495 research outputs found
Numerical modelling of glacial lake outburst floods using physically based dam-breach models
No full textThe instability of moraine-dammed proglacial lakes creates the potential for catastrophic glacial lake outburst floods (GLOFs) in high-mountain regions. In this research, we use a unique combination of numerical dam-breach and two-dimensional hydrodynamic modelling, employed within a generalised likelihood uncertainty estimation (GLUE) framework, to quantify predictive uncertainty in model outputs associated with a reconstruction of the Dig Tsho failure in Nepal. Monte Carlo analysis was used to sample the model parameter space, and morphological descriptors of the moraine breach were used to evaluate model performance. Multiple breach scenarios were produced by differing parameter ensembles associated with a range of breach initiation mechanisms, including overtopping waves and mechanical failure of the dam face. The material roughness coefficient was found to exert a dominant influence over model performance. The downstream routing of scenario-specific breach hydrographs revealed significant differences in the timing and extent of inundation. A GLUE-based methodology for constructing probabilistic maps of inundation extent, flow depth, and hazard is presented and provides a useful tool for communicating uncertainty in GLOF hazard assessment
Parenchyma abundance in wood of evergreen trees varies independently of nutrients
No full textThe abundance of living cells in wood—mainly as interconnected axial and ray
parenchyma networks—varies widely between species. However, the functional
significance of this variation and its role in plant ecological strategies is poorly understood, as is the extent to which different parenchyma fractions are favored in relation to soil nutrients and hydraulic functions. We analyzed wood tissue fractions of 16 Australian angiosperm species sampled from two nearby areas with similar climate but very different soil nutrient profiles and investigated structure-function links with soil and tissue nutrient concentrations and other plant traits. We expected the variation in parenchyma fractions to influence nutrient concentrations in wood xylem, and to find
species with lower parenchyma fractions and accordingly lower nutrient requirements on lower-nutrient soils. Surprisingly, both axial and ray parenchyma fractions were mostly unrelated to tissue and soil nutrient concentrations, except for nitrogen concentration in stem sapwood. Species from low nutrient soils showed higher fractional P translocation from both leaves and sapwood, but little patterning with respect to tissue nitrogen. While species from high and low nutrient soils clearly clustered along the soil-fertility axis, their tissue composition varied independently from plant functional traits related to construction costs and hydraulic anatomy. Our findings imply that there is considerable variation among species in the nutrient concentrations within different parenchyma tissues. The anatomical composition of wood tissue seems unrelated to plant nutrient requirements. Even though xylem parenchyma is involved in metabolic functions such as nutrient translocation and storage, parenchyma abundance on its own does not directly explain variation in these functions, even in co-occurring species. While parenchyma is highly abundant in wood of angiosperm trees, we are still lacking a convincing ecological interpretation of its variability and role in whole-tree nutrient budgets
People with enteral tubes and their carers' views of living with a tube and managing associated problems: a qualitative interview study.
No full textBackground: Nutrition by enteral tube is a complex therapy requiring significant management to ensure safe, timely delivery of nutrients and avoidance of complications. In the home setting people with enteral tubes and their carers are required to self-manage the therapy, including the need to cope with problems that arise. Whilst previous studies have conveyed experiences of people with enteral tubes, few have described views on enteral tube problems.
Aims and objectives: Drawing on the findings of a previously reported study (1), this paper aims to describe in-depth the experiences of people with enteral tubes and their carers of living with the tube day to day and managing problems that arise.
Design: A qualitative descriptive design using semi-structured in-depth interviews was employed.
Methods: A purposive sample of 19 people with enteral tubes and 15 carers of people with tubes participated. Interviews were recorded and transcribed. Using a thematic analysis approach, codes were defined and applied; themes developed and refined. Five themes with associated sub-themes were generated, of which one, “living with the tube”, is reported in-depth. The COREQ checklist was used.
Results:
Participants described the tube affecting both physical and psychosocial being and revealed it had resulted in significant changes to their daily living, necessitating adaptation to a new way of life. Participants reported spending much time and effort to manage tube problems, at times without support from healthcare practitioners knowledgeable in tube management. Discomfort associated with the tube was commonly described.
Conclusions:
Living with an enteral tube impacts significantly on daily life requiring adaptations to normal routine. People with tubes and their carers use a range of strategies to manage common complications.
