bluuebunny/crossref_metadata_2025_split huggingface dataset:
Species richness–standing crop relationship in stream bryophyte communities: patterns across multiple scales
Authors: Virtanen Risto , Muotka Timo , Saksa Marita 
Published: March 2003

Summary

We tested for a unimodal (‘hump‐backed’) relationship between species richness and standing crop at various spatial scales in stream bryophyte communities. Bryophyte species and their biomasses were determined from 20 to 25 quadrats in eight river and six stream sites in northern Finland.
Regression analyses revealed a quadratic relationship between richness and biomass in only two of the river sites and a positive correlation in one other. A quadratic relationship was detected in three stream sites and richness increased linearly with biomass in another.
We also tested for the hump‐shaped pattern across individual stream boulders, representing an elevational gradient from continuously submerged to permanently dry conditions, with an intermediate zone with fluctuating water level.
Species richness‐standing crop relationship conformed to the hump‐backed model only when samples from all three microhabitats were included in the analysis. A significant positive correlation occurred in the exposed low biomass end of the gradient which is characterized by semi‐aquatic species, whereas the relationship tended to be negative in permanently submerged areas with high biomass of large canopy‐forming species. Quadrats close to the water level had intermediate standing crop and highest species richness.
Species dominant at either end of the gradient appeared unable to monopolize space in the intermediate zone where disturbances (e.g. scouring by ice) detach mosses from the substratum, creating vacant gaps for colonization. The unimodal relationship between richness and biomass is likely to occur only in streams that contain large boulders protruding above the water line, thus providing scope for community diversification along very short vertical distances.
Consequences of plant population size and density for plant–pollinator interactions and plant performance
Authors: Mustajärvi Kaisa , Siikamäki Pirkko , Rytkönen Saara , Lammi Antti 
Published: March 2003

Summary Habitat fragmentation and the resulting decline in the local abundance of plant species can affect biological interactions. We examined the effects of abundance on plant–pollinator interactions by observing the pollinator service and subsequent reproductive output of a mostly outbreeding, but self‐compatible, plant,Lychnis viscaria, in experimental populations of different sizes (number of individuals) and densities (distance between individuals). Bumblebees, the main pollinators ofL. viscaria,preferred larger populations, but visitation rates were higher in sparser populations. Pollinators were attracted to the larger inflorescences in sparse populations, which were also more visible due to their larger area for a given size. Bumblebees probed more flowers within plants in sparse populations, probably due to the larger inflorescences and longer flight distances between individuals. Subsequent reproductive success (capsule production) was higher in sparse populations, due to differences in pollination success and resource competition, and their interaction. In self‐compatible species, such asL. viscaria, reproductive success may be determined more by resource availability, whereas self‐incompatible plants may be more sensitive to changes in pollinator abundance. We conclude that plant–pollinator interactions are sensitive to changes in both the size and spatial arrangement of plant populations, which can affect their demography and genetics. In this study, species density had a greater effect than size and the unexpectedly beneficial effects of low density may be due to greater resource availability.
Crown development in tropical rain forest trees: patterns with tree height and light availability
Authors: Sterck Frank J. , Bongers Frans 
Published: March 2003

Summary

Monitoring of two canopy species Dicorynia guianensis and Vouacapoua americana (Caesalpiniaceae) in a tropical rain forest in French Guiana was used to investigate vegetative crown development at five organizational levels: leaf, metamer, extension unit, sympodial unit and whole crown. The effects of light availability and tree height on different traits were evaluated in trees < 25 m in height and compared with taller individuals (25–37 m). Path‐analysis is used to illustrate the consequences of trait changes at multiple levels of organization for the whole crown level.
Tree height and canopy openness influenced crown development at each organizational level. Crowns in higher light levels had lower specific leaf area, greater leaf spacing, greater extension of all branches, and greater extension of the leader shoot. With increasing tree height, crowns had a lower specific leaf area, greater leaf area index and greater relative crown depth.
Vouacapoua showed some responses to light not seen in Dicorynia. In particular, Vouacapoua increased meristem activity with light, but the lack of response in Dicorynia may be due to moderate light levels rather than inability to respond.
Low leaf‐display costs at low light availability may enable trees to survive light suppression.
Light availability cannot explain trait changes with tree height. Alternative explanations for trait changes with tree height are discussed.
Several of the relationships between plant traits and tree height or canopy openness became non‐linear when taller trees (25–37 m) were included. In these taller trees, vegetative growth was reduced at all organizational levels, particularly in Vouacapoua, which does not grow as tall as Dicorynia.
Qualitatively, plant responses to light did not differ between trees of different height, and were similar to seedling and sapling data in the literature. Responses were, however, quantitatively different, suggesting that small saplings cannot serve as model organisms for crown development in taller trees.
Relationship between vegetation and soil seed banks in an arctic coastal marsh
Authors: Chang E. R. , Jefferies R. L. , Carleton T. J. 
Published: March 2003

