bluuebunny/crossref_metadata_2025 huggingface dataset:
A simple equation for simulating C decomposition in a multi‐component pool of soil organic matter
Authors: Fang C. , Smith P. , Smith J. U.
Published: September 2005

Partitioning carbon (C) pools presents theoretical and practical challenges in soil modelling. In most current models, organic matter (OM) is commonly divided into a number of pools using data‐fitting techniques. It is often not possible to measure the properties of each pool of soil C simulated in this way. Furthermore, there is no effective way in current soil models to properly simulate inputs of OM with variable qualities in terms of decomposability. Here, we describe a simple model, taking the OM as a whole and assuming a rate constant function changing exponentially with time, to simulate C decomposition in a multi‐component OM pool. The model requires fewer parameters to be estimated than current multi‐component models, and the simulated properties of OM are measurable. When changing the quantity and the quality of OM input, the model produces results similar to multi‐component models, but avoids the difficulty and uncertainty of OM partitioning.
Determination of labile Cu in soils and isotopic exchangeability of colloidal Cu complexes
Authors: Ma Y. B. , Lombi E. , Nolan A. L. , McLaughlin M. J.
Published: September 2005

Measurement of labile (isotopically exchangeable) pools of metals (E values) in soil is required to assess the size of metal pools potentially available to soil organisms, from both a micronutrient deficiency and metal toxicity viewpoint. In this paper, E values of soil Cu were measured by an isotope dilution technique using different solution extracts – water with and without resin purification, water coupled with Donnan dialysis (free ion determination) and 0.01 m CaCl2. Using these techniques, the isotopic exchangeability of Cu species in water extracts was investigated. The results showed that the specific activity of 64Cu in the water‐soluble fraction was less than in the free metal ion fraction or in the fraction that adsorbed to resin. The isotopically non‐exchangeable Cu in water extracts ranged between 4% and 40% of water‐soluble Cu (16% on average), and appeared to be associated with dispersed colloids. The existence of isotopically non‐exchangeable Cu in water extracts led to overestimation (17.7% on average) of isotopically exchangeable Cu in soils when based on the specific activity in water extracts. The method of isotope dilution coupled with resin extraction is recommended for the determination of isotopically exchangeable Cu in soils when water extracts are used.
Temporal variation in the surface‐water chemistry of a blanket bog on Dartmoor, southwest England: analysis of 5 years' data
Authors: Proctor M. C. F.
Published: September 2005

Blanket‐bog peats, mapped as the Winter Hill and Crowdy associations by the Soil Survey of England and Wales, are an oceanic manifestation of the ombrotrophic ‘raised‐bog’ (Hochmoor) peats that cover large tracts in the boreal zone of the northern hemisphere. This paper examines monthly analyses from 1992 to 1997 of major ions and other variables from an upland blanket bog in southwest England in relation to seasonality, rainfall, and the chemical composition of rainwater. Average ionic composition of surface water (and peat) integrates variable atmospheric solute inputs over the years. The dominant ions in the surface water, Na+ and Cl–, showed only weak seasonality, but divalent cations a stronger seasonal pattern with a summer maximum. Mean pH ranged from c. 4.4 in February to c. 4.2 in August. Changes in concentration of different cations were closely interlinked by cation exchange. The anion deficit, accounted for by anionic groups on the dissolved organic matter, was strongly seasonal with a summer maximum, as was optical absorbance at 320 nm. Nitrate and NH4+ were both at much smaller concentrations than in rain. Nitrate exceeded 1 μmol l−1 only during cold periods in winter, mainly following drought in the summer of 1995; NH4+ reached a few μmol l−1 only in summer. There was evidence of net retention of S by the peat in wet sites and during wet periods, and of net release of SO42– (and acidity) under dry conditions. The 1995 summer drought and ensuing dry year in 1996 had marked and persistent effects on pH, apparent ion deficit (DEF), SO42–, the divalent cations and Fe.
Microscale Zn and Pb distribution patterns in subsurface soil horizons: an indication for metal transport dynamics
Authors: Van Oort F. , Jongmans A. G. , Citeau L. , Lamy I. , Chevallier P.
Published: September 2005

In many studies on soil pollution, authors conclude that there is no downward migration of metal elements if no evidence for enrichment can be inferred from profiles of total metal contents. We assessed possible transfer of mobile and less mobile metal pollutants to depth in subsurface horizons of a heavy metal contaminated soil, by a study of specific pedofeatures in thin sections by optical microscopy, and their corresponding Zn and Pb distribution patterns by synchrotron‐based X‐ray microfluorescence. In the B horizon (70 cm depth), Zn accumulation was predominantly associated with clay–iron coatings. Strong correlation was found between Zn and Fe (r = 0.94), Zn and Mn (r = 0.75), Zn and Ti (r = 0.84), and Zn and K (r = 0.88), but significant correlation was absent between Zn and Pb. In the C horizon (100 cm depth), clear Pb accumulation was observed in distinct iron coatings, with large correlation coefficients found between Pb and Fe (r = 0.94–0.75), whereas correlation between Zn and Fe was absent. Detected Zn concentrations were small and attributed to the local natural geochemical background. These results were then compared with data of the composition of gravitational soil water collected in other soils from the same study area. Thus, Zn accumulation in the B horizon was ascribed to interception of dissolved Zn2+by negatively charged constituents of clay–iron coatings. In contrast, Pb accumulation in C horizons was related to precipitation of Pb‐bearing iron colloids leading to neoformed, optically pure iron oxyhydroxide crystals and coatings. We demonstrate very localized accumulation of almost immobile Pb which occurs at greater depth than the more mobile Zn. The common, but strongly localized, occurrence of Pb‐bearing iron coatings in the soil groundmass explained the absence of changes in the total Pb concentrations of the C horizon compared with the concentrations in the B horizon.
Phosphorus solubility and sorption in frozen, air‐dried and field‐moist soil
Authors: Peltovuori T. , Soinne H.
Published: September 2005

