect of Extractant and Selected Soil Properties on Predicting the Correct Phosphorus Fertilization of Soybean
Authors: Lins I. D. G. , Cox F. R. 
Published: July 2010

AbstractThe rate of phosphorus required to maximize soybean [Glycine max (L.) Merr.] yields is dependent on the concentration of extractable P along with other chemical and mineralogical characteristics of the soil. Clay content, surface area, P adsorption maximum, type of clay, and extractable phosphorus were evaluated in order to enhance the prediction of the rate of P required for optimum soybean growth on seven acid soils in the greenhouse. The soil test extractants were: Mehlich‐1, Mehlich‐3, Bray‐1, and an ion exchange resin method. The critical P level by each extraction method was correlated with clay content and, in one case, also with type of clay. Clay content and surface area were the most effective additional criteria found to improve the prediction of P fertilizer rate. The Mehlich‐3 extractant was superior to Bray‐1 and the resin method; Mehlich‐1 was least predictive. From a practical standpoint, clay content and extractable P offer the best means of predicting the rate of P required.
Gypsum Occurrence in Soils on the Margin of Semipermanent Prairie Pothole Wetlands
Authors: Steinwand A. L. , Richardson J. L. 
Published: July 2010

AbstractA series of three wetlands in a local recharge‐throughflow‐discharge groundwater flow system were investigated to determine factors controlling concentration of gypsum at the wetland edge. The three wetlands differ in pond size, permanence, salinity, and in their relationship to the groundwater hydrology. We believe gypsum accumulation resulted from long term hydrologic, geomorphic, and climatic factors. Wetland salinity appeared to control the distribution and amount of gypsum in soils around individual wetlands and between wetlands. In all wetlands gypsum was concentrated at the edge; presumably as a result of dissolved salt transport to an area of low water potential created by evapotranspiration and freezing (edge effect). The water flow from the edge effect converged on the peninsulas and diverged in the bays. Consequently in less saline wetlands, the bay soils contained minimal amounts of gypsum; peninsula soils were very gypsiferous. Wetlands of high salinity were surrounded by a continuous band of evaporites including gypsum. Within individual wetlands, differences in the degree and number of ponding events and groundwater recharge‐discharge resulted in variations in gypsum distribution across soils of the low prairie, wet meadow, and shallow marsh vegetation zones.
Effect of Crystalline Iron Oxides on Development and Classification of Podzolic Soils in Western Labrador, Newfoundland
Authors: Wang C. , Ross G. J. , Protz R. 
Published: July 2010

AbstractSeven pedons from western Labrador with various amounts of crystalline Fe oxides in the parent material were studied to determine how Fe oxides inherited from the parent material influence Podzolic soil development in a boreal environment. Amounts of total amorphous Fe oxides did not increase with increasing amounts of crystalline Fe oxides in the soils. Consequently, the ratio of amorphous to crystalline Fe oxide contents decreased sharply with increasing crystalline Fe oxide contents. This decrease is attributed to the resistance of crystalline Fe oxides to weathering and decomposition. Goethite was the only form of crystalline Fe oxide identified in the clays of soils with low crystalline Fe oxide contents. About equal amounts of goethite and hematite were identified in the clays of soils with medium and high crystalline Fe oxide contents. Smectite and vermiculite were the major clay minerals in the E horizon of soils with low and medium crystalline Fe oxide contents. However, only small amounts of these minerals were present in the E horizon of the soil with high crystalline Fe oxide contents in spite of relatively large amounts of potentially expandable silicates such as mica. One of the current criteria of the spodic horizon, (Fe + Al)p/(Fe + Al)d, was found to be too restrictive for soils developed on materials containing medium to high crystalline Fe oxide contents and should be deleted.
Assessing Physical Conditions of Some Pacific Northwest Volcanic Ash Soils After Forest Harvest
Authors: Geist J. Michael , Hazard John W. , Seidel Kenneth W. 
Published: July 2010

