bluuebunny/crossref_metadata_2025 huggingface dataset:
Nutritional status, symptoms experienced and general state of health in HIV‐infected patients
Authors: Karlsson Anette , Nordström Gun
Published: March 2003

• The aim of the study was to describe HIV‐infected patients with respect to nutritional status, symptoms experienced, general state of health, and relevant medical and laboratory data. An additional aim was to study the relationships between some of these variables.

• On admission to an acute care hospital in Sweden, 25 HIV‐positive men were consecutively included in the study. Medical data, anthropometric variables such as weight, height, body mass index (BMI) and percentage weight loss were studied.

• The following instruments were used: the subjective global assessment (SGA) was used to determine nutritional status; the oral assessment guide (OAG) was used for subjective assessment of the oral cavity; and the numeric rating scale (NRS) was used to assess the symptoms experienced. The Health Index (HI) was used to evaluate general state of health.

• The results showed that more than half of the patients had suspected/severe malnutrition; between 48% and 72% complained of moderate to severe symptoms of various kinds. Two thirds felt their general state of health was rather poor or very poor.

• Correlations showed that the lower the BMI, the worse the nutritional status (SGA); the greater the weight loss in percent, the worse the nutritional status (SGA); and the worse the general state of health (HI), the worse the nutritional status (SGA).

• In conclusion, it is important that nurses have good knowledge concerning nutritional problems in order to be able to detect these conditions at an early stage and/or to endeavour to prevent them.
Background pain in fibromyalgia patients affecting clinical examination of the skin
Authors: RAAK RAGNHILD , WAHREN LIS KARIN
Published: March 2003

• The purpose of this study was to investigate the relationship between on‐going pain and acute thermal pain in patients suffering from chronic pain.

• This experimental study in cold and heat sensitivity was performed in order to test the following hypothesis: that fibromyalgia patients scoring high in current background pain tolerate less experimental thermal pain in the skin than patients with low scores.

• Ethical aspects of the study are discussed.

• The level of tolerable experimental thermal stimuli was tested and compared between the `low‐score' and the `high‐score' patients.

• Background pain seemed to affect the intensity of experimental cold pain.

• Clinical routine examinations and bodily care of the skin that might interfere with background pain in the fibromyalgia patients are discussed.

• Clinical practice should be carefully planned in order to assist fibromyalgia patients in understanding and coping with thermal conditions that might influence background pain.
A study of parenteral use of methotrexate in rheumatic conditions
Authors: ARTHUR VALERIE , JUBB RONALD , HOMER DAWN
Published: March 2003

• This paper reports the findings of a small pragmatic study to compare the safety and efficacy of methotrexate administered by intramuscular and subcutaneous injection, and to teach patients to self‐administer methotrexate by the subcutaneous route.

• Eight patients with rheumatic conditions, already receiving a stable weekly dose of methotrexate by intramuscular injection, were entered into this 13‐week study.

• Serum levels of methotrexate were measured on six consecutive occasions: three whilst patients received intramuscular methotrexate and then three after switching to the subcutaneous route.

• Patients were taught to self‐administer their methotrexate subcutaneously and were then discharged to perform this task at home.

• Levels of disease activity and psychological scores were measured at the start and end of the study. Satisfaction with self‐administration and teaching of injection techniques were assessed at 13 weeks.

• Serum methotrexate levels were not significantly affected by the route of administration. All patients were able to perform self‐injection safely and seven out of eight preferred self‐administration at home.

• This small study demonstrates that there is no difference in the safety and efficacy of methotrexate given by either parenteral route. Patients were able to administer safely methotrexate subcutaneously. Self‐administration reduced hospital visits, was more convenient for patients and improved patient satisfaction.
Mental health issues in primary healthcare
Authors: RUSSELL GRAHAM , POTTER LORNA
Published: March 2003

• This article describes a project that was designed to explore mental health issues arising in primary care, as a basis for understanding primary care professionals' mental health training needs.

• Whilst recent UK government initiatives, such as the National Service Framework for Mental Health, have emphasized the need to enhance mental healthcare in the general population, the capacity to respond effectively is likely to be dependent upon primary care professionals acquiring the relevant skills. To achieve this, a thorough understanding of the issues inherent in dealing with mental health problems in primary care is required.

• Given that the mental health issues facing primary care professionals may differ from those that confront mainstream mental health professionals, logic dictates that primary care professionals may require a discrete set of skills and a special approach to mental health training.

• The principal aim of this project was, hence, to identify mental health issues arising in clinical practice, as a first step towards identifying primary care training needs.

• A series of focus groups and semi‐structured interviews was used to gather information about mental health issues arising in primary care, based on the experiences of primary care professionals and users' representatives.

