bluuebunny/crossref_metadata_2025_split huggingface dataset:
Clients with chronic and complex conditions: their experiences of community nursing services
Authors: Wilkes Lesley , Cioffi Jane , Warne Bronwyn , Harrison Kathleen , Vonu‐Boriceanu Oana 
Published: June 2008

Aim.  This qualitative study aimed to explore and describes clients’ experiences of receiving care from community nurses.Background.  Understanding of the experiences of clients with chronic and complex conditions receiving community nursing care can provide insight into their needs. International studies have identified experiences clients have had of receiving care from community nurses. However, no Australian study was found that had specifically explored with clients who had chronic and complex conditions and their experiences of receiving care from community nurses in an area health service.Design.  A qualitative descriptive study conducted during 2005 explored and described clients’ experiences of the nursing care provided by community nurses.Method.  A purposive sample of 13 volunteer participants with chronic and complex conditions was interviewed and the transcripts analysed.Results.  Three main categories were identified that clients used to describe their experiences. These were: the client’s relationship with the nurse, care process and being able to stay out of hospital.Conclusions.  Clients strongly indicated their satisfaction with care provided by experienced community nurses and acknowledged that nurses are playing a key role in fostering their self‐management and avoiding their readmission to hospital. Areas that require further attention are the professional development of less‐experienced community nurses, services at the weekend, the scope of nursing management of clients with chronic conditions and the education needs of community nurses to meet the goals of these clients.Relevance to clinical practice.  This study highlights the need for nurses who work in strong autonomous clinical roles in the community to have experience in assessment, education, planning and delivery of client care before they can be competent community nurses. The possibility of adverse occurrences during weekends provides the opportunity for managers to review and plan weekday and weekend workloads and staffing.
Effects of canopy heterogeneity, seed abscission and inertia on wind‐driven dispersal kernels of tree seeds
Authors: Bohrer Gil , Katul Gabriel G. , Nathan Ran , Walko Robert L. , Avissar Roni 
Published: June 2008

Summary

Understanding seed dispersal by wind and, in particular, long‐distance dispersal (LDD) is needed for management of plant populations and communities, especially in response to changes in climate, land use and natural habitats. Numerical models designed to explore complex, nonlinear atmospheric processes are essential tools for understanding the fundamental mechanisms involved in seed dispersal. Yet, thus far, nearly all such models have not explicitly accounted for the spatial heterogeneity that is a typical feature of all ecosystems.
The recently developed Regional Atmospheric Modelling System (RAMS)‐based Forest Large Eddy Simulation (RAFLES) is used here to explore how within‐stand canopy heterogeneity impacts LDD. RAFLES resolves microscale canopy heterogeneity such as small gaps and variable tree heights, and it simulates their impacts on turbulence inside and above the canopy in the atmospheric boundary layer (ABL). For that purpose, an Eulerian–Lagrangian module of seed dispersal is added to RAFLES to simulate seed trajectories.
Particular attention is paid to the sensitivity of statistical attributes of the dispersal kernels (i.e. mean, mode, variance, tail) to key simplifications common to all seed dispersal models, such as horizontal homogeneity in the canopy and flow field, and the tight coupling between air parcel trajectories and seed trajectories (i.e. neglecting seed inertia). These attributes appear to be sensitive to various factors operating at scales ranging from the seed scale to the ABL scale.
Simulations with RAFLES show that LDD is characterized by a dispersal kernel with a ‘tail’, asymptotically approaching a power law decay of –3/2 (mainly occurring for lighter seeds at high wind speeds). This is consistent with asymptotic predictions from analytical models. The wind speed threshold at which seed abscission occurs, set‐up to be twice the standard deviation of the vertical wind speed, is shown to affect short‐distance dispersal, but has no significant impact on LDD. Ignoring the effects of seed inertia on the seed trajectory calculations has a minor effect on short‐distance dispersal and no effect on the probability of seed uplift. Thus, it has no significant impact on LDD.
Synthesis. Tree‐scale canopy heterogeneity affects the turbulence characteristics inside and above the canopy and, consequently, this affects dispersal kernel statistics. A key finding from this study is that ejection is enhanced above the shorter trees of the canopy. Seeds dispersed above shorter trees have a higher probability of experiencing LDD while their short‐distance dispersal remains practically the same. At inter‐annual time scales, such interactions could affect species composition.
Plant fecundity and seed dispersal in spatially heterogeneous environments: models, mechanisms and estimation
Authors: Schurr Frank M. , Steinitz Ofer , Nathan Ran 
Published: June 2008

