bluuebunny/crossref_metadata_2025 huggingface dataset:
The Rietveld method applied to the quantitative mineralogical and chemical analysis of a ferralitic soil
Authors: Weidler P. G. , Luster J. , Schneider J. , Sticher H. , Gehring A. U.
Published: March 2003

The analysis of X‐ray diffraction (XRD) patterns by the Rietveld method was tested for characterizing quantitatively the mineralogical composition of a ferralitic soil from southern Mali. Quantitative analysis of two samples from this soil revealed kaolinite and quartz as major components and smaller amounts of haematite, goethite and anatase. Despite a strong overlap of the peaks, precise and reliable cell parameters and Al for Fe substitutions were determined. The quantitative results of the Rietveld refinement were verified by chemical analysis. This comparison revealed a strong influence of sample preparation on the quantitative mineralogical analysis by XRD.
Nitrous oxide and methane fluxes from organic soils under agriculture
Authors: WILD  , KLEMISCH  , PFADENHAUER
Published: March 2003

Trace gas fluxes of N2O and CH4 were measured weekly over 12 months on cultivated peaty soils in southern Germany using a closed chamber technique. The aim was to quantify the effects of management intensity and of soil and climatic factors on the seasonal variation and the total annual exchange rates of these gases between the soil and the atmosphere. The four experimental sites had been drained for many decades and used as meadows (fertilized and unfertilized) and arable land (fertilized and unfertilized), respectively. Total annual N2O‐N losses amounted to 4.2, 15.6, 19.8 and 56.4 kg ha–1 year–1 for the fertilized meadow, the fertilized field, the unfertilized meadow and the unfertilized field, respectively. Emission of N2O occurred mainly in the winter when the groundwater level was high. At all sites maximum emission rates were induced by frost. The largest annual N2O emission by far occurred from the unfertilized field where the soil pH was low (4.0). At this site 71% of the seasonal variation of N2O emission rates could be explained by changes in the groundwater level and soil nitrate content. A significant relationship between N2O emission rates and these factors was also obtained for the other sites, which had a soil pH between 5.1 and 5.8, though the relation was weak (R2 = 15–27%). All sites were net sinks for atmospheric methane. Up to 78% of the seasonal variation in CH4 flux rates could be explained by changes in the groundwater level. The total annual CH4‐C uptake was significantly affected by agricultural land use with greater CH4 consumption occurring on the meadows (1043 and 833 g ha–1) and less on the cultivated fields (209 and 213 g ha–1).
Charge characteristics in relation to free iron and organic matter of soils from Bambouto Mountains, Western Cameroon
Authors: VAN RANST  , SHAMSHUDDIN  , BAERT  , DZWOWA
Published: March 2003

We have examined the charge characteristics, with special emphasis on the role of free Fe and organic matter, of humid tropical soils from Bambouto Mountains, Western Cameroon. The soils, which are formed from tuff, basalt and trachyte, are dominated by kaolinite and sesquioxides. The amounts of Fe oxides in them increase somewhat with depth. Open 2:1 phyllosilicates are present in trace amounts. The point of zero charge of the variable charge components, pH0, is around 4 in the topsoil (0–20 cm) and around 6 at 100–150 cm depth. In the subsoils, pH0 exceeds soil pH presumably because of large quantities of Fe oxides. Deferration increases both soil pH and pH0, but diminishes the anion exchange capacity. Oxides and oxyhydrates of Fe have positive surface charge, so their removal from the soils would result in overall loss of positive charge. Increases in soil pH would bring about an increase in the cation exchange capacity of the soils. Hence, management practices that reduce soil acidity should reduce loss of essential basic cations via leaching.
Analytical pyrolysis of a soil profile under Scots pine
Authors: DIJKSTRA  , BOON  , VAN MOURIK
Published: March 2003

The chemical properties of pine needle litter cause slow decomposition, which results in an accumulation of highly lignocellulosic material on the forest floor. Decomposition of organic matter is important for the nutrient turnover in pine forests on nutrient‐poor soils. We studied the biodegradation of needles in an organic layer focusing on the various stages of lignin degradation by fungi. Samples were obtained from pine needle litter and a stratified organic layer over nutrient‐poor sand under a 60‐year‐old Scots pine (Pinus sylvestris forest stand. Pyrolysis mass spectrometry (PyMS) and pyrolysis gas chromatography mass spectrometry (PyGCMS) were used to characterize the chemical composition of the needles and the soil. The pyrolysis data show that diterpenoid acids are a main component in fresh needles, but rapidly decrease in the organic layer of the soil, as a result of decomposition. The chemical composition of the soil profile is dominated by guaiacyl lignin and polysaccharides from needle litter. The hexose/pentose ratio increases with depth in the soil profile. The partial preservation of hexose polymers is the result of the preferential decomposition of pentose polymers by white‐rot fungi, and points to the input of microbially synthesized polysaccharides. Indications for the degradation of guaiacyl lignin are also found in the soil profile. Oxidative reactions by soil fungi result in a shortening of the side chain of the guaiacyl lignin derivatives and an increase of carbonyl and carboxyl groups. These degradational patterns of lignin in the soil profile under Scots pine are similar to those observed in lignin model compounds and wood lignin degraded by fungi under controlled laboratory conditions.
Phosphate rock dissolution and transformation in the rhizosphere of tea (Camellia sinensis L.) compared with other plant species
Authors: ZOYSA A. K. N. , LOGANATHAN P. , HEDLEY M. J.
Published: March 2003