• The findings suggest that primary care professionals are confronted by a wide range of mental health issues, many of which lie outside of the scope of the current National Service Framework for Mental Health. The article discusses the implications for mental health training in primary care practice and future research.
An exploration of the potential risks associated with using pet therapy in healthcare settings
Authors: BRODIE SARAH J. , BILEY FRANCIS C. , SHEWRING MICHAEL
Published: March 2003

• The widespread inclusion of companion animals into the homes and lives of humans has prompted a considerable amount of research into the health benefits of such relationships.

• Findings seem to confirm that if humans interact with companion animals they are likely to experience various health benefits.

• Programmes that encourage and facilitate pet visiting schemes in hospitals have developed and animals can often be found in in‐patient and long‐term care facilities, with the aim of contributing towards a positive therapeutic milieu.

• Despite supportive research evidence, the adoption of such a therapeutic activity may have been restricted by the belief that client safety could be compromised by an increase in the risk of infection acquired from animals, allergic responses and bites.

• This paper explores the literature on these risks and concludes that, in a controlled health care environment in urban Europe or North America and with responsible human behaviour the potential benefits of sharing our lives with companion animals, either at home or hospital, far outweigh the apparently insignificant risks.

• Recommendations aimed at limiting the potential risk of infection and guidelines for the safe management of pet therapy are developed.
Cultural conflict: the impact of western feminism(s) on nurses caring for women of non‐English speaking background
Authors: Blackford Jeanine , Street Annette
Published: March 2003

• Much research has been conducted for understanding the health needs of people of different cultural backgrounds and the problems they experience in seeking health care. In Australia, despite such research, it is argued that there remains an exclusionary health care culture that continues to affect equity and access for people of non‐English speaking background. There was a need for research in which health professionals examined their own Anglo‐Australian culture and its impact on other ethnic communities.

• Such concerns provided the impetus for a feminist praxis study to engage nurses in understanding and improving care for migrant women. This study was conducted with 26 nurses in a paediatric hospital in Melbourne, Australia. Five collaborative research groups were formed, each consisting of four to six nurses who were co‐researchers. Together, the nurses and researchers explored the health care experiences of migrant women, using a variety of quantitative and qualitative data collection strategies.

• This paper explores a major finding of the study, which was the impact of liberal feminist approaches on the practices of Australian nurses who cared for women of different ethnicity and race.

• The study found that the efforts of liberal feminist nurses to ‘treat all people the same’ meant that women from different cultural backgrounds did not always receive equity in care. Through the feminist praxis process the nurses were able to explore contradictions in their practice and focus on equity in care to meet the specific gendered and racially constructed needs of women of different cultural backgrounds.

• A number of strategies were adopted that included regular use of female health interpreters and provision of privacy for migrant women when caring for their children.
Using cost‐effectiveness analysis to compare Hospital at Home and in‐patient interventions. Part 2
Authors: Jester Rebecca , Hicks Carolyn
Published: March 2003

•  An economic analysis was conducted as an integral part of a comparison of the effectiveness and suitability of Hospital at Home (HaH) and in‐patient interventions. The sample comprised 109 adult primary total joint replacement patients and 21 of their co‐resident informal carers.

•  Part 2 is principally a methodology paper and describes how nurses may use a variety of methods to compare cost between treatment modalities. A Cost‐Effectiveness Analysis framework uses the data from Paper 1 to calculate the economic feasibility of HaH compared with traditional in‐patient interventions as a worked example of how the principles of economic analysis can be used within health care research. The basic information for calculating cost of both interventions was obtained by multiplying the mean length of total treatment days by the cost per treatment day. However calculating and comparing cost for in‐patient and HaH modalities was multifaceted and included costs incurred by patients and families as well as any shift in cost from tertiary to community and outpatient services.

•  Application of the cost‐effectiveness analysis framework demonstrated that not only was HaH more effective than in‐patient care in several aspects, but also it was less costly because of a mean reduction in length of stay of 0.9 days per patient and a significant reduction in cost per treatment day because of removal of hospital overhead costs and reduced special duty payments even when offset against additional transport, community and outpatient costs.
A review of the newer aromatase inhibitors in the management of metastatic breast cancer
Authors: Reddy
Published: March 2003

Background:
Breast cancer remains a major cause of morbidity and mortality world‐wide. While aminoglutethimide, a first‐generation aromatase inhibitor, has equivalent efficacy to first‐line tamoxifen in the palliative treatment of metastatic breast cancer, its toxicity profile has relegated this drug to a second‐ or third‐line agent in this setting. Recently, several aromatase inhibitors have been released onto the market while others are in phase II and III clinical trials

Aim:
To review the role of the new aromatase inhibitors in the management of metastatic breast cancer

Methods:
Current literature, abstracts from meetings and information from pharmaceutical manufacturers have been summarized

Content: A review of the clinical pharmacology of the new aromatase inhibitors has been provided in addition to a synopsis of phase III clinical studies

