bluuebunny/crossref_metadata_2025_split huggingface dataset:
Reduced fecundity and offspring performance in small populations of the declining grassland plantsPrimula verisandGentiana lutea
Authors: Kéry Marc , Matthies Diethart , Spillmann Hans‐Heinrich 
Published: March 2003

Summary1 We studied reproduction and offspring performance in relation to population size in the declining self‐incompatible perennialsPrimula verisandGentiana lutea. In both species, reproduction was strongly reduced in small populations, where plants produced fewer seeds per fruit and per plant. Total seed mass per plant was higher in large populations, but individual seeds were smaller, indicating a trade‐off between seed number and size. Reproduction was depressed most strongly in populations consisting of less thanc.200 (P. veris) andc.500 plants (G. lutea), respectively.2 The inclusion of plant size (an integrated measure of habitat quality) in the statistical models did not change the relationships between fecundity and population size. Pollen limitation or inbreeding depression in small populations are therefore more likely explanations for these patterns than is habitat quality.3 Germination rate and survival of seedlings in a common environment was not related to population size in either species, althoughP. verisdeveloped into larger rosettes when seeds were derived from large populations. This suggests that inbreeding depression occurs in small populations ofP. veris.4 In a factorial fertilizer‐by‐competition experiment withP. veris, offspring from larger populations grew significantly larger and responded more strongly to fertilizer. For this declining species genetic deterioration as a result of habitat fragmentation may therefore aggravate the effects of environmental changes such as habitat eutrophication.5 Our results suggest that small populations may face an increased short‐term risk of extinction because of reduced reproduction, and an increased long‐term risk because they are less able to respond to environmental changes.
Long‐term change and spatial pattern in a late‐successional hemlock–northern hardwood forest
Authors: Woods Kerry D. 
Published: March 2003

Summary 1 Tree populations were monitored for six decades on a grid of 140 permanent plots in old‐growth mesic (hemlock‐northern hardwood) forests in northern Michigan, USA. Multiple remeasurements allow assessment of stability of late‐successional forests and analysis of spatial patterns and environmental linkages. 2 This forest is not compositionally stable. Betula alleghaniensis has declined with little regeneration, suggesting dependence on episodic canopy disruption for persistence. Tsuga canadensis and Fagus grandifolia have increased in dominance in all size classes independently of major disturbances. Acer saccharum populations have remained little changed overall. Dynamics appear to be successional in nature, even though there has been no major disturbance for at least 400 years. Different areas in the stand may have experienced different histories. 3 Fagus grandifolia has invaded the stand recently through range expansion, and has come to dominate regeneration in some parts of the stand. 4 Canonical correspondence analysis suggests that soil texture, chemistry, and drainage influence successional dynamics, producing strong spatial pattern. Fagus grandifolia has invaded only on relatively fine‐textured soils with impeded drainage. 5 Trends suggest that Fagus, Tsuga, and perhaps Acer saccharum would, in different parts of the stand, achieve near‐total dominance in the absence of large‐scale disturbance, but only after elapsed time of a millennium or more. Estimated return times for major disturbance in this region are of similar magnitude.
Unexpected density‐dependent effects of herbivory in a wild population of the annual Collinsia torreyi
Authors: Parmesan Camille 
Published: March 2003

Summary 1 Herbivory is known to affect plant fitness, but has rarely been studied under realistic conditions, i.e. by manipulation of real herbivores in a wild plant population. Furthermore, its interaction with competition, another factor known to affect plant physiology and reproduction, has usually been neglected. 2 Interactions among plant density, insect herbivore damage and plant fitness components (survival and lifetime fecundity) were investigated by both observation and experiment in a population of a native montane annual, Collinsia torreyi, and its primary insect herbivore, the butterfly Euphydryas editha. Larvae were manipulated to inflict predetermined levels of experimental damage. 3 Increases in either plant density or herbivory generally had negative effects on fitness. Loss of only 5% of seedling leaf area significantly reduced adult lifetime fecundity. 4 Herbivory reduced fitness at low, but not at high, plant density. This form of interaction between effects of competition and herbivory is theoretically unexpected and opposite in direction to interactions found in other published studies. Low resource availability may be an important factor. 5 Where such an interaction occurs, it would cause the selective effects of herbivores to be density‐dependent, i.e. when plants are crowded, the absence of selection would oppose any evolutionary increase in costly defences.
Influence of pressurized ventilation on performance of an emergent macrophyte (Phragmites australis)
Authors: Vretare Viveka , Weisner Stefan E. B. 
Published: March 2003

