bluuebunny/crossref_metadata_2025_split huggingface dataset:
Combined Magnetic, Spectroscopic, and Analytical‐Chemical Approach to Infer Genetic Information for a Vertisol
Authors: Gehring A. U. , Guggenberger G. , Zech W. , Luster J. 
Published: July 2010

AbstractA Vertisol from a floodplain in southern Mali was investigated by a combination of magnetic and spectroscopic methods in addition to classical soil chemical and physical analyses. This combined approach allowed us to deduce the genesis of the soil. The Ustic Endoaquert profile extended to a water table at 1.2 m and was subdivided into four horizons, Ap (0–0.1 m), A2 (0.1–0.4 m), A3 (0.4–0.6 m), and Ag (0.6–1.2 m). Redoximorphic features were found at a depth between 0.6 and 0.8 m. Prevailing reducing conditions in the Ag horizon were documented by a maximum concentration of exchangeable Mn(II). High redox dynamics were indicated by minimum concentrations of total and extractable Fe in the A3 horizon as well as by minimum susceptibility and saturation isothermal remanent magnetization in the A3 and Ag horizons. The latter minimum was most likely caused by the reductive dissolution of lithogenic magnetite. Soil organic matter (SOM) was generally characterized by a high amount of aromatic compounds and a high degree of lignin decomposition with maxima in the Ag horizon as indicated by solution and solid‐state 13C nuclear magnetic resonance as well as fluorescence spectroscopies. These characteristics of SOM suggested formation under highly oxidative conditions. The presence of such characteristics, in particular in the lower part of the Vertisol with prevailing reducing conditions, suggests an allochthonous origin of the SOM. Pedoturbation in the upper part of the profile was documented by a higher contribution of primary resources such as lignin, cellulose, and hemicellulose in the Ap and A2 horizons.
Distribution of Mycorrhiza on Competing Pines and Weeds in a Southern Pine Plantation
Authors: Sylvia David M. , Jarstfer Amiel G. 
Published: July 2010

AbstractMycorrhiza are important in the uptake of nutrients by plants, yet little is known about the distribution and function of the diverse fungal symbionts associated with competing plant species. The objective of our research was to investigate effects of weed competition on mycorrhizal development in a slash pine (Pinus elliottii Engelm. var. elliottii) plantation in order to better understand the impact of arbuscular mycorrhizal (AM) weeds on ectomycorrhizal (EM) pines. Seedlings were planted in a typical Spodosol and samples were collected to a depth of 100 cm from weed‐free (herbicide‐treated) and weedy plots in the first and third growing seasons after outplanting. Pine roots were separated from weed roots before samples were assessed for fine root (<3.0‐mm diam.) length, surface area, and mycorrhizal status. Fine root length and surface area, as well as EM surface area, of pine generally decreased with depth and increased between Years 1 and 3. In contrast, fine root length of weedy species was fairly constant during the 3‐yr period. The AM colonization of weeds followed a trend similar to that of fine root development. The depth distribution of EM pine roots and AM weedy roots exhibited complex interactions with treatment, time, and depth. There was generally greater mycorrhizal colonization of both AM on weedy species and EM on pine in the A soil horizon. Weed competition significantly affected the number of EM root tips and the distribution of EM morphotypes. Thelephora was generally the most abundant morphotype, followed by a white, rhizomorph‐producing type (White Rhiz) and Cenococcum. An exception to this pattern was found in the near‐surface soil (0–10 cm) of the weed‐free plots, where White Rhiz was the most frequent morphotype. A challenge for the future is to evaluate the functional significance of changing patterns of EM in the field.
Aggregate Size Effects on the Sorption and Release of Phosphorus in an Ultisol
Authors: Linquist B. A. , Singleton P. W. , Yost R. S. , Cassman K. G. 
Published: July 2010

