bluuebunny/crossref_metadata_2025_split huggingface dataset:
Spatial monitoring of a non‐stationary soil property: phosphorus in a Florida water conservation area
Authors: Marchant B. P. , Newman S. , Corstanje R. , Reddy K. R. , Osborne T. Z. , Lark R. M. 
Published: July 2009

SummaryEcological restoration plans in the Florida Everglades require detailed information about the status and change of the nutrient content of the soil. The soil total phosphorus (TP) content is of particular importance as the system is naturally P limited and the TP enrichment has led to changes in the wetland vegetation communities. One way to provide the relevant information is by geostatistical prediction from sampled data. However, conventional geostatistical models assume that properties being monitored are realizations of second‐order stationary random functions. The assumption of second‐order stationarity is not appropriate for soil TP in Water Conservation Area 1 (WCA‐1) of the Florida Everglades because the mean and variance of soil TP are larger at sites adjacent to the canals which bound WCA‐1 and deliver P to the system than at sites in the interior of the region.We develop a novel linear mixed‐model framework for spatial monitoring of a property for which this assumption is not valid. Specifically we use this non‐stationary model to map the status and change of TP within WCA‐1 from surveys carried out in 1991 and 2003. We fit the parameters of the model by residual maximum likelihood (REML) and compare the effectiveness of this non‐stationary model with the conventional stationary model.Conventional second‐order stationary models fail to represent accurately the large uncertainty in predictions of TP adjacent to the canals. The non‐stationary model predicts an invading front of P entering the interior of the region which is not evident in the predictions from the stationary model. Tests on the log‐likelihood and the standardized squared prediction error of the fitted models provide further evidence in favour of the non‐stationary model.The sampling intensity required to ensure a certain precision of TP predictions varies across WCA‐1 with the variance of TP. Therefore we apply a spatial simulated annealing optimization algorithm to design future monitoring surveys based upon our non‐stationary model which ensure that the status and change are efficiently and effectively predicted across the region.
Xylem root and shoot hydraulics is linked to life history type in chaparral seedlings
Authors: Pratt Robert B. , North Gretchen B. , Jacobsen Anna L. , Ewers Frank W. , Davis Stephen D. 
Published: July 2009

Summary 1. Shrubs in fire prone chaparral communities have evolved different life history types in response to fire. A key to understanding the evolution of life history type differences is to understand how physiological traits are linked to differences in life history type. Vascular adaptations are important for delivering an efficient and stable water supply to evergreen chaparral shrub leaves. This study tested for a link between vascular physiology and life history type in chaparral shrubs. 2. Chaparral shrub species along the south‐western coast of North America survive wildfire by three different life histories. Non‐sprouters are killed by fire and re‐establish exclusively through germination of fire‐stimulated seeds, facultative sprouters re‐establish by a combination of vegetative sprouting and fire‐stimulated seeds, and obligate sprouters re‐establish exclusively by vegetative sprouting because their seeds do not survive fire. Non‐sprouters and facultative sprouters establish seedlings in the open canopy post fire environment, whereas obligate sprouters establish seedlings in the shady understory of the mature chaparral canopy. 3. Seedlings of nine species (Rhamnaceae) representing three each of the different life history types were grown in deep containers in a common garden under treatments of sun and shade. Hydraulic conductance was measured using a high‐pressure flow meter for all organs, and a vacuum technique was used to measure conductance of fine and woody roots. We predicted that non‐sprouters would exhibit greater hydraulic efficiency than the sprouting species, and that facultative sprouters would be more efficient than the shade tolerant obligate sprouters. 4. Non‐sprouters had the greatest hydraulic conductance per unit leaf and sapwood area at the whole seedling level, whereas facultative and obligate sprouters were not different. Comparing hydraulic conductance across major organs (from fine roots to leaves) showed that the hydraulic system was well coordinated. At the whole seedling level, the root system was more of a bottleneck than the shoot system. This pattern was consistent with high resistance extraxylary pathways in roots and differences in root architecture. 5. The greater hydraulic efficiency of the non‐sprouter life history type is attributed to its post‐fire pioneering habit and may partially explain the relatively high speciation in the non‐sprouters. Lower hydraulic efficiency is associated with a sprouting life history and greater shade tolerance. The seedling root systems represent a hydraulic bottleneck that may place roots under especially intense selection.
Variation in leaf functional trait values within and across individuals and species: an example from a Costa Rican dry forest
Authors: Hulshof Catherine M. , Swenson Nathan G. 
Published: July 2009