SummaryPlant fecundity and seed dispersal often depend on environmental variables that vary in space. Hence, plant ecologists need to quantify spatial environmental effects on fecundity and dispersal.We present an approach to estimate and model two types of spatial environmental effects:source effectscause fecundity and dispersal to vary as a function of a source's local environment, whereaspath effectsdepend on all environments a seed encounters during dispersal. Path effects are described by first transforming physical space so that areas of low seed permeability are enlarged relative to others, and then evaluating dispersal kernels in this transformed ‘movement space’.Models for source and path effects are embedded into the established inverse modelling (IM) framework. This enables the statistical estimation of environmental effects from easily available data on the spatial distribution of seeds, seed sources and environmental covariates.The presented method is applied to data from a well‐studied population of the wind‐dispersed Aleppo pine (Pinus halepensis). We use local tree density as an environmental covariate, model fecundity as a function of a tree's basal area, and consider four dispersal kernels: WALD (a closed‐form mechanistic model for seed dispersal by wind), log‐normal, exponential power and 2Dt.The inclusion of source and path effects of tree density markedly improves IM performance. IM analyses and independent data agree in the parameter range of the mechanistic WALD kernel and in suggesting weak negative density‐dependence of fecundity. Of 64 IMs considered, the best four involve the WALD kernel and negative source effects on its shape parameter. The best IM predicts that increasing tree density at the source shortens median dispersal distance while enhancing long‐distance dispersal (LDD). Additionally, path effects lead to lower seed permeability of high density areas. These results shed light on the mechanisms by which environmental variation affects fecundity and dispersal ofP. halepensis. Moreover, the predicted density‐dependent dispersal causes a pronounced lag‐phase in simulations of population spread.Synthesis. The presented method can quantify environmental effects on fecundity and dispersal in a wide range of study systems. The movement space concept may furthermore promote a unified understanding of how various organisms move through spatially heterogeneous environments.
Inequalities in fruit‐removal and seed dispersal: consequences of bird behaviour, neighbourhood density and landscape aggregation
Authors: Carlo Tomás A. , Morales Juan M. 
Published: June 2008

Summary

Frugivores disperse the seeds of the majority of woody plant species world‐wide. Thus, insights on how frugivores influence the dispersal of plants and the variability of this process are crucial for understanding plant population dynamics in a rapidly changing world.
We used a spatially explicit, stochastic, individual‐based model that simulates fruit‐removal and seed dispersal by birds to assess bird density, landscape and neighbourhood effects on the inequalities of within‐population fruit‐removal rates and seed dispersal. We also compared model predictions with spatially‐explicit field data.
In our simulations, bird density had a strong effect on the distribution of fruit‐removal rates creating large inequalities among plants. Also, for equal bird densities, inequalities increased with the landscape level aggregation of plants.
Fruit removal increased with increasing plant neighbourhood density although there was a tendency to decline at the highest densities. Neighbourhood density also changed average dispersal distances, but with shorter distances at higher densities. Plants with few neighbours not only had longer distance dispersal but also a larger variance in seed rain across distances than plants with ten or more neighbours. These relationships between neighbourhood density and fruit removal and dispersal distance were scale‐dependent with a peak in correlations at 150‐m radius.
Similar to model predictions, field data shows an inverse relationship between dispersal distances (inferred from bird movements) and fruiting neighbourhood density. Also, fruit‐removal rates observed in the field show large numbers of plants receiving little or zero fruit‐removal. Fruit‐removal rate distributions were statistically indistinguishable between the simulation and field data. But, distributions were strikingly different from two alternative models that lacked spatial effects.
Synthesis. Our model and field data show that as fruiting plants become aggregated, inequalities in fruit‐removal rates increase and seed dispersal distance decreases. Both of these processes could help create and maintain plant aggregation and affect genetic structuring. The model also predicts that small‐scale neighbourhood effects can be controlled by large‐scale processes such as overall frugivore abundance and landscape‐level plant aggregation. Most importantly, both simulations and field data shows an interaction between plant spatial pattern and bird foraging, which results in neighbourhood‐specific dispersal and rates of fruit removal.
The effect of collisions with vegetation elements on the dispersal of winged and plumed seeds
Authors: Pounden E. , Greene D. F. , Quesada M. , Contreras Sánchez J. M. 
Published: June 2008

