bluuebunny/crossref_metadata_2025 huggingface dataset:
Vegetation and disturbance history of a rare dwarf pitch pine community in western New England, USA
Authors: Motzkin Glenn , Orwig David A. , Foster David R.
Published: March 2003

Aim  This study documents the vegetation history and age‐structure of a rare, ridgetop dwarf pine–oak community and compares the dynamics of this unusual vegetation with similar dwarf pine communities found elsewhere in the north‐eastern United States (US).

Location  The study area is located on the summit of Mt Everett in the Taconic Mountains of south‐western Berkshire County, Massachusetts, USA (42°06′N 73°26′W).

Methods  Vegetation composition, tree age‐structure, physical site characteristics, and evidence of fire and other disturbances were determined for twelve 15 × 15 m plots in dwarf pine–oak vegetation and two plots in oak forests on the summit. Age‐structure analyses, tree‐ring patterns, and historical records of human and natural disturbance were used to investigate the long‐term history and dynamics of the summit vegetation.

Results  The summit of Mt Everett has been dominated by dwarf pines (1–3 m tall) and ericaceous shrubs similar to the modern vegetation throughout the historical period; there is no evidence that tall‐stature forests occurred on the site at any point in the past few centuries. The summit supports uneven‐aged stands; pitch pine (Pinus rigida) recruitment began in the 1830s and occurred in every decade since the 1860s. Average pitch pine age is seventy‐eight with a range of 12–170 years. Red oak (Quercus rubra) and red maple (Acer rubrum) increased in importance in the twentieth century, with most stems establishing from 1940 to 1980. Pitch pine radial growth rates averaged <0.5 mm year−1 while red oak and red maple averaged 1.0 and 0.8 mm year−1, respectively. In some areas, hardwoods have overtopped pitch pines, apparently resulting in pitch pine mortality. Whereas most dwarf pitch pine communities occur on sites that burn frequently and have a high degree of cone serotiny, we found no evidence of recent fires or cone serotiny. Small amounts of macroscopic charcoal that we documented may have resulted from fires in the pre‐European or early historical periods.

Conclusions  Harsh edaphic conditions and chronic low‐level disturbances on the summit, including frequent winter storms, have apparently contributed to the establishment, long‐term persistence, and slow radial growth of dwarf pitch pines on Mt Everett. The ability of dwarf pines to persist on a site in the absence of frequent fire is highly unusual among North‐eastern barrens and has not been well‐incorporated into previous conceptual ecological models of these communities. Our results suggest that even among North‐eastern barrens, the summit of Mt Everett is characterized by highly unusual vegetation and dynamics. The site has long been recognized as regionally significant and should be afforded the strictest conservation protection. With no evident history of human disturbance or recent fire, there is no apparent need for immediate active management of the site.
A review of the factors influencing nonrecurrence of venous leg ulcers
Authors: Peters Jean
Published: March 2003

• The literature on external prevention strategies for recurrence of venous leg ulcers is reviewed to assess the extent of existing knowledge and the effectiveness of preventive practices currently employed.

• Although there is some evidence that the use of compression hosiery is effective in reducing the incidence of recurrence, other strategies cited for ulcer prevention are not supported by documented research.

• It is also evident that patient compliance with wearing compression hosiery could be improved and that an evaluation of the effectiveness of hosiery currently available is overdue.

• With district nurses spending up to 50% of their time treating venous leg ulcers, not only are they in a key position to disseminate information on effective prevention to patients, but in so doing they should contribute to a reduction in their leg ulcer treatment caseload.

• To do this, nurses need to be more informed on aspects of venous leg ulceration and prevention strategies.
Some issues in the assessment of clinical practice: a review of the literature
Authors: Chambers Margaret A.
Published: March 2003

• This paper focuses on some issues in the assessment of clinical practice of particular interest to the author.

• The assessment of students of nursing in clinical practice is acknowledged as a long‐standing and difficult problem.

• There is little consensus as to what is meant by the term competence when applied to clinical nursing practice, making the assessment of clinical practice a mainly subjective process.

• The English National Board (1989) has distinguished the term mentor as meaning counsellor and guide, nevertheless the roles of mentor and assessor are frequently confused.

• It is suggested that nurses are equally accountable for the accurate assessment of student nurses' clinical skills as they are for their own practice.

• The validity and reliability of tools used to assess clinical practice are difficult to establish, making objective assessment complex at best, and impossible at worst.

• The assessment of the reflective process has been suggested as one way out of the dilemma, but the ability to think and to write does not necessarily translate into competent clinical practice.
Exploring the concept of user involvement in mental health through a participation continuum
Authors: Hickey Gary , Kipping Cheryl
Published: March 2003

• Although recent years have seen an increased emphasis on involving service users in decisions about their care, there has been limited exploration of the theories and ideologies underpinning the concept.

