bluuebunny/crossref_metadata_2025 huggingface dataset:
Iron‐overload and genotypic expression of HFE mutations H63D/C282Y and transferrin receptor Hin6I and BanI polymorphism in German patients with hereditary haemochromatosis
Authors: Gottschalk R. , Seidl C. , Schilling S. , Braner A. , Seifried E. , Hoelzer D. , Kaltwasser J. P.
Published: March 2003

Gene variations of HFE, a HLA‐class I like molecule, are highly associated with hereditary haemochromatosis (HH). Functional as well as molecular studies of the HFE protein have indicated that the molecule is involved in iron metabolism and that the HFE gene variations observed among HH patients affect its interaction with the transferrin receptor (TfR). In the present study, we have therefore analysed the relationship between the HFE gene variants, C282Y and H63D, and body iron status among 85 German HH patients. In addition, two TfR gene polymorphism, TfR‐Hin6I and TfR‐BanI, were typed that have been reported to define ethnically distinct haplotypes. As controls we used 251/159 healthy German blood donors. Seventy‐eight (92%) patients were C292Y homozygous, the H63D mutation was present in five (6%) patients with none of the patients being H63D homozygous. Serum transferrin, transferrin saturation and liver iron content were determined prior to therapeutic intervention. Among C282Y homozygous patients serum ferritin levels (2294 ± 3174 vs. 463 ± 224 µg L−1, P < 0.0001) and transferrin saturation (86 ± 18% vs. 62 ± 25%, P = 0.048) were elevated significantly compared with C282Y and/or H63D heterozygous patients. In addition, the liver iron content (291 ± 165 vs. 138 ± 95 µmol g−1, P = 0.028) and liver iron index (6.4 ± 2.8 vs. 3.2 ± 2.3, P = 0.019) were increased among C282Y homozygotes compared with C282Y heterozygotes. In contrast, no difference was observed between patients and controls regarding the distribution of TfR‐Hin6I and TfR‐BanI alleles. These data indicate that the iron intake is higher among C282Y homozygous patients compared with C282Y heterozygous or C282Y/H63D compound heterozygous individuals and supports the functional role of the HFE protein in iron metabolism whereas the TfR gene variants seem to have no influence on iron uptake.
Allele frequencies of polymorphisms of the tumour necrosis factor‐α, interleukin‐10, interferon‐γ and interleukin‐2 genes in a North European Caucasoid group from the UK
Authors: Reynard M. P. , Turner D. , Navarrete C. V.
Published: March 2003

Cytokine gene polymorphisms affecting cytokine production may influence rejection and graft‐versus‐host disease following solid organ and haemopoietic stem cell (HSC) transplantation, respectively. Polymorphisms in the regulatory regions of several cytokine genes have been described; for example, tumour necrosis factor‐α (TNF‐α) has a G/A substitution at position −308, interleukin‐2 (IL‐2) has a T/G substitution at position −330 and interleukin‐10 (IL‐10) has substitutions at positions −1082(G/A), −819(C/T) and −592(C/A). Microsatellites associated with cytokine production have been detected in the first intron of the IFN‐γ gene and flanking the TNF‐α gene. In this study, we have genotyped a single panel of healthy Northern European Caucasoids living in the south‐east of England for the above‐mentioned polymorphisms and compared the results to those published for other populations. A PCR method using sequence‐specific primers (SSP) was developed for genotyping the IL‐2 polymorphism, and the ABI PRISM™ 310 genetic analyser was used to detect the TNF‐α and IFN‐γ microsatellites. The allele frequencies of all the studied polymorphisms were consistent with those reported for other UK Caucasoid populations, but differences were observed when compared to other Oriental, African and Caucasoid groups. If these cytokine polymorphisms prove to have functional consequences, then any differences across population groups may have significant clinical relevance in disease and in the outcome of solid organ and HSC transplantation.
TCRBV3S1 and TCRBV18 gene segment polymorphisms in Brazilian Caucasoid and Black populations
Authors: Dresch C. , Nardi N. B. , Chies J. A. B.
Published: March 2003

The T‐cell receptor (TCR) repertoire plays an important role in shaping specific immune responses. Genetic polymorphisms at the TCR locus, in both constant and variable regions, seem to represent an important mechanism for generating inter‐individual and inter‐population differences. Considering the scarcity of immune parameters characterized for normal human populations, we decided to determine the frequency of two TCRBV polymorphisms (located in the TCRBV3S1 and TCRBV18 gene segments) in two ethnically distinct groups of the general Brazilian population. Both polymorphisms are related to the expression of these segments at the T‐cell surface and can consequently modulate the T‐cell repertoire, potentially modifying the capacity of a given individual to develop an immune response. These DNA polymorphisms were analysed in material obtained from adult, normal South‐American Caucasoid and Black individuals. A total of 139 individuals were analysed for the TCRBV3S1 and 141 for the TCRBV18 gene segment polymorphisms. The data indicated statistically significant differences in allelic frequencies for the two ethnic groups analysed, suggesting that any correlation between TCR usage or T‐cell repertoire and development of a given disease should take in account the ethnic origin of the population studied.
Identification of a new isoform of human IL‐12 p35 mRNA
Authors: Johansson U. , Cooke S. P. , Londei M.
Published: March 2003

