bluuebunny/crossref_metadata_2025_split huggingface dataset:
The relative contributions of sexual reproduction and clonal propagation in Opuntia rastrera from two habitats in the Chihuahuan Desert
Authors: Del Carmen Mandujano María , Montanā Carlos , Méndez Ignacio , Golubov Jordan 
Published: March 2003

1 The clonal cactus Opuntia rastrera shows predominantly sexual reproduction in grasslands (GH) and clonal propagation in nopaleras (NH). We assessed the effects of light, herbivory, water availability and the habitat an offspring came from on the survival and growth of sexual or clonal offspring (i.e. seedlings and cladodes), through 3‐ and 4‐year common garden and short‐term greenhouse experiments. 2 Shading by nurse plants increased seedling survival in the field by an order of magnitude, and a small additional advantage due to predator protection by grasses was observed. Strong herbivory transforms a facultative nurse–protégé relationship for seedlings into an obligatory one. 3 In the greenhouse seedlings grew better under shade, but in the field the production of the first cladode was delayed in seedlings in the more shaded GH. Competition for soil resources may be more intense under a dense grass tussock than under a open shrub, thus affecting the nurse–protégé relationship. Seedling survival under nurse plants was similar in GH and NH, but higher plant cover suggests that a larger number of seedlings will establish in GH in the long term. 4 Cladode survival was higher in NH. Cladodes were more successful than seedlings at establishing in intercanopy areas, possibly due to physiological differences as well as their ability to survive partial predation. Cladode survival in intercanopy areas may explain the enhanced clonal propagation in the more open NH scrubland, together with their susceptibility to the flooding which affects GH. 5 The high seedling and cladode survival in the greenhouse experiments contrasted with that observed in the field, indicating that survival is determined by the interaction between herbivores, plants and abiotic conditions rather than the physiological aptitude of the plants.
A 6000‐year soil pollen record of subalpine meadow vegetation in the Olympic Mountains, Washington, USA
Authors: Gavin Daniel G. , Brubaker Linda B. 
Published: March 2003

1 Subalpine meadow communities are influenced by edaphic and microclimatic gradients, and should be affected by climate change that affects these local controls. We used pollen preserved in meadow soils to investigate the long‐term interaction of these factors in a 1‐ha subalpine meadow in the Olympic Mountains, Washington, USA. 2 To describe the spatial scale at which soil pollen is related to neighbouring vegetation, pollen in 46 soil surface samples was compared with plant cover within concentric circular plots (0.5–1 m radii). Regression analysis of percentage pollen with plant cover at different distances from the surface sample had the highest correlation with radii < 1 m, confirming that entomophilous meadow species have very small relevant pollen source areas. 3 We analysed pollen records in soil columns at three sites representing a range of growing season lengths and community types within the meadow. Soils had aggraded by the deposition of eolian silt. Radiocarbon dates of pollen concentrates were similar to or older than radiocarbon dates on charcoal pieces at the same depth, suggesting negligible downwards movement of pollen in the soil profile. 4 The oldest soil pollen profile was from the wettest microsite, currently dominated by a snowbed Carex nigricans community. This site was occupied by a dry Juniperus community prior to c. 6000 bp (before present), when it shifted to more mesic communities dominated by Poaceae and Polemonium. The first appearance of a snowbed Carex nigricans community at this site, c. 2500–1500 bp, suggests a change to cooler and/or wetter regional climate. 5 High levels of Polygonum bistortoides at all sites indicated a shift to long snow‐free periods and mesic summer conditions during an interval corresponding to the Medieval Warm Period (c. 1200–700 bp). After 500 bp (during the Little Ice Age) Carex nigricans re‐established in the wet microsite, while relatively little change occurred at the other two sites. Overall, the greater magnitude of change at this microsite than at the longer growing‐season sites indicates that, in these subalpine meadows, short growing season sites are most sensitive to regional climate change.
Effects of habitat fragmentation on choke disease (Epichloë bromicola) in the grass Bromus erectus
Authors: Groppe Kathleen , Steinger Thomas , Schmid Bernhard , Baur Bruno , Boller Thomas 
Published: March 2003

