bluuebunny/crossref_metadata_2025_split huggingface dataset:
Tree architecture in relation to leaf dimensions and tree stature in temperate and tropical rain forests
Authors: King David A. , Maindonald John H. 
Published: March 2003

Summary1 The architecture and leaf dimensions (petiole length, blade length and blade width) of 403 tree species were studied at six sites ranging from lowland equatorial to temperate Australian rain forest. The branching patterns of understorey saplings and exposed canopy trees were classified as orthotropic (three‐dimensional arrangements of leaves about ascending twigs) or plagiotropic (leaves arranged in planes, usually along the sides of horizontal twigs).2 Among understorey saplings, orthotropic species had larger leaves and longer petioles than plagiotropic species. Discriminant analysis showed that the two groups could be separated by petiole length and the ratio of blade width to length, with those orthotropic species having short petioles also tending to have narrow blades.3 The petiole length distinguishing orthotropy from plagiotropy showed a linear decrease with increasing latitude, as small‐leaved short‐petioled orthotropic species were relatively abundant at the temperate Australian sites.4 The likelihood of a species being plagiotropic was weakly related to its shade tolerance and not related to adult stature or abundance, i.e. understorey leaf display was more closely related to leaf dimensions than to life‐history attributes. This importance of leaf dimensions may reflect their influence on light interception and mechanical support requirements.5 A smaller fraction of species was plagiotropic in the canopy than in the understorey, particularly in Australia, where many short‐petioled species shifted from plagiotropic to orthotropic on attaining the canopy.6 This switch from plagiotropy to orthotropy appeared to be associated with excess light levels relative to photosynthetic capacity, slow branch extension rates and low illumination angles. Thus, leaf display is related to leaf dimensions in shaded saplings, but light and physiological factors may have a greater influence on canopy architecture.
A buried spruce forest provides evidence at the stand and landscape scale for the effects of environment on vegetation at the Pleistocene/Holocene boundary
Authors: Pregitzer Kurt S. , Reed David D. , Bornhorst Theodore J. , Foster David R. , Mroz Glenn D. , Mclachlan Jason S. , Laks Peter E. , Stokke Douglas D. , Martin Patrick E. , Brown Shannon E. 
Published: March 2003

Summary 1 Due to a unique set of circumstances, we were able to excavate an entire spruce (Picea) forest in Michigan's Upper Peninsula, USA, which was buried in the early Holocene (9928 ± 133 uncalibrated 14C years bp). Trees ranged from < 5 cm to > 50 cm in diameter, and dominants were approximately 9 m tall. The stand was multi‐aged, with a maximum tree age of 145 years. Well‐preserved stem cross‐sections (n = 140) were recovered and the entire stand was mapped. 2 Stand reconstruction combined with pollen and sediment analysis revealed a pure spruce forest in the sandy lowlands surrounded by hills dominated by pine, oak and birch. These results are consistent with the idea that topography and substrate played an important role in determining forest composition during Holocene plant migrations. 3 Very rapid climate fluctuations were occurring 10 000 bp. The extensive spruce forests that once dominated much of interior North America were being replaced by subboreal and temperate conifer and hardwood species migrating northward. During this dynamic period in the Earth's history, patterns of plant community change are usually inferred from the study of pollen assemblages, and lack of detailed stand level information has prevented the direct comparison of the composition, age, structure and growth rates of Holocene forests with those that exist today. 4 Our findings that the age‐class distribution, size, spatial distribution of trees and radial growth rates of white spruce (Picea glauca) can be remarkably similar between the two time periods suggest that forest population and growth processes responsible for today's advancing tree‐lines appear to have been at work 10 000 years ago.
A test of community reassembly using the exotic communities of New Zealand roadsides in comparison to British roadsides
Authors: Wilson J. Bastow , Steel John B. , Dodd Mike E. , Anderson Barbara J. , Ullmann Isolde , Bannister Peter 
Published: March 2003