This study has identified an alternate mRNA isoform of the human interleukin‐12 p35 gene differing from normal p35 transcripts by the deletion of exon 3. Exon 3‐lacking p35 mRNA was produced by both dendritic cells and Epstein‐Barr virus‐transformed B cells and was detected only when transcription of normal p35 mRNA was abundant.
Associations of HLA class II alleles with pulmonary tuberculosis in Thais
Authors: Vejbaesya S. , Chierakul N. , Luangtrakool K. , Srinak D. , Stephens H. A. F.
Published: March 2003

Tuberculosis is an important infectious disease in Thailand. Susceptibility to tuberculosis is influenced not only by the environment but also by host genetic factors. In this study, we investigated HLA alleles in 82 patients with tuberculosis from Bangkok and in 160 normal controls. HLA‐DRB1, DQA1 and DQB1 genotyping was performed by the PCR‐SSO method. The frequency of HLA‐DQB1*0502 was increased in tuberculosis patients compared to the normal controls (P = 0.01, OR = 2.06). In contrast, the frequencies of DQA1*0601 and DQB1*0301 were decreased in tuberculosis patients compared to the controls (P = 0.02 and P = 0.01, respect­ively). Our results suggest that HLA‐DQB1*0502 may be involved in the development of pulmonary tuberculosis, whereas HLA‐DQA1*0601 and DQB1*0301 may be associated with protection against tuberculosis.
Determination of free Al3+ in soil solutions by capillary electrophoresis
Authors: Göttlein A.
Published: March 2003

Colorimetric and ion exchange methods are commonly used to distinguish and measure Al species in natural waters. Unfortunately they also include weakly complexed Al species in their ‘reactive' or ‘labile' Al fractions and thus are of limited value for the estimation of free Al3+. Capillary electrophoresis (CE) has the potential for direct measurement of Al3+, and its performance has been verified experimentally. The method also detected the stable and positively charged AlOx+ complex formed with oxalic acid. It was compared with a colorimetric and an ion exchange method by analysing artificial solutions containing low molecular weight organic acids as well as soil extracts and seepage waters and was found to be the only method closely matching the theoretically calculated values of free Al3+. In samples from the upper soil horizons of an acid forest soil less than 14% of total Al was present as free Al3+, whereas the colorimetric method found more than 65%, and the ion exchange method more than 80% of total Al in a ‘reactive' or ‘labile' form. The latter methods thus would seriously overestimate Al toxicity, whereas using CE Al toxicity is likely to be only slightly underestimated.
Fixation of radiocaesium in an acid brown forest soil
Authors: Maes E. , Delvaux B. , Thiry Y.
Published: March 2003

The OAh and Ah horizons of acid brown and podzolic forest soils are reported to fix more radiocaesium than the mineral B horizons beneath them. We determined the respective influence of organic matter and clay minerals on the magnitude of Cs+ retention in a strongly acid brown forest soil in Belgium. The soil contained mica throughout the profile. Vermiculite was identified in the OAh and Ah horizons, and hydroxy interlayered vermiculite (HIV) in the Bw horizon. The OAh and Ah clay fraction retained much more Cs+ than the Bw horizon. The extraction of Al interlayers by Na‐citrate resulted in a marked increase in Cs+ fixation in the Bw clays as well as the collapse of the vermiculitic layers after K+ saturation. Organic matter had a strong but indirect effect on Cs+ fixation. In the Bw horizon, acid weathering of layer silicates releases free Al and produces HIV minerals in which Al polymers block the access of radiocaesium onto Cs+‐specific sites. In OAh and Ah horizons, free Al is complexed by organic acids. Consequently, the interlayer specific sites remain accessible for Cs+ fixation.
A combination of laser technology and fractals to analyse soil surface roughness
Authors: PARDINI  , GALLART
Published: March 2003

Laboratory experiments were conducted on artificially weathered mudrocks (i) to measure changes in the roughness following cycles of freezing and thawing, and (ii) to find a simple method to calculate roughness as an alternative method to standard deviation methods. Surface roughness was measured with a laser profile meter and the resulting measurements were analysed by a program written for the purpose. The analysis is based on calculation of the fractal dimension of the profile for selected ranges of scale, and estimated by linear regression. Results revealed distinct micro‐ and macrotopographic variations of artificially weathered surface samples.
Morphological and genetic relations between siderite, calcite and goethite in a Low Moor Peat from southern Germany
Authors: McMILLAN  , SCHWERTMANN
Published: March 2003

Siderite, calcite and goethite occur in a Low Moor Peat near Freising, southern Germany. Siderite is present mainly as microcrystalline ovoids which have a lamellar structure and are less than 5 μm long. Selected area electron diffraction and X‐ray diffraction data suggest a crystal size less than that of the ovoids, probably as small as 20–50 nm. Siderite occurs interstitially between plant materials, predominantly of the genus Equisetum. Calcite, which is subordinate to siderite, occurs as pseudomorphs of plant cells. This suggests an earlier crystallization for calcite predating that of the siderite.

The distribution of mineral morphologies and pH and Eh data suggest that siderite weathers by oxidation to goethite under mildly alkaline conditions, despite the probable production of protons. This process initially involves a pseudomorphism of the siderite ovoids by goethite. However, the goethite, comprising poorly acicular crystals with a mean coherence length of 11 nm normal to the 111 plane, eventually develops into a massive fabric.