Summary 1. Patterns of species co‐existence and species diversity in plant communities remain an important research area despite over a century of intensive scrutiny. To provide mechanistic insight into the rules governing plant species co‐existence and diversity, plant community ecologists are increasingly quantifying functional trait values for the species found in a wide range of communities. 2. Despite the promise of a quantitative functional trait approach to plant community ecology, we suggest that, along with examining trait variation across species, an assessment of trait variation within species should also be a key component of a trait‐based approach to community ecology. Variability within and between individuals and populations is likely widespread due to plastic responses to highly localized abiotic and biotic interactions. 3. In this study, we quantify leaf trait variation within and across ten co‐existing tree species in a dry tropical forest in Costa Rica to ask: (i) whether the majority of trait variation is located between species, within species, within individuals or within the leaves themselves; (ii) whether trait values collected using standardized methods correlate with those collected using unstandardized methods; and (iii) to what extent can we differentiate plant species on the basis of their traits? 4. We find that the majority of variation in traits was often explained by between species differences; however, between leaflet trait variation was very high for compound‐leaved species. We also show that many species are difficult to reliably differentiate on the basis of functional traits even when sampling many individuals. 5. We suggest an ideal sample size of at least 10, and ideally 20, individuals be used when calculating mean trait values for individual species for entire communities, though even at large sample sizes, it remains unclear if community level trait values will allow comparisons on a larger geographic scale or if species traits are generally similar across scales. It will thus be critical to account for intraspecific variation by comparing species mean trait values across space in multiple microclimatic environments within local communities and along environmental gradients. Further, quantifying trait variability due to plasticity and inheritance will provide a better understanding of the underlying patterns and drivers of trait variation as well as the application of functional traits in outlining mechanisms of species co‐existence.
Work‐related stress, education and work ability among hospital nurses
Authors: Golubic Rajna , Milosevic Milan , Knezevic Bojana , Mustajbegovic Jadranka 
Published: July 2009

AbstractTitle.  Work‐related stress, education and work ability among hospital nurses. Aim.  This paper is a report of a study conducted to determine which occupational stressors are present in nurses’ working environment; to describe and compare occupational stress between two educational groups of nurses; to estimate which stressors and to what extent predict nurses’ work ability; and to determine if educational level predicts nurses’ work ability.Background.  Nurses’ occupational stress adversely affects their health and nursing quality. Higher educational level has been shown to have positive effects on the preservation of good work ability.Method.  A cross‐sectional study was conducted in 2006–2007. Questionnaires were distributed to a convenience sample of 1392 (59%) nurses employed at four university hospitals in Croatia (n = 2364). The response rate was 78% (n = 1086). Data were collected using the Occupational Stress Assessment Questionnaire and Work Ability Index Questionnaire.Findings.  We identified six major groups of occupational stressors: ‘Organization of work and financial issues’, ‘public criticism’, ‘hazards at workplace’, ‘interpersonal conflicts at workplace’, ‘shift work’ and ‘professional and intellectual demands’. Nurses with secondary school qualifications perceived Hazards at workplace and Shift work as statistically significantly more stressful than nurses a with college degree. Predictors statistically significantly related with low work ability were: Organization of work and financial issues (odds ratio = 1·69, 95% confidence interval 1·22–2·36), lower educational level (odds ratio = 1·69, 95% confidence interval 1·22–2·36) and older age (odds ratio = 1·07, 95% confidence interval 1·05–1·09).Conclusion.  Hospital managers should develop strategies to address and improve the quality of working conditions for nurses in Croatian hospitals. Providing educational and career prospects can contribute to decreasing nurses’ occupational stress levels, thus maintaining their work ability.
Transgressive aggression in Sceloporus hybrids confers fitness through advantages in male agonistic encounters
Authors: Robbins Travis R. , Pruitt Jonathan N. , Straub Lorelei E. , Mccoy Earl D. , Mushinsky Henry R. 
Published: July 2009

Summary 1. We investigated agonistic behaviour and associated characteristics of Sceloporus woodi (Florida scrub lizard), Sceloporus undulatus (Eastern fence lizard) and their hybrids using staged territorial encounters. 2. These Sceloporus hybrids exhibit transgressive aggression and transgressive head‐girth relative to the parental species and the transgressive aggression was specifically associated with an advantage in agonistic encounters. Our results suggest a hybrid advantage in natural habitats when defending and invading territories against either parental species. 3. We further analysed general advantages in agonistic encounters across the entire three‐group system to elucidate characteristics that may be advantageous under specific circumstances. Individuals with larger body size (SVL) and greater aggression had an overall advantage in agonistic encounters; however, smaller individuals could win when slightly more aggressive and fatter, and less aggressive individuals could win when slightly larger, especially with greater head‐girth. 4. The extreme hybrid phenotypes likely occurred through transgressive segregation, which has been implicated as a process through which homoploid, hybrid speciation can occur. Some form of ecological divergence is necessary, however, to impede parental gene flow. Our data suggest that ecological divergence could manifest in territorial species through transgressive aggression.
Great tits lay increasingly smaller clutches than selected for: a study of climate‐ and density‐related changes in reproductive traits
Authors: Ahola Markus P. , Laaksonen Toni , Eeva Tapio , Lehikoinen Esa 
Published: July 2009

