bluuebunny/crossref_metadata_2025_split huggingface dataset:
Soils of the Red Fir Forest‐Barrens Mosaic, Siskiyou Mountains Crest, California
Authors: Laurent T. E. , Graham R.C. , Tice K. R. 
Published: July 2010

AbstractIn the crest areas of northern California and southern Oregon mountains, Shasta red fir (Abies magnifica var. shastensis Lemmon) forests are often interspersed with irregularly shaped, 0.1‐ to 50‐ha openings that contain only sparse prostrate forbs and sub‐shrubs amid mostly bare and gravel‐paved soil. We investigated these forest‐barrens associations to determine if soil differences could help explain the cause of the barrens. While the soils (Xerumbrepts) are morphologically similar in many respects, burrowing by abundant pocket gophers (Thomomys sp.) in the barrens produced thicker umbric epipedons than in the forests, where pocket gophers are absent. The only significant soil chemical differences detected between sites were lower concentrations of Ca and Mg in the barrens surface soils. In contrast, base cations accumulate in the forest A horizons as a result of biocycling. While the origin of the barrens remains unknown, herbivory by pocket gophers is a major factor in maintaining the barren conditions and their activity ultimately accounts for most soil chemical and morphological differences.
Temperature‐Dependent Measurement Errors in Time Domain Reflectometry Determinations of Soil Water
Authors: Pepin S. , Livingston N. J. , Hook W. R. 
Published: July 2010

AbstractWith the recent development of improved time domain reflectometry (TDR) probe design, measurement systems, and calibration procedures, it is now possible to detect and quantify the effect of temperature on the soil apparent dielectric constant (Ka). We investigated measurement errors in Ka associated with soil temperature variations and compared measured changes in Ka with those predicted by a dielectric mixing model. After confirming the accuracy and resolution of our measurement system with a series of measurements on distilled water, we measured changes in Ka with temperature for a range of soil types, including sand, loam, and peat, at soil water contents (θv) ranging from 0.09 to 0.81 m3 m−3. The measured variation with temperature in the dielectric constant of distilled water (0.322°C−1) was very close to that reported in the literature (0.356°C−1). In soils, changes in Ka with temperature were highest at high water contents. For soils near saturation, the overall changes observed in Ka with temperature were lower than those predicted by the dielectric mixing model by 17% for sand, 24% for loam, and 39% for peat. These results suggest that the temperature dependence of the dielectric constant of water in a soil matrix is lower than that of bulk water. Absolute water content errors increased linearly with the size of the water fraction, ranging from 8.75 × 10−5 m3 m−3°C−1 at 0.05 m3 m−3 soil water content to 1.40 × 10−3 m3 m−3°C−1 at 0.80 m3 m−3 soil water content. To obtain the highest measurement accuracy, particularly at higher θv, we suggest that a temperature correction of 0.00175θv °C−1 be employed.
Fragipan Genesis in Polygenetic Soils on the Springfield Plateau of Missouri
Authors: James H. R. , Ransom M. D. , Miles R. J. 
Published: July 2010

AbstractSoils on broad ridgetops of the Springfield Plateau in southwestern Missouri typically are covered by a silty mantle about 1 m thick, have developed from multiple parent materials, and contain a fragipan. The objectives of this study were to identify the parent materials, assess the influence of parent material stratigraphy on fragipan expression, and determine processes of fragipan genesis. Two pedons each of Creldon (fine, mixed, mesic Mollic Fragiudalfs) and Captina (fine‐silty, siliceous, mesic Typic Fragiudults) soils were investigated using field, soil characterization, and micromorphological techniques. The parent materials were Late Wisconsinan loess, erosional lag concentrate, and cherty limestone residuum. A composite paleosol developed in the lower two parent materials was merged with the modern soil. Since the composite paleosol was acid and highly weathered, illuviation of carbonates from the overlying loess had minimal effect on the paleosol. Clay and silt, however, were illuviated from the loess into the composite paleosol. The parent material strongly influenced fragipan expression. A fragipan formed only in the erosional lag concentrate, which was probably deposited as a slurry. Micromorphological examination showed close packing of particles in the fragipan. Depth distributions of Al, Si, Mn, and Fe extracted in sodium citrate‐bicarbonate‐dithionite were not useful in establishing if one or more of these constituents was a chemical cement of the fragipan. Close packing of skeleton grains was most responsible for fragipan genesis in these soils and could have resulted from physical ripening of the erosional lag concentrate.
Organic Matter Role in Illitic Soil Colloids Flocculation: III. Scanning Force Microscopy
Authors: Heil Dean , Sposito Garrison 
Published: July 2010

