bluuebunny/crossref_metadata_2025 huggingface dataset:
Telephone nurses' experience of problems with telephone advice in Sweden
Authors: Wahlberg Anna Carin , Cedersund Elisabet , Wredling Regina
Published: March 2003

• By telephoning a healthcare call centre, individuals in Sweden can consult a nurse to discuss medical problems and health care accessibility, and to receive professional information on how to find their way about the health care system.

• The aim of the study was to identify problems, difficulties and disadvantages that telephone nurses with varying degrees of experience had met during their professional careers.

• The Delphi technique was used with three sets of questionnaires.

• Twenty‐five nurses with varying experience of working with telephone advice from six 24‐hours call centres participated in the study. The response rate was 100%.

• An open‐ended question generated 154 statements. Comments were categorized into 24 different problem categories.

• Ten problem categories were mainly related to the nurse perspective, i.e. the problems experienced were associated with the qualities of the nurse, eight principally to the patient perspective, i.e. problems associated with caller characteristics and six mostly to the organizational perspective, i.e. problems linked to the organization of the national health service.

• ‘Lack of health care resources’ was rated as the biggest problem, ‘second‐hand consultations’ as the second and ‘always making a decision’ as the third biggest problem.

• Decision‐making seems to be the core of telephone advice nursing and problems related to the nurses, patients and organization seem to influence the telephone nurses' working situation.

• Training should focus on active listening and handling social conflicts.
Training teachers in computer‐based management information systems
Authors: North R.F.J. , Strain D.M. , Abbott L.
Published: March 2003

Abstract This paper presents an evaluation of a multimedia training programme, supported by a video‐conference link, for senior school staff in the use of a computer‐based Management Information System and the subsequent impact on the school organisation. The training took place as a part of the Education Departments' Superhighways Initiative. Two years later the impact of this initiative on school management practice was examined and the implications of subsequent patterns of staff use of ICT in management assessed. Results indicate that change strategies should involve attention to the totality of the relevant school system and should provide for professional dialogue and participation in the process.
Computer support for peer‐based methodology tutorials
Authors: Anderson A. , Cheyne W. , Foot H. , Howe C. , Low J. , Tolmie A.
Published: March 2003

Abstract This paper reports on a study that was designed to explore computer support for peer‐based learning in methodology tutorials. In particular, software was developed to organise group discussion, with the aim of leaving students free to concentrate on the more productive elements of group dialogue, and in particular discussing their ideas. Forty‐three undergraduate psychology students in groups of 3–4 were given a series of computer‐supported methodology tutorials designed to structure their discussion around issues concerning the design of their Honours dissertation. Students gave individual ratings of their reactions to both the software and the tutorial sessions more generally. A sample of their discussions was videotaped and the dialogues analysed. The written assignments in which they detailed their proposed empirical work (the ‘Design Exercise’) were blind marked and compared to a sample of similar assignments from the previous year. The results demonstrated that the computer‐supported tutorials resulted in better quality Design Exercises, that the students' dialogues were overwhelmingly task‐focussed and substantially transactive, and that their expressed satisfaction was generally high but with a desire for more preparation time before and between tutorials. The implications of the study for the use of computers to support groupwork are discussed.
The efficacy of a World‐Wide Web mediated formative assessment
Authors: Buchanan T.
Published: March 2003

Abstract  Two studies evaluated the effectiveness of a WWW‐based formative assessment package used in undergraduate psychology courses. Students taking on‐line multiple‐choice tests received instant feedback on areas of weakness and how to address them. In Study 1, students used the package as an integral part of their course syllabus. Level of use correlated with performance in the end‐of‐course summative assessment. In Study 2, the package was used as an ‘optional extra’. Both studies found that students who used the package performed better than those who did not. Such systems may be useful learning tools which students may use to enhance performance.
Graphing investigations using portable (palmtop) technology
Authors: Hennessy S.
Published: March 2003

Abstract  The increasing use of portable computers raises issues about their impact on learning and attitudes to computing. These issues were explored in an evaluation of a weather project undertaken by 48 students aged 13–14 using palmtop computers. Students worked in groups over 3 weeks, collecting and graphing temperature data. Motivation and confidence in using technology increased and learning gains of averages and graph interpretation were observed. The evaluation illustrated the potential power and versatility of portable technology in tackling graphing, and the opportunities they present for student participation. Some pedagogic implications of using portables are considered.
The evaluation of online courses
Authors: Benigno V. , Trentin G.
Published: March 2003

Abstract  Given the special characteristics of online courses, their quantitative/qualitative evaluation calls for the adoption of specific procedures to assess both the learning process and the participant performance. This paper seeks to shed light on the aspects and issues involved in the evaluation of online courses, focusing on the peculiarities that distinguish such evaluation from that of traditional distance education. Subsequently, a methodological approach will be proposed that was developed and tested during evaluation of online courses for in‐service teacher training and for training of staff in small and medium‐sized enterprises.
Cognitive load while learning with a graphical computer interface
Authors: Martin‐Michiellot S. , Mendelsohn P.
Published: March 2003