AbstractA study of impacts of forest harvest on volcanic ash soils was conducted on three National Forests in the Blue Mountains of Eastern Oregon and Washington. Surface soil conditions were assessed in 11 forest harvest units; sampling employed a randomly positioned grid of randomly oriented line transects. In addition, air permeameter readings were tested in seven units for correlation with bulk density values obtained from core samples. Most of the detrimental soil conditions detected were attributable to compaction. Displacement, although readily apparent during harvest or slash piling with ground‐based equipment, was nearly undetected by the methods used on these units, which ranged from 14 to 23 yr old. Detrimental compaction averaged 28 or 19% of the harvest unit area when defined as either a 15 or 20% increase in bulk density, respectively. Area percentages included skid trails and landings but not the transportation system. Statistical tests showed that either 5 or 3 of the 11 units exceeded 20% area in detrimental condition, depending on degree of bulk density increase used to define detrimental compaction. Several other units were borderline in exceeding 20% of the area. Given slow recovery from compaction, there is potential for additional area to be adversely impacted by future entries. Air permeameter readings were poorly correlated with bulk density assessments, even though six of seven correlations were statistically significant. Less than 12% of the total variability was accounted for by regression analyses. The air permeameter does not appear to be accurate enough to measure compaction in volcanic ash soils.
Iron and Trace Metals in Some Tidal Marsh Soils of the Chesapeake Bay
Authors: Griffin T. M. , Rabenhorst M. C. , Fanning D. S. 
Published: July 2010

AbstractSediments from six tidally influenced Chesapeake Bay marshes were sequentially extracted in order to determine their relative Fe, Zn, Cu, Pb, Ni and Cd content, and to ascertain the relative magnitude of the mechanisms (e.g. adsorption, sulfide occlusion, organic complexation etc., ‥) involved in their retention. The extraction sequence used, and the corresponding geochemical phases extracted were: 0.01 M DTPA (exchangeable, organic complexes); 0.1 M HC1 (monosulfide occluded); dithionite citrate bicarbonate (DCB) (Feoxide occluded); H2O2 (disulfide occluded, organically bound complexes); HF‐HNO3‐HC104 (silicate mineral component). The sediments were dated using 210Pb geochronology in an effort to evaluate historical rates of metal deposition. Marshes in the vicinity of Baltimore, MD harbor were found to contain relatively higher metal concentrations than those marshes in other areas of the bay thus indicating that the degree of metal contamination is related to the source distance. Rates of deposition were related to historical periods of industrial discharge and to the use of leaded fuels. Iron was retained in the marsh sediments mainly in the oxide and sulfide (FeS2) phases and was apparently controlled by redox conditions. Copper, Cd and to a lesser extent Zn and Ni were apparently controlled by sulfide precipitation and pyrite coprecipitation thus rendering them noninfluential and unavailable to the marsh biota. Lead however, appears to be weakly complexed by organics and is a potential ecological threat since it is more readily available to plants and organisms and thus may accumulate in the food chain.
Microbial Utilization of Carbon‐14‐Glucose in Aerobic vs. Anaerobic Denitrifying Soils
Authors: Parsons Laura L. , Smith M. Scott 
Published: July 2010

AbstractIn order to better characterize the behavior of denitrifying bacteria in soil and their effect on cycling of C and N, the rate of consumption and the extent of microbial assimilation of glucose were compared in aerobic and anaerobic denitrifying soils. Three soils (Bruno, a Udifluvent; Maury silt loam, and Paleudalf; and Lanton, a Haplaquoll) were amended with 14C‐glucose and excess NO‐3, then incubated for 3 to 7 d in air or anaerobically. Transient accumulations of soluble, nonglucose intermediates occurred in both aerobic and anaerobic soils. Aerobic substrate consumption rates were greater than anaerobic denitrifying substrate consumption rates. Anaerobic substrate consumption rate varied among soils more than aerobic rates, but the ratio of aerobic to anaerobic rates for a sample was not related to the presumed propensity of that soil type to denitrify. When all labelled glucose had been depleted, 8 to 10% more of the label had been mineralized to CO2 in the anaerobic than in aerobic incubations, suggesting lower efficiency of assimilation under denitrifying conditions. However, the effect of aerobic vs. denitrifying respiration on assimilation efficiency was small relative to differences among soil samples and the effects of substrate‐to‐soil ratio.
Evidence for Clay Translocation in Coastal Plain Soils with Sandy/Loamy Boundaries
Authors: Cabrera‐Martinez F. , Harris W. G. , Carlisle V. W. , Collins M. E. 
Published: July 2010

AbstractSoils of the Atlantic Coastal Plain commonly have thick sandy epipedons overlying loamy subsurface horizons. The origin of these sandy/loamy boundaries is often uncertain, due to frequent lack of visible indications of clay translocation. Five soils, which varied in depth to a sandy/loamy boundary, were analyzed for evidences of lithological discontinuity and clay translocation. Four of these soils occurred in close landscape association; the fifth soil, formed in an obviously stratified parent material, was included to test the sensitivity of the methods used. No evidence of a discontinuity was found for the four associated soils. Ratios of dominant sand subfractions to total sand were relatively uniform with depth, as was heavy mineral content of very fine sand. The stratified soil, however, exhibited considerable fluctuation in these parameters. Clay translocation was indicated by (i) the presence of oriented clay coatings on ped surfaces in the Btg horizon of one soil, as verified by micromorphological techniques; and (ii) significantly higher fine‐clay to total‐clay ratios below the sandy/loamy boundary than above. Results suggest that clay illuviation is a factor in the formation of sandy/loamy boundaries in some Coastal Plain soils even when the boundary is relatively deep (>50 cm).
Use of Geostatistics in Designing Sampling Strategies for Soil Survey
Authors: Di H. J. , Kemp R. A. , Trangmar B. B. 
Published: July 2010