Relevance to clinical practice:
Knowledge and understanding of how people with enteral tubes live with their tube and manage issues as they arise will enable healthcare practitioners to provide better support.
What does this paper contribute to the wider global community?
The number of people with enteral tubes living at home is increasing globally. People with enteral tubes and their carers are required to manage associated therapy and any issues that arise. Community nurses and other healthcare practitioners care for people with enteral tubes and need knowledge and understanding of the experience of living with a tube and managing associated problems to be able to provide appropriate support
Effects of body mass, climate, geography, and census area on population density of terrestrial mammals
No full textAim The aim of this study was to investigate the effects of climate, geography, census area and the distribution of body mass on the mass : density relationship in terrestrial mammal populations. Location The areas covered include most major terrestrial biomes including the tropics, savannas, and temperate forests. Method Data on population density and body mass from 827 populations belonging to 330 different terrestrial mammal species were derived from a review of the literature. Results LOWESS and polynomial regression analysis indicated that the overall mass : density relationship on log-log scales was not linear and that the slope of this relationship behaves differently across the range of body mass. Body mass explained between 37 and 67% of the variability in population density depending upon the dietary category or the biome group. We also developed two multivariate models that can explain up to 65% of the variability in population density in terrestrial mammals. We also tested for a confounding effect of census area on the mass : density relationship on log-log scales in terrestrial mammals. Conclusions Our findings support previous studies suggesting that body mass is a major predictor of the variance in population density in terrestrial mammals. We suggest that the nonlinearity of the mass : density relationship may result from the fact that the overall distribution of body mass is a mixture of distributions across dietary groups and biomes. In contrast to body mass, our results indicate that climatic and geographical factors have a minor effect on population density. Although census area was closely correlated with body mass, body mass was generally a better predictor of population density than was census area.PT: J; CR: BAKER RH, 1967, SYST ZOOL, V16, P28 BLACKBURN TM, 1990, J ANIM ECOL, V59, P335 BLACKBURN TM, 1993, J ANIM ECOL, V62, P694 BLACKBURN TM, 1996, BIODIVERSITY LETT, V3, P44 BLACKBURN TM, 1996, OIKOS, V75, P303 BLACKBURN TM, 1996, OIKOS, V77, P436 BLACKBURN TM, 1997, J ANIM ECOL, V66, P233 BLACKBURN TM, 1999, ADV ECOL RES, V28, P181 BLACKBURN TM, 1999, OIKOS, V85, P570 BOURLIERE F, 1961, INT UNION CONSERVATI, V1, P102 BROWN JH, 1981, AM ZOOL, V21, P877 BROWN JH, 1984, ACTA ZOOL FENN, V172, P45 BROWN JH, 1986, NATURE, V324, P248 BROWN JH, 1991, AM NAT, V138, P1478 BROWN JH, 1995, MACROECOLOGY BROWN JH, 1998, BIOGEOGRAPHY CAUGHLEY G, 1964, AUST J ZOOL, V12, P238 CHEW RM, 1970, ECOL MONOGR, V40, P1 CHURCHILL SK, 1991, WILDLIFE RES, V18, P343 CLEVELAND WS, 1979, J AM STAT ASSOC, V74, P829 CLEVELAND WS, 1985, SCIENCE, V229, P828 CLUTTONBROCK TH, 1977, J ZOOL LOND, V183, P1 COE MJ, 1976, OECOLOGIA, V22, P341 COTGREAVE P, 1992, FUNCT ECOL, V6, P248 COTGREAVE P, 1994, FUNCT ECOL, V8, P219 COTGREAVE P, 1994, OIKOS, V66, P353 COTGREAVE P, 1995, FUNCT ECOL, V9, P285 CURRIE DJ, 1993, OIKOS, V66, P353 CURRIE DJ, 1993, OIKOS, V67, P56 DAMUTH J, 1981, NATURE, V290, P699 DAMUTH J, 1987, BIOL J LINN SOC, V31, P193 DAMUTH J, 1993, NATURE, V365, P748 DOWSETT RJ, 1966, PUKU, V4, P135 EISENBERG JF, 1981, MAMMALIAN