Tea (Camellia sinensis L.) is generally grown in highly weathered acidic Ultisols of the humid tropics. The low pH, large P fixing capacity and moisture content of these soils favour the dissolution of phosphate rock. Plant species differ widely in their ability to take up P from phosphate rock, and we have compared phosphate mobilization in the rhizosphere of tea with that under calliandra (Calliandra calothyrsus L.), Guinea grass (Panicum maximum L.) and bean (Phaseolus vulgaris L.) by studying the changes in the concentration of P fractions at known distances from the root surface in an acidic (pH in water 4.5) Ultisol from Sri Lanka treated with a phosphate rock. Plants were grown in the top compartment of a two‐compartment device, comprising two PVC cylinders physically separated by a 24‐μm pore‐diameter polyester mesh. A planar mat of roots was formed on the mesh in the top compartment, and the soil on the other side of the mesh in the lower compartment was cut into thin slices parallel to the rhizosphere and analysed for pH and P fractions.

All plant species acidified the rhizosphere (pH [water] difference between bulk and rhizosphere soils was 0.17‐0.26) and caused more rock to dissolve in the rhizosphere (10–18%) than in the bulk soil (8–11%). Guinea grass was most effective, though the rate of acidification per unit root surface area was least (0.02μmol H+ cm−2) among the four species. Tea produced the largest rate of acidification per unit root surface area (0.08μmol H+ cm+2). All species depleted P extracted by a cation–anion exchange resin and inorganic P extracted by 0.1 M NaOH. All except tea depleted organic P extracted by 0.1M NaOH in the rhizosphere. The external P efficiencies (mg total P uptake) of Guinea grass, bean, tea and calliandra in soil fertilized with phosphate rock were 4.82 ± 0.42, 4.02 ± 0.32, 1.06 ± 0.02 and 0.62 ± 0.02, respectively, and the corresponding internal P efficiencies (mg shoot dry matter production per mg plant P) were 960 ± 75, 1623 ± 79, 826 ± 33 and 861 ± 44. This study showed that the various crops cultivated in tea lands differ in their rates of acidification, phosphate rock dissolution and P transformation in the rhizosphere. This requires testing under field conditions.
A comparison of aggregate stability and biological activity in earthworm casts and uningested soil as affected by amendment with wheat or lucerne straw
Authors: HAYNES R. J. , FRASER P. M.
Published: March 2003

The mechanisms responsible for stabilization of earthworm casts were investigated in a laboratory study. Earthworms (Aporrectodea caliginosa) were fed soil or soil amended with either ground wheat straw or lucerne hay. Cast material and uningested soil material were incubated for 56 days, and changes in aggregate stability (measured by wet sieving), soil biological activity and macronutrient availability were measured periodically. In general, aggregate stability and microbial biomass C tended to increase during the incubation for both cast and soil material, whereas hot‐water extractable carbohydrate content declined. For amended treatments, basal respiration rate and microbial metabolic quotient were large at the first sampling (7 days) but declined rapidly thereafter. There was a transitory increase in extractable P in fresh casts compared with uningested material, a sustained increase in mineral N concentrations but no change in exchangeable K content. For unamended treatments, the casts were less stable than soil material, but this difference diminished during incubation. Drying aggregates before analysing them did not reverse this trend. The casts contained more microbial biomass C than soil material did, but the basal respiratory rate, respiratory quotient and hot‐water extractable carbohydrate content were less. By contrast, for wheat‐ and lucerne‐amended treatments casts were more stable than soil material, and the microbial biomass was less at all sampling times. For wheat treatments, respiratory quotient and hot‐water extractable carbohydrate content were larger for cast than soil material, but the opposite was the case for lucerne treatments. We attribute the stability of casts in amended treatments to the intimate mixing of part‐decomposed organic fragments with comminuted soil particles, binding by microbial mucilage associated with the organic fragments and linking and binding by fungal hyphae.
Empirical modelling of the kinetics of phosphate sorption to macropore materials in aggregated subsoils
Authors: Hansen H. C. B. , Hansen P. E. , Magid J.
Published: March 2003