AbstractSemivariograms are used to quantitatively assess spatial variability of depth to mottles, depth to gravels, and thickness of loamy sand and/or coarser‐textured layers, which are definitive criteria for classification of soils derived from alluvium on the Canterbury Plains near Lincoln College, New Zealand. The three properties vary anisotropically with the anisotropy ratio being highest for depth to mottles (k = 5.84), lowest for thickness of loamy sand and/or coarser‐textured layers (k = 1.58), and intermediate for depth to gravels (k = 2.43). Directions of maximum variation for depth to mottles and depth to gravels are NE‐SW across an abandoned channel hollow. This pattern is reflected in the soil map of the study area and in the smaller‐scale soil map of the adjacent region. Such variation reflects the past regional drainage patterns of channels flowing predominantly in a NW‐SE direction. The appropriate field configuration of a sampling scheme for future survey of similar adjacent soils would be rectangular with a sample spacing in the direction of least variation k (anisotropy ratio) times that in the direction of maximum variation. Suitable sample numbers and sampling intervals to achieve desired levels of precision in the direction of maximum variation are determined. These are obtained from graphs showing relationships between kriging standard error, sample spacing and sample number. This geostatistical approach is more efficient than conventional statistical methods in designing sampling strategies: less samples are needed for kriging than for the conventional method to achieve the same level of precision.
Water Relationships of Claypan and Constructed Soil Profiles
Authors: Hauser Victor L. , Chichester F. W. 
Published: July 2010

AbstractClaypan soils with poor physical properties are the only surface materials available to cover and reclaim much of the spoil left by strip mining for coal in east‐central Texas. We compared an undisturbed claypan soil profile of Axtell fsl fine montmorillonitic, thermic Udertic Paleustalfs) to four constructed soil profiles and evaluated them as cover soils for toxic minespoil. We compared profiles constructed from minespoil selected for low pyrite content alone (non‐topsoiled) against the same selected spoil covered by a mixture of Axtell soil material. The rainfall intake rate and physical properties of the materials controlled forage production by kleingrass (Panicum coloratum L.). All of the constructed soils stored less water in the soil profile than the undisturbed claypan soil, and forage yield was reduced on them during drought. Infiltration rate during the first 2 cm of rainfall influenced forage yield more than final intake rate. Mulch application increased water storage and forage yield up to 15% on selected minespoil, but not on the mixed claypan soil profiles. Either selected minespoil or a mixture of Axtell soil may be used to cover toxic random soil with a nontoxic layer, but the Axtell mix had the least acid‐forming potential. Selected minespoil material was equal in value to a mixture of the 1.8 m claypan soil profile as a surface material for constructed minesoils.
Effect of Acid Treatment on Dissolved Organic Carbon Retention by a Spodic Horizon
Authors: Vance George F. , David Mark B. 
Published: July 2010

AbstractProcesses involving the movement of organic substances in forest soils are not well understood. This study was conducted to examine the role of acidic inputs on dissolved organic carbon (DOC) mobility, processes affecting the retention of DOC by a B horizon, and SO2‐4 adsorption. Using O and B horizon samples from a Spodosol collected in a forested watershed in Maine, acid solutions leached through O, B, and O over B (O/B) soils in small vacuum extractor columns were analyzed for DOC, DOC fractions, and anions. For the O and O/B columns, DOC in the leachates decreased (7550 to 3350 and 2380 to 850 µmol C L−1, respectively) with an increase in acidic inputs; for the B horizon, the reverse was the case (435 to 1570 µmol C L−1). The DOC in leachates from the O horizon was dominated by hydrophobic and hydrophilic acids (68 and 20% of DOC with no acid addition), which were altered by acidic inputs (46 and 36% of DOC at p[H+] = 2). The hydrophobic acid percentage in leachates from O/B horizon columns decreased from 52 to 28%, whereas hydrophilic acids increased from 27 to 47% with H2O and p[H+] = 2 treatments, respectively. Ionic strength adjustment (I = 0.01) of treatment solutions reduced C solubilization in O and O/B horizon leachates, leading to lower DOC leaching. The SO2‐4 adsorption in O over variable B horizon columns decreased with greater B horizon mass due to pH dependent SO2‐4 adsorption processes. The B horizon adsorption of DOC from field collector leachates showed that hydrophobic acids were selectively adsorbed, as indicated by initial mass isotherm coefficients. The results indicated that acidity, salt effects, and B horizon mass are significant factors in controlling both the amount and composition of DOC in surface and groundwaters.
Nature and Charge Properties of X‐Ray Noncrystalline Aluminosilicates as Affected by Citric Acid
Authors: Lou G. , Huang P. M. 
Published: July 2010