The effects of freezing on soil phosphorus (P) chemistry are poorly understood, although freezing is habitual for many soils at middle and high latitudes. We studied the effects of various freezing treatments on the solubility and sorption of P in an incubation experiment on two coarse and two fine‐textured cultivated surface soils in Finland. Air‐drying was included in the experimental arrangement because freezing and drying have similar features. Compared with field‐moist soils stored at +5°C in the dark, freezing had few effects on P extractability by water or on sorption properties of P studied with a Q/I plot technique. Air‐drying, by contrast, increased almost systematically the equilibrium concentration of P estimated with Q/I plots, water‐soluble organic carbon, and the extractability of P, aluminium, iron and manganese in the soils. The results imply that drying destroys organomineral complexes. The breakdown of these complexes releases P, while simultaneously exposing new surfaces on which P could sorb. Because of the considerable impact of drying on the behaviour of P, air‐drying of soil samples should be avoided in studies of the chemistry of P in soil. Freezing seems to be a safe way of storing mineral soil for such studies, but it may significantly alter the P conditions of soils rich in organic matter.
Production of gaseous mercury in tropical hydromorphic soils in the presence of ferrous iron: a laboratory study
Authors: Peretyazhko T. , Charlet L. , Grimaldi M.
Published: September 2005

In this paper, we demonstrate that reduction of Hg(II) to Hg0 under anaerobic conditions, followed by volatilization of Hg0 to the atmosphere, might be responsible for the removal of Hg from tropical hydromorphic soils. We conducted a series of kinetic batch experiments in which we added Hg(II) to anoxic suspensions of a soil clay fraction and haematite nanoparticles. The clay fraction came from three depths in a hydromorphic soil by the Leblond River in French Guiana, South America: close to the upper and lower boundaries (30–40 cm and 90–100 cm) and within the central part (60–70 cm) of the frequently water‐saturated clay horizon. We prepared a second set of soil clay fraction suspensions with Fe(III) citrate, whose reduction acted as a source of dissolved Fe(II) to investigate the influence of Fe(II) on the production of Hg0. Reduction of Hg(II) to Hg0 occurred with all samples amended with Fe(III) citrate. Laboratory experiments with haematite suspensions demonstrated that adsorption of Fe(II) to the haematite surface created very reactive sites for the reduction of Hg(II), while in the absence of haematite particles, no production of Hg0 occurred. The greatest production of Hg0 was found for the depth intervals 30–40 cm and 90–100 cm, where the total mercury concentration exhibits a local minimum. The observed pseudo‐first order rate constants for the 90–100 cm depth sample were close to rate constants reported for abiotic reduction of Hg(II) by Fe(II) adsorbed on mineral surfaces. Significant production of Hg0 was found for the 90–100 cm depth interval sample, both with and without Fe(III) citrate. A biotic pathway as well as abiotic reduction by Fe(II) might be involved in the reduction of Hg(II) to Hg0.
Effect of water composition on phosphorus concentration in runoff and water‐soluble phosphate in two grassland soils
Authors: Schärer M. , Vollmer T. , Frossard E. , Stamm C. , Flühler H. , Sinaj S.
Published: September 2005

Many irrigation experiments determine phosphorus (P) losses from soil. Often, these studies cannot be compared, because the irrigation water was not characterized. We used calcium‐rich tap water and deionized water to investigate the influence of water composition on P concentrations in induced runoff. We irrigated two grassland sites: one acid and one calcareous. Less P was measured in runoff from tap water irrigation than from deionized water, especially for the acid soil. Batch experiments confirmed the findings of the field experiments. Tap water decreased water‐soluble phosphate and increased calcium in the solid phase. This interaction increased with decreasing soil:water ratio. Water of low ionic strength gave results comparable to rainwater.