Preferential transport of phosphate through macropores increases the significance of phosphate sorption to macropore wall materials compared with bulk soil materials. Therefore we studied the kinetics of phosphate sorption to soil bulk materials from the Ap and Btg horizons, from the iron oxide‐poor (Albic) centres and from iron oxide‐rich (Red) exteriors of the fractures in a clayey pseudogley in batch at initial phosphate concentrations (P0) up to a maximum of 650 μm and at sampling times up to 7 days. Uptake of phosphate was least in the phosphate‐rich Ap, and the Albic material also adsorbed little. By contrast the Red material sorbed phosphate strongly. By plotting the logarithm of the solution phosphate concentration against log time, two or three different kinetic regions could be distinguished: a fast reaction within the first minute of reaction; a lag period at intermediate to large initial values of phosphate concentration (P0); and a steady slow reaction. The lag phase cannot be described satisfactorily by the well‐known adsorption models. The Langmuir equilibrium expression produced rather good fits at any fixed time of reaction, but the estimated adsorption maximum increased steadily with time. Empirical models were fitted to the data, among them a ‘lag‐linear’ model developed to include the lag phase. The relative contribution of the fast reaction to total adsorption during 7 days decreased from 50 to 80% at small P0 to less than 10% at large P0 values. The fraction of fast‐adsorbed phosphate followed the order Red > Btg > Albic > Ap regardless of P0; the slow reaction is, by a log–log rate, ranked Albic ≅  Btg > Red > Ap for P0 < 20 μm and Red > Btg > Albic > Ap at larger initial concentrations. The Albic material does not minimize the risk of phosphate leaching through macropores, as demonstrated by its small P sorption capacity, the relatively slow adsorption rate and its small actual P content.
The solubility characteristics of organic Al precipitates in allophanic Bs horizons could mimic those of Al hydroxides, and indicate the solubility of associated allophanes
Authors: Farmer V. C.
Published: March 2003

It is shown that Al‐humate and fulvate precipitates in Bs horizons of pH > 4.6 can be the source of the soluble aluminium which is rapidly released in equilibrium studies to give log10{Al3+} + 3pH values near 9.4 at 8°C, so that it is not necessary to postulate an anomalously reactive but sparingly soluble Al(OH)3 phase. These Al‐organic precipitates will have reached equilibrium in the natural soil environment with the more slowly reacting hydroxy‐aluminium precipitates present, including proto‐imogolite allophane, but can release Al3+ much more rapidly than the inorganic precipitates in laboratory equilibrations and soil leaching episodes that yield lysimeter waters. Equilibrium concentrations of Al reported in a range of Bs horizons indicate that the allophanes present are less soluble than proto‐imogolite sols prepared in the laboratory and matured for up to 2 years.
Two‐dimensional simulation of bromide transport in a heterogeneous field soil with transient unsaturated flow
Authors: Hammel K. , Gross J. , Wessolek G. , Roth K.
Published: March 2003

As a consequence of spatial heterogeneity, solute transport and associated phenomena of soil in the field are typically complex and often poorly described by current one‐dimensional models. Therefore, better descriptions should be obtained if the specific variation of the soil is explicitly accounted for. To test this hypothesis, we simulated the two‐dimensional transport of a bromide trace in pore‐water velocity fields which varied in both space and time. We used data obtained in a field experiment in which we studied bromide transport as input parameters and boundary conditions for the simulation. We conceptualized heterogeneity at two spatial scales. Large regions with constant spatial properties were defined by the measured geometry of the soil’s horizons. On these we superimposed small structures derived from a correlated random field of scaling factors and conditioned on measured hydraulic properties. Simulations with homogeneous and heterogeneous horizons show that both coarse and fine hydraulic variation contribute to characteristic experimental phenomena such as concentration ‘hot spots’, especially near irregularities of horizon boundaries, and early breakthrough of solute leading to large dispersion at the field scale. The comparison between simulation and experimental results demonstrates that these features are reproduced if local hydraulic variation is included in the description of the transport. As expected, the quantitative agreement is limited, since the concentration distribution is strongly sensitive to local hydraulic conditions which were only partly accounted for by the measurements.
Determination of moisture content in a deformable soil using time‐domain reflectometry (TDR)
Authors: Kim D. J. , Choi S. I. , Ryszard O. , Feyen J. , Kim H. S.
Published: March 2003

Time‐domain reflectometry (TDR) is being used increasingly for measuring the moisture content of porous media. However, successful application for measuring water in soil has been limited to non‐deformable soils, and it would be a valuable extension of the technique if it could be used for soils that shrink on drying. We have recently investigated its application to soils rich in clay and organic matter and peats. Here we propose a method for determining moisture content in deformable soils based on the relation between the dielectric constant, K, and the volumetric moisture content, Θ, measured by TDR.

Parallel TDR probes with a length of 15 cm and a spacing of 2 cm were placed horizontally in soil cores with a diameter of 20 cm and height of 10 cm taken from a forest. The soil is very porous with large proportions of both silt and clay. The sample weight and travel time of the electromagnetic wave guided by parallel TDR probes were simultaneously measured as a function of time, from saturation to oven‐dryness during which the core samples shrank considerably. Vertical and horizontal components of shrinkage were also measured to take the air‐exposed region of TDR probe into account in the determination of K. The effect of deformation on volumetric moisture content was formulated for two different expressions, namely actual volumetric moisture content (AVMC) and fictitious (uncorrected) volumetric moisture content (FVMC). The effects of air‐exposure and expressions of volumetric moisture content on the relation between K andΘ were examined by fitting the observations with a third‐order polynomial. Neglecting the travel time in the air‐exposed part or use of the FVMC underestimated the Θ for a given K. The difference was more pronounced between AVMC and FVMC than between two different dielectric constants, i.e. accounting for air‐exposure, Kac, and not accounting for air‐exposure, Kau. When the existing empirical models were compared with the fitted results, most underestimated the relation based on the AVMC. This indicates that published empirical models do not reflect the effect of deformation on the determination of Θ in our forest soil. Correct use of the Θ expression has more impact on determining moisture content of a deformable soil than the accommodation of travel time through the air‐exposed region of TDR probe.
Myriapod and isopod communities in soils contaminated by heavy metals in northern France
Authors: Grelle C. , Fabre M. ‐C. , Leprêtre A. , Descamps M.
Published: March 2003

