bluuebunny/crossref_metadata_2025 huggingface dataset:
The potential effects of sexual reproduction and seedling recruitment on the maintenance of red maple (Acer rubrum L.) populations at the northern limit of the species range
Authors: Tremblay M. Francine , Bergeron Yves , Lalonde Danielle , Mauffette Yves
Published: March 2003

Aim

For this study, we wanted to evaluate the reproductive potential of northern red maple (Acer rubrum L.) populations to identify the possible factors responsible for the scattered distribution pattern of these northern populations.

Location

Samara production and long‐term establishment of seedlings were observed along a north–south transect crossing the transition zone between continuous and discontinuous stands of red maple (47°80′–49°27′ N) in western Quebec.

Methods

Eleven populations of red maple were selected along a latitudinal gradient extending to the northern limit of the species. Seed traps were placed in each stand and distributed under the canopy of mature red maple trees. Seed abundance was tracked for 6 years from 1988 to 1993. Phenological observations were made in 1992 and 1993 at Roquemaure (Roq), a site located at the centre of the latitudinal gradient. Red maple trees were randomly selected within the population; counts of flower buds, pollinated buds and samaras produced were made in 1992–93. Samaras were collected from each branch immediately before dispersal and counted. During the summer of 1987, seedlings (< 1 cm d.b.h.) were collected and aged at each site in twenty 1 m2 quadrants and age of the seedlings (< 1 cm d.b.h.) was determined by counting the annual scars left by terminal buds.

Results

Samaras were produced even at the northern limit but large yearly variations were observed. Over the 6‐year period we counted 3 years (1989, 1990, 1993) when samara production was high, and 3 years (1988, 1991, 1992) when production was low. Phenological observations indicate that the occurrence of spring frosts at the time of flower bud flushing could contribute to decreasing the abundance of seeds. The age structure of southern localities had a relatively constant production of seedlings, as indicated by an inverse J‐shaped distribution. However, the five northernmost localities show sporadic recruitment.

Main conclusions

Populations at the northern limit are maintained essentially through vegetative reproduction and infrequent sexual recruitment. Our results indicate that regeneration within established stands through sexual recruitment is possible in all of the populations we studied. This potential becomes very low at more northerly sites and sexual reproduction alone would be unlikely to ensure successful stand regeneration. Without major disturbances in those stands, shade tolerant conifer species such as balsam fir (Abies balsamea) or black spruce (Picea mariana) would readily dominate the canopy. The discontinuous distribution of red maple stands at the northern limit is the consequence of either a random colonization of few sites during a better climatic period or remnants of a much larger distribution that has been constrained because of climatic deterioration.
Regional patterns of biodiversity in New Guinea animals
Authors: Heads Michael
Published: March 2003

Aim

To assess regional patterns of biodiversity levels in the New Guinea region by counting numbers of species of different groups in 1° grid squares.

Location

The New Guinea region.

Methods

Panbiogeographical analysis [Craw, R.C., Grehan, J.R. & Heads, M.J. (1999) Panbiogeography: tracking the history of life. Oxford University Press, New York].

Results

The following taxa were analysed: three genera of cicadas (Homoptera), freshwater fishes, snakes, and the four terrestrial orders of mammals in the region – monotremes, marsupials, bats and rodents. A total of 622 species (and subspecies) was analysed and the different centres of diversity in the various groups of animals are related to the three main geological regions of the country: Australian craton, accreted terranes, and Cainozoic volcanic arcs.

Main conclusions

Freshwater fishes are most diverse in the lower Fly – Merauke region, on the southern, Australian craton portion of New Guinea. Marsupials are the only other group with a main massing on the craton (at the Kubor Mountains area). Snakes are most diverse in the trans‐Fly region, like freshwater fishes, and also around Port Moresby. All the other groups have centres of diversity either on the craton margin or outboard of it on different accreted terranes of the New Guinea orogen. In the groups studied, only bats have a significant, albeit secondary, massing on the Bismarck Archipelago. Other terrestrial vertebrates with centres of diversity on the Bismarck Archipelago include the diverse frog genus Platymantis. The regions north and east of New Guinea (Bismarck Sea plate, Solomon Sea plate) are now occupied mainly by sea and volcanic island arcs, but biogeographers and geologists have suggested this as the site of earlier, more extensive land. The different centres of diversity in the different groups are suggested to derive from vicariant locations of early (Mesozoic – early Cainozoic) diversity rather than from different means of dispersal or other aspects of ecology.
Estimated migration rates under scenarios of global climate change
Authors: Malcolm Jay R. , Markham Adam , Neilson Ronald P. , Garaci Michael
Published: March 2003

Aim

Greenhouse‐induced warming and resulting shifts in climatic zones may exceed the migration capabilities of some species. We used fourteen combinations of General Circulation Models (GCMs) and Global Vegetation Models (GVMs) to investigate possible migration rates required under CO2‐doubled climatic forcing.