Summary 1. The phenology of temperate environments and therefore timing of breeding has advanced in a number of bird species due to climate warming. Few studies, however, have examined the mechanisms behind the observed changes, the role of natural selection in them or the determinants of the selection. In other traits such as clutch size, even changes over years have been rarely studied. 2. We studied patterns and trends in timing of breeding, clutch size and fledgling production in the great tit Parus major in South‐West Finland during 1953–2008, as well as natural selection on the timing and clutch size, based on fledgling production. We also examined connections between these parameters and a number of climatic and population intrinsic factors. 3. Laying date was earlier when the pre‐breeding period was warm and tended to be earlier when breeding density was high, but it did not show any temporal change during the study period despite temporal increases in both explanatory factors. Number of fledglings decreased through declines in both mean clutch size and fledging success. Fledging success was better with higher breeding‐time temperature and larger clutch size. Both the clutch size and fledging success were lower at higher breeding density. 4. Selection on laying date did not change through time, but there was a selection for early laying with high breeding‐time temperature and high breeding density. Interestingly, in contrast to the decrease in reproductive output, the selection for larger than average clutch size strengthened with time, which was not explained by any tested factor. 5. We suggest that increasingly favourable conditions in winters have enhanced the survival and resulted in the observed increase in great tit breeding density. This may have most concerned young and otherwise low‐quality individuals, which also most likely end up breeding in the increasingly occupied low‐quality territories. This hypothesis was indicatively supported by increased within‐year variation in both laying date and clutch size. The changes could also explain the lack of advancement in laying date as well as the increasing selection for large clutch sizes as the fittest individuals most likely occupy the best territories and lay largest clutches.
Conception date affects litter type and foetal sex ratio in female moose in Estonia
Authors: Veeroja Rauno , Kirk Anne , Tilgar Vallo , Säde Sander , Kreitsberg Merit , Tõnisson Jüri 
Published: July 2009

Summary 1. The Trivers–Willard model of optimal sex ratios predicts that in polygynous species mothers in better condition should produce more male than female offspring. However, empirical support for this hypothesis in mammals and especially ungulates has been equivocal. This may be because the fitness of mothers has been defined in different ways, reflecting morphological, physiological or behavioural measures of condition. In addition, factors other than maternal condition can influence a mother’s fitness. Given that recent studies of wild ungulates have demonstrated the importance of the timing of conception and birth on offspring fitness, litters conceived at different stages of the rut might be expected to exhibit differences in types and embryonic sex ratio. 2. Based on a 6‐year survey of the reproductive tracts of female moose harvested in Estonia, we investigated the effect of conception date on the types of litters produced and on the foetal sex ratio. 3. There was a clear relationship between conception date and litter characteristics. Overall, earlier conceived litters were more likely than those conceived late to contain multiple embryos and a high proportion of males. However, while foetal sex ratio varied nonlinearly with conception date in yearlings and subadults, no relationship was found in adults. 4. We conclude that female moose adjust foetal sex ratio and litter type/size depending on their age and the date of conception, and that these adjustments are in accordance with the Trivers–Willard hypothesis if females that conceive earlier are in better condition.
Use of resource selection functions to identify conservation corridors
Authors: Chetkiewicz Cheryl‐Lesley B. , Boyce Mark S. 
Published: July 2009

