bluuebunny/crossref_metadata_2025 huggingface dataset:
Benthic diatoms in USA rivers: distributions along spatial and environmental gradients
Authors: Potapova Marina G. , Charles Donald F.
Published: March 2003

Aim

To study large‐scale patterns of benthic diatom assemblages in rivers, to assess the relative importance of environmental and geographical factors affecting their composition, and to evaluate the implications of these patterns for the use of diatoms as indicators of water quality, particularly nutrient enrichment.

Location

The United States Geological Survey (USGS) National Water Quality Assessment (NAWQA) Programme data set covers the conterminous United States.

Methods

We employed gradient analysis to understand the floristic structure of the data set and to discover major ecological gradients underlying variation in species composition at different spatial scales (entire US, Omernik Level 1 and Level 2 ecoregions). We used variance partitioning to separate the effect of environmental and spatial characteristics.

Results

At the national scale, three major ecological gradients were evident. The first was a complex `downstream' gradient from fast‐flowing, mostly oligotrophic, highland rivers to predominantly eutrophic rivers of high‐ and low‐elevation plains. The second was a gradient integrating water mineral content and pH, which separated the soft and often more acidic waters of the humid eastern part of US from the alkaline waters of arid western regions. The third obvious gradient was related to latitudinal and altitudinal variation of temperature. Up to one‐third of the total explainable variation in species data was attributed solely to geographical factors not correlated with measured environmental characteristics. We present several examples of species with complex patterns of spatial distribution.

Main conclusions

Although environment consistently plays the most important role in structuring diatom assemblages in rivers, spatial factors also explain some variation in diatom distribution, especially at the continental scale. Most of the species that are confined to limited geographical areas are not yet described and await future taxonomic work. We show that selection of species which could serve as indicators of nutrient enrichment in US rivers is not a straightforward procedure. The existence of complex environmental gradients, and still poorly understood spatial patterns of species distribution, precludes attempts to develop uniform diatom‐based metrics that would be applicable everywhere in the US. We advocate the development and calibration of metrics based on data sets collected from more limited geographical areas, and that include sites having relatively narrow ranges of environmental characteristics other than that which the metrics are designed to indicate.
Population dynamics of reintroduced forest birds on New Zealand islands
Authors: Armstrong Doug P. , Davidson R. Scott , Dimond Wendy J. , Perrott John K. , Castro Isabel , Ewen John G. , Griffiths Richard , Taylor Jason
Published: March 2003

Aim

We studied dynamics of four populations of New Zealand forest birds for 5–9 years after reintroduction to islands. We primarily aimed to predict whether these populations were viable, and what, if any, management was needed to maintain them. However, the small scale of these islands also provided an opportunity to study density‐dependent population growth over a short time frame.

Location

We studied New Zealand robin (toutouwai,Petroica australis) and stitchbird (hihi,Notiomystis cincta) populations reintroduced to Tiritiri Matangi, a 220‐ha offshore island near Auckland, and saddleback (tieke,Philesturnus carunculatus) and stitchbird populations reintroduced to Mokoia, a 135‐ha island in Lake Rotorua. These islands are free of mammalian predators, but have highly modified habitat following clearing and regeneration.

Methods

We closely monitored each population, individually marking all or most of the birds and in some cases experimentally manipulated population density or food supply. We used model selection procedures to understand factors affecting survival, fecundity and dispersal, and developed stochastic simulation models.

Results

The Tiritiri Matangi robin and Mokoia saddleback populations grew without management and appear to be viable. Both showed strong evidence of density‐dependent growth, with fecundity (saddlebacks) and juvenile survival (both populations) declining with increasing density. Neither stitchbird population appears viable without management and supplementation experiments showed reproduction and/or survival to be limited by food supply. The Tiritiri Matangi population appears viable as long as supplementary feeding continues. However, the Mokoia population has a high mortality rate regardless of supplementary feeding, resulting in tenuous viability even with intensive management. Mokoia stitchbirds suffer from infection byAspergillus fumigatus, a pathogenic fungus that is prevalent in highly modified habitats and more abundant on Mokoia than Tiritiri Matangi.

Main conclusions

Some forest birds can thrive in regenerating forest on islands and strong evidence of density dependence can be detected in such populations in as little as 5 years. This allows density‐dependent models to be developed, providing guidance when island populations are harvested for further translocations. Other species are limited by food supply in regenerating environments, a problem potentially overcome by management. However, prevalence ofA. fumigatusmay render highly modified environments uninhabitable by some species regardless of management.
Male‐biased sex ratio in a small tuatara population
Authors: Nelson Nicola J. , Keall Susan N. , Pledger Shirley , Daugherty Charles H.
Published: March 2003

Aim

We estimated population size, survival, longevity and sex ratio of tuatara (Sphenodon guntheri Buller 1877) on North Brother Island and determined whether recruitment was occurring, to aid management and identify potential problems for population viability.

