bluuebunny/crossref_metadata_2025_split huggingface dataset:
Total lipid extracts from characteristic soil horizons in a podzol profile
Authors: Naafs D. F. W. , Van Bergen P. F. , De Jong M. A. , Oonincx A. , De Leeuw J. W. 
Published: November 2004

SummaryThe podzolization process is studied through lipids in nine characteristic podzol horizons. Organic matter accumulates particularly with aluminium in the Bh horizon, while the hard, cemented Bs horizon below this is formed mainly by iron oxides. The low soil pH seems to have no great influence on the preservation of lipids as reflected by the absolute amounts present and the presence of bacterial lipid markers throughout the profile. Independent of soil pH, lipids accumulate in organically enriched horizons. Albeit, high molecular weight organic compounds accumulate to a relatively greater extent than lipids in these horizons. A lipid signal related to the aerial parts, i.e. leaves and flowers, of Calluna is observed only in the O horizon. This ‘n‐alkane, steroid and triterpenoids’ signal is quickly lost in the underlying Ah horizon due to (bacterial) oxidation. The other total lipid extracts obtained are dominated by root‐derived compounds. In subsoil horizons rich in organic matter, i.e. the Ahb and Bh horizons, root‐derived friedooleanan and steroid compounds dominate the total lipid signal. Degraded horizons, poor in organic matter, i.e. the E2, Bhs, Bs and B/C horizons, are dominated by C22 and C24ω‐hydroxy acids, long‐chain (> C20) n‐alkanoic acids with a strong even‐over‐odd predominance and C22 and C24n‐alkanols. Steroid and root‐derived triterpenoids with a friedooleanan structure have been removed from these horizons through degradation. Based on total organic carbon content and lipid composition, the formation of an E1 horizon has started, but is not yet complete. In the Ahb horizon, a contribution from buried vegetation to the total lipid signal is still present, although degradation and an input from roots have significantly altered the original signal. Overall, lipid data indicate that degradation (microbial oxidation) is an important process that should be taken into account, in addition to leaching, when describing podzolization processes in soils.
A transfer‐function method for analysing breakthrough data in the time domain of the transport process
Authors: Mojid M. A. , Rose D. A. , Wyseure G. C. L. 
Published: November 2004

SummaryA transfer‐function method is proposed to determine transport parameters from solute breakthrough data. The method is based on the assumptions that a linear process governs the transport of solute through soil and that the soil is homogeneous. It needs breakthrough data at two different vertical locations from a pulse input of solute to the soil. The method predicts the response by convoluting the input with the transfer function in the time domain.Solute breakthrough data were measured in unsaturated soil columns by time‐domain reflectometry (TDR). An experimental soil column was placed over a supporting column filled with sandy soil. A constant hanging water table, maintained in the lower column, created suction in the upper column and maintained unsaturated conditions. A solution of calcium chloride (CaCl2) was spread over the soil in the upper column during steady flow of water in the column. Resident concentrations of solute in terms of electrical conductivity were measured at two depths by TDR sensors.We analysed breakthrough curves of CaCl2 in 81 experiments to determine the transport parameters in coarse sand, sandy loam soil and clay loam soil by the transfer‐function method. The transport parameters obtained were compared with those determined by the widely used deterministic equilibrium model of the CXTFIT program. The transfer‐function method provided a better fit between the measured and estimated breakthrough curves in almost all cases and resulted in stable values of the parameters. The method is robust against small errors in measurements. It is a mathematically sound and efficient method for analysing breakthrough data.
Calibrating soil respiration measures with a dynamic flux apparatus using artificial soil media of varying porosity
Authors: Butnor J.R. , Johnsen K.H. 
Published: November 2004