Summary

Corridors are commonly used to connect fragments of wildlife habitat, yet the identification of conservation corridors typically neglects processes of habitat selection and movement for target organisms. New technologies and analytical tools make it possible to better integrate landscape patterns with behavioural processes. We illustrate the integration of resource selection functions (RSFs) and least‐cost path (LCP) analyses for the purpose of corridor planning for two large carnivores.
We used RSFs developed from Global Positioning System telemetry data to predict the seasonal distribution of two large carnivores: grizzly bears Ursus arctos and cougars Puma concolor. We then applied LCP analyses to identify potential corridors in two fragmented montane landscapes – Canmore and Crowsnest Pass – in Alberta, Canada.
Grizzly bear habitat selection in both areas positively correlated with greenness in all seasons and soil wetness and proximity to water in the summer when both variables were associated with bear forage. During spring, grizzly bear occurrence in Canmore inversely correlated with road density.
For cougars, habitat selection varied by region: it negatively correlated with road density in Canmore during non‐winter and positively correlated with terrain ruggedness in Crowsnest Pass. Cougar occurrence during the non‐winter season in Canmore positively correlated with greenness.
For each species, seasonal RSFs were used to develop a cost surface for LCP analyses to identify potential corridor locations in each study area. Overlaying the paths for the two species highlighted where the landscape could support corridors for both species and potential highway crossing zones. The telemetry data supported some of these modelled crossings.
Synthesis and applications. We show how to integrate RSFs and least‐cost modelling to identify corridors for conservation. We focus on two large carnivores in the Canadian Rocky Mountains to identify potential corridors in Canmore and provide a framework for corridor planning in Crowsnest. We suggest that our approach is applicable to many other target species in addition to large carnivores in human‐dominated landscapes.
Competitive interactions and the effect of herbivory on Bt‐Brassica napus, Brassica rapa and Lolium perenne
Authors: Damgaard Christian , Kjær Christian 
Published: July 2009

Summary 1.  The probability of a transgenic crop establishing a feral population outside cultivated areas and possibly outcompeting naturally occurring species needs to be assessed to make an ecological risk assessment of the transgenic crop. 2.
The interaction between herbivory and competition is thought to determine the ecological success of insect‐resistant plants, and this interaction was investigated in a competition experiment with transgenic insect‐resistant Bt‐Brassica napus, Brassica rapa, Lolium perenne, and herbivory from the large white butterfly Pieris brassicae. 3.
As expected, herbivory had a negative effect on the biomass of B. rapa at high plant densities. The competitive ability of L. perenne, when growing with B. rapa, increased significantly with the level of herbivory on B. rapa. 4.
To predict the effect of herbivory in a natural ecosystem, plant competition between the two annual Brassica species was analysed in a population ecological model. It was concluded that it is probable that transgenic Bt‐B. napus plants may invade a natural habitat if herbivory is sufficiently high and the habitat is suitable for B. napus. 5.
Synthesis and applications. The results indicate that it is important to study the interaction between herbivory and competition when assessing the ecological risk of insect‐resistant genetically modified crops. Furthermore, combining ecological data from manipulated experiments with population ecological modelling is a fruitful approach when conducting environmental risk assessments.
Fresh insights into long‐term changes in flora, vegetation, land use and soil erosion in the karstic environment of the Burren, western Ireland
Authors: Feeser Ingo , O’Connell Michael 
Published: July 2009

Summary 1.
The study focuses on species‐rich, upland, heathy vegetation with arctic‐alpine floristic affinities and Sesleria grasslands in the karstic Burren region, western Ireland. The investigations aimed at reconstructing the long‐term development of these high conservation‐value communities and the role of farming in their formation and long‐term survival. 2.
The methods used included pollen analysis and 14C‐dating of short monoliths and investigation of grykes (fissures in karstic limestone) for evidence of soil erosion. Special attention was paid to fossil, coprophilous fungal spores as indicators of local grazing. The strong local character of the pollen records facilitated identification of inter‐site differences as well as regional patterns. It is shown that open pine woodland characterized the Cappanawalla uplands between c. 1500 BC and 500 BC. It is proposed that such woodlands, with floristic affinities to Scandinavian open pine woodlands on calcareous soils, provided a suitable environment for the present‐day, open heath vegetation with species such as Dryas octopetala, Arctostaphylos uva‐ursi, Geranium sanguineum and Empetrum nigrum. 3.  Burning of vegetation as a management tool was important in the uplands over most of the last two millennia. Firing seems to have ceased with the onset of more intensive grazing regimes in the 18th century. 4.
Synthesis. Upland palaeoarchives, derived from shallow peaty deposits, show that the upland Burren supported mainly plagioclimax Corylus‐dominated woody vegetation and grasslands from c. 1500 BC (beginning of present record), until possibly as late as the 17th century AD. In the uplands of the north‐western Burren, open, species‐rich pinewoods with hazel dominated. The northern‐arctic elements in the present‐day upland flora survived clearances, involving initially Pinus sylvestris (c. 500 BC) and subsequently Corylus avellana (c. AD 1600). Colluvial material retrieved from grykes supports the idea of considerable soil loss occurring as late as the first and early 2nd millennium AD. The investigations highlight the potential of upland palaeoarchives, consisting of short sequences, for elucidating vegetation and land‐use dynamics in karstic environments such as the Burren.