Calcite occurs with goethite in oxidized samples in the same location as in the unoxidized samples, but in decreased amount. Thus, calcite dissolution may act as a buffer to siderite oxidation.
Nitrous oxide production by denitrification and nitrification in temperate forest, grassland and agricultural soils
Authors: AMBUS P.
Published: March 2003

Nitrous oxide is produced in soils by biological denitrification and nitrification. To improve the fundamental understanding of the processes leading to N2O fluxes from soils, the production of N2O from denitrification and nitrification in spruce forest, beech forest, riparian grassland, coastal grassland and an agricultural field were studied. Samples were taken at a high and a low position along a topographic gradient in each site in the spring and autumn when the largest N2O fluxes were expected. They were incubated after being amended with N, and C2H2 was used as biological inhibitor to distinguish nitrification and denitrification.

The N2O production in the low landscape position varied between 32 and 121 ng N cm−3 h−1 in the riparian grassland. 9 and 26 ng N cm−3 h−1 in the coastal grassland, and 135 and 195 ng N cm−3 h−1 in the agricultural field which was 10–100 times more than in the high positions where rates ranged between 3 and 5 ng N cm−3 h−1, 0.3 and 0.4 ng N cm−3 h−1, and 7 and 10 ng N cm−3 h−1, respectively. These differences almost certainly arose because the soil in the low positions was wetter and contained more organic matter. In the two forests N2O production was less than 1 ng N cm−3 h−1, strongly inhibited by O2, and not influenced by landscape position. Nitrification contributed to more than 60% of total N2O production in the riparian grassland. In the agricultural field nitrification produced 13–74% of the total N2O in the low position, and 10–88% in the high position. Denitrification was the dominant source of N2O in the coastal grassland except at the low position in the autumn where nitrification produced 60% of the total N2O. In the two forests where the soil had small nitrification potentials denitrification was the only source of N2O. In the other sites nitrification and denitrification potentials were large and of identical magnitude. The results emphasize the need to separate nitrification and denitrification at the process level and to recognize topography at the field scale when modelling N2O effluxes from soil.
Composition of soil organic matter and its water‐soluble fraction under young vegetation on drift sand, central Netherlands
Authors: NIEROP K. G. J. , BUURMAN P.
Published: March 2003

Podzols tend to form on drift sands in The Netherlands given sufficient time. Differences in organic matter (OM) composition relate to vegetation succession on drift sand that evolves eventually into a micropodzol. We examined the relation between the water‐soluble organic matter (WSOM) and the total OM composition in the Ah horizons of the first vegetation stages, under grass (Corynephorus canescens), moss (Polytrichum piliferum), heather (Calluna vulgaris) and pine (Pinus sylvestris), as determined by pyrolysis‐gas chromatography/mass spectrometry (Py‐GC/MS) and analysis of polysaccharides after acid hydrolysis. Polysacharides dominate the OM in the Ah horizons under grass and moss. Lignin and aliphatic compounds are minor compounds in these profiles, but are more important under heather and pine. The Py‐GC traces of the WSOM under grass and moss contain abundant products derived from polysaccharides. The water‐soluble fraction is enriched in phenolic and aliphatic compounds in comparison with their contents in pyrolysates of the total OM. In the WSOM fractions under heather and pine, phenols dominate the pyrolysates, whereas lignin‐derived methoxyphenols are rare. Remarkably large amounts of alkenes and alkanes are present in the pyrolysates of these water‐soluble fractions, most probably derived from aliphatic biopolymers. Their presence in water might be explained through the formation of colloids, which are stabilized by micelle‐like arrangements.
The immobilization of nitrogen by straw decomposing in soil
Authors: Cheshire M. V. , Bedrock C. N. , Williams B. L. , Chapman S. J. , Solntseva I. , Thomsen I.
Published: March 2003

Immobilization of nitrogen (N) in decomposing straw varies between soils, and the objective of this study was to identify the mechanisms responsible. Internode segments of wheat straw were incubated in Denmark and in Scotland in arable soils fertilized with NH4NO3, labelled with15N, for periods up to 1 year. Straw was recovered from the soils periodically and analysed for microbial biomass and different forms of N using chemical methods and CPMAS15N NMR spectroscopy.

The total N content of the straw increased, as long as the soil was not too wet, such that there was overall immobilization. This was accompanied by a rapid increase in the content of amino acid N and to a lesser extent of glucosamine N and a concomitant decrease in the carbohydrate content of the straw. Using direct and plate counts for bacterial and ergosterol content for fungal estimation, we found that fungal biomass was much greater than that of bacteria. This correlated with the forms of N in the straw as determined by CPMAS15N NMR, which showed spectra that were more typical of fungi than of bacteria. It seems that immobilization of N is primarily caused by fungi as they decompose the straw.
Modelling changes in cations in the topsoil of an Amazonian Acrisol in response to additions of wood ash
Authors: Ludwig B. , Khanna P. K. , Hölscher D. , Anurugsa B.
Published: March 2003

