bluuebunny/crossref_metadata_2025 huggingface dataset:
Immunoprecipitation and isoelectric focusing of sheep MHC class I antigens reveal higher complexity than serology
Authors: Jugo B. M. , Joosten I. , Grosfeld‐Stulemeyer M. , Amorena B. , Hensen E. J.
Published: March 2003

Biochemical and serological methods were used to characterize sheep MHC class I polymorphism at the product level. The cells of 65 selected animals were subjected to immunoprecipitation and one‐dimensional isoelectric focusing (IEF) with two cross‐reacting monoclonal antibodies, B1.1G6 and HC‐10. We were able to define up to 18 distinct haplotypes in the Latxa breed sample. Most of the locally defined serological specificities were confirmed or subdivided by biochemical typing. As IEF detected antigens not yet defined by serology, it provided us with a guide to producing more specific antisera by appropriate immunizations. Lastly, evidence of expression of two class I loci products was found.
Definition of permissible and immunogenic HLA antigens based on epitope analysis of the HLA specific antibodies produced in sensitized patients
Authors: Papassavas A. C. , Stavropoulos‐Giokas C. , Boletis J. , Ioannou S. , Iniotaki‐Theodoraki A. , Kostakis A.
Published: March 2003

The goal of this study was to develop an accurate protocol whereby detection of acceptable HLA‐A and ‐B mismatches is based on epitope analysis of HLA class I specific antibodies detected in the serum of highly sensitized patients awaiting a kidney retransplant. A total of 400 serum samples from 44 highly sensitized patients with panel reactive antibodies (PRA) of ≥ 60% were collected during a 3‐year follow‐up period. All patients had been sensitized from a previous graft. In order to define the specificities of the HLA class I specific antibodies, two techniques were used in parallel: the antihuman globulin augmented complement‐dependent cytotoxicity (CDC) technique and an enzyme‐linked immunoabsorbent assay (ELISA) technique. Epitope identification was based on class I HLA antigen sequencing, where the unique epitope configuration on one HLA antigen represented the private epitope of the specific HLA antigen, and epitopes shared by more than one HLA antigen represented public determinants. The epitope prediction for the immunogenic HLA epitopes was based on an MHC database. For each highly sensitized patient, antibody specificities against actual and ‘at risk’ epitopes were defined. Following epitope analysis, all HLA antigens that did not express the actual and/or ‘at risk’ immunogenic epitopes were considered as acceptable mismatches of epitope analysis. The cytotoxicity of highly sensitized patients was determined using two different panels of selected, separated T lymphocytes. HLA class I specific IgG antibodies against 69 actual and 86 ‘at risk’ epitopes were detected. In all patients, a large number of acceptable mismatches were defined. These included a large number of HLA antigens, corresponding to both HLA‐A and ‐B loci. Our study introduces an accurate protocol for the detection of acceptable mismatches in highly sensitized patients. According to this protocol, the detailed description of immunogenic HLA specific epitope targets, against which HLA class I specific antibodies are directed, is a useful tool for the detection of acceptable mismatches in highly sensitized patients. This may lead to reduced production of HLA class I specific antibodies and, consequently, improved graft survival.
Surface morphology of quartz grains from tropical soils and its significance for assessing soil weathering
Authors: Marcelino V. , Mussche G. , Stoops G.
Published: March 2003

The surface morphology of quartz grains can indicate the degree of weathering of soil material. We have compared two methods of assessing the relative weathering of soils on the basis of differences in the surface morphology of quartz sand grains in a catena of soils in Rwanda. One method is based on the presence or absence of surface features indicative of weathering or freshness, while the other uses the frequency and size of dissolution etch pits. A ranking of relative weathering could be obtained using the first technique for the slightly and somewhat weathered soils but not for the weathered soils. On the other hand, weathering trends and differences between the horizons studied were detected in weathered soils using the second method. The introduction of more specific definitions of the weathering classes used in the latter method leads to clear improvement of the inter‐observer reproducibility of the weathering classification.

The surface features on the quartz grains suggest that the soil at the summit is less weathered than the other soils of the sequence. Quartz grains from the well‐drained soils on the slopes, which are subjected to more intense leaching and thus to stronger chemical weathering, have more triangular etch pits and chatter marks. In the imperfectly drained soils in the valley bottom quartz grains are less etched because dissolution is inhibited by the oversaturation in silica of the drainage waters.
The influence of soil processes on carbon isotope distribution and turnover in the British uplands
Authors: Bol R. A. , Harkness D. D. , Huang Y. , Howard D. M.
Published: March 2003