SummaryMeasurement of soil respiration to quantify ecosystem carbon cycling requires absolute, not relative, estimates of soil CO2 efflux. We describe a novel, automated efflux apparatus that can be used to test the accuracy of chamber‐based soil respiration measurements by generating known CO2 fluxes. Artificial soil is supported above an air‐filled footspace wherein the CO2 concentration is manipulated by mass flow controllers. The footspace is not pressurized so that the diffusion gradient between it and the air at the soil surface drives CO2 efflux. Chamber designs or measurement techniques can be affected by soil air volume, hence properties of the soil medium are critical. We characterized and utilized three artificial soils with diffusion coefficients ranging from 2.7 × 10−7 to 11.9 × 10−7 m2 s−1 and porosities of 0.26 to 0.46. Soil CO2 efflux rates were measured using a commercial dynamic closed‐chamber system (Li‐Cor 6400 photosynthesis system equipped with a 6400‐09 soil CO2 flux chamber). On the least porous soil, small underestimates (< 5%) of CO2 effluxes were observed, which increased as soil diffusivity and soil porosity increased, leading to underestimates as high as 25%. Differential measurement bias across media types illustrates the need for testing systems on several types of soil media.
Effects of glucose and rhizodeposits (with or without cysteine‐S) on immobilized‐35S, microbial biomass‐35S and arylsulphatase activity in a calcareous and an acid brown soil
Authors: Dedourge O. , Vong P.‐C. , Lasserre‐Joulin F. , Benizri E. , Guckert A. 
Published: November 2004

SummaryOur aim was to study the effects of C (as glucose and artificial rhizodeposits) on S immobilization, in relation to microbial biomass‐S and soil arylsulphatase (ARS) activity, in contrasting soils (a calcareous and an acid brown soil). The glucose‐C and artificial rhizodeposit‐C with or without cysteine were added at six rates (0, 100, 200, 400, 600 and 800 mg kg−1 soil) to the two soils and then incubated with Na235SO4 for 1 week prior to analysis. The percentages of 35S immobilized increased when C as glucose and rhizodeposit (without cysteine) were added to both soils. With cysteine‐containing rhizodeposit, the percentages of 35S immobilized remained relatively stable (23.5% to 29.9%) in the calcareous soil, but decreased in the acid brown soil (52.7% to 31.5%). For both soils, cysteine‐containing rhizodeposit additions showed no significant correlation between immobilized‐35S and microbial biomass‐35S, suggesting that microorganisms immobilized cysteine‐S preferentially instead of 35S from the tracer (Na235SO4). In the calcareous soil, a positive and significant correlation was found between ARS activity and microbial biomass‐35S (r = 0.85, P < 0.05) when glucose was added. We also saw this correlation in the acid brown soil when rhizodeposit‐C without cysteine was added (r = 0.90, P < 0.05). Accordingly, the results showed the presence of extracellular arylsulphatase activity of 48.7 mg p‐nitrophenol kg−1 soil hour−1 in the calcareous soil and of 27.0 mg p‐nitrophenol kg−1 soil hour−1 in the acid brown soil.
Factors regulating diversity and abundance of fish communities in Pantanal lagoons, Brazil
Authors: Súarez Yzel Rondon , Petrere Miguel , Catella Agostinho Carlos 
Published: November 2004

AbstractThe factors effecting fish species richness, evenness and relative abundance in 19 floodplain lagoons in the Pantanal (Brazil) were examined. Richness and evenness were strongly correlated with the lagoon's: (i) isolation time from the main river; (ii) depth; and (iii) distance from the main river. Abundance of the five dominant fish species was correlated mainly with: (a) macrophyte cover; (b) the distance from the main river; and (c) piscivore abundance. These results suggest that the species select lagoons to avoid or minimize their confinement in inappropriate floodplain habitats. A combination of strategies, together with variations in the lagoon's connection period, determines the diversity and abundance of the fish species in the Nhecolândia Pantanal.
Gear‐based management of a tropical artisanal fishery based on species selectivity and capture size
Authors: McClanahan T. R. , Mangi S. C. 
Published: November 2004