AbstractDespite extensive research on soil‐P reactions, little is known of the effect of soil aggregation on these processes. This study was conducted to determine the role of aggregate size on the sorption and release of P in a Haiku clay (Typic Palehumult). A range of aggregate sizes up to 4 mm in diameter were used in this study. Autoradiography of sorbed 32P and P sorption studies indicated that added P was initially sorbed to a 0.188‐mm layer around aggregates and remained in this peripheral layer for up to 28 d. We defined this layer as the reactive mass. Analysis of P in aggregates from a 4‐yr P management field experiment on the same soil indicated that diffusion of P from this peripheral layer into the aggregate was slow, requiring >2 yr for aggregate P to reach equilibrium. When P was added to a combined mix of aggregate size fractions, P sorption increased from 55 to 245 mg P kg−1 as mean aggregate diameter decreased from 3.4 to 0.375 mm, and was linearly related to the aggregates' reactive mass (r2 = 0.96). Similarly, the reactive mass of aggregates was linearly correlated to P release from aggregates (r2 = 0.99) and to the linear buffer coefficients derived from P‐sorption isotherms (r2 = 0.98). Since aggregate size is related to P sorption, soil buffering capacity, and P release from soil, it is likely that aggregation affects short‐ and long‐term plant P availability. The effect of aggregate size, however, needs to be investigated for other soils.
Loess Stratigraphy and Fragipan Occurrence in the Lower Mississippi River Valley
Authors: Lindbo D. L. , Rhoton F. E. , Hudnall W. H. , Smeck N. E. , Bigham J. M. 
Published: July 2010

AbstractThe loess uplands adjacent to the Lower Mississippi River Valley (LMRV) are comprised of several different depositional units overlying either coastal plain or alluvial sediments. The occurrence and development of fragipan horizons in the region has been attributed to the presence of a specific stratigraphic unit. This study was conducted to investigate the stratigraphic relationship between loess units throughout the LMRV to determine if the existence of fragipans is limited to one loess deposit. The study utilized five field sites in the loess uplands between northwestern Tennessee and southeastern Louisiana. At all sites, each member of the Memphis catena (Memphis [fine‐silty, mixed, thermic Typic Hapludalf], Loring [fine‐silty, mixed, thermic Typic Fragiudalf], and Grenada [fine‐silty, mixed, thermic Glossic Fragiu‐dalf]) was sampled and preliminary stratigraphic breaks identified by changes in texture and color. These breaks were further refined in the laboratory by characterizing each horizon for clay‐free particle‐size distribution and mass magnetic susceptibility. Additionally, total Fe, K, Mg, Ca, Ti, and Zr were determined for the coarse silts (20–50 µm) from all Memphis horizons. The data were further evaluated by κ‐means cluster analysis to refine stratigraphic breaks in the loess and underlying coastal plain or alluvial deposits. Generally, stratigraphic breaks were distinguishable by changes in clay‐free sand, clay‐free medium and coarse silt, and mass magnetic susceptibility. Secondary clay maxima below 250 cm represented paleoargillic horizons that confirmed stratigraphic changes and buried surfaces. For the thick loess deposits (>3.5 m total loess thickness), fragipans developed entirely in Peoria Loess, but in thinner loess deposits (<3.5 m total loess thickness) fragipans crossed stratigraphic boundaries between Peoria Loess and underlying units. Thus, the development of fragipan horizons in these loess soils is independent of stratigraphic units.
Soil Aggregation and Fungal and Bacterial Biomass under Annual and Perennial Cropping Systems
Authors: Chantigny Martin H. , Angers Denis A. , Prévost Danielle , Vézina Louis‐P. , Chalifour François‐P. 
Published: July 2010

