bluuebunny/crossref_metadata_2025_split huggingface dataset:
Signatures of lipid assemblages in soils under continental Mediterranean forests
Authors: ALMENDROS G. , SANZ J. , VELASCO F. 
Published: August 2005

SummaryThe analysis of free lipids in 12 soils from three representative types of Mediterranean forest has been carried out in an attempt to describe diagnostic molecules reflecting differences between the ecosystems and the intensity of the soil organic matter turnover. The study centred on the analysis by gas chromatography–mass spectrometry of the soil compounds extracted with petroleum ether from soils in central Spain, developed under monospecific formations of stone pine (Pinus pined), evergreen oak (Quercus rotundifolia) and Spanish juniper (Juniperus thurifera), the lipid extracts from their leaves also being analysed as reference material.The comparison between the distribution patterns of alkanes and fatty acids in plant lipids and the corresponding soil lipids was used to assess the extent to which the former accumulate in soil or are substituted by other biogenic or diagenetic homologues. In general, the alkane patterns showed the greatest variation in soils under oak, and the differences between lipid patterns in plant and soil were greatest in the juniper forests. As indicators of the vegetation type, the soil fatty acids had little value.Up to 60 major cyclic compounds were identified, including mainly di‐ and sesquiterpenes, in addition to some monoterpenes and nonterpenic naphthalenes and decalins. Of these major constituents, 33 compounds were found in soil but were not present in plant extracts, and 18 compounds were identified in plants but were not in the soils. The results suggest an arrangement of the soil samples based on the composition of the signature lipid assemblages.
Hyperfine splitting in the electron spin resonance solution spectra of humic substances
Authors: CHESHIRE M.V. , McPHAIL D.B. 
Published: August 2005

SummaryHumic substances contain significant quantities of free radicals which have important functions in many biological processes in soil involving electron transfer. Such radicals may be detected by electron spin resonance spectroscopy in both solid and solution state and are usually reported as giving a single unstructured peak. Humic acids from a range of soil types varying in parent material and pH have been examined by electron spin resonance spectroscopy of their solutions in 0.1 m KOH. Spectra with an effective g‐value typical of an organic free radical were obtained. Observation of hyperfine structure was highly dependent on the instrument settings used. It was present at a modulation amplitude of 0.0142 mT, but not at 0.101 mT. Similarly, there was a reduction in resolution as microwave power was increased from 0.505–20 mW. This may explain the inability of some investigators to observe structure in soil humic acids. Resolution of hyperfine features was greatly enhanced by recording spectra in the second derivative mode. Using appropriate instrument settings all the humic acids showed hyperfine structure, although the intensity of these components varied by a factor of 100, being much greater in humic acid from highly acidic soils.
The 14C age and residence time of organic matter and its lipid constituents in a stagnohumic gley soil
Authors: BOL R. , HUANG Y. , MERIDITH J.A. , EGLINTON G. , HARKNESS D.D. , INESON P. 
Published: August 2005

SummaryA combination of radiocarbon (14C) dating and biomarker analyses of the aliphatic hydrocarbons in soil lipids is proposed as a novel and improved method for studying the environmental history of peaty soils. The radiocarbon concentration of unfractionated bulk organic matter, hydrolysed soil residues and two lipid fractions (the aliphatic hydrocarbons and carboxylic acids) recovered from a stagnohumic gley soil, were compared using AMS (accelerator mass spectrometry) and radiometric 14C dating techniques. The radiocarbon ages recorded by the aliphatic hydrocarbon fractions were consistently older than those measured from the unfractionated soil, and were in most cases older than the residues remaining after acid hydrolysis. This pattern was observed at three different depths in the soil profile. The apparent age difference between the hydrocarbon fraction and its unfractionated substrate increased with depth. An abundance of long–chain n–alkanes, similar to those found in higher plant waxes, characterized the aliphatic hydrocarbon fraction from the deepest soil (at 21.5–24.5–cm depth). The radiocarbon age of this basal organic component (13470± 170 years bp) indicated that it derived from the initial re–establishment of vegetation on the local deglaciated landscape with the onset of the Windermere Interstadial (c. 14000–13000 14C years bp). Bulk organic detritus within the basal horizon dated at some 3000 years younger, and presumably as a result of the downward penetration and retention of some mobile organic residues produced later in the development of the soil profile. The survival and apparent stratigraphical stability of these recoverable aliphatic hydrocarbons provides the opportunity, via the development of AMS dating, to measure an unambiguous radiocarbon age for the origin of organic residues retained in soils and sediments.
Turnover of clay‐associated organic nitrogen in the different aggregate‐size classes of a cultivated silty loam
Authors: BALABANE M. 
Published: August 2005