Summary 1 Competing theories of community assembly are very difficult to test. Four main theories exist. The Stochastic theory sees species assembly as being random. The Humpty Dumpty/Alternative Stable States (ASS) theory suggests that a community may be unable to reassemble itself from its constituent species. The Deterministic theory suggests there will be convergence to one stable state. The Pre‐adaptation theory is similar to the Deterministic theory but emphasizes that many species fit the stable state because of characters acquired elsewhere. 2 The reassembly of a flora into new communities in a different country, or its assimilation as a major component of such communities, offers a means to test these theories. The invasion of British plant species into New Zealand, and their reassembly into roadside communities there, is a good example of such a natural experiment. 3 Plant communities of NZ roadsides were compared to the communities of the British National Vegetation Classification (NVC). British roadside communities were also compared to the NVC as a control. New Zealand roadside communities provided a fit to the NVC communities of only 54.7% on average. After excluding species that are not present in NZ, and therefore could not possibly reassemble, the fit increased to 61.1%. British roadsides gave a 65.8% fit. The NZ figures are similar to the fit obtained with random data (58.7%), indicating that the NZ communities bear little relation to the ones formed by the same species in Britain. 4 Similarity between roadside communities in NZ and Britain was low, forming two almost distinct sets of communities. 5 Some of the predictions of the Stochastic, Humpty Dumpty / ASS and Deterministic models are borne out, but others are not. It is concluded that British species have reassembled into communities in NZ most of which are new, i.e. distinct from those that occur in the native range of the species in Britain. The evidence points to a process of community assembly by pre‐adaptation.
Seed bank dynamics of Onopordum acanthium: emergence patterns and chemical attributes
Authors: Qaderi Mirwais M. , Cavers Paul B. , Bernards Mark A. 
Published: March 2003

Summary

Cypselas (fruits) of Scotch thistle (Onopordum acanthium) germinate unpredictably over a long period of time. We evaluated the effects of soil type, burial depth and collection date on the emergence patterns of two populations of O. acanthium, ESW and Quarry (Q).
From each of four separate collections made throughout 1996, five replicates of 200 cypselas each were placed on the surface or buried at depths of 3 or 15 cm in both sand and silt‐loam soils (i.e. field conditions) and emergence was recorded biweekly between August 1996 and September 1999.
Emergence was intermittent over the 3 years, with a higher total percentage from silt loam (17%) than from sand (9%), and from 3 cm depth (18%) compared with the surface (8%).
After 3 years, all remaining viable, split (germinated but not emerged), decayed and unfilled cypselas were retrieved. Total germination over the 3 years (emerged plus split) was up to 77% at 3 cm in silt loam but always less than 10% at 15 cm in both soils for both populations. Although a higher percentage of cypselas germinated under controlled conditions when retrieved from loam compared with sand (89% vs. 66%), a significant number from all treatments did not germinate until scarified.
Cypselas that ripened under the warmest temperature (collection 3) had the highest emergence in the year of collection (1996), while more of those that ripened under cooler temperatures (collections 1 and 4) emerged in later years (1998 and 1999). Both initial and later emergence patterns for both populations varied greatly with collection date. This may be the first time that seedling emergence from the seed bank for different collections has been monitored over several years.
We compared waxes, lignins and soluble phenolics in the coats of cypselas retrieved from soil (early germinators) with those that germinated only after scarification. More surface wax was found in dormant cypselas.
Understanding these complex germination/emergence patterns may help develop control policies for O. acanthium.
Plant response to solar ultraviolet‐B radiation in a southern South American Sphagnum peatland
Authors: Searles Peter S. , Flint Stephan D. , Díaz Susana B. , Rousseaux M. Cecilia , Ballaré Carlos L. , Caldwell Martyn M. 
Published: March 2003

