bluuebunny/crossref_metadata_2025_split huggingface dataset:
Avian foraging studies: an overlooked source of distribution data for macroecological and conservation studies
Authors: Grim Tomas 
Published: May 2006

ABSTRACTMacroecological and biogeographical studies and their applicability for biological conservation vitally depend on distribution data. These are usually taken from distribution atlases and databases or maps found in identification guides. A previous study pointed to another little explored source of data — local faunistic studies. Here, I would like to draw attention to another potential source. Papers that analysed the food composition of some taxa (e.g. insectivorous birds) are an overlooked source of rich information on taxa distributions. These studies frequently include an ‘Appendix’ with a list of food items determined to the species level. These studies also contain data on abundances, number of samples, sampling time, and geographical location as a rule. Foraging birds naturally provide data on invertebrate distributions with good spatio‐temporal coverage and reasonably large samples. Importantly, birds frequently collect rare and by entomological methods hardly detectable species (i.e. those living high, in tree canopies, in very dense vegetation, or with secretive lifestyle). Data from bird dietary studies may help to ameliorate one of the most serious problems in distribution studies — zero inflation. I briefly discuss pros and cons of this so far neglected source of biogeographical data.
Mortality risk score in liver transplantation: Changes over time in its predicting power
Authors: Del Pino Mariana , Cervio Guillermo , Dip Marcelo , Giannivelli Silvina , Buamscha Daniel , Ciocca Mirta , García de Dávila Maria Teresa , Imventarza Oscar , Lejarraga Horacio 
Published: May 2006

Abstract:  Since the onset of our liver transplantation program in 1992, 362 transplants were performed in 338 children. A risk score for predicting mortality was designed and implemented over time. The description of a method utilized to design the risk score, changes in mortality rate over 12 yr and the analysis of factors that might have influenced these changes are presented and discussed in this paper.Patients and methods:  Cox regression analysis was applied to a retrospective sample of 110 patients with liver cirrhosis, transplanted between 1992 and 2000. A risk score was prepared using β coefficients of the two significant variables related to survival time: age (1.08, p=0.02) and bilirubin levels (0.93, p=0.03), and two groups were identified: low‐ and high‐risk score. The score was applied in two consecutive samples: 2000–2002 and 2002–2004.Results:  In the first sample (1992–2000), we found 69 and 41 as low‐ and high‐risk patients, with a median survival time of 93.13 and 2.93 months (p=0.0001). In the 2000–2002 sample, a median survival time of 41.7 and 2.33 months (p=0.03) was found for low‐ and high‐risk groups, respectively. In the third sample (2002–2004), there was a remarkable decrease in mortality in the high‐risk group (n=29) and the score did not discriminate between high‐ and low‐risk groups (p=0.35).Conclusion:  A scoring system to identify risk levels in liver transplantation patients is an operative and powerful tool during a given period of time but it has to be updated as risk factors will vary following the team's learning curve.
Treeline dynamics in relation to climatic variability in the central Tianshan Mountains, northwestern China
Authors: Wang Ting , Zhang Qi‐Bin , Ma Keping 
Published: May 2006