• This paper identifies two approaches to user involvement, each with implications for the extent to which users can be involved in decisions about their care. The approaches are linked through a ‘participation continuum’ which is a framework through which the concept of user involvement can be explored, and against which practice can be assessed.

• The framework must be seen within the context of constraints to user involvement. A more realistic assessment of the extent to which users can be involved in decisions can then be made and the risks of raising unrealistic expectations avoided.
Nursing practice draws upon several different ways of knowing
Authors: Berragan Liz
Published: March 2003

• This paper explores the proposition that nursing practice draws upon several different ways of knowing.

• It highlights difficulties often faced by practising nurses in defining what they do and hence what it is that constitutes nursing practice.

• Following formal definition and analysis of sources of literature regarding nursing knowledge, issues such as the origins of knowledge and the sources of nursing knowledge are addressed.

• The types of knowledge required to enhance nursing practice are discussed, focusing upon future opportunities and innovations in the generation of knowledge for nursing.

• Finally, recommendations are made regarding the way forward for nurses endeavouring to communicate the complexities of nursing practice.
The role of the paediatric nurse in promoting paediatric right to consent
Authors: ORR FIONA E.
Published: March 2003

• This article examines the processes involved in obtaining informed consent focusing on the abilities and legalities related to a child's right to consent.

• Most authors who have researched when a child may be considered competent to give a valid consent propose that the child must be 14 years old and thus able to think abstractly and consider the risks and benefits of the planned treatment.

• Qualitative research on this topic reveals that a child's previous life experiences can influence their ability to comprehend the intervention.

• This suggests children under 14 years of age may be regarded as competent.

• The confusion around the prevailing legal situation is examined.

• The role of the paediatric nurse is explored to distinguish areas in which the nurse could potentially make a contribution to the process of gaining consent from children.

• The paediatric nurse's role as an assessor, educator and evaluator are identified.
Nurses’ perceptions of caring as documented in theory and research
Authors: Patistea Evangelia
Published: March 2003

• Caring represents an essential human need and the fundamental component of the nursing profession.

• A deep understanding of caring and the way it is expressed will help nurses to provide high‐quality services and, more importantly, to understand nursing itself.

• This review of the literature indicates the importance of examining caring both conceptually and operationally.

• Based on theoretical and research accounts, it also presents the wide variety of ways in which caring is conceived and expressed within the professional field.

• Caring is examined from anthropological, philosophical and psychosocial perspectives.

• In this paper implications for practice and research are outlined.
Parents’ experiences of general hospital admission for adults with learning disabilities
Authors: Fox David , Wilson David
Published: March 2003

• General hospital care for people with learning disabilities is strongly emphasized in recent health policy.

• Ten sets of parents were interviewed about their experiences of general hospital inpatient care for their adult sons and daughters with learning disabilities.

• Findings in the areas of placement, occupation, basic nursing care, feeding, toileting, nursing attitudes, staffing and procedures are presented.

• Recommendations are made for changes to reported nursing practice to improve the quality of general hospital care for people with learning disabilities.
Information needs of women with non‐invasive breast cancer
Authors: Brown Marina , Koch Tina , Webb Christine
Published: March 2003

• The purpose of this inquiry was to gain a better understanding of the experience of women who have had surgery for non‐invasive breast cancer. In particular, issues surrounding information were explored.

• Six women who had undergone surgery for a non‐invasive breast cancer (ductal carcinoma in situ or DCIS) participated in the research and an interpretive approach was used to guide the research process.

• In‐depth interviews took place in the women’s homes and the interviews were transcribed verbatim.

• Through a process of familiarization with the tapes and transcripts, clusters of significant statements were assembled into individual stories of each woman’s experience.

• The findings highlight the individual nature of the experience of information, with the women wanting information that is tailored to their personal needs.

• Nurses can provide care that is more responsive to the information needs of each woman by being aware of the diverse ways in which women experience information.

• This small study contributes to the limited understanding of the experience of having surgery for ductal carcinoma in situ and the information needs of these women.
Psychological adjustment of critically injured patients three months after an unexpected, potentially life‐threatening accident
Authors: Grossman Mary , Lee Virginia , Van Neste Kenny Jocelyne , McHarg Linda , Godin Maryse , Chambers‐Evans Jane
Published: March 2003

• Cognitive processing and meaning theories suggest that a patient’s psychological adjustment following a traumatizing event depends on an ability to cognitively integrate the trauma event and restore a sense of meaning in life. These processes may be facilitated by using coping strategies such as sharing concerns, mobilizing support, and reframing.

• A correlational study explored the magnitude of the relationships between psychological adjustment, cognitive processing, sense of meaning, and coping strategies in critically injured patients 3 months after a potentially life‐threatening injury.