Summary

Plant growth and pigmentation of the moss Sphagnum magellanicum and the vascular plants Empetrum rubrum, Nothofagus antarctica and Tetroncium magellanicum were measured under near‐ambient (90% of ambient) and reduced (20%) ultraviolet‐B (UV‐B) radiation for three growing seasons in a Sphagnum peatland in Tierra del Fuego, Argentina (55° S).
Reduction of solar UV‐B increased height growth but decreased volumetric density in S. magellanicum so that biomass production was not influenced during the 3 years. The morphology of vascular plants tended not to respond to UV‐B reduction.
A 10–20% decrease in UV‐B‐absorbing compounds occurred in T. magellanicum under solar UV‐B reduction. No effects were seen on chlorophyll or carotenoids in S. magellanicum, although, for UV‐B‐absorbing compounds, a significant interaction between UV‐B and year suggests some response to solar UV‐B reduction.
The climate‐related growth of the dwarf shrub E. rubrum was assessed retrospectively by correlating an 8‐year record of annual stem elongation with macroclimatic factors including solar UV‐B and visible radiation, precipitation and temperature.
No significant negative correlations were found between annual E. rubrum stem elongation and ambient solar UV‐B, the ratio of UV‐B : visible radiation, or the 305‐nm : 340‐nm irradiance ratio for an 8‐year record (1990–91 to 1997–98), nor was stem elongation affected by solar UV‐B reduction in our experimental field plots after 3 years.
The role of solar UV‐B radiation on plant growth in Sphagnum peatlands in Tierra del Fuego, Argentina, is likely to depend on the severity of stratospheric ozone depletion over the next several decades. The increases in ambient solar UV‐B associated with ozone depletion over the last 20 years are less than the difference between our radiation treatments. Therefore, providing that the ozone layer substantially recovers by the middle of this century, only modest effects of increased solar UV‐B on plant growth may be expected.
Grazing effect on diversity of annual plant communities in a semi‐arid rangeland: interactions with small‐scale spatial and temporal variation in primary productivity
Authors: Osem Yagil , Perevolotsky Avi , Kigel Jaime 
Published: March 2003

Summary

The interactive effect of grazing and small‐scale variation in primary productivity on the diversity of an annual plant community was studied in a semiarid Mediterranean rangeland in Israel over 4 years. The response of the community to protection from sheep grazing by fenced exclosures was compared in four neighbouring topographic sites (south‐ and north‐facing slopes, hilltop and wadi (dry stream) shoulders), differing in vegetation, physical characteristics and soil resources. The herbaceous annual vegetation was highly diverse, including 128 species. Average small‐scale species richness of annuals ranged between 5 and 16 species within a 20 × 20 cm quadrat, and was strongly affected by year and site.
Above‐ground potential productivity at peak season (i.e. in fenced subplots) was typical of semiarid ecosystems (10–200 g m−2), except on wadi shoulders (up to 700 g m−2), where it reached the range of subhumid grassland ecosystems. Grazing increased richness in the high productivity site (i.e. wadi), but did not affect, or reduced, it in the low productivity sites (south‐ and north‐facing slopes, hilltop). Under grazing, species richness was positively and linearly related to potential productivity along the whole range of productivity. Without grazing, this relationship was observed only at low productivity (< 200 g m−2).
The effect of grazing along the productivity gradient on different components of richness was analysed. At low productivity, number of abundant, common and rare species all tended to increase with productivity, both with and without grazing. Rare species increased three times compared with common and abundant species. At high productivity, only rare species continued to increase with productivity under grazing, while in the absence of grazing species number in the different abundance groups was not related to productivity.
In this semiarid Mediterranean rangeland, diversity of the annual plant community is determined by the interaction between grazing and small‐scale spatial and temporal variation in primary productivity, operating mainly on the less abundant species in the community.
Growth and mortality in high and low light: trends among 15 shade‐tolerant tropical rain forest tree species
Authors: Bloor Juliette M. G. , Grubb Peter J. 
Published: March 2003

