bluuebunny/crossref_metadata_2025_split huggingface dataset:
Relationship between the isotopically exchangeable and resin‐extractable phosphate of deficient to heavily fertilized soil
Authors: Schneider A. , Morel C. 
Published: March 2003

SummaryThe rate and extent of soil–solution transfer of orthophosphate ions (Pi) depend both on soil solution Pi concentration and on time. This is so both in experiments on sorption–desorption and in those on isotopic exchange. Because the two methods are based on different principles, it is questionable whether they give a similar quantification of Pi transfer.The amount of isotopically exchangeable Pi, E, was determined over periods of 100 minutes and described as a function of both time and Pi concentration in solution for three soil samples taken from field plots having different P fertilizer histories over 26 years of annual application. In separate experiments, amounts of Pi, Qd, were extracted from soil suspensions using three levels of anion exchange resin strips for periods ranging from 10 minutes to 7 days. Both initial and final solution Pi concentrations were measured. These concentrations and periods of resin‐contact were used to predict the difference in E, ΔE, between the initial and final states of the suspension–resin system using extrapolations of the equations fitted to the exchange data. Under conditions in which the solution concentration of Pi decreased during extraction the ΔE values and the resin‐extracted Pi values, Qd, were equal. It is thus possible, using the description of E, to predict the amount of Pi released from soil suspension knowing the initial and final solution Pi concentrations and the time it took for the system to pass from the initial to the final state. For the soil studied, identical amounts of mobile Pi, i.e. the Pi which participates in the soil–solution dynamics, may therefore be assessed by either isotopic exchange or desorption.
The effect of organic acids on base cation leaching from the forest floor under six North American tree species
Authors: Dijkstra F. A. , Geibe C. , Holmström S. , Lundström U. S. , Van Breemen N. 
Published: March 2003

SummaryOrganic acidity and its degree of neutralization in the forest floor can have large consequences for base cation leaching under different tree species. We investigated the effect of organic acids on base cation leaching from the forest floor under six common North American tree species. Forest floor samples were analysed for exchangeable cations and forest floor solutions for cations, anions, simple organic acids and acidic properties. Citric and lactic acid were the most common of the acids under all species. Malonic acid was found mainly under Tsuga canadensis (hemlock) and Fagus grandifolia (beech). The organic acids were positively correlated with dissolved organic carbon and contributed significantly to the organic acidity of the solution (up to 26%). Forest floor solutions under Tsuga canadensis contained the most dissolved C and the most weak acidity among the six tree species. Under Tsuga canadensis we also found significant amounts of strong acidity caused by deposition of sulphuric acid from the atmosphere and by strong organic acids. Base cation exchange was the most important mechanism by which acidity was neutralized. Organic acids in solution from Tsuga canadensis, Fagus grandifolia, Acer rubrum (red maple) and Quercus rubra (red oak) were hardly neutralized while much more organic acidity was neutralized for Acer saccharum (sugar maple) and Fraxinus americana (white ash). We conclude that quantity, nature and degree of neutralization of organic acids differ among the different tree species. While the potential for base cation leaching with organic acids from the forest floor is greatest under Tsuga canadensis, actual leaching with organic anions is greatest under Acer saccharum and Fraxinus americana under which the forest floor contains more exchangeable cations than does the strongly acidified forest floor under Tsuga canadensis.
Isotopic fractionation of dissolved organic carbon in shallow forest soils as affected by sorption
Authors: Kaiser K. , Guggenberger G. , Zech W. 
Published: March 2003