• Fifty‐one critically injured patients completed the Brief Symptom Inventory, Bradburn’s Psychological Well‐Being Scale, Impact of Events Scale, the Meaning‐of‐Illness Questionnaire, and Family Crisis‐Oriented Personal Evaluation Scale in face‐to‐face interviews 8–12 weeks after the accident. Bivariate and partial correlation coefficients were used to test the main hypothesis, and Pearson correlation coefficients, to address the three research questions.

• The main hypothesis that psychological adjustment will be significantly related to cognitive processing, sense of meaning, and use of coping strategies in critically injured patients 3 months after the accident was partially upheld.

• Depressive symptomatology was found to be significantly associated with increased cognitive processing efforts and a decreased ability to acknowledge the accident’s negative effects on the self.

• In contrast, psychological well‐being was found to be significantly associated with decreased cognitive processing efforts and an increased ability to acknowledge the accident’s negative effects on the self.

• Restoring a sense of meaning, however, was found to be unrelated to sharing concerns, mobilizing support and re‐framing. The potential theoretical and clinical implications of the findings for nursing practice are discussed.
An evaluation of a teaching intervention to improve the practice of endotracheal suctioning in intensive care units
Authors: Day Tina , Wainwright Steven P. , Wilson‐Barnett Jenifer
Published: March 2003

• Endotracheal suctioning is a frequently performed procedure that has many associated risks and complications. It is imperative that nurses are aware of these risks and are able to practise according to current research recommendations.

• This study was designed to examine to what extent intensive care nurses’ knowledge and practice of endotracheal suctioning is based on research evidence, to investigate the relationships between knowledge and practice, and to evaluate the effectiveness of a research‐based teaching programme.

• This quasi‐experimental study was a randomized, controlled, single‐blinded comparison of two research‐based teaching programmes, with 16 intensive care nurses, using non‐participant observation and a self‐report questionnaire.

• Initial baseline data revealed a low level of knowledge for many participants, which was also reflected in practice, as suctioning was performed against many of the research recommendations.

• Following teaching, significant improvements were seen in both knowledge and practice. Four weeks later these differences were generally sustained, and provide evidence of the effectiveness of the educational intervention.

• The study raised concern about all aspects of endotracheal suctioning and highlighted the need for changes in nursing practice, with clinical guidelines and focused practice‐based education.
Communication issues for the interdisciplinary community palliative care team
Authors: Street Annette , Blackford Jeanine
Published: March 2003

• This paper discusses the findings of a critical study that examined the communication patterns between nurses and general practitioners (GPs) providing palliative care in Australia.

• Interviews and focus groups involved 40 palliative care nurses who worked in the three settings of care: community, hospice and hospital.

• Issues that impeded effective communication strategies between palliative care nurses and GPs were networking, case management, multiple service providers, lack of standardized documentation and formal tracking of clients, along with difficulties in transmission of relevant practice knowledge.

• Supporting strategies for effective formal modes of communicating and reporting are described.
Communication skills: some problems in nursing education and practice
Authors: CHANT SIMON , JENKINSON TIM , RANDLE JACQUELINE , RUSSELL GRAHAM
Published: March 2003

• This article is based on a literature review carried out as part of a study of communication skills training in pre‐registration nursing education in England in 2000.

• A systematic literature search was conducted and 200 articles were found that were relevant to the study.

• Definitional problems were found, with terms such as communication skills and interpersonal skills being used interchangeably.

• The term communications strategies is suggested to overcome these problems, as it reflects the logical organization of a number of different communication skills within a theoretical or empirical framework.

• Problems in current communication skills teaching and social barriers to using communication skills in practice are discussed.

• It is concluded that problems continue to exist in these areas and that an emphasis on both aspects is needed if patient and staff satisfaction is to be improved.
Nurses' experience with vancomycin‐resistant enterococci (VRE)
Authors: MITCHELL ANN , CUMMINS TERESA , SPEARING NATALIE , ADAMS JUNE , GILROY LISA
Published: March 2003

• The emergence and spread of resistant organisms, in particular vancomycin‐resistant enterococci (VRE), is an issue facing all staff in acute hospitals.

• This study explored how nurses coped with the responsibility of halting further spread of this organism during an outbreak.

• VRE‐positive patients were cohorted with nurses who cared for them in an endeavour to contain the spread of VRE.

• The majority of nurses found the situation extremely stressful because of the need to act as `gatekeepers' responsible for educating and monitoring the practices of staff and visitors. The nurses reported that they felt they were inadequately supported, were blamed for the outbreak, and that they had an increased workload as they took on duties of other staff.

• The results reinforce the need for a multidisciplinary team approach to education and control of VRE, more support for nursing staff cohorted with VRE‐positive patients, and stringent adherence to infection control measures by all hospital staff.
The quality of nursing care as perceived by individuals with chronic illnesses: the magical touch of nursing
Authors: THORSTEINSSON LAURA SCH
Published: March 2003

• Providing high quality nursing care is the vision of nursing. The literature has revealed gaps between the perspectives of patients and nurses regarding the quality of nursing care.