AbstractIn previous papers of this series, the flocculation of illitic colloids separated from Hanford sandy loam diminished with the presence of organic matter that can form coatings on soil colloids. The purpose of this study was to apply scanning force microscopy to image both geologic specimen illite and the Hanford (coarse‐loamy, mixed, nonacid, thermic Typic Xerorthent) soil colloids directly to provide visual evidence of the coatings. Scanning force micrographs showed differences in particle morphology and surface features between the soil and the specimen illite particles that were not interpretable exclusively in terms of organic coatings but did indicate the presence of surface roughness that could inhibit flocculation of the soil illite particles.
Field Method for Measuring Mobile/Immobile Water Content and Solute Transfer Rate Coefficient
Authors: Jaynes D. B. , Logsdon S. D. , Horton R. 
Published: July 2010

AbstractNumerous field and laboratory studies have documented the occurrence of preferential transport of solutes due to a fraction of the soil water being immobile and not taking part in the transport process. Domain models have been developed that describe these processes, but before we can apply them routinely, we need methods for measuring the required model parameters, particularly the fraction of immobile water to total water θlm/θ and the exchange coefficient between the mobile and immobile domains, α. We developed a field method for measuring both θlm/θ and α. The method uses a sequence of conservative anionic tracers consisting of Br−, pentafluorobenzoate, o‐trifluoromethylbenzoate, and 2,6‐difluorobenzoate infiltrated with time through a tension infiltrometer. Previous studies have confirmed that these tracers have very similar transport properties in a wide range of soils. The method was applied to an undisturbed loam and a greenhouse soil as an initial test of the approach. Calculated θim/θ fractions averaged 0.69 and ranged from 0.25 to 0.98, while calculated α values averaged 0.0081 h−1 and ranged from 0.0030 to 0.021 h−1. These values compare well with values reported earlier by other investigators. The method is simple and allows routine measurement of transport properties of field soils. The method can also be used to validate the applicability of domain models to specific soils.
Near‐Infrared Analysis as a Rapid Method to Simultaneously Evaluate Several Soil Properties
Authors: Ben‐Dor E. , Banin A. 
Published: July 2010

AbstractThe near infrared analysis (NIRA) approach was studied to examine its capability for predicting spectral feature soil properties from the reflectance curves in the near infrared (NIR) region (1–2.5 µm) of arid and semiarid soils. High‐resolution diffuse reflectance spectra (3113 spectral points) in the NIR region were recorded for 91 soil samples from Israel. Six soil properties (clay content, specific surface area, cation‐exchange capacity, hygroscopic moisture, carbonate content, and organic matter content) were measured by routine methods employed in soil laboratories. An empirical model to predict each property from its spectral signature was developed by adapting the NIRA technique. Several data manipulations were used to obtain optimum performance. The optimum performance of all properties was found to be between 25 and 63 spectral points. Strong support for the NIRA capability was provided by its ability to examine most of the spectral assignments. A slight bias was observed for the prediction of both organic matter and hygroscopic moisture, suggesting that more attention in the prediction of these constituents is required. It was concluded that NIRA is a promising method for rapid and nonrestrictive analysis of soil materials, and further study of the synergism between NIRA and soil materials is recommended.
Hydrologic Tracer Effects on Soil Microbial Activities
Authors: Groffman Peter M. , Gold Arthur J. , Howard Galen 
Published: July 2010

AbstractWhile much research has shown that the commonly used hydrologic tracers Br−, Cl−, and pentafluorobenzoic acid (PFBA) are not affected by soil microbial processes, much less work has gone into analysis of the effects of these tracers on microbial activity. In this study, we analyzed the effects of Br−, Cl−, and PFBA at 100 mg kg−1 concentration on soil respiration, denitrification, N mineralization, and nitrification in a forest soil under laboratory conditions. Chloride and Br− inhibited all activities other than denitrification and PFBA stimulated respiration and denitrification. Mechanisms for the observed effects may be related to the effects of these anion tracers on soil solution cation activities and microbial membrane processes. The results suggest that effects on microbial activities should be considered when tracers are used in studies of the fate and transport of pollutants that are affected by microbial processes.
Slope Class Maps from Soil Survey and Digital Elevation Models
Authors: Hammer R. D. , Young F. J. , Haithcoate T. W. , Wollenhaupt N. C. , Barney T. L. 
Published: July 2010