ABSTRACTAim  Climate variability may be an important mediating agent of ecosystem dynamics in cold, arid regions such as the central Tianshan Mountains, north‐western China. Tree‐ring chronologies and the age structure of a Schrenk spruce (Picea schrenkiana) forest were developed to examine treeline dynamics in recent decades in relation to climatic variability. Of particular interest was whether tree‐ring growth and population recruitment patterns responded similarly to climate warming.Location  The study was conducted in eight stands that ranged from 2500 m to 2750 m a.s.l. near the treeline in the Tianchi Nature Reserve (43°45′−43°59′ N, 88°00′−88°20′ E) in the central Xinjiang Uygur Autonomous Region, northwestern China.Methods  Tree‐ring cores were collected and used to develop tree‐ring chronologies. The age of sampled trees was determined from basal cores sampled as close as possible to the ground. Population age structure and recruitment information were obtained using an age–d.b.h. (diameter at breast height) regression from the sampled cores and the d.b.h. measured on all trees in the plots. Ring‐width chronologies and tree age structure were both used to investigate the relationship between treeline dynamics and climate change.Results  Comparisons with the climatic records showed that both the radial growth of trees and tree recruitment were influenced positively by temperature and precipitation in the cold high treeline zone, but the patterns of their responses differed. The annual variation in tree rings could be explained largely by the average monthly minimum temperatures during February and August of the current year and by the monthly precipitation of the previous August and January, which had a significant and positive effect on tree radial growth. P. schrenkiana recruitment was influenced mainly by consecutive years of high minimum summer temperatures and high precipitation during spring. Over the last several decades, the treeline did not show an obvious upward shift and new recruitment was rare. Some trees had established at the treeline at least 200 years ago. Recruitment increased until the early 20th century (1910s) but then decreased with poor recruitment over the past several decades (1950–2000).Main conclusions  There were strong associations between climatic change and ring‐width patterns, and with recruitments in Schrenk spruce. Average minimum temperatures in February and August, and total precipitation in the previous August and January, had a positive effect on tree‐ring width, and several consecutive years of high minimum summer temperature and spring precipitation was a main factor favouring the establishment of P. schrenkiana following germination within the treeline ecotone. Both dendroclimatology and recruitment analysis were useful and compatible to understand and reconstruct treeline dynamics in the central Tianshan Mountains.
Simultaneous Wavelet Deconvolution in Periodic Setting
Authors: DE CANDITIIS DANIELA , PENSKY MARIANNA 
Published: May 2006

Abstract.  The paper proposes a method of deconvolution in a periodic setting which combines two important ideas, the fast wavelet and Fourier transform‐based estimation procedure of Johnstone et al. [J. Roy. Statist. Soc. Ser. B66 (2004) 547] and the multichannel system technique proposed by Casey and Walnut [SIAM Rev. 36 (1994) 537]. An unknown function is estimated by a wavelet series where the empirical wavelet coefficients are filtered in an adapting non‐linear fashion. It is shown theoretically that the estimator achieves optimal convergence rate in a wide range of Besov spaces. The procedure allows to reduce the ill‐posedness of the problem especially in the case of non‐smooth blurring functions such as boxcar functions: it is proved that additions of extra channels improve convergence rate of the estimator. Theoretical study is supplemented by an extensive set of small‐sample simulation experiments demonstrating high‐quality performance of the proposed method.
CYTOTAXONOMIC STUDIES IN HOLCUS
Authors: JONES KEITH 
Published: May 2006

summaryStudies have been made of the relative frequency and distribution in parts of Britain of the chromosome races of Holcus mollis (2n= 28, 35, 42, 49). These show that the penta‐ploid is the most common race and that the distribution of the races as a whole is a reflection of varying degrees of adaptability to moisture content of the soil.Chromosome studies at meiosis and mitosis show that the tetraploid is an allopolyploids and that the hexaploid is derived from it. The penta‐ploid appears to be derived from a hybrid of H. lanatus (2n=14) and H. mollis (2n= 28).The hybrid nature of the penta‐ploid is confirmed by the discovery of natural triploid hybrids (2n= 21) from which it is presumed to have been derived by backcrossing to the tetraploid parent.With the exception of the tetraploid, the races of H. mollis reproduce almost exclusively by vegetative means. The tetraploid is fertile but is also likely to reproduce mainly by rhizomes.The success of the penta‐ploid is attributed to its hybrid vigour in both growth and adaptability to soil moisture. In addition its spread is favoured by the fact that its tetraploid parent does not offer much seed competition in the colonization of new areas. There is no competition from the H. lanatus parent, which has different ecological requirements.It is considered feasible that the vigorous penta‐ploid could eventually supersede the other races of H. mollis.
THE STUDY OF POLLEN GRAIN SURFACES IN THE ELECTRON MICROSCOPE
Authors: BRADLEY D. E. 
Published: May 2006