Conclusion:
The newer aromatase inhibitors have several advantages compared to aminoglutethimide and are a useful addition to the armamentarium of therapies employed in the palliative management of advanced breast cancer
Prospective investigation of a subcutaneous, implantable central venous access device for therapeutic plasma exchange in adults with neurological disorders
Authors: Pertiné Basilio , Razvi Syed A. , Weinstein Robert
Published: March 2003

Standard alternatives to antecubital access for long‐term therapeutic plasma exchange, including percutaneous polyurethane or tunneled silicone catheters, are associated with complications and inconvenience for the patient. We have investigated the Bard CathLink® 20, a subcutaneously implantable central venous access device, as an alternative for outpatient plasma exchange. The CathLink® 20 consists of a funnel‐shaped titanium port connected to a soft polyurethane‐derived catheter and is accessed percutaneously using an 18‐gauge catheter‐over‐needle Angiocath®. Six patients with paraproteinemic polyneuropathies underwent 64 outpatient plasma exchanges using the CathLink® 20 for access, 31 using 2 CathLink® 20's (draw and return), 20 using a single CathLink® 20 as the draw site and 13 using a single CathLink® 20 as the return site. Mean (± SD) plasma removed was 3,680 ± 551 ml in 115.2 ± 25.3 min. Apheresis personnel were able to access the ports in 1.23 ± 0.6 attempts per port per procedure. Six of 70 planned procedures were aborted: 3 because of failure of an antecubital access site and 3 because of catheter occlusion resolved using a thrombolytic agent. Whole blood flow rate was approximately 54 ml/min, and plasma flow rate was about 32 ml/min for 135 min. Access pressures were stable at −150 to −200 torr (P = 0.1395). Return line pressures varied between 90 and 130 torr (P = 0.0147). No patient required hospitalization during the study. Though not optimized for apheresis, the CathLink® 20 provides a reasonable option for chronic apheresis patients who lack adequate peripheral venous access. J. Clin. Apheresis 17:1–6, 2002. © 2002 Wiley‐Liss, 2002.
Influence of women’s workload on their nutritional status in selected communities in Ghana
Authors: Nti Christina A. , Inkumsah Dora , Fleischer Grace
Published: March 2003

Abstract: A study was undertaken to assess the impact of women’s work on their health and nutritional status in Ghana. Using a combination of purposive sampling and cluster sampling techniques, 80 women were selected from Madina (suburban) and Boi (rural) communities in the Greater Accra Region of Ghana. Structured questionnaire and 24‐h dietary recall methods were used to collect the information on the nature of the women’s work, the amount of time used for the activities, health problems and food intakes. Nutritional anthropometry (weight, height) was used to assess the nutritional status using body mass index (BMI) as an indicator. The results revealed that the women were involved in multiple activities and worked between 12 and 17.5 h daily. In an attempt to fulfil their multiple roles, the women suffered many physiological problems, with general weakness and tiredness, body pains, dizziness, headaches, arthritis and malaria being the most common ailments. For food intake and nutrition, it was observed that 70% of the women had only two meals in a day. The reasons attributed to this include lack of time, the need to leave home early and too much involvement in work. The diet of the rural residents were low in almost all the nutrients calculated, whereas that of the urban residents was slightly deficient in protein, energy, iron and calcium. Using BMI as a measure of nutritional status, 31% of the women were found to be at nutritional risk.
Benefits of plant diversity to ecosystems: immediate, filter and founder effects
Authors: Grime J. P.
Published: March 2003

1 It is useful to distinguish between the immediate effects of species richness on ecosystems and those which become apparent on a longer time scale, described here as filter and founder effects.

2 Relationships between plant diversity and ecosystem properties can be explored by classifying component species into three categories – dominants, subordinates and transients. Dominants recur in particular vegetation types, are relatively large, exhibit coarse‐grained foraging for resources and, as individual species, make a substantial contribution to the plant biomass. Subordinates also show high fidelity of association with particular vegetation types but they are smaller in stature, forage on a more restricted scale and tend to occupy microhabitats delimited by the architecture and phenology of their associated dominants. Transients comprise a heterogeneous assortment of species of low abundance and persistence; a high proportion are juveniles of species that occur as dominants or subordinates in neighbouring ecosystems.

3 A ‘mass ratio’ theory proposes that immediate controls are in proportion to inputs to primary production, are determined to an overwhelming extent by the traits and functional diversity of the dominant plants and are relatively insensitive to the richness of subordinates and transients. Recent experiments support the mass ratio hypothesis and the conclusion of Huston (1997) that claims of immediate benefits of high species richness to ecosystem functions arise from misinterpretation of data.

4 Attribution of immediate control to dominants does not exclude subordinates and transients from involvement in the determination of ecosystem function and sustainability. Both are suspected to play a crucial, if intermittent, role by influencing the recruitment of dominants. Some subordinates may act as a filter influencing regeneration by dominants following major perturbations.