Understanding the natural variation of carbon within the soil, and between soil types, is crucial to improve predictive models of carbon cycling in high and mid‐latitude ecosystems in response to global warming. We measured the carbon isotope distributions (12C, 13C and 14C) in soil organic matter (SOM) from Podzols, Brown Podzolic soils and Stagnohumic Gleysols from the British uplands, which were then compared with the total amounts and turnover of carbon in these soils. We did so by sampling at 2‐cm intervals down six profiles of each soil type. The average amount of carbon stored in the top 28 cm of the Stagnohumic Gleysols is twice that of the other two soils. The 13C content and 14C age show a general increase with depth in all soils, and there is also a significant correlation between isotopic variation and the main pedogenic features. The latter suggests that soil‐forming processes are significant in determining the carbon isotope signatures retained in SOM. Organic matter formed since 1960 is not found below 5 cm in any of the soils. Evidently organic detritus in the surface layers (LF and Oh) is rapidly mineralized. This accords with our modelled net annual C fluxes which show that more than 80% of the CO2 emanating from these soils is derived from the top 5 cm of each profile. Although these soils contain much carbon, they do not appear to assimilate and retain SOM rapidly. The mean residence time of most of their carbon is in the 2–50 years range, so the soils are fairly ineffective sinks for excess CO2 in the atmosphere. Under the predicted future ‘greenhouse’ climate, likely to favour more rapid microbial decomposition of organic materials, these soils are a potential source of CO2 and are therefore likely to accelerate global warming.
Thermal stability and composition of mineral‐bound organic matter in density fractions of soil
Authors: Schulten H. ‐R. , Leinweber P.
Published: March 2003

Heavy density fractions of soil contain organic matter tightly bound to the surface of soil minerals. The chemical composition and ecological meaning of non‐metabolic decomposition products and microbial metabolites in organic–mineral bonds is poorly understood. Therefore, we investigated the heavy fraction (density > 2 g cm–3) from the topsoil of a Gleysol (Bainsville, Ottawa, Canada). It accounted for 952 g kg–1 of soil and contained 19 g kg–1 of organic C. Pyrolysis‐field ionization mass spectra showed intensive signals of carbohydrates, and phenols and lignin monomers, alkylaromatics (mostly aromatic) N‐containing compounds, and peptides. These classes of compound have been proposed as structural building blocks of soil organic matter. In comparison, the light fraction (density > 2 g cm–3) was richer in lignin dimers, lipids, sterols, suberin and fatty acids which clearly indicate residues of plants and biota. To confirm the composition and stability of mineral‐bound organic matter, we also investigated the heavy fraction (density > 2.2 g cm–3) from clay‐, silt‐ and sand‐sized separates of the topsoil of a Chernozem (Bad Lauchstädt, Germany). These heavy size separates differed in their mass spectra but were generally characterized by volatilization maxima of alkylaromatics, lipids and sterols at about 500°C. We think that the observed high‐temperature volatilization of these structural building blocks of soil organic matter is indicative of the organic–mineral bonds. Some unexpected low‐temperature volatilization of carbohydrates, N‐containing compounds, peptides, and phenols and lignin monomers was assigned to hot‐water‐extractable organic matter which accounted for 7–27% of the carbon and nitrogen in the heavy fractions. As this material is known to be mineralizable, our study indicates that these constituents of the heavy density fractions are degradable by micro‐organisms and involved in the turnover of soil organic matter.
Changes in soil chemistry accompanying acidification over more than 100 years under woodland and grass at Rothamsted Experimental Station, UK
Authors: Blake L. , Goulding K. W. T. , Mott C. J. B. , Johnston A. E.
Published: March 2003

We have examined the effect that acid deposition and other sources of acidity have had over the last 110–140 years on soil under woodland (Broadbalk and Geescroft Wildernesses) and grassland (Park Grass) comprising some of the Classical Experiments at Rothamsted Experimental Station. Changes in soil chemistry have been followed by analysing some of the unique archive of stored samples for pH, water‐soluble and exchangeable base cations, aluminium, iron and manganese, exchangeable acidity, cation exchange capacity (CEC) and soluble anions. Proton balances and historical data show the importance of acid deposition to acidification and concomitant changes in the chemistry of the soil. The pH of the surface soil of Geescroft Wilderness has fallen from 6.2 to 3.8 since 1883. The decrease in the pH of the unlimed, unfertilized plot on Park Grass was less over a similar period (from pH 5.2 to 4.2), illustrating the significant effect of the woodland canopy on the interception of acidifying pollutants. The effect of increasing acidity on the soil chemistry of Geescroft Wilderness is seen in its decreasing base saturation and CEC, with base cations moving down the soil profile. Clay minerals are being irreversibly weathered, and Mn and Al progressively mobilized, so that today Al occupies 70% of the exchange complex in the surface soil. Even with present reductions in sulphur deposition critical loads for sulphur, nitrogen and acidity are still exceeded. Such semi‐natural ecosystems are unsustainable under the current climate of pollution.
Surface podzolization in Cambisols under deciduous forest in the Belgian loess belt
Authors: Brahy V. , Titeux H. , Iserentant A. , Delvaux B.
Published: March 2003