Abstract  Computer software packages are hard to learn but little is known about how to help new users. A study was made in which 30 learners had to learn the basic commands of a CAD software package using manuals with different formats of presentation of instructions. Ten learners learned using a conventional manual plus a computer, 10 learners learned using a manual with juxtaposed screen images but no computer and 10 learners learned using a manual with integrated screen images but no computer. Each learner was tested with a practical and a written test and the learning time was measured. There was no statistical difference between the groups of learners for the score of the practical and written tests. However, it was found that learners using a manual with juxtaposed or integrated screen images had learned twice as fast as learners using a conventional manual. The discussion questions the use of conventional manuals to learn application software and stress as the key role of the graphical environment in the learning process.
Plant foraging and dynamic competition between branches ofPinus sylvestrisin contrasting light environments
Authors: Stoll Peter , Schmid Bernhard
Published: March 2003

1 The morphological plasticity of sun and shade branches ofPinus sylvestrisgrowing at the edge of a ‘tree‐patch’ created in 1989, when surrounding trees were removed, was compared with that of branches of trees growing in the centre of the patch.

2In 1992, we selected 10‐year‐old branches. Yearly growth increments (long‐shoots) and emerging buds were individually marked, architectural parameters measured, the branch topology mapped, and the number of male and female cones counted. In 1993, the survival of growth increments and buds was recorded and the branches were harvested to determine dry mass of growth increments and needles.

3The size of growth increments produced after 1989, i.e. their length, total dry mass and needle dry mass, decreased in the order sun branches of edge trees > branches of centre trees > shade branches of edge trees. Thus, the growth increments produced on the shade branches of trees that also had branches in the sun were consistently smaller than the growth increments on the branches of centre trees growing completely in the shade.

4The number of new growth increments produced after 1989 was highest in sun branches and lowest in shade branches of edge trees. Survival of growth increments and buds was higher in edge than in centre trees; no difference was found between sun and shade branches of edge trees.

5In shade branches of edge trees, branching angles between first‐ and second‐order growth increments were highest and increased from older to younger growth increments. This was interpreted as ‘bending’ towards the edge of the patch.

6Production of female cones was almost totally restricted to edge trees and higher in sun than in shade branches.

7One prediction of an optimal foraging strategy, i.e. the production of more growth increments and buds in higher light, was supported by the data, whereas the other prediction, i.e. decreased length of growth increments, could only be supported when it was expressed per unit dry mass. Thus, the hypothesis of an adaptive foraging strategy in plants was rejected in favour of a ‘passive’ growth null hypothesis.

8The results suggest that both growth increments within branches and branches within trees are physiologically integrated and their ‘foraging behaviour’ can only partly be understood in terms of their local environment. We interpreted the observed differences between shade branches of edge and centre trees as correlative growth inhibition.
Reconstruction of long‐term successional dynamics of temperate woodland in Białowieża Forest, Poland
Authors: Mitchell Fraser J. G. , Cole Edwina
Published: March 2003

1 Białowieża Forest contains the most extensive stands of old‐growth temperate woodland in Europe. It therefore has the potential to provide a model for near‐natural woodland, which is a conservation aim for many sites in western Europe.

2 Pollen analyses from two small hollow sites in the northern part of Białowieża Forest National Park are reported here. The records cover the last 1200–1500 years. The pollen data of the principal tree taxa were converted into vegetation data using previously published pollen:vegetation correction factors.

3 These data were used to reconstruct long‐term vegetation dynamics in the Tilio–Carpinetum and Pino–Quercetum communities that dominate the forest. Changes in forest composition have occurred as a result of both autogenic and allogenic processes. High grazing intensities in recent centuries have been particularly significant, although the forest is often considered to be undisturbed.

4 The larger hollow (site I) initially sampled across Peucedano–Pinetum, Carici elongatae–Alnetum and Tilio–Carpinetum communities. Since 1750, the Peucedano–Pinetum community has dominated, but with an increased Picea component. This has recently been replaced by the Pino–Quercetum community following the reduction of grazing pressure. These recent changes are largely consistent with published successional models for Białowieża Forest.

5 Site II recorded a relatively stable balance between the Tilio–Carpinetum and Pino–Quercetum communities until 750 years ago. The Tilio–Carpinetum community then expanded. The continued dominance of Quercus in this community is inconsistent with previous models.

6 The long time perspective available with pollen data permits the exploration of forest dynamics beyond the temporal range of existing models for Białowieża Forest. Comparison of recent and older records revealed that anthropogenic impact on forest composition has been greatest in recent centuries.

7 This investigation highlights the significant role of history in determining forest stand structure and composition.
Experimental demography of the old‐field perennialSolidago altissima: the dynamics of the shoot population
Authors: Meyer Andrea. H. , Schmid Bernhard
Published: March 2003

1Control strategies are needed for the clonal speciesSolidago altissima, which is an aggressive invader in Europe that propagates vegetatively by persistent rhizomes that produce annual shoots.