Location

This study was conducted on North Brother Island, Cook Strait, New Zealand. This 4‐ha island supports the sole remnant population of S. guntheri.

Methods

Demographic variables were estimated using capture–recapture methods. Tuatara were individually marked and recaptured during twelve trips, spanning a decade. Population size was estimated for selected trips using the CAPTURE package and finite mixture models, and survival was analysed using the Jolly–Seber (J–S) model. Longevity was estimated using tuatara individually marked in 1957.

Results

Approximately 350 adult tuatara profile likelihood interval (PLI) (294–427) inhabit North Brother Island, and the sex ratio is strongly biased towards males (1.7M : 1F). Annual adult survivorship is high (0.95) for both sexes and some tuatara live for at least 61 years.

Main conclusions

The small size and biased sex ratio of this population may make it susceptible to demographic stochasticity, Allee effects, and/or loss of genetic variation. Harvesting for translocation could exacerbate such problems. In addition, tuatara have temperature‐dependent sex determination (TSD), with males produced at higher incubation temperatures. Global warming may therefore skew the sex ratio further unless female nest site choice or adaptive shifts in pivotal temperatures compensate for rising temperatures.
On the distributional patterns of Southeast‐East Asian freshwater fish and their history
Authors: Yap S. Y.
Published: March 2003

Abstract Aim  The extensively published data on Southeast‐East Asian freshwater fish communities and distributions were compiled and expressed into phenograms.

Location  River basins of Southeast China, the Indochinese Peninsula and Sundaland were studied and compared for possible lineages.

Methods  The Hennig86 program was employed to cluster the basins of the various subregions on the basis of their similarity in fish assemblages. In this cluster analysis, the outgroup comparison method was used, in which a reference was based on which to make corrections for unequal rates of evolution among the lineages.

Results  South‐eastern China, the Indochinese Peninsula and Sundaland are groups of landmass that share a common ancestor and that evolved at distinct epochs and through different geological processes, as shown from the association between the distribution of freshwater fish of Southeast‐East Asia and the twenty‐one river basins they inhabit.

Main conclusions  Southeast‐East Asia comprises an estimated 3500 cyprinid species. The phenograms obtained, based on their compositional and distributional patterns, suggest that the riverine fish communities of the area studied fall into nineteen biogeographical zones defined by the main river systems and their underlying geology.
The experience of early miscarriage from a male perspective
Authors: Murphy Fiona A.
Published: March 2003

• In the literature there is increasing awareness of the psychological consequences of early miscarriage for women.

• However, there is little on the feelings, needs and experiences of men whose partner has had an early miscarriage.

• This paper aims to describe the experience of early miscarriage from a male perspective using a phenomenological approach.

• Seven categories related to the experience of early miscarriage are discussed: Feelings, Loss, Characteristics and differences between men and women, Staff action and attitudes, What to do?, Coping and Time.

• Based on an awareness of the needs of both partners, it is suggested that nurses have a key role to play in delivering effective interventions after early miscarriage.
Family response to difficult hospitalizations: the phenomenon of `working through'
Authors: BUTTERY JOANNE , EADES MARGARET , FRISCH SARA , GIGUÈRE MONIQUE , MOUNTJOY ANITA
Published: March 2003

• This paper describes the process and outcomes of a project to learn about qualitative research methods.

• A small study of family participation in decision‐making was conducted with 7 family members who were interviewed after an inter‐unit patient transfer.

• The data analysis used strategies derived from grounded theory, family life‐cycle framework and storytelling.

• The interviews indicated respondents' concerns about the patient, their efforts to balance their lives during a time of disarray and their sorting through crises in their lives (`working through').

• `Working through' discourse has identifiable features, including: linking the past, present and future; refrains; rhetorical questions; and self‐talk.

• Clinicians should encourage the `working through' process by family during the hospitalization of a family member.
The implications of latex allergy in healthcare settings
Authors: BOWYER REBECCA V. ST. L.
Published: March 2003

• Latex allergy is on the increase.

• This paper focuses on how sensitization can occur and the use of latex gloves.

• Implications for the healthcare setting are addressed and recommendations made focusing on glove usage.
Women’s experiences of obtaining emergency contraception: a phenomenological study
Authors: Bell Tina , Millward Jennifer
Published: March 2003

• Emergency contraception (EC) has been available since 1984 but has been labelled the ‘best kept secret’ ( Winfield, 1995).

• Because EC was originally termed ‘the morning after pill’, many people interpreted this literally and missed an opportunity to use the method.

• More recent publicity has dropped this term and emphasized that the method is effective up to 72 h after unprotected intercourse or contraceptive failure ( Burton & Salvage, 1990).