Summary 1 Pressurized ventilation, which increases gas exchange between aerial and submerged plant parts, has been found in various emergent macrophyte species. We investigated the potential for this mechanism to affect growth, morphology and biomass allocation in Phragmites australis in glasshouse experiments. 2 Inhibition of pressurized ventilation by perforation of stems above the water surface resulted in decreased oxygen concentrations in stem bases and rhizomes. Perforation caused little mechanical damage. 3 Allometric methods were used to evaluate treatment effects on biomass allocation and morphology. 4 Inhibition of pressurized ventilation resulted in decreased allocation to below‐ground weight and decreased rhizome penetration into the substrate in two of three experiments. Treatment also decreased growth rate, rhizome length and number of rhizomes when substrate had a high organic content. In the third experiment, growth clearly decreased in deep water, although inhibition of pressurized ventilation did not affect growth, biomass allocation or morphology at either of the water depths tested. 5 Decreased allocation to below‐ground parts and decreased rhizome lengths may be adaptations to allow the oxygen concentration in roots and rhizomes to be maintained above a critical level when the oxygen supply is low. 6 Pressurized ventilation may improve the performance of P. australis but only under certain conditions (e.g. not when growth rate is low or the substrate has a high redox potential).
Fruit dispersal and seed banks inAtriplex sagittata: the role of heterocarpy
Authors: Mandák Bohumil , Pyšek Petr 
Published: March 2003

SummaryAtriplex sagittata, an arly succesional, annual species of disturbed habitats in Central Europe, produces three types of fruits. We studied the differences in dispersal between the fruit types in order to investigate their ecological roles.The typical positive relationship between dispersal ability and germinability is not found in this species. Type A (ebracteate) fruits produced deeply dormant seeds and had the lowest dispersal potential, but of the two fruits with bracts, type B, with dormant seeds, was better dispersed by both water and wind than type C, which produces non‐dormant seeds.Wind, temperature and precipitation have significant effects on fruit release but their effects differ between fruit types. The release of fruit types with bracts was positively correlated with wind whereas all fruit types tended to be negatively correlated with precipitation and temperature range.Type C fruit, which contains non‐dormant seed, are absent from the soil in summer and have a Type II transient seed bank. Type A and B fruits, containing dormant seeds, form a persistent seed bank.Heterocarpy, where fruit types show distinct ecological behaviour, enables colonizing species such asA. sagittatato survive both major disturbance (by ensuring that some seeds persist) and unfavourable conditions (by spreading germination over a long period).InA. sagittata, seed dynamics can be explained by the germination behaviour of seeds produced by the three types of fruit. All fruit types mature in autumn, but few of Type A fall from the mother plant until spring, when germination is probably inhibited because of insufficient stratification. Type C fruit, however, show peak dispersal in winter and the majority of these non‐dormant seeds are able to germinate as soon as conditions become more suitable.
Calcium and pH in north and central Swedish mire waters
Authors: Sjörs H. , Gunnarsson U. 
Published: March 2003