Our findings demonstrate that solution chemistry and the soil:water ratio can strongly influence the availability of P for transport. We recommend that P tests or irrigation experiments should use water resembling that of the system of interest. Irrigation experiments aiming to simulate P losses by surface runoff should be carried out with water having a composition comparable to rainwater.
Root impact on the stability and types of micro‐ aggregates in silty soil under maize
Authors: Watteau F. , Villemin G. , Burtin G. , Jocteur‐Monrozier L.
Published: September 2005

We wished to assess the impact of maize roots on the stability, nature and formation of soil organomineral aggregates under field conditions. We sampled coarse‐textured soil, cropped with maize for 3 years, and combined in situ study of the root system with evaluation of soil structural stability. We examined root morphology (i) on thin sections of still recognizable root tissues, and (ii) at the interfaces between roots and soil, using transmission electron microscopy (TEM) to differentiate between fine and coarse roots. Soil structural stability was evaluated in relation to a spatial gradient of increasing distance from the roots. For that we distinguished between soil adhering to roots and that not adhering in the rhizosphere, and soil between the rows of this crop, and used two methods of granulodensimetric soil fractionation involving different disaggregation strengths. We isolated and identified the organomineral associations in the soil fractions determining soil stability. We found that the roots at the soil–root interface generated stable aggregates of 2–20 µm size, which were much involved in the structural stability of the soil adhering to roots. We identified by TEM several types of organomineral associations that depended on the nature of the plant or microbial organic matter. The distribution of the different types of aggregates varied according to their positions in relation to the roots. We showed that humification of roots contributes significantly to the development of stable organomineral associations in the soil.
Humus components and biogenic structures under tropical slash‐and‐burn agriculture
Authors: Topoliantz S. , Ponge J.‐F. , Lavelle P.
Published: September 2005

Slash‐and‐burn cultivation in the humid tropics can cause changes in the composition of topsoil, depending on the duration of the fallow. We studied differences between practices, using the small‐volume micromorphological method, to quantify the distribution of solid components in the topsoil, concentrating on plant organs and biogenic structures created by soil animals. We compared samples of topsoil from five plots, two at Maripasoula, an Aluku village along the Maroni river (French Guiana), with short fallow (= 8 years), and the other three at Elahe, a Wayana village along the same river, with long fallow (= 25 years). At both sites structures created by arthropods other than ants gave way to ones formed by ants and annelids under the influence of fire and cultivation. This change was more abrupt under long fallow, because of the time needed to restore the arthropod community. Charcoal and charred plant material were incorporated by earthworms into the mineral soil, forming dark grey to black aggregates. Charcoal became mixed with the mineral soil faster at Elahe than at Maripasoula, where it accumulated in the topsoil. The reason seems to be an imbalance between charcoal inputs (from repeated fires) and the capacity of burrowing animals (earthworms, ants) to mix it with the mineral soil.
Effect of earthworm activity (Aporrectodea giardi) on atrazine adsorption and biodegradation
Authors: Alekseeva T. , Besse P. , Binet F. , Delort A. M. , Forano C. , Josselin N. , Sancelme M. , Tixier C.
Published: September 2005

We investigated the influence of earthworm (Aporrectodea giardi) activity on soil properties and on atrazine (AT) adsorption and biodegradation by comparing a coarse‐textured smectite‐free wetland soil (Brittany, France) with the earthworm casts derived from the top horizon of this soil. Casts are characterized by lower pH, are enriched in organic carbon (OC) and clay content, have a larger cation exchange capacity, and a greater exchangeable Ca content. The clay mineralogy of the soil studied and casts is characterized by a muscovite–kaolinite–chlorite association. In addition, the clay fraction of the soil contains lepidocrocite (γ‐FeOOH), which was not found in the casts. Atrazine adsorption isotherms were reasonably well described by the Freundlich equation and were all non‐linear. The mean amounts of adsorbed AT for starting concentrations of 3–30 mg litre−1 ranged from 8 to 34%, being largest in earthworm casts. Soil AT adsorption capacity was well correlated with OC content. Non‐decomposed organic matter present in the coarse size fractions and specific compounds present in earthworm casts (proteins, mono‐ and polysaccharides, polyphenols, sugars, lignin) and microbial and fungal biomass contribute to AT adsorption. Weak electrostatic (physical) sorption of AT on organic compounds and on mineral surfaces prevails. For casts, the formation of additional hydrophobic interactions between AT and SOM is proposed. We also studied AT biodegradation by the model bacterium Pseudomonas sp. strain ADP in the presence of soils or earthworm casts. An enhancement of the AT disappearance rate was observed in the presence of all the solid matrices tested compared with that obtained in an aqueous medium. The biodegradation rate was shown to be dependent not only on the OC content of the solid matrix, but mainly on its composition and structure.
The cation exchange capacity of a sandy soil in southern Brazil: an estimation of permanent and pH‐dependent charges
Authors: Bortoluzzi E. C. , Tessier D. , Rheinheimer D. S. , Julien J. L.
Published: September 2005

In soils in general, the cation exchange capacity is an important factor in soil fertility because it determines both cation retention and selectivity, and in turn controls most of the other soil properties. The main goal of this paper was to estimate the cation exchange capacity (CEC) and the contribution of permanent charges and pH‐dependent charges and their respective importance in soil CEC as a function of pH, clay and organic matter content in soils. A multiple regression method was developed from 75 samples under different soil management practices. The permanent charge (∼ 140 mmolc kg−1 of clay) estimated by this approach was independent of the analytical method used, i.e. a French method (MF) and a Brazilian method (MB), and is consistent with the presence of 2:1 clay minerals. However, the pH‐dependent charges were closely related to the buffering capacity inherent in each protocol (MF protocol using NH4+, and MB using a SMP solution proposed earlier by other workers, both at pH 7). For the MF protocol, the proposed method appeared to be well adapted for reproducing soil component properties under different management conditions. In the soil samples studied, the contribution of organic carbon to negative charges ranged from 12.3 to 55.8% of effective CEC and from 14.1 to 59.2% of CEC at pH 7. However, the clay contribution, notably its permanent charges, can contribute to 31% and more of the CEC in the lower horizons of soil profiles. The proposed approach can accurately evaluate the effective and pH 7 CECs when the MF protocol is used but evaluation is less accurate with the MB protocol.
Distribution of soil organic carbon and phosphorus on an eroded hillslope of the rangeland in the northern Tibet Plateau, China
Authors: Zhang J. H. , Liu S. Z. , Zhong X. H.
Published: September 2005