• Uptake of EC has steadily increased since 1985 but there is still evidence that younger women in particular are least aware of its existence ( Zeibland & Maxwell, 1996).
Prevalence of urinary incontinence and its relationship with health status
Authors: Roe Brenda , Doll Helen
Published: March 2003

• A postal survey of two random samples of adult populations within two health authorities in the UK was undertaken during 1994. One health authority had an established continence advisory service (HA1) and the other one did not have a continence advisory service (HA2).

• A total of 12 529 patients (HA1, 6319; HA2, 6210) were mailed a structured questionnaire and 53% (n=6139) returned completed questionnaires.

• A point prevalence of current urinary incontinence of 9% (n=519, 95% CI, or confidence interval, from 7.9% to 9.3%) was found. A larger number of people within the populations had experienced urinary incontinence at some time during their adult years (23%, n=1427, 95% CI from 22.2% to 24.3%).

• People who were incontinent had a significantly lower health status than people who were continent (mean scores across all eight domains of the Short Form 36, SF36, P < 0.0001), indicative of greater health and social care needs.

• The prevalence of urinary incontinence in the adult populations of two communities indicates that it is a sizeable public health and primary healthcare issue.
The effects on patient well‐being of music listening as a nursing intervention: a review of the literature
Authors: Biley Francis C.
Published: March 2003

• A review of the therapeutic potential of music listening as a nursing intervention was performed.

• It revealed that evidence from a variety of fields and clinical specialities existed, including the use of music in critical care environments, surgical settings, dental surgery applications, mental healthcare, pain control, and generally for the control of anxiety and promotion of relaxation.

• Due to a number of reasons, including the variety of dependent variables that were measured and methodological issues such as the use of small sample sizes, it is difficult to form any firm conclusions.

• Tentatively, the research seems to indicate that there often appear to be positive changes in physiological variables measured, although these changes are not consistent, nor are they always statistically significant.

• More confidence can be placed in research that examines psychological variables, as a consistent positive impact on certain measures has been found.
Medication management and older patients: an individualized and systematic approach
Authors: Ryan Assumpta Ann , Chambers Mary
Published: March 2003

• The aim of this action research study was to evaluate the effectiveness of an individualized education programme on older patients’ knowledge of prescribed medication.

• A questionnaire for assessment of medication knowledge was used to collect data from 15 patients at two intervals, before and after an individualized education programme. Following the collection of pre‐intervention data, an individualized education programme was developed for each patient. As part of the education programme patients also had an opportunity to self‐administer their medication.

• The results of the study showed that all participants scored higher in the post‐test than the pre‐test although the degree of improvement varied between participants. Patient satisfaction with the education programme was also assessed and revealed a high level of satisfaction.

• The most significant finding was the importance of tailoring education programmes to meet the needs of the older person. This is borne out by case studies, which suggest that the most relevant characteristic of successful participants is a real desire to remain independent and in control of their medication.

• The findings question the value of standardized programmes of medication education that treat older people as a homogeneous population. The article concludes by emphasizing the need for nurses and other healthcare professionals to individualize their teaching and learning strategies to meet the needs of older patients.
Use of the Oucher Numeric and the Word Graphic Scale in children aged 9–14 years with post‐operative pain
Authors: Ramritu
Published: March 2003

• The construct validity and clinical applicability of two self‐report scales, the Oucher Numeric and the Word Graphic Scales, were examined in this study. Construct validity was tested on the assumption that pain declines following the administration of analgesia.

• Eighty‐one children aged between nine and 14 years with post‐operative pain used the two scales before and for each of the 4 hours following the administration of analgesia, to report their intensity of pain. The method used for testing construct validity was a replication of the study conducted by Aradine et al. (1988; Children’s pain perception before and after analgesia: a study of instrument construct validity and related issues. Journal of Pediatric Nursing 3 (1), 11–23) to test the construct validity of the Oucher Scale. Construct validity was supported for both the scales.

• Twenty‐eight nurses who administered the scales and the parents of 45 children who had observed their children use the scales, commented on the usefulness of the scales in assessment of pain during hospitalization.

• A majority of children and nurses preferred the Oucher Numeric, whereas the Word Graphic Scale was preferred by a majority of the parents.

• Preference of scale was based on its ease of use and whether the child preferred to use numbers or words to describe the intensity of pain.

• A majority of the children and nurses and all parents believed that a self‐report scale was useful for assessment and communication of children’s pain following surgery.
Nursing in the community – impact of context on the practice agenda
Authors: Carr Susan M.
Published: March 2003

• The agenda for health care detailed in recent policy statements has a strong community and primary health care focus.

• The impact of the community, and specifically the patient’s home, as a location for practising and learning to practise nursing, is an issue which has received limited exploration. Recent research suggests that the context influences the practice agenda in a number of ways.

