bluuebunny/crossref_metadata_2025_split huggingface dataset:
The role of amino acids and nucleic bases in turnover of nitrogen and carbon in soil humic fractions
Authors: KUZYAKOV Y.V. 
Published: August 2005

SummaryIncorporation of labelled 15N and 14C amino acids and nucleic bases into soil humus fractions as well as humus turnover was investigated under field conditions. The dynamics of 15N and 14C incorporation into organic matter was characterized by the following main steps: rapid incorporation of the labelled substance prevailing for the first 1–3 weeks, and decomposition of included labelled fragments prevailing beyond one month after substance addition. The annual turnover rates of N and C in humus fractions due to incorporation of amino acids and nucleic bases were calculated. The turnover rate of N in humus is two to three times that of C. The contribution of amino acids to organic matter generation is about twice as great as that of nucleic bases and other N‐containing organic substances. This indicates the important role of amino acids in the humification process and humus turnover. Turnovers of humic acids (0·002 year−1 for C and 0·02 for N) are the most rapid of humic fractions investigated, and humin is characterized by the slowest turnover (0·0002 year−1 for C and 0·007 for N). There are no significant differences in the turnover rates of fulvic acid fractions (0·0002 year−1 for C) with different molecular weight.
Factors affecting phosphate sorption along a Mediterranean, dolomitic soil and vegetation chronosequence
Authors: CARREIRA J.A. , LAJTHA K. 
Published: August 2005

SummaryPhosphate sorption by calcareous soils has been studied mainly on heavily fertilized agricultural soils and soils with calcite as the main carbonate mineral. We examined factors affecting phosphate adsorption in the soils of a semi‐arid, mediterranean, dolomitic, soil and vegetation chrono‐sequence in southeastern Spain. The youngest soils are highly eroded, Sandy Regosols (Typic Xerorthents) under gorse‐scrubland vegetation. These have small P sorption capacities, large Mg‐Ca carbonate contents but small amounts of Fe and Al oxides. Small total P (HNO3/HClO4 digestion) concentrations (30–130 μg P g−1), of which up to 90% is Ca‐bound (HCl‐extractable), are typical of these young soils. P sorption markedly increased when Ca2+ was added to the solution. The fractionation of previously sorbed P indicates that the fate of most of this extra‐sorbed P is the labile‐P fraction sorbed on to (carbonate) surfaces and the apatite‐like fraction (NaHCO3‐extractable and HCl‐extractable fractions). At the other extreme, older more‐intensively weathered, sandy‐clay‐loam rendzinas (Entic Haploxerolls), supporting dense mature garrigue, have a much greater P adsorption capacity and larger clay and Fe and Al oxide concentrations. They have more total P (ca 400 μg P g−1), much of it in occluded form (residual fraction). These soils show no significant differences in P sorption whether or not CaCl2 was used as a background electrolyte. Considering the overall variations within the chronosequence, dithionite extractable Fe and Al are the properties best correlated with P sorption. This support the general finding that crystalline Fe‐oxides (e.g. goethite and haematite) appear to be the most important P‐sorbing component for soils in the Mediterranean region, rather than amorphous Fe‐oxides (e.g. ferrihydrite) as is reported for more mesic areas. Stepwise multiple regression and fractionation data, however, suggest that, provided the soil solution is rich in Ca2+, carbonate may also be a significant contributing factor to P sorption, especially in the youngest of these dolomitic soils.
Effects of changes in pH, ionic strength, and sulphate concentration on the CEC of temperate acid forest soils
Authors: MATSCHONAT G. , VOGT R. 
Published: August 2005

SummaryAs the acidity of rain diminishes, changes in the pH, ionic strength, and ion activities of the soil solution will influence the charge characteristics of soil. We have investigated the response of cation exchange capacity (CEC) of three acid forest soils of variable charge to small changes in pH, ionic strength, and SO2−4concentration. The variable charge for these temperate soils has the same significance as for tropical soils and those from volcanic ash. Maximum absolute increase in CEC on increasing pH by 0·2–0·5 units reached 5 cmolckg‐1in O horizons. The increase in CEC on doubling ionic strength in EA and Bsh horizons of a Cambic Podzol was about half that amount, but relative gains compared to effective CEC were 65 and 46%, respectively. For other soil horizons, absolute changes were smaller, and relative changes were between 10 and 30%. Halving the SO2−4concentration significantly influenced CEC only in some samples. Both pH and ionic strength must be adjusted with care when determining CECcof acid forest soils. Decreasing acid deposition will not inevitably increase CECcbecause in some soils pH effects may be balanced by simultaneous decrease in ionic strength.
A hard sandy‐loam soil from semi‐arid Northern Cameroon: I. Fabric of the groundmass
Authors: LAMOTTE M. , BRUAND A. , HUMBEL F.X. , HERBILLON A.J. , RIEU M. 
Published: August 2005