Some studies on the relationship between soil erosion and subsequent redeposition of eroded soils in the same field and soil quality have been conducted in croplands, yet few studies have revealed this relationship in rangelands. We selected a toposequence with a slope of 30% and a horizontal length of 342 m from the rangeland in the northern Tibet Autonomous Region, China (31°16′N, 92°09′E) to determine the relationship between soil erosion, soil organic carbon (SOC) content and available P patterns within a hillslope landscape. Soil samples for the determination of 137Cs as well as SOC, available P and particle‐size fractions were collected at 20 m intervals along a transect of this hillslope. Soil redistribution was caused primarily by wind erosion at toe‐slope positions, but primarily by water erosion at the hillslope positions above the toe‐slope. In upper‐ and mid‐slope portions (0 m to 244 m horizontal length), SOC content is closely correlated to 137Cs concentration (r = 0.74, P < 0.01, n= 15), suggesting that SOC distribution along the slope was similar to 137Cs distribution, which itself was dependent on topographic changes. However, SOC contents in toe‐slope portions are less than those above the toe‐slope (i.e. upper‐ and mid‐slope portions), and the correlation between 137Cs and SOC in the toe‐slope portion is weaker than that above the toe‐slope. A highly significant correlation (r = 0.72, P < 0.001, n= 20) between 137Cs concentration and available P was found within the whole hillslope landscape, implying the distribution pattern of available P was somewhat different from that of SOC. We suggest that the distribution of SOC within the hillslope landscape is also affected by factors such as assimilation rates due to difference in grassland productivity at different points and different biological oxidation rates of carbon related to patterns of moisture distribution.
Effects of cereal roots on detachment rates of single‐ and double‐drilled topsoils during concentrated flow
Authors: Gyssels G. , Poesen J. , Liu G. , Van Dessel W. , Knapen A. , De Baets S.
Published: September 2005

Farmers in Europe want to control soil erosion in ways that are easily incorporated in their normal practices. We have investigated the possibility of reducing soil erosion by concentrated flow (i.e. rill and gully erosion) through increasing the root density of cereal crops.In situroot density measurements on cereal fields were combined with laboratory flume experiments on samples, taken in single‐ and double‐drilled fields, of which the above‐ground biomass was clipped. During the laboratory experiments no significant effect of root densities on critical shear stress or channel erodibility was observed because of interactions with other changing parameters (e.g. ageing effects). Therefore, the expected relative detachment rates as a function of plant root density were calculated using an empirical equation. During the first 75 days of the crop growth season relative soil detachment rates for single‐drilled field parcels can be reduced up to 50% compared with a rootless field, whereas relative soil detachment rates in double‐drilled field parcels can be reduced up to 60% in this period. Thereafter, plant roots in double‐drilled field parcels reduce relative soil detachment rates on average by 9% compared with single‐drilled field parcels (up to an absolute maximum of 90% compared with rootless soils). During the growing season, not only root density increases but also the vegetation cover changes, which enhances soil protection from erosion. Therefore, cereal roots will help to conserve the soil when seed is drilled at double rates, especially during the early growth stages and in fields with medium risk of concentrated flow.
Trace element distributions in soils developed in loess deposits from northern France
Authors: Sterckeman T. , Douay F. , Baize D. , Fourrier H. , Proix N. , Schvartz C. , Carignan J.
Published: September 2005

A pedo‐geochemical survey was carried out in the Nord‐Pas de Calais region (France) on soils developed in loess deposits. Total concentrations of Al, Fe and 18 trace elements, as well as common soil characteristics, were determined in samples from 52 surface and 97 deep horizons developed in these loess deposits. The Pb isotopic composition was determined in two sola. The composition of deep horizons, compared with that of the upper continental crust, with that of horizons developed from 21 other sedimentary rocks from the region and with that of loess from various parts of the world, confirms that loess from the Nord‐Pas de Calais region derives from multi‐recycled and well‐mixed ancient sedimentary rocks. Correlation analysis shows that least mobile (i.e. ionic potential (Z/r) is between 3 and 7) geogenic elements (Bi, Co, Cr, Cu, In, Ni, Pb, Sn, Tl, V, Zn) are associated with the fraction <2 µm (which we define as ‘lutum’). More mobile elements (As, Cd, Hg, Mn, Mo, Sb, Se) are less associated with this fraction. Cadmium is particularly linked to Mn. The distribution of [trace element]/([Al] or [Fe]) in the French loess gives the background content for soils developed from most sedimentary materials in northwestern Europe. Topsoils are enriched with all the trace elements examined, except Co, Cr and Ni. Enrichments with Cd, Cu, Mn and Zn are greater in cultivated soils than in forest soils. Enrichments with Pb and with Cu, Hg, Mo, Sb, Se and Sn are mainly due to human contamination through atmospheric fallout. Organic matter seems to act as a sink for all the exogenous trace elements.
Effect of ionic strength and clay mineralogy on Na–Ca exchange and the SAR–ESP relationship
Authors: Kopittke P. M. , So H. B. , Menzies N. W.
Published: September 2005