Summary

The fungal endophyte Epichloë bromicola causes choke disease on Bromus erectus, thereby suppressing maturation of host inflorescences. We conducted a 3‐year field experiment to investigate the effects of small‐scale habitat fragmentation on the occurrence of choke disease in three calcareous grasslands in the Swiss Jura Mountains, where, overall, 4.3% of all flowering tillers had diseased inflorescences.
The number of diseased B. erectus plants (presumed genets), the number of tillers with diseased inflorescences, and the number of tillers with healthy inflorescences were counted over 3 years, but healthy tillers could not be allocated to particular genets. Each of 12 blocks contained one large (4.5 × 4.5 m), one medium (1.5 × 1.5 m) and two small (0.5 × 0.5 m) fragments and corresponding control plots. The percentage of tillers in the plots that were infected but did not show disease symptoms (asymptomatic plants) was estimated in the final year of the study using a diagnostic polymerase chain reaction. On average 1.7% of all tillers without disease symptoms were infected.
There were significantly more diseased plants in fragment than in control plots, particularly in small fragment plots or in the third year of the study, indicating that disease incidence in the host plant increased after fragmentation if assessed at the level of the genet population. This was probably due both to a switch of genets from the asymptomatic to the symptomatic state and to increased horizontal transmission of the disease in fragments.
The increase in the number of flowering tillers with diseased inflorescences was outweighed by that in the number of tillers with healthy inflorescences. Disease incidence was therefore decreased by fragmentation if assessed at the level of the host flowering tiller population. The effect on healthy plants was probably due to beneficial abiotic edge effects following fragmentation.
Plot size affected fragmentation response, with the largest increases in small, followed by medium and large fragments. Similarly, the strength of fragmentation responses increased through time over the 3‐year study period.
Significant site to site and year to year variation in the number of diseased plants and in the number of tillers with diseased inflorescences suggested that separate experiments with replication within site and year would have yielded a series of interesting but individually different results. Only by repeating the experiments at several sites and over several years was it possible to obtain the general results reported in the previous points.
Inferring landscape dynamics of bog pools from scaling relationships and spatial patterns
Authors: Belyea Lisa R. , Lancaster Jill 
Published: March 2003

Summary1 On many peatlands, a patterned landscape is formed by clusters of open‐water pools enclosed by the peat of surrounding terrestrial and semi‐aquatic habitats. Processes governing development of pool complexes operate over long time‐scales (decades to millennia) that preclude direct observation and necessitate inferential analysis.2 We used present‐day scaling relationships and spatial patterns of pools to test multiple hypotheses for development and dynamics of a bog pool complex in the Flow Country of northern Scotland. The complex included 641 permanent pools, ranging in surface area from 2.3 to 1930 m2.3 Allometric scaling relationships and spatial analysis showed that the shape and distribution of pools is size‐ (or age‐) dependent. With increasing size, pools became deeper relative to their surroundings and more convoluted and elongated in shape. Pool orientation and bathymetry were related to direction of slope. Small pools were located on the periphery of a focus now occupied by the largest pools. Peat depth varied systematically across the complex, leading to changes in both direction and gradient of water flow.4 The evidence suggests that pools formed initially where water tended to pond, and subsequently spread outward as the flat plateau expanded. Pools have accumulated sediment more slowly than surrounding areas, and the continued initiation of new pools seems to depend on this spatial variation in rates of sediment accumulation. Our study provides both a fuller understanding of the development of one pool complex, and techniques for comparative analysis of others.
The effects of fertilization and herbivory on the herbaceous vegetation of the boreal forest in north‐western Canada: a 10‐year study
Authors: Turkington Roy , John Elizabeth , Watson Sally , Seccombe‐Hett Pippa 
Published: March 2003