SummarySoil aggregates are known to protect organic matter against microbial attack, and thereby stabilize it. The scale at which aggregation is effective and the degree of control it exerts on organic matter transformations are not well known. I investigated whether rapid and slow pools of organic nitrogen bound to the <2‐μm clay fraction could be related to different locations of the clay fraction in the soil structure. Dry aggregates were separated from soil to which 15N had been added for 4 years in a field experiment. Soil samples were at maximal immobilization of a labelled inorganic N dressing, and after 1 and 3 years of the beginning of the remineralization phase. Clay‐sized particle fractions (< 2 μm) were.separated from the different aggregate‐size classes, and their total C and N contents, and 15N isotopic excess, were determined. It seems that recently immobilized N associated with the clay fraction was rapidly sequestered in microaggregates (< 0.1 mm). The results also suggest a relation between the fast decay of part of the clay‐associated N and its location on the macroaggregate scale (>0.1 mm) of soil structure.
Changes in chemical properties of organic matter with intensified rice cropping in tropical lowland soil
Authors: OLK D.C. , CASSMAN K.G. , RANDALL E.W. , KINCHESH P. , SANGER L.J. , ANDERSON J.M. 
Published: August 2005

SummaryRice systems in Asia have intensified rapidly in the past 30 years, and significant areas of irrigated lowland rice are now supporting two or three rice crops per year. Our objective was to compare the chemical composition of soil organic matter (SOM) from four fields with different histories of rice cropping intensity and soil submergence: (i) a single‐crop rainfed, dryland rice system without soil submergence, (ii) an irrigated rice and soybean rotation, and irrigated (iii) double‐ or (iv) triple‐crop rice systems in which soil remains submerged during much of the year. In all four soils, extracted mobile humic acid (MHA) and calcium humate (CaHA) fractions were of modern age by 14C‐dating, and represented about 20% of total N and organic C. The MHA was enriched in N and hydrolysable amino acids (AA) compared with CaHA in all soils. With increased frequency of irrigated rice cropping, however, there was a large increase in phenolic content of SOM. We speculate that slower lignin decomposition caused by deficiency of O2 in submerged soil leads to incorporation of phenolic moieties into young SOM fractions. The increased phenolic character of these fractions may influence N cycling and the N supplying capacity of lowland soils supporting two or three annual crops of irrigated rice.
Field evaluation of models of denitrification linked to nitrate leaching for aggregated soil
Authors: VINTEN A.J.A. , CASTLE K. , ARAH J.R.M. 
Published: August 2005