Summary

The role of collisions with vegetation elements in seed dispersal by wind has been examined only anecdotally. In particular, the idea that the effect of collisions in dispersal may depend on the aerodynamic class of the diaspore has not been broached.
We adapted a collision model for small particles to predict the probability of a winged or plumed seed colliding with a vegetation element as a function of the Stokes number (a dimensionless parameter which quantifies inertial tendency and includes diaspore terminal velocity, wind speed and diameter of the target element).
We performed experimental releases of seeds upwind of tree boles in two deciduous forest types (temperate and dry tropical) for 10 mid‐latitude and tropical species to test the collision model. The model was a reasonable expression of collision efficiency. At higher Stokes numbers, collisions were far more likely for seeds than for water droplets or other small particles.
Experimental releases were used in both forests to determine the effect of collisions with boles on distance travelled for several species. Seeds of the three species with asymmetric wings had significantly reduced dispersal following collisions; the single species with plumed seeds did not.
In a leafless tropical forest, we experimentally determined the frequency distribution of collisions per metre of travel for seeds released from a canopy. Approximately one collision occurred for every 2 m of flight through the volume occupied by branches and lianas. Distance achieved by asymmetric samaras was relatively unaffected by collisions with small vegetation elements, because the samaras quickly readopted stable autorotation. Conversely, bilaterally symmetric samaras had their dispersal greatly reduced.
Synthesis. The effect of collisions on dispersal depends on aerodynamic type. Collisions with small vegetation elements in forests should be more common for samaras than for plumed seeds, because plumed seeds generally have lower terminal velocities. Among winged seeds, collisions with branches will not seriously reduce dispersal except for bilaterally symmetric diaspores, because they are unable to rapidly regain stable autorotation. Reduction in dispersal due to collisions with boles will be unimportant because bole collisions, unlike branch collisions, are rare.
Costs of persistence and the spread of competing seeders and sprouters
Authors: Higgins Steven I. , Flores Olivier , Schurr Frank M. 
Published: June 2008

Summary

Trade‐offs between reproduction and persistence are thought to regulate life‐history evolution and competitive interactions between plants. We examined how seeder (non‐persistent semelparous) and sprouter (persistent iteroparous) life‐history strategies compete in fire prone shrublands.
Our hypothesis was that a trade‐off between persistence and colonization ability implies that seeders would be better colonizers than sprouters and would therefore stand to benefit from periods of rapid climate change, whereas sprouters are candidates for extinction in periods of shifting climates because of their relatively poor ability to colonize.
We developed an individual based simulation model that simulates lottery plant competition in a homogeneous spatial arena. We used an indirect method to estimate the fecundity and dispersal parameters needed by the model. Dispersal was described by a lognormal dispersal kernel.
We found that coexistence was possible in the system only for a restricted range of conditions. Moreover, the model when parameterized using our empirical estimates of demographic and dispersal rates, suggested that the sprouting strategies have a competitive advantage in the system we studied.
The migration capacities of the sprouter species were substantially lower than those of the seeder species. Our simulations suggested that, even though sprouters had a competitive advantage over seeders, interspecific competitive interactions did not slow the spread of seeder species, but did substantially hamper the spread of the slower spreading sprouter species.
Synthesis. We conclude that, in fire driven systems characterized by lottery recruitment, existing theories of colonization – persistence trade‐offs do not completely describe interactions between persistent and non‐persistent strategies. Moreover, our investigation of seeder – sprouter interactions suggests that sprouters, even though they might be competitively superior, will be more threatened by periods of rapid climate change because of their limited colonization ability.
Interspecific variation in primary seed dispersal in a tropical forest
Authors: Muller‐Landau Helene C. , Wright S. Joseph , Calderón Osvaldo , Condit Richard , Hubbell Stephen P. 
Published: June 2008