Predictions of changes in soil solution chemistry and exchangeable cations which occur on ash deposition after slash burning are complex and may be facilitated by the use of chemical models. Multi‐ion sorption in the topsoil of an Amazonian Acrisol was studied by sequentially adding small amounts of electrolytes to soil and mixtures of soil and ash in batch experiments. A chemical equilibrium model that included inorganic complexation, multiple cation exchange and sparingly soluble salts (aluminium hydroxide and magnesian calcites) was used to interpret the results. The model predicted well the pH and sorption values in all experiments in which there was no addition of ash. The model suggested that cation exchange was the main process determining concentrations of soil solutions in all cases where neutral salt solutions were added, and that proton buffering was achieved by the dissolution of Al(OH)3 which was followed by Al3+ adsorption. Calculation of ion activity products in solutions from various batch experiments in soil + ash mixtures suggested that magnesian calcites of differing solubility may be in equilibrium with the activities of Mg2+ and Ca2+ in solution. An incongruent dissolution of Mg resulted in less soluble magnesian calcites in the ash. The model estimated satisfactorily the pH and the sorption of ions for all experiments with differing ash additions to the soil. Most of the Ca and significant amounts of Mg added in the ash are expected to remain for a long time in the soil and may determine the Ca and Mg status of the soil solution, primarily controlled by principles of solubility products.
Closed chamber systems underestimate soil CO2 efflux
Authors: Rayment M. B.
Published: March 2003

Chamber systems are widely used to measure soil CO2 efflux, using either a closed or an open gas exchange methodology. In comparisons between these two methods fluxes measured with closed systems are often found to be around 10% less than those measured with open systems. One reason why closed chambers might systematically underestimate the true efflux rate is that the effective chamber volume is larger than the volume of the chamber alone, i.e. it includes the volume of air‐filled spaces in the soil. In tests carried out in a northern forest, this error resulted in a closed chamber underestimating the true efflux by up to 30%, with an average underestimation of around 10%.
A re‐evaluation of the enriched labile soil organic matter fraction
Authors: Six J. , Merckx R. , Kimpe K. , Paustian K. , Elliott E. T.
Published: March 2003

Identifying ‘functional' pools of soil organic matter and understanding their response to tillage remains elusive. We have studied the effect of tillage on the enriched labile fraction, thought to derive from microbes and having an intermediate turnover time. Four soils, each under three regimes, long‐term arable use without tillage (NT), long‐term arable under conventional tillage (CT), and native vegetation (NV), were separated into four aggregate size classes. Particle size fractions of macro‐ (250–2000 μm) and microaggregates (53–250 μm) were isolated by sonication and sieving. Subsequently, densiometric and chemical analyses were made on fine‐silt‐sized (2–20 μm) particles to isolate and identify the enriched labile fraction. Across soils, the amounts of C and N in the particle size fractions were highly variable and were strongly influenced by mineralogy, specifically by the contents of Fe and Al oxides. This evidence indicates that the fractionation procedure cannot be standardized across soils. In one soil, C associated with fine‐silt‐sized particles derived from macroaggregates was 567 g C m−2 under NV, 541 g C m−2 under NT, and 135 g C m−2 under CT, whereas C associated with fine‐silt‐sized particles derived from microaggregates was 552, 1018, 1302 g C m−2 in NV, NT and CT, respectively. These and other data indicate that carbon associated with fine‐silt‐sized particles is not significantly affected by tillage. Its location is simply shifted from macroaggregates to microaggregates with increasing tillage intensity. Natural abundance 13C analyses indicated that the enriched labile fraction was the oldest fraction isolated from both macro‐ and microaggregates. We conclude that the enriched labile fraction is a ‘passive' pool of soil organic matter in the soil and is not derived from microbes nor sensitive to cultivation.
Disruption of soil aggregates by varied amounts of ultrasonic energy in fractionation of organic matter of a clay Latosol: carbon, nitrogen and δ13C distribution in particle‐size fractions
Authors: Roscoe R. , Buurman P. , Velthorst E. J.
Published: March 2003

Ultrasonic energy has been widely used to disrupt soil aggregates before fractionating soil physically when studying soil organic matter (SOM). Nevertheless, there is no consensus about the optimum energy desirable to disrupt the soil. We therefore aimed (i) to quantify the effect of varied ultrasonic energies on the recovery of each particle‐size fraction and their C, N and δ13C distribution, and (ii) to determine an ideal energy to fractionate SOM of a specific soil. Our results show that the 2000–100 μm particle‐size fraction was composed mainly of unstable aggregates and the 100–2 μm fraction of stable aggregates. Energies of 260–275 J ml−1 were sufficient to disrupt most of the unstable aggregates and leave stable aggregates. The use of this threshold energy combined with particle‐size fractionation was not satisfactory for all purposes, since litter‐like material and relatively recalcitrant organic carbon present in stable aggregates > 100 μm were recovered in the same pool. An ultrasonic energy of 825 J ml−1 was not sufficient to stabilize the redistribution of soil mass and organic matter among particle‐size fractions, but at energies exceeding 260–275 J ml−1 relatively stable aggregates would fall apart and cause a mixture of carbon with varied nature in the clay fraction.
Modelling structural changes in tilled topsoil over time as a function of cropping systems
Authors: Roger‐Estrade J. , Richard G. , Boizard H. , Boiffin J. , Caneill J. , Manichon H.
Published: March 2003