SummaryDynamic simulation models of the nitrogen cycle are an important aid for predicting the effect of land management on nitrate concentration in ground and surface waters. These models often neglect, or treat in a highly empirical way, the process of denitrification. The solute leaching model SLIM, suitable for use in aggregated soil, was linked to two alternative denitrification submodels ('simple structure'and ‘aggregate assembly’ treatments). The linked models can be used in dynamic simulation of the fate of nitrate in soil. The models were calibrated using water release and soil respiration data from two field sites (a clay loam and a sandy loam). The fate of Br−1and 99 atom percentage15NO−3tracers on drained plots was measured at these sites. Both models predicted less denitrification from plots receiving small inputs of fresh organic residue than was actually lost; both did better where residue inputs were large. The ‘aggregate assembly’ model predicted short‐term losses immediately after incorporation of residues more successfully than did the ‘simple structured’ model. The simulated dynamics of denitrification during the autumn and winter in the two models were also very different. Overall N balances were better predicted in the clay loam than the sandy loam. Possible reasons for discrepancies between model output and real data include immobilization (especially when large inputs of residues were incorporated), denitrification in the subsoil, and an inadequate description of the way in which degradation of organic matter depends on temperature.
Improving the calibration of dielectric TDR soil moisture determination taking into account the solid soil
Authors: MALICKI M.A. , PLAGGE R. , ROTH C.H. 
Published: August 2005

SummaryThe influence of soiľs solid phase on the dielectric constant of the soil over a range of moisture contents has been studied. Samples of soil, soil‐like, and also other porous materials were analysed using Time Domain Reflectometry (TDR) to determine the contribution of bulk density and porosity to the function that relates dielectric constant to water content.The study showed that bulk density, and thus also porosity, substantially affects the relation between dielectric constant and water content. Two equivalent, empirical, normalized conversion functions were found, one accounting for bulk density and the other for porosity. Each of them reduced the root mean square error of the dielectric TDR determinations of moisture to 0.03, regardless of the materialľs bulk density and porosity.
A simple model of soil organic matter complexation to predict the solubility of aluminium in acid forest soils
Authors: WESSELINK L.G. , VAN BREEMEN N. , MULDER J. , JANSSEN P.H. 
Published: August 2005

SummaryA simple equilibrium model for competitive binding of Al and protons to soil organic matter shows that Al activities in soil solutions of acid mineral soils are controlled by complexation reactions with soil organic matter. The model successfully explains the relation between pH and the activity of dissolved Al in several forest soils. Furthermore, we found evidence that pools of organically bound Al may be depleted fairly quickly. Kinetically controlled dissolution of inorganic soil Al compounds, which may be considerable, is the main cause for the re‐supply of the organically bound Al in the soil. The previously reported decrease in Al solubility that accompanies measured decline in organically bound Al in three Dutch soils was found quantitatively consistent with the model for organically bound Al proposed here.
Comparison of chemical composition of soil solutions collected by zero‐tension plate lysimeters with those from ceramic‐cup lysimeters in a forest soil
Authors: MARQUES R. , RANGER J. , GELHAYE D. , POLLIER B. , PONETTE Q. , GŒDERT O. 
Published: August 2005

SummaryWe analysed the chemistry of solutions collected from soil by zero‐tension plate lysimeters and cup lysimeters connected to a constant suction (600 hPa) under Douglas fir in the Beaujolais mountains (France). The chemistry of zero‐tension lysimeters' (ZTL) and tension lysimeters' (TL) solutions differed enormously: TL solutions were most concentrated in Si, NH4‐N, NO3‐‐N, Cl−, Mg2+ and A13+ and TOC, whereas Ca2+ and K+ concentrations were greater in ZTL solutions. Organic matter (OM) greatly influenced the solution chemistry in both ZTL and TL. The chemistry of ZTL solutions was affected mainly by OM mineralization in the forest floor and upper soil horizon, and that of TL solution seemed to be related to destabilization of humified compounds under the new vegetation. Nitrification was important: residual nitrification led to excess protons neutralized in weathering or ion exchange reactions, mobilized cations, mainly A13+. Selectivity coefficients calculated both for ZTL and TL solutions formalized the differences between the two types of solutions. Nevertheless, these coefficients remained most often within the same order of magnitude indicating relations between them. Solutions from the two devices provided different information and should not be used for the same objectives. Solutions from ZTL are suited for ecosystem input‐output budgets, whereas TL solutions are more useful when equilibrium between the solution and solid phase or when plant nutrition are considered.
Three‐dimensional analysis of a loamy‐clay soil using pore and solid chord distributions
Authors: COUSIN I. , LEVITZ P. , BRUAND A. 
Published: August 2005