Location

Global.

Methods

Migration distances were calculated between grid cells of future biome type x and nearest same‐biome‐type cells in the current climate. In `base‐case' calculations, we assumed that 2 × CO2 climate forcing would occur in 100 years, we used ten biome types and we measured migration distances as straight‐line distances ignoring water barriers and human development. In sensitivity analyses, we investigated different time periods of 2 × CO2 climate forcing, more narrowly defined biomes and barriers because of water bodies and human development.

Results

In the base‐case calculations, average migration rates varied significantly according to the GVM used (BIOME3 vs. MAPSS), the age of the GCM (older‐ vs. newer‐generation GCMs), and whether or not GCMs included sulphate cooling or CO2 fertilization effects. However, high migration rates (≥ 1000 m year−1) were relatively common in all models, consisting on average of 17% grid cells for BIOME3 and 21% for MAPSS. Migration rates were much higher in boreal and temperate biomes than in tropical biomes. Doubling of the time period of 2 × CO2 forcing reduced these areas of high migration rates to c. 12% of grid cells for both BIOME3 and MAPSS. However, to obtain migration rates in the Boreal biome that were similar in magnitude to those observed for spruce when it followed the retreating North American Glacier, a radical increase in the period of warming was required, from 100 to >1000 years. A reduction in biome area by an order of magnitude increased migration rates by one to three orders of magnitude, depending on the GVM. Large water bodies and human development had regionally important effects in increasing migration rates.

Main conclusions

In conclusion, evidence from coupled GCMs and GVMs suggests that global warming may require migration rates much faster than those observed during post‐glacial times and hence has the potential to reduce biodiversity by selecting for highly mobile and opportunistic species. Several poorly understood factors that are expected to influence the magnitude of any such reduction are discussed, including intrinsic migrational capabilities, barriers to migration, the role of outlier populations in increasing migration rates, the role of climate in setting range limits and variation in species range sizes.
Oceanic islands as model systems for ecological studies
Authors: Vitousek Peter M.
Published: March 2003

Aim

The purposes of this paper are to suggest that a greater use of model systems would advance our understanding of ecology, and to illustrate that oceanic islands are valuable model systems for ecosystem studies in particular.

Location

The illustrations discussed herein result from studies in the Hawaiian Islands.

Methods

Sequences of sites that are similar in most respects but differ widely in temperature, precipitation or substrate age have been developed and analysed in the Hawaiian Islands. Process studies, experiments and models arrayed on these gradients are used to determine fundamental controls over ecosystem processes, with a precision that cannot be duplicated in continental ecosystems.

Results

Increasing temperatures enhance rates of decomposition to a greater extent than plant production, in soil organic matter as well as litter. Ecosystem‐level losses of N by fractionating pathways are greater in drier sites. Sea spray and long‐distance dust transport play increasing roles in the nutrient economy of ecosystems as soils become progressively older.

Main conclusions

All of the results describe processes that occur in continental as well as island ecosystems, but a number of features of islands make the processes more amenable to analysis on islands.
Complex histories of speciation and dispersal in communities: a re‐analysis of some Australian bird data using BPA
Authors: McLennan Deborah A. , Brooks Daniel R.
Published: March 2003

Aim

Demonstrate the utility of Brooks Parsimony Analysis (BPA) in showing that communities of species characterizing areas of endemism may have complex histories rather than simple histories of vicariance, and that the non‐vicariant influences can be discovered.

Location

Australia.

Methods

Primary and secondary BPA of eight clades of Australian birds inhabiting ten areas of endemism.

Results

While supporting previous general conclusions that the evolution of those members of the Australian avifauna has been influenced by two different vicariant elements, BPA also discovered substantial non‐vicariant elements, including one non‐response to a vicariance event, five instances of peripheral isolates speciation, four episodes of extinction, seven cases of post‐speciation dispersal and three lineage duplications, which could represent ancient episodes of sympatric speciation. The result of including all evolutionary events in the analysis is that seven of the ten areas have reticulate histories.

Main conclusions

Areas of endemism are not necessarily the result of simple histories of vicariance. They may also be evolutionary hot spots, places where multiple evolutionary events have occurred over a significant period of time. This produces communities heavily influenced by a variety of evolutionary processes affecting the same areas at different times.
Variation in spectral reflectance among populations of Dendrobates pumilio, the strawberry poison frog, in the Bocas del Toro Archipelago, Panama
Authors: Summers Kyle , Cronin Thomas W. , Kennedy Timothy
Published: March 2003

Aim  The goal of this study was to quantify levels of variation in spectral reflectance within and among populations of Dendrobates pumilio, the strawberry poison frog from the Bocas del Toro Archipelago.