Surface podzolization involves the migration of metal–humus complexes to a depth of a few centimetres. In acid soils derived from loess, this process has been diagnosed mainly by morphological observation. We investigated this process in a toposequence of Luvisols and Cambisols on loess using selective extraction and mineralogical data as well as characteristics of the leaf litter. The humus type (O and OAh horizons) is a moder in the three Luvisols and one of the Cambisols, whereas it is a fibrimor in the two other Cambisols. The contents in total alkaline and alkaline‐earth cations range from 35 to 60 cmolckg−1in the fibrimor and from 40 to 90 cmolckg−1in the moder humus. In the two Cambisols with fibrimor smectite occurs in the clay fraction of the Ah horizon; Fe–humus complexes seem to have moved, but no more than 9 cm, from the Ah to the AB horizon beneath. Relative to the Ah horizon, the upper part of the AB has larger tetraborate‐extractable Fe/Al ratio and optical density of the oxalate extract. Such features converge to diagnose surface podzolization in the Cambisols with fibrimor. However, they were not detected in the Cambisol and Luvisols with moder. In the two Cambisols with fibrimor, surface podzolization is consistent with (i) their smaller iron content, (ii) their more advanced weathering stage and (iii) their lower acid neutralizing capacity.
Enchytraeid worms (Oligochaeta) enhance mineralization of carbon in organic upland soils
Authors: Cole L. , Bardgett R. D. , Ineson P.
Published: March 2003

We investigated the functional role of enchytraeid worms (Oligochaeta) in organic upland soils experimentally, because that role of these animals is little known. We made microcosms of intact soil cores cut from two depths, 0–4 cm and 4–8 cm, of a Cambic Stagnohumic Gley from the Moor House National Nature Reserve (UK). Enchytraeids were added to half of the microcosms, resulting in four treatments: litter (L), litter + enchytraeids (L + E), soil (S) and soil + enchytraeids (S + E). Triplicates of each treatment were established, and all microcosms (60) were then incubated in the dark at 15°C, arranged in a fully randomized design. The experiment ran over 110 days, with five destructive harvests at days 10, 25, 50, 75 and 110, when microbial measurements (soil respiration and biomass C) as well as measures of decomposition (nutrient concentration in leachates) were made. Enchytraeids almost doubled the availability of organic carbon (measured as dissolved organic carbon in soil leachates) in the surface (0–4 cm) microcosms only. There were no effects of enchytraeids on the release of inorganic N or P from either soil horizon, although the release of ammonium and phosphate was correlated with the number of enchytraeids in the microcosms. The depth from which the soil was taken exerted a strong influence on nutrient leaching, with almost six times more ammonium and four times more carbon being leached from the surface (0–4 cm) layer than from the more decomposed (4–8 cm) horizon. There was little nitrate leaching from any of the treatments, with only one‐quarter as much nitrate leached from the surface (0–4 cm) as from the subsurface (4–8 cm) horizon. Enchytraeids had no detectable effect on microbial biomass, but they increased microbial respiration by 35% in the surface (0–4 cm) horizon. Because they enhanced microbial activity in this horizon we suggest that enchytraeids indirectly drive the processes of decomposition and nutrient mineralization in organic upland soils.
Ammonium fluoride extraction for determining inorganic sulphur in acid forest soils
Authors: Prietzel J. , Hirsch C.
Published: March 2003

Current methods for determining inorganic sulphur (S) in aerated mineral soil horizons often result in underestimates. To overcome this defect we developed a new method combining a batch extraction with 0.5 m NH4F solution at a soil:solution ratio of 1:5 with a subsequent analysis of the mobilized SO42– by ion chromatography. The ammonium fluoride extraction enables us to characterize inorganic sulphate in non‐calcareous forest soils. It is more efficient than conventional procedures in which inorganic S is extracted with phosphate or bicarbonate solution. In contrast to the extraction with strongly alkaline reagents (NaOH, KOH, LiOH), the NH4+–NH3 buffer system in NH4F prevents the pH of the suspension from exceeding 9.0 and thus the undesired conversion of organic S into SO42– by auto‐oxidation and hydrolysis of ester sulphate. In a comparison we demonstrated that the inorganic S in six German forest soils is underestimated by up to 50% or 200 kg S ha−1 in the uppermost 60 cm, if it is assessed by extraction with 0.016 m KH2PO4 or 0.5 m NaHCO3 instead of 0.5 m NH4F. Conversely, the pool of ester sulphate is overestimated almost threefold.
NEMIS, a predictive model of denitrification on the field scale
Authors: Hénault C. , Germon J. C.
Published: March 2003

We have developed a predictive model of denitrification in soils, NEMIS, based on data from a cultivated field composed of denitrification rates measured on undisturbed soil cores and the corresponding soil water‐filled pore space, nitrate content and respiration. This model is a multiplicative combination of a potential denitrification rate measured under standard conditions defined in this paper, and dimensionless functions of nitrate content, water‐filled pore space and temperature. The model was applied to two further databases obtained independently of its definition. Significant correlation was observed between the simulated and measured denitrification rates. The sensitivity of NEMIS to systematic variations of the input variables and of the coefficients included in the dimensionless functions was tested using these databases. NEMIS seems to be a very useful tool particularly adapted for interpolating a small number of denitrification measurements from a simple database composed of soil potential denitrification rate and the evolution of soil water‐filled pore space, nitrate content and temperature. Its main limitation is its high sensitivity to the water‐filled pore space from which denitrification starts to occur and which is included in the water function.