SummaryIn semi‐arid tropics soil hardening may reduce both water infiltrability and biological activity, thus inducing the development of large almost bare areas. A sandy‐loam soil with contrasting loose and underlying hard horizons was studied in the southern plain of the Chad basin. The fabrics of these horizons were studied using combined sieving and sedimentation techniques, mercury porosimetry and scanning electron microscopy. The horizons had similar particle size distributions of the skeleton grains. The hard horizon differs by a small increase in its fine clay (< 0·2 μm) content. The hardness is closely related to a fabric with clay coatings on the skeleton grains and clay wall‐shaped bridges linking the latter. This induces a strong continuity of the solid phase. This fabric requires a minimum of clay content (6%) to make the coatings and the wail‐shaped bridges, and it can be 30% less porous than the loose horizon, without any change in the packing of the skeleton grains. These characteristics of the fabric of the hard horizon are like those of fragipans elsewhere. The continuity of the solid phase, from the microscopic to the macroscopic scale, as well as the absence of a network of cracks explains the considerable strength of the hard horizon, and consequently the difficulties for water infiltration, root penetration and tillage.
Release of Al by hydroxy‐interlayered vermiculite and hydroxy‐interlayered smectite during determination of cation exchange capacity in fine earth and rock fragments fractions
Authors: CORTI G. , AGNELLI A. , UGOLINI F.C. 
Published: August 2005

SummaryThe fine earth (<2 mm) and rock fragments (>2 mm) fractions of two soils derived from Oligocene sandstone have been examined to assess the origin of the discrepancies between cation exchange capacity (CEC) and effective CEC (ECEC). The soils differ in terms of acidity: soil A is more acid than soil B. When the A samples are treated with BaCl2, the solution became sufficiently acid (pH < 4·5) to dissolve and to maintain Al in solution. From these samples more Al is released than base cations. Aluminium was continuously replenished even after 192 h, so that the ECEC was always larger than the CEC. Samples from soil B contain less H and Al ions, and the BaCl2 solution could not lower the pH below 5·0. In these samples little Al is released, and the base cations dominate the exchangeable pool of ions. This Al can be considered to be exchangeable, and a good agreement exists between the ECEC and the CEC. The source of non‐exchangeable Al in the A samples is the OH‐Al polymers of the hydroxy‐interlayered vermiculite (HIV) and hydroxy‐interlayered smectite (HIS) that tend to dissolve during the BaCl2 treatments. In the less acid B samples the Al polymers are not affected by BaCl2 treatment. Different results were obtained when the clays, extracted from an Na‐dispersed suspension, were treated with BaCl2 solution. Because the clays are no longer acid, no H+ is released, and the OH‐Al polymers are not dissolved. Therefore, the saturating ions play an important role in the dissolution of the OH‐Al polymers and cause differences between the CEC and ECEC. We discount organic matter and specifically Al‐organo complexes as a source of non‐exchangeable Al. Both A and B soils contain very similar pyrophosphate‐extractable Al, but show substantial differences in the amount of exchangeable Al.
Dissolved organic matter sorption on sub soils and minerals studied by13C‐NMR and DRIFT spectroscopy
Authors: KAISER K. , GUGGENBERGER G. , HAUMAIER L. , ZECH W. 
Published: August 2005