Soil invertebrates suffer from contamination of the soil by heavy metals. We have studied the effects of contamination by cadmium, zinc and lead on their communities in soils in northern France by comparing polluted land with non‐contaminated sites. We have followed the seasonal variations and effects of soil properties. Saprophagous invertebrates (Diplopoda, Isopoda) and Chilopoda were sampled by pitfall‐trapping from February to November in fairly contaminated areas. In addition, a Berlese extraction of the litter in two very highly contaminated sites was conducted during autumn; animals were also trapped during June in the same locations. The most active period for myriapods was spring (April and May), whereas isopods were abundant from April to the end of summer. No clear relation was found relating dominant species or number of myriapods or isopods to concentration of heavy metal in the little‐contaminated soils. The dominant species seemed not to be related to pollution but to vegetation or soil characteristics. In the most contaminated sites, with metalliferous grassland and a thick undecomposed litter layer, a threshold in contamination values seemed to be reached: no isopods or millipedes were found, but only Chilopoda and Symphyla.
Effect of compaction on the porosity of a silty soil: influence on unsaturated hydraulic properties
Authors: Richard G. , Cousin I. , Sillon J. F. , Bruand A. , Guérif J.
Published: March 2003

Tillage and traffic modify soil porosity and pore size distribution, leading to changes in the unsaturated hydraulic properties of the tilled layer. These changes are still difficult to characterize. We have investigated the effect of compaction on the change in the soil porosity and its consequences for water retention and hydraulic conductivity. A freshly tilled layer and a soil layer compacted by wheel tracks were created in a silty soil to obtain contrasting bulk densities (1.17 and 1.63 g cm−3, respectively). Soil porosity was analysed by mercury porosimetry, and scanning electron microscopy was used to distinguish between the textural pore space and the structural pore space. The laboratory method of Wind (direct evaporation) was used to measure the hydraulic properties in the tensiometric range. For water potentials < −20 kPa, the compacted layer retained more water than did the uncompacted layer, but the relation between the hydraulic conductivity and the water ratio (the volume of water per unit volume of solid phase) was not affected by the change in bulk density. Compaction did not affect the textural porosity (i.e. matrix porosity), but it created relict structural pores accessible only through the micropores of the matrix. These relict structural pores could be the reason for the change in the hydraulic properties due to compaction. They can be used as an indicator of the consequences of compaction on unsaturated hydraulic properties. The modification of the pore geometry during compaction results not only from a decrease in the volume of structural pores but also from a change in the relation between the textural pores and the remaining structural pores.
Laser‐induced breakdown spectroscopy for soil diagnostics
Authors: Bublitz J. , Dölle C. , Schade W. , Hartmann A. , Horn R.
Published: March 2003

Laser‐optical measurements and fibre optics are potentially attractive tools for applications in soil science because of their great sensitivity and selectivity and their capabilities for on‐line and in situ analysis. We have investigated laser‐induced breakdown spectroscopy (LIBS) for the quantitative detection of metal ions on the surface of natural soil samples from two sites (Hohenschulen and Oderbruch, Germany). The LIBS technique allows the spatially resolved investigation of adsorption and desorption effects of ions in soil. A frequency doubled (532 nm) and Q‐switched Nd:YAG laser with a pulse duration of 8 ns is focused on the soil surface and induces a plasma. Typical power densities are 150 mJ mm−2. The plasma emission is recorded in time and spectrally resolved by a gateable optical multichannel analyser (OMA). A delay time of about 500 ns between laser pulse and OMA gate was used to resolve single atomic and ionic spectral lines from the intense and spectrally broad light that is emitted by the plasma itself. The dependency of the LIBS signal of a single spectral line on the amount of water in the sample is investigated in detail. The results indicate that quenching of water in the plasma plume reduces the line intensities, while the interaction with aquatic colloids increases the intensity. The two processes compete with each other, and a non‐linear correlation between measured line intensities and the amount of water in the sample is obtained. This is verified by a simple computer simulation and has to be taken into account for the quantitative interpretation of LIBS signals, e.g. when absolute concentrations are estimated. In the present investigation natural calcium concentrations < 2 μg kg−1 were measured with the LIBS technique in the samples for the two test sites. In addition, measurements were made with dry and water‐saturated BaCl2 mixed soil samples, and no significant difference in the detection limit for barium was obtained.
Effect of sodium adsorption ratio and electrolyte concentrations on the saturated hydraulic conductivity of clay–sand mixtures
Authors: Aringhieri R. , Giachetti M.
Published: March 2003