5 Transients originate from the seed rain and seed banks and provide an index of the pool of potential dominants and subordinates at specific sites. Where the landscape carousel operates against a background of declining diversity in the reservoir of colonizing transients, we may predict that a progressive loss of ecosystem functions will arise from the decline in the precision with which dominants can engage in the re‐assembly and relocation of ecosystems.
Interspecific differences in above‐ground growth patterns result in spatial and temporal partitioning of light among species in a tall‐grass meadow
Authors: Anten Niels P. R. , Hirose Tadaki
Published: March 2003

1 We compared allometric growth patterns, canopy structure and light interception for individual shoots of different species in a tall‐grass meadow.

2 The vertical distributions of above‐ground biomass, leaf area, height and leaf angles were measured, both early and late in the season, for individual shoots of Miscanthus sinensis (the dominant species), Lespedeza bicolor, Lysimachia clethroides, Astilbe thunbergii and Potentilla freyniana. A canopy model was developed to calculate light absorption by individual shoots. Light absorption per unit mass (Φmass) was used to quantify the efficiency with which plants utilized biomass to capture light.

3 The leaf mass ratio (LMR), average specific leaf area (SLA) and therefore the leaf area ratio (LAR) decreased with shoot height and light availability. Light absorption per unit leaf area (Φarea) increased with shoot height, and this increase was observed to be much stronger at greater than at smaller shoot heights.

4 In the taller species (Miscanthus and Lespedeza) Φmass (the product of LAR and Φarea) increased, while in the shortest species (Potentilla) it decreased with shoot height. Clones of Miscanthus and Lespedeza may thus increase total light capture by allocating shoot biomass among fewer taller shoots, and a clone of Potentilla by producing a larger number of shorter shoots.

5 Shoots of the shorter species were equally efficient in capturing light (i.e. they had similar Φmass) early in the season, but less efficient later in the season than shoots of the taller species. Shorter species appear to be able to use the earlier part of the season for efficient light capture, while shoots of taller species gain an advantage from their height later in the season.

6 This study shows how different above‐ground growth patterns of the species in a tall‐grass meadow allow them to use different positions in vertical space and different periods of the season to absorb light efficiently. This is a clear example of niche separation and helps to explain the coexistence of these species.
Dioecy‐induced spatial patterns of two codominant tree species,Podocarpus nagiandNeolitsea aciculata
Authors: Nanami Satoshi , Kawaguchi Hideyuki , Yamakura Takuo
Published: March 2003

1 Spatial patterns of two codominant dioecious tree species,Podocarpus nagiandNeolitsea aciculata, were analysed at Mt. Mikasa, Nara City, Japan.Podocarpus nagihas a higher shade tolerance but a narrower seed dispersal range thanN. aciculata.We examined the effects of dioecy on regeneration and coexistence of the two species.

2 Seeds ofP. nagiare dispersed by gravity around female trees. Young plants ofP. nagiwere clumped and showed significant attraction to large female trees and significant repulsion from large male trees. Dioecy therefore affected the spatial heterogeneity of plant density in theP. nagipopulation.

3 Seeds ofN. aciculataare widely dispersed by birds, and young plants ofN. aciculatatherefore showed no significant attraction to female trees. This wide dispersal of seeds moderated the effects of dioecy on the spatial pattern inN. aciculata.

4 LargeN. aciculatatrees were clumped and showed significant attraction to large maleP. nagitrees, suggesting that growth ofN. aciculatais facilitated where youngP. nagiplants are uncommon and competition is therefore less intense.

5 One effect of dioecy may be to produce a population structure forP. nagithat promotes its coexistence withN. aciculata.
Using spatial pattern analysis to distinguish causes of mortality: an example from kelp in north‐eastern New Zealand
Authors: Cole Russell G. , Syms Craig
Published: March 2003

1 Spatial analysis techniques were used to differentiate between climate‐induced and pathogen‐induced mass mortalities of the kelpEcklonia radiatain north‐eastern New Zealand. We predicted that climate‐induced effects would generate broad‐scale patterns, whereas pathogen‐induced mortality would be traceable among neighbouring thalli.

2 Spatial autocorrelation analysis was performed on the proportion ofE. radiataaffected by dieback in quadrats during an initial mortality event in 1991. The absence of any consistent spatial scale of affected thalli between 10 and 100 m suggested that small‐scale spread of an agent might be occurring.

3 Individual thalli were therefore mapped at two sites during a subsequent mortality event in 1992/93, and the degree of damage recorded. Spatial analyses found little evidence of aggregation of either intact or affected thalli at scales of 1–150 cm.

4 The relative spatial patterns of healthy and affected plants in mapped quadrats during the 1992/93 mortality provided little evidence of spatial association or repulsion between these broad damage categories.