SummaryIsotopic fractionation of dissolved organic carbon percolating through the soil is often interpreted as due to microbial transformation. We investigated the potential effects of sorption on the δ13C of dissolved organic C in field and laboratory experiments. We sampled the organic C in soil water at two forested sites and measured sorption with intact mineral soil and individual minerals (dolomite, ferrihydrite, goethite, and quartz). The dissolved organic C was separated into hydrophilic and hydrophobic fractions using a resin approach. The δ13C values of bulk soils, alkaline‐extractable organic C, and dissolved organic C and its fractions were measured. Hydrophilic and hydrophobic fractions in forest floor seepage water were characterized by13C‐NMR spectroscopy.At both sites, δ13C of dissolved organic C increased with increasing depth, suggesting that decomposition contributes to the loss of the dissolved organic C. However, there was an enrichment of hydrophilic organic C in the soil solution as the water moved down the soil. The δ13C values of hydrophilic fractions were less negative than those of hydrophobic fractions. The smaller δ13C in the hydrophobic fraction was due to the large contribution of compounds derived from lignin that are depleted in13C. As the isotope composition of both fractions of dissolved organic C did not change throughout the profile, changes in δ13C of total organic C reflected changes in the relative proportions of its hydrophilic and hydrophobic fractions. The sorption experiments with minerals and soil cores gave similar results. When dissolved organic C came into contact with mineral material, the δ13C of that remaining in solution increased due to preferential sorption of the13C‐depleted hydrophobic fractions. Moreover, the soils released hydrophilic organic C with large δ13C values, increasing the δ13C of organic C in effluents from soil compared with that in the inflow. Thus, selective sorption of organic C fractions changes δ13C in a way that mimics metabolic transformation and decomposition.
Pedotransfer functions for solute transport parameters of Portuguese soils
Authors: Gonc˛alves M. C. , Leij F. J. , Schaap M. G. 
Published: March 2003

SummaryThe purpose of this study is to quantify solute transport parameters of fine‐textured soils in an irrigation district in southern Portugal and to investigate their prediction from basic soil properties and unsaturated hydraulic parameters. Solute displacement experiments were carried out on 24 undisturbed soil samples by applying a 0.05 mKCl pulse during steady flow. The chloride breakthrough curves (BTCs) were asymmetric, with early breakthrough and considerable tailing characteristic of non‐equilibrium transport. The retardation factor (R), dispersion coefficient (D), partitioning coefficient (β), and mass transfer coefficient (ω) were estimated by optimizing the solution of the non‐equilibrium convection–dispersion equation (CDE) to the breakthrough data. The solution could adequately describe the observed data as proved by a median of 0.972 for the coefficient of determination (r2) and a median for the mean squared error (MSE) of 5.1 × 10−6. The median value forRof 0.587 suggests that Cl–was excluded from a substantial part of the liquid phase. The value forβwas typically less than 0.5, but the non‐equilibrium effects were mitigated by a large mass transfer coefficient (ω > 1). Pedotransfer functions (PTFs) were developed with regression and neural network analyses to predictR,D,βandωfrom basic soil properties and unsaturated hydraulic parameters. Fairly accurate predictions could be obtained for logD(r2 ≈ 0.9) andβ(r2 ≈ 0.8). Prediction forR andlogωwere relatively poor (r2 ≈ 0.5). The artificial neural networks were all somewhat more accurate than the regression equations. The networks are also more suitable for predicting transport parameters because they require only three input variables, whereas the regression equations contain many predictor variables.
Modelling competitive anion adsorption on oxide minerals and an allophane‐containing soil
Authors: Gustafsson J. P. 
Published: March 2003