summary1. The application of the electron microscope to the study of pollen grains is discussed.2. Two carbon replica methods suitable for the study of pollen grain surfaces are briefly described.3. Examples are given of the surfaces of various pollen specimens, and a distinction between the submicroscopic structures of Corylus and Myrica is reported. Structures within the furrows of some grains are described.The high resolving power of the electron microscope is of considerable value in the study of pollen, and the sub‐microscopic structure revealed is of interest in problems of identification and of pollen morphology. However, the difficulties encountered in the preparation of pollen specimens for the electron microscope have limited the amount of research carried out in this field.Pollen grains cannot be examined directly in the instrument because of their size and consequent density to electrons, and even in the case of acetolysed grains the remaining wall is still far too thick to allow the passage of electrons through it. It is therefore necessary to employ either thin sections or surface replicas. The first method has been used extensively by Mühlethaler (1953), Afzelius, Erdtman and Sjöstrand (1954) and Afzelius (1950) in studies of pollen and spore walls. Surface replicas have been employed by Mühlethaler (1955) who used the carbon replica method (Bradley, 1954a). The present author has also made some preliminary studies using this technique (Bradley, 1956). This paper is concerned with the potentialities of the carbon replica in the study of pollen grain surfaces.
ON THE STRATIGRAPHY AND PALAEOBOTANY OF A LATE‐PLEISTOCENE ORGANIC DEPOSIT AT CHELFORD, CHESHIRE
Authors: SIMPSON I. M. , WEST R. G. 
Published: May 2006

summaryThe stratigraphy of the Pleistocene deposits in the area of Chelford is described.The palaeobotany of a layer of organic mud within the Middle Sands of the Pleistocene sequence is described, and it is shown that the organic mud was deposited during a cool period in which a Betula‐Pinus‐Picea forest was the local dominant vegetation. The climatic indications given by the flora and vegetation are discussed.The organic mud is tentatively correlated with an interstadial period early in the Last Glaciation; the implications of this correlation are briefly mentioned.
TWO LACUSTRINE DEPOSITS IN THE SOUTH OF THE ENGLISH LAKE DISTRICT
Authors: SMITH A. G. 
Published: May 2006

SummaryIt is shown that the lowermost deposits at Helton Tarn and at the former lake near Witherslack Hall, Westmorland, date from Late‐glacial times and that zones I, II and III correspond roughly to layers of laminated clay, clay mud, and clay, respectively. There is little evidence for solifluction in zone III. Pollen analysis reveals a Late‐glacial flora comparable with floras of similar date which have already been described. A minor oscillation, in which herb pollen becomes predominant over tree and shrub pollen, occurs at both sites during zone II. At Helton Tarn some of the pollen types characteristic of the Late‐glacial period occur sporadically until Boreal and Atlantic time; at both sites pollen of those weed and ruderal types which are plentiful in the early deposits constantly recurs throughout Post‐glacial time.Stratigraphical and pollen analytical evidence suggests that at the maximum of the early Post‐glacial marine transgression, the sea overflowed a rock bar that is now at about + 5 m. O.D. into the Helton Tarn basin and laid down a layer of clay during the earliest part of Atlantic time.In contrast to the findings of Walker (1955a), at the sites investigated, Finns appears to have been relatively successful in Boreal time and Tilia pollen, although not appearing until early Atlantic time, is present in quantity throughout most of post‐Boreal time. The relatively high proportion of Tilia pollen suggests that the lime was growing as far north as southern Westmorland in post‐Boreal time.At the opening of the Sub‐boreal period, at the first decline of Ulmus pollen, the presence of small amounts of Plantago lanceolata pollen is taken to indicate the first agricultural activity in the region.
THE ECOLOGY OF FUNGI IN CALLUNA‐HEATHLAND SOILS
Authors: SEWELL GEOFFREY W. F. 
Published: May 2006