AbstractUnderstanding the mechanisms controlling crop effects on soil aggregation is necessary to develop sustainable soil management practices. Changes in soil aggregation, carbohydrates, and fungal vs. bacterial biomass were monitored following a shift from fallow (bare soil) to various cropping systems. Faba bean (Vicia faba L.) and wheat (Triticum aestivum L.) were used as annual cropping systems, while alfalfa (Medicago sativa L.), timothy (Phleum pratense L.), bromegrass (Bromus inermis L.), and reed canarygrass (Phalaris arundinacea L.) were used as perennial cropping systems. Crops were established in spring 1989, on a silty clay loam (fine, mixed, frigid Typic Dystro‐chrept) and a clay loam (fine‐loamy, mixed, frigid Typic Humaquept) near Québec City (Canada). After three growing seasons, the mean‐weight diameter of water‐stable aggregates (MWD) was higher under reed canarygrass (2.26 mm in the clay loam and 2.45 mm in the silty clay loam) and timothy (2.13 and 2.26 mm) than under faba bean (1.92 and 1.89 mm) or wheat (2.06 and 1.57 mm). Intermediate values were found under alfalfa and bromegrass. Changes in MWD were not correlated with microbial biomass C. Acid‐hydrolyzable carbohydrates correlated with MWD in the silty clay loam (r2 = 0.42**) but the relationship decreased with higher carbohydrate levels in the clay loam (r2 = 0.05). Close correlations were found between MWD and both fungal glucosamine (r2 = 0.68***, soils combined) and bacterial muramic acid (r2 = 0.48***). Changes in MWD were mostly reflected in aggregates >2 mm, and the close relationship with fungal glucosamine suggests that fungi played a dominant role in soil macroaggregation. Measurement of muramic acid and glucosamine is proposed as a potential approach to compare bacterial vs. fungal contributions to soil aggregation.
The Pattern of Soil Variables Related to Artemisia tridentata in a Burned Shrub‐Steppe Site
Authors: Halvorson Jonathan J. , Bolton, Harvey , Smith Jeffrey L. 
Published: July 2010

AbstractArtemisia tridentata Nutt. is a prominent shrub of cool deserts in the USA that influences the patterns of chemistry and microbiological activity in the soil in which it grows. However, little is known about the fate of these patterns following the death or removal of the live A. tridentata plant. We compared abutting burned and unburned sites to see if patterns in soil could be related to locations where shrubs were removed by fire 9 yr earlier. While most soil variables were significantly higher in the unburned site than in the burned site, total organic C and soil pH appear unaffected by the removal of A. tridentata or the fire itself. Differences between unburned and burned sites were greatest near the location of a plant axis. In contrast, burned soil was not distinguishable from unburned soil at distances greater than ≈ 50 cm away from a live A. tridentata axis or a charred stump indicating that soil patterns were most affected by removal of the plant and not by the fire. Nearly a decade after the fire, significant effects of A. tridentata on patterns of some soil variables in the burned site were still detectable. Significantly higher values for total organic C, total N, water soluble C, electrical conductivity, and soil microbial biomass C were observed near the location of charred A. tridentata stumps than at distances further away. These patterns are a significant source of soil variability that may be difficult to account for because they are not related to the obvious location of live plants.
Effect of Storage and Sieving on the Phosphorus Composition of Soil Solution
Authors: Chapman P.J. , Shand C. A. , Edwards A. C. , Smith S. 
Published: July 2010

AbstractIn this study, the effects of storage and sieving of a mineral soil (Typic Fragiorthod) on the P chemistry of the soil solution have been quantified. Intact and sieved soil cores were stored for 0, 1, 3, and 8 d at 4°C prior to obtaining solutions, which were analyzed for total dissolved phosphorus (TDP), molybdate‐reactive phosphorus (MRP), dissolved organic phosphorus (DOP), and dissolved condensed phosphorus (DCP). Storage of both sieved and intact soil cores influenced the amount and chemical composition of P in solution. Concentrations of TDP, MRP, and DOP displayed a rapid decline with increase in storage time, whereas DCP concentrations, which were initially very low, increased. Concentrations of TDP were significantly (P < 0.05) different between solutions extracted from intact and sieved soils on the same day as sampling and this was accounted for by DOP and MRP, which were significantly (P < 0.05) larger in sieved soil. The proportions of MRP, DOP, and DCP were similar in solutions extracted from intact and sieved soils on the same day, even for Day 0 where a large difference in TDP was apparent. The MRP fraction was consistently larger for intact cores (44%) than sieved (38%) on all days and varied little with length of storage. The DOP component, which dominated initially, decreased with increase in storage time, while DCP increased to become the major fraction after 8 d of storage. This study has highlighted the potential effects of soil storage and sieving on the P concentration and composition of soil solution. The results also have important implications for soil solution sampling and subsequent data interpretation.
Impact of Funnel Flow on Contaminant Transport in Sandy Soils: Numerical Simulation
Authors: Ju S.‐H. , Kung K.‐J. S. 
Published: July 2010