SummaryCan surface complexation constants for anions, drawn from the literature for reference oxides, be combined to describe competitive adsorption in a spodic B horizon sample containing the important adsorbent minerals proto‐imogolite allophane and ferrihydrite? To answer this and to derive complexation constants for the corresponding reference oxides, a CD‐MUSIC model was used, with arsenate as the sorbing ion. To minimize the interference from competing organic substances, a sample containing little organic matter was used. To describe the adsorption of added arsenate correctly, it was found that competitive interactions from sulphate, silicic acid and phosphate had to be considered. In the model, the specific surface area of singly coordinated AlOH groups of allophane, the sulphate surface complexation constant on allophane, and the total concentration of reactive silicic acid were fitted. All other parameters were fixed using reference oxide values. The results indicated that arsenate, phosphate and silicic acid formed stronger surface complexes on ferrihydrite than on gibbsite or allophane, whereas the reverse was true for sulphate. I conclude that the approach used should provide significant qualitative information on the competitive adsorptive interactions in soils. However, the approach may be impractical for routine simulations and predictions. This is partly due to the uncertainty of the assumption that the properties of allophane and ferrihydrite in real soils can be approximated by those of gibbsite and ferrihydrite synthesized in the laboratory. Another difficulty is that the adsorption of arsenate and phosphate might not reach equilibrium within the limited time of most experiments.
Shrinkage and drainage in aggregates of volcanic soils: a new approach combining mercury porosimetry and vacuum drying kinetics
Authors: Poulenard J. , Bartoli F. , Burtin G. 
Published: March 2003

SummaryThe topsoils of Andisols in the wet high altitude grasslands (páramos) of Ecuador have shrunk after recent changes from permanent grassland to agriculture. The question arises as to whether all Andisols in the region behave in the same way. We have therefore studied the shrinkage on drying of topsoils from four representative types of Andisol in the páramos using a combination of drying kinetics and mercury porosimetry. We aimed to identify and quantify the pore volumes that participate in either drainage or shrinkage or both. The key concept of hierarchical dual porosity of soils used to interpret the shrinkage curves was partly validated, but we also identified more complex relations between drainage, shrinkage and structure. We found that the older was the soil, the more weathered it was, and, consequently, the greater its aggregation and porosity. In turn, the total volumetric shrinkage was controlled by the initial void ratio of the wet soil samples. Our results also show that the solid–pore interfaces of the volcanic soil aggregates were less accessible after shrinkage than before.
Evaluation of ferrolysis in soil formation
Authors: Van Ranst E. , De Coninck F. 
Published: March 2003

SummaryThe concept of ferrolysis as defined in the 1970s by Brinkman and co‐workers is mentioned in the recent literature as a dominant process to explain clay disintegration, interlayering of clay minerals, and strong texture contrast of duplex soils, in which bleaching and mottling are predominant features. Ferrolysis is based on biochemical reduction of free iron(III) oxides to Fe2+ and re‐oxidation of Fe2+ during alternating reducing and oxidizing conditions in the soil. The acidity produced during the oxidation is assumed to release cations from silicates which results in the destruction of clay minerals. A detailed analysis of data from chemical analyses, laboratory experiments, and mineralogical and micromorphological investigations, which have been considered to sustain the ferrolysis theory, has been carried out. Some soils in Belgium and France, which have been considered to be formed mainly by ferrolysis, show strong textural contrast or albeluvic features. It has been shown that the development of these soils is due to clay translocation rather than to clay destruction by ferrolysis. Fine quartz and chlorite, assumed to be secondary minerals formed during ferrolysis, are more likely formed by disintegration of larger quartz and chlorite particles.
Edaphic and physiographic factors affecting the distribution of natural gamma‐emitting radionuclides in the soils of the Arnás catchment in the Central Spanish Pyrenees
Authors: Navas A. , Soto J. , Machín J. 
Published: March 2003

SummaryGamma‐emitting radionuclides are a natural source of radiation that can be a concern for human health, therefore it is important to know the radionuclide backgrounds in soils and to assess their mobility and transfer in ecosystems. Concentrations of natural radionuclides were determined in soils from a small catchment in the middle mountain environment of the Central Spanish Pyrenees. Radioisotope activities were well within the natural ranges for soil, averaging 27, 26, 32 and 500 Bq kg−1 for 238U, 226Ra, 208Tl and 40K, respectively. Their distributions in the soil profile were analysed along three transects of contrasting physiography and soil type. Uranium was depleted in upper layers of the soil and slightly enriched in deeper sections, while 226Ra, 40K and 208Tl were more uniformly distributed. Radionuclide activities in the Calcaric Regosols on the shrub slope were less than those in the deeper and better developed Haplic Kastanozems under forest and in Calcaric Fluvisols in the valley bottom. These spatial patterns seem to be affected by the soil type; other landscape features, such as slope orientation and vegetation cover, appeared to have an indirect effect. The results indicate that the depth distribution of the radionuclides is affected by some soil properties, including pH, carbonates, organic matter and particle size, and soil processes, such as leaching and adsorption.
Stabilization of carbon from maize in a sandy soil in a long‐term experiment
Authors: Ludwig B. , John B. , Ellerbrock R. , Kaiser M. , Flessa H. 
Published: March 2003