The relationship between sodium adsorption ratio (SAR) and exchangeable sodium percentage (ESP) for all soils has traditionally been assumed to be similar to that developed by the United States Salinity Laboratory (USSL) in 1954. However, under certain conditions, this relationship has been shown not to be constant, but to vary with both ionic strength and clay mineralogy. We conducted a detailed experiment to determine the effect of ionic strength on the Na+–Ca2+ exchange of four clay minerals (kaolinite, illite, pyrophyllite, and montmorillonite), with results related to the diffuse double‐layer (DDL) model. Clays in which external exchange sites dominated (kaolinite and pyrophyllite) tended to show an overall preference for Na+, with the magnitude of this preference increasing with decreasing ESP. For these external surfaces, increases in ionic strength were found to increase preference for Na+. Although illite (2:1 non‐expanding mineral) was expected to be dominated by external surfaces, this clay displayed an overall preference for Ca2+, possibly indicating the opening of quasicrystals and the formation of internal exchange surfaces. For the expanding 2:1 clay, montmorillonite, Na+–Ca2+ exchange varied due to the formation of quasicrystals (and internal exchange surfaces) from individual clay platelets. At small ionic strength and large ESP, the clay platelets dispersed and were dominated by external exchange surfaces (displaying preference for Na+). However, as ionic strength increased and ESP decreased, quasicrystals (and internal exchange surfaces) formed, and preference for Ca2+ increased. Therefore, the relationship between SAR and ESP is not constant and should be determined directly for the soil of interest.
Root dynamics and demography in shortgrass steppe under elevated CO2, and comments on minirhizotron methodology
Authors: Milchunas D. G. , Morgan J. A. , Mosier A. R. , LeCain D. R.
Published: September 2005

The dynamics and demography of roots were followed for 5 years that spanned wet and drought periods in native, semiarid shortgrass steppe grassland exposed to ambient and elevated atmospheric CO2 treatments. Elevated compared with ambient CO2 concentrations resulted in greater root‐length growth (+52%), root‐length losses (+37%), and total pool sizes (+41%). The greater standing pool of roots under elevated compared with ambient CO2 was because of the greater number of roots (+35%), not because individuals were longer. Loss rates increased relatively less than growth rates because life spans were longer (+41%). The diameter of roots was larger under elevated compared with ambient CO2 only in the upper soil profile. Elevated CO2 affected root architecture through increased branching.

Growth‐to‐loss ratio regressions to time of equilibrium indicate very long turnover times of 5.8, 7.0, and 5.3 years for control, ambient, and elevated CO2, respectively. Production was greater under elevated compared with ambient CO2 both below‐ and aboveground, and the above‐ to belowground ratios did not differ between treatments. However, estimates of belowground production differed among methods of calculation using minirhizotron data, as well as between minirhizotron and root‐ingrowth methods. Users of minirhizotrons may need to consider equilibration in terms of both new growth and disappearance, rather than just growth.

Large temporal pulses of root initiation and termination rates of entire individuals were observed (analogous to birth–death rates), and precipitation explained more of the variance in root initiation than termination. There was a dampening of the pulsing in root initiation and termination under elevated CO2 during both wet and dry periods, which may be because of conservation of soil water reducing the suddenness of wet pulses and duration and severity of dry pulses. However, a very low degree of synchrony was observed between growth and disappearance (production and decomposition).
The fate of 15N added to high Arctic tundra to mimic increased inputs of atmospheric nitrogen released from a melting snowpack
Authors: Tye A. M. , Young S. D. , Crout N. M. J. , West H. M. , Stapleton L. M. , Poulton P. R. , Laybourn‐Parry J.
Published: September 2005

Increases in the long‐range aerial transport of reactive N species from low to high latitudes will lead to increased accumulation in the Arctic snowpack, followed by release during the early summer thaw. We followed the release of simulated snowpack N, and its subsequent fate over three growing seasons, on two contrasting high Arctic tundra types on Spitsbergen (79°N). Applications of 15N (99 atom%) at 0.1 and 0.5 g N m−2 were made immediately after snowmelt in 2001 as either Na15NO3 or 15NH4Cl. These applications are approximately 1 × and 5 × the yearly atmospheric deposition rates. The vegetation at the principal experimental site was dominated by bryophytes and Salix polaris while at the second site, vegetation included bryophytes, graminoids and lichens. Audits of the applied 15N were undertaken, over two or three growing seasons, by determining the amounts of labeled N in the soil (0–3 and 3–10 cm), soil microbial biomass and different vegetation fractions.