5 The large‐scale mortality of 1992/93 was consistent with a physiological response to broad‐scale light deprivation, although other agents, perhaps both a virus and amphipod grazing, might also have been involved. Potentially complex interactions among the candidate agents render interpretation of the spatial patterns difficult.
Vascular plant species richness in Alaskan arctic tundra: the importance of soil pH
Authors: Gough Laura , Shaver Gaius R. , Carroll Jenny , Royer Dana L. , Laundre James A.
Published: March 2003

1 Species diversity in the Arctic varies dramatically across abiotic gradients, including topography, moisture, pH and nutrient availability. We hypothesized that vascular plant species density, richness and diversity in Alaskan tundra would be correlated with: (i) site age, (ii) soil pH, (iii) above‐ground productivity and biomass, and (iv) spatial heterogeneity. We sampled moist tussock, snowbed and watertrack communities in three sites that differed in substrate age (11 000–4.5 million years since deglaciation) for a variety of environmental and vegetation data over one growing season.

2 Productivity, biomass and heterogeneity were not consistently correlated with species density. However, variation in canopy height was correlated with species density and richness in a unimodal fashion, suggesting that heterogeneity of the light regime may be important for maintaining higher species numbers.

3 The 11 000‐year‐old site supported more vascular plant species than the two older sites, primarily due to greater numbers of forb species on the youngest site.

4 Soil pH was significantly positively correlated with species richness (R2 = 0.82) and species density (R2 = 0.61). In general the species found on acidic substrates (pH < 5.5) also occurred on non‐acidic substrates (pH > 5.5).

5 This pattern of higher richness with higher pH occurs across other tundra types throughout the Arctic, suggesting that soil pH is an important filter of the regional species pool within northern regions, although other factors may become more important at local scales.
Precipitation, decomposition and litter decomposability ofMetrosideros polymorphain native forests on Hawai’i
Authors: Austin Amy T. , Vitousek Peter M.
Published: March 2003

1 The effects of precipitation on litter quality and surface litter decomposition were evaluated across a natural rainfall gradient, ranging from 500 to 5500 mm mean annual precipitation, on the island of Hawai’i.

2 Litter ofMetrosideros polymorphafrom the driest (500 mm) and wettest (5500 mm) extremes of the gradient was decomposed at five sites along the precipitation gradient. Metrosideros polymorphalitter collected from all sites was also decomposed at a single common site (2500 mm), andM. polymorphalitter collected from each site was decomposed at the site of collection (in situ).

3 Initial litter quality varied significantly with precipitation at the site. Leaf mass per area (LMA) and phosphorus content decreased, while lignin and nitrogen content both increased, with increasing site precipitation.

4 Mass loss of all common litter types increased with increasing precipitation, as didin situdecomposition, which gavek‐values ranging from 0.22 to 1.06. When decomposition at the same site was evaluated, litter from the driest site decomposed up to 2.5 times more rapidly than wet‐site litter.

5 Decomposition at the common site showed an inverse correlation between inherent decomposability of litter (i.e. litter quality) and precipitation at the site from which litter originated, withk‐values ranging from 0.71 for litter from the driest site to 0.28 for litter from the wettest site. Decomposability correlated strongly and inversely with initial lignin concentrations.

6 Proportional nutrient release fromin situlitter was slower than mass loss, but nitrogen and phosphorus mineralization generally increased with increasing precipitation.

7 At the common site, there was an inverse relationship between rate of nutrient release and precipitation at the site where litter was collected. The systematic variation in litter decomposability due to changes in annual precipitation appears to buffer the direct effects of precipitation on carbon and nutrient turnover.
Changes in allozyme frequencies inFestuca ovinapopulations after a 9‐year nutrient/water experiment
Authors: Prentice Honor C. , Lönn Mikael , Lager Helena , Rosén Ejvind , Van Der Maarel Eddy
Published: March 2003

1 The grassFestuca ovinais an important constituent of the species‐rich ‘alvar’ grasslands on the Baltic island of Öland. Levels of allozyme polymorphism are high and variation is known to be correlated with habitat variation (soil moisture, pH and depth).

2 A 9‐year field experiment on species diversity provided replicate plots (in three sites) that had been subjected to six different experimental treatments (control; N + P + K; P + K; N + K; K; water).

3 Samples ofF. ovinawere collected and analyses of deviance were used to investigate associations between allele frequencies, at each of four polymorphic loci, and the nutrient/water treatments. We also used the models to estimate predicted values for the alleles in different nutrient/water treatments and in interactions involving the nutrient/water treatments and additional explanatory variables (vegetation height and clipping).

4 There were significant allozyme frequency differences between samples ofF. ovinafrom the six different nutrient/water treatments in the grassland experiment. Frequencies in the fertilized or watered plots had diverged from those in the control plots. There were also significant allele–habitat associations (after the removal of site effects), especially at the Pgi‐2 locus.

5 Soil moisture was the only variable that was common to this study and an earlier study of variation inF. ovinain natural habitats. In natural populations, the Pgi‐2‐2 allele was significantly associated with soil moisture and was more common in dry habitats. Our findings that the frequency of the Pgi‐2‐2 allele was significantly affected by the nutrient/water treatments, and that it was rarest in the treatment that involved the addition of extra water, were therefore as predicted.