2The shoot dynamics of a population ofS. altissimathat had invaded an old‐field site in 1984 were studied from 1987 to 1992. Shoots from 120 genets of the same cohort were followed in relation to their parent genets. We assessed the effect of yearly mowing, yearly cutting of rhizomes and repeated removal of close neighbour plants on growth, survival, probability of reproduction and flux of these shoots.

3In unmown plots, both shoot survival until the end of the growing season and the proportion of shoots producing seeds decreased (59% to 36% and 67% to 32%, respectively, from 1988 to 1992). The proportion of rhizomes producing shoots, however, rose (fromc. 50% to more than 90%) so that annual shoot density increased almost fivefold by the end of the study, when it had almost reached equilibrium.

4In contrast, shoot density in mown plots remained roughly constant from 1988 to 1992, after an increase from 1987 to 1988. Shoots were much smaller and a smaller proportion of them reproduced than in unmown plots.

5Rhizome cutting (reduced clonal integration) produced a small but consistent decrease in height and in the percentage of sexually reproducing shoots.

6The removal of close neighbour plants increased shoot density, and a higher percentage of these shoots survived and reproduced.

7Experimental demographic studies thus show that (i) continued regular mowing reduces the production of both seeds and shoots, and so would prevent further spread of an invadingS. altissimapopulation; (ii) clonal integration may contribute to the species’ success as an invader because disconnected rhizomes produce smaller shoots with a lower chance of sexual reproduction; and (iii) competition decreases shoot density, mainly as a consequence of reduced shoot survival, and can therefore controlS. altissimagrowth.
Mast seeding in Abies balsamea, Acer saccharum and Betula alleghaniensis in an old growth, cold temperate forest of north‐eastern North America
Authors: Houle Gilles
Published: March 2003

1 Several hypotheses have been put forward to explain the phenomenon of masting or mast seeding, i.e. the supra‐annual, periodic production of a large number of seeds in long‐lived plants. Some of these hypotheses deal with the proximate causes of masting (e.g. the climate hypothesis) but others are concerned mostly with ultimate, evolutionary explanations (e.g. the pollination efficiency hypothesis).

2 The seed production of three tree species, Abies balsamea, Acer saccharum and Betula alleghaniensis, was followed over a 7‐year period in an old‐growth, cold temperate forest of north‐eastern North America. The main objectives were to determine the extent of interannual variations in seed production, to investigate the relationship between viable and potential seed crop and crop efficiency, and to explore the effects of climate on seed production.

3 Potential and viable seed production varied significantly among years for all three species. However, the timing of dispersal remained the same regardless of the level of seed production.

4 Seed rain was spatially less heterogeneous in years of high seed production, suggesting that most trees were reproducing in such years.

5 Over the 7‐year period, there was a significant concordance among species in their viable seed crop and crop efficiency, but not in their potential seed crop. Crop efficiency was positively correlated to potential seed crop for Abies and Betula, but not for Acer.

6 High seed production was related to warm, dry conditions in the spring of the previous year (i.e. at reproductive bud initiation) but to a moist summer in the year of seed maturation.

7 Masting in these three species thus appears to be controlled by several factors, including climate and pollination efficiency.
Annual growth rings, rainfall‐dependent growth and long‐term growth patterns of tropical trees from the Caparo Forest Reserve in Venezuela
Authors: Worbes Martin
Published: March 2003

1 Tree‐ring analyses and dendrometer measurements were carried out on 37 tree species in a semi‐deciduous forest of the Reserva Forestal de Caparo, Venezuela, where the mean annual rainfall is about 1700 mm and there is a dry season from December to March. The main purposes of the investigation were to show the seasonality of cambial growth, and the connection between precipitation patterns and tree‐ring curves. Long‐term rates of wood increment were also estimated.

2 Cambial markings in consecutive years showed that annual rings were formed by many species.

3 The distinctiveness of growth zones was usually greater in deciduous species than in evergreen species, although not all deciduous species had distinct rings.

4 Dendrometer measurements showed that the annual growth rhythm was related to precipitation patterns. Evergreen species tended to show only a short interruption of wood growth (during the later part of the dry season), whereas deciduous species stopped growth completely at the end of the rainy season.

5 For deciduous species, regression analyses showed close relations between tree‐ring width and the sum of precipitation outside the rainy seasons (i.e. November to April). Evergreen species reacted to the total annual amount of precipitation.

6 Variation in longest available ring chronology (for Terminalia guianensis) showed little correlation with the El Niño–Southern Oscillation effect.

7 On average trees from natural forests showed relatively constant growth over the entire life span. Plantation trees grew fast up to an age of 15–20 years, but annual increments then decreased to values seen in natural forest trees.
Interacting effects of herbivory and fertility on a synthesized plant community
Authors: Fraser Lauchlan H. , Grime J. Philip
Published: March 2003

1 Outdoor microcosms were used to investigate the effects of invertebrate herbivory on plant community composition, and thereby infer possible effects on the rate of secondary succession, at differing levels of soil fertility.