• The purpose of this study was to investigate how individuals with chronic illnesses perceive the quality of nursing care in order to enhance the quality of care.

• The participants were 11 Icelandic individuals, aged 39–80 years with various chronic illnesses.

• Phenomenology was the research approach and in‐depth dialogues were used.

• Five themes emerged: nurses who provided high quality nursing care, the effects of high quality nursing care, the lack of good quality nursing care and its effects, ancillary factors, and the art of being a patient.

• Based on the findings I conclude that professional caring is the most important part of quality of care as perceived by individuals with chronic illnesses.
Effects of sponge bathing on vagal tone and behavioural responses in premature infants
Authors: LEE HAE‐KYUNG
Published: March 2003

• The purpose of this study was to evaluate the effects of sponge bathing on physiological (vagal tone, heart rate, heart period, oxygen saturation) and behavioural responses in newly born premature infants in the intensive care unit of a university hospital in South Korea.

• A convenience sample was taken of 40 infants who were between 27 and 36 weeks gestational age at birth and free of congenital defects.

• The infants' physiological parameters were recorded 10 min before, during and after bathing. To determine behavioural status, tools were modified from the instruments used in a previous study by Scafidi et al. (1990).

• Analysis of the results showed that the premature infants reacted to sponge bathing with decreases in vagal tone and heart period and increases in heart rate. Oxygen saturation did not demonstrate any remarkable alteration during bathing. Also, there were no significant differences in behavioural signs, motor activity and behavioural distress.

• Results of this study indicated that nurses in a neonatal intensive care unit should decide according to a premature infant's physiological state whether or not to give a sponge bath.
Parents' roles in using non‐pharmacological methods in their child's postoperative pain alleviation
Authors: PÖLKKI TARJA , VEHVILÄINEN‐JULKUNEN KATRI , PIETILÄ ANNA‐MAIJA
Published: March 2003

• Increasingly nowadays, parents participate more fully in the care of their hospitalized children.

• The purpose of this study was to describe parents' utilization of selected non‐pharmacological methods in relieving their hospitalized child's (aged 8–12 years) postoperative pain, and factors related to this function.

• Data were collected by a questionnaire survey completed by parents (n=192) with a child hospitalized on a paediatric surgical ward in the five university hospitals of Finland. The response rate was 90%.

• Results indicated that non‐pharmacological methods, such as emotional support and helping with daily activities, were well utilized whereas cognitive‐behavioural and physical methods were less frequently used strategies.

• Certain background factors specific to the parents and their hospitalized children were significantly related to the non‐pharmacological methods used by the parents. The hospitalized child's gender, the time of the surgical procedure, and the parents' assessments of their child's pain intensity, were especially significantly related to many of these strategies.

• The findings of this study could be used in clinical practice to improve guidance provided to parents regarding interventions for children's pain relief.
The role of community staff in care home placement in Sweden
Authors: SANDBERG J. , NOLAN M. R. , LUNDH U.
Published: March 2003

• The role of community staff in placing a relative in a care home is a relatively unexplored area of practice.

• Interviews with a variety of community staff in Sweden suggest that they play a significant role in helping family carers, particularly spouses, research the decision about the need for placement.

• This role can include recognition that placement is required (seeing the need), initiating and sustaining discussions about placement (sowing the seed and nurturing the seed) and legitimating the decision.

• However, once the decision has been made relatively little attention is given to the emotional consequences of the move and attention is focused largely on instrumental aspects.

• Despite showing sensitivity in the decision‐making phase, community staff could do more to help carers deal with the guilt they experience and to initiate contact with the care home.
The transition of adolescents with diabetes from the children's health care service into the adult health care service: a review of the literature
Authors: FLEMING ELIZABETH , CARTER BERNIE , GILLIBRAND WARREN
Published: March 2003

• Adolescents with diabetes have unique health needs, which impact upon their transition from children's health care services into adult health care services.

• These health needs result from the precarious period in their lives, when they have to cope with the stresses of being a maturing person. This coincides with their move from the children's into the adult health care service. Whilst coping with these pressures they must also keep their diabetes under control.

• The impact of emotional and physical demands upon the adolescent means that they are more susceptible to non‐adherence, which may result in reduced diabetic control.

• This literature review identifies some of the many barriers erected to the transition into the adult health care system; these barriers may be constructed by any one of the parties involved: the children's health care team, adult health care team, the adolescent or their family.