SummaryThe sequestration of carbon (C) in soil is not completely understood, and quantitative information about the amounts of organic carbon in the various fractions and their rates of turnover could improve understanding. We aimed (i) to quantify the amounts of C derived from maize at various depths in the soil in a long‐term field experiment with and without fertilization using 13C/12C analysis, (ii) to model changes in the organic C, and (iii) to compare measured and modelled pools of C. The organic C derived from the maize was measured in soil samples collected to a depth of 65 cm from four plots, two of which had been under continuous maize and two under continuous rye during long‐term field experiments with NPK and without fertilization. The fractionation procedures included particle‐size fractionation and extractions in water and in pyrophosphate solution. We used the Rothamsted Carbon Model to model the dynamics of the carbon from 13C data. The amounts of C derived from maize in the Ap horizon after 39 years of continuous maize cropping were 9.5% of the total organic C (where unfertilized) and 14.0% where NPK had been applied. Fertilization did not affect the residence time of carbon in the soil. The amounts of C derived from maize in water extracts were 21% of the total organic C (where unfertilized) and 22% where NPK had been applied. The extracts that were soluble in pyrophosphate and insoluble in acid were depleted in C from maize (the amounts were 5% and 7% of the total organic C, respectively). The results of the 13C natural abundance technique were used to model the dynamics of the organic C. Both the total organic C and the C derived from maize in the particle‐size fraction 0–63 μm agreed well with the total and maize‐derived sums of the model pools ‘inert organic matter’, ‘humified organic matter’ and ‘microbial biomass’. The model suggested that 64% (unfertilized) or 53% (NPK) of the organic C in the Ap horizon were inert. Only one of three published equations to determine the size of the inert pool agreed well with these model results.
A comparison of three methods for estimating substrate coarseness in rivers
Authors: GIBSON R. J. , HILLIER K. G. , WHALEN R. R. 
Published: March 2003

AbstractThree methods were used to estimate coarseness of substrate within experimental stations in four Newfoundland rivers: (1) a categorical rating was derived by estimating proportions of types of all the substrate within an area; (2) a similar type of rating was derived, but from substrate types within 30 cm sections delineated on a lead rope stretched across the station; and (3) an index of coarseness of the substrate was measured from a depth sampler constructed of 11 sliding rods supported within a 1 m long frame. The rod, or depth, sampler was considered to provide the least subjective method and could therefore provide an index to validate the other methods. Compared with the standard deviations of depths for the rod sampler, the categorical ratings from the general estimate had an rs= 0.85, and the 30 cm sampler an rs= 0.86. It was deduced that the two methods of visually estimating substrate types in shallow clear rivers are reasonably adequate methods for describing coarseness, but that the depth sampler would be the more precise under certain conditions.
Stock size fluctuations in chub mackerel (Scomber japonicus) in the East China Sea and the Japan/East Sea
Authors: Hiyama Yoshiaki , Yoda Mari , Ohshimo Seiji 
Published: March 2003