2 A mixture containing 24 grassland plant species of widely different functional types was established, with 12 microcosms at each of three fertility levels. Four generalist herbivores (Helix aspersa, Cepaea hortensis, Arianta arbustorum and Sitobion avenae) were added to half of the microcosms. Above‐ground biomass of each species was harvested after 2 years. Reproductive variables were also measured for one species, Poa annua.

3 At both moderate and high soil fertility generalist invertebrate herbivores fed selectively on early successional, fast‐growing species, thus increasing the relative abundance of later successional, slow‐growing species. This supports the hypothesis that herbivory increases the rate of secondary succession. Flowering and viable seed production of early successional ephemerals was also reduced by the invertebrate herbivores across a wide range of soil fertility. This would seriously reduce the ability of a species to persist in the community, thereby further hastening the rate of succession.
Nutrient foraging traits in 10 co‐occurring plant species of contrasting life forms
Authors: Einsmann Juliet C. , Jones Robert H. , Pu MoU. , Mitchell AndRobert J.
Published: March 2003

1 Responses to spatial heterogeneity of soil nutrients were tested in 10 plant species that differ in life form and successional status, but which co‐occur in the South Carolina coastal plain. The morphological responses of the root system were tested by assessing scale (represented by root mass and root length densities), precision (preferential proliferation of roots in nutrient‐rich patches compared with less fertile patches) and discrimination (ability to detect and proliferate within the richest patches when patches vary in nutrient concentration). We also investigated sensitivity (growth benefits gained as spatial heterogeneity of nutrients increases, measured as total biomass).

2 Ten individuals of each species were grown in pots under four treatments that had differing nutrient distribution but the same overall nutrient addition. Plants were harvested when roots reached pot edge.

3 We observed high variation between species in scale, precision and sensitivity. No significant discrimination responses were observed, although greatest root mass density occurred at intermediate fertility levels for all species.

4 We rejected the hypothesis that scale and precision are negatively correlated. Indeed, in herbaceous species alone, scale and precision were positively correlated.

5 Sensitivity was not closely related to precision, indicating that proliferation of roots in fertile patches does not always yield growth benefits in heterogeneous soils. Further, some sensitive species had very low precision, suggesting that a positive growth response in heterogeneous environments may be related to plasticity in physiology or root life span, rather than morphology.

6 Plant life form was not correlated with precision or sensitivity. However, scale of response was greater in herbs than in woody plants, possibly because the two life forms develop root systems at different rates.
Seed release without fire in Pinus halepensis, a Mediterranean serotinous wind‐dispersed tree
Authors: Nathan Ran , Safriel Uriel N. , Noy‐Meir Imanuel , Schiller Gabriel
Published: March 2003

1 Although serotiny is frequently considered to have evolved under the selective pressure of fires, the drying conditions that induce cone opening are not necessarily associated with fire. We hypothesized that in Pinus halepensis, a Mediterranean serotinous wind‐dispersed tree, xeriscence (seed release induced primarily by drying conditions not generated by fire) bears intrinsic adaptive values, independent of those of pyriscence (fire‐induced seed release).

2 We used seed‐traps to quantify seed release in two scrubland pine stands in Israel. Contemporary meteorological data were used to seek correlations with climatic factors affecting seed release.

3 Substantial seed release, estimated to be about 60% of the annual crop, was observed in the absence of fire. Seed release was distinctly seasonal, with high rates in spring and autumn, and was strongly correlated with short, infrequent but temporally predictable Sharav events (dry and hot weather). In the most extensive Sharav‐induced seed release, seed density reached 117 seeds m–2 and 15% of the annual crop was released within 6 days. Stepwise multiple regression revealed that mean relative humidity (in both stands) and maximum temperature (in one stand) were significant predictors of seed release.

4 Vertical (upwards) wind velocity was significantly positively correlated with dry and hot weather. Seed counts in distant traps (> 20 m from the nearest tree) were significantly greater in periods in which Sharav events occurred than in other periods. Xeriscence may therefore have an adaptive value in promoting dispersal distance by wind.

5 Both xeriscence and pyriscence appear to be involved in determining serotiny in P. halepensis and provide means of exploiting establishment opportunities generated either by fire or by other factors.
Soil pathogenic fungi have the potential to affect the co‐existence of two tallgrass prairie species
Authors: Holah Jenny C. , Alexander Helen M.
Published: March 2003

1 Negative feedback may exist between plant species and their biotic soil communities. Two co‐occurring native tallgrass species (Andropogon gerardii, a perennial grass, and Chamaecrista fasciculata, an annual legume) were reciprocally transplanted into pots containing soil from areas dominated by one of the species. Half of the soil derived from each area was microwaved to reduce soil fungi, resulting in four different ‘soil types’.