The optimization of tillage practices requires the evaluation of the long‐term effects of cropping on changes in soil structure. A model is presented that simulates changes in soil structure in the tilled horizons of cultivated fields. The indicator of soil structure that we have modelled is based on a morphological description of the structure and the assessment of the percentage of severely compacted zones and clods showing no visible porosity in the tilled layer of a soil profile. The model takes into account the spatial variation of the structure induced by traffic and tillage. Severely compacted zones are created under wheel tracks, they are cut and transferred during ploughing, and they are fragmented into fine soil during secondary tillage. The model was evaluated over 7 years in a field trial on loamy soil in three experimental plots, where the crop sequences and field operations induced contrasted changes in the percentage of severely compacted zones and clods. The model satisfactorily reproduced the changes with time of the indicator, and the correspondence between simulated and observed values was fairly good (r= 0.82, model efficiency = 0.61). However, some variations from one year to the next were poorly predicted. The sensitivity analysis did not suggest modification to the parameter values but showed that the performance of the model could be improved if the fragmentation (due to weather and tillage) were more precisely described in the model. Nevertheless the present version of the model and the corresponding simulation program (SISOL) can be used to compare the effects of different technical choices on the evolution of soil structure.
Solid‐state 13C‐NMR dipolar dephasing experiments for quantifying protonated and non‐protonated carbon in soil organic matter and model systems
Authors: Smernik R. J. , Oades J. M.
Published: March 2003

Dipolar dephasing was investigated as a means for quantitatively differentiating protonated and non‐protonated and molecularly mobile and rigid components in soil organic matter. We experimented on cellulose, hemicelluloses, lignin, a protein, chitin, charcoal, palmitic acid and two waxes which served as model systems for components of soil organic matter. Dipolar dephasing decay curves showed significant deviation from the expected exponential decay (for non‐protonated and methyl carbons) and Gaussian decay (for non‐methyl protonated carbons), partly due to rotational and dipolar modulation. No signal is observed for most protonated carbon (excluding methyl carbon) for a dipolar dephasing delay of 45 μs, and so we generated three subspectra, representing non‐protonated, non‐methyl protonated and methyl carbon classes, requiring the acquisition of just the 0‐ and 45‐μs dipolar dephased spectra. This methodology was applied to eight samples of soil organic matter, allowing the determination of relative contributions of overlapping resonances such as C‐substituted and H‐substituted aromatics (110–145 p.p.m.), carbohydrate anomeric and tannin (90–110 p.p.m.), and amino acid and methoxyl (45–65 p.p.m.). The waxes behaved aberrantly, probably because some of their components are highly mobile. We determined accurately the exponential dipolar dephasing decay rates of non‐protonated carbon resonances, free from the interference of rotational and dipolar modulations.
Interactions of fulvic acid with aluminium and a proto‐imogolite sol: the contribution of E‐horizon eluates to podzolization
Authors: Farmer V. C. , Lumsdon D. G.
Published: March 2003

The podzolization process is examined in the light of measurements of the solubility characteristics of aluminium fulvate, the extent of dissolution of a proto‐imogolite sol by fulvic acid, the adsorption capacity of proto‐imogolite for fulvic acid and aluminium fulvate, and published evidence. Fulvic acid at 500 mg l−1 acting on a proto‐imogolite (PI) preparation containing 0.95 mmol l−1 Al as PI did not bring enough Al into solution at pH 4.5–5.0 over 4–15 months to cause significant precipitation of the fulvic acid. As allophanic Bs horizons of podzols typically have pH ≥ 4.8, fulvic acids entering them in drainage water cannot be quantitatively precipitated by dissolution of Al from the allophane. They are, however, strongly absorbed on the allophane, and this must be the mechanism that removes most of the fulvic acid at the top of the Bs horizon, and which contributes, along with colloidal humus and root decomposition, to the formation of a Bh horizon.

We conclude that fulvic acid plays no active role in podzolization, but only recycles Al and Fe, that have been transferred by biological processes to the O horizon, back to the Bh horizon. The podzolization process, which leads to the formation of an allophanic Bs horizon underlying a progressively deepening E horizon, requires the dissolution of Al‐humate and allophanic precipitates at the Bh–Bs interface as well as progressive attack on the more readily weatherable minerals. Inorganic acids, particularly episodic fluxes of nitric acid, could play a major role in this, as well as attack by readily metabolized complexing acids such as oxalic and citric acids released by roots and fungi.

In addition to throwing light on the podzolization process, the experimental results provide an explanation of the lower limit to C:Al ratios reported in natural waters, and a check on the applicability of the WHAM chemical equilibrium model to Al–fulvate–proto‐imogolite equilibria. In Ca‐containing fulvate solutions, Al‐fulvate begins to precipitate when C:Al falls below 50, which is also the limiting ratio observed in natural waters. WHAM calculations overestimate by 70–85% the amount of Al‐fulvate formed over 4 months at pH 4.5–5.0 in Ca‐containing fulvate–imogolite systems.
Application of a two‐dimensional model to simulate flow and transport in a macroporous agricultural soil with tile drains
Authors: Abbaspour K. C. , Kohler A. , Simunek J. , Fritsch M. , Schulin R.
Published: March 2003