Summary

Past work on tropical rain forest tree seedlings has been dominated by contrasts between strongly light‐demanding and strongly shade‐tolerant species. We examined patterns of growth and mortality among shade‐tolerant tree seedlings in response to light, and investigated the morphological and physiological correlates of high seedling growth and survival rates across species.
Seedlings of 15 tree species from Australian tropical lowland forest were grown for up to 1 year in neutral‐density shadehouses at three light levels (10%, 0.8% and 0.2% full daylight). All species showed negligible mortality in the 10% and 0.8% shadehouses, but survival was significantly reduced in 0.2% daylight.
Seedling survival rate in 0.2% daylight showed no significant relationship with either the dry mass of seed reserves (embryo plus endosperm), or relative growth rates in dry mass (RGRM) in 0.8% and 10% light.
The RGRM values in 0.8% and 10% daylight were strongly positively correlated, and showed a strong negative correlation with the dry mass of seed reserves. Interspecific variation in low‐light RGRM was driven by unit leaf rate (rate of accumulation of dry mass per unit area of leaf), whereas interspecific variation in high‐light RGRM was most closely correlated with leaf area ratio (leaf area per total plant dry mass).
Variation in seedling characters in response to light may have important implications for the coexistence of shade‐tolerant tropical tree species.
Bayesian statistics in medical research: an intuitive alternative to conventional data analysis
Authors: Gurrin Lyle C. , Kurinczuk Jennifer J. , Burton Paul R. 
Published: March 2003

SummaryStatistical analysis of both experimental and observational data is central to medical research. Unfortunately, the process of conventional statistical analysis is poorly understood by many medical scientists. This is due, in part, to the counter‐intuitive nature of the basic tools of traditional (frequency‐based) statistical inference. For example, the proper definition of a conventional 95% confidence interval is quite confusing. It is based upon the imaginary results of a series of hypothetical repetitions of the data generation process and subsequent analysis. Not surprisingly, this formal definition is often ignored and a 95% confidence interval is widely taken to represent a range of values that is associated with a 95% probability of containing the true value of the parameter being estimated. Working within the traditional framework of frequency‐based statistics, this interpretation is fundamentally incorrect. It is perfectly valid, however, if one works within the framework of Bayesian statistics and assumes a ‘prior distribution’ that is uniform on the scale of the main outcome variable. This reflects a limited equivalence between conventional and Bayesian statistics that can be used to facilitate a simple Bayesian interpretation based on the results of a standard analysis. Such inferences provide direct and understandable answers to many important types of question in medical research. For example, they can be used to assist decision making based upon studies with unavoidably low statistical power, where non‐significant results are all too often, and wrongly, interpreted as implying ‘no effect’. They can also be used to overcome the confusion that can result when statistically significant effects are too small to be clinically relevant. This paper describes the theoretical basis of the Bayesian‐based approach and illustrates its application with a practical example that investigates the prevalence of major cardiac defects in a cohort of children born using the assisted reproduction technique known as ICSI (intracytoplasmic sperm injection).
Evidence‐based medicine and randomized double‐blind clinical trials: a study of flawed implementation
Authors: Kirk‐Smith Michael D. , Stretch David D. 
Published: March 2003

AbstractThe randomized double‐blind clinical trial (RDBCT) is a key source of information for evidence‐based medicine. However, anomalous and unexplainable results have prompted suggestions that ‘unknown and unidentifiable biases’ may exist. This paper identifies that a possible flaw in the implementation of RDBCTs may account for these biases. The flaw relates to the breaking of the double blind through the generation of beliefs and expectations in experimenters. These, in turn, may lead to unconscious biases in assessment and cues to patients. It is then uncertain how much of an observed effect is due to such expectations or the treatment itself. Therefore, any RDBCT in which the maintenance of blinding is not monitored throughout its course is at risk of its conclusions being compromised. It is not sufficient to assert that blinding must have been maintained through arguments based on design features. The burden of proof is on the researchers to demonstrate, through data, that blinding has been maintained. The need to address social psychological issues in implementing RDBCTs is discussed and it is recommended that to avoid this confound, methods of monitoring and accounting for experimenter beliefs and expectations should be routinely included in future RDBCTs.
Utility and treatment decisions: 15 clinical cases in Japan
Authors: Matsuura Nanshi , Kamae Isao , Nakamura Hajime , Maruo Takeshi 
Published: March 2003