SummaryThe effects of habitat degradation on the soil seed bank at La Pérouse Bay, Manitoba are described. Foraging by lesser snow geese leads to loss of vegetation, coupled with changes in soil abiotic conditions and an increase in salinity.The density of seeds and the relative abundance in the seed bank of species characteristic of undisturbed sites decrease following degradation, while the relative abundance of invasive species increases. Vegetation loss had the greatest impact on seed banks of stress‐tolerant species and the least impact on species with many widely dispersed seeds.The above‐ground vegetation and below‐ground seed bank were less similar in undamaged plots than in disturbed plots. In spite of the low degree of similarity, redundancy analysis of the data indicated that approximately half of the variation in the soil seed bank could be explained by the vegetation data and vice versa.More recently degraded soils had richer soil seed banks than those from older disturbances. Site‐specific factors not only influenced the species present but also the time lag between loss of vegetation and loss of the seed bank. Seed banks in these impacted and fragmented sites do not recover quickly.Seed banks in sandy beach‐ridges were less affected by degradation due to the greater proportion of ruderals present in the original vegetation and the absence of the high soil salinities that are characteristic of degraded salt‐marsh soils.
Resprouting and growth dynamics after fire of the clonal shrub Andira legalis (Leguminosae) in a sandy coastal plain in south‐eastern Brazil
Authors: Cirne Paulo , Scarano Fabio R. 
Published: March 2003

Summary

Survival, resprouting and growth dynamics of the clonal shrub Andira legalis were studied for 2 years after fire, on a sandy spit on the coastal plain of Brazil. We examined the importance of resprouting for post‐fire persistence, the relationship between resprouting patterns and injury suffered and size of individuals, and whether ramet growth was determined by competition and self‐thinning.
Post‐fire resprouting was responsible for production of new ramets and led to an increase in the mean number of ramets per A. legalis individual.
There was a negative association between resprouting from overground vs. underground. Highly injured individuals showed a significant tendency to sprout new ramets from underground organs whereas less damaged plants produced new branches and leaves from stem buds. Ramet production was related to an individual’s prefire size (basal area), but to a lesser extent than to injury.
Immediately after fire, the G(t,x) function (mean of absolute growth rates of shoots of size x at time t) was size‐independent, suggesting an absence of competition. G(t,x) then became size‐dependent, while D(t,x) (variance of absolute growth rates of shoots of size x at time t) remained size‐independent, indicating that any competition between ramets was symmetric.
Size‐dependent mortality and a negative linear relationship between mean ramet size and density indicated self‐thinning. However, the low ramet mortality (7.7%) and the absence of size hierarchies (coefficients of variation remained constant) suggest that competition and self‐thinning were not intense.
Clonal variation in morphological and physiological responses to irradiance and photoperiod for the aquatic angiosperm Potamogeton pectinatus
Authors: Pilon Jörn , Santamaría Luis 
Published: March 2003

Summary

Widely distributed plants are exposed to contrasting gradients in irradiance and photoperiod across latitude. We investigated the relative contribution of local specialization and phenotypic plasticity to variation in plant growth for three clones of the aquatic angiosperm Potamogeton pectinatus L., originating from 42.5 to 68° N. Plants were grown at a factorial combination of two irradiances (50 and 350 µmol m−2 s−1) and three photoperiods (13, 16 and 22 h) and morphology, gas‐exchange rate and biomass accumulation were recorded.
The overall response to variation in irradiance and photoperiod was similar for all three clones.
Differences in irradiance resulted in strong acclimative changes in morphological and physiological characteristics. At low irradiance, pronounced vertical shoot extension compensated for the limited plasticity in leaf area production, while photosynthetic capacity, apparent quantum yield and total chlorophyll concentration increased. As a result, biomass yield at the end of the experimental period was similar in both treatments.
A decrease in photoperiod also resulted in plastic changes in morphology (increase of leaf biomass per unit plant biomass) and physiology (increase of photosynthetic capacity). However, these acclimative responses did not fully compensate for differences in photoperiod, since biomass was significantly lower under 13 and 16 h photoperiods than at 22 h.
P. pectinatus is therefore phenotypically plastic, rather than locally specialized to differences in irradiance and photoperiod.
Treating individuals according to evidence: why do primary care practitioners do what they do?
Authors: Oswald Nigel , Bateman Hilarie 
Published: March 2003