Location  This study was carried out in the Bocas del Toro Archipelago, in the Republic of Panama, Central America.

Methods  Spectral reflectance was measured for samples of individuals from fifteen distinct island and mainland populations, using an Ocean Optics 2000 spectrometer and a BiLink portable computer.

Results  Our results provide quantitative evidence for extreme polymorphism among populations, and more limited levels of polymorphism within some populations. No obvious signs of sexual dimorphism were found. All the colour morphs appear to have relatively little reflectance in the ultraviolet part of the spectrum. There is some evidence for clinal variation in colour and pattern across some mainland populations. There is also at least one area where distinctly different morphs occur in sympatry, suggesting the possibility of incipient reproductive isolation. We argue that variation in coloration may have been enhanced by sexual selection.
Multisensory environments: are they therapeutic? A single‐subject evaluation of the clinical effectiveness of a multisensory environment
Authors: SLEVIN EAMONN , McCLELLAND ANN
Published: March 2003

• This article reviews the current literature on multisensory therapy.

• Utilizing a single‐subject quasi‐experimental design, the therapeutic clinical effectiveness of multisensory therapy in promoting relaxation in a young man with learning disabilities is evaluated.

• Findings support the hypothesis that multisensory therapy can promote relaxation.

• It is concluded that multisensory environments are therapeutic, in that they can promote relaxation, and they may also have a place in the care of people with learning disabilities who display challenging behaviours.
Pressure sore prevalence: a national survey
Authors: THORODDSEN ÁSTA
Published: March 2003

• A cross‐sectional nation‐wide sample was used to determine the point prevalence and grading of pressure sores in patients in all hospitals in Iceland (22 hospitals).

• The pressure sore prevalence was 8.9% (n = 57 patients), 7.12% for women (n = 26) and 11.2% for men (n = 31); the mean age for both sexes with pressure sores was 78.4 years.

• Grade I sores were most frequently identified and Grade IV the least. Eighty‐five per cent of pressure sores were located below the waist.

• `No dressings' and occlusive dressings were the treatment of choice for pressure sores.

• Results from this study are important for international comparisons.
Pain in older adults living in sheltered accommodation – agreement between assessments by older adults and staff
Authors: BLOMQVIST KERSTIN , HALLBERG INGALILL R.
Published: March 2003

• This study aimed to investigate the presence of pain, pain duration, localization(s), intensity, type and pharmacological treatment among older adults living in sheltered accommodation or receiving rehabilitation, as well as the agreement between pain assessments performed by staff and the older adults.

• Twenty‐nine randomly selected older adults (65+ years) and the staff who looked after them participated in a structured interview based on standardized measures for pain assessment and physical, intellectual and communicative functions.

• Pain was found to be common, with a majority of participants experiencing it every day or all of the time. Nine out of 22 of the older adults in pain had no pain relief drugs at all. Agreement between assessments by the older adults and the staff was no higher than moderate and in general pain levels were underestimated.

• The findings indicate that older adults were at risk of undetected and untreated pain and the risk was even higher for those with speech difficulties. The provision of good nursing care for older adults in sheltered accommodation requires systematic routines for frequent pain assessments.
Intensive Care Unit psychosis, the therapeutic nurse–patient relationship and the influence of the intensive care setting: analyses of interrelating factors
Authors: DYSON MARTYN
Published: March 2003

• It has been estimated that between 12.5% and 38% of conscious patients admitted to critical care settings experience Intensive Care Unit psychosis, a condition which seems to resolve upon transfer to the ward.

• This phenomenon was traditionally recognized when the patient outwardly exhibited abnormal behaviours and signs in the form of confusion, delirium, anxiety, depression, delusions and audiovisual hallucinations, yet it has been argued that due to the illness of the patient and their suppressed ability to communicate, such overt displays of unusual behaviour are the tip of the iceberg.

• In recognizing this phenomenon, it is felt that a relationship exists between Intensive Care Unit Psychosis, the therapeutic nurse–patient relationship, and the environment in which nurses' interactions with their clients occur.

• This paper will explore the interaction between these three elements while considering the implications for contemporary nursing practice.
The sleep of older people in hospital and nursing homes
Authors: ERSSER STEVEN , WILES ANNE , TAYLOR HEIDI , WADE SIAN , WALSH ROSEMARY , BENTLEY THERESA
Published: March 2003

• Disturbed sleep can affect personal wellbeing and impede the rehabilitation and recovery of older people from illness.