RAD ANAL T FLEMING TH, 1973, ECOLOGY, V54, P555 FREESE CH, 1982, INT J PRIMATOL, V3, P53 FRITZ H, 1994, P ROY SOC LOND B BIO, V256, P77 GRIFFITHS D, 1998, J ANIM ECOL, V67, P795 GUJARATI D, 1978, BASIC ECONOMETRICS HARVEY PH, 1991, COMP METHOD EVOLUTIO HUTCHINSON GE, 1959, AM NAT, V93, P145 JOHNSON CN, 1998, J ANIM ECOL, V67, P689 JOHNSON CN, 1999, OIKOS, V85, P565 JOHNSON RA, 1992, APPL MULTIVARIATE ST LODER N, 1997, OIKOS, V78, P195 MACPHERSON E, 1989, MAR ECOL-PROG SER, V50, P295 MARQUET PA, 1990, SCIENCE, V250, P1125 MARQUET PA, 1995, J ANIM ECOL, V64, P325 MARQUET PA, 1998, EVOL ECOL, V12, P127 MARQUET PA, 1999, OIKOS, V85, P299 MONTFORT A, 1972, TERRE VIE, V26, P216 NEE S, 1991, NATURE, V351, P312 NOWAK RM, 1991, WALKERS MAMMALS WORL, V1 NOWAK RM, 1991, WALKERS MAMMALS WORL, V2 PERES CA, 1990, BIOL CONSERV, V54, P47 PETERS RH, 1983, OECOLOGIA, V60, P89 PETERS RH, 1984, AM NAT, V124, P498 PHILLIPSON J, 1975, E AFR WILDL J, V13, P171 PIMM SL, 1992, BALANCE NATURE RAPOPORT EH, 1982, AREOGRAPHY GEOGRAPHI, V1 RICKLEFS RE, 1996, OIKOS, V77, P167 ROBERTS SC, 1991, AFR J ECOL, V29, P316 ROBINSON JG, 1986, AM NAT, V128, P665 ROSENZWEIG ML, 1968, AM NAT, V102, P67 SILVA M, 1994, CONSERV BIOL, V8, P732 SILVA M, 1995, AM NAT, V145, P704 SILVA M, 1997, J ANIM ECOL, V66, P327 SMALLWOOD KS, 1996, OECOLOGIA, V107, P588 SOKAL RR, 1981, BIOMETRY STEVENS GC, 1989, AM NAT, V133, P240 WAND MP, 1995, KERNEL SMOOTHING WERNSTEDT FL, 1972, WORLD CLIMATIC DATA WESTOBY M, 1995, J ECOL, V83, P531 WESTOBY M, 1995, J ECOL, V83, P727 WESTOBY M, 1995, J ECOL, V83, P892 WHITTAKER RH, 1975, COMMUNITIES ECOSYSTE WILSON DE, 1992, MAMMAL SPECIES WORLD WILSON JW, 1974, EVOLUTION, V28, P124 ZAR JH, 1996, BIOSTATISTICAL ANAL; NR: 79; TC: 12; J9: GLOBAL ECOL BIOGEOGR; PG: 17; GA: 482PLSource type: Electronic(1
Testing models of biological scaling with mammalian population densities
No full textTwo hypotheses have been suggested to explain the form of interspecific scaling of organismal characteristics to body size, such as the well-known increase in total metabolism with body mass. A hypothesis based on simple Euclidean geometry suggests that the scaling of many biological variables to body size should have a scaling exponent of 2/3, or approximate to0.667. On the other hand, according to a hypothesis based on fractal dimensions, the relationship between biological variables and body mass should have a scaling exponent of 0.750. We conducted a power analysis of the predicted exponents of scaling under the Euclidean and fractal hypotheses, using average adult body masses and population densities collected from the published literature on mammalian species. The collected data reflect 987 mammal populations from a broad variety of terrestrial habitats. Using statistical methods we determined the sample sizes required to decide between the values of the scaling exponent of the density-to-mass relationship based on the Euclidean (-0.667) and fractal (-0.750) hypotheses. Non-linearities in the dataset and insufficient power plagued our tests of the predictions. We found that mammalian species weighing less than 100 kg had a linear scaling pattern, sufficient power to reveal a difference between the scaling coefficients -0.667 and -0.750, and an actual scaling coefficient of -0.719 (barely significantly different from -0.667 but not from -0.750). Thus, our results support the fractal hypothesis, though the support was not particularly strong, which suggests that the relationship between body mass and population density should have a scaling exponent of -0.750.PT: J; CR: BANAVAR JR, 1999, NATURE, V399, P130 BLACKBURN TM, 1997, J ANIM ECOL, V66, P233 BROWN JH, 1998, BIOGEOGRAPHY CALDER WA, 1984, SIZE FUNCTION LIFE H COTGREAVE P, 1995, FUNCT ECOL, V9, P285 CURRIE DJ, 1993, OIKOS, V66, P353 CURRIE DJ, 1993, OIKOS, V67, P56 DAMUTH J, 1981, NATURE, V290, P699 DAMUTH