AbstractThe population density, species composition and lengths of fish landed by artisanal fishermen using six types of gear: large and small traps, gill nets, hand lines, spears and beach seines were studied in the multi‐species fishery of southern Kenya. Selectivity and catch composition among gears were determined by studying the species richness, diversity, size and mean trophic level of the catches for each gear type, to develop gear‐based management recommendations for this artisanal reef lagoon fishery. One hundred and sixty‐three reef and reef‐associated species from 37 families were recorded in the catch. Beach seines and small traps accounted for the highest number of fish landed (34–35 individuals per fisherman per day). These gears also caught smaller fish than big traps, spears and gill nets. Beach seines caught the highest number of species (14 ± 7 species per day) while most other gears caught four to five species per day with no differences between gears. Predatory species with a mean trophic level of 3.6 dominated catches from hand lines, while the mean trophic level of the other gears was low and ranged from 2.6 to 2.9 with no differences between the gears. The high diversity and small size of fish caught in beach seines indicates that its selectivity overlapped most with large traps and gill nets. Spears and small traps also showed high similarity in species selectivity and small traps captured the smaller mean size of fish, indicating that they are likely to pre‐empt the resource of spears. Large traps, hand lines and spears catch the largest individuals and the species composition of the catch differed sufficiently such that their selectivity should overlap the least and may, therefore, be the preferred mix of gears. The elimination or reduction of beach seines and small traps should reduce the catch of small fish and overlap in selectivity among the existing gears.
Age‐specific patterns in density‐dependent growth of white crappie, Pomoxis annularis
Authors: Pope K. L. , Wilde G. R. , Durham B. W. 
Published: November 2004

AbstractThe relationship between growth in white crappie, Pomoxis annularis Rafinesque, and climate, lake morphometry and population density was studied in 103 Texas reservoirs. Growth of age‐0 through age‐3 white crappie was significantly (P≤0.05) related to latitude, growing season and surface area. Growth of age‐1 through age‐5 white crappie also was related to annual precipitation. Multiple linear regression models with precipitation and mean catch per unit effort (CPUE) of white crappie as independent variables explained 14–22% of the variation in growth of age‐0, ‐1 and ‐2 white crappie. By contrast, growth of age‐3, ‐4 and ‐5 white crappie was unrelated to CPUE. Apparently, between age 2 and 3, the density of white crappie in Texas reservoirs falls below a density‐dependent growth threshold beyond which growth is no longer related to density. This density‐dependent threshold was most likely related to angler harvest of larger, older white crappie.
Temperature and depth associations of porbeagle shark (Lamna nasus) in the northwest Atlantic
Authors: Campana S. E. , Joyce W. N. 
Published: November 2004

AbstractThe porbeagle (Lamna nasus) is a large fast‐swimming pelagic shark found at high latitudes in both hemispheres. To examine the influence of temperature on porbeagle distribution, a detailed analysis of the relationship between catch rate, temperature, depth and location was carried out based on 420 temperature profiles taken during commercial fishing operations. More than half of the porbeagle were caught at temperatures of 5–10°C (at the depth of the hook); the mean temperature at gear of 7.4°C differed very little among seasons. Most of the spring fishing took place near fronts, although the affinity with fronts was not evident in the fall. Temperature at depth was a significant modifier of catch rate when included in a generalized linear model controlling for the effects of location, fishing vessel, month and year. However, sea surface temperature was a poor predictor of catch rate. The similarity between environmental and catch‐weighted cumulative distribution functions confirmed suggestions that fishers sought out the most appropriate temperature range in which to set their gear. As porbeagle are among the most cold tolerant of pelagic shark species, we suggest that they have evolved to take advantage of their thermoregulating capability by allowing them to seek out and feed on abundant coldwater prey in the absence of non‐thermoregulating competitors.
Thermal habitat experienced by Atlantic salmon (Salmo salar L.) kelts in coastal Newfoundland waters
Authors: Reddin David G. , Friedland Kevin D. , Downton Peter , Brian Dempson J. , Mullins Conrad C. 
Published: November 2004

AbstractThermal habitat was recorded by data storage tags (DSTs) applied to Atlantic salmon (Salmo salar L.) kelts during their seaward migration in the spring of 1998 at enumeration facilities in Highlands River, Humber River, Western Arm Brook, and Campbellton River, Newfoundland. In total, 139 DSTs were applied and data were downloaded from eleven of the recovered tags. The recovered tags had been applied at Highlands, Campbellton and Western Arm rivers and recovered in the coastal waters of Newfoundland and Québec and at the enumeration facilities at Highlands and Campbellton rivers. Water temperatures experienced by the fish were recorded for periods of 62–118 days at resolutions of 15–30 min. The data from the sea record on the DSTs were analysed for temperature patterns in relation to migration behaviour and diurnal movement of the fish. A variety of patterns were exhibited on the temperature records suggesting that the fish were behaving in various ways at different times. For Campbellton and Highlands fish over the course of some 24 h periods, night‐time temperatures changed little and were among the highest daily temperatures experienced by the fish, whereas daytime temperatures often showed dramatic and frequent shifts in temperature presumably as the fish rapidly and frequently changed depth. For the Western Arm Brook fish, rapid fluctuations in temperature occurred sometimes during the day and night without a consistent diurnal pattern. We also considered large‐scale aspects of the data by examining oceanographic conditions in relation to the temperatures recorded by the tags.
Studying spatial and temporal dynamics of sward structure at low stocking densities: the use of an extended rising‐plate‐meter method
Authors: Correll O. , Isselstein J. , Pavlu V. 
Published: November 2004