2 Chamaecrista fasciculata plants were smaller when grown in their native soil vs. that from under A. gerardii, but were unaffected by microwaving (i.e. fungal reduction). Andropogon gerardii plants were shorter with fewer inflorescences in non‐microwaved soil, with the poorest growth occurring in non‐microwaved C. fasciculata soil.

3 Fungi were isolated from roots of A. gerardii growing in the different soil types. We tested whether the fungi found differed between the four soil types and whether any species characteristic of C. fasciculata soil were responsible for the poor growth of A. gerardii in this medium.

4 Fungi unique to the non‐microwaved C. fasciculata soil type reduced tillering and caused an early reduction in growth of A. gerardii. These effects were partially ameliorated when potentially mycoparasitic fungi associated with A. gerardii were also included. By the end of the experiment, both fungal treatments increased above‐ground biomass but greatly reduced below‐ground biomass of A. gerardii compared with controls, suggesting that the exposure to potential fungal pathogens from C. fasciculata soil altered biomass allocation within plants.

5 There was no evidence of negative feedback between the prairie species and their own soils. However, fungi associated with Chamaecrista fasciculata were detrimental to A. gerardii, one of the dominant perennials in the surrounding area, and may facilitate the annual’s long‐term persistence. Arbuscular mycorrhizae did not ameliorate the pathogenic effects of these fungi as there was little colonization of A. gerardii roots in C. fasciculata soil.
Effect of light on the germination of forest trees in Ghana
Authors: Kyereh B. , Swaine M. D. , Thompson J.
Published: March 2003

1  Seed germination in light and dark, and responses to irradiance and light quality, were tested in shadehouse experiments for 19 West African tropical forest tree species representing a wide range of ecological types. Germination in forest gaps of different size was tested for 11 species.

2
 Percentage germination was reduced in the dark only for three small‐seeded species that are common in forest soil seed banks: Musanga cecropioides, Nauclea diderrichii and Milicia excelsa. Percentage germination of the other 16 species, including four widely regarded as ‘pioneers’, was unaffected.

3  Effects of different irradiances in shadehouses, where the seeds were watered, were significant for some species, but there was no consistent pattern. Irradiance effects in forest gaps, where the seeds received only natural wet season rainfall, were more widespread and substantial, and were most commonly shown as a depression of percentage germination at high irradiance.

4
 Effects of light quality (neutral vs. green shade; red : far‐red = 0.43) were insignificant at 5% irradiance in shadehouses for all species except Nauclea diderrichii. In growth chamber experiments, the low energy response was only evident at 1.0 µmol m–2 s–1 (< 1% of unshaded forest irradiance) in Musanga and Nauclea.

5  The speed of germination was affected by irradiance in many species, but the effect was small compared with differences between species, in which time to complete germination varied between 3 weeks and over 6 months.

6
 Seeds of Ceiba pentandra and Pericopsis elata planted in deep forest shade (2% irradiance) and in a small gap (30% irradiance) germinated well in both sites, showed exponential biomass growth in the gap but a linear decline in mean seedling biomass and subsequent death in deep shade.

7  Light‐mediated germination is relatively rare among these forest trees, even among pioneers, so that the working definition of a pioneer should be seen to depend more on a species’ ability to survive in forest shade. The effects of canopy opening on seed germination are small except in the largest openings, which severely depress germination in a number of species, including some species with strongly light‐demanding seedlings.
Fire, resprouting and variability: a recipe for grass–tree coexistence in savanna
Authors: Higgins Steven I. , Bond William J. , Trollope Winston S. W.
Published: March 2003

1 Savanna ecosystems are characterized by the codominance of two different life forms: grasses and trees. An operational understanding of how these two different life forms coexist is essential for understanding savanna function and for predicting its response to future environmental change.

2 The existing model, which proposes that grasses and trees coexist by a separation of rooting niches, is not supported by recent empirical investigations. Our aim was to define an alternative mechanism of grass–tree coexistence in savanna ecosystems. The model we have built concentrates on life history–disturbance interactions between grasses and trees.

3 The model demonstrates coexistence for a wide range of environmental conditions, and exhibits long periods of slow decline in adult tree numbers interspersed with relatively infrequent recruitment events. Recruitment is controlled by rainfall, which limits seedling establishment, and fire, which prevents recruitment into adult size classes. Decline in adult tree numbers is the result of continuing, but low levels, of adult mortality. Both aspects of the dynamics are consistent with an established non‐equilibrium mechanism of coexistence (the storage effect).

4 A sensitivity analysis indicated that data on tree resprouting ability, stem growth rates and the relationship between seedling establishment and wet season drought are essential for predicting both the range of conditions for which coexistence is possible and the response of savanna ecosystems to environmental change.