AbstractResearch evidence does not necessarily translate into changed management for individual patients, but that may not mean that the evidence has been ignored. Drawing on accounts from general practitioners, we use a study of non‐rheumatic atrial fibrillation (NRAF) to illuminate the processes by which practitioners became aware of and assimilated research evidence. We follow that with an account of how the evidence was incorporated into practice protocols for anticoagulation and then applied to a review of individual patients’ records. Practitioners used a range of sources of evidence. They reported difficulties arising from their own skills and circumstances and from the perceived quality of the evidence. Creating a protocol involved overcoming problems of scheduling, resources and managing judgements about the value of the review process. In applying the protocol practitioners drew on their knowledge of the patients’ preferences, circumstances and previous specialist consultations. As a result, practitioners made judgements that evidence, combined with prior experience, did not support the initiation of anticoagulation in 52% of an unselected primary care population with NRAF. Our findings have implications for evidence‐based practice and for practitioner education.
Why are investigations not recommended by practice guidelines ordered at the periodic health examination?
Authors: Walraven Carl van , Goel Vivek , Austin Peter 
Published: March 2003

AbstractEvidence‐based guidelines recommend few routine investigations for healthy adults at the periodic health examination (PHE). However, small studies indicate that laboratory tests are commonly ordered at the PHE. This study examined PHE laboratory testing that is not recommended by recognized guidelines (‘discretionary’). Using administrative data from the universal health care system in Ontario, Canada, we studied 792 844 adults having a PHE in 1996 and the 3727 physicians who administered them. We measured the number of discretionary laboratory tests per PHE along with the patient and physician factors potentially influencing laboratory testing. A multilevel, multivariate model was used to examine the association between the number of discretionary laboratory tests at the PHE with patient and physician characteristics. A mean of 7.1 discretionary tests (SD 7.1) was ordered per PHE. Renal, haematological, glucose and lipid tests each were conducted in more than a third of PHEs. Testing varied extensively between physicians and was more common in healthy patients. With the exception of age, patient factors had little effect on discretionary testing. However, each physician factor we examined was independently associated with the number of discretionary tests. Physician specialty, practice volume and previous testing patterns had the strongest influence on discretionary testing. Discretionary investigations are common at the PHE. Testing varies extensively between physicians and seems to be driven more by physician than by patient factors. Interventions to modify discretionary test utilization at the PHE should consider these physician factors.
Towards an optimal model for community‐based diabetes care: design and baseline data from the Mayo Health System Diabetes Translation Project
Authors: Dinneen Sean F. , Bjornsen Susan S. , Bryant Sandra C. , Zimmerman Bruce R. , Gorman Colum A. , Knudsen Jens B. , Rizza Robert A. , Smith Steven A. 
Published: March 2003

AbstractThe objective of the Mayo Health System Diabetes Translation Project is to assess the impact of three different models of care on the overall quality of diabetes care in the community. The unit of study is the primary care practice with a different model of care implemented at each of three sites. The design incorporates a comparison of a diabetes guideline implementation team initiative (Practice model A), a guideline initiative combined with clinical use of a Diabetes Electronic Management System (DEMS) by primary care providers (Practice model B) and a guideline initiative combined with DEMS utilization combined with electronic review of DEMS patient encounters by an endocrinologist (Practice model C). Administrative data sets were used to define the patient population at each practice. Patients were designated as new, attending or non‐attending based on their pattern of visits over the preceding 12 months. A random sample of 200 charts from attending patients at each site was audited at baseline for diabetes‐related process and outcome measures. This audit will be repeated yearly during the 2 years of the project. Baseline data revealed significant differences across sites in adherence to certain key indicators of the quality of diabetes care including: frequency of documentation of eye examinations (19, 39 and 37% for sites A, B and C, respectively), haemoglobin A1c monitoring (64, 89 and 77%) and microalbumin monitoring (3, 15 and 6%). The interventions being assessed in this study include traditional (diabetes education; guideline implementation) and modern (DEMS; telemedicine specialist review) methods for improving the quality of diabetes care. In spite of variation in baseline quality indicators, the setting and design should lead to broad applicability of the results and help determine an optimal model of diabetes care in the community.
Use of marketing to disseminate brief alcohol intervention to general practitioners: promoting health care interventions to health promoters
Authors: Lock Catherine A. , Kaner Eileen F. S. 
Published: March 2003