NEMIS, un modèle prédictif de la dénitrification à l'échelle de la parcelle cultivée

Résumé

NEMIS, un modèle prédictif de la dénitrification dans les sols, a été défini à partir d'une base de données obtenue dans un sol cultivé et composée de vitesses de dénitrification mesurées sur des échantillons de sol non remaniés et les valeurs correspondantes de taux de saturation en eau, de teneur en nitrates et de vitesses de respiration. Ce modèle est une combinaison multiplicative entre une vitesse potentielle de dénitrification mesurée dans des conditions standardisées définies dans ce papier et de fonctions sans dimension de la teneur en nitrates, du taux de saturation en eau et de la température du sol. Ce modèle a ensuite été utilisé sur deux jeux de données indépendantes et des corrélations significatives ont été observées entre mesures et simulations. La sensibilité du modèle lors de variations systématiques du niveau des variables d'entrée ainsi que des coefficients inclus dans les fonctions sans dimension a été testée sur ces jeux de données. NEMIS apparaît comme un outil très utile d'interpolation entre quelques points de mesures de dénitrification à partir d'un jeu de données relativement simple comprenant le potentiel de dénitrification du sol et l'évolution du taux de saturation en eau, de la teneur en nitrates et de la température du sol. La principale limite de NEMIS est sa grande sensibilité au taux de saturation en eau du sol à partir duquel le processus de dénitrification commence à fonctionner.
Quantifying dye tracers in soil profiles by image processing
Authors: Forrer I. , Papritz A. , Kasteel R. , Flühler H. , Luca D.
Published: March 2003

Developing and testing models for solute transport in the field requires experimental data on the spreading of solutes in the soil. Obtaining such data is costly, and a substantial part of the total costs is in the preparation and chemical analysis of the tracing compounds in the gathered samples. We developed a cheap method to quantify the concentration of the mobile dye tracer Brilliant Blue FCF from digitized photographs of stained soil profiles, and we have tested it in the field. Soil sampling and chemical analyses were necessary only to establish a calibration relation between the dye content and the colour of the soil. The digital images were corrected for geometrical distortions, varying background brightness, and colour tinges, and then they were analysed to determine the soil colour at sampling points in the profiles. The resident concentration of the dye was modelled by polynomial regression with the primary colours red, green, blue and the soil depth as explanatory variables. Concentration maps of Brilliant Blue were then computed from the digitized images with a spatial resolution of 1 mm. Validation of the technique with independent data showed that the method predicted the concentration of the dye well, provided the corrected images contained only the colours included in the calibration.
Sorption of dissolved organic nitrogen by acid subsoil horizons and individual mineral phases
Authors: Kaiser K. , Zech W.
Published: March 2003

Dissolved organic matter is important in translocation and export of nutrients from forest ecosystems. Its mobility in soil is restricted by sorption to mineral surfaces which depends on its chemical properties. Carboxyl and hydroxyl groups form strong bondings to mineral surfaces, whereas the role of N‐containing functional groups in the sorption process is less well understood. We examined in laboratory experiments the binding of dissolved organic matter from the forest floor to amorphous Al(OH)3, goethite, kaolinite, and illite and to subsoils in order to compare the sorption and desorption of dissolved organic C with that of dissolved organic N. The mineral samples were equilibrated with acidic solutions of organic matter at pH 4. In the equilibrium solutions organic C and N and their contribution to two operationally defined fractions, namely the so‐called hydrophilic and hydrophobic fractions, were determined. We measured neutral and acidic amino sugars to discover the nature of the binding of organic N. Within the hydrophilic and hydrophobic fractions, the sorption and desorption of organic C and N did not differ, indicating that there was no preferential binding of N‐containing compounds. The hydrophilic fraction contained more N and sorbed less than the hydrophobic fraction, and so the overall retention of organic N by the mineral phases and subsoils was smaller than that of organic C. Among the amino sugar compounds, muramic acid was preferentially removed from the solution, whereas the neutral amino sugars were sorbed similar to organic C. The results suggest that the sorption of N‐containing compounds is favoured by acidic groups and not by amino groups.
Estimation of phosphate adsorption by Acrisols of western Spain from electrical conductivity of potassium dihydrogen phosphate extracts of soil
Authors: Serrano R. Espejo , Arias J. Santano , García E. Pardo , Fernández P. González
Published: March 2003