SummarySorption on the mineral matrix is an important process restricting the movement of dissolved organic matter (DOM) in soils. In this study, we aimed to identify the chemical structures responsible for the retention of DOM by sorption experiments with total DOM and acidic humic substances (AHS), containing humic and fulvic acids, on soil samples and minerals (goethite, ferrihydrite, and amorphous Al(OH)3). The AHS remaining in solution after sorption were studied by13C nuclear magnetic resonance (NMR) analysis, and total DOM and AHS for bed on the surfaces of minerals by diffuse reflectance Fourier‐transform infrared (DRIFT) spectroscopy. The soil samples were taken from strongly sorbing Bw horizons of two Inceptisols rich in pedogenetic Fe (29 and 35 g kg−1) and containing little C (7 and 22 g kg−1). The13C‐NMR spectra showed that sorption causes a preferential removal of aromatic and carboxyl C from the solution, whereas alkyl‐C accumulates in the solution. No change was observed for O‐alkyl C. The DRIFT spectra of sorbed total DOM and AHS showed a relative increase of the band intensity of carboxyl groups compared to DOM in the initial solution, confirming the importance of those groups for the sorption to mineral surfaces. The spectra also indicated reactions of carboxyl groups with metals at the mineral surfaces. The extent to which the carboxyl groups are bound depended on the surface coverage with DOM and the type of mineral.
Phenolic and carbohydrate signatures of organic matter in soils developed under grass and forest plantations following changes in land use
Authors: SANGER L.J. , ANDERSON J.M. , LITTLE D. , BOLGER T. 
Published: August 2005

SummaryComparisons were made between the phenolic and carbohydrate signatures of soil profiles developed under grass, spruce and ash stands. Samples were collected from a brown earth soil which was originally under the same land use, but over the past 43 years has supported different monocultures. Distinct signatures associated with each litter type were recorded in individual profiles. A relatively undecomposed phenolic fraction from lignin and hydrolysable carbohydrate fraction from plants had accumulated in the soils under spruce and ash. This largely reflected the quantity and quality of the litter inputs from the spruce and ash compared with the grass. The phenolic and hydrolysable carbohydrate fractions accounted for as much as 60% of the total organic carbon concentration in the deep horizons. In the grassland profile both fractions were more decomposed than under ash and spruce suggesting that the forest profiles had rapidly accumulated a carbon pool with a comparatively slow rate of decomposition. This was most apparent from the spruce profile (which contained 398 mg g−1 C carbohydrate hydrolysed using trifluoracetic acid (TFA) in the C horizon compared with 165 and 45 mg g−1 C under ash and grass respectively). We conclude that the decay rate of these fractions is a function of the vegetation type.
Ecotoxicological effects of fluorine deposits on microbial biomass and enzyme activity in grassland
Authors: TSCHERKO D. , KANDELER E. 
Published: August 2005

SummaryThe influence of atmospheric fluoride deposits on the soil microbial biomass and its enzyme activities was investigated near the aluminium smelter at Ranshofen, Upper Austria. Soil samples at various distances from the emission source were analyzed for water‐extractable F and microbial activity. The water‐extractable F contents at the sites examined reflected the gradient of F exposure (10 to 189 mg F kg−l dry soil). The microbial activities increased with distance from the emission source and were inversely correlated with the degree of F contamination. The linear correlation coefficients between the water‐extractable F concentrations and the microbial biomass, dehydrogenase and arylsulphatase activity were r=−0·8, −0·86 and −0·84, respectively. In the most contaminated soil (up to 189 mg F kg−1), the microbial activities were only 5–20% of those in the unpolluted soil. The microbial biomass and dehydrogenase activity decreased substantially where the concentration of F exceeded 100mgkg−1, whereas arylsulphatase activity was already inhibited at 20 mg kg−1. The accumulation of organic matter near the smelter (123 mg F kg−1) also indicated severe inhibition of the microbial activity by F. Our investigations show that the ratio of arylsulphatase to microbial biomass can be used as a sensitive index for evaluating environmental stress such as F Contamination.
Solubility control of Cu, Zn, Cd and Pb in contaminated soils
Authors: McBRIDE M. , SAUVE S. , HENDERSHOT W. 
Published: August 2005