• This paper reports the findings of a pilot study which included examination of sleep quality and sleep patterns of older people in community hospital and nursing home settings.

• A marked proportion of older people reported sleeping well in nursing care settings, and those in nursing homes slept better than those in the community hospital.

• The main causes of sleep disturbance in both settings were: needing to go to the toilet, noise, pain, and discomfort; a similar pattern was seen across the different settings.

• No discernible difference was found in quality of sleep and whether patients felt rested or not between those patients on hypnotic medication and those who were not.

• The implications of the findings for practice and future research are discussed.
Recognition of depression by staff in nursing and residential homes
Authors: Bagley Heather , Cordingley Lis , Burns Alistair , Mozley Caroline Godlove , Sutcliffe Caroline , Challis David , Huxley Peter
Published: March 2003

• Newly admitted residents in long‐term care facilities are particularly vulnerable to depression and the early recognition and treatment of depression is therefore crucial around the time of admission to a home.

• Staff from 30 nursing and residential homes were asked to assess newly admitted residents for depression using HoNOS 65+ and their responses were compared with residents’ scores on the Geriatric Depression Scale (GDS‐15).

• The findings indicated low levels of recognition by staff, with rates ranging from 15% to 27% of those identified as depressed, depending on the definition of depression used.

• There was no statistically significant difference in the rate of recognition between nursing staff and other care staff.

• A staff survey conducted in the 30 study homes indicated that fewer than 2% had received specific in‐service training on depression in older people.

• The findings suggest that more needs to be done to raise staff awareness of depression in residents of nursing and residential homes, particularly in newly admitted residents.
Student nurses’ perception of independence of supervision during clinical nursing practice
Authors: Löfmark Anna , Carlsson Marianne , Wikblad Karin
Published: March 2003

•  The purposes of this longitudinal study were to examine Swedish student nurses’ perceptions of independence and to explore to what extent the students had had opportunities to practise different tasks during clinical practice.

•  Data were collected on weekly self‐assessment forms during the first and final clinical courses of a 3‐year nursing programme for 60 and the remaining 48 students, respectively.

•  The majority of the students rated themselves as being independent of supervision to a great extent both at the beginning and throughout the clinical courses. Some students reported no or few opportunities to practise certain tasks during both courses.

•  Factors that may have influenced the students’ perception of independence are discussed, such as preparation before the clinical courses and the importance students gave to certain tasks.

•  Clinical practice should be carefully planned and individualized to facilitate students’ opportunities to practise different tasks.
Intensive care nurses’ experiences of caring for brain dead organ donor patients
Authors: Pearson Alan , Robertson‐Malt Susie , Walsh Ken , Fitzgerald Mary
Published: March 2003

•  This study was designed to identify the feelings and experiences of critical care nurses who have been involved in nursing brain dead patients prior to organ donation.

•  The purpose of the study was to generate knowledge which informs the discipline of nursing.

•  A number of themes relating to nurses’ experiences of caring for brain dead organ donor patients were uncovered in this interpretative study.

•  Overall, caring for patients who are diagnosed as brain dead is a challenging experience for nurses and they are intensely involved in a search for meaning in each event.

•  The interpretative analysis in this study has revealed a range of meanings articulated by the nurses involved. However, the primary focus of care – as identified by the participating nurses – was the donor family.
Developing a unified language for children’s nurses, children and their families in the United Kingdom
Authors: Lyte Geraldine , Jones Kathryn
Published: March 2003

•  This paper presents a taxonomy of Infant, Child and Adolescent (ICA) nursing diagnoses and clinical outcomes that has been developed with the co‐operation of nurses caring for children in the United Kingdom.

•  Three focus group interviews were conducted in one acute care NHS trust in London (referred to as the host trust in this paper) in 1998/99, in which participants were asked to consider nursing and family factors relevant for identifying and providing care.

•  A total of 28 ICA diagnoses, including definitions, defining characteristics and outcomes, were identified for clinical testing and included in the ICA taxonomy.

•  The ICA diagnostic labels and outcomes for care were further tested for their relevance for clinical practice in a Delphi Survey carried out in 1999 and their use in clinical practice began in 1999.

•  This research augments the findings from an initial Delphi survey carried out in 1993 and case study research in 1996.

•  The previous research initiated the development of a unified language for children’s nurses, children and their families, to aid communication and decision‐making.

•  Implications of this and future research for clinical practice, nationally and internationally, are also discussed.
Elders’ needs and experiences of receiving formal and informal care for their activities of daily living
Authors: Roe Brenda , Whattam Maxine , Young Heather , Dimond Margaret
Published: March 2003

• Older people living in the community or institutional settings are more likely to require help with their activities of daily living, with women more likely than men to need some help.