AbstractAn extended rising‐plate‐meter method was used to study the spatial and temporal variability of the sward structure of extensively managed pastures over a grazing season. Two treatments of a long‐term grazing experiment with heifers were investigated: extensive continuous grazing (EG) with a target sward height of 10 cm and intensive continuous grazing (IG) with a target sward height of 5 cm. Compressed sward height and related herbage mass (HM), dominant plant species and stage of development of phenology were determined at weekly or twice weekly intervals at fixed measuring points. The results demonstrated a strong variability in sward height and HM, especially on the EG treatment. The botanical composition of the standing herbage differed between treatments and between patches of different heights within the same treatment. In areas with a short sward, the herbage was predominantly composed of Agrostis capillaris, Festuca rubra and Trifolium repens. It was more evenly composed and also included taller growing species, such as Alopecurus pratensis and Galium mollugo, in areas with a tall sward. The area potentially available for reproductive development was high in the EG treatment and low in the IG treatment. The method employed proved suitable to provide a detailed description of the dynamics of the sward structure.
Assessment of seasonal dry‐matter yield and quality of grass swards with imaging spectroscopy
Authors: Schut A. G. T. , Ketelaars J. J. M. H. 
Published: November 2004

AbstractThe potential of imaging spectroscopy for the assessment of seasonal dry‐matter (DM) yield and sward quality was studied. Relationships between spatial heterogeneity of tiller density, light interception, ground cover and seasonal DM yield were developed. Sward heterogeneity was quantified by the spatial standard deviation of ground cover and of logarithmically transformed ground cover, and patterns in ground cover transects were quantified by wavelet entropy. An experiment was conducted with eight control (C) swards, eight naturally damaged (ND) swards and twelve artificially damaged (AD) swards. Swards were established in containers and spectroscopic images were recorded twice weekly.Seasonal DM yield was linearly related to a combination of means of ground cover and index of reflection intensity (r2 = 0·93). Spatial variation of tiller density was larger for AD and ND swards than for C swards. Values of the spatial standard deviation of ground cover and wavelet entropy were larger for AD and ND swards than for C swards. A single spatial standard deviation of ground cover value of 13% discriminated ND and AD swards from C swards. Seasonal means of wavelet entropy (r2 = 0·70) and the spatial standard deviation of ground cover (r2 = 0·63) at harvest were linearly related to seasonal DM yield. It is concluded that imaging spectroscopy can be used for assessing seasonal DM yield and sward heterogeneity.
Evaluation of the effect of 17αOH‐progesterone and 17β‐oestradiol on human sperm ability to fuse with oocytes: comparison and possible interference with the effect of progesterone
Authors: Francavilla F. , Romano R. , Pandolfi C. , Macerola B. , Santucci R. , Necozione S. , Francavilla S. 
Published: November 2004