SummaryWe developed a semiempirical equation from metal complextion theory which relates the metal activity of soil solutions to the soil's pH, organic matter content (OM) and total metal content (MT). The equation has the general form:
image
where pM is the negative logarithm (to base 10) of the metal activity, and a, b and c are constants. The equation successfully predicted free Cu2+ activity in soils with a wide range of properties, including soils previously treated with sewage sludge. The significant correlation of pCu to these measured soil properties in long‐contaminated soils suggests that copper activity is controlled by adsorption on organic matter under steady state conditions. An attempt was made from separate published data to correlate total soluble Cu, Zn, Cd and Pb in soils to soil pH, organic matter content and total metal content. For Cu, the total Cu content of the soil was most highly correlated with total soluble Cu. Similarly, total soluble Zn and Cd were correlated with total metal content, but were more strongly related to soil pH than was soluble Cu. Smaller metal solubility in response to higher soil pH was most marked for Zn and Cd, metals that tend not to complex strongly with soluble organics. The organic matter content was often, but not always, a statistically significant variable in predicting metal solubility from soil properties. The solubility of Pb was less satisfactorily predicted from measured soil properties than solubility of the other metals. It seems that for Cu at least, solid organic matter limits free metal activity, whilst dissolved organic matter promotes metal solubility, in soils well‐aged with respect to the metal pollutant. Although total metal content alone is not generally a good predictor of metal solubility or activity, it assumes great importance when comparing metal solubility in soils having similar pH and organic matter content.
Measurement of volumetric water content by TDR in saline soils
Authors: WYSEURE G.C.L. , MOJID M.A. , MALIK M.A. 
Published: August 2005

SummaryTime‐domain reflectometry (TDR) evaluates the bulk dielectric constant, K, of the soil by measuring the travel time of an electromagnetic pulse through a sensor, and through it estimates the volumetric water content. We show that for saline soils the effects of conductivity and frequency on the travel time cannot be neglected and that, as a result, TDR systematically overestimates the water content in saline soils. Simultaneously the bulk electrical conductivity of soils can be estimated by TDR. The equivalent impedance after multiple reflections is related to the bulk electrical conductivity, σ This relation differs from sensor to sensor and requires calibration for each individual sensor.A method is proposed for correcting the volumetric water content in saline soils. First, the bulk electrical conductivity, o, is estimated from the equivalent impedance at a specific equivalent distance of cable, several times the actual length of the sensor. The zero‐salinity dielectric constant, KO, of this soil is obtained by correcting the apparent K as a function of the measured bulk electrical conductivity. The volumetric water content is estimated from Ko. The correction of K is a function of the equivalent frequency of the electromagnetic pulse. The imaginary part of the dielectric constant is primarily due to ohmic losses. The model, which calculates the velocity of propagation of the electromagnetic pulse and which takes into consideration the imaginary part, performs reasonably well. An empirical approach based on calibration gave slightly better results.
Differential Contribution of Nitric Oxide and cGMP to the Stimulatory Effects of Growth Hormone‐Releasing Hormone and Low‐Concentration Somatostatin on Growth Hormone Release from Somatotrophs
Authors: Luque R. M. , Rodríguez‐Pacheco F. , Tena‐Sempere M. , Gracia‐Navarro F. , Malagón M. M. , Castaño J. P. 
Published: August 2005

AbstractThere is increasing evidence that nitric oxide (NO) produced by NO synthase (NOS), and their signalling partners, guanylyl cyclase and cGMP, play a relevant role in growth hormone (GH) secretion from somatotrophs. We previously demonstrated that both GH‐releasing hormone (GHRH; 10−8 M) and low concentrations of somatostatin (10−15 M) stimulate pig GH release in vitro, whereas a high somatostatin concentration (10−7 M) inhibits GHRH‐induced GH secretion. To ascertain the possible contribution of the NOS‐NO and guanylyl cyclase‐cGMP routes to these responses, cultures of pituitary cells from prepubertal female pigs were treated (30 min) with GHRH (10−8 M) or somatostatin (10−7 or 10−15 M) in the absence or presence of activators or blockers of key steps of these signalling cascades, and GH release was measured. Two distinct activators of NO route, SNAP (5 × 10−4 M) or L‐AME (10−3 M), similarly stimulated GH release when applied alone (with this effect being blocked by 10−7 M somatostatin), but did not alter the stimulatory effect of GHRH or 10−15 M somatostatin. Conversely, two NO pathway inhibitors, NAME (10−5 M) or haemoglobin (20 µg/ml) similarly blocked GHRH‐ or 10−15 M somatostatin‐stimulated GH release. 8‐Br‐cGMP (10−8 to 10−4 M) strongly stimulated GH release, suggesting that cGMP may function as a subsequent step in the NO pathway in this system. Interestingly, 10−7 M somatostatin did not inhibit the stimulatory effect of 8‐Br‐cGMP. Moreover, although 8‐Br‐cGMP did not modify the effect of GHRH, it enhanced GH release stimulated by 10−15 M somatostatin. Accordingly, a specific guanylyl cyclase inhibitor, LY‐83, 583 (10−5 M) did not alter 10−15 M somatostatin‐induced GH release, whereas it blocked GHRH‐induced GH secretion. These results demonstrate for the first time that the NOS/NO signalling pathway contributes critically to the stimulatory effects of both GHRH and low‐concentration somatostatin on GH release, and that, conversely, the subsequent guanylyl cyclase/cGMP step only mediates GHRH‐ and not low‐concentration somatostatin‐induced GH secretion from somatotrophs.
Ethnic Variations of IL‐10 Polymorphisms in a Sami and Norwegian Population
Authors: Torkildsen Ø. , Utsi E. , Harbo H. F. , Mellgren S. I. , Vedeler C. A. , Myhr K.‐M. 
Published: August 2005