Initial partitioning of the 15N at the first sampling time showed that ∼60% of the applied 15N was recovered in soil, litter and plants, regardless of N form or application rate, indicating that rapid immobilization into organic forms had occurred at both sites. Substantial incorporation of the 15N was found in the microbial biomass in the humus layer and in the bryophyte and lichen fractions. After initial partitioning there appeared to be little change in the total 15N recovered over the following two or three seasons in each of the sampled fractions, indicating highly conservative N retention. The most obvious transfer of 15N, following assimilation, was from the microbial biomass into stable forms of humus, with an apparent half‐life of just over 1 year. At the principal site the microbial biomass and vascular plants were found to immobilize the greatest proportion of 15N compared with their total N concentration. In the more diverse tundra of the second site, lichen species and graminoids competed effectively for 15NH4‐N and 15NO3‐N, respectively. Results suggest that Arctic tundra habitats have a considerable capacity to immobilize additional inorganic N released from the snow pack. However, with 40% of the applied 15N apparently lost there is potential for N enrichment in the surrounding fjordal systems during the spring thaw.
Recovery of Enterococcus faecalis after single‐ or multiple‐visit root canal treatments carried out in infected teeth ex vivo
Authors: Vivacqua‐Gomes N. , Gurgel‐Filho E. D. , Gomes B. P. F. A. , Ferraz C. C. R. , Zaia A. A. , Souza‐Filho F. J.
Published: September 2005

Aim  To assess the presence of Enterococcus faecalis after root canal treatment in single or multiple visits in an ex vivo model.

Methodology  Forty‐five premolar teeth were infected ex vivo with E. faecalis for 60 days. The canals were then prepared using a crowndown technique with System GT and Gates–Glidden burs and irrigated with 2% chlorhexidine gel. The specimens were divided into five groups (G1, G2, G3, G4 and G5) according to the time elapsed between chemical–mechanical preparation and root canal filling, the irrigant solution used and the use or nonuse of a calcium hydroxide intra‐canal medicament. The teeth were then root‐filled and incubated for 60 days at 37 °C. Dentine chips were removed from the canal walls with sequential sterile round burs at low speed. The samples obtained with each bur were immediately collected in separate test tubes containing Brain–Heart Infusion broth. These samples were placed onto agar plates and colony forming units were counted after 24 h at 37 °C. Data were ranked and analysed using the Kruskal–Wallis statistical test.

Results  Enterococcus faecalis was recovered from 20% (three of 15 specimens) of G1 (chlorhexidine irrigation and immediate root filling in a single visit), 25% (four of 15 specimens) of G2 (chlorhexidine irrigation and filling after 14 days use of a calcium hydroxide dressing in multiple visits), 40% (two of five specimens) of G3 (chlorhexidine irrigation and filling after 7 days), 60% (three of five specimens) of G4 (saline irrigation and filling after 7 days) and from 100% (five of five specimens) of G5 (saline irrigation and immediate filling without sealer).

Conclusions  Neither single‐ nor multiple‐visit root canal treatment ex vivo, eliminated E. faecalis completely from dentinal tubules. Up to 60 days after root filling, E. faecalis remained viable inside dentinal tubules. When no sealer was used, E. faecalis presented a higher growth rate.
Ex vivo evaluation of the capacity of the Tri Auto ZX to locate the apical foramen during root canal retreatment
Authors: Alves A. M. H. , Felippe M. C. S. , Felippe W. T. , Rocha M. J. C.
Published: September 2005

Aim  To evaluate ex vivo the capacity of the Tri Auto ZX to locate the apical foramen during root canal retreatment.

Methodology  The root canals of 62 maxillary and mandibular canines were prepared to a length 1 mm short of the apical foramen, to an apical size 35 using 1% sodium hypochlorite as an irrigant. Once prepared, the length of each tooth was measured directly using a size 15 K‐Flexofile introduced in the canal until the tip was visible at the apical foramen. After the file was removed, its length was recorded to a precision of 0.01 mm using a calliper. These direct lengths (DL) became the ‘gold standard’ for comparison with the electronic lengths (EL) derived from the Tri Auto ZX. After direct measurement, the tooth was measured electronically (EL1) and the canals were filled using lateral condensation of gutta‐percha cones and sealer. Seven days later the root filling was removed using solvent, Gates‐Glidden burs, and K‐files, and new electronic lengths determined (EL2). The electronic lengths (EL1 and EL2) were compared with the DL, and the differences were analysed statistically using the proportions test and Student's t‐test.

Results  At a tolerance limit of ±0.5 mm, EL1 coincided with the DL in 76% of cases. Lengths obtained in the presence of remnant of filling material (EL2) coincided in 81% of cases. The proportions test used to compare these percentages showed no statistically significant difference between EL1 and EL2 (P > 0.05). The Student's t‐test revealed a statistically significant difference (P < 0.05) between the means of the differences between DL/EL1 (−0.36 mm) and DL/EL2 (−0.04 mm).

Conclusion  The Tri Auto ZX was accurate to ±0.5 mm in more than 80% of teeth following removal of root fillings.
Survival of Enterococcus faecalis in root canals ex vivo
Authors: Sedgley C. M. , Lennan S. L. , Appelbe O. K.
Published: September 2005

Aim  The hypotheses tested in this study were that: (i) Enterococcus faecalis can survive long‐term entombment in root filled teeth without additional nutrients, (ii) initial cell density influences the survival of E. faecalis in instrumented root canals and (iii) gelatinase‐production capacity influences the survival of E. faecalis in root canals.