• Principles of a successful transition are explored, along with the prerequisite qualities required of health care providers and the health care service.
A pain workshop: an approach to eliciting the views of young people with chronic pain
Authors: CARTER BERNIE , LAMBRENOS KARINA , THURSFIELD JONATHAN
Published: March 2003

•  Chronic pain is complex and there is still much to discover about the burden that it places on children and their families.

•  The aim of this study was to explore the way in which the experience of chronic pain impacts on the lives of young people.

•  Through the use of a pain workshop that involved a series of guided activities and a focus group, young people were able to share their experiences with each other and the facilitators/researchers.

•  Data were analysed using a theoretical coding technique supported by Atlas.ti®.

•  Five key interlinked themes emerged from the data and each theme is expressed in the words of the young people themselves: `no one's pain's the same', `getting on with it', `it's hard 'cos…', `keeping with the dream', and `it depends … some are OK'.

•  The young people did experience significant disruption in their lives as a result of their pain.

•  Pain was experienced as if it was both a separate entity as well as an intrinsic part of them and, to a degree, blighted their future.

•  Based on the experiences shared by the young people, professionals need to develop insight and strategies into the challenges young people with chronic pain face on a daily basis.
Computer‐assisted learning of Chinese idioms
Authors: Lewis R. , Luk R.W.P. , Ng A.B.Y.
Published: March 2003

Abstract Chinese idioms play an important role in Chinese vocabulary learning as well as having cultural and social functions. However, researchers found that Hong Kong students seldom use idioms. Not only are students writing characters incorrectly, they are using the idioms both incorrectly and inappropriately. A survey was conducted to examine the attitudes of Hong Kong students and teachers to learning Chinese idioms. According to the survey, primary teachers believed that computers can assist students in learning Chinese idioms more effectively than an idiom dictionary. Consequently, an experimental program for learning Chinese idioms was designed for students between 9 and 11 years old. As an evaluation, usability tests were carried out by interview and by survey. Both evaluations produced positive responses from the dependent and independent group of subjects which is an encouraging first step.
Learning how to learn using a virtual learning environment for philosophy
Authors: Gibbs G. R.
Published: March 2003

Many students find theoretical subjects hard and challenging. Although they may pass modules in the subject, they often fail to attain a deeper, conceptual understanding. coMentor, a virtual learning environment on the WWW was developed to support such conceptual subjects by providing facilities for debate, discussion, groupwork, resource sharing and vicarious learning. The system was evaluated with undergraduates taking a philosophy module. Although there was no unequivocal evidence of gains in final assessment in those using the system, there was evidence of other forms of learning. Students learned from seeing each other's work, from having to ‘write’ down their ideas and share them with others and they adopted learning styles that were beneficial to learning a theoretical subject matter. Using a Learning Styles Inventory Scale, those using coMentor showed higher levels of deep learning and significantly higher levels of strategic learning than those who used the system little.
Design and use of a hypermedia system at the University level
Authors: Collaud G. , Gurtner J‐L. , Coen P‐F.
Published: March 2003

Abstract This paper reports on an experiment in which a whole semester course in psychology was replaced by a mixed formula consisting of a CD‐ROM complemented by a series of seminars and workshops. The CD‐ROM was conceived as a collection of documents (hypertexts, research data, references, videos and activities) linked together with genuine Netscape facilities. Students were invited to search through these documents for information to answer questions (called challenges) on the topic. A multiple‐choice questionnaire accompanied each challenge in order to foster students' self‐evaluation. The seminars, held every other week, served both as forums to discuss each of the topics under the guidance of an expert. Careful analysis of students' answers to two questionnaires at the beginning and end of the course and during interviews, showed that such a formula was favourably accepted by a large majority of students, although it lead to more anxiety and work load than a traditional course. Positive effects were also observed on learning.
E‐commerce: consumer protection issues and implications for research and education
Authors: Goldsmith Elizabeth , McGregor Sue L.T.
Published: March 2003

The impact of e‐commerce on consumers, public policy, business and education is examined. It behoves academics and students alike to keep abreast of new developments in this field and to contribute to the public debate on the widespread effects of e‐commerce. A discussion of public policy initiatives, research questions and ideas for future research are given.
Gender modification and resource allocation in subdioecious Wurmbea dioica (Colchicaceae)
Authors: Barrett Spencer C. H. , Case Andrea L. , Peters Gregory B.
Published: March 2003

1 Populations of subdioecious species contain female, male and cosexual plants. Here we investigate factors influencing gender expression and patterns of resource allocation among the sex phenotypes in subdioecious populations of the diminutive geophyte Wurmbea dioica (Colchicaceae) from the Australian Capital Territory, south‐east Australia.

2 Demographic studies and population comparisons of the sex phenotypes were conducted to determine their distinguishing features, and whether sex expression was labile. Comparisons of biomass allocation were made to assess whether plants with hermaphrodite flowers were larger than unisexual plants. The seed fertilities of sex phenotypes were measured and related to the sex ratio of populations.