• The interviews in this qualitative study were conducted with a convenience and purposive sample of 20 elders living in Southeast Washington, USA, at home or in institutional settings, receiving informal or formal health care.

• Findings related to personal and instrumental activities of daily living are reported and include elders’ experiences and views relating to the help and assistance they receive.

• The majority of elders needed help with their instrumental activities of daily living, provided by informal networks, whether living at home or in institutional settings. This help constituted social care. Formal health care with personal activities of daily living was required only by a minority of elders and constituted those with the greatest disability and dependency.
Complications associated with enteral nutrition by nasogastric tube in an internal medicine unit
Authors: Pancorbo‐Hidalgo Pedro L. , García‐Fernandez Francisco P. , Ramírez‐Pérez Carmen
Published: March 2003

• Enteral nutrition through a nasogastric tube is a technique often used with hospitalized patients when they present problems with oral nutrition.

• Patients receiving enteral nutrition show several kinds of complications such as diarrhoea, vomiting, constipation, lung aspiration, tube dislodgement, tube clogging, hyperglycaemia and electrolytic alterations.

• We present a prospective and observational study carried out in an Internal Medicine Unit with 64 patients who were fed by a nasogastric tube. From the results it can be seen that older people represented a majority (the average age was 76.2 years), and difficulty in swallowing was the main reason for beginning enteral nutrition.

• The complications which appeared were: tube dislodgement (48.5%); electrolytic alterations (45.5%); hyperglycaemia (34.5%); diarrhoea (32.8%); constipation (29.7%); vomiting (20.4%); tube clogging (12.5%); and lung aspiration (3.1%). We discuss the possible relationship between the different factors associated with the enteral nutrition procedure and the occurrence of these complications.

• Finally, some nursing interventions are suggested, such as: checking the gastric residue periodically; attempting to place the tube in the duodenum in unconscious patients; and the use of protective mittens in disturbed patients.
Cross‐boundary working: a macro‐political analysis of the impact on professional roles
Authors: MASTERSON ABIGAIL
Published: March 2003

• This paper reviews the policy developments impacting on professional roles and boundaries in health and social care.

• A macro‐political analysis is used to offer a challenging critique to many of the assumptions associated with cross‐boundary working.

• It explores issues such as: whether or not new nursing roles are truly being developed to meet need; the myths and realities of interprofessional working; how competence can be assured; the need for new forms of professional regulation; the implications for professional education of initiatives such as national occupational standards and shared learning; planning the future health care workforce; and the need for rigorous and robust evaluation of service and role developments.

• Through this exploration the likely consequences of political and professional initiatives for both cross‐boundary working and the profession of nursing itself are illuminated.
Older people seeking solutions to constipation: the laxative mire
Authors: ANNELLS MERILYN , KOCH TINA
Published: March 2003

• This article reports an extensive descriptive survey of 90 older people (65+ years) living in the community who sought through in‐depth, semistructured interviews to explore their experiences and responses to constipation.

• The composite story of these older people is that seeking a solution to constipation may be fraught with great difficulty. Most commonly tried are laxatives, yet laxative use can be like a mire. The older people tend to be uncertain of which way to turn to avoid getting stuck in a murky conglomeration of laxative options.

• The imperative for self‐management of constipation is strong amongst most of the older people and the process in which they engage when seeking for a solution is discussed. There is an evident frustrating lack of readily identifiable and accessible services and information that could help them navigate successfully through or around this mire. `Through the mire' would be the appropriate use of suitable laxatives with minimal side‐effects. `Around the mire' would be the gaining of useful solutions other than laxative use. Solutions may be strategies to prevent constipation or to treat constipation.

• The needs of these older people seeking solutions to constipation are grouped into two main categories: provision of accessible, empathetic and useful advice about affordable solution choices, and accessibility to solutions, including laxatives, where evidence‐based knowledge informs selection or prescription of the solution. Eight major recommendations, including research suggestions, are offered for consideration.
Motivation and interface design: maximising learning opportunities
Authors: Lewis R. , Stoney S. , Wild M.
Published: March 2003

Abstract Instructional multimedia is creating a revolution in universities. Academic staff are being urged to transfer instruction to a format suitable for either CD/ROM and/or the Internet, principally the World Wide Web. Many, it seems, simply take their existing course materials, add image and sound without proper consideration of the nature of the medium in which they are seeking to instruct and present the product to their students. In essence, it appears they ignore the need to motivate their students to work with their instructional multimedia materials. It is a contention of this paper that the user‐interface to instructional multimedia is strategically important: if it is poorly designed students will not be intrinsically motivated to make use of the product or to learn with it. Interfaces that motivate learners are realistic, easy to use, challenging and engaging. Superior interfaces have some of the elements of a game: they provide the user with a functional model of task, content and processes; they encourage exploration and engagement; and they demonstrate cognisance of design considerations such as interactivity, functionality, learner control and cognition.
Questioning teachers about their use of portable computers
Authors: Phillips R. , Bailey M. , Fisher T. , Harrison C.
Published: March 2003