• Highlighting the impact of working in the community context is timely in order that education providers, policy makers and managers are fully aware of the impact of moving care ‘closer to home’.
‘Brothers in arms’: how men with cancer experience a sense of comradeship through group intervention which combines physical activity with information relay
Authors: Adamsen L , Rasmussen J. Midtgaard , Pedersen L. Sønderby
Published: March 2003

• The study investigated how a group intervention programme (13 sessions over 16 weeks), designed for men with cancer (n=17), affected their sense of well‐being and had a positive impact on their ability to cope with the physical, psychological and social consequences of living with cancer. The close‐knit relationships fostered between participants stimulated a sense of solidarity and commitment amongst them.

• New thinking in relation to gender, group dynamics and social processes is presented, as are the implications for clinical nursing practice in cancer care. The experience from male orientated group intervention programmes shows that men with cancer have undiscovered strengths, whilst some wish to die ‘with their boots on’.
The hidden benefit: the supportive function of the nursing handover for qualified nurses caring for dying people in hospital
Authors: HOPKINSON JANE B.
Published: March 2003

• The nursing handover is a key activity for nurses working in acute hospital wards in the NHS. Little scholarly attention has been paid to the use nurses make of the information exchanged during nursing handover or how certain features of the nursing handover might impact positively or negatively on patient outcomes.

• This paper draws on data from a phenomenological study of 28 qualified diplomate nurses.

• During the course of non‐directive semi‐structured interviews, some of the participants in this study expressed the opinion that nursing handover was helpful in enabling them to work with dying people in the acute hospital medical wards in which they worked.

• The nurses identified two important functions of the nursing handover. The first was as a forum for discussing opinions and expressing feelings. The second was as a source of information on which to base their nursing decisions and actions.

• It is proposed that some qualified nurses need help with the emotional labour of caring for dying people and that the nursing handover can assist in emotional adaptation, so enabling the management of troubling thoughts or feelings experienced in the course of caring for someone who is dying.

• The role of the nursing handover in providing emotional support for nurses has been little studied and is a potentially useful area of future research, especially if it can be related to patient experiences and outcomes.
The nursing role in out‐patient child and adolescent mental health services
Authors: BALDWIN LAURENCE
Published: March 2003

• Whilst nurses in the UK have been working in out‐patient settings in the speciality of child, adolescent and family psychiatry for nearly 20 years, they are frequently unclear about what is their nursing contribution to the multidisciplinary team.

• This paper reports a qualitative study of perceptions of the nursing role in child and adolescent mental health teams of 11 clinicians from six different clinics.

• Whilst other disciplines were each able to define what was unique about their role, there was found to be no consensus as to what nurses brought by virtue of their nursing background.

• There is a risk that if nurses cannot develop a clearer rationale for their role, or be better able to articulate what they do in these teams, that role might be lost.
Adaptation and negotiation as an approach to care in paediatric diabetes specialist nursing practice: a critical review
Authors: MARSHALL MARIE , FLEMING ELIZABETH , GILLIBRAND WARREN , CARTER BERNIE
Published: March 2003

• Considerable attention has been given to diabetes care in children. However, nursing practice may be guided by biomedical models.

• Diabetes care in children should focus on family‐centred approaches arguably based in the community.

• Psychosocial constructs have an important role in the development of self‐management of chronic illness in children.

• Paediatric diabetes nurse specialists are pivotal in facilitating family‐centred care based on personal models of child and family interventions.
Mental health nurses: changing practice?
Authors: Tingle Alison
Published: March 2003

• Project 2000 envisaged that the nurse practitioner of the future should act as an ‘agent for change’, using research evidence to address those aspects of practice deemed detrimental to patient care.

• A Department of Health funded study investigating the careers of nurse diplomates provides information on the extent to which newly qualified nurses were able to change aspects of practice, what factors inhibited changes and which personnel played a key role in facilitating change.

• Key factors which inhibited newly qualified nurses acting as change agents were lack of experience and confidence, as well as attitudes of other members of staff.

• Staff of a higher grade, immediate line managers and healthcare assistants all played a key role in facilitating change.
Estimation of energy intake in clinical practice: a comparison between a food record protocol and a precoded food record book
Authors: Lorefält Birgitta , Unosson Mitra
Published: March 2003

• The aim of this study was to compare energy intake estimated from a clinical food record protocol (CFRP) with that from a precoded food record book (PFRB) as reference method.

• Food and fluid consumption were recorded in 10 older patients using a CFRP in parallel with a PFRB during a 6‐day period.

• The results showed that there were no significant differences in mean energy intake estimated from the CFRP as compared with that estimated from the PFRB. The correlation coefficient between the calculated daily energy intake from the CFRP and PFRB was 0.96.

• The differences in energy intake (kcal/day) between the CFRP and PFRB, plotted against their mean value for 10 patients, showed that results were within the limits of agreement (mean ± 2SD) for nine patients. The differences in each day's energy intake between the two methods plotted against their mean value showed that 97% of the estimated daily energy intake was within the limits of agreement. The weighted kappa between the two methods was 0.76.