3 Female plants exhibited canalized gender producing only ovuliferous flowers, which were smaller and less showy compared to flowers of other plants. Some male plants displayed labile gender expression, producing varying numbers of male and hermaphrodite flowers (fruiting males). Maternal investment among male plants was size‐dependent.

4 Fruiting males were significantly larger and produced more flowers than unisexual plants. At flowering, we found no evidence for changes in proportional allocation with increases in size after controlling for total biomass. At fruiting, allocation patterns differed between females and fruiting males independently of size.

5 Total seed output by fruiting males was 70% of that produced by females. The number of seeds per fruit declined acropetally in both sexes, and males produced, on average, more seeds per fruit than females. Data on the relation between female frequency and the relative seed fertilities of males and females gave a poor fit to Lloyd's (1976) genetic model predicting equilibrium female frequency. The lack of congruence probably occurs because size‐dependent gender modification in males complicates the assumptions of the model.
The significance of assemblage‐level thinning for species richness
Authors: Stevens M. Henry H. , Carson Walter P.
Published: March 2003

1 A unimodal relationship between species richness and primary productivity is commonly reported. To explain this pattern, the mechanisms proposed in the many hypotheses are generally complex and almost all are without a strong empirical foundation. Here we evaluate the role of self‐thinning in plant assemblages: assemblage‐level thinning.

2 We developed a simple two‐parameter model of species richness that predicts that plant species richness will be determined by a unimodal relationship between total plant density and above‐ground biomass. This model provides a very narrowly defined set of testable quantitative predictions, and thus is the first falsifiable model of assemblage‐level thinning. We fit this model to the species richness–above‐ground biomass data from 14 empirical studies that are often cited as evidence of a general diversity–productivity relationship. In addition, we compared our model to two other models, one more flexible and one more constrained than our own.

3 We found that our model of species richness explained a substantial and statistically significant portion of the species richness observed in 11 of the 14 empirical studies of species richness–biomass patterns. Therefore, given the conservative nature of our model, and the number of previously published data sets explained by this model, we argue that assemblage‐level thinning not only provides a viable and exceedingly parsimonious explanation, but may also be a widespread phenomenon.
Disturbance‐related heterogeneity in the seed banks of a marine angiosperm
Authors: Inglis Graeme J.
Published: March 2003

1 Patterns in the distribution of seeds of the marine angiosperm Halodule uninervis were described over spatial scales ranging from a few centimetres to meadows separated by more than 120 km along the north‐eastern coast of Queensland, Australia. Separate surveys examined how seed bank densities were related to: (i) the distribution of male and female plants (primary dispersal) and (ii) disturbances caused by turbulent water movement and the foraging of large marine vertebrates.

2 The distribution of seeds was extremely heterogeneous at very small scales of sampling (centimetres to tens of centimetres). Variation in seed abundance within individual meadows (87% of total variation in seed densities) was at least an order of magnitude greater than that among separate intertidal populations (13%). Densities of seeds were greatest in micro‐topographic depressions where the overlying vegetation had been removed by directional water currents and the feeding activities of dugongs. Smaller disturbances that did not disrupt the cover of vegetation had no effect on seed abundance. Detailed mapping of the distributions of seeds and male and female reproductive shoots showed only a weak relationship between primary seed production and the seed bank, but revealed a pattern of seed distribution that was consistent with accumulation in linear depressions in the meadow.

3 The seed banks of intertidal sediments exhibit many similarities to those of physically dynamic desert sands. In these unstable environments, seeds are most abundant in sheltered micro‐habitats where sediment mobility is impeded. Plants that inhabit desert and marine sands appear to have responded similarly to strong selective pressures on seedling recruitment by developing mechanisms that restrict primary seed dispersal to take advantage of micro‐sites provided by established plants.
Restriction of the upper distribution of New England cobble beach plants by wave‐related disturbance
Authors: Kennedy Coleman W. , Bruno John F.
Published: March 2003

1 The New England cobble beach plant community is an intertidal assemblage of halophytic forbs found exclusively behind fringing beds of the grass Spartina alterniflora. The purpose of this study was to determine the life stage and factors that limit the upper (landward) distribution of cobble beach plants in Narragansett Bay, Rhode Island, USA.

2 Seed traps and soil samples above the community border contained large numbers of seeds and buried seedlings of three cobble beach species, indicating that seed supply and germination do not limit vertical plant distribution. Experimentally added seeds of four species germinated above the community border, but seedlings did not emerge suggesting that seedling emergence is the proximate life stage limiting population and community distribution.

3 Measures of wave disturbance (cobble movement and change in cobble depth) indicated that substrate instability is substantially greater above than within the community, probably due to the lack of buffering by the S. alterniflora bed at higher tidal heights.