SummaryThe demonstration of a stimulatory effect of progesterone (P) on the sperm/oocyte fusion has provided the most relevant biological evidence of the effect of P on sperm functions involved in fertilization. Some evidence exists that 17α‐hydroxyprogesterone (17αOH‐P) and 17β‐oestradiol (17β‐E2), could also exert non‐genomic effects on human spermatozoa and a role for 17β‐E2 as a possible physiological modulator of P action on spermatozoa has been suggested. This study aimed to determine the effect of the exposure of human spermatozoa to 17αOH‐P and 17β‐E2 on sperm/oocyte fusion as well as the possible interference of 17β‐E2 with the effect of P. The effect of steroids on sperm/oocyte fusion was assessed by means of the hamster egg penetration test (HEPT). The exposure of capacitated sperm suspensions to scalar doses of 17αOH‐P produced a significant enhancement of penetrations/oocytes with a dose/response effect. It was equal to 75.3% of that produced by equimolar doses of P. Conversely, 17β‐E2 (from 100 nM to 50 μM) did not produce any significant effect when added either before or after capacitation. Moreover, the sperm pre‐incubation with 17β‐E2 did not interfere with the stimulatory effect of P. These results support a physiological role for 17OH‐P in the process of fertilization, but not a role for 17β‐E2 as a possible physiological modulator of P action on spermatozoa.
Effects of Ca‐ATPase inhibitors on the intracellular calcium activity and motility of human spermatozoa
Authors: Williams K. M. , Ford W. C. L. 
Published: November 2004

SummaryAlthough evidence suggests that high intracellular calcium activity ([Ca2+]i) inhibits sperm motility, data concerning [Ca2+]i within, or slightly above, the physiological range are sparse, particularly in mammalian sperm. We investigated inhibitors of the sarcoplasmic/endoplasmic reticulum Ca‐ATPase (SERCA) and the plasma membrane Ca‐ATPase with the objective of increasing the intracellular calcium ion activity in human spermatozoa to study its effect on motility and other functions. Thapsigargin (20 μmol/L) increased [Ca2+]i from 140 ± 7 nmol/L over a ∼2‐min period to reach a plateau of 530 ± 84 nmol/L (mean ± SEM, n = 3, p < 0.05). In sperm suspended in calcium‐free medium thapsigargin increased [Ca2+]i from 13 ± 3.3 to 35 ± 7.5 nmol/L (p < 0.01), consistent with the release of calcium from intracellular stores. Cyclopiazonic acid (60 μmol/L) caused a transient decrease in [Ca2+]i. Quercetin, (200 μmol/L) caused a rapid increase in [Ca2+]i to 1280 ± 90 nmol/L, after which [Ca2+]i fell quickly at first but then more slowly. Thapsigargin (20 μmol/L) caused ∼70% of sperm to acrosome react in≤5 min, but once acrosome reacted, many sperm died over the next 30 min. Lower concentrations of thapsigargin caused fewer acrosome reactions but were less toxic. Both thapsigargin and quercetin caused rapid dose‐dependent decreases in sperm motility. The results are consistent with high [Ca2+]i in the range observed in caput epididymal or cryopreserved spermatozoa inhibiting motility, but might be confounded by other events following the acrosome reaction.
Distribution of marine birnavirus in cultured marine fish species from Kagawa Prefecture, Japan
Authors: Isshiki T , Nagano T , Kanehira K , Suzuki S 
Published: November 2004

AbstractTo determine the distribution of marine birnavirus (MABV) in cultured populations of different marine fish species, 1291 pooled tissue samples from 2672 fish belonging to 22 species and one hybrid were collected from Kagawa Prefecture, Japan, during 1999–2001. Using cell‐culture MABV was isolated from three species: yellowtail, Seriola quinqueradiata Temminck & Schlegel (positive number/sample number, 10/419), amberjack, S. dumerili (Risso) (4/72), and Japanese flounder, Paralichthys olivaceus (Temminck & Schlegel) (41/481). Using PCR on MABV‐negative samples, the MABV genome was detected in the same three species [yellowtail (9/409), amberjack (4/68) and Japanese flounder (93/440)] and two additional species, spotted halibut, Verasper variegatus (Temminck & Schlegel) (5/11), and goldstriped amberjack, S. lalandi Valenciennes (1/5). These MABV‐positive species can be taxonomically divided into two groups: the genus Seriola and flatfish. In Japanese flounder, MABV was detected during all seasons, and the infection rate was correlated with water temperature. Aquaculture sites with MABV‐positive fish were evenly distributed over the surveyed area, suggesting that MABV is widely distributed at aquaculture sites in Kagawa Prefecture. The nucleotide sequence at the variable region, the VP2/NS junction, revealed that the 39th base mutation occurs host‐specifically for flatfish. Flatfish are suspected to be the main reservoir of MABV and might be responsible for establishing the infection cycle in aquaculture environments.