It is essential that important field processes are taken into account to model water flow and chemical transport accurately in agricultural fields. Recent field studies indicate that transport through macropores can play a major role in the export of solutes and particulates from drained agricultural land into surface water. Non‐ideal drain behaviour may further modify the flow and transport. We extended an existing two‐dimensional flow and transport model for variably saturated soils (SWMS_2D) by adding a macropore domain and an additional Hooghoudt drain boundary condition. The Hooghoudt boundary condition accounts for an entrance head needed to initiate flow into the drains. This paper presents the application of the new model (M‐2D) to an agricultural field in Switzerland. To understand interactions between macropore flow and drains better we simulated water flow and bromide transport for four different field scenarios. We considered both collector drains only with an ideal drain boundary condition (with and without macropores) and collectors and laterals with a Hooghoudt boundary condition (also with and without macropores). For each scenario, inverse modelling was used to identify model parameters using 150 days of data on observed cumulative discharge, water table depth, and tracer concentration. The models were subsequently tested against a 390‐day validation data set. We found that the two additional components (macropore flow, drain entrance head) of the M‐2D model were essential to describe adequately the flow regime and the tracer transport data in the field.
Cation exchange resin and test vermiculite to study soil processes in situ in a toposequence of Luvisol and Cambisol on loess
Authors: Brahy V. , Delvaux B.
Published: March 2003

Both the ion accumulation on cation exchange resin and the transformation of test vermiculite in situ have been used to identify current processes in acid forest soils. We used such test materials to study weathering in a toposequence Dystric Luvisol–Spodo‐Dystric Cambisol on loess under deciduous forest in Belgium. The resin and a trioctahedral vermiculite were inserted for 2 years in the major horizons, down to a depth of 60 cm. The cation accumulation on the resin revealed that four main acid‐consuming systems are currently active in the toposequence. With decreasing acid neutralizing capacity, these systems are in the Luvisols: (i) the pool of exchangeable bases, (ii) the Al‐bearing minerals controlling the Al concentration in the liquid phase; and in the podzolized Cambisols: (iii) the less weatherable K‐bearing minerals, (iv) the Mg‐bearing phyllosilicates made free of Al interlayers in complexing conditions. The loss of cation exchange capacity in the test vermiculite is related to Al interlayering. However, this process masks a significant interlayer accumulation of magnesium, which is generated by the weathering of the test mineral itself. The largest interlayer accumulation of Mg occurs in the podzolized Cambisol, suggesting more intense weathering of the test vermiculite in this soil.
Sorption and transport of metals in preferential flow paths and soil matrix after the addition of wood ash
Authors: Bundt M. , Zimmermann S. , Blaser P. , Hagedorn F.
Published: March 2003

As a consequence of heterogeneous transport in soils, only a small part of the soil might be responsible for sorbing incoming elements. After staining preferential flow paths in forested Dystric Cambisol with a colour dye, we sampled soil material from the flow paths and from the soil matrix. We measured chemical properties and sorption isotherms of these two flow regions and estimated the significance of preferential flow paths for the transport of solutes leached from wood ash applied at the surface. In the A horizon (0–9 cm depth), the cation exchange capacity of the flow paths was 83.8 mmolc kg−1, while that of the soil matrix was only 74.6 mmolc kg−1. The base saturation was 42% and soil organic matter content was 41% larger in flow paths than in the soil matrix. The sorption capacity for Cu was also larger than in the matrix, whereas the sorption capacity for Sr was similar in both flow regions. The impact of the addition of 8 t wood ash ha−1 on soil chemical properties was restricted mainly to the flow paths in the uppermost 20 cm of the soil; it was negligible in the matrix and at greater depths. Concentrations of exchangeable Ca in the flow paths increased nearly 10‐fold during the 6 months following the addition of the wood ash, and those of organically bound Pb by 50%. The opposite effect was found for exchangeable Al. Our results show that only part of the whole soil volume, approximately 50% of 0–20 cm in our study, is involved in transporting and sorbing the elements applied with the wood ash or as tracers. Such differences must be considered when calculating the maximal impact of any addition of fertilizer, wood ash, or liming agent.
Humus composition of soils under forest, coffee and arable cultivation in hilly areas of south Sumatra, Indonesia
Authors: Watanabe A. ,   Sarno, Rumbanraja J. , Tsutsuki K. , Kimura M.
Published: March 2003

To understand the effect of land use changes on the composition of humus in tropical soils, samples from land under primary forest, secondary forest, coffee plantation, and arable crops were investigated at three sites in south Sumatra, Indonesia. Total carbon and total nitrogen contents were 1.7 to 4.3 times and 1.1 to 2.8 times greater in the topsoil under primary forest than under the other types of land use. Following change from primary forest to other uses, the proportion of humic acids in the organic matter of the topsoils decreased while that of the fulvic acid fraction increased. Within the range of land uses, differences in the yields of humic acids and fulvic acid fractions were, respectively, larger and smaller than those in total carbon content. The humic acids were classified into the low and middle classes in the degree of humification. Absorption due to the green fraction of humic acids, Pg, was detected in the UV‐visible spectra of almost all the humic acids. No relation was observed between the degree of humification of humic acids or the strength of Pg absorption in their spectra and land use change. The fulvic acid fractions were fractionated on insoluble polyvinylpyrrolidone (PVP) into the adsorbed fractions consisting of humic substances and the non‐adsorbed fractions consisting of non‐humic substances. A positive correlation between the amount of the fulvic acid fraction and the percentage of the PVP‐adsorbed fraction within it indicated that the variation in the amount of the fulvic acid fraction was attributable to acid‐soluble humic substances. The ionization difference spectra of solutions between pH 12 and pH 7 suggested that the chemical structures of the PVP‐adsorbed fulvic acids have been altered by land use change.
Determination of the free ion concentration of trace metals in soil solution using a soil column Donnan membrane technique
Authors: Weng L. , Temminghoff E. J. M. , Van Riemsdijk W. H.
Published: March 2003