AbstractSpecial‐purpose land use maps based on slope attributes from digital elevation models (DEMs) often are produced with geographic information system technology. Field verification is lacking for accuracy and precision of computer‐generated slope class maps from 10‐ and 30‐m DEMs, a standard USDA (1:24 000) soil survey, and field‐measured slopes. Two 16‐ha sites in Atchison County, Missouri, were selected, flagged on 10‐m grids, and the slope was field measured for each grid cell. The field‐measured slope class maps were templates for cell‐by‐cell comparisons with the computer‐generated slope classes. More than 50% of the areas were classified into correct slope classes with 10‐m DEM maps. The 30‐m DEM maps were 30 and 21% correctly classified in the two study areas. Two iterations of low‐pass filters increased the accuracy of the 10‐m derived maps, but decreased the accuracy of one 30‐m derived map. Soil survey techniques correctly classified >30% of each area, but did not capture landscape heterogeneity. The GIS‐produced maps underestimated slopes on convexities and overestimated slopes on concavities. Slope class maps from 10‐m DEMs have potential use for soil survey and land use planning.
Methane and Carbon Dioxide Dynamics in a Northern Hardwood Ecosystem
Authors: Yavitt J. B. , Fahey T. J. , Simmons J. A. 
Published: July 2010

AbstractThere is evidence that oxidation of CH4 to CO2 by methanotrophic bacteria in forest soil is a major sink for atmospheric CH4, even though growth of the bacteria on such low CH4 concentrations (<1.7 µL L−1) is perplexing. Measurements of CH4 and CO2 in a northern hardwood ecosystem in the Adirondack Park in the state of New York indicated that: (i) soil CH4 concentrations were mostly higher than the concentration of CH4 in forest air, with concentrations as high as 500 µL L−1 at the 0.1‐m depth in the early and late parts of the growing season; (ii) soil CO2 concentrations ranged from the atmospheric level to as high as 19 000 µL L−1 at the 0.2‐m depth in midsummer; (iii) net consumption of atmospheric CH4 emission by soil in midsummer averaged only 0.25 mg m−2 d−1, which is low compared with findings for most forest ecosystems; and (iv) methanogenesis occurred in soil samples throughout the profile when incubated anaerobically as well as aerobically with CH3F to inhibit methanotrophs. The prominent activity of methanogenic bacteria producing CH4 in the spring and autumn could support the growth of methanotrophic bacteria that otherwise consume atmospheric CH4 when methanogens are not active. Therefore, CH4 dynamics in this Spodosol represent the balance between CH4 production and CH4 oxidation, which is similar to the CH4 dynamics in many wetland ecosystems.
Soil Pedotransfer Functions for Four Mexican Soils
Authors: Bell M. A. , van Keulen H. 
Published: July 2010

AbstractSimulation models for design and testing of different land use management options require detailed soil data inputs, which are often not available. Under such circumstances, pedotransfer functions (PTF) can be used to predict soil properties such as cation‐exchange capacity (CEC) and moisture retention. We developed PTF for CEC and moisture retention at −1500 kPa for soils from four contrasting agro‐ecological environments in Mexico. The PTF relating CEC to clay content, soil organic matter content (SOM), and pH explained 96% of the variability. Analysis of the residuals showed the effects of clay at three sites and SOM at all sites to be similar, despite quite distinct agro‐ecological conditions and a wide range of SOM levels (8.0–40.0 g kg−1). The PTF, using SOM, clay, and pH, explained 93% of the variability across the four sites in moisture retention at −1500 kPa, and residuals showed similar behavior across the sites for both SOM and clay. Additionally, PTF from the literature for CEC and moisture retention at −1500 kPa were tested for the study data and adequate fits were found. Apart from PTF prediction, confidence in model output depends in part on the variability of soil properties at a site. Despite considerable absolute variation in soil properties among sites, the relative variability (i.e., coefficient of variation [CV]) across sites was quite similar, with electrical conductivity and micronutrient concentrations showing the highest CV, and pH, −1500 kPa soil moisture retention, and CEC the lowest; the latter results provided some degree of confidence in the application of PTF. The SOM content was strongly related to altitude and to silt + clay content.
Horizontal Groundwater Flow Patterns Through a Cypress Swamp‐Pine Flatwoods Landscape
Authors: Crownover S. H. , Comerford N. B. , Neary D. G. , Montgomery J. 
Published: July 2010