• The CFRP would seem to be acceptable for the estimation of mean energy intake in the hospital setting.
Educating nurses about pain management: the way forward
Authors: Twycross Alison
Published: March 2003

? Nurse education does not appear to be preparing nurses to manage pain in the clinical area.

? A number of studies have demonstrated that nurses continue to have educational deficits in this context.

? Several studies have found no change in knowledge or behaviours following education about pain management.

? Others have found that changes in behaviour do occur.

? It is possible that innovative teaching strategies need to be used.

? The literature in this area is reviewed and recommendations made.
Simulation as a home learning environment — students’ views
Authors: Ronen M. , Eliahu M.
Published: March 2003

This paper describes a pilot study aimed at exploring the possibility of introducing simulation‐based homework into science learning, in the present junior‐high school setting. Two 9th grade classes have performed simulation‐based homework assignments as part of the study of electrical circuits, during two months. Students’ views about this activity were analyzed in relation to their prior computer experience and their achievement. The findings reveal that most students favour using the simulation as a home learning environment and find it more interesting and effective than the other homework activities. Students realise the potential of a simulation as a source of constructive feedback that enables them to take more responsibility on their learning.
Learning and teaching in a synchronous collaborative environment
Authors: Marjanovic O.
Published: March 2003

Despite obvious domination of asynchronous collaborative technologies, especially for virtual classrooms and distance education, the work presented in this paper is based on the assumption that some students will still prefer the experience of on‐campus, face‐to‐face collaborative learning. For those students a new synchronous collaborative environment is created by combining an innovative methodology for ‘same‐time, same‐place’ interactive learning and the technology called Group Support Systems which is designed to provide not only communication but rather computer‐mediated collaboration. This paper introduces this learning methodology and illustrates its potential to improve critical thinking, problem solving and communication skills of all students who are stimulated to participate as equal learners. It also describes how teachers are transformed from ‘information delivery specialists’ to guides and facilitators of learning.
Simulation — a bridge between theory and reality: the case of electric circuits
Authors: Ronen M. , Eliahu M.
Published: March 2003

Abstract This study aimed to examine the role of a simulation as a potential aid that may help students bridge the gap between theory and reality, in the case of electric circuits. Sixty‐three pairs of students aged about 15 years were presented with two tasks involving real circuits. An open simulation environment was available as an optional aid for the experimental group. Significant differences were found between the achievements of the groups. The use of the simulation contributed to students' confidence and enhanced their motivation to stay on‐task. The detailed analysis revealed the role of the simulation as a source of constructive feedback, helping students identify and correct their miscon‐ceptions and cope with the common difficulties of relating formal representations to real circuits and vice versa.
Consumer education and the OECD electronic commerce consumer protection guidelines
Authors: McGregor Sue L.T.
Published: March 2003

This paper explores the implications of e‐commerce transactions and the lack of consumer protection regulation on consumer educators and curricula. The discussion is divided into five sections: conceptualizing e‐commerce; the juggernaut of e‐commerce; consumer education defined, especially consumer protection in the electronic market‐place; the Organization for Economic Co‐operation and Development (OECD) 1998 Ottawa conference on electronic commerce; and the implications of this fluid market and policy context on consumer educators. Empowerment of the consumer, the ultimate objective of consumer education, is a total challenge in the global electronic market‐place, but a challenge that must be embraced by staying informed, becoming a consumer advocate, as well as educator, and remaining ever vigilant as curricula are developed for the domestic consumer transacting in an electronic global market.
Competitive exclusion of Elymus athericus from a high‐stress habitat in a European salt marsh
Authors: Bockelmann Anna‐Christina , Neuhaus Reimert
Published: March 2003

1 Zonation is often seen in environments with a strong physico‐chemical gradient, such as salt marshes. It has been hypothesized that plant species are limited in their distribution by abiotic factors towards the more extreme end of the gradient, and by competition towards the more favourable end. Invasion of the native clonal grass genus Elymus in many Wadden Sea marshes may be due to increasing atmospheric nitrogen input into a nitrogen‐limited environment. However, at Thmlauer Bay, Germany, Elymus athericus does not occur in lower salt marsh communities that are dominated by a dwarf shrub (Atriplex portulacoides). We therefore hypothesized that at this site the downslope (= more extreme) distributional boundary of E. athericus is a result of competition with A. portulacoides rather than of physiological limits.

2 A factorial experiment was set up to investigate the effects of removal of each competitor and fertilization. The reciprocal effects of the species on each other were measured in terms of vegetation cover and above‐ground biomass. The impact of the tidal regime on plant zonation was investigated by calculating inundation frequencies at the boundary between the two plant populations from water level recordings.