Summary

We present data on calcium concentrations and pH in mire waters collected from different mire types in central and northern Sweden, compiled from published literature or calculated from field determinations of electrical conductivity and pH.
Measurements of electrical conductivity (after subtracting that of H+ ions) were used to calculate the most probable Ca concentrations, but only when pH was 4.7 or higher. At lower pH the possible errors become too large.
The data support a continuous gradient in water chemistry, but with considerable overlap, from mineral‐poor ombrotrophic bogs and minerotrophic extremely poor fens, to moderately poor fens, intermediate fens, moderately rich fens and finally to extremely rich fens, rather than a discrete division. However, for hydrological reasons, we wish to retain the separation of ombrotrophy (bog) from minerotrophy (fen).
The frequency histogram of pH values from central and northern Sweden shows a bimodal tendency, although a considerable number of mires still occur close to the minimum (pH 5.3). Over‐sampling in species‐rich areas could have contributed to the depth of this apparent minimum, but not to its position along the pH scale.
Changes in calcium concentrations in mire waters during the last 50 years are discussed and related to changes in pH and conductivity.
Year‐to‐year variation in plant competition in a mountain grassland
Authors: Herben Tomáš , Krahulec František , Hadincová Věra , Pecháčková Sylvie , Wildová Radka 
Published: March 2003

Summary

We used a series of removal experiments to examine how species response to competition and climatic differences varied in three different years. We tested the interaction between removal of the dominant grass species, Festuca rubra, and year‐to‐year environmental variation in a mown mountain grassland.
In each year, we quantified shoot frequency and above‐ground biomass of all remaining plant species. Above‐ground responses were tested both by analysis of covariance and by redundancy analysis with randomization tests of changes in total species composition.
Analysis of above‐ground biomass data showed that other species compensated for the removal of F. rubra biomass within 2 years and that the response in total biomass of the community did not differ among years in which the experiment was started.
Multivariate tests showed that species composition changed as a result of the removal; grass biomass and frequency increased more than that of dicotyledons. However, response of species composition to removal of F. rubra was significantly different between onset years. Specific conditions in individual years thus affect the competitive ability of individual species in a non‐additive way.
Our results indicate that the year‐to‐year variation at the site has the potential to affect species coexistence and richness. As a consequence, year‐to‐year variation of climatic parameters may be an important driving factor in community dynamics and should be taken into account in studies of ecosystem response to climate.
Do ants feed plants? A 15N labelling study of nitrogen fluxes from ants to plants in the mutualism of Pheidole and Piper
Authors: Fischer Renate C. , Wanek Wolfgang , Richter Andreas , Mayer Veronika 
Published: March 2003

Summary

Nutrient fluxes play a significant role in the interaction of myrmecophytic plants and their symbiotic ants. There is a clear flux from plants to ants via nectar or food bodies but nutrient fluxes from ants to plants are less obvious.
We report on a nitrogen flux from ants to plants in the association between Pheidole bicornis (Formicidae‐Myrmicinae) and two myrmecophytic Piper species (P. fimbriulatum and P. obliquum, Piperaceae). Pulse experiments were performed by feeding ants with 15N‐labelled glycine supplied in sucrose solution. Workers passed ingested label on to other ants and the brood by trophallaxis.
The distribution of label within the colony showed highest incorporation rates in larvae and in the working caste, while the reproductive caste received only a small amount of the 15N‐labelled food.
Nutrient transfer from ants to plants occurred remarkably fast. Within 6 days, up to 25% of the nitrogen ingested by the ants was incorporated by the plants.
However, ant distribution within P. fimbriulatum plants did not correlate with the intra‐plant uptake pattern of 15N, and ant‐mediated nitrogen uptake by myrmecophytic P. fimbriulatum accounted for less than 1% of the plants’ above‐ground nitrogen demand.
Public health in the undergraduate medical curriculum – can we achieve integration?
Authors: Stone David H. 
Published: March 2003