We did flow experiments under saturated conditions on homoionic (Na+) kaolin–sand and illite–sand systems, containing 5, 10, and 15% clay, to validate a drainage model, and evaluate the effect of the different chemical composition of the percolating solutions on the hydraulic properties of the systems. Column drainage experiments, under a constant hydraulic head, were carried out using solutions with two sodium adsorption ratios (SAR 0 and ∞) and three electrolyte concentrations (10−2, 10−3, and 10−4 m). We calculated the saturated hydraulic conductivity, Ksat, of the systems using Darcy's law when these showed linear relationships between effluent volume and time. The drainage model was applied to characterize the flow of non‐steady‐state drainage of solutions through the porous systems. This model describes and characterizes quantitatively the drainage of solutions from soil columns that vary in intrinsic permeability, k, because of structural modifications that occur within the solid matrix of the systems. For both the systems investigated we always observed a decrease in the flow rate as electrolyte concentration decreased, or clay percentage increased. Under the same conditions the flow was faster for the kaolin system than the illite system, even though kaolin dispersed more than illite. Non‐linear relations were also observed at the smallest electrolyte concentration (10−4 m). In all cases, the equations proposed correlated well with the experimental data, confirming the soundness of the model. The flow rates observed in the experiments at SAR ∞ were unexpectedly greater than those observed at SAR 0, for the two systems, when leaching with solutions at 10−3 and 10−4 m. The values of pH and electrical conductivity of the eluates support the idea that the clay hydrolysis occurred during the saturation and, to a lesser extent, during the leaching phase of the flow.
Sources and composition of soil organic matter fractions between and within soil aggregates
Authors: Six J. , Guggenberger G. , Paustian K. , Haumaier L. , Elliott E. T. , Zech W.
Published: March 2003

It is generally accepted that particulate organic matter derives from plants. In contrast, the enriched labile fraction is thought by many to derive from microbes, especially fungi. However, no detailed chemical characterization of these fractions has been done. In this study, we wanted to assess the sources (plants or microbes; fungi or bacteria) and degree of microbial alteration of (i) three particulate organic matter fractions – namely the free light fraction (1.85 g cm−3), the coarse (250–2000 μm) and the fine (53–250 μm) intra‐aggregate particulate organic matter fractions – and of (ii) three density fractions of fine‐silt associated carbon – namely < 2.0, 2.0–2.2 (i.e. enriched labile fraction) and > 2.2 g cm−3– by analysing the amino sugars, by CuO oxidation analyses, and by 13C‐, 1H‐ and 31P‐NMR analyses. Macroaggregates (250–2000 μm) were separated by wet‐sieving from a former grassland soil now under a no‐tillage arable regime. The three particulate organic matter fractions and the three density fractions were isolated from the macroaggregates by a combination of density flotation, sonication and sieving techniques. Proton NMR spectroscopy on alkaline extracts showed that the enriched labile fraction is not of microbial origin but is strongly degraded plant material that is enriched in aliphatic moieties partly bound to aromatics. In addition, the enriched labile fraction had a glucosamine content less than the whole soil, indicating that it is not enriched in carbon derived from fungi. Decreasing yields of phenolic CuO oxidation products and increasing side‐chain oxidation in the order coarse intra‐aggregate particulate organic matter < fine inter‐aggregate particulate organic matter < fine‐silt fractions indicate progressive alteration of lignin as particle size decreases. The light fraction was more decomposed than the coarse inter‐aggregate particulate organic matter, as indicated by (i) its larger ratio of acid‐to‐aldehyde of the vanillyl units released by CuO oxidation, (ii) the smaller contribution of H in carbohydrates to total extractable H as estimated by 1H‐NMR spectroscopy, and (iii) a larger contribution of monoester P to total extractable P in the 31P‐NMR spectra. In conclusion, the four fractions are derived predominantly from plants, but microbial alteration increased as follows: coarse inter‐aggregate particulate organic matter < light fraction ≈ fine inter‐aggregate particulate organic matter < enriched labile fraction.
The dynamics of organic matter in rock fragments in soil investigated by 14C dating and measurements of 13C
Authors: Agnelli A. , Trumbore S. E. , Corti G. , Ugolini F. C.
Published: March 2003

Rock fragments in soil can contain significant amounts of organic carbon. We investigated the nature and dynamics of organic matter in rock fragments in the upper horizons of a forest soil derived from sandstone and compared them with the fine earth fraction (<2 mm). The organic C content and its distribution among humic, humin and non‐humic fractions, as well as the isotopic signatures (Δ14C and δ13C) of organic carbon and of CO2 produced during incubation of samples, all show that altered rock fragments contain a dynamic component of the carbon cycle. Rock fragments, especially the highly altered ones, contributed 4.5% to the total organic C content in the soil. The bulk organic matter in both fine earth and highly altered rock fragments in the A1 horizon contained significant amounts of recent C (bomb 14C), indicating that most of this C is cycled quickly in both fractions. In the A horizons, the mean residence times of humic substances from highly altered rock fragments were shorter than those of the humic substances isolated in the fine earth. Values of Δ14C of the CO2 produced during basal respiration confirmed the heterogeneity, complexity and dynamic nature of the organic matter of these rock fragments. The weak 14C signatures of humic substances from the slightly altered rock fragments confirmed the importance of weathering in establishing and improving the interactions between rock fragments and surrounding soil. The progressive enrichment in 13C from components with high‐14C (more recent) to low‐14C (older) indicated that biological activity occurred in both the fine and the coarse fractions. Hence the microflora utilizes energy sources contained in all the soil compartments, and rock fragments are chemically and biologically active in soil, where they form a continuum with the fine earth.
The soil skeleton, a forgotten pool of carbon and nitrogen in soil
Authors: Corti G. , Ugolini F. C. , Agnelli A. , Certini G. , Cuniglio R. , Berna F. , Fernández Sanjurjo M. J.
Published: March 2003