3 Elymus athericus extended its distribution into the lower salt marsh when A. portulacoides was removed. The latter increased in cover but not in biomass after the removal of E. athericus. Neither species showed a response to nitrogen fertilization. The boundary between the two species in the control plots varied considerably in elevation and inundation frequency.

4 The lower distributional boundary of E. athericus can be interpreted as the result of competition with A. portulacoides. Improvement of nitrogen availability in concentrations of the same order of magnitude as annual atmospheric input had no detectable effect on plant zonation and growth. Elevation and inundation frequency were not strictly correlated with plant zonation.
A method for analysing spatio‐temporal pattern in plant establishment, tested on a Populus balsamifera clone
Authors: Little L. R. , Dale M. R. T.
Published: March 2003

1 Ecological patterns in space and time have been well documented using interval variables such as plant density. In this paper, we use join Page: 1Is the text OK: join count statistics to examine spatio‐temporal patterns in a binary variable, plant establishment.

2 Establishment along a belt transect is represented as a grid or lattice in which each cell denotes a particular quadrat in a particular year. A cell is ‘black’ if a plant established at that particular time and place; otherwise it is ‘white’.

3 Each pair of black cells is connected by a ‘join’ that represents the association between stems established at two different places and times. Join ‘length’ is the pair of factors (s,t) that describes the distance between stems in space and in time, respectively. Spatio‐temporal pattern is detected by comparing the number of joins of each ‘length’ in a particular lattice with the expected number calculated from lattices generated by three different random models. Colonization rates can be estimated if there are particular join classes that occur more frequently than expected.

4 Artificially generated lattices were used to examine the effect of background noise on the ability to detect underlying pattern.

5 Field data were obtained from a Populus balsamifera clone that was colonizing a grassland. Three belt transects, 1 m wide and up to 13 m in length, were established, and ramets in each 0.5‐m interval were aged by tree ring counts. Position and age were used to construct a lattice of stem establishment.

6 We were able to discern a pattern both in artificial lattices and in the colonization of P. balsamifera ramets. Ramets took between 1 and 2 years to advance 1 m into the grassland (equivalent to a rate of 0.5–1 m per year).

7 Describing plant establishment in space and time with two‐factor join count statistics provides a way of measuring the rate of species movement at the scale of the individual.
Selective slug grazing on montane meadow plants
Authors: Scheidel Ulrich , Bruelheide Helge
Published: March 2003

1 In order to test the hypothesis that the sensitivity of field populations of the rare perennialArnica montanato slug attack is due to its high palatability, we comparedArnicaleaves and seedlings with 20 other plant species in greenhouse food choice experiments.

2 When slugs were given a choice of mature plant leaf discs,Arnica montanawas one of the food plants most preferred by all three slug species tested.Arion lusitanicus,ArionsubfuscusandDeroceras agrestediffered only slightly in their preference for particular plant species. Greater differences in acceptability were observed when parameters other than area consumed were evaluated.Arnicaseedlings displayed similarly high susceptibility to slug grazing.

3 Morphological factors influence mollusc feeding behaviour, with epidermal cell wall thickness and hairiness related to acceptability. Removing the hairs by shaving the leaves increased the acceptability of one species,Centaurea jacea.

4 Leaves of undamagedArnica montanaplants were preferred to leaves of plants that had been predamaged by partial leaf removal, suggesting that there is an inducible component of chemical defence.

5 We discuss our results in comparison with other food choice experiments and attempt to extrapolate them to mollusc/plant interactions under field conditions.
Data diving with cross‐validation: an investigation of broad‐scale gradients in Swedish weed communities
Authors: Hallgren Erik , Palmer Michael W. , Milberg Per
Published: March 2003

1 Multivariate analysis of complex data sets is plagued by problems of subjectivity and of finding statistically valid ways to test a large number of plausible hypotheses. We show how patterns in the data can be identified (data diving) as well as rigorously tested statistically by subdividing the data set.

2 We analysed data on weed biomass and environmental variables from more than 2000 plots in cereal and oil‐seed crops in Sweden during 1970–94. Half the data set was used in an exploratory phase while the other half was used in a subsequent confirmatory phase.

3 The exploratory analyses included multivariate statistics [detrended correspondence analysis (DCA) and canonical correspondence analysis (CCA)] with various options and combinations of variables, and led to the formation of hypotheses that were then tested.

4 We tested the hypotheses in a sequential analysis with CCA and Monte Carlo permutation tests: after establishing the influence of one set of environmental variables, this set was covaried out in subsequent analyses. In this way the influence of (i) season of sowing of the crop; (ii) geographical region; (iii) soil type; (iv) crop species; and (v) temporal trends was tested. The four latter were tested separately for spring‐ and autumn‐sown crops.