AbstractThe surface charge properties of x‐ray noncrystalline aluminosilicates in relation to their structural distortion by citric acid during their formation were investigated. The precipitates formed from solutions containing monomeric orthosilicic acid and AlCl3 (Si/Al molar ratio 0.5 and OH/Al molar ratio 2.0) in the presence of citric acid (citrate/Al molar ratios of 0.02 and 0.025) exhibit an IR absorption maximum at 965 cm−1, a feature similar to that of “allophane‐like constituents” or “ill‐defined fraction of the allophane‐imogolite complex” in soil. The complexation of citrate ligand with hydroxy‐aluminosilicate ions or “proto‐imogolite”, the precursor of paracrystalline to x‐ray noncrystalline aluminosilicates, promoted the development of structural defects apparently through perturbation of the regular linkage of hydroxy‐aluminosilicate fragments. The perturbation effect of citrate ligands promoted the development of positive charge and resulted in a marked increase in the point of zero charge (PZC) due to the exposure of Al‐OH0.5+2 groups around the defect sites. The role of complexing organic ligands in influencing the surface properties of short‐range ordered aluminosilicates through structural distortion thus deserves attention.
Water Transport in Unsaturated Nonisothermal Salty Soil: II. Theoretical Development
Authors: Nassar I. N. , Horton Robert 
Published: July 2010

AbstractA theory describing both vapor and liquid phases of moisture transfers in porous materials is developed. The two equations included extend previous work, which only considered moisture and temperature gradients, by also including solute concentration effects. The new equations include six diffusivities to be considered in describing vapor and liquid movement in soil. Three liquid diffusivities are for liquid‐phase flow associated with water content, temperature, and solute concentration, and three vapor diffusivities are for vaporphase flow. Steady‐state heat and mass transfer laboratory experiments were performed by using moist salinized and solute‐free closed soil columns. From observations of water content, temperature, and solute distributions, five of the diffusivities (vapor diffusivities due to temperature, water, and solute concentration and liquid diffusivities due to temperature and solute concentration) are determined. The isothermal liquid diffusivity as a function of soil water content is determined in a separate experiment. In general, the liquid diffusivities are larger than the vapor diffusivities for the experimental conditions considered. For the soil conditions investigated, the water fluxes due to the solute gradients are nearly equal to the water fluxes due to the temperature gradients within salinized soil columns, but the water fluxes resulting from gradients in soil water content are small in comparison. To test the validity of the theory, two different approaches are used. The first approach involves using water diffusivities of moist solute‐free soil along with the new theory to predict steady‐state water distributions within moist salinized soil for comparison with observations. The predicted values of soil water content are in good agreement with the observed values. The second approach is to predict steady‐state soil water distributions within the moist salinized soil column while neglecting the solute effects on soil water movement. The predictions using this approach are markedly different from the experimental observations.
A Spectroscopic and Chemical Investigation on the De‐ashing of a Humin
Authors: Preston C. M. , Schnitzer M. , Ripmeester J. A. 
Published: July 2010

AbstractThe application of 13C cross‐polarization magic‐angle spinning nuclear magnetic resonance (CPMAS NMR) to humins has been limited because low C and high Fe contents degrade spectral quality. This study investigated the effect of de‐ashing with aqueous HCl/HF (1.16 M HCl and 2.88 M HF) on chemical properties and 13C CPMAS NMR spectra of a humin. With progressive de‐ashing, the humin became partly soluble in 0.5 M NaOH, and its ash‐free composition approached that of the humic acid fraction. The CPMAS NMR spectra showed increasing improvement in resolution and signal‐to‐noise ratio. The spectrum of the most extensively de‐ashed sample (520 g C kg−1) was very similar to that of the humid acid extracted from the same soil. The de‐ashing treatment caused variable changes in the distribution of N determined after acid hydrolysis, but little change in the molar distribution of amino acids. Some monosaccharides were lost, and there was a change in the monosaccharide composition, with glucose predominating (on a molar basis) in the most extensively de‐ashed samples. It is unlikely that major structural changes were caused by the de‐ashing, which provides a useful approach to the NMR investigation of humins.