Estimation of the phosphate adsorption capacity in highly weathered acid soils is crucial for adopting appropriate phosphate fertilization practices. In this work, the salt sorption effect was used to develop a method for estimating phosphate adsorption capacity from the decrease in electrical conductivity of a potassium dihydrogen phosphate solution brought in contact with acidic soil samples from surface and subsurface horizons of Acrisols. The method is fast and simple and requires only the use of a conductimeter.
Re‐evaluation of the structural properties of some British swelling soils
Authors: Groenevelt P. H. , Grant C. D.
Published: March 2003

The structural condition of swelling soils can be assessed from their shrinkage curves. We re‐evaluated data on six British swelling soils using modern methods to model the void ratio, e, as a function of the moisture ratio, ϑ. The points on the e–ϑ curve were fitted with a constitutive shrinkage equation using an unbiased least‐squares, curve‐fitting program. The shrinkage curves were then differentiated to obtain their slopes, σ(ϑ), which were used to calculate the overburden potentials, Ω. The slope functions were subsequently differentiated to obtain the curvatures, κ(ϑ), from which the maximum curvature at the wet end was used to separate the structural shrinkage, Sc, from the proportional (unsaturated) shrinkage. At the point of maximum curvature, Sc and the volumetric air content, θac, were calculated and found to correspond closely to those reported previously. Water retention curves were constructed and fitted using the van Genuchten equation, from which the α coefficient appears an important structural parameter. The structural condition of a swelling soil appears to be well described by its air content at the point of maximum curvature, its van Genuchten α coefficient, and a parameter describing the effect of the overburden potential.
Ultrastructural study of the biogeochemical cycle of silicon in the soil and litter of a temperate forest
Authors: Watteau F. , Villemin G.
Published: March 2003

The biogeochemical cycle of silicon is closely linked to the plant cycle. We have studied the relations between silica and organic matter during humification in a temperate deciduous forest, an acid brown soil ecosystem, the characteristics of which suggest that plants play a major role in the recycling of soluble silica. Our ultrastructural approach consists in identifying the occurrence of biogenic silica in the beech roots, in young and old beech leaves in litter and in the underlying microaggregates of the topsoil. The microaggregates were either sampled directly in situ or isolated by size fractionation.

Observations  of ultrathin sections by transmission electron microscopy at a micrometric scale were combined with electron energy loss microanalysis, which enabled us to identify the silica phases and their associated mineral and organic environments. Some silica deposits were identified in the cell walls of both the beech roots and the beech leaves, whereas pure silica occurred in the root cortical cells as a layer which was closely associated with polyphenolic substances. The ultrastructural study of the microaggregates showed a close association between Si‐cell wall residues and Si‐polyphenolic residues. We also identified a specific bacterial activity that seemed to be related to the degradation of siliceous cell walls. The microquartz in the topsoil showed morphological and analytical transformations that might be considered as weathering. Both ultrastructural observations and the electron energy loss microanalysis showed the presence of biogenic silica and silica‐organic material in litter and soil, and these techniques should enable us to follow the biogeochemical cycle in ecosystems and the bioavailability of silicon.
Vents and seals in non‐steady‐state chambers used for measuring gas exchange between soil and the atmosphere
Authors: Hutchinson G. L. , Livingston G. P.
Published: March 2003

Despite decades of research to define optimal chamber design and deployment protocol for measuring gas exchange between the Earth's surface and the atmosphere, controversy still surrounds the procedures for applying this method. Using a numerical simulation model we demonstrated that (i) all non‐steady‐state chambers should include a properly sized and properly located vent tube; (ii) even seemingly trivial leakiness of the seals between elements of a multiple‐component chamber results in significant risk of measurement error; (iii) a leaking seal is a poor substitute for a properly designed vent tube, because the shorter path length through the seal supports much greater diffusive gas loss per unit of conductance to mass flow; (iv) the depth to which chamber walls must be inserted to minimize gas loss by lateral diffusion is smaller than is customary in fine‐textured, wet or compact soil, but much larger than is customary in highly porous soils, and (v) repetitive sampling at the same location is not a major source of error when using non‐steady‐state chambers. Finally, we discuss problems associated with computing the flux of a gas from the non‐linear increase in its concentration in the headspace of a non‐steady‐state chamber.
Analysing repeated measurements in soil monitoring and experimentation
Authors: Webster R. , Payne R. W.
Published: March 2003

Field monitoring, leaching studies, and experimentation in soil biology are often now being done non‐destructively using fixed installations so that measurements are made repeatedly on the same units. The resulting data for each unit (suction cup, lysimeter, incubation chamber) constitute a time series in which there may be autocorrelation. The usual methods of statistical analysis, such as the analysis of variance, must be modified or replaced by more suitable ones to take account of the possible correlation.

 This paper describes the split‐plot design of such experiments, shows how to assess the variance–covariance matrix of residuals for uniformity by the Greenhouse–Geisser statistic, and shows how to use this statistic to adjust the degrees of freedom in a formal test of significance. It also describes more recent methods. Ante‐dependence analysis identifies the extent of the temporal correlation in the data and provides approximate significance tests for the treatments. Alternatively, the paper also shows how the traditional analysis of variance may be replaced by a restricted maximum likelihood analysis which gives Wald statistics.