4 A second seed addition experiment demonstrated that seedlings of Suaeda linearis, a common cobble beach forb, are only able to emerge and grow into reproductive adults above the community border when the substrate there is artificially stabilized. Seedling transplants and glasshouse manipulations demonstrated that neither herbivores nor soil quality limited seedling emergence.

5 Overall, the vertical restriction of habitat modification by S. alterniflora appears to result in substrate instability at higher tidal elevations sufficient to prevent seedling emergence and limit the vertical distribution of cobble beach plants.
The effects of light quality, nitrate concentration and presence of bracteoles on germination of different fruit types in the heterocarpous Atriplex sagittata
Authors: Mandák Bohumil , Pyšek Petr
Published: March 2003

We investigated the effect of light quality, nitrogen supply, fruit size and age on germination of the three types of fruit produced by Atriplex sagittata.

 Regardless of fruit type, seed germination was significantly reduced in the dark. Light quality had no significant effect on germination of seeds from fruit types A and B, both of which are dormant, but seeds from fruit type C, which are non‐dormant, germinated better in green light (low photon flux and red : far‐red ratio, simulating conditions in the canopy) than in white light.

 Optimum nitrate concentration differed between seed types but, for all, germination was reduced at the highest concentration used.

 The effects of cold stratification and its interaction with light and nitrogen effects were also studied. Strong interactions between stratification and light were found in all seed types but other interactions were less frequent.

 Three size classes of type C fruit showed similar final germination percentages but large seeds germinated more slowly.

 The effect of seed age was highly significant: over a 3 year period, the germinability of dormant seeds (types A + B) increased while that of non‐dormant seeds (type C) fell.

 The salt concentration in bracteoles of freshly ripened fruits was too low to mediate an inhibitory effect on germination. Moreover, the first autumn rain would be sufficient to remove all the salt from bracteoles.

 Differences between fruit types in depth of dormancy, and in response to the quality of light and to nitrate concentration in the soil, allows A. sagittata to respond to the spatial and temporal variation in environmental conditions encountered by this annual of disturbed habitats.
Demographic variation and population viability in Gentianella campestris: effects of grassland management and environmental stochasticity
Authors: Lennartsson Tommy , Oostermeijer J. Gerard B.
Published: March 2003

Transition matrix models were used to evaluate the effects of environmental stochasticity and four different methods of grassland management on dynamics and viability of a population of the biennial Gentianella campestris (Gentianaceae) in species‐rich grassland. Data were collected between 1990 and 1995.

 Continuous summer grazing, the prevailing management strategy in Scandinavian grasslands, resulted in high recruitment of new plants, mainly because litter accumulation was prevented and gaps were created by trampling. Trampling and repeated grazing, however, caused damage which reduced seed production. Lambda for the average matrix was c. 0.77, and a stochastic matrix model yielded an extinction probability for the total population of c. 0.08 within 50 years.

 Mowing in mid‐July (used as a conservation tool) increased seed production, but litter accumulation following re‐growth of the vegetation prevented establishment. Lambda and extinction risk were similar to continuous grazing.

 Mowing in October (another conservation tool) promoted recruitment because of low litter accumulation, but the seed output decreased because plant growth was impaired by tall vegetation. Lambda was 0.64, while the extinction probability was very high (c. 0.98 within 50 years).

 Mid‐July mowing followed by autumn grazing (the historical management regime) yielded high values for both seed production and establishment of rosettes. Lambda was 0.94 and the probability of extinction within 50 years was below detection level.

 Log‐linear analysis showed that the matrices differed significantly both between treatments and between years. The latter indicates environmental stochasticity, here caused by summer drought that increased the extinction risk. Lambda may be slightly underestimated because drought occurred in one out of five summers during the study period, which is high compared with the natural frequency.

 We conclude that traditional grassland management is more favourable for G. campestris than the methods that prevail in Scandinavia today. This indicates a serious conservation problem, because grazing has replaced traditional management in many of the remaining semi‐natural grasslands throughout Europe.
Patterns of fruit production in the subdioecious plant Astilbe biternata (Saxifragaceae)
Authors: Olson Matthew S.
Published: March 2003

Patterns of fruit production in the subdioecious plant Astilbe biternata were used to test whether sex ratio is correlated with relative fruit production by females and males; whether males that produce large inflorescences also produce proportionally more fruit; whether male fruit production is correlated with habitat type; and whether pollen limitation could affect fruiting.

 Inflorescence length, a good predictor for flower production, was surveyed along with percentage fruit production and sex ratio in 22 populations from throughout the species range, including eight populations where plants were growing in both roadside and understorey habitats. In one population, the percentage fruit production of males and females was assessed in relation to the distance from to the nearest pollen source.