5 Our analysis suggests that understanding grass–tree interactions in savanna requires consideration of the long‐term effects of life history–disturbance interactions on demography, rather than the fine‐scale effects of resource competition on physiological performance.
The effect of initial density on interactions between bryophytes at individual and community levels
Authors: Zamfir Manuela , Goldberg Deborah E.
Published: March 2003

1 A glasshouse experiment was conducted with seven bryophyte species to determine the effects of competition. We tested whether competitive hierarchies varied with initial abundance (density and biomass) and between two different experimental approaches.

2 Relative competition intensities were calculated based on proportional growth (G) and relative biomass (R). The standards for comparison (i.e. no interactions) were species’ performance in monocultures at one of two sowing abundances (the combined monocultures method; CM) and in a low‐density mixture of equal proportions of all species (the community density series method; CDS).

3 Proportional growth decreased with increasing initial abundance for all species. Community effects (relative biomass of each species) were generally weaker and more variable than individual effects. R increased linearly with abundance for only one species, while three species showed a quadratic response (of which two were negative).

4 Competitive hierarchies derived by the CM method differed with abundance, and we argue that the CDS method is likely to provide a more reliable comparison.

5 With CDS, competitive hierarchies were similar along the community abundance gradient, implying that non‐linear competitive effects are not likely to be a mechanism of coexistence in this community.

6 There were significant competitive effects on community composition, but not on diversity as measured by evenness. At the community level individual species tended to show either competitive or positive effects throughout the gradient of initial community abundance, with decreasing values for most species at high initial community abundance, as were the effects of interactions on community composition.
Recruitment dynamics of a fleshy‐fruited plant (Olea europaea): connecting patterns of seed dispersal to seedling establishment
Authors: Rey Pedro J. , Alcántara Julio M.
Published: March 2003

1
 Little is known about the consequences of seed‐disperser activity for plant demography. We compared the spatial patterns of seed dispersal generated by frugivorous birds with those of seedling survival for the shrub Olea europaea. We examined the relative importance of dispersal in determining plant recruitment and tested whether the initial dispersal pattern persisted throughout recruitment.

2  We quantified the processes affecting each stage of regeneration (seed within a ripe fruit, dispersed seed, seedling and sapling) in different microhabitats, and evaluated transition probabilities between stages. We could then determine the overall probability of a seed in a ripe fruit becoming a sapling, and compare the probability of such an event occurring in different microhabitats.

3  Only 9.3% of the emerged seedlings reached the sapling stage, whereas 35.3% of the seeds were dispersed; 27.0% of dispersed seeds produced seedlings and 62.9% of saplings survived for 2 years. Seedling survival was therefore the critical link in regeneration. Water stress was responsible for more than 70% of seedling losses, which suggests that abiotic factors (mainly rainfall) may account for most of the fluctuation in recruitment in this species.

4  Neither post‐dispersal seed predation nor germination caused changes in the initial spatial distribution of seeds, but differences in the requirements of seeds and seedlings then caused spatial uncoupling. The most favourable places for seeds were the worst for seedlings, and consequently frugivore‐generated dispersal patterns differed from the final spatial pattern of recruitment.

5  Recruitment under conspecifics was nearly zero and dispersers are therefore crucial if recruitment is to occur. Their effect on the amount of recruitment was, however, overwhelmed by processes acting on the seedling stage.

6
 For Olea europaea, the pattern generated by short‐term recruitment dynamics persists in the long‐term spatial distribution of saplings.
Quantitative aspects of community structure examined in a semi‐arid grassland
Authors: Wilson J. Bastow , Steel John B. , Newman James E. , King Warren MCG.
Published: March 2003

1 Community structure was examined by analysing the spatial distribution of species' biomass–abundance, as well as species' occurrences, in two semi‐arid grassland sites in New Zealand. This is the first attempt to search for a range of assembly rules (variance in species occurrence, guild proportionality and intrinsic guilds) using quantitative data.

2 One site, with a greater proportion of native species, had a larger species pool, greater species richness and greater biomass. At this site, variance in richness was generally greater than expected at random, but variance in biomass tended to be less than expected at random, probably indicating competition. Microsites which had lower biomass and fewer species tended to be dominated by exotic species; it is suggested that these are more recently disturbed microsites.

3 At a second site, dominated by exotic species, there was no significant evidence for community structure, i.e. no non‐random patterns in richness or biomass, i.e. no assembly rules.

4 Guild proportionality was not seen in a priori guilds: dicots, monocots, cryptogams, native species and exotic species.

5 Searches for intrinsic guilds produced no evidence of guild structure, in the Pianka sense of groups of species that use similar resources, compete strongly with each other, and thus are especially subject to mutual competitive exclusion.

6 It is concluded that interspecific competition limits the biomass of each species in these grasslands, but there is no evidence from the community structure that it causes local competitive exclusion. There was no indication at either site that the communities were structured by guilds. It is concluded that, at least at the scale examined and at the time examined, Pianka‐type guilds do not exist in this vegetation.
Climatic control of blanket mire development at Kentra Moss, north‐west Scotland
Authors: Ellis Christopher J. , Tallis John H.
Published: March 2003

1 Four peat cores were collected from Kentra Moss, north‐west Scotland, and analysed for botanical macrofossils and peat humification. The pollen record was used as a template for the identification of synchronous levels between cores.