6 The study supports the conclusion, from an earlier study of populations in unmanipulated grassland habitats, that selection is contributing to the fine‐scale patterning of genetic variation in the alvar populations ofF. ovina.
Abundance and distribution of desert annuals: are spatial and temporal patterns related?
Authors: Guo Qinfeng , Brown James H. , Valone & Thomas J.
Published: March 2003

1  Spatial distribution–abundance relationships have been intensively studied. Workers have now begun to study temporal relationships but little is known about how these are related to spatial patterns. We examined these relationships both over space and time using 15 years of data from permanent quadrats in the Chihuahuan Desert.

2
 Winter and summer annual communities were analysed. Within single years, the species in each community exhibited a positive relationship between distribution and abundance at two spatial scales, 0.25‐ha plots and 0.25‐m2 quadrats. Over 15 years, the species in each community also exhibited a positive relationship between abundance and the number of years in which they were present. Species frequency distributions, both in space and over time, were scale‐dependent.

3  Over space, the frequency distribution was bimodal at large (plot) scales, but unimodal at small (quadrat) scales in both communities. Over time, the frequency distribution was bimodal for winter annuals but unimodal for summer annuals, a difference we attribute to the marked difference between the two communities in the temporal consistency of rank abundance of species. We conclude that both niche and metapopulation models can be used in explaining the distribution patterns of species but at different scales. The factors and processes in these models are not mutually exclusive in determining the overall abundance and distributions of these species in space and over time.
Fluctuating resources in plant communities: a general theory of invasibility
Authors: Davis Mark A. , Grime J. Philip , Thompson Ken
Published: March 2003

1 The invasion of habitats by non‐native plant and animal species is a global phenomenon with potentially grave consequences for ecological, economic, and social systems. Unfortunately, to date, the study of invasions has been primarily anecdotal and resistant to generalization.

2 Here, we use insights from experiments and from long‐term monitoring studies of vegetation to propose a new theory in which fluctuation in resource availability is identified as the key factor controlling invasibility, the susceptibility of an environment to invasion by non‐resident species. The theory is mechanistic and quantitative in nature leading to a variety of testable predictions.

3 We conclude that the elusive nature of the invasion process arises from the fact that it depends upon conditions of resource enrichment or release that have a variety of causes but which occur only intermittently and, to result in invasion, must coincide with availability of invading propagules.
The demographics of resprouting in tree and shrub species of a moist tropical forest
Authors: Paciorek Christopher J. , Condit Richard , Hubbell Stephen P. , Foster Robin B.
Published: March 2003

1 Individuals of many woody plant species have the ability to respond to damage which causes removal of the crown by producing new branches (sprouts) along the remaining stem. Resprouting by woody plants has received little attention in relatively undisturbed tropical forest.

2 To assess the importance of resprouting for forest dynamics, we estimated resprouting rates and mortality rates of resprouted individuals for the forest as a whole and for individual species in a 50‐ha permanent plot in tropical moist forest on Barro Colorado Island, Panama. We tested for differences between species and asked whether the differences were related to phylogeny, growth form or shade tolerance.

3 Among individuals not known to have resprouted previously, we estimate that the annual rate of resprouting is 1.7% for individuals in both small and large size classes (1–9.9 cm d.b.h. and ≥ 10 cm d.b.h.). For small and large individuals, respectively, annual mortality of previously undamaged individuals is 2.2% and 1.5%, while that of resprouted individuals is 9.6% and 10.3%. This resulted in survival of 62% of resprouted individuals over 5 years, compared to 90% survival among individuals not known to have resprouted recently.

4 Resprouting rates varied by species and family, but little between growth forms. Species in the families Lauraceae and Piperaceae had high rates of resprouting. Resprouting was common across the spectrum of shade tolerance.

5 Damage to woody forest plants on Barro Colorado Island is frequent, and many species are able to respond by resprouting. Resprouting ability may be an important life history characteristic of woody species on BCI, with individuals experiencing both increases and decreases in size.
Colonization constraints during primary succession on coastal Lake Michigan sand dunes
Authors: Lichter John
Published: March 2003

1 Primary succession on coastal sand dunes has generally been presumed to be driven by autogenic environmental change associated with dune stabilization and gradual soil development.

2 An extensive chronosequence of dune‐capped beach ridges is found adjacent to northern Lake Michigan and the youngest 13 ridges (aged 30–440 years old) show a clear pattern of primary succession and development of a forest ecosystem.

3 Seed‐addition and seedling‐transplant experiments indicated that colonization of young sand dunes by late‐successional Pinus and Quercus species is constrained by limited seed dispersal, seed and seedling desiccation, and seed predation rather than seedling success being constrained by low soil nitrogen availability. Their establishment may therefore depend on coincidence of chance seed dispersal, favourable weather conditions and low rodent densities.