SummaryExamples of pore and solid chord distributions obtained for ideal porous media are presented, and the distributions of the porous and solid phases of a soil have been studied by pore and solid chord distributions. Serial sections, 100 μm apart, were cut in a soil core, impregnated with resin, and images were obtained of them. The 2D images from 160 sections were used to build a 3D reconstruction of the core. The initial 2D images, the 3D reconstructed medium and 2D computed images from the latter were studied. We found that the solid matrix of the particular soil is homogeneous and isotropic at the scale studied, and it could be characterized with a single 2D image. For pores ranging from 500 μm to 2 mm we also found similar pore chord distributions for the 2D images in the three orthogonal directions and the 3D medium. A single 2D image can be used to study these pores. For larger pores more than one 2D image is required, and we showed that eight 2D images are sufficient to describe these pores.
Physical and chemical variations within prisms of a saline polder clay in relation to seasonal changes
Authors: HALLAIRE V. , AZIB M. , CURMP P. , CHEVERRY C. 
Published: August 2005

SummaryThe prismatic structure and soil behaviour were studied on a saline clayey soil in the polder of the Marais de ľQuest (France). Three profiles with different histories were examined, and the structure under wet and dry conditions, ionic concentrations, and changes in void ratio and water suction were measured on prisms sampled between 5 and 40 cm deep, in four places (base, centre, top and side). Seasonal dynamics were accompanied by reorganization within the prismatic structure, changing both the size and distinctiveness of the blocky substructure. Chemical and physical characteristics were closely related to the sharpness of these two imbricated structures. In the absence of blocky substructure the salinity increased horizontally from the centres of the prisms to their sides (the latter acting as exchange surface between the soil and the atmosphere), and no physical gradient was apparent. These results emphasized the permanence of lateral hydraulic continuity in individual prisms. On the other hand, where the blocky substructure was well developed there was no lateral variation of salinity within the prisms, whereas the swelling potential varied from the centres to the sides: the sharpness of the substructure therefore caused a decrease in lateral water transfer. The internal structure of the prisms appeared to determine the seasonal behaviour of the soil.
The significance of organic separates to carbon dynamics and its modelling in some cultivated soils
Authors: BALESDENT J. 
Published: August 2005

SummarySoil organic matter (SOM) dynamics are usually described by compartmental models. We have sought SOM separates that might be related to SOM dynamic compartments. The turnover of C in various separates from long–term field experiments with maize was measured using the natural 13C labelling technique. The Rothamsted carbon model gave a good prediction of the observed C turnover. Primary particle–size fractions coarser than 50 μm had short lives, and could be associated with the plant structural compartment of models. Water–extractable components are enriched in young C but cannot be associated with labile compartments. None of the chemical separates obtained by acid hydrolysis, wet oxidation, thermic oxidation, pyrolysis or alkaline extraction, were enriched either in young or old C. The results showed neither a sequential relation between fulvic acids and humic acids nor a resistance of nonhydrolysable material. The range of lifetimes of soil C seems to be determined more by physical position and protection than by the chemical nature of SOM.
Land‐use and fertilization effects on P forms in two European soils: resin extraction and 31P‐NMR analysis
Authors: GUGGENBERGER G. , CHRISTENSEN B.T. , RUBÆK G. , ZECH W. 
Published: August 2005