AbstractPublic health is widely regarded by medical students as peripheral or even irrelevant to the acquisition of clinical knowledge and skills. This paper attempts to set out some of the reasons for this, to encourage innovative approaches to integrating public health with clinical teaching and to offer a theoretical framework of integrated public health education for curriculum development and evaluation. The points of convergence between public health and clinical practice should not be regarded as self‐evident. A practical demonstration of the application of public health principles to clinical problem solving may be the most effective means of overcoming resistance. Almost anywhere that clinical services are provided is suitable for this purpose. Community clinics, health centres or general practices have obvious appeal but acute hospitals have important advantages arising from students’ preoccupation with clinical medicine. The main aim of integrated public health teaching is to facilitate the students’ acquisition of knowledge, skills and attitudes that promote the effective application of public health approaches to clinical practice. The interrelationships between clinical practice and public health may be represented in the form of a grid. The vertical headings are the clinical skills that relate to the different stages of the natural history of disease – from the pre‐disease state through diagnosis, treatment and follow up. The horizontal headings describe four key public health dimensions: epidemiology, behaviour/lifestyle, environment and health policy. The text in the boxes suggests appropriate topics for discussion. The grid is also potentially useful for course documentation and content evaluation.
Do we face a fourth paradigm shift in medicine – algorithms in education?
Authors: Eitel Florian , Kanz Karl‐Georg , Hortig Dipl. ‐Ing Elzbieta , MA Arthur Tesche 
Published: March 2003

AbstractMedicine has evolved toward rationalization since the Enlightenment, favouring quantitative measures. Now, a paradigm shift toward control through formalization can be observed in health care whose structures and processes are subjected to increasing standardization. However, educational reforms and curricula do not yet adequately respond to this shift. The aim of this article is to describe innovative approaches in medical education for adapting to these changes. The study design is a descriptive case report relying on a literature review and on a reform project’s evaluation. Concept mapping is used to graphically represent relationships among concepts, i.e. defined terms from educational literature. Definitions of ‘concept map’, ‘guideline’ and ‘algorithm’ are presented. A prototypical algorithm for organizational decision making in the project’s instructional design is shown. Evaluation results of intrinsic learning motivation are demonstrated: intrinsic learning motivation depends upon students’ perception of their competence exhibiting path coefficients varying from 0.42 to 0.51. Perception of competence varies with the type of learning environment. An innovative educational format, called ‘evidence‐based learning (EBL)’ is deduced from these findings and described here. Effects of formalization consist of structuring decision making about implementation of different learning environments or about minimizing variance in teaching or learning. Unintended effects of formalization such as implementation problems and bureaucracy are discussed. Formalized tools for designing medical education are available. Specific instructional designs influence students’ learning motivation. Concept maps are suitable for controlling educational quality, thus enabling the paradigm shift in medical education.
Meaning and measurement: an inclusive model of evidence in health care
Authors: Upshur Ross E.G. , VanDenKerkhof Elizabeth G. , Goel Vivek 
Published: March 2003

AbstractEvidence‐based approaches are assuming prominence in many health‐care fields. The core ideas of evidence‐based health care derive from clinical epidemiology and general internal medicine. The concept of evidence has yet to be analysed systematically; what counts as evidence may vary across disciplines. Furthermore, the contribution of the social sciences, particularly qualitative methodology, has received scant attention. This paper outlines a model of evidence that describes four distinct but related types of evidence: qualitative‐personal; qualitative‐general; quantitative‐general and quantitative‐personal. The rationale for these distinctions and the implications of these for a theory of evidence are discussed.
A critique of hypertension treatment trials and of their evaluation
Authors: Robertson John I.S. 
Published: March 2003

AbstractProgressive improvements in antihypertensive drug therapy over the past four decades have provided clear benefits in limiting cardiovascular complications. Unfortunately, and largely inexplicably, the inclusion in meta‐analyses of defective trials plus the employment of inappropriate diagnostic criteria for adverse coronary events have led to spurious, exaggerated claims for the advantages of such treatment. The consequence has been a devaluation of the very real worth of prophylactic drug therapy for hypertension.
Evidence‐based medicine, guidelines, personality types, relatives and absolutes
Authors: Welsby Philip D. 
Published: March 2003

AbstractThere is an epidemic of guidelines but very little evidence‐based information has been assembled to tell us exactly how guidelines are best implemented. Guidelines, although very valuable, are essentially a reductionistic attempt to simplify the complexities of medicine. Clinicians may appreciate that each guideline should be prefaced by a statement that ‘what follows may not be applicable to all patients’ but there seems little doubt that guideline adherence will be used to assess quality of care by those unfamiliar with the complexities.
Beyond evidence‐based medicine: bridge‐building a medicine of meaning
Authors: Buetow S. 
Published: March 2003