This paper analyses case studies from the ‘Multimedia Portables for Teachers’ pilot project where two teachers in more than 500 English schools received portable computers to use at home and at school for one year to develop confidence and competence. In‐depth interviews with a representative sample of 60 of the teachers revealed a disparate range of uses that reflected teachers’ needs and interests, and often were imaginative and innovative. For nearly all the teachers the project was successful on a number of criteria: they gave time and commitment, they gained confidence, they increased their number of IT (information technology) skills, and certain IT activities became a natural and regular part of their work. Gains were evident regardless of the baseline from which they were starting. Issues discussed include the use of email and WWW, prior access to computers, use by the teacher's family, the value of portability, and the relationship with colleagues. Some practical recommendations are made for future schemes of this kind.
Using conferencing to support a culture of collaborative study
Authors: Rimmershaw R.
Published: March 2003

Five short undergraduate courses were run, four using a computer‐based conferencing system and one paper‐based to support collaborative study practices. The seriousness of the emphasis on collaborative study was communicated to the students not only through the use of conferences, but also of students’ own writing as set reading material, and of material from the conference as the basis for the final examination. Students responded best when the tutor participated in conferences in a similar style to themselves. Even when some computer‐based features were lost, as in the course which used a paper file for public writing, students made significant use of this forum. However factors outside the design of the system for supporting collaboration seemed to play the strongest part in determining the value students found in using the it. These included the physical conditions, initial induction process, tutor's participation style, and assessment practices.
Examining a collaborative assessment process in networked lifelong learning
Authors: McConnell D.
Published: March 2003

This case study paper is concerned with the development of professional practice in networked learning environments. Through the presentation of one case (a) an assessment process in a networked learning environment which involves the learner, their peers and a tutor in making judgments about the learner's formal coursework; and (b) the role of the tutor/ teacher in these processes are examined. From an analysis of the case it is suggested that assessment should be a learning event and that networked learning course participants should be involved in making judgments about their own and their peers’ learning. The benefits to learners and tutors of these collaborative learning processes are examined and discussed.
Visuospatial working memory in learning from multimedia systems
Authors: Gyselinck V. , Ehrlich M.‐F. , Cornoldi C. , De Beni R. , Dubois V.
Published: March 2003

Abstract  Multimedia systems involve the association of various types of information: verbal information presented visually or auditorily, static or dynamic pictorial information, and sound information. In a cognitive approach, integrating this information involves complex processes constrained by properties of the learner's cognitive system, and especially by the capacity of working memory. This paper, reports on an experiment focused on the integration of verbal and pictorial information when students learn a series of physics concepts. The involvement of the visuo‐spatial working memory was investigated by means of a dual‐task paradigm. Results show that pictorial information enhances the learning process. They also suggest that the visual and the spatial components of visuospatial working memory should be considered separately. Finally, they emphasise the need to consider the limitations in cognitive resources available to the learner.
The end of software training ?
Authors: Van Merrienboer J.J.G.
Published: March 2003

Abstract  The contributions to this Special Issue are discussed within an Instructional Design framework. A distinction is made between contributions concerned with task and content analysis, design and selection of instructional methods, and instructional message design. Three major trends indicate a shift in focus:

• from narrow learning tasks for operating the software per se to rich learning tasks for using the software in the context of meaningful task performance;

• from methods that stress procedural descriptions and related exercises to methods that stress guided exploration and scaffolding and so aim at deep system understanding, and

• from low‐load presentation formats to formats that also evoke active processing and elaboration of presented information.

These trends indicate the end of software training. It has grown up and is no longer fundamentally different from regular professional skills training.
Range size, dispersal and niche breadth in the herbaceous flora of central England
Authors: Thompson Ken , Gaston Kevin J. , Band Stuart R.
Published: March 2003

1It has been suggested that rare species differ from related common species in a variety of traits, including (among others) niche breadth and dispersal ability. We set out to test these ideas in the flora of central England.

2We used two measures of range: number of hectads in Britain (national range) and number of 1 km2in a 3000‐km2area of central England (local range). In each case we regressed phylogenetically independent contrasts in geographical range against contrasts in range of germination temperature (one aspect of fundamental niche breadth), terminal velocity of dispersule (a measure of wind dispersal capacity), seed weight and specialism index (a measure of the diversity of habitats exploited in central England). Seed weights and germination temperature were known for 263 species, specialism index for 261 and terminal velocity for 178.