AbstractAgrichemicals have played an essential role in maintaining the productivity of arable lands in modern agriculture. Recently, it was found that preferential flow could greatly enhance the leaching of agrichemicals into groundwater. This study investigated how contaminant transport would be influenced by funnel‐type preferential flow paths in a sandy vadose zone. Numerical simulations were conducted in four 12‐m‐wide by 6‐m‐deep two‐dimensional hypothetical soil profiles with embedded coarse sand layers. The soil layering structures in these profiles were generated according to what was observed in the vadose zone of a Plainfield sand (sandy, mixed, mesic Typic Udipsamment) in central Wisconsin. Corresponding simulations were conducted in one‐dimensional profiles as controls. Results showed that contaminant breakthrough time in the two‐dimensional profiles was only 25% of that in one‐dimensional homogeneous profiles. The ratio of the total mass leached from the two‐dimensional profile to that from the one‐dimensional profile increased exponentially as the water application rate decreased. This implies that: (i) the impact of funnel flow on contaminant transport is most drastic when the net infiltration is low; and (ii) minimizing excess leaching by carefully controlling the water budget alone might not prevent groundwater contamination. For a pesticide with a degradation coefficient of 3 × 10−7 s−1 and an adsorption coefficient of 0.5 cm3 g−1 in the top 30 cm and 0.05 cm3 g−1 from 30 to 600 cm, about 4% of the total mass would reach the groundwater through two‐dimensional funnel flow paths with an averaged daily net infiltration rate of 1.15 mm d−1.
Geochemical Characteristics of a Loess‐Soil Sequence in Central Kansas
Authors: Feng Zhao‐Dong 
Published: July 2010

AbstractThis study focuses on a Barton County loess‐soil section in central Kansas in an attempt to retrieve the geochemical signature of the late Quaternary environmental change in the arid‐semiarid region and provide a data base of loess geochemical characteristics in the Great Plains. The data indicate that the elements (expressed as oxides) of the windborne fraction (<63 µm) that are easily solubilized and lost from the soil by chemical weathering and leaching are relatively sensitive to soil‐forming processes, whereas the insoluble elements of that fraction are controlled primarily by the chemical composition of the parent material. The geochemical imprint of pedogenesis superimposed on that of the loess parent material can be distinguished by comparing the magnetic susceptibility signature with the Fe2O3/Al2O3 ratio. Based on the geochemical imprint and radiometric dates (14C and thermoluminescence), the Bignell Loess (8000–5000 yr) is poorly weathered and the Brady Soil (10 000–8000 yr) is strongly weathered. The Peoria Loess (20 000–10 000 yr) has neither a traceable leaching nor weathering marker, and the Gilman Canyon pedocomplex (35 000–20 000 yr) is strongly leached. The reddish pedocomplex (70 000–35 000 yr) is the most strongly weathered, probably due to stable land surface conditions in a mild climate, and the Barton sand (92 000–70 000 yr) seems to have been subjected to a moderate weathering. Within the exposed portion of the Loveland Loess (260 000–92 000 yr), weathering indices are inversely correlated with the carbonate content and the carbonate‐rich soils were developed under warm dry environments before 92 000, around 193 000, and before 260 000 yr. The data also show that the geochemical background of Fe2O3 and Al2O3 is high in two portions of the section: from the Brady Soil to the Gilman Canyon pedocomplex and from LL1 to LL2 within the Loveland Loess. The geochemical background of Fe2O3 and Al2O3 in the loess‐soil sequence might have been dictated by that of eolian sources.
Cradle‐Knoll Patterns and Characteristics on Drumlins in Northeastern Wisconsin
Authors: Kabrick J. M. , Clayton M. K. , McSweeney K. , McBratney A. B. 
Published: July 2010