SummaryMacroporous anion‐exchange resin extraction and 31P‐NMR spectroscopy of dialysed NaOH extracts were used to investigate the effects of land use (Taubenberg, Bavaria: spruce forest, deciduous forest, permanent grass, arable) and fertilization (Askov, Denmark: unmanured, mineral fertilizer, animal manure) on forms of phosphorus in soil with emphasis on the potentially labile organic (Po) and inorganic (Pi pools. Carbon content ranged from 12.5–118.1 g kg−1 and total P (Pi) content from 511 to 2063 mg kg−1. For all soils, the C:Po ratios of SOM decreased in the order: whole soil, 150: 1–44:1; alkali extract, 57:1–41: 1; resin extract, 20:1–9:1; suggesting an increasing P functionality of the OM with increasing Po lability. Analysis of functional relation showed a close relation between resin Po and 31P‐NMR estimates for diester‐P including teichoic acid‐P, indicating that these species contributed significantly to the labile Po pool as determined by the resin method. The most marked effects of land‐use were an increase in Pi under grass and arable, a concurrent sequestration of Po and SOM under grass, and a depletion of Po under arable. The amount of resin Pj appeared to be a function primarily of fertilization, and amounted to around 100 mg kg−1 in the fertilized soils irrespective of the SOM content and P source. The forest soil and the unfertilized agricultural soil had much smaller resin Pj values. The soil under grass had the largest amounts in resin Po and diester‐P including teichoic acid‐P, indicating a rapid turnover of Po with build‐up of a large potentially labile, microbially derived Po pool. 31P NMR also showed large proportions of labile Po species in soils where microbial activity is restrained by acidity (Taubenberg spruce forest, phosphonates) or where highly microbially altered OM is relatively enriched (Taubenberg arable, diester‐P including teichoic acid‐P).We conclude that the resin used in this study isolates a structurally and functionally reasonably uniform pool of potentially labile soil Po.
Infant mortality and soil type: a case study in south‐central England (with discussion)
Authors: MUNRO L.J.A. , PENNING‐ROWSELL E.C. , BARNES H.R. , FORDHAM M.H. , JARRETT D. 
Published: August 2005

SummaryWe have analysed the differences in infant mortality for 1981 to 1990 in areas of contrasting soil types in south‐central England. The soils overlie rocks of varied lithology and hydrology, ranging from porous and permeable Chalk and limestones, to the generally wet and impermeable Oxford and Lower Jurassic Clays. The study area comprises 504 administrative wards, for each of which the soil has been classified as being predominantly‘Wet’, ‘ Intermediate’ or ‘Dry’, depending on the degree of seasonal or periodic waterlogging. The soil classes used are those mapped by the Soil Survey of England and Wales and relate closely to the underlying geology. We find proportionately more infant deaths on the‘Wet’ soils, and a gradation towards lower infant mortality rates on the drier soils. Overall, infant mortality on the‘Wet’ soils is 31·9 percent greater than on the‘Dry’ soils, for reasons that remain unexplained. This relation between infant mortality and soil moisture remains after the effect of social class has been removed.
Predicting soil properties over a region using sample information from a mapped reference area
Authors: VOLTZ M. , LAGACHERIE P. , LOUCHART X. 
Published: August 2005

SummaryA method for mapping soil properties at a regional scale with acceptable precision and cost was investigated. It combines soil classification and interpolation, and uses sample information from a reference area and simple soil observations over the region. The method consists of two stages. First is the prediction of soil properties at a set of sites covering the region by classifying each site according to the soil classification of the reference area, and then by assigning to each site the values of soil properties measured at the representative profile of its soil class. The second is by interpolating the predictions of the properties from the classes at the observation sites. Three methods were considered: kriging, inverse squared distance and nearest neighbour. The performance of classification combined with interpolation was evaluated for mapping water content at wilting point in an area of 1736 ha in a physiographic region of Southern France. The method was compared with conventional methods, namely kriging with actual data and prediction from a soil map at a scale of 1:100000. Estimates from classification combined with kriging were more precise than those from the 1:1OOOOO soil map in all instances, and close to those of ordinary kriging with actual data when prediction points were near the observation points. Classification combined with inverse squared distance or with nearest neighbour interpolation was always less precise than classification with kriging. However, it was more precise than classification at the 1:100 000 scale except when prediction points were far from the observation points.