AbstractThe stock size of chub mackerel (Scomber japonicus) in the East China Sea and the Japan/East Sea has shown a continuous decrease, with fluctuations, from 1975 to 1990. After a remarkable increase in 1992–96, the stock size fell to its lowest level in 1997–99. The spawning success (number of recruits/spawning biomass) fluctuates periodically with a period of several years, although there are no clear relationships between the spawning biomass and the number of recruits. Spawning success was inversely correlated with sea surface temperature (SST). On the contrary, the catch amount and the catch per unit effort (CPUE) of spotted mackerel (Scomber australasicus) has increased since 1997.
Empirical biomass model for the Japanese sardine, Sardinops melanostictus, with sea surface temperature in the Kuroshio Extension
Authors: Noto Masayuki , Yasuda Ichiro 
Published: March 2003

AbstractAn Empirical Biomass Model for the Japanese sardine, Sardinops melanostictus, was developed on the basis of the relationship between February sea surface temperature (SST) in the Kuroshio Extension (30–35°N, 145–180°E) and the mortality coefficient during the period from egg to age 1, observed in 1979–94, to examine the long‐term variation of biomass. The periods of the good and bad catch, the year of the biomass peak, and the speed of the biomass decline in the period from 1957 to 1994 were successfully reproduced, except for the biomass increase in the early 1970s. When the model also included with a density‐dependent effect, the whole history of the observed catch during 1957–94 was almost perfectly reproduced. These results suggest that the environment in the Kuroshio Extension region, represented by winter–spring SST, is regarded as a leading factor for determining fluctuations of the sardine biomass in the long term, and that the density effect has a secondary contribution.
Predator–prey interactions between larval damselflies and mining larvae of Glyptotendipes gripekoveni (Chironomidae): reduction in feeding activity as an induced defence
Authors: Koperski Pawel 
Published: March 2003

1. The feeding methods and intensity of predation by larvae of the damselfly Erythromma najas on leaf‐mining larvae of the chironomid Glyptotendipes gripekoveni were examined in artificial habitats differing in complexity. The experiments assessed the influence of chemical stimuli from the predator, light and the concentration of suspended food on the feeding activity of G. gripekoveni inside and outside of the mine.2. Erythromma najas preyed upon G. gripekoveni as the latter grazed outside mines. The intensity of this predation decreased significantly at night in a habitat offering alternative prey.3. When the food concentration for the chironomid was high, it significantly reduced both filtering activity and activity outside mines in response to the kairomone produced by E. najas. Feeding activity did not change when food was scarce.4. The induced reduction in filter‐feeding and deposit‐feeding activity probably reduced predator success by reducing the probability of long‐distance detection of a mine and location of the chironomid’s hole.5. The predator can detect and catch mining prey in either the light (visually) or dark (mechanically). This may explain the lack of diel periodicity in the chemically induced differences in prey activity.6. Reduced feeding activity of mining larvae in the chemically simulated presence of a larval damselfly can be explained as an induced antipredator behaviour, illustrating the trade‐off between feeding demands and predation risk in a poorly known link of the littoral foodweb.
Breakdown of	Ficusand	Eucalyptusleaves in an organically polluted river in India: fungal diversity and ecological functions
Authors: Raviraja  , Sridhar  , Bärlocher Felix 
Published: March 2003

1. At two organically polluted sites in the River Nethravathi, banyan and eucalypt leaves were colonized by one or two species of aquatic hyphomycetes. A total of three or four species were identified at the two sites in samples of water and naturally occurring leaves.2. Spore production from stream‐exposed leaves by aquatic hyphomycetes was lower by a factor of up to 1 million compared with an earlier study in geographically close but unpolluted streams.3. Exponential decay rates and loss rates of phosphorus and calcium, were not statistically different from an earlier study in unpolluted streams. Nitrogen increased during decomposition more slowly in the current study.4. The microbial community on both leaves released enzymes active against starch, pectin, cellulose and xylan.5. Banyan leaves conditioned for 12 weeks were more palatable to the gastropod Notopala sp. than unconditioned leaves.6. Together with earlier data from unpolluted streams, the study provides evidence that organic pollution severely restricts diversity of aquatic hyphomycetes and their reproductive output, but does not have an equally strong effect on ecological functions generally associated with this group.