4 In addition, episodic burial by sand prevents most species from colonizing young dune ridges, while burial of seedlings by litter limits recruitment on older dune ridges with developing forest. The intensity of competition increases during succession.

5 Dune succession is better described as the transient dynamics of colonization and competitive displacement rather than the result of gradual soil development and competitive displacement.
Effects of fine‐scale disturbances on the demography and population dynamics of the clonal moss Hylocomium splendens
Authors: Rydgren Knut , De Kroon Hans , Økland Rune H. , Van Groenendael Jan
Published: March 2003

The boreal forest is subject to disturbance but the effects on population dynamics are poorly understood. We investigated how a prominent species of the forest floor, the clonal moss Hylocomium splendens, responded to different types of fine‐scale disturbance.

Canopy gap formation was simulated in H. splendens populations by removing 50% of the bryophyte layer (Removal treatment) and herbivory by clipping all of its growing points (Clipped treatment). Demographic parameters and population dynamics were compared with an unmanipulated reference population (Ref).

Both types of disturbance caused a significant decrease in mean segment size (particularly following clipping) and an increase in branching rates. Branching rates in the Removal population were enhanced at all architectural opportunities for enhanced branching, but only the Clipped segments themselves were affected during the 2 years following disturbance.

The population effects of disturbance were analysed by a periodic matrix model, with 3‐year as the period, followed by elasticity analysis. The Ref population was approximately stable (growth rate, λ = 1.012), with the survival of mature segments making an overwhelming contribution to its growth rate. The higher λ (1.740) in the Removal population was associated with higher elasticities of branching. Clipping reduced λ to 0.841 by blocking segment survival, although regeneration of new growing points on the remnant main shoot axis after 1 year, and its subsequent maturation in the next year, then made a major contribution.

Life table response experiment analyses revealed that almost all demographic processes including branching and the survival of mature segments contributed to the increased λ in Removal treatment. The relatively small decrease in λ following clipping was mainly due to the absence of mature segment survival, being almost balanced by the pulse of regeneration of growing points the year after disturbance.

We conclude that H. splendens populations show a good ability to recover from common types of disturbances in their environment. The general mechanisms behind the responses are discussed.
Relationships between plant nitrogen economy and life history in three deciduous‐forest herbs
Authors: Rothstein David E. , Zak Donald R.
Published: March 2003

We compared nitrogen (N) uptake and whole‐plant N dynamics in three deciduous‐forest herbs of contrasting life histories: the spring ephemeralAlliumtricoccum, the summergreenViolapubescensand the semievergreenTiarellacordifolia. We predicted that differences in above‐ground physiology would translate into differences in N acquisition and partitioning, such that nitrogen‐use efficiency (NUE) would increase fromAlliumtoViolatoTiarella.

Patterns of N uptake were generally the opposite of our predictions.Alliumhad the lowest N uptake capacity in both laboratory and field experiments whereas roots ofTiarellahad the highest specific N uptake capacity.

Violawas the only species in which the specific uptake capacity of roots was related to photosynthetic activity of leaves, both decreasing by a factor of two from spring to summer. In contrast,Tiarellaconsistently had the lowest photosynthetic capacity and the highest specific uptake capacity whereasAlliummaintained substantial root uptake capacity throughout the summer when it had no photosynthetic activity.

There were no significant differences between species in overall NUE. However, there were differences in the components of NUE: nitrogen productivity (A) and mean residence time of N in the plant (MRT). Nitrogen productivity increased, and MRT decreased, fromAlliumtoViolatoTiarella.

In all three species, there was a balance between acquisition of N and building of biomass over the annual growth cycle, despite dramatic disjunctions between the tissue‐specific rates of carbon and N acquisition inAlliumandTiarella. The variation in A and MRT we observed among co‐occurring species of a single N‐rich habitat was comparable with that observed by other researchers studying plants adapted to habitats of widely varying N availability.
Habitat requirements for establishment of Sphagnum from spores
Authors: Sundberg Sebastian , Rydin Håkan
Published: March 2003

1 The ecological significance of the spore in perennial bryophytes has been questioned. In Sphagnum, protonemata have rarely been observed in the field and P‐concentrations in natural waters are insufficient for spore establishment.

2 We determined requirements for establishment of Sphagnum spores in growth chamber experiments. Up to 17 species were tested on peat with various natural substrates added and with different mire waters. In a field experiment, the effect of cover of nutrient depleted Eriophorum‐litter was also tested.

3 There were large differences between substrates, and establishment appeared to be limited by the amount of phosphate released. Added moose dung or litter of Betula pubescens promoted establishment well above the low level seen on peat alone, or with added litter from Pinus sylvestris.

4 Species differed slightly in response to different mire waters and to added substrates, but these differences could not be attributed to the natural habitat of the species or their breeding system. There was a weak negative relationship between spore size and establishment success.