 There was significant variation in sex ratios among populations, but this was not correlated with relative (female:male) total fruit production. Fruiting males produced smaller inflorescences than either females or non‐fruiting males, and within fruiting males, individuals with large inflorescences produced proportionally fewer fruits than those with small inflorescences. The proportion of males that produced fruit was higher in roadside than understorey habitats whereas all females produced fruit in both habitats. Female, but not male, percentage fruit production decreased with distance from the nearest potential pollen source.

 Allocation patterns to fruiting differed between males and females. Percentage fruit production declined as inflorescence size increased for both males and females. Astilbe biternata males with a genetic propensity to produce fruit might produce smaller inflorescences, or fruit production might be determined by resource availability within the inflorescence after the inflorescence is produced.
Vernalization requirement of wild beet Beta vulgaris ssp. maritima: among population variation and its adaptive significance
Authors: Boudry Pierre , Mccombie Helen , Van Dijk Henk
Published: March 2003

Seven populations of Beta vulgaris ssp. maritima (wild beet) situated along a latitudinal cline were studied for their vernalization requirement and its consequences for fitness.

Various cold regimes were applied in glasshouses and experimental gardens with plants of different ages. Three additional experimental sites (on the French Mediterranean, Atlantic and North Sea coasts) situated near three of the sampled populations, and thus including a reciprocal transplant design, were used to evaluate the influence of latitude under natural conditions. Survival and plant size were measured over 3 years.

The vernalization requirement was greater in plants from more northern origins. The level of cold required to allow flowering overcompensated for the colder springs, so that northern plants in northern sites flowered less than southern plants in southern sites.

Young seedlings were more difficult to vernalize than plants that had already developed vegetative rosettes.

Differences in vernalization requirement seem to be an adaptive response to spring temperatures and season length in a particular latitude. A whole winter vernalization almost always led to flowering in the subsequent year whatever the latitude or geographical origin.

Plants from the Atlantic and Channel coasts showed the highest lifetime reproductive success at all sites. Southern populations were better adapted to disturbed habitats as shown by their higher first‐year reproductive success. The North Sea population had a lower reproductive success than the Atlantic populations, even in its native environment.
Density‐dependent regulation in an invasive seaweed: responses at plant and modular levels
Authors: Arenas Francisco , Viejo Rosa M. , Fernández Consolación
Published: March 2003

The effects of density on the vital rates, growth form and population size structure of the invasive seaweed Sargassum muticum (Yendo) Fensholt were evaluated experimentally.

The initial difference in plant number between the highest and the lowest density (200 and 6400 plants m−2) was considerably reduced by the end of the experiment. Surprisingly, this was mostly due to numbers increasing at lower densities, probably because microscopic forms were not removed during the experimental thinning.

The allometric length–dry mass relationship fitted a simple linear model on log‐log scale for both the highest and the lowest densities, but had different slopes. At higher densities plants became taller and thinner as a consequence of variations in the production and growth of modules.

Mean size (dry mass) and the development of size hierarchies of plants were affected by both the addition of further (microscopic) recruits and asymmetrical competition among plants. Plant length distributions were also influenced by changes in the growth form of plants. The length hierarchies of main branches also suggested the presence of asymmetrical competition at this modular level.

Density influenced both mean size and morphology of the plants and thus induced changes in reproduction. The negative effect of density on individual plant size reduced the percentage of fertile plants and possibly their annual reproductive allocation, but these effects may be attenuated by morphological responses.

The responses of S. muticum to crowding are closely linked to its ability to colonize bare space. The massive reproductive output and very limited dispersal range account for local and dense recruitment patterns. Our results suggest that the responses of S. muticum to crowding allow the establishment of dense populations with high persistence and resistance to colonization by other species.
The synchronized and intermittent reproduction of forest trees is mediated by the Moran effect, only in association with pollen coupling
Authors: Satake Akiko , Iwasa Yoh
Published: March 2003

Coupled map models for the dynamics of individuals’ energy reserves have shown that large between‐year fluctuation in tree seed crops can occur in a constant environment and that reproduction can be synchronized over the whole forest if fruit production is limited by the availability of outcross pollen.

In this paper we examine the effects of the environmental fluctuation experienced by different individuals. The reactive changes in annual productivity and the reproductive threshold are accounted for by an additional term in the energy reserve dynamics.

If individuals show chaotic seed production, strongly correlated environmental fluctuations (the Moran effect) failed to produce a high positive correlation in seed production across the forest in the absence of pollen limitation. Regardless of the high nonlinearity of resource dynamics, a large correlation was maintained when both pollen limitation and correlated environmental fluctuation occurred.

We derived a regression formula for the degree of synchronization when pollen coupling occurred only on a local scale. The correlation coefficient of seed crops between distantly located individuals decreases with the resource depletion coefficient, but it increases with the strength of pollen limitation, the standard deviation of environmental noise, and the correlation of environmental noise between different trees.