Methodology  The root canals of 150 extracted single canal teeth were instrumented to apical size 60 and divided into six groups of 25. Within each group 10 canals were inoculated with either gelatinase‐producing E. faecalis OG1‐S and the other 10 with its gelatinase‐defective mutant E. faecalis OG1‐X. Five canals per group were kept as uninoculated controls. The root canals in groups 1 and 2 were inoculated with 106 bacteria, incubated for 48 h at 37 °C then filled with gutta‐percha and zinc‐oxide eugenol sealer. Root canals were inoculated with 106, 105, 104 and 103 bacteria in groups 3–6, respectively, and left unfilled. All teeth were sealed coronally with glass–ionomer cement. After 6‐ (groups 1, 3–6) and 12‐month (group 2) incubation at 37 °C in 100% humidity, root fragments were analysed for presence of E. faecalis, using culture, polymerase chain reaction and histological methods.

Results  Viable E. faecalis was recovered from all root filled teeth and from 95–100% of unfilled inoculated teeth. Initial cell density and gelatinase production did not influence the recovery of viable E. faecalis (P > 0.05; chi‐square test). Enterococcus faecalis 16S rRNA gene products were present in all inoculated teeth and absent in all noninoculated controls. Dentinal tubule infection was evident under light microscopy in sections from inoculated teeth after 48‐h, 6‐ and 12‐month incubation.

Conclusions  Enterococcus faecalis inoculated into root canals maintained viability for 12‐months ex vivo. The clinical implications are that viable E. faecalis entombed at the time of root filling could provide a long‐term nidus for subsequent infection.
Weight management: a survey of current practice in secondary care NHS settings in 2004
Authors: Leslie W. S. , Hankey C. R. , McCombie L. , Lean M. E. J.
Published: September 2005

Objective  To determine the current practices in relation to weight management currently provided for overweight/obese patients attending different  secondary care outpatient clinics. 

Methods  Postal questionnaire sent to 100 consultant clinicians working in a range of specialist areas in three NHS Trust areas in Scotland, between January and March 2004.

Results  Overall response rate was 55%. Only 9% (five) of clinicians reported having a protocol in place for the management of patients who were overweight or obese. Lack of expertise and inaccessibility to expertise were cited frequently as reasons for having no protocol in place. Fifty‐one per cent felt that weight management (including obesity treatment) should be undertaken by a specialist service either run by general practitioners (GPs), or by clinicians in a secondary care setting. Around a third of all  those  surveyed  reported  willingness  to  incorporate  obesity management  within  their  own routine specialty practice.

Conclusion  Clinicians acknowledged the adverse health effects of obesity within their specialist area, but felt unskilled and under‐resourced to provide effective management. Effective prevention and management are required to challenge the obesity epidemic and will require the involvement of both primary and secondary care NHS settings. It is encouraging that a third of respondents felt prepared to incorporate obesity and weight management within their routine specialist practice.
Insights into creation and use of prescribing documentation in the hospital medical record
Authors: Tully Mary P. , Cantrill Judith A.
Published: September 2005

Rationale, aims and objectives  Extraction of prescribing data from medical records is a common, albeit flawed, research method. Yet little is known about the processes that result in those data. This study explores the creation and use of prescribing documentation in the medical record, from the perspective of the hospital doctors who both create and use it.

Methods  Thirty‐six hospital doctors were purposively selected for qualitative interviews, giving a maximum variability sample of grades of doctors across the range of major medical specialty areas and medical teams at a large teaching hospital in England.

Results  The findings suggest a number of reasons why hospital doctors fail to record prescribing decisions in the medical record. There was no set standard, record keeping was not formally taught and the hurried environment of the ward gave little time for documentation. The doctors also acknowledged that there was no need for completeness, as colleagues would be able to ‘fill in the gaps’ via an inferential process.  Assumptions  were  made  and  although  this  was  not  seen  as  ideal, it was recognized as necessary if work was to be done efficiently.

Conclusion  These results reinforce the suggestion that, despite the large number of potential users, the medical record is created for those with the right privileged knowledge. This has profound implications for those without that insider knowledge who are using medical records for research purposes.

Funding  This work was funded by a North West Regional National Health Service Postdoctoral Fellowship.
Evaluating national guidelines for prevention of cardiovascular disease in primary care
Authors: Marshall Tom
Published: September 2005

Introduction  National guidelines for prevention of cardiovascular disease make different recommendations in relation to screening and treating patients with aspirin, antihypertensive treatment and statins. The resource cost and health implications of these differences are quantified in this paper.

Data sources  Guidelines were obtained from Australia, New Zealand, Canada, UK and USA. Effectiveness data were obtained from published sources, costs and a model population of 2000 patients from US sources.

Method  The resource costs and health effects of screening and treating a standard population of 2000 persons were determined for each of the five national guidelines. Costs and effects were calculated over a 5‐year time horizon and cost‐effectiveness determined cost per cardiovascular event prevented.

Results  Cost per cardiovascular event prevented is lowest in older patients and very high under 35. The New Zealand guidelines are more cost‐effective of the national guidelines, however, they would be more effective if they incorporated US recommendations on the use of aspirin. Further antihypertensive treatment is the least cost‐effective of the interventions considered.