 The techniques are illustrated with data on CO2 evolved from soil incubated for 75 days in closed chambers, during which time the gas was measured on 24 occasions to give time series for three replicates of each combination of two soils (limed and unlimed) and three types of ryegrass amendment. An ante‐dependence structure (extending to ninth order) weakened the usual significance test within the subunit stratum. The Wald statistics showed that there was, nevertheless, a strong interaction between the treatments and time.
Effect of non‐linear adsorption on the transport behaviour of Brilliant Blue in a field soil
Authors: Kasteel R. , Vogel H.‐J. , Roth K.
Published: March 2003

The food dye Brilliant Blue FCF (Color Index 42090) is often used as dye tracer in field studies for visualizing the flow pathways of water in soils. Batch studies confirmed findings of other researchers that non‐linear sorption is important for Brilliant Blue, especially at small concentrations (< 10 g l−1 for our soil), and that retardation increases with decreasing concentrations as well as with increasing ionic strength of solutions. Therefore, it is not obvious if it can be used as an indicator for water flow paths as is often done. In this study, we compared the mobility of Brilliant Blue in a field soil (gleyic Luvisol) with that of bromide. Brilliant Blue and potassium bromide were simultaneously applied as a 6‐mm pulse on a small plot in the field, and the tracers were displaced with 89 mm of tracer‐free water using a constant intensity of 3.9 ± 0.2 mm hour−1. Both tracer concentrations were determined on 144 soil cores taken from a 1 m × 1 m vertical soil profile. The transport behaviour differed in both (i) mean displacement and (ii) spatial concentration pattern. We found the retardation of Brilliant Blue could not be neglected and, in contrast to the bromide pattern, a pulse splitting was observed at the plough pan. Numerical simulations with a particle tracking code revealed that the one‐dimensional concentration profile of bromide was represented fairly well by the model, but the prediction of the double peak in the Brilliant Blue concentration profile failed. With additional assumptions, there were indications that Brilliant Blue does not follow the same flow paths as bromide. However, the question of Brilliant Blue taking the same flow pathways as bromide cannot be adequately answered by comparing both concentration distributions, because we look at two different transport distances due to the retardation of Brilliant Blue. It became obvious, however, that Brilliant Blue is not a suitable compound for tracing the travel time of water itself.
The influence of soil pH on denitrification: progress towards the understanding of this interaction over the last 50 years
Authors: ŠImek M. , Cooper J. E.
Published: March 2003

Results from the pioneering research on the interactions between pH and denitrification in soil from the 1950s to the present are reviewed, the changing perceptions of this complex relationship are discussed, and the current status of the subject is assessed. Facets of this relationship that are analysed in detail include the direct or indirect influence of pH on overall denitrification rates in soils, changes in the composition of gaseous products that depend on pH, methods for measuring the process, the concept of an optimum pH for denitrification, and the adaptation of microbial denitrifying communities to acidic environments. The main conclusions to be drawn are as follows. Total gaseous emissions to the atmosphere (N2O, NO and N2) have repeatedly been shown to be less in acidic than in neutral or slightly alkaline soils. This may be attributable to smaller amounts of organic carbon and mineral nitrogen available to the denitrifying population under acid conditions rather than a direct effect of low pH on denitrification enzymes. Numerous laboratory and field studies have demonstrated that the ratio N2O:N2 is increased when the pH of soils is reduced. The relation between soil pH and potential denitrification as determined by various incubation methods remains unclear, results being influenced both by original conditions in soil samples and by unknown changes during incubation. The concept of an optimum pH for denitrification has been frequently proposed, but such a term has little or no meaning without reference to specific attributes of the process.
The effect of reducing conditions on the solubility of phosphorus in a diverse range of European agricultural soils
Authors: Scalenghe R. , Edwards A. C. , Ajmone Marsan F. , Barberis E.
Published: March 2003

The effects of reducing conditions on solubility of phosphorus (P) can directly influence water quality. The release of P is enhanced although the P is not directly involved in reduction processes. We here compare the responses to flooding of 12 overfertilized agricultural soils in widely varying pedological and management regimes, belonging to seven World Reference Base groups. The redox potential initially ranged from 305 to 515 mV and decreased to −157 to −195 mV within 32 days. The onset of reducing conditions led to an increase in the concentration of soluble P. The maximum rate of solubilization occurred within 1–3 weeks under reducing conditions, and the steady‐state concentrations of P never exceeded 200 μmol dm−3. Four stages in the development of the reduction process are identified, and a simple empirical model describes the change in concentrations of soluble P. The potential of P release under reduction is positively correlated with the soil saturation with P. Flooding over a few weeks triggered the release of large amounts of P. Constant pe + pH is related to constant concentration of molybdate‐reactive P, suggesting that soluble P is effectively buffered so that P will be immobilized. In general the solubilization of P under reducing conditions is likely to be aggravated by the increased soil P status that has resulted from overfertilization of agricultural land with P. These findings bear on the establishment and long‐term effectiveness of riparian buffer zones where phosphorus is likely to accumulate by the interception of drainage.
Humus forms and metal pollution in soil
Authors: Gillet S. , Ponge J. F.
Published: March 2003