AbstractThe purpose of this study was to investigate the applicability of utility concepts to treatment decision making in different clinical situations. In each of the 15 independent cases studied, subjective utility values were obtained directly from the patients before the treatment decisions were made. The optimal decision based on the utility values was then calculated. The actual treatment decisions were made without any input or influence by this study. The data were obtained at two large public hospitals and two privately owned multi‐service hospitals in Kobe, Japan. Active participation by patients in treatment decision making seems particularly useful when two or more treatments are approximately equivalent in terms of outcome. A careful assessment of an individual patient’s utilities can help the patient choose a treatment option meeting individual goals. Patient autonomy must be strengthened by giving the patients realistic and unbiased information of the alternatives available and the possible outcomes.
The rationale of value‐laden medicine
Authors: MD Michael H. Kottow MA(Soc) 
Published: March 2003

AbstractMedicine is becoming increasingly confident that scientific advances, especially in the area of genetics, will allow a major improvement in the control and eradication of disease. This development seems to go hand in hand with health‐enhancement strategies, erasing the distinction between the states of health and disease, and blurring the specific goals of medical services. Medicine tends to become an increasingly technocentric practice that relies heavily on expert knowledge and on epidemiological evidence, neglecting the lived‐body experience of being ill, and tending to transform costly medical services into commodities only affordable by the affluent. This paper argues that disease is not merely a functional description, but rather a definitely value‐laden organismic state that is experienced by the patient, needs to be explored and treated by medical practitioners, and requires the assessment and participation of social institutions concerned with the delivery and support of medical services. Each of these perspectives introduces its own set of values, both in the clinical encounter and in public health programmes. Bioethics seems to be the appropriate discipline to discuss all these values involved, and help assign them properly in order to rescue the caring concern of medicine for the sick, as well as uphold a principle of fairness in publicly funded medical services.
Reorganizing the delivery of intensive care could improve efficiency and save lives
Authors: MSc Adrienne G. Randolph MD , PhD Peter Pronovost MD 
Published: March 2003

AbstractCritically ill patients are at high risk for death and permanent disability. Their care is also very expensive. The method of delivering critical care services to these patients can have an impact on their clinical and economic outcomes. Researchers face significant challenges when attempting to identify an association between an intensive care unit (ICU) organizational characteristic and patient outcomes. In this paper we review the challenges faced when evaluating the impact of ICU organizational characteristics on patient outcomes and highlight ICU characteristics that are consistently associated with improved patient outcomes. These characteristics include: (i) the presence of specialist physicians devoted to the ICU; (ii) increased nurse : patient ratios; (iii) decreased use of tests and evaluations that will not change clinical management; (iv) development and implementation of evidence‐based protocols and guidelines; (v) use of computer‐based alerting and reminding systems; and (vi) having a pharmacist participate in daily rounds in the ICU. When implementing these in ICUs, it is important to evaluate the impact of these characteristics on patient outcomes. We provide a format for such an evaluation. Given the growing evidence supporting the association between specific ICU characteristics and improved patient outcomes, we hope the future realizes broad implementation of these beneficial characteristics.
When you hear hoofs, think horses, not zebras: an evidence‐based model of health care accountability
Authors: MPH Vahé A. Kazandjian PhD 
Published: March 2003

AbstractHealth care organizations are increasingly asked to show accountability about their performance. This paper proposes that accountability can best be achieved through evaluative methods that are based on evidence regarding the relationship between processes of care and expected outcomes. Root cause analysis (RCA) is used as an illustration of how a generic method of inquiring can be transformed into an ongoing monitoring, evaluation, user education and accountability strategy. The role of performance indicators, as well as patient and community expectations, is discussed.