AbstractGroundwater movement in the surficial aquifer of the lower Coastal Plain cypress swamp‐pine flatwoods landscape of the southeastern USA is poorly documented. This study was conducted to define the patterns of horizontal groundwater flow through a typical landscape with particular attention to water exchange between cypress swamps and the surrounding areas. One hundred and twenty shallow water table wells 1 m deep were installed in a 42‐ha study area, one‐third of which was covered by pond cypress (Taxodium ascendens Brongn.) swamps. Water tables were measured approximately every 2 wk for 2 yr and the data were used to map water table elevation. Directions of horizontal groundwater flow were inferred from the water table topographic maps. Measured hydraulic heads were combined with saturated hydraulic conductivities to estimate groundwater flux. Most of the groundwater flowed through the swamps in response to the generalized surface elevation pattern. For selected ponds, the ground‐water also flowed from the swamps to the surrounding areas. It was uncommon for groundwater to flow into the ponds from the entire surrounding area. The pattern of groundwater exchange between the swamps and the surrounding area was related to the average water table depth: the deeper the average water table, the greater chance for groundwater to flow from the swamp into the surrounding area. Waterflow rates were estimated to be <56 cm d−1. These groundwater flow patterns are different from the generally accepted pattern of water flow and should be useful in defining the hydrologic cycle of these landscapes.
Soil Water Pressure Measurements in Subzero Air Temperatures
Authors: Gorden D. S. , Veneman P. L. M. 
Published: July 2010

AbstractAir temperatures below freezing often preclude soil water pressure measurements with tensiometers. The use of antifreeze solutions facilitates tensiometer use in weather when air temperatures are below 0°C yet the soil remains unfrozen. We studied the applicability of methanol concentrations ranging from 100 to 500 cm3 L−1. Soil water pressures were measured with ceramic cup tensiometers installed at 15‐cm depth within 38‐L‐capacity buckets. Experimental temperatures were ‐2, 0, 5, and 15°C. The pressures ranged from 0 to −60 kPa. Readings of the tensiometer with the methanol‐water mixture were within 0.6 kPa of that of the tensiometer with pure water. No statistically significant difference (α = 0.05) in soil water pressure was found between the methanol‐water mixtures and the pure water system using 1:1 lines and the Wilcoxon signed rank test for paired data. The results indicate that field tensiometer data may be collected in unfrozen soils by the use of the appropriate methanol concentration based on the temperature range expected.
Phenolic Acid Redox Properties: pH Influence on Iron(III) Reduction by Caffeic Acid
Authors: Deiana Salvatore , Gessa Carlo , Marchetti Mauro , Usai Marianna 
Published: July 2010

AbstractPhenolic acids are of great interest to soil chemists because their redox properties affect the availability of micronutrients to plants. In order to provide information about the mechanisms that regulate the reduction of Fe(III) at the soil‐root interface, the redox activity of caffeic acid (CAF) at different pH values in aqueous solution was investigated. The kinetics of the redox reaction was studied by using systems with Fe(III)/CAF molar ratios ranging from 1.1 to 10.9. At pH < 3, all systems showed the highest redox capacity: a maximum of nine electrons for each molecule of CAF was released at a Fe(III)/CAF molar ratio of 10.9. At pH > 3, the redox capacity dramatically decreased and was very low above pH 4. At pH > 4, the reduction of Fe(III) was considerably inhibited due to the formation of Fe(III)‐CAF complexes as well as of Fe(OH)3 precipitates, which are active in the adsorption of CAF. The amount of Fe(II) determined after 24 h of reaction suggests that not only the aquo ion, but also the hydrolized Fe(III)‐soluble species, are active in the oxidation of the organic molecule. At about pH 4, the ultraviolet/visible spectra revealed the presence of Fe(III)‐CAF complexes, which gave rise to the formation of a black polymeric product. The infrared spectra of this product suggest that the CAF molecule interacts with the positively charged hydroxide through the carboxylate groups. The reaction was not influenced by the presence of metal ions such as Cu(II), Ni(II), Mn(II), Fe(II), and Zn(II). We have proposed a mechanism of the reduction and complexation process consistent with our results.
Dynamics of Soil Organic Matter and Corn Residues Affected by Tillage Practices
Authors: Angers D. A. , Voroney R. P. , Côté D. 
Published: July 2010