Summary1 The influence of fertilizer addition and mammalian herbivore exclosures (a 2 × 2 factorial design, with four replicates at each of two sites) on the cover, species composition and diversity of the understorey vegetation of the boreal forest in the south‐western Yukon, Canada, were investigated from 1990 to 1999. This was done to test whether vegetation composition was controlled by resource level alone (bottom‐up control), herbivory alone (top‐down control), or by both (interactive control).2 The density of the major herbivore, the snowshoe hare, varied 25‐fold, declining from 148 km−2in 1990 to 8 km−2in 1994, and increasing to a second peak of 198 km−2in 1998.3 In control plots most species were remarkably constant in percent cover. After 10 years, most of the major species showed significant responses to fertilizer with four species increasing (Festuca altaica,Mertensia paniculata,Epilobium angustifolium, andAchillea millefolium), and three declining (Linnaea borealis,Lupinus arcticus,Arctostaphylos uva‐ursi). Some species took up to 5 years before a response was detected.4 Fertilization caused (i) a decline in the number of species, and species evenness in the community, (ii) a reduction in the proportion of woody species, and (iii) an increase in herbaceous dicotyledons and grasses.5 The exclusion of herbivores had virtually no impact on the abundance of the vegetation or on species diversity, except in 1990–92 during a decline from a peak of 148 hares km−2to 29 hares km−2.6 These results suggest that the percentage cover and composition of herbaceous vegetation in the boreal forest are determined almost exclusively by the productivity of the site (bottom‐up control) and that the activities of mammalian herbivores may be important only during peaks in hare population densities (interactive control).7 Results were both species‐specific and time‐dependent, suggesting that long‐term studies are needed to discriminate between long‐term responses to treatments and transient phenomena.
A spatial model of coexistence among three Banksia species along a topographic gradient in fire‐prone shrublands
Authors: Groeneveld J. , Enright N. J. , Lamont B. B. , Wissel C. 
Published: March 2003

Summary

A spatially explicit, rule‐based model for three co‐occurring Banksia species was developed to investigate coexistence mediating processes in a fire‐prone shrubland in western Australia. Fecundity, recruitment, mortality and other biological data for two non‐sprouting (B. hookeriana, B. prionotes) and one resprouting (B. attenuata) species were available from 15 years of empirical field studies.
Without interspecific competition, each species could persist for a wide range of fire intervals (10 to > 20 years). The resprouting species performed better under shorter fire intervals (10–13 years), while both non‐sprouting species were favoured by longer (15 to > 20 years) fire intervals. These results conform with those obtained from single‐species, non‐spatial population models.
When interspecific competition for space was included in the model, all three species exhibited optima at shorter fire intervals and with a narrower range than in isolation. The three species did not co‐occur under any fire regime. At intermediate fire frequencies (11–13 years), B. hookeriana excluded the other species, while for longer intervals between fires B. prionotes became dominant.
The introduction of temporal (stochastic) variability in fire intervals (drawn from a normal distribution) failed to produce coexistence, unless spatial variability as a spatial ignition gradient was also included. The spatial arrangement of the non‐sprouters observed in the field was then reproduced.
Observed patterns of coexistence and spatial distributions of all species occurred when a spatial establishment gradient for the resprouter species was included in the model (individuals of B. attenuata are known to produce more seeds in swales than on dune crests and recruit seedlings here more frequently).
Coexistence appears to be highly dependent upon the mean interfire period in combination with subtle gradients associated with fire propagation and recruitment conditions. Variation around the mean fire interval is less critical. When the system is modelled over a long time period (1500 years) coexistence is most strongly favoured for a narrow window of mean fire intervals (12–14 years).
The effect of maternal phenology on offspring characters in the herbaceous plantCampanula americana
Authors: Galloway Laura F. 
Published: March 2003