AbstractHealth research findings are of little benefit to patients or society if they do not reach the audience they are intended to influence. Thus, a dissemination strategy is needed to target new findings at its user group and encourage a process of consideration and adoption or rejection. Social marketing techniques can be utilized to aid successful dissemination of research findings and to speed the process by which new information reaches practice. Principles of social marketing include manipulating the marketing mix of product, price, place and promotion. This paper describes the development of a marketing approach and the outcomes from a trial evaluating the effectiveness and cost‐effectiveness of manipulating promotional strategies to disseminate actively a screening and brief alcohol intervention (SBI) programme to general practitioners (GPs). The promotional strategies consisted of postal marketing, telemarketing and personal marketing. The study took place in general practices across the Northern and Yorkshire Regional Health Authority. Of the 614 GPs eligible for the study, one per practice, 321 (52%) took the programme and of those available to use it for 3 months (315), 128 (41%) actively considered doing so, 73 (23%) actually went on to use it. Analysis of the specific impact of the three different promotional strategies revealed that while personal marketing was the most effective overall dissemination and implementation strategy, telemarketing was more cost‐effective. The findings of our work show that using a marketing approach is promising for conveying research findings to GPs and in particular a focus on promotional strategies can facilitate high levels of uptake and consideration in this target group.
Exploring the pathology of quality failings: measuring quality is not the problem – changing it is†
Authors: Davies Huw Talfryn Oakley 
Published: March 2003

AbstractThe USA can boast a long history of investigation into quality failings in health care. From Ernest Codman and Abraham Flexner in the opening decades of this century through to the intense activity of the 1980s and 1990s, much careful study has exposed extraordinary and at times scandalous deficiencies in the quality of care (Millenson 1997;Chassin & Galvin 1998;Schusteret al.1998). Yet we are still far from developing ‘industrial strength’ quality in health care: in all but a few isolated areas, such as general anaesthesia, ‘six sigma quality’ (i.e. a handful of errors per million) seems wishful thinking (Chassin 1998). Pockets of excellence and innovation notwithstanding, the dominant experience of the past two decades has been an increasing ability to document quality failings and a seeming inability to mobilize effective action (Coye & Detmer 1998). The rich literature on health‐care quality that has sprung up over the past few decades has largely failed to provide a clear direction for quality improvement activity. This paper analyses some of the reasons why this might be so. Contrasting the relative absence of progress on health‐care quality with the relative success of disease epidemiology provides some illuminating parallels. In essence, study of the quality of care has focused largely on providing a ‘descriptive epidemiology’. Much more work is needed yet to unravel the underlying pathology of quality failings, in order to empower development of an ‘aetiological epidemiology’ of quality in health care. Such understanding is essential as a precursor to targeted and effective preventative and remedial action.
Evidence‐based medicine in general practice: beliefs and barriers among Australian GPs
Authors: Young Jane M. , Ward Jeanette E. 
Published: March 2003

AbstractIf implemented, evidence‐based medicine (EBM) in general practice will improve health outcomes for patients. This paper examines the views of 60 Australian general practitioners about EBM. While 57% of respondents had a computer in their surgery, 15% had Internet access and only 3% had access to the Cochrane Library at work. The most commonly cited barrier to EBM was ‘patient demand for treatment despite lack of evidence for effectiveness’ (45%). The next three most highly rated barriers related to lack of time. For each of three tasks of EBM, namely searching for evidence, appraising evidence and discussing the implications of evidence with patients, lack of time was rated as a ‘very important barrier’ by significantly more participants than lack of skills (McNemar’s tests: χ21 = 7.1, P = 0.008, χ21 = 14.0, P = 0.001 and χ21 = 9.0, P = 0.003, respectively). Preferred resources for EBM included clinical practice guidelines (rated as ‘very useful’ by 55%) and journals that summarize research evidence, for example Evidence‐based Medicine (52%). Systematic reviews were considered ‘very useful’ by only 15% of respondents, consistent with our finding that 30% did not understand the term ‘systematic review’. Furthermore, 43% did not understand ‘meta‐analysis’. A minority indicated they understood the terms ‘relative risk’ (23%), ‘absolute risk’ (28%) and ‘number needed to treat’ (15%) sufficiently to explain to others. Skills development is crucial to achieve EBM in general practice.
Clinical evaluation: constructing a new model for post‐normal medicine
Authors: FRCGP Kieran Sweeney MA MPhil , MRCGP David Kernick MD 
Published: March 2003

AbstractThe current paradigm in medicine is served by an explanatory model based on scientific positivism. We argue that there are inherent weaknesses in this model: its basis on reductionism, its reliance on linear thinking and its failure to incorporate human values invite a revision of our thinking about knowledge in medicine. We propose that a fresh explanatory model should be based on complexity theory, and argue that this better suits the new era of post‐normal medicine, where analytical and predictive power are obtained by stepping back and looking at the relationships and overall context of a system rather than forcing reality into a preferred disciplinary framework. Better at times to be vaguely right, we argue, rather than precisely wrong.