Smelters in northern France are a serious source of soil pollution by heavy metals. We have studied a poplar plantation downwind of an active zinc smelter. Three humus profiles were sampled at increasing distance from the smelter, and the thickness of topsoil horizons was measured along a transect. We analysed the vertical distribution of humus components and plant debris to assess the impact of heavy metal pollution on the humus forms and on soil faunal activity. We compared horizons within a profile, humus profiles between them, and traced the recent history of the site. Near the smelter, poplar trees are stunted or dead and the humus form is a mor, with a well‐developed holorganic OM horizon. Here faunal activity is inhibited, so there is little faecal deposition and humification of plant litter. At the distant site poplar grows well and faunal activity is intense, so there are skeletonized leaves and many organo–mineral earthworm and millipede faecal pellets. The humus form is a mull, with a well‐developed hemorganic A horizon. The passage from mor to mull along the transect was abrupt, mor turning to mull at 250 m from the smelter, though there was a progressive decrease in heavy metal deposition. This indicates that there was a threshold (estimated to be 20 000 mg Zn kg−1) in the resilience of the soil foodweb.
Simulation of the redistribution of soil by tillage on complex topographies
Authors: Van Oost K. , Van Muysen W. , Govers G. , Heckrath G. , Quine T. A. , Poesen J.
Published: March 2003

Tillage redistributes soil and contributes significantly to the within‐field soil variation, especially on topographically complex terrain. Although the basic principles of the redistribution are well understood, models for simulating the redistribution are poor predictors. This paper presents a modelling structure that allows a simulation of the redistribution of soil constituents on complex topographies for various tillage implements. The model simulates the redistribution of soil constituents by convoluting the probability distribution of the tillage displacement with the spatial distribution of the soil constituents. The probability distributions in two dimensions are derived from a series of tillage experiments conducted with a mouldboard plough at various positions in the landscape. Furthermore, the effects of topography and tillage direction on the probability distributions were characterized and implemented in the model. A first application showed that the direction of tillage significantly affects the long‐term redistribution of soil constituents. The inclusion of other implements in the model was explored, and we found that data in the literature could be used for simulating the long‐term effects of tillage.
Testing the adequacy of measured data for evaluating nitrogen turnover models by the dot‐to‐dot method
Authors: Smith J. U. , Smith P. , Richter G. M. , Agostini F. A. , Welham S. J.
Published: March 2003

Dynamic models of nitrogen turnover in soil are being used increasingly in agricultural science. To be of value, a model must be thoroughly evaluated, and the expected accuracy of simulated values must be defined. Frequent field measurements are time‐consuming and costly, and so models are often evaluated against only few data. However, this mismatch between the measured and simulated values can result in error statistics that are themselves subject to large errors and therefore unreliable. The dot‐to‐dot method quantifies the error associated with having too few measured values by interpolating linearly between measured data (hence, dot‐to‐dot) and evaluating the simulation at each time step using interpolated data where actual measurements are unavailable. A large error will be seen if the measured data do not capture the fluctuations predicted by the model. Other quantitative methods can be used to evaluate the performance of a model, but the dot‐to‐dot method can be used in conjunction with these to estimate whether or not the data are adequate for testing the model. If the performance of the model at the measured points is within the acceptable error, then the dot‐to‐dot method is used to judge whether there are too few points to evaluate the model's performance, and so to determine whether the evaluation of the model is valid.
The dietary regime of detritivorous fish from the River Jacaré Pepira, Brazil
Authors: Vaz M. M. , Petrere M. , Martinelli L. A. , Mozeto A. A.
Published: March 2003

The diet of detritivorous fish was analysed at four distinct habitats in a tropical river during the wet and dry seasons. Two methodologies were used to determine the diet of the fish: (1) the direct analysis of the stomach contents; and (2) the use of stable carbon isotopes. Both methods indicated food partitioning among the fish. The stomach contents showed what the fish had ingested when captured and the 13C isotope indicated what it had assimilated over a long period of time. The 13C isotope suggested the existence of sectional differences in the feeding of the detritivorous fish along the river. Plants employing the C4 photosynthesis pathways seem to have little influence on the diet of these fish. This method proved to be more appropriate for the detection of the main food sources of the captured fish.
Water resources management of the southern rivers of Russia with reference to fisheries requirements
Authors: Dubinina V. G. , Kozlitina S. V.
Published: March 2003