SummaryAn individual's phenotype may influence the expression of traits in its offspring. I tested whether maternal flowering phenology influenced offspring germination and thus life history schedule in two populations ofCampanula americana. Autumn‐germinatingC. americanagrow as annuals whereas individuals that germinate in the spring are biennials.Under near‐natural conditions, early‐season flowers produced seeds that were more likely to germinate in the autumn than late‐season flowers, but spring germination was equally likely for all seeds.Seed mass (two of three years) and percentage and timing of germination under constant environmental conditions (all three years) did not vary across the reproductive season. External environmental factors are therefore more likely to contribute to seasonal changes in the probability of germinating in the autumn than are the characteristics of the seeds.The frequency of annual offspring varied among maternal plants. The association between the time a flower was open and offspring germination season suggests that evolution of life history schedule may be accomplished by altering maternal flowering phenology.The association between the time of a flower's anthesis and its fruit maturation was weaker in two years when water was limiting. Limited water also resulted in earlier seed maturation, and consequently a greater proportion of a population's seed being produced during the period when autumn germination was likely. This, in combination with differences between populations, suggests that the magnitude of maternal phenological effects varies across years and populations.
Principles to govern clinical governance
Authors: Onion Carl W. R. 
Published: March 2003

AbstractClinical governance – a new NHS concept that seeks, through clinical guidelines and national service frameworks, to encourage and enforce com‐pliance with nationally‐devised evidence based clinical policies – has manifold and complex implications. This paper reasons that clinical governance is actually a means to promote excellent practice of a particular kind and that non‐compliance does not necessarily equate to bad practice. Therefore, separate means must be utilized to address bad practice. The paper proposes and supports in turn a series of principles to ensure that the potential benefits of clinical governance are maximized and the potential harms are diminished. A similar set of principles is proposed to help govern the management of bad practice. The complementary conclusions of the reasoning are that a) doctors should willingly embrace clinical governance and b) the NHS should not rigidly enforce it. However, as clinical governance restricts clinical freedom and patient choice it is important that ethical principles, such as those proposed, are followed in order to avoid or manage some unhappy conflicts.
Effectiveness of educational interventions on the improvement of drug prescription in primary care: a critical literature review
Authors: Figueiras Adolfo , Sastre Isabel , Gestal‐Otero Juan Jesus 
Published: March 2003

AbstractThis paper is a critical review of studies of educational programmes designed to improve prescription practices in ambulatory care. Scientific articles were selected from the following bibliographical indices: MEDLINE, IME, ICYT and ERIC. The searches covered the time period between 1988 and 1997. The search criteria included: primary‐care, educat*, prescription* and other related keywords. The inclusion criteria were studies describing educational strategies aimed at general practitioners working in ambulatory settings. The study outcome was change in prescribing behaviour of physicians through prescribing indicators. The following data were extracted: study design, target drugs, type of intervention, follow‐up period of the prescription trends, type of data analysis, type of statistical analysis and reported results. We found 3233 articles that met the search criteria. Of these, 51 met the inclusion criteria and 43 studied the efficacy/effectiveness of one or various interventions as compared to no intervention. Among seven studies evaluating active strategies, four reported positive results (57%), as opposed to three of the eight studies assessing passive strategies (38%). Among the 28 studies that tested reinforced active strategies, 16 reported positive results for all variables (57%). Eight studies were classified as a high degree of evidence (16%). We concluded that the results of our review suggest that the more personalized, the more effective the strategies are. We observe that combining active and passive strategies results in a decrease of the failure rate. Finally, better studies are still needed to enhance the efficacy and efficiency of prescribing practices.
Physicians’ attitudes towards voluntary reporting of adverse drug events
Authors: Figueiras Adolfo , Tato Fernando , Fontaiñas Jesus , Takkouche Bahi , Jesus Gestal‐Otero Juan 
Published: March 2003