AbstractContesting that a debate on evidence‐based health care has taken place, this article charts three paths to the future: continuing avoidance of debate by proponents of evidence‐based medicine (EBM); conflict, which the EBM movement courts and critics have espoused, and dialogue. The last portal allows for integration, which would end the disagreement between EBM and its critics and make a debate unnecessary. In search of integration, I sketch a bridge whose construction requires not compromise but a win– win approach. The bridge is a medicine of meaning (MOM). Consolidating multiple pillars of evidence to unify questions that are not necessarily the same for protagonists and critics of EBM, a MOM contends that the purpose or meaning of
medicine is always healing and helping, and each party finds meaning in medicine by contributing to this common purpose in its own distinctive way.
Developing a measure of patient access to primary care: the access response index (AROS)
Authors: Elwyn Glyn , Jones Wendy , Rhydderch Melody , Edwards Peter 
Published: March 2003

AbstractAccess to appointments in primary care is not routinely measured, and there is no one standardized method for doing so. Any measurement tool has to take account of the dynamic status of appointment availability and the definitional problems of appointment types. The aim of this study was to develop and trial a method for measuring access that is valid, reliable, quick and provides a daily longitudinal record of access on an organizational basis (not for individual clinicians). Using the results of a literature review and following discussions with clinicians and managers a tool was designed following agreed specifications. After initial adjustments of the tool a feasibility study tested the acceptability of a data collection exercise on 11 practices of varying types, over a 4‐ to 8‐week period. The development phase led to the design of a tool named the access response index (AROS). The method was well received in the practices, with a low incidence of missed days and only one practice failing to return data. The index measures the number of days’ wait to the next available appointment with any general practitioner. The inclusion in the score of urgent appointments was abandoned due to definitional problems. A 5‐day moving average was chosen to represent the data in graph form to demonstrate overall trends. AROS is a useful tool usable in any practice, and our feasibility study points to it being widely acceptable in the field. Data are represented in clear graphical daily format, either just for one practice or as an anonymous composite graph with other practices in the locality.
Effects of tributyltin and hypoxia on the progression of Perkinsus marinus infections and host defence mechanisms in oyster, Crassostrea virginica (Gmelin)
Authors: Anderson R. S. , Brubacher L. L. , Calvo L. Ragone , Unger M. A. , Burreson E. M. 
Published: March 2003

AbstractOysters, Crassostrea virginica (Gmelin), naturally infected by the protozoan parasite Perkinsus marinus in the field were exposed for 6 weeks to tributyltin (TBT), hypoxia, or to both stressors simultaneously. The TBT‐exposed oysters continuously bioaccumulated TBT, reaching about 4 mg kg−−1 dry weight by 6 weeks; hypoxic oysters were exposed to water containing an average dissolved oxygen level of about 3 mg L−−1. Untreated control oysters suffered about 30% cumulative mortality by 6 weeks as a result of the progression of their P. marinus infections. The TBT treatment alone produced no additional mortality; however, cumulative mortality in hypoxic oysters was elevated. Mortality among oysters receiving both TBT and hypoxia significantly exceeded that caused by either stressor alone, suggesting a synergistic effect. In an attempt to identify immunotoxicological mechanisms underlying stress‐related augmentation of P. marinus infections, defence‐related immune functions were measured at 3 and 6 weeks in control and treated oysters. In general, the total number of haemocytes increased as the infections progressed, and the TBT and hypoxic treatments also caused significant additional increments in some samples. However, oxygen‐dependent (reactive oxygen species) and oxygen‐independent (lysozyme) antimicrobial host defence mechanisms appeared to be largely unaffected by TBT and/or hypoxia. This may be explained by the death of those oysters with marked immunological lesions prior to sampling or by the actual lack of treatment effects.