J, 1987, BIOL J LINN SOC, V31, P193 DAMUTH J, 1993, NATURE, V365, P748 DOWSETT RJ, 1966, PUKU, V4, P135 DUTOIT JT, 1989, AM NAT, V133, P736 EISENBHERG JF, 1981, MAMMALIAN RAD ANAL T ENQUIST BJ, 1998, NATURE, V395, P163 ENQUIST BJ, 1999, NATURE, V401, P907 GRIFFITHS D, 1987, NATURE, V328, P117 GRIFFITHS D, 1998, J ANIM ECOL, V67, P795 HARVEY PH, 1991, COMP METHOD EVOLUTIO KELT DA, 1999, ECOLOGY, V80, P337 LAWTON JH, 1989, OIKOS, V55, P429 MARQUET PA, 1990, SCIENCE, V250, P1125 MARQUET PA, 1995, J ANIM ECOL, V64, P325 MARQUET PA, 1998, EVOL ECOL, V12, P127 MCMAHON TA, 1976, J THEOR BIOL, V59, P443 MONTFORT A, 1972, TERRE VIE, V26, P216 NIKLAS KJ, 2001, P NATL ACAD SCI USA, V98, P2922 NOWAK RM, 1991, WALKERS MAMMALS WORL, V1 NOWAK RM, 1991, WALKERS MAMMALS WORL, V2 PETERS RH, 1983, ECOLOGICAL IMPLICATI PETERS RH, 1983, OECOLOGIA, V60, P89 PETERS RH, 1984, AM NAT, V124, P498 PIMM SL, 1991, BALANCE NATURE ECOLO POLISHCHUK LV, 1999, OIKOS, V86, P544 ROBINSON JG, 1986, AM NAT, V128, P665 SCHMIDTNIELSON K, 1984, SCALING WHY IS ANIMA SILVA M, 1995, AM NAT, V145, P704 SILVA M, 1995, CRC HDB MAMMALIAN BO SILVA M, 1997, J ANIM ECOL, V66, P327 SILVA M, 2001, GLOBAL ECOL BIOGEOGR, V10, P469 WEST GB, 1997, SCIENCE, V276, P122 WEST GB, 1999, SCIENCE, V284, P1677 WESTOBY M, 1995, J ECOL, V83, P531 WESTOBY M, 1995, J ECOL, V83, P727 WESTOBY M, 1995, J ECOL, V83, P892; NR: 44; TC: 4; J9: CAN J ZOOL; PG: 8; GA: 698CTSource type: Electronic(1
The evolution of plant functional variation: traits, spectra, and strategies
No full text© 2003 by University of ChicagoVariation in plant functional traits results from evolutionary and environmental drivers that operate at a variety of different scales, which makes it a challenge to differentiate among them. In this article we describe patterns of functional trait variation and trait correlations within and among habitats in relation to several environmental and trade‐off axes. We then ask whether such patterns reflect natural selection and can be considered plant strategies. In so doing we highlight evidence that demonstrates that (1) patterns of trait variation across resource and environmental gradients (light, water, nutrients, and temperature) probably reflect adaptation, (2) plant trait variation typically involves multiple‐correlated traits that arise because of inevitable trade‐offs among traits and across levels of whole‐plant integration and that must be understood from a whole‐plant perspective, and (3) such adaptation may be globally generalizable for like conditions; i.e., the set of traits (collections of traits in syndromes) of taxa can be considered as “plant strategies.”Reich, Peter B; Wright, I J; Cavender‐Bares, J; Craine, J M; Oleksyn, J; Westoby, M; Walters, M B. (2003). The evolution of plant functional variation: traits, spectra, and strategies. Retrieved from the University Digital Conservancy, 10.1086/374368
Specialized strategies I: seedlings in stressful environments
No full textIntroduction Seedlings are particularly susceptible to harsh conditions. Indeed, the seedling stage is considered to be the most vulnerable stage in the life of the plant (Stebbins, 1971; Fenner, 1987; Fenner & Thompson 2005) because even small reductions in biomass may lead to the death of the plant (Dirzo, 1985; Fenner & Thompson, 2005). Selection has favored strategies that reduce the high risk of the seedling stage primarily in two ways: first, maternal deployment of optimal amount of reserves to ensure maximum likelihood of seedling survival (Smith & Fretwell, 1974; Westoby et al., 1992; Leishman & Westoby, 1994a; Leishman et al., 2000), and second, timing of germination to avoid emergence during periods of high environmental stress as well as during transient favorable conditions too short to ensure postemergence survivorship (Grime, 1979; Baskin & Baskin, 1989, 1998; Fenner & Thompson, 