AbstractAt the time a new drug is placed on the market, information on its therapeutic effect and toxicity is limited. Because of its simplicity and widespread use, the voluntary reporting by clinical physicians is the main method for detecting rare or unexpected adverse drug events (ADEs). However, the usefulness of this method may be compromised if the reporting rate is low. We present the results of a questionnaire‐based case‐control study carried out among 692 physicians from Galicia (north‐west region of Spain), in which we assessed their attitudes and opinions towards ADEs. In general, the Galician physicians think it is difficult to link a given ADE with a drug (P < 0.05) and have very heterogeneous opinions on the fact that very severe ADEs are known before the drug is commercialized. They globally disagree with the proposal that ADE reporting should be remunerated and the fact that ADE reporting can be risky for the physician. Some of the beliefs concerning ADEs are incorrect. It is crucial to improve the training of the physicians through active educational strategies based on personal contact.
Age period cohort analysis of time trends in regional mortality rates in England, Wales and Scotland
Authors: Robertson Chris , Ecob Russell 
Published: March 2003

AbstractPrevious studies have demonstrated regional variation in mortality rates, this reducing for younger but not older individuals. However, it has not been clear from such studies whether or not the overall findings can or cannot be attributed to particular regions that may have abnormal patterns of change over time. We analyse mortality rates by region using data from the census years from 1931 until 1991 for adults. Age period cohort models, based on the local ‘curvatures’, are used to describe the changes in the rates. We also use estimable contrasts to compare the later periods with the earlier periods and to compare pre‐ and post‐war cohorts. There is strong evidence that the changes in the mortality rates are associated with non‐linear period and cohort effects. There is no evidence that these curvatures vary over regions. There is evidence that the curvatures are not the same among men and women. Among women there is evidence that there is a change in trend in the periods from 1961 to 1991 compared with the trend in the earlier periods from 1931 to 1951, such that the reduction in the mortality rates with time are slowing down for women. Among men who had higher mortality rates, there is not so much evidence of a slowing down of the reduction. Post‐war cohorts of women from 1941 onwards are enjoying a reduction in mortality compared with the cohorts from 1901 to 31, while among men there is no evidence of a change in mortality trends among younger cohorts. Changes in the mortality rates over regions have come about from different long‐term temporal trends in the regions rather than abrupt changes taking place at different times in different regions. The general convergence of mortality rates over regions over time with a consequent reduction in regional variance is masked by two regions, Scotland and East Anglia. These regions appear to differ from the regions as a whole in the relationship of mortality to age at a given period and in the reduction of mortality over time (drift), Scotland having a higher mortality, especially at younger ages, and lower downward trend, and East Anglia vice versa.
Evaluation of chloroquine as a potent anti‐malarial drug: issues of public health policy and healthcare delivery in post‐war Liberia
Authors: Massaquoi Moses B. F. , Kennedy Stephen B. 
Published: March 2003

AbstractChloroquine‐resistant plasmodium falciparum malaria is a serious public health threat that is spreading rapidly across Sub‐Saharan Africa. It affects over three quarters (80%) of malarial endemic countries. Of the estimated 300–500 million cases of malaria reported annually, the vast majority of malarial‐related morbidities occur among young children in Africa, especially those concentrated in the remote rural areas with inadequate access to appropriate health care services. In Liberia, in vivo studies conducted between 1993 and 2000 observed varying degrees of plasmodium falciparum malaria infections that were resistant to chloroquine, including sulfadiazine‐pyrimethamine. As the country emerges from a prolonged civil war, the health care delivery system may not be adequately prepared to implement an effective nation‐wide malarial control strategy. As a result, the management of uncomplicated malaria in Liberia poses a significant public health challenge for the government‐financed health care delivery system. Therefore, based on extensive literature review, we report the failure of chloroquine as an effective first‐line drug for the treatment of uncomplicated plasmodium falciparum malaria in Liberia and recommend that national health efforts be directed at identifying alternative drug(s) to replace it.