To evaluate the contribution of rock fragments to the soil’s total carbon content, the soil of 26 sites, ranging from the Canadian Arctic to the Jordan desert, was analysed for the content of organic C and total N in both fine earth and skeleton fractions. The soils, uncultivated and cultivated, are derived from 11 parent materials: sandstone, mica‐schist, granite, gneiss, basaltic pyroclastites, trachyte, dolomite, beach deposits, clay schist, marl and serpentinite. For each soil horizon the contents of fine earth and skeleton were determined by volume. Both fractions were analysed for bulk density, total and organic C and total N. Our results indicate that rock fragments contain amounts of C and N that depend on the nature of the parent material and on its resistance to the weathering processes. The C and N of both fine earth and skeleton were used to calculate the contents of these elements for three depths. At each depth, the skeleton contributes C and N to the soil depending on its abundance. We conclude that the contribution of the rock fragments to the soil C and N cannot be predicted from the soil taxa, but can from the parent material. Calculations that exclude C and N of the skeleton could lead to errors in the estimates of these two elements in soils.
Organic matter in particle‐size fractions from A and B horizons of a Haplic Alisol
Authors: Schmidt M. W. I. , Kögel‐ Knabner I.
Published: March 2003

The organic matter in soils may be stabilized by its interactions with minerals. We have studied such interactions in a Haplic Alisol under forest in which clay and organic matter have migrated from an eluvial A horizon to accumulate in an illuvial B horizon. We have tried to trace the fate of organic matter in these horizons (Ah and Bvt) by determining clay mineralogy, carbon and nitrogen content, hydrolysable amino acids, lignin signature by alkaline CuO oxidation and carbon species by13C CPMAS NMR of bulk soils and particle‐size fractions. In both horizons, most of the organic matter was present in O–alkyl and methylene structures, each contributing one‐third to the bulk organic matter. In the Ah horizon the ratios of carbon‐to‐nitrogen, and yields for lignin and hydrolysable amino acids decreased as the particle‐size class decreased, but side‐chain oxidation of lignin compounds increased with decreasing particle size. In contrast to previous observations, the proportions of O–alkyl carbon increased as particle size decreased, constituting a major proportion of the organic carbon in the clay‐size fractions from both the Ah and Bvt horizons (≥ 38%), while proportions of methylene carbon decreased. Illite was the dominant mineral in the fraction ≤ 6 μm, whereas the mobile fine clay fraction (<0.2 μm) was rich in smectites – minerals with large surface areas. Our results support the hypothesis that potentially labile organic matter, such as O–alkyl carbon typically present in polysaccharides, may be stabilized against further degradation in organomineral complexes.
Defining the relation between soil water content and net nitrogen mineralization
Authors: Paul K. I. , Polglase P. J. , O'Connell A. M. , Carlyle J. C. , Smethurst P. J. , Khanna P. K.
Published: March 2003

Simulation models of net mineralization of nitrogen (N) in soil need to be able to incorporate the effect of soil water. Our objective was to identify and define the best way of expressing soil water and its effect on net mineralization across a range of soil types. We collated data from 12 laboratory incubation studies, including a total of 33 different soils, where rates of net mineralization of N were determined from the net accumulation of mineral N under a range of water contents at near‐optimal temperatures. Measurements of water potential and limits of water content observed in the field were available for most of these soils. The percentage of pore space filled with water was estimated from measurements of soil bulk density. We found that relative water content, particularly when expressed relative to an upper and lower limit of water content observed in the field, was the best descriptor for net mineralization. The next best descriptions were soil water potential, water content relative to the optimal water content for mineralization, and percentage of pore space filled with water, with water content alone being poor. Although various functions may be used to describe the relation between relative water content and net mineralization of N, an equation for a sigmoidal curve provided the best fit, and explained 78% of the variation.
Movements of two strains of radio tagged Altlantic salmon, Salmo salar L., smolts through a reservoir
Authors: Aarestrup K. , Jepsen N. , Rasmussen G. , Òkland F.
Published: March 2003

Smolt migration through a shallow and turbid hydro‐reservoir in a major Danish river system was investigated using radiotelemetry. Hatchery‐reared 1+‐year‐old Atlantic salmon, Salmo salar L., smolts of equal size from two different non‐native strains were radio‐tagged and followed during their downstream migration through the 12‐km‐long reservoir. A total of 50 salmon smolts, 25 of Swedish (Øtran River) and 25 of Irish (Burrishoole River) origin, were surgically implanted with miniature radiotransmitters. The tagged smolts were tracked daily over a 3‐week period in May 1996. The Øtran smolts initiated migration first (P < 0.001), moved faster (P < 0.01), were delayed less when passing a culvert (P < 0.001) and were more successful in moving through the reservoir than the Burrishoole smolts. The observed differences in migratory behaviour are interpreted as evidence of a genetic component influencing smolt migration.
Factors influencing the abundance of the common bully, Gobiomorphus cotidianus McDowall, in small, North Island, New Zealand, lakes
Authors: Rowe D. K.
Published: March 2003