Accurate measurement of the free metal ion is difficult, especially for trace metals present in very small concentrations (less than micromolar) in natural systems. The recently developed Donnan membrane technique can measure the concentrations in solution in the presence of inorganic and organic complexing agents. We have developed this method further to make it applicable for analysing soil samples. The major development is the linkage of a soil column with the Donnan cell. The operational aspects of the method, including equilibrium time, buffering capacity and correction for differences in ionic strength, were investigated and optimized. The method was applied to determine concentrations of free Cu2+, Cd2+, Pb2+ and Zn2+ in the soil solution of 15 soil samples (pH 2.9–7.1, organic C < 2.9–137.4 g kg−1, clay 0.2–51.6%). Compared with other speciation methods, the Donnan membrane technique has the advantage of allowing the measurement of several elements simultaneously and it minimizes the disturbance of substrate. The detection limit of the technique is about 10−9 m. This method can be applied to study the biogeochemical behaviour of metals in soils, sediments and other solid materials.
Nutrient storage and turnover in organic layers under tropical montane rain forest in Ecuador
Authors: Wilcke W. , Yasin S. , Abramowski U. , Valarezo C. , Zech W.
Published: March 2003

In tropical montane forests nutrients released from the organic layers of the soil can supply a large part of the vegetation's requirements. We have examined concentrations, storage, and turnover times of nutrients in the organic layer and the fluxes of nutrients by the fall of small litter (leaves, seeds, flowers, small twigs, and plant debris that passed an opening of 0.3 m × 0.3 m) in such a forest in Ecuador. The times taken for litter to turn over were estimated by relating nutrient storage in the organic layer to rate of litterfall and by incubating samples in the laboratory. The organic layer had a thickness of 2–43 cm, a mass of 30–713 t ha−1, and a nutrient storage of 0.87–21 t N, 0.03–0.70 t P, 0.12–2.5 t K, 0.09–3.2 t Ca, and 0.07–1.0 t Mg ha−1. The pH (in H2O) ranged between 3.1 and 7.4 and was correlated with the concentrations of Ca and Mg (r= 0.83 and 0.84, respectively). The quantity of small litter (8.5–9.7 t year−1) and mean concentrations of nutrients in litter (19–22 g N, 0.9–1.6 g P, 6.1–9.1 g K, 12–18 g Ca, and 3.5–5.8 g Mg kg−1) were larger than in many other tropical montane forests. The mean turnover times of elements in the organic layer increased in the order, Mg (7.0 years) < Ca (7.9) < K (8.5) < P (11) < N (14) < S (15) when calculated as the quotient of storage in the organic layer to flux by litterfall; they were < 12 years for N, P, and S in the incubation experiment. Under optimum conditions in the laboratory, the mineralization of S was just as large as the S deposition by litterfall. In weakly acid soils Mn and Zn and in strongly acid soils Ca added in a nutrient solution were immobilized during incubation. Thus, lack of S, Mn, Zn, and Ca might limit plant growth on some soils.
Iron reduction and changes in cation exchange capacity in intermittently waterlogged soil
Authors: Favre F. , Tessier D. , Abdelmoula M. , Génin J. M. , Gates W. P. , Boivin P.
Published: March 2003

The long‐term effects of intermittent flooding on soil properties were studied in field experiments on a Vertisol cropped with rice in Senegal. The dominant clay minerals were smectite and kaolinite. When the soil was reduced after flooding, its cation exchange capacity (CEC) increased to twice that of its oxidized, unflooded state. Mössbauer spectroscopy showed an increase in smectite structural FeII upon reduction, which explained a part of the increase in CEC. The rest of the increase was attributed to the removal of iron oxyhydroxide coatings by reductive dissolution. The reduction and dissolution of oxides under the field conditions were substantiated by analysis of the surfaces of vermiculites buried in the Ap horizons of the cropped and the non‐cropped soils. The redox‐induced CEC changes were found to be reversible after 22 cycles of rice cropping. Nevertheless, the structural Fe and free Fe contents of the rice field Ap horizon were less than those of soil in uncropped neighbouring land, suggesting that inundation induced weathering and eluviation of the minerals. The observed changes in CEC and related redox reactions may substantially modify proton, anion and cation balances in intermittently flooded soils.
Quantification of pore structure and gas diffusion as a function of scale
Authors: Vogel H.‐J. , Cousin I. , Roth K.
Published: March 2003

The quantification of the spatial heterogeneity of soil structure is one of the main difficulties to overcome for an adequate understanding of soil processes. There are different competing concepts for the type of heterogeneity, including macroscopic homogeneity, discrete hierarchy or fractal. With respect to these different concepts we investigate the structure of the pore space in one single sample (4 × 103 mm3) by analysing basic geometric quantities of the pores > 0.3 mm within gradually increasing subsamples. To demonstrate the relation between geometrical and functional properties we simulate gas diffusion within the three‐dimensional pore space of the different subsamples. An efficient tool to determine the geometric quantities is presented. As a result, no representative elementary volume (REV) is found in terms of pore‐volume density which increases with sample size. The same is true for the simulated gas diffusion coefficient. This effect is explained by two different types of pores, i.e. big root channels and smaller pores, having different levels of organization. We discuss the different concepts of structural organization which may be appropriate models for the structure investigated. We argue that the discrete hierarchical approach is the most profitable in practice.
Pressure plate studies to determine how moisture affects access of bacterial‐feeding nematodes to food in soil
Authors: Yeates G.W. , Dando J. L. , Shepherd T. G.
Published: March 2003