2 A non‐random pattern of change in bryophyte macrofossils and humification was simultaneous between all four cores. Stratigraphic changes occurred independently of human land‐use and were best interpreted as palaeoclimatic events. Remains of Racomitrium lanuginosum and Sphagnum papillosum, in conjunction with changes in peat humification, provided the clearest indication of past increases in climatic wetness (‘wetshifts’) to impact upon mire hydrology and ecology.

3 Eight wetshifts were identified and radiocarbon‐dated, beginning at c. 3250, 2550, 2150, 1400, 1150, 875, 600 and 325 calibrated years BP (cal. BP). Seven of these wetshifts match closely with palaeoclimatic events from a range of mires previously examined in Britain and Ireland. We suggest that blanket mires may provide the best source of decade‐ to century‐scale palaeoclimatic information in oceanic north‐west Europe.

4 The proxy‐climatic evidence indicates that: (i) the extinction of Sphagnum imbricatum at Kentra Moss (at c. 1400 cal. BP) was caused by an increase in climatic and mire surface wetness, when it was replaced first by Racomitrium lanuginosum and then by Sphagnum papillosum; and (ii) that increased climatic wetness and human land‐use were responsible for the shift from an early minerotrophic peatland to ombrotrophic blanket mire at c. 4070 cal. BP.

5 Given the evidence for a prevailing climatic effect on the development of Kentra Moss, the effect of human‐induced global warming on Britain's blanket mire resource will probably be significant. British blanket mires have international conservation status, and future changes in their ecology will challenge conservationists, academics and politicians.
Post‐dispersal fate of seeds in the Monte desert of Argentina: patterns of germination in successive wet and dry years
Authors: Marone Luis , Horno Manuel E. , Solar Rafael González Del
Published: March 2003

1 Patterns of seed germination of grass and forb species were studied in open Prosopis woodland of the central Monte desert (Argentina) during several years, to test the hypotheses that (i) seed germination is positively affected by both rainfall and protection afforded by vegetation cover (a facilitative effect), (ii) the number of surviving plants is positively influenced by rainfall but negatively affected by established vegetation (a competitive effect), and (iii) seed loss from soil banks owing to germination is lower than that caused by granivorous animals.

2 Forb species germinated during restricted periods, either in early autumn or in spring. Grasses, however, germinated throughout the growing season, but because seedlings could not be identified to species level, it was impossible to discern whether different species germinated in particular seasons, or if all grasses germinated in all seasons. Grass and forb germination were generally of similar magnitude, but grass germination increased by an order of magnitude during a summer of unusually abundant rainfall related to an El Niño Southern Oscillation (ENSO) event.

3 Overall, the spatial distribution of neither germinating seeds nor surviving plants could be explained by interactions with established vegetation (facilitation and competition effects, respectively). An alternative explanation may be provided by the distribution of forb and grass seeds in the soil.

4 Seed loss owing to germination was low in both dry and rainy years. For forbs, such loss totalled < 1% of soil‐seed reserves, and no forb species suffered losses > 4%. Total grass‐seed loss to germination was usually < 0.5%, and the 5% reached in 1997–98 corresponded to an interruption of a prolonged drought by unusually abundant rainfall associated with a reduced seed bank.

5 Grass‐seed loss caused by germination was one to two orders of magnitude lower than that reported due to autumn‐winter granivory in the central Monte desert.
Seedling emergence, survival and size in relation to light and water availability in two bottomland hardwood species
Authors: Battaglia L. L. , Foré S. A. , Sharitz R. R.
Published: March 2003

1 Windstorm disturbances create a wide range of microsites which can have complex effects on forest regeneration patterns. We investigated the combined effects of light and microtopography on emergence, mortality and size of seedlings of two bottomland hardwood canopy tree species, Quercus michauxii and Liquidambar styraciflua, over a 2‐year period. A split‐plot design in experimental tanks represented the range of light levels and the pits and mounds found in a disturbed floodplain forest.

2 Emergence was always higher on mounds than in pits, except for L. styraciflua in full sunlight. For both species, mortality was consistently lower, and seedlings of both species grew better in both years on mounds. Light levels did not affect the two later stages.

3 There were species‐specific interactions between the effects of two factors on seedling emergence. Lower emergence of L. styraciflua on mounds in full sunlight suggested that full sunlight at this stage can eliminate the advantage to later stages of being on a mound. The combined stresses of low light and a high water table significantly reduced emergence of Q. michauxii in pits at low light.

4 Microsites optimal for one regeneration component of a species were not always optimal for others as seen for L. styraciflua. The relative significance of environmental factors also varied with regeneration stages, such that neither light nor a light‐water interaction influenced regeneration after emergence.