3Specialism index explained by far the largest part of the variance in local and national range. Seed weight, terminal velocity and germination temperature each explained only 2–4% of the variation in local range, and none of the variation in national range.

4Most previous attempts to relate niche breadth and dispersal ability to range have concerned animals. There is little convincing published evidence for plants, and in the British herbaceous seed plants studied here the best predictor of range was diversity of habitats exploited. This pattern was independent of phylogeny.
The exploitation of heterogeneity by a clonal plant in habitats with contrasting productivity levels
Authors: Kleijn David , Van Groenendael Jan M.
Published: March 2003

1
 We investigated habitat exploitation by the rhizomatous grass Elymus repens in a heterogeneous environment in both productive and unproductive habitats. We tested whether there was selective entry of rhizomes into favourable microsites or random exploration of the habitat, and whether the benefits of selective exploitation were higher in productive than unproductive habitats.

2
 Trays were divided into four quadrants around a common central area. Homogeneous environments were created by planting vegetation throughout the trays; heterogeneous environments were created by planting only centre and two opposite quadrants. Contrasting productivity levels were established by fertilizing half of the trays of each environment type. A single rhizome fragment of E. repens was planted in the centre of the trays and allowed to exploit the trays for two growing seasons.

3
 
Elymus repens effectively exploited habitat heterogeneity at both productivity levels. However, only unproductive trays showed preferential growth of rhizomes into bare quadrants.

4  In the productive trays individual rhizomes that grew into bare quadrants showed a significantly greater production of shoots and total biomass than those that grew into vegetated quadrants. Smaller, non‐significant effects were observed at lower productivity.

5  Increased growth of primary rhizomes, once they had entered a bare quadrant, with or without selective growth into these patches, led to similar increases in heterogeneous compared to homogeneous trays at the two productivity levels (3.0 vs. 2.7). Heterogeneity was not therefore more effectively exploited at high productivity.

6  We suggest that sectorial transport of nutrients through the rhizomes, resulting in directional outgrowth of bud meristems into the bare quadrants, may have been responsible for the selective placement of rhizomes in the unproductive trays. Our results suggest that selective entry of rhizomes into favourable microsites may complement morphological plasticity in enabling rhizomatous plants to forage in heterogeneous environments.
Environmental heterogeneity and species diversity of forest sedges
Authors: Bell Graham , Lechowicz Martin J. , Waterway Marcia J.
Published: March 2003

1 A field experiment was designed to investigate the relationship between environmental heterogeneity and species diversity in a group of sedges (Cyperaceae: Carex) growing in old‐growth forest.

2 A measure of environmental quality, as perceived by the sedges, was obtained from the survival of clonal ramets of 11 species of Carex planted at 10‐m intervals along each of three 1‐km transect lines.

3 The resident assemblage of sedges was censused along the same three transect lines and along a further 24 km of survey lines in the same forest.

4 The general state of a site was represented by the overall survival of the experimental implants at that site. The general environmental variance between sites provided a measure of environmental heterogeneity. This could be partitioned into a specific variance (mean environmental variance of species) and an environmental covariance. The rate of increase of the general and specific variances with distance between sites reflected environmental structure.

5 The three transects differed in scale. The species diversity of the resident Carex assemblage was correlated with general environmental quality both among and within transects.

6 The three transects differed in structure. The number of resident species, relative to the number expected from the number of individuals sampled, was greatest on the most coarse‐grained transect (steepest increase in general environmental variance with distance).

7 Within each transect, species diversity increased with general environmental variance because the specific correlation of performance (correlation among species of survival in pair‐wise combinations of sites) decreased as the general environmental variance increased.

8 The effect of specific environmental variance was weaker. Overall survival of a species on the transects was not correlated with its abundance in the forest. Neither the transects nor a targeted implant experiment provided evidence for a close relationship between the distribution of species and the state of the environment.

9 As a general explanation of our results, we propose a ‘marginal‐specialist’ model in which the species that dominate the most productive sites also have the broadest ranges, whereas other species are superior in a more restricted range of less productive sites.
The replacement series
Authors: Jolliffe Peter A.
Published: March 2003

1 The replacement series has been used widely to assess interference, niche differentiation, resource utilization, and productivity in simple mixtures of species. Correctly used, the approach can lead to some valid interpretations. In order to avoid criticisms, however, researchers should appreciate the assumptions and limitations of this methodology.

2 A replacement series contains confounded species density treatments. Replacement series experiments therefore provide collective results and cannot distinguish separate contributions to interference by the constituents of a mixture.