Nematode activity in the soil depends on the presence of free water. We conducted pressure plate experiments to understand better how soil matric potential and structural degradation affect the population growth of three bacterial‐feeding nematodes (Cephalobus,Pristionchus,Rhabditis). We took undisturbed cores from six soils (sand, silt loam and silty clay loam with four management regimes), and removed all fauna from them. Ten or 30 nematodes were added, and pressures corresponding to soil matric potentials of −10, −33, −50, −100 or −1500 kPa were applied for 35 days. The nematodes were then counted. Significant reproduction of all bacterial‐feeding nematodes occurred when the diameters of water‐filled pores were approximately 1 μm. This confirms observations using repacked soils and field manipulations. Only forPristionchusdid declining populations match the reduction in total soil porosity related to intensification of land use on the silty clay loam. We had not expectedCephalobusto have the fastest increase in population of the three nematodes in intact soil cores, and our evidence questions the relative importance given to the three nematode families in soil processes. The differing rates of population increase of the three nematodes in the various soils reflect both habitable pore space and trophic interactions. This suggests that the very diversity of nematode assemblages is crucial in the resilience of biological soil processes. That water‐filled pores as small as 1 μm provide suitable spaces for sizeable populations of bacterial‐feeding nematodes accords with the observed migration of infective juveniles of trichostrongylid nematodes and mermithids in water films on herbage. Our results imply that assessment of the role of nematodes in soil processes may be a key to the understanding of biological interactions in water films, and the selection pressures on nematode morphology.
The relationship between copper accumulated in vineyard calcareous soils and soil organic matter and iron
Authors: Parat C. , Chaussod R. , Lévêque J. , Dousset S. , Andreux F.
Published: March 2003

The intensive use for over 100 years of copper sulphate (Bordeaux mixture) to fight mildew in vineyards has led to a substantial accumulation of copper (Cu) in surface soils. To assess the effects of such large concentrations, the surface soils of 10 Burgundy vineyards were sampled and analysed for total organic matter (carbon and nitrogen) and metal (copper and iron) contents. Physical (i.e. size fractionation) and chemical (sequential extraction) methods were used to determine the distribution of these elements. The most Cu‐contaminated plots showed the largest accumulation of organic carbon and Cu in the coarse sand and fine sand fractions. Copper was strongly correlated with organic carbon and organic nitrogen in the coarse sand fraction and with organic nitrogen in the fine sand fraction. Copper was also highly correlated with both Fe and organic nitrogen in the clay fraction but not significantly with organic carbon. The sequential extraction showed that Cu was bound mainly to the Fe oxides. However, in the most Cu‐contaminated plots, a part of added Cu was bound to organic matter. This study suggests that Cu protected indirectly the organic matter present in the coarse fractions against biodegradation, and therefore modified the distribution of organic carbon among the particle‐size fractions. Iron appeared as the main factor responsible for Cu accumulation in the clay fraction, mainly through inclusion of Cu in Fe oxyhydroxides and possibly in clay–humus complexes.
Fish and lamprey passage in a combined Denil and vertical slot fishway
Authors: LAINE  , KAMULA  , HOOLI
Published: March 2003

A fishway (fish pass), consisting of vertical slot and Denil sections, was constructed at the lowest dam on the River Kemijoki, northern Finland, in 1993. The river was one of the best salmon rivers in Europe until 1949, when the dam and the hydropower plant were completed close to the river mouth. From 1993 to 1995, nearly 1000 adult salmonids passed through the fishway despite heavy fishing below the dam. Of environmental variables measured, water temperature, headwater level, and discharge through the power plant in relation to season changes explained most of the variation in Baltic salmon, Salmo salar L., numbers. They had a minor effect on trout, Salmo trutta L. Migratory whitefish, Coregonus lavaretus (L.), entered the fishway but were not observed in its uppermost pool. River lamprey, Lampetra fluviatilis (L.), passed through the vertical slot section of the fishway after plastic bristles were fastened into the bottom of the slots.
Comparative life‐history characteristics of native and hatchery‐reared brown trout, Salmo trutta L., in a sub‐Alpine reservoir
Authors: Hesthagen T. , Flòystad L. , Hegge O. , Staurnes M. , Skurdal J.
Published: March 2003

Wild and non‐native hatchery‐reared brown trout, Salmo trutta L., released when 2 summers old, were caught in the littoral habitat of Vinstervatna Reservoir, southern Norway. Hatchery‐reared brown trout grew more slowly and had a smaller asymptotic length (293 ± 71 mm CL) than native fish (391 ± 56 mm CL). Hatchery‐reared brown trout also exhibited significantly shorter life spans than native fish. This category consisted mainly of individuals aged 2+ and 3+ years, and only 1.5% of the specimens were aged ≥5 years. The ages of the native fish in the sample were between 2 and 8 years, and the most abundant age groups of trout were 4+ and 5+ years. It is suggested that the differences in life‐history characteristics are related to adaptations by the native trout to the local environmental conditions. In this reservoir, which has a limited food supply as a result of water level fluctuations and a high level of inter‐ and intraspecific competition, environmental effects might be significant.