5 The sowing season of the crop had an overwhelming influence on the weed flora, and many weed species, both annual and perennial, showed strong associations with either autumn or spring. There were significant differences in weed flora composition between the geographical regions and soil types as well as between crop species. There were significant temporal trends only in the weed flora of autumn‐sown crops.

6 This study provides a protocol that combines exploratory ‘data diving’ with strict hypothesis testing using direct gradient analysis methods such as CCA. Such two‐phase analysis should improve the way complex data are analysed and patterns are interpreted.
The effects of plant litter on vegetation: a meta‐analysis
Authors: Xiong Shaojun , Nilsson Christer
Published: March 2003

1 We used data from 35 independently published studies world‐wide to analyse the effects of plant litter on the germination, establishment, species richness and above‐ground biomass of plants. Overall, the short‐term effects of litter on vegetation were mostly negative, although their magnitude varied with vegetation variable, study method, experimental duration, latitude, habitat, type and quantity of litter and target species.

2 Species richness was more affected than above‐ground biomass by litter, suggesting that litter may play a direct role in structuring plant communities as well as influencing competition in productive habitats. Litter had a stronger overall effect on plant germination than on establishment, suggesting that a litter‐reducing disturbance will have more effect early in the growth season.

3 On average, vegetation was more affected by litter in field than in glasshouse studies and during 2‐year than during 1‐year studies. The effect on biomass switched from negative after 1 year to positive after 3 years.

4 The absolute effects of litter on germination and establishment decreased and the absolute effects on above‐ground biomass increased with latitude. Ecosystem type also influenced the effects significantly.

5 Vegetation was generally more depressed by higher litter quantities. Litter composed of forbs and tree leaves had a stronger effect on vegetation than grass litter. The impact of a certain type of litter may therefore be related to its decomposition rate.

6 Tree species were more affected than forbs and grasses by litter, at least at the colonization stage.
Small‐scale disturbance and regeneration dynamics in a neotropical mangrove forest
Authors: Sherman Ruth E. , Fahey Timothy J. , Battles John J.
Published: March 2003

1 Mangrove forests are affected by a variety of natural disturbances that differ in scale, intensity and frequency. Small canopy gaps, although common, have not been well studied. We examined the role of lightning‐created canopy gaps in the dynamics of a 47‐km2 intertidal mangrove community in the Dominican Republic, by quantifying the spatial patterns of overstorey tree distributions, spatial and temporal patterns of gap formation, and tree regeneration in gaps and beneath the closed forest. We hypothesized that regeneration in these gaps would maintain and reinforce species’ distribution patterns across the intertidal gradient in this mangrove ecosystem.

2 All 52 gaps surveyed in the field were nearly circular canopy openings created by lightning. Expanded gap size indicated an average diameter of 30.4 m. The total area of forest in the gap‐phase is currently 1.9%, with an annual formation rate of 0.23% year−1. Canopy turnover was calculated to range from 421 to 842 years; however, gaps were not randomly distributed across the mangrove forest and canopy turnover in the most gap‐prone areas ranged from 194 to 386 years.

3 Seedling density was not different under gaps and under the forest canopy, but sapling density and sapling growth rates of three species were significantly greater in canopy gaps. The annual mortality rate of Rhizophora mangle (9%) in canopy gaps was significantly lower than either Laguncularia racemosa (32%) or Avicennia germinans (56%). Gap regeneration was dominated by R. mangle throughout the forest.

4 The results of this study do not support our initial hypothesis but suggest that the distribution and abundance of R. mangle will increase throughout the forest over time, given the present disturbance regime. Field observations indicated that the peat mat collapses in lightning‐created gaps following their formation, resulting in increased levels of standing water. We suggest the successful regeneration of R. mangle is favoured in these gaps because of its greater tolerance to flooding conditions.
Seed dispersal, habitat suitability and the distribution of halophytes across a salt marsh tidal gradient
Authors: Rand Tatyana A.
Published: March 2003

1  The relative importance of seed availability and the post‐dispersal environment in causing the distribution and abundance patterns of five halophytic forbs and a shrub was investigated across a New England salt marsh tidal gradient. Seed traps and soil samples were used to assess the spatial pattern of seed availability across the marsh, and experimental seed additions were performed to examine the effects of tidal elevation and interspecific competition with dominant grasses and rushes on seedling emergence and survivorship.

2  Seed distributions strongly paralleled adult plant abundance patterns across the marsh, suggesting localized dispersal with limited movement out of parental environments.

3  Adding seeds typically increased seedling densities by at least an order of magnitude, thus lack of seed availability may be important in limiting plant abundance within marsh zones.

4  Post‐dispersal factors were primarily responsible for determining species distribution patterns across zones. Lower limits to the distribution of species typically found at high‐marsh elevations were determined by intolerance to abiotic conditions in the lower marsh zones. In contrast, species typically found at low‐marsh elevations were precluded from the high marsh due to competitive suppression by dominant plants. Patterns of post‐dispersal success were strongly reinforced by limited dispersal.