5 Environmental factors may have independent or interacting effects on regeneration, and the nature or presence of these effects can vary among demographic stages. Within each environmental combination, effects may be consistently positive or negative across stages; alternatively, demographic conflicts may develop.
Effects of global change on a sub‐Arctic heath: effects of enhanced UV‐B radiation and increased summer precipitation
Authors: Phoenix Gareth K. , Gwynn‐Jones Dylan , Callaghan Terry V. , Sleep Darren , Lee John A.
Published: March 2003

The responses of sub‐Arctic heathland vegetation to enhanced UV‐B radiation and increased summer precipitation over 7 years were investigated in a field experiment in northern Sweden.

Growth, phenology and reproduction of the dominant dwarf shrubs Vaccinium myrtillus, V. uliginosum, V. vitis‐idaea and Empetrum hermaphroditum were studied after 5–7 years of manipulation and retrospective analyses were used to assess growth responses in earlier years. Leaf tissue N and P and 13C natural abundances were determined for V. myrtillus and E. hermaphroditum. Growth responses were also assessed for the moss Hylocomium splendens.

The deciduous V. myrtillus showed reduced growth, increased leaf thickness and increased flowering and berry production under enhanced UV‐B in some years. V. uliginosum, V. vitis‐idaea, E. hermaphroditum and H. splendens were, in general, tolerant of UV‐B.

Increased precipitation affected growth only in the evergreen species: stem length and branching were sometimes stimulated in E. hermaphroditum, whereas V. vitis‐idaea showed reduced branching.

Precipitation also increased leaf thickness in V. uliginosum and reduced flowering and berry production in V. myrtillus.

In the interactions that occurred between enhanced UV‐B radiation and increased summer precipitation, combining the two treatments often negated any effect that either may have had separately. The effect of concurrent increases on this ecosystem is therefore likely to be much less than if either occurred singly.

Enhanced UV‐B and increased summer precipitation appeared not to effect dwarf shrub abundances during the first 5 years of the experiment, suggesting that overall this heath may be more tolerant of these environmental changes than previously thought.
The influence of fire on the demography of a dominant grass species of West African savannas, Hyparrhenia diplandra
Authors: Garnier Lisa K. M. , Dajoz Isabelle
Published: March 2003

Effects of fire on the demography of a population of a long‐lived perennial tussock grass, Hyparrhenia diplandra, were investigated in a West African savanna that normally burns annually. Seedling growth, survival and fecundity were recorded in burned and unburned plots during 3 years for a first cohort and during 1 year for a second cohort initiated 1 year later.

Seedling growth and survival rates were significantly higher in unburned plots, with larger seedlings surviving burning better. Regardless of treatment/fire regime, seedlings grew faster when located further from the nearest tuft, but differences between clones showed that growth rate also had a genetic basis in this apomictic species. Adult survival was always high, but exclusion of fire increased size, and therefore age, at maturity. Fire therefore affects life‐history traits in this grass species of fire‐prone environments.

Size‐structured matrix models were constructed separately for each fire treatment, incorporating demographic and fire parameters estimated from field data.

The asymptotic population growth rate was higher in the unburned model (λ = 1.23) than in the burned one (λ = 1.07), indicating that the population of H. diplandra expanded quickly in the absence of fire.

Overall, results indicate that annual burning limits population growth rate. Less frequent, but still regular fires may allow establishment while preventing the accumulation of litter and accelerating nutrient recycling; thus lead to more stable populations than in the total absence of fire.
Storage and the delayed costs of reproduction in the understorey perennial Lathyrus vernus
Authors: Ehrlén Johan , Van Groenendael Jan
Published: March 2003

A trade‐off between current and future reproduction, often referred to as the cost of reproduction, is a fundamental assumption in life history theory. In long‐lived plants, large absolute differences in size between individuals, storage of resources between reproductive events and organ preformation may make such costs difficult to demonstrate, especially when only natural variation is considered.

The long‐lived legume Lathyrus vernus shows large size differences compared with variation in carbon resource allocation, and is known to store resources in below‐ground rhizomes. We therefore followed individual plants over a period of 4 consecutive years. We examined the cost of reproductive investment by comparing the performance of untreated plants that differed in size and herbivore damage. We also compared controls with plants where we experimentally reduced flowering in terms of fitness measured as: survival, growth, flower number, fruit:flower ratio and storage.

Natural patterns of flowering and fruiting provided no evidence of a negative relationship between current and future reproduction. Individuals that produced fruits did not experience a lower probability of surviving and producing fruits the following season compared with flowering individuals that failed to produce any fruits, even when differences in above‐ground size and herbivore damage were taken into account.

Flower removal in a single season increased the allocation to the rhizome but the size of shoot buds for the next season was not increased. Experimental manipulation of reproductive effort by repeated removal of flowers during 3 consecutive years, however, resulted in a significant increase in vegetative size and the probability of flowering and setting fruit compared with control plants.

While long‐term data on natural variation in fruit production and short‐term experimental data provided no evidence of a cost of reproduction, such a cost is still present, although detectable only after repeated flower removal.