3 In a replacement diagram, trends in observed yields per species can be due to a multitude of possible levels of intra‐ and interspecific interference. Similarly, trends in expected yields per species do not represent specific levels of intra‐ and interspecific interference. A replacement series is therefore unsuitable for the quantitative evaluation of interference or niche differentiation.

4 A standard replacement series, but not a proportional replacement series, may be used to detect an imbalance between intra‐ and interspecific interference for a component of a mixture. If competition for resources is assumed or known to be the sole cause of interference, then such experiments yield a qualitative evaluation of complementary resource utilization by the mixture components.

5 The possibility of total density dependence impedes generalization from a replacement series result. Other biases, due to initial size and time of observation, may occur with replacement series and related experimental structures.

6 Results from a replacement series are of questionable value in predicting the long‐term outcome of an association between species.

7 Replacement series are a valid setting, but not the only possible setting, for some kinds of yield comparisons. These include comparing productivity of monocultures with that of simple species mixtures.

8 In some cases, interpretations obtained from replacement series have not been confirmed using other methods but, on the whole, conclusions from replacement series do not seem to be characteristically different from those obtained using other approaches.
Ecological mechanisms of reproductive isolation between diploid and tetraploid Chamerion angustifolium
Authors: Husband And Brian C. , Schemske Douglas W.
Published: March 2003

1  Theoretical models indicate that coexistence of diploid and polyploid individuals in sympatric populations is unlikely when mating is random among cytotypes and hybrids are inviable. However, coexistence may be facilitated by prezygotic isolating mechanisms that reduce intercytotype mating and increase assortative mating.

2
 We examined the ecological factors regulating intercytotype mating in Chamerion (formerly Epilobium) angustifolium by measuring floral morphology, flowering synchrony and insect foraging preferences in a mixed population within a diploid–tetraploid contact zone. We also calculated the minimum rate of between‐cytotype mating from estimates of the frequency of triploid offspring.

3  Diploids had significantly shorter and narrower petals as well as shorter styles than tetraploids. Inflorescences were significantly taller in tetraploids than diploids, but the mean number of open flowers per inflorescence did not differ. Diploid and tetraploid flowering periods overlapped by 51%, with diploid stems flowering earlier.

4  In a plot of 20 diploid and 28 tetraploid stems that were flowering simultaneously, only 26% of all bee flights were between flowers on different stems. Of the total flights between inflorescences, only 15% were between different cytotypes. The combined effects of flowering asynchrony and insect foraging reduced the opportunities for intercytotype mating from 49% expected if mating is random to about 2% of the total number of pollinator flights.

5  A computer simulation indicated that the deficiency of pollinator flights between cytotypes was due largely to the spatial structure of cytotypes and limited pollinator flight distances within the observation plot. The frequency of triploid offspring produced during the period when both cytotypes were in flower was 6.6%, similar to the proportion of flights observed between flowers on different cytotypes (4%).

6
 The results indicate that flowering phenology and insect behaviour (as influenced by clonal structure) have a significant effect on prezygotic mating isolation and triploid production, and may contribute to the maintenance of mixed cytotype populations in Chamerion angustifolium.
Soil seed bank dynamics in hayfield succession
Authors: Bekker Renée M. , Verweij Geurt L. , Bakker Jan P. , Fresco Latzi F. M.
Published: March 2003

1  Changes in the species composition of the soil seed bank were determined in a dry and a more species‐rich wet chronosequence. Each sequence represented a 25‐year hayfield succession following cessation of fertilizer application in the Drentse A Nature Reserve (NL), where the vegetation has been studied since 1972.

2  The number of seeds of many late successional species showed a significant increase during succession with only two characteristic late species present in the seed bank of the early stage of each series. Most of the early successional species showed a decrease in the number of seeds, which paralleled their relative frequency within the vegetation. Overall, seed density and species diversity of the seed bank was higher in the wet than the dry chronosequence.

3  Mean values for seed longevity were calculated for each successional phase in each series using a published seed bank data base. When based simply on the presence of species, the seed longevity index decreased significantly during the wet‐series succession in both surface and deeper seed banks and in the vegetation. When based on the relative frequency of species present, the index decreased significantly in both series but only in the surface seed bank and the vegetation.

4
 Comparison with data for an ancient undisturbed wet hay meadow in England suggests that seed longevity of hayfield species is generally low. Similarity between seed bank and established vegetation was low in both the undisturbed British meadow (only 47%) and in the relatively young Dutch study sites (c. 50%).

5  The soil seed bank is unlikely to determine hayfield succession in the Drentse A Nature Reserve, since the composition of the soil seed bank tended to follow that of the above‐ground vegetation. Increases in plant species richness following the cessation of fertilizer application, the main goal of restoration management, therefore depend to a large extent on an influx of the seeds of most species from outside the site.