SummaryThe fungi occurring in some Calluna‐heathland soils in England and Wales were studied by the soil plate method. A small proportion of the fungi isolated were of constant occurrence and are considered to be representative members of the heath land fungus flora as demonstrated by the soil plate method. The distribution of fungi in area could be related to the known habitat characteristics in a few instances: these relationships were obtained mainly with fungi which tended to dominate the immediate subsurface populations.The numbers of species decreased with depth and only five species were at their most frequent occurrence in horizons below the surface: four of these were species of high constancy of occurrence in these soils. Evidence suggested that the presence of illuviated horizons in the soil profile restricted the vertical distribution of sporing species. The deepest soil levels were colonized largely by a miscellany of sterile mycelia.
STUDIES ON THE GROWTH OF EXCISED ROOTS
Authors: CHARLES H. P. 
Published: May 2006

SummaryA study has been made of the effects of 2‐naphthoxyacetic acid (2‐NOA) on excised roots from various strains of groundsel. The roots were grown in medium containing lysine and 2‐NOA for one passage and were then subcultured into arginine medium for their second passage.‘Directly’ the effect of 2‐NOA was to increase, though to different levels, the growth of the roots of all strains.‘Indirectly’ and at a concentration appropriate to each strain, it increased the growth of all four strains up to the same high level. The hypothesis is advanced that a major factor responsible for the different growth rates of the roots of the different strains is their content of a natural growth substance whose physiological properties are simulated by 2‐NOA.
STUDIES ON THE GROWTH OF EXCISED ROOTS
Authors: SHEAT D. E. G. , FLETCHER B. H. , STREET H. E. 
Published: May 2006

SummaryThe composition of the inorganic fraction of White's medium has been modified to permit studies in nitrogen nutrition. A preparation of ferric sodium ethylenediamine tetra‐acetate is described which enables an addition of 1 p.p.m. iron to meet the iron requirement of exised tomato roots in culture media whose pH is below 7.5.The content of calcium and magnesium in the medium has been reduced to one‐tenth the standard concentration in order to prevent precipitation at pH values above 6.0, particularly when using enhanced phosphate concentrations.Techniques whereby the pH of root culture medium can be adjusted aseptically or stabilized by the addition of soluble phosphates or of sparingly soluble salts of calcium (phosphate, carbonate) are described and evaluated.These techniques have made possible a high level of growth of excised tomato roots receiving ammonium as their sole source of nitrogen. The ability of the roots to grow with nitrite as their sole nitrogen source has also been demonstrated. In contrast, hydroxylamine, even at low concentrations, inhibited the extension growth which otherwise occurs on absence of external nitrogen and caused death of the root apices.pH‐growth response curves with ammonium and with nitrate as nitrogen sources indicate pH 4.7–4.9 as optimum for growth with nitrate nitrogen and pH 7.0–7.2 as optimum for growth with ammonium nitrogen. Less complete data indicates pH 5.0–6.0 as the optimum region for growth with nitrite.From studies of the pH drifts occurring as a result of root growth in media containing various ammonium: nitrate ratios and from direct determinations of nitrate and ammonium uptake at high and low pH, it is concluded that the differing pH optima for these two nitrogen sources are not explicable in terms of the direct effects of pH upon the uptake of these ions.
STUDIES ON THE GROWTH OF EXCISED ROOTS
Authors: HANNAY J. W. , FLETCHER B. L. , STREET H. E. 
Published: May 2006