Water consumption from Russia's southern rivers has increased substantially in recent years as a consequence of intensified economic activity. The volume of irreversible river‐flow withdrawal from the Azov Sea basin varies between 11 and 13 km3 year−1. The majority of the abstracted water is used for irrigation. By 1990, the decrease in discharge into the Caspian Sea was 41 km3 year−1. Withdrawals of water from the Kura, Terek, Ural and other rivers have so far exceeded the ecologically admissible limits and become critical. The paper discusses methodological approaches for the elaboration of standards for water withdrawal and ecologically safe discharges into the southern seas. New data are presented on the dynamics of fish abundance as a function of the hydrological characteristics of rivers and water salinity. The results of the system analysis and regressive modelling formed the basis of a programme to develop policies for water management for fisheries in the lower Don. The principles and criteria for water withdrawal under variable hydrological regimes for the rivers entering the Azov and the Caspian Seas should be tested for their applicability for other water bodies (e.g. rivers, water reservoirs and lakes).
Large‐scale, differential summer habitat use of three anadromous salmonids in a large river basin in Oregon, USA
Authors: Scarnecchia D. L. , Roper B. B.
Published: March 2003

The summer distribution of three juvenile anadromous salmonid species was compared in the mainstem sections and nine tributaries of the Upper South Umpqua River Basin, Oregon, USA. Chinook salmon, Oncorhynchus tshawytscha (Walbaum), was found at highest densities in the mainstem and mid‐elevation tributaries. Coho salmon, O. kisutch (Walbaum), was essentially absent from the mainstem, but was found at high densities in the low‐elevation tributaries. Steelhead trout, O. mykiss (Walbaum), was found in the mainstem and all nine tributaries; the highest densities of this species were in the upper mainstem reaches and high‐elevation tributaries. No significant correlations were found between ranks of mainstem and tributary densities among the three species (Spearman's rs;P > 0.05). Observed spatial segregation of basin habitat by these species during summer indicated that protection provided at the level of the river basin will be necessary to assure the continued existence of all stocks.
Resource use of native and stocked brown trout Salmo trutta L., in a subarctic lake
Authors: Kahilainen K. , Lehtonen H.
Published: March 2003

Habitat use, food composition and growth of stocked and native brown trout, Salmo trutta L., were studied in the subarctic Lake Muddusjärvi in northern Finland. Stocked brown trout and native brown trout preferred littoral and pelagic areas. Trout were stocked in October. In June stocked trout fed primarily on invertebrates while native fish were piscivorous. From July onwards the composition of the diet of both stocked and native trout was similar and consisted almost entirely of small‐sized whitefish. Brown trout were already piscivorous at a length of about 20 cm. The mean length of prey consumed was about 12 cm. Mean length‐at‐age was similar from the second year in the lake despite of the larger size of stocked fish during the first year in the lake.
Effects of catch and release angling on Atlantic salmon, Salmo salar L., of the Conne River, Newfoundland
Authors: DEMPSON J. B. , FUREY G. , BLOOM M.
Published: March 2003

The effects of catch and release angling on survival of Atlantic salmon, Salmo salar L., at Conne River, Newfoundland, were investigated by retaining angled (n=49; experimental group) and trap‐caught (n=20; control group) fish in holding cages for up to 40 days. Samples were obtained from 8 June to 4 July, 2000, and partitioned among four water temperature strata. Apart from not being angled, control fish were handled, tagged, and transferred to holding cages in a manner similar to angled salmon. Water temperatures and discharge were monitored throughout the duration of the study. Overall, 8.2% of salmon caught and released died, but 12% died among salmon angled in water temperatures ≥ 17.9 °C. No control fish died. There were no significant differences in time associated with angling, exposure to air, tagging, transfer to holding cages, nor total handling time between salmon that survived vs. those that died. Results of the study should encourage managers to continue to use catch and release as a viable tool in the management of Atlantic salmon stocks.
Evaluation of the robustness of predictive yield models based on catchment characteristics using GIS for reservoir fisheries in Sri Lanka
Authors: AMARASINGHE U. S. , DE SILVA S. S. , NISSANKA C.
Published: March 2003

Land‐use patterns in the catchment areas of Sri Lankan reservoirs, which were quantified using Geographical Information Systems (GIS), were used to develop quantitative models for yield prediction. The validity of these models was evaluated through the application to five reservoirs that were not used in the development of the models, and by comparing with the actual fish yield data of these reservoirs collected by an independent body. The robustness of the predictive models developed was tested by principal component analysis (PCA) on limnological characteristics, land‐use patterns of the catchments and fish yields. The predicted fish yields in five Sri Lankan reservoirs, using the empirical models based on the ratios of forest cover and/or shrub cover to reservoir capacity or reservoir area were in close agreement with the observed fish yields. The scores of PCA ordination of productivity‐related limnological parameters and those of land‐use patterns were linearly related to fish yields. The relationship between the PCA scores of limnological characteristics and land‐use types had the appropriate algebraic form, which substantiates the influence of the limnological factors and land‐use types on reservoir fish yields. It is suggested that the relatively high predictive power of the models developed on the basis of GIS methodologies can be used for more accurate assessment of reservoir fisheries. The study supports the importance and the need for an integrated management strategy for the whole watershed to enhance fish yields.