Adult common bullies, Gobiomorphus cotidianus McDowall, are small (total length =  30–120 mm), benthic fish commonly found in the littoral zones of New Zealand lakes where they are a major prey species for trout and eels. Differences in their relative abundance (CPUE) were determined between 21 shallow North Island lakes. Mean CPUE ranged from 2 to >  1000 fish net− 1 night− 1 and was inversely related to water transparency. The abundance of bullies was not reduced in lakes containing rainbow trout, Oncorhynchus mykiss (Walbaum), but was reduced in all lakes containing self‐recruiting populations of eels, Anguilla spp. Mean densities of planktonic larval bullies in the limnetic zone were also inversely related to water transparency. Since low water transparency is related to increased trophic status for these lakes, the abundance of bullies is likely to be related to lake productivity, rather than turbidity.
An index for the management of South African estuaries for juvenile fish recruitment from the marine environment
Authors: Quinn N. W. , Breen C. M. , Whitfield A. K. , Hearne J. W.
Published: March 2003

The release of fresh water from major impoundments to meet the requirements of estuaries has become a recognized need and methodologies to define appropriate release strategies have become an urgent priority in some parts of the world. A recruitment index for juvenile marine fish is presented, based on information relating to the preferred recruitment periods for 27 species, as well as the extent of dependency of these species on estuaries. The status of the estuary mouth (i.e. open or closed) and the longitudinal salinity differences (i.e. the difference between the salinity at the estuary head and the mouth) in the estuary are obtained from a hydrodynamic model of the estuary. The recruitment index integrates this information to provide an indication of potential recruitment (or recruitment opportunity). This index was applied in a case study of the Great Brak Estuary, South Africa, and a distinct decrease in the recruitment index was associated with a reduction in freshwater inflow. In the estuary modelled, annual run‐off could be halved without an appreciable decrease in the fish recruitment index (FRI), but with a potentially sharp decline in fish recruitment thereafter. While the index represented recruitment opportunity rather than actual recruitment, it does at least provide an indication of where ecological risk is likely to increase substantially. Since the index integrates the current understanding with respect to the key processes which regulate recruitment of juvenile marine fish into estuaries, it is suggested that it has the potential to fulfil a vital role in identifying appropriate freshwater release policies for impoundments in South Africa.
Impacts of long‐term changes in fishery management on the trophic level water quality in Czech fish ponds
Authors: Pechar L.
Published: March 2003

The management of Czech fish ponds changed little from the Middle Ages until the end of the nineteenth century. The intensification of fish production was initiated during the first half of the twentieth century. During the 1930s, liming and manuring of the ponds became common. A greater density of stocking led to the use of artificial feeds in the form of pellets and grain. These changes in pond management have led to an increase in fish production from ≈ 50 to > 500 kg ha−1 year−1 over the last 5 decades. At the same time, the quality of the water and sediments has been deteriorating, and the functioning of the pond ecosystem has been disturbed. There are now massive blooms of phytoplankton, especially cyanobacteria, accompanied by great fluctuations in the oxygen concentration and pH. Data collected since 1925, when systematic research on the ponds started, allow the mechanisms responsible for the changes to be traced.
Predation by seals on salmonids in two Scottish estuaries
Authors: Carter T. J. , Pierce G. J. , Hislop J. R. G. , Houseman J. A. , Boyle P. R.
Published: March 2003

Detailed observations of the behaviour of harbour seals, Phoca vitulina L., at sites within the estuaries of the Rivers Dee and Don, in north‐eastern Scotland, were made over two full years between 1993 and 1996. Small numbers of grey seals, Halichoerus grypus Fab., were also present. The presence of seals within the estuaries was strongly related to season, with maximum numbers observed in winter and early spring; seals were virtually absent in June and July. The River Don was used largely as a haul‐out site, while the River Dee was used predominantly as a foraging site, although it was not possible to determine whether the same seals were using the two estuaries. More seals were hauled‐out on the River Don during twilight and dark than in daylight. The seals were observed to eat mostly salmonids, Salmo salar L. and S. trutta L., unidentified roundfish and flounder, Pleuronectes flesus L. The otoliths identified in scats collected at the mouth of the River Don belonged to marine species indicating that the seals were also feeding outside the estuaries. A minimum estimate is given of the numbers of large salmonids eaten in each river during the course of the year. Although no information was available on the numbers of salmonids using the rivers or the reproductive status of the fish eaten by the seals, as a cause of mortality, seal predation on large salmonids in estuaries is apparently an order of magnitude less important than mortality caused by angling within the river.
Fixed location hydroacoustic monitoring of fish populations in the tidal River Hull, north‐east England, in relation to water quality
Authors: Peirson G. , Frear P. A.
Published: March 2003