2005). However precise the mechanism to adjust germination to low-risk conditions may be, many environments present inherently high risks for seedlings because the stress is chronic or favorable conditions are intermittent and uncertain (see Table 3.1). Because the ability of the seedling to accumulate or replace biomass decreases as the environment becomes less favorable, seedlings in stressful environments are at higher risk of mortality. Furthermore, when postemergence mortality is highly probable, avoidance of stress per se is not a viable strategy and seedlings are selected to tolerate stressful conditions.Jose M. Facellihttp://www.amazon.com/Seedling-Ecology-Evolution-Mary-Allessio/dp/0521873053#noo
Response inhibition is linked to emotional devaluation: behavioural and electrophysiological evidence
No full textTo study links between the inhibition of motor responses and emotional evaluation, we combined electrophysiological measures of prefrontal response inhibition with behavioural measures of affective evaluation. Participants first performed a Go-Nogo task in response to Asian and Caucasian faces (with race determining their Go or Nogo status), followed by a trustworthiness rating for each face. Faces previously seen as Nogo stimuli were rated as less trustworthy than previous Go stimuli. To study links between the efficiency of response inhibition in the Go-Nogo task and subsequent emotional evaluations, the Nogo N2 component was quantified separately for faces that were later judged to be high versus low in trustworthiness. Nogo N2 amplitudes were larger in response to low-rated as compared to high-rated faces, demonstrating that trial-by-trial variations in the efficiency of response inhibition triggered by Nogo faces, as measured by the Nogo N2 component, co-vary with their subsequent affective evaluation. These results suggest close links between inhibitory processes in top-down motor control and emotional responses
Data and code for: Partitioning mortality into growth-dependent and growth-independent hazards across 203 tropical tree species (PNAS).
No full textPartitioning mortality into growth-dependent and growth-independent hazards across 203 tropical tree speciesJames S Camac, Richard Condit, Richard G FitzJohn, Lachlan McCalman,Daniel Steinberg, Mark Westoby, Joe Wright, Daniel FalsterWe present a model that partitions rates of tropical tree mortality into growth-dependent and growth-independent hazards. This creates the opportunity to examine the relative contributions of within-species and across-species variation on tropical tree mortality rates, but also, how species traits affect each hazard. We parameterize this model using >400,000 observed survival records collected over a 15-year period at Barro Colorado Island from more than 180,000 individuals across 203 species. We show that marginal carbon budgets are a major contributor to tree death on Barro Colorado Island. Moreover, we found that while species' light demand, maximum dbh and wood density affected tree mortality in different ways, they explained only a small fraction of the total variability observed among species.This repository contains the data and code required to reproduce our entire workflow from data cleaning, rerunning the analysis, producing figures and reproducing the manuscript.## PublicationCamac, J.S., Condit, R., FitzJohn, R.G., McCalman, L., Steinberg, D., Westoby, M., Wright, S.J., Falster, D. (Accepted at PNAS) Partitioning mortality into growth-dependent and growth-independent hazards across 203 tropical tree species.</div
Low-budget topographic surveying comes of age: Structure from motion photogrammetry in geography and the geosciences
No full textThis is the author accepted manuscript. The final version is available from SAGE Publicarions via the DOI in this record
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