AbstractThis study was conducted to determine the influence of tillage practices on the decomposition of corn (Zea mays L.) residues and turnover of soil organic matter (SOM). Measurements of δ13C were made of the whole soil, the microbial biomass, and two particle‐size fractions (<50 and >50 µm) in soils that had been under corn production for 11 yr and from an adjacent meadow. Meadow‐derived C in total SOM (0–24 cm) decreased under corn cropping at the same rate under all tillage treatments. Corn‐derived C was evenly distributed with depth in the moldboard plow treatment and accumulated at the surface in the shallow, reduced‐tillage treatments. The incorporation of corn residue C into SOM in the 0‐ to 24‐cm layer was not significantly affected by tillage and was estimated to be ≈41 g C m−2 yr−1, which represents ≈30% of the corn residue inputs. Both the macroorganic matter (>50 µm) and microbial biomass had a greater enrichment (up to 35%) in corn‐derived C than either the whole soil or the microorganic matter (<50 µm), indicating that these pools are important recipients of plant residue inputs. Nevertheless, the microorganic matter was also a significant sink for C input, acounting for ≈50% of the total corn‐derived C remaining in the surface (0–8 cm) soil. Under the conditions of this study, tillage practices influenced the vertical distribution of SOM and corn residues but had no detectable effect on SOM turnover and on the fate of corn residues when the whole Ap horizon was considered.
Bacterial Transport and Phenanthrene Biodegradation in Soil and Aquifer Sand
Authors: Devare Medha , Alexander Martin 
Published: July 2010

AbstractRemediation of contaminated soil by inoculated bacteria requires movement of the bacteria to the site of contamination. Addition of a phenanthrene‐metabolizing Psudomonas sp. to the surface of 1.5‐cm columns of sterile or nonsterile soil or aquifer sand resulted in the rapid mineralization of phenanthrene present in the top 0.4 cm of sand or soil columns receiving intermittent or no water flow. However, the surface‐inoculated pseudomonad mineralized little of the substrate present in the bottom 0.4‐cm portion of nonsterile soil or aquifer sand that had been sterilized prior to inoculation, although mineralization occurred at the bottom of nonsterile aquifer sand. Little biodegradation was evident if the bacterium and the substrate were both at the bottom part of columns of soil and aquifer sand receiving intermittent flows of water, although rapid biodegradation occurred at this site in soil if the water flow was constant. Only ≈1% of the added cells passed through the soil after passage of ≈1.5 pore volumes of water, although ≈4% passed through the aquifer sand. We suggest that bacteria added to the soil surface or to aquifer solids for biodegradation may not be transported sufficiently to reach organic pollutants at sites distant from channels or macropores.
An Apparatus for Application of Nitrogen‐15 Fertilizers Through Buried Drip Tubing
Authors: McGee E. A. , Thompson T. L. , McCreary T. W. 
Published: July 2010

AbstractThis study evaluated a new apparatus for applying 15N by fertigation to subplots under buried drip irrigation. Leaf lettuce (Lactuca sativa L. cv. Waldmann's Green) was planted in one unfertilized buried‐drip‐irrigated plot (4.06 by 53.34 m) with four north‐south beds. Six subplots (1.02 by 2.00 m) were established by placing a 15N injection apparatus into the drip tubing. Nitrogen‐rate treatments (71 and 176 kg ha−1) were replicated three times. Low‐ and high‐N plots received 1.60 and 1.15 atom % 15N urea applied at five times during the season. Plants were harvested at specific positions within and near the subplots. Uniform recovery of 15N by plants within subplots occurred. Uptake of 15N by plants was observed up to 45 cm outside subplots in the north‐south directions and in plants on beds immediately adjacent to the subplots. Uptake outside the subplots in the north‐south directions (apparent lateral movement) was no more than 21% of total 15N uptake.