5 In the field experiment, about 1% of the sown, viable spores established in the presence of moose dung or Betula litter. With moose dung there was an indication that protonemata and plants of other bryophytes had a negative effect on the establishment of Sphagnum.

6 Nutrient release from litter and cover provided by vascular plants are needed to generate safe sites for the establishment of Sphagnum from spores, especially on wet, acidic and relatively nutrient‐poor soils and peat. Recruitment from spores may therefore be important in Sphagnum, particularly following disturbance.
The relationship between growth and mortality for seven co‐occurring tree species in the southern Appalachian Mountains
Authors: Wyckoff Peter H. , Clark James S.
Published: March 2003

Slow growth is associated with high mortality risk for trees, but few data exist to assess interspecific differences in the relationship between growth and mortality. Here we compare low growth tolerance for seven co‐occurring species in the southern Appalachian Mountains:Acer rubrum,Betula lenta,Cornus florida,Liriodendron tulipifera,Quercus prinus,Quercus rubraandRobinia pseudo‐acacia.

For all species, mortality was greater for understorey individuals than for canopy trees. Species varied widely in the length of growth decline prior to death, ranging from 6 years forL. tulipiferato more than 12 years forQ. rubra.

Growth‐mortality functions differ among species, but we found little evidence of a trade‐off between tolerance of slow growth and an ability to show rapid growth in high light conditions.

A. rubrumstands out in its ability both to grow rapidly and to tolerate slow growth, suggesting that its density may increase at our study site as in other parts of the eastern United States. In contrast,C. floridashows high mortality (15% per annum) as a result of infection with dogwood anthracnose.

We modified a forest simulation model, LINKAGES (which assumes that all species have the same ability to tolerate slow growth), to include our functions relating growth and mortality. The modified model gives radically altered predictions, reinforcing the need to rethink and re‐parameterize existing computer models with field data.
Carbon limitation in trees
Authors: Körner Christian
Published: March 2003

The ongoing enrichment of the atmosphere with CO2 raises the question of whether growth of forest trees, which represent close to 90% of the global biomass carbon, is still carbon limited at current concentrations of close to 370 p.p.m. As photosynthesis of C3 plants is not CO2‐saturated at such concentrations, enhanced ‘source activity’ of leaves could stimulate ‘sink activity’ (i.e. growth) of plants, provided other resources and developmental controls permit. I explore current levels of non‐structural carbon in trees in natural forests in order to estimate the potential for a carbon‐driven stimulation of growth.

The concentration of non‐structural carbohydrates (NSC) in tree tissues is considered a measure of carbon shortage or surplus for growth. A periodic reduction of NSC pools indicates either that carbon demand exceeds con‐current supply, or that both source and sink activity are low. A steady, very high NSC concentration is likely to indicate that photosynthesis fully meets, or even exeeds, that needed for growth (surplus assimilates accumulate).

The analysis presented here considers data for mature trees in four climatic zones: the high elevation treeline (in Mexico, the Alps and Northern Sweden), a temperate lowland forest of central Europe, Mediterranean sclerophyllous woodland and a semideciduous tropical forest in Panama.

In all four climatic regions, periods of reduced or zero growth show maximum C‐loading of trees (source activity exceeding demand), except for dry midsummer in the Mediterranean. NSC pools are generally high throughout the year, and are not significantly affected by mass fruiting episodes.

It is concluded that, irrespective of the reason for its periodic cessation, growth does not seem to be limited by carbon supply. Instead, in all the cases examined, sink activity and its direct control by the environment or developmental constraints, restricts biomass production of trees under current ambient CO2 concentrations.

The current carbohydrate charging of mature wild trees from the tropics to the cold limit of tree growth suggests that little (if any) leeway exists for further CO2‐fertilization effects on growth.
A new learning environment: combining clinical research with quality improvement
Authors: Pronovost Peter J. , Kazandjian Vahé A.
Published: March 2003

Abstract: The emphasis provided by quality improvement strategies on performance measurement and evaluation often results in our understanding of processes of care and, perhaps, better outcomes. There are different references for process evaluation: external peers, regional profiles of performance or a trending of one's own performance patterns. This paper proposes a methodology that enables learning from the daily practice of medicine by comparing alternative care processes and outcomes. Since it is estimated that 15–20% of medical practices are based on rigorous scientific data establishing their effectiveness, we have much to learn. We propose to learn from our daily practice by combining clinical research methods with quality improvement tools. The products comprise modified clinical trial and case–control studies. In a modified clinical trial, we would use a practice guideline as a control group and modify the guideline to create an experimental group. This method would maintain the internal validity of efficacy research while maintaining the external validity of effectiveness research. In the case–control method, it is possible to quantitate risk for a given outcome and focus improvement effort on factors associated with that outcome. We believe physicians will accept this learning approach because it is a more valid learning method than traditional quality improvement and, unlike randomized clinical trials, learning will occur in the daily practice of medicine.