5  Seed dispersal patterns and post‐dispersal factors may therefore interact to generate distribution and abundance patterns in salt marsh plant communities.
Species functional redundancy, random extinctions and the stability of ecosystems
Authors: Fonseca Carlos Roberto , Ganade Gislene
Published: March 2003

The level of functional redundancy in natural communities is likely to modulate how ecosystem stability is affected by local species extinction. Thus, extinction should have no effect if all species have similar functions, but a major effect if each carries different functions.

  We provide a probabilistic framework that, from any distribution of species number across functional groups, generates specific predictions of how functional groups are lost when species become randomly extinct within a given community. In particular, we predict how many species can go extinct before a community loses its first functional group, a useful index for conservation purposes.

We demonstrate that the probability of a whole functional group becoming extinct from a given community increases with the number of recognized functional groups (functional richness) but decreases with species richness and functional evenness (the distribution of species across functional groups).

  Application of this framework to one published data set for a South American plant community suggested that, if local extinction is random, 75% of the species could be lost before the disappearance of the first functional group.

  However, if redundancy is to be used to determine conservation priorities, the definition of functional groups must be carefully reviewed.
Discordance in spatial patterns of white pine (Pinus strobus) size‐classes in a patchy near‐boreal forest
Authors: Dovčiak Martin , Frelich Lee E. , Reich Peter B.
Published: March 2003

White pines (Pinus strobus) in ac. 1 ha near‐boreal aspen‐red maple stand in the western Great Lakes region, USA, were allocated to five size‐classes that were tested for discordance of their spatial patterns (i.e. within‐size‐class spatial distribution of individuals and spatial associations among different size‐classes). The size‐classes were 0.5–1 m tall, 1–2 m tall, 2–4 m tall, > 4 m tall but < 20 cm diameter at breast height (d.b.h.), and > 20 cm d.b.h. The size‐classes also differed in age. Their spatial patterns were analysed using formulae for spatial autocorrelation with categorical data at neighbourhood (0–14 m) and stand (0–70 m) scales.

Size‐classes clustered in neighbourhoods that differed in size ranging from 6 m in diameter (size‐class 2) to 40 m (size‐class 3), suggesting that the pattern of each size‐class is due to a different set of environmental factors. Similar size‐classes tended to be randomly or positively associated at neighbourhood scales, while the most dissimilar size‐classes occupied different neighbourhoods.

Size‐classes 1 and 2 were located farther away from seed trees than size‐class 3, which was farther away than size‐class 4. Thus periodic seedling invasion of a deciduous matrix may be followed by the gradual retraction of older size‐classes into a refuge near the mature seed source where competition from shrubs and overstorey trees is lower. Although the lack of fine‐scale clustering suggests density‐dependent mortality within the refuge, few older individuals were found outside this area.

Two regeneration bottlenecks may structure white pine populations. First, recruitment into size‐class 2 is restricted to small patches (possibly in understorey gaps) within neighbourhoods with abundant size‐class 1. Relatively unrestricted recruitment to size‐class 3 follows, and after that recruitment to size‐class 4 is again limited, this time to refugia with sparse canopy near adult trees.
Effects of flooding and herbivores on variation in recruitment of palms between habitats
Authors: Pacheco Manoel A. W.
Published: March 2003

It is widely recognized that negative effects of anaerobic stress on growth and survival of flooded plants influence the distribution of numerous species. Less explored is the possibility that heterogeneity in abundance of plants between habitats with distinct flooding regimes may also result from variation in rates of herbivory or in the ability of plants to tolerate losses to herbivores.

Flooding and herbivores were tested as factors underlying variation in abundance of two tropical forest palms,Socratea exorrhiza(which is associated with lowlands adjacent to streams) andOenocarpus bacaba(which is more abundant on plateaux and upper edges of slopes).

In a bench experiment, seeds of both palms were either completely immersed in water for a period of 101 days or not subject to inundation. Flooding inhibited germination of both species but, as expected, the adverse effects were much stronger onOenocarpus.

In a field experiment, seeds of both palms were planted with increasing levels of protection against herbivores on plateaux and in lowlands. Seeds were either not protected or placed within poultry‐netting exclosures, half of which were sprayed with insecticide.

After 17 months, onlyOenocarpushad experienced differential mortality between habitats, and this was clearly associated with the negative effects of flooding on seed germination in lowlands. In contrast, growth differed between habitats only forSocrateaseedlings, where average above‐ground biomass was greater in lowlands.

Although protection with exclosures and insecticide increased survivorship of both species,herbivores caused similar proportions of mortality on plateaux and in lowlands, and had no significant effect on seedling growth. Therefore at this site, herbivores do not appear to influence variation in abundance of species between habitats.