SummaryWe investigated the relationships of seed size, dispersal mode and other species characteristics to interspecific variation in mean primary seed dispersal distances, mean annual seed production per unit basal area, and clumping of seed deposition among 41 tropical tree species on Barro Colorado Island, Panama.A hierarchical Bayesian model incorporating interannual variation in seed production was used to estimate seed dispersal, seed production, and clumping of seed rain for each species from 19 years of data for 188 seed traps on a 50‐ha plot in which all adult trees were censused every 5 years.Seed dispersal was modelled as a two‐dimensional Student'sTdistribution with the degrees of freedom parameter fixed at 3, interannual variation in seed production per basal area was modelled as a lognormal, and the clumping of seed rain around its expected value was modelled as a negative binomial distribution.There was wide variation in seed dispersal distances among species sharing the same mode of seed dispersal. Seed dispersal mode did not explain significant variation in seed dispersal distances, but did explain significant variation in clumping: animal‐dispersed species showed higher clumping of seed deposition.Among nine wind‐dispersed species, the combination of diaspore terminal velocity, tree height and wind speed in the season of peak dispersal explained 40% of variation in dispersal distances. Among 31 animal‐dispersed species, 20% of interspecific variation in dispersal distances was explained by seed mass (a negative effect) and tree height (a positive effect).Among all species, seed mass, tree height and dispersal syndrome explained 28% of the variation in mean dispersal distance and seed mass alone explained 45% of the variation in estimated seed production per basal area.Synthesis. There is wide variation in patterns of primary seed rain among tropical tree species. Substantial proportions of interspecific variation in seed production, seed dispersal distances, and clumping of seed deposition are explained by relatively easily measured plant traits, especially dispersal mode, seed mass, and tree height. This provides hope for trait‐based generalization and modelling of seed dispersal in tropical forests.
Measuring long‐distance seed dispersal in complex natural environments: an evaluation and integration of classical and genetic methods
Authors: Jones F. Andy , Muller‐Landau Helen C. 
Published: June 2008