Abstract  Fixed location hydroacoustic fish monitoring was carried out at a series of sites in the tidal River Hull, north‐east England, in July 1996 during periods of moderate freshwater flows and spring tides. This was followed by a corresponding series during a period of lower freshwater flows and spring tides in autumn 1996. The surveys indicated substantial numbers of fish living upstream and downstream of a depleted oxygen zone which exists in the tidal Hull. Conditions in this zone of poor water quality deteriorated further during low flow periods due to reduced dilution of effluents. Fish populations moved with the tide apparently in response to gradients of dissolved oxygen and salinity. Under conditions of low freshwater flow and high tides, gradients of salinity and oxygen were steeper and fish responses appeared more marked: at higher salinities, the response to increasing salinity overrode the response to decreasing oxygen availability.
Effects of colony location and nekton abundance on the at‐sea distribution of four seabird species
Authors: PARRISH JULIA K. , LEMBERG NORM , SOUTH‐ORYSHCHYN LAURA
Published: March 2003

Although seabirds are locally superabundant in the vicinity of breeding colonies, abundance farther offshore is patchy in both space and time. The present study examines the fine‐scale (i.e. 1 km unit) distribution and abundance of four seabird species as a function of distance from a breeding colony (for three of the four species) and nekton density determined hydroacoustically. We found that density of the breeding species was significantly associated with nekton density, after controlling for island effects. In addition, nekton density associated with foraging aggregations of seabirds was significantly higher than that under resting aggregations. These results provide some of the clearest evidence of seabird‐nekton association, albeit on an extremely close spatial scale.
Distribution of minke whales in the Bellingshausen and Amundsen Seas (60°W–120°W), with special reference to environmental/physiographic variables
Authors: Kasamatsu Fujio , Ensor Paul , Joyce Gerald G. , Kimura Noritugu
Published: March 2003

The relationship between the distribution of minke whales (Balaenoptera acutorostrata) in the Bellingshausen and Amundsen Seas (longitude between 60°W and 120°W), and environmental and physiographic variables (sea‐surface temperature, sea‐ice extension, and sea‐floor‐slope type), was studied to determine whether these environmental and physical factors affect the distribution and density of minke whales. The analysis was based on sightings data obtained from the 1989/90 and 1982/83 IWC/IDCR cruises. The mean sea‐surface temperatures for comparable areas were significantly higher in 1989/90 (2.04°C) than in 1982/83 (1.12°C), and the area where the sea‐surface temperature was greater than 1°C in the 1989/90 study was approximately twice that of the 1982/83 study. Additionally, during the surveys, the extent of the sea ice in 1989/90 was less than that in 1982/83, with the mean ice edge about 92.6 km (50 nautical miles; 1 nautical mile ≈1.852 km) farther south in 1989/90 than in 1982/83. This is consistent with the sea ice extent observed in winter, when the sea ice extent was less in 1989 than in 1982. The distribution of minke whales was substantially different between the two surveys, with the density and abundance of minke whales being greater in 1982/83 than in 1989/90. The warmer sea‐surface temperatures, fewer cold‐water intrusions, and the smaller extent of sea ice in 1989/90 may be related to the difference in distribution of minke whales from 1982/83, possibly owing to the shift in availability of prey.
Acoustic approaches to remote species identification: a review
Authors: Horne John K.
Published: March 2003

Noninvasive species identification remains a long‐term goal of fishers, researchers, and resource managers who use sound to locate, map, and count aquatic organisms. Since the first biological applications of underwater acoustics, four approaches have been used singly or in combination to survey marine and freshwater environments: passive sonar; prior knowledge and direct sampling; echo statistics from high‐frequency measures; and matching models to low‐frequency measures. Echo amplitudes or targets measured using any sonar equipment are variable signals. Variability in reflected sound is influenced by physical factors associated with the transmission of sound through a compressible fluid, and by biological factors associated with the location, reflective properties, and behaviour of a target. The current trend in acoustic target identification is to increase the amount of information collected through increases in frequency bandwidth or in the number of acoustic beams. Exclusive use of acoustics to identify aquatic organisms reliably will require a set of statistical metrics that discriminate among a wide range of similar body types at any packing density, and incorporation of these algorithms in routine data processing.
Pacific herring,Clupea pallasi, recruitment in the Bering Sea and north‐east Pacific Ocean, I: relationships among different populations
Authors: Williams Erik H. , Quinn, II Terrance J.
Published: March 2003

We examined recruitment and average weight‐at‐age time series for Pacific herring (Clupea pallasi) populations from the Bering Sea and north‐east Pacific Ocean to determine similarities. Statistical correlation and multivariate clustering methods indicated Pacific herring populations form large‐scale groups. Large year classes occur synchronously among several Pacific herring populations. Multivariate cluster analyses of recruitment and weight‐at‐age data indicated that Bering Sea herring populations are distinct from north‐east Pacific Ocean populations. Within the NE Pacific Ocean, there appear to be three groups of herring populations: a British Columbia group, a south‐east Alaska coastal group, and an outer Gulf of Alaska group. Jackknife and randomization tests indicate these groups are robust and not the result of random chance. Deviations from observed herring population groups were examined for indications of anthropogenic perturbations. The Prince William Sound herring populations did not show any strong deviations corresponding to the oil spill of 1989. There might not yet be enough data since the spill to detect changes in the recruitment or weight‐at‐age data since that time, particularly if oil spill effects were concentrated on the early life history stages.