SummaryExcised tomato roots supplied their nitrogen as nitrate in media of pH 4–5 or pH 7 have an essential requirement for molybdenum. Their growth is markedly stimulated and their continued culture made possible by the addition of 0.000005 p.p.m. Mo. The minimum addition which fully satisfies the molybdenum requirement is 0.001 p.p.m. The depression of growth resulting from a deficiency of molybdenum is not due to the toxicity of accumulating nitrate.Excised roots supplied their nitrogen as nitrite, ammonium, urea, casein hydrolysate or as a mixture of L(+)— arginine and glycine are capable of growth in molybdenum‐omitted medium. Their growth is stimulated by addition of molybdenum and a similar addition is required for optimum growth whether nitrogen is supplied as nitrate or as ammonium.The tolerance of excised tomato roots to excess manganese at pH 7.0 is greater in ammonium than in nitrate media. The optimum manganese addition is increased by supraoptimal concentrations of ammonium. Optimum growth is only achieved when the medium has a satisfactory magnesium: manganese ratio. The deleterious effects of excess manganese can be counteracted by increasing the concentration of magnesium. At low manganese concentration, growth is depressed by enhancing the magnesium concentration.Using a medium buffered with calcium carbonate (pH 7) and with a manganese addition of 0.01 p.p.m. the continuous culture of excised tomato roots supplied their nitrogen solely as ammonium has been achieved. No improvement of the very poor growth occurring in ammonium media at pH 4–5 has been achieved by altering the absolute and relative concentrations of a number of macronutrient elements.
POPULATION DIFFERENTIATION IN AGROSTIS TENUIS SIBTH
Authors: BRADSHAW A. D. 
Published: May 2006

SummaryIn order to investigate the pattern of population differentiation in Agrostis tennis, sixty tillers were collected from each of thirty‐three areas mainly in central Wales. These were grown under garden conditions in Aberystwyth. In a subsequent experiment five of these areas were sampled again by tillers, and at the same time sampled by seed. These samples were grown under garden conditions in Bangor.Numerous differences between these population samples were recorded. The main conclusions are as follows:(i) The environment is the dominating factor in determining population differentiation.(ii) Although the distribution is continuous, distances of about 50 m or less are sufficient to effectively isolate populations from one another.(iii) Thus the species is able to evolve under the influence of natural selection in response to very local variations in environment.(iv) Since the environment is a graded patchwork of different conditions, the pattern of differentiation is similar.(v) It is, therefore, not possible to classify effectively such interspecific variation.(vi) It is likely that this situation is to be found in most other out breeding continuously distributed plant species occupying a wide range of habitats.
EFFECT OF VESIGULAR‐ARBUSCULAR MYCORRHIZAS ON GROWTH OF GRISELINIA LITTORALIS (CORNACEAE)
Authors: BAYLIS G. T. S. 
Published: May 2006

SummaryThe endophyte of Griselinia littoralis is a vesicular‐arbuscular Phycomycete which could not be induced to make more than transient growth into agar, but which survived in soil kept moist for 26 months.In two consecutive experiments using sterilized soil in which ectotrophic mycorrhizas were necessary for sustained growth of Pinus radiata the endotrophic mycorrhizas of Griselinia littoralis proved necessary for sustained growth of that species. Under the same conditions seedlings of a non‐mycotrophic tree, Myrsine australis, grew steadily.The technique used to establish mycorrhizas upon Griselinia did not stimulate its growth when mycorrhizas were not formed. It produced no symbiotic infection in Pinus and only traces of it in Myrsine, and it depressed the growth of both these species.In both Pinus and Griselinia percentage composition of mycorrhizal plants was consistently higher in phosphorus and lower in nitrogen than that of non‐mycorrhizal plants. Enhanced phosphorus uptake thus appears to have been the main favourable effect of both types of mycorrhiza.
POLLEN DIAGRAMS FROM SOUTHERN ENGLAND: WAREHAM, DORSET AND NURSLING, HAMPSHIRE
Authors: SEAGRIEF S. C. 
Published: May 2006

SummaryPollen analytic investigations made at two sites in southern England, Wareham, Dorset and Nursling, Southampton, show in each instance valley fen deposits extending over a considerable part of Post‐glacial time. The general trends of the tree‐pollen curves conform closely to the pattern established by Godwin (1940 and later papers). At Nursling the earliest deposits were formed in zone III and exhibit a typical range of Late‐glacial pollen types.Lists of macroscopic remains are given for each site. Remains of Pinus sylvestris in zones III, IV and V establish the early presence of this tree in southern England and Fagus sylvatica also appears to have been present from early Atlantic time. There is some evidence for the presence of open heath and grassland in Wareham from the same period onwards.