Summary

Seed dispersal is a critical life stage of plants, yet accurate measurement of dispersal distances has been difficult in natural systems. Genetic techniques for matching dispersed seeds to maternal trees provide valuable data on dispersal events. Questions remain regarding how best to estimate the population seed dispersal distance distributions from such data and how these estimates compare with classical non‐genetic estimates based on seed trap data alone.
Using simulated data, we compared seed shadow estimates obtained via standard inverse modelling of seed arrival into seed traps within mapped stands (summed seed shadow, SSS) with estimates from four models using genetic matches: direct fitting of the observed distribution of distances in the genotyped sample (observed distance, OBS), direct fitting inversely weighted by sampling intensity (OBSw), inverse modelling of numbers of seeds of each genotype in each trap (gene shadow model, GSM), and inverse modelling of frequencies of each genotype in each trap (competing sources model, CSM). We further explored how consideration of immigrant seed rain from unmapped and ungenotyped trees outside the stand affected dispersal estimates, denoting these variants SSSi, GSMi and CSMi.
We applied these models to an empirical data set for the Neotropical tree Jacaranda copaia, using a hierarchical Bayesian model to incorporate variation in fecundity among trees.
Fits to simulated data sets showed that OBS and SSS estimates were strongly biased, while SSSi, GSMi and CSMi were mildly biased. Root mean square errors varied as OBS >> SSS > OBSw > CSMi > GSMi > SSSi > CSM > GSM.
Comparing results for Jacaranda under the three best models, mean posterior estimates of dispersal distances varied as SSSi < GSM < CSM, but credible intervals overlapped among all three models, demonstrating agreement that long‐distance dispersal is common.
Synthesis. Here we reconcile two general approaches used to study seed dispersal distances in natural communities. Genetic and non‐genetic approaches can both provide good estimates of seed dispersal provided that analyses of genetic data take account of any deviation from random selection of seeds for genotyping, and that SSS models consider immigrant seed rain in the analysis whenever there is reason to think its contribution is non‐zero. The use of the models presented here should provide better estimates of population‐level dispersal distance distributions in genetic and classical seed dispersal studies.
Influence of benthic sediment transport on cold‐water coral bank morphology and growth: the example of the Darwin Mounds, north‐east Atlantic
Authors: WHEELER ANDREW J. , KOZACHENKO MAXIM , MASSON DOUG G. , HUVENNE VEERLE A. I. 
Published: June 2008

AbstractThe Darwin Mounds are small (up to 70 m in diameter), discrete cold‐water coral banks found at c. 950 m water depth in the northern Rockall Trough, north‐east Atlantic. Formerly described in terms of their genesis, the Darwin Mounds are re‐evaluated here in terms of mound growth processes based on 100 and 410 kHz side‐scan sonar data. The side‐scan sonar coverage is divided into a series of acoustic facies representing increasing current speed and sediment transport/erosion from south to north: pockmark facies, ‘mounds within depressions’ facies, Darwin Mound facies, stippled seabed facies and sand wave facies. Mound morphometric changes are quantified and show a south‐to‐north divergence from an inherited morphology, reflecting the outline of coral‐colonized fluid escape structures, to developed, downstream elongated, elevated mound forms. It is postulated that increasing current speeds and bedload sand transport favour mound growth and development by a process of enhanced sand sedimentation within mounds due to current deceleration by frictional drag around coral colonies. Comparisons are made with similar growth processes attributed to comparably sized cold‐water coral mounds in the Porcupine Seabight, offshore Ireland.
Molecular cloning and characterization of OsCDase, a ceramidase enzyme from rice
Authors: Pata Mickael O. , Wu Bill X. , Bielawski Jacek , Xiong Tou Cheu , Hannun Yusuf A. , Ng Carl K.‐Y. 
Published: June 2008

SummarySphingolipids are a structurally diverse group of molecules based on long‐chain sphingoid bases that are found in animal, fungal and plant cells. In contrast to the situation in animals and yeast, much less is known about the spectrum of sphingolipid species in plants and the roles they play in mediating cellular processes. Here, we report the cloning and characterization of a plant ceramidase from rice (Oryza sativa spp. Japonica cv. Nipponbare). Sequence analysis suggests that the rice ceramidase (OsCDase) is similar to mammalian neutral ceramidases. We demonstrate that OsCDase is a bona fide ceramidase by heterologous expression in the yeast double knockout mutant Δypc1Δydc1 that lacks the yeast ceramidases YPC1p and YDC1p. Biochemical characterization of OsCDase showed that it exhibited classical Michaelis–Menten kinetics, with optimum activity between pH 5.7 and 6.0. OsCDase activity was enhanced in the presence of Ca2+, Mg2+, Mn2+ and Zn2+, but inhibited in the presence of Fe2+. OsCDase appears to use ceramide instead of phytoceramide as a substrate. Subcellular localization showed that OsCDase is localized to the endoplasmic reticulum and Golgi, suggesting that these organelles are sites of ceramide metabolism in plants.