Discussion  Cardiovascular disease prevention guidelines should focus on older rather than younger patients. Treatment eligibility should be informed more by risk than by individual risk factor status. Guidelines should put greater emphasis on the use of aspirin and initial antihypertensive treatment than on achieving blood pressure targets.

Conclusion  In order to justify their recommendations guidelines should quantify the resource implications in relation to the health benefits.
Capturing the full measure of patient outcome improvement using a self‐assessed health adjustment
Authors: Long Michael J. , McQueen David A. , Lescoe‐Long Mary , Schurman John R.
Published: September 2005

Rationale  Self‐assessed health (SAH) status is a very simple four‐, or five‐category self‐reported measure of health status that has been shown to be a powerful predictor of mortality, service use and total cost of medical care treatment. It is therefore reasonable to suggest that pre‐intervention SAH may influence the extent to which patient outcomes improve following surgery.

Methods  Using the four‐category measure of SAH of Excellent; Good; Fair; Poor, we developed an adjustment factor based on the mean improvement  of  the  SAH  category  relative  to  the  mean  improvement  of the overall sample.

Results  The results clearly  indicate  that  the  higher  patients  rated  their  pre‐operative  health, the greater their pre–post‐operative improvement. Adjusting the outcome improvement by this SAH factor  provides  for  the  adjustment  of  the  overall  sample  results  by  extent to which each category of SAH contributes  to  the  overall  mean.  

Conclusion  The results indicate that by adjusting patient outcome improvement measures by a factor based on pre‐intervention SAH, overall sample patient outcome improvement increased 5.8%. The results also indicate that failure to adjust for pre‐intervention SAH will result in an understatement of patient outcome improvement following surgery.
Henneguya pagri n. sp. (Myxozoa: Myxosporea) causing cardiac henneguyosis in red sea bream, Pagrus major (Temminck & Schlegel)
Authors: Yokoyama H , Itoh N , Tanaka S
Published: September 2005

Henneguya pagri n. sp. (Myxozoa: Myxosporea) is described from netpen‐cultured red sea bream, Pagrus major, in Japan. Affected fish displayed anaemic gills, an enlarged bulbus arteriosus and internal haemorrhaging in the pericardial cavity. Disease outbreaks occurred during the summer and the prevalence of infection reached 75% in August. Plasmodia of H. pagri developed in the bulbus arteriosus of red sea bream, in which degenerative cardiomyopathy was observed. Following maturation of the parasite, the influx of spores into the gills caused congestion of the gill capillaries, resulting in proliferative branchitis. Spores (10.5 × 7.5 μm) were ovoid with two caudal appendages (29.6 μm in average length), with a whip‐like extension from the end. Partial small subunit ribosomal RNA gene sequences of H. pagri are closely related to those of H. lateolabracis infecting the bulbus arteriosus of Chinese sea bass, Lateolabrax sp.
Organelle interactions and possible degradation pathways visualized in high‐pressure frozen algal cells
Authors: AICHINGER N. , LÜTZ‐MEINDL U.
Published: September 2005

Organelle interactions, although essential for both anabolic and catabolic pathways in plant cells have not been examined in detail so far. In the present study the structure of different organelle–organelle, organelle–vesicle and organelle–membrane interactions were investigated in growing and nongrowing cells of the green alga Micrasterias denticulata by use of high pressure freeze fixation and energy filtering transmission electron microscopy. It became clear that contacts between mitochondria always occur by formation of a cone‐shaped protuberance of one of the mitochondria which penetrates into its fusion partner. In the same way, structural interactions between mitochondria and mucilage vesicles and between microbodies and mucilage vesicles are achieved. Lytic compartments contact mitochondria or mucilage vesicles again by forming protuberances and by extending their contents into the respective compartment. Detached portions of mitochondria are found inside lytic compartments as a consequence of such interactions. Mitochondria found in contact with the plasma membrane reveal structural disintegration. Our study shows that interactions of organelles and vesicles are frequent events in Micrasterias cells of different ages. The interactive contacts between lytic compartments and organelles or vesicles suggest a degradation pathway different from autophagy processes described in the literature. Both the interactions between vesicles and organelles and the degradation pathways occur independently from cytoskeleton function as demonstrated by use of cytochalasin D and the microtubule inhibitor amiprophos‐methyl.
Atomic force microscopy investigation of the dependence of cellular elastic moduli on glutaraldehyde fixation
Authors: HUTTER J. L. , CHEN J. , WAN W. K. , UNIYAL S. , LEABU M. , CHAN B. M. C.
Published: September 2005

The atomic force microscope (AFM) has provided nanoscale analyses of surfaces of cells that exhibit strong adhesive and cell spreading properties. However, it is frequently reported that prior fixation is required for reliable imaging of cells with lower adhesive properties. In the present study, the AFM is used to assess the effects of fixation by glutaraldehyde on the elastic modulus of a human rhabdomyosarcoma transfectant cell line RDX2C2. Our results show a sharp increase in the elastic modulus for even mild fixation (0.5% glutaraldehyde for 60 s), accompanied by a dramatic improvement in imaging reproducibility. An even larger increase is seen in NIH‐3T3 mouse fibroblasts, although in that case fixation is not typically necessary for successful imaging. In addition, our results suggest that treatment with glutaraldehyde restricts the content of the resulting images to features nearer to the cell surface.