AbstractCradle‐knoll microtopography has been shown to influence soil and vegetation. However, the scale of commonly used topographic maps is too coarse for representation of microtopography. The objectives of this study were to investigate the influence of cradle‐knoll microtopography on the distribution of trees, to develop a method to quantify the spatial patterns and characteristics of cradle‐knolls, and to test for pattern similarity of cradle‐knolls within and among drumlins in the Nicolet National Forest, Wisconsin. Six drumlins were selected for study. Tree species, tree diameter, and microsite location (e.g., cradle, knoll, or neither) within which each tree was found were inventoried in three, 10‐m‐radius plots across each drumlin. The spatial location, length, width, relief, and orientation of 220 cradle‐knolls were inventoried along 200‐m transects using a T‐square sampling technique on summit and backslope positions of each drumlin. Sixty percent of the trees inventoried were growing on knolls and only 2% were growing in cradles. The same number of knolls and cradles occurred among drumlins and among backslopes and summits within drumlins. Cradle‐knoll relief differed among drumlins, and knoll relief is greater on backslopes than on summits within drumlins. Cradle‐knoll orientation differed among slope positions. These findings suggest that treethrow rates and the size of the uprooted trees are roughly the same among and within drumlins. Differences in relief among drumlins are probably an indication of how recently treethrow has occurred. Greater relief of knolls among backslopes and summits is probably because of slope‐mediated differences in cradle‐knoll formation. Slope position also affects cradle‐knoll orientation in these landscapes.
Mineralogical and Physicochemical Differences between Mobile and Nonmobile Colloidal Phases in Reconstructed Pedons
Authors: Kaplan Daniel I. , Bertsch Paul M. , Adriano Domy C. 
Published: July 2010

AbstractUltisols can be highly dispersive and therefore a potential source for mobile colloids to underlying aquifers. In this study, mobile colloids were collected after a rain from 13.5‐m3 lysimeters containing reconstructed pedons of two Ultisols. The mobile colloids were enriched with kaolinite, Fe oxides, and gibbsite and were more dilute in quartz and hydroxy‐interlayered vermiculite (HIV) relative to the total clay fractions of the originating pedons. The colloids were <1000 nm in diameter and had a bimodal size distribution: the larger colloids (≈760 nm) consisted primarily of quartz and HIV; the much more abundant smaller colloids (≈230 nm) consisted primarily of Fe oxides, kaolinite, and gibbsite. The colloids also had exceptionally high negative surface charges that probably originated from organic coatings (10 g kg−1). These organic coatings indicate that the majority of the colloids originated from the surface horizon, the only horizons with measurable amounts of organic C. Soil minerals most likely to enter the mobile phase (Fe oxides, gibbsite, and kaolinite) were readily dispersible and in the <200‐nm fraction. The HIV in the reconstructed pedons was readily dispersible but because of its relatively large size (>200 nm), it was removed from the mobile phase during transport, presumably via a straining mechanism. Quartz was neither readily dispersible nor abundant in the <200‐nm fraction and, therefore, was not prevalent in the mobile phase. The ability of Ultisols to release colloids that can readily move through a pedon may make these soils and the underlying aquifers especially susceptible to colloid‐facilitated transport of contaminants.
Modeling Structural Influences on Soil Water Retention
Authors: Nimmo John R. 
Published: July 2010

AbstractA new model quantifies the effect of soil structure, considered as the arrangement of particles in the soil, on soil water retention. The model partitions the pore space into texture‐related and structure‐related components, the textural component being what can be deduced to exist if the arrangement of the particles were random, and the structural component being the remainder. An existing model, based on particle‐size distributions, represents the textural component, and a new model, based on aggregate‐size distributions, represents the structural component. This new model makes use of generalized properties that vary little from one medium to another, thereby eliminating any need for empirically fitted parameters. It postulates a particular character of the structural pore space that in some ways resembles texture‐related pore space, but with pore shape related to the breadth of the aggregate‐size distribution. To predict a soil water retention curve, this model requires the soil's porosity and particle‐ and aggregate‐size distributions. Tested with measurements for 17 samples from two sources, it fits the data much better than does a model based on texture alone. Goodness of fit indicated by correlation coefficients ranged from 0.908 to 0.998 for the new model, compared with a range of 0.686 to 0.955 for the texture‐based model.