AbstractInterleukin‐10 (IL‐10) production is genetically determined and influenced by different polymorphisms in the promoter region of IL‐10. These polymorphisms may contribute to the risk and clinical outcome of various infectious and immunological‐related diseases. The Samis are the aboriginal inhabitants of Norway and Fennoscandinavia and are ethnically different from the Norwegians. Different distribution of various immune‐related diseases among the Samis compared with Norwegians have been reported. This is the first study to evaluate the distribution of IL‐10 polymorphisms in the Sami population. Two hundred healthy Samis were genotyped for polymorphisms in the promoter region of IL‐10 at region −1082 (G/A), −819 (T/C) and −592 (A/C). The allele frequencies, genotypes and haplotypes were compared with 187 healthy Norwegians. A significantly higher number of the Samis than the Norwegians had the ATA/ATA genotype, whereas the Norwegians displayed a higher frequency of the GCC/GCC genotype (P = 0.0057). There was a significant difference in haplotypes in the two populations with a P = 0.0024. These findings may be important for the distribution and clinical outcome of various infectious and immune‐related disorders in the two populations.
Signal Pathway of Cytokines Produced by Reactive Oxygen Species Generated from Phorbol Myristate Acetate‐Stimulated HMC‐1 Cells
Authors: Kim J. Y. , Ro J. Y. 
Published: August 2005

AbstractThe relationship of cytokine production and reactive oxygen species (ROS) generated in mast cells has not been reported yet. This study aimed to examine the signal pathway in the production of cytokines [interleukin‐8 (IL‐8) and tumour necrosis factor‐α (TNF‐α)] by ROS generated from phorbol myristate acetate (PMA)‐stimulated human mast cell line‐1 cells (HMC‐1). HMC‐1 cells were stimulated with 25 ng/ml of PMA. The ROS generation and production of cytokines (IL‐8 and TNF‐α) were measured by fluorescence‐activated cell sorter and enzyme‐linked immunosorbent assay method, respectively. Phosphorylation of mitogen‐activated protein kinase family (extracellular signal‐regulated kinase, p38 and c‐Jun N‐terminal kinase) was detected by the Western blotting method. The expression of cytokine's mRNA was measured by reverse transcriptase – polymerase chain reaction, and the DNA‐binding activity of the transcription factors [nuclear factor‐κB (NF‐κB) and activator protein‐1] was detected by electrophoretic mobility shift assay. PMA‐stimulated HMC‐1 cells immediately generated ROS, and the generated ROS was inhibited by 1,3‐dimethyl‐2‐thiourea (DMTU), but partially inhibited by catalase orN‐acetyl‐l‐cysteine. The production of cytokines in PMA‐stimulated HMC‐1 cells reached the maximum at 3–5 h and was inhibited by DMTU and specific kinase inhibitor for p38, SB203580. DMTU and SB203580 also inhibited the expressed cytokine's mRNA level and the increased DNA‐binding activity of transcription factors, NF‐κB in PMA‐stimulated HMC‐1 cells. These data suggest that intracellular ROS generated from PMA‐stimulated HMC‐1 cells contributes to the production of inflammatory cytokines via p38 kinase/NF‐κB.