Just as people with the same weight can have different body builds, woods with the same wood density can have different anatomies. Here, our aim was to assess the magnitude of anatomical variation ...within a restricted range of wood density and explore its potential ecological implications.
Twig wood of 69 angiosperm tree and shrub species was analyzed. Species were selected so that wood density varied within a relatively narrow range (0.38-0.62 g cm-3). Anatomical traits quantified included wood tissue fractions (fibres, axial parenchyma, ray parenchyma, vessels, and conduits with maximum lumen diameter below 15 μm), vessel properties, and pith area. To search for potential ecological correlates of anatomical variation the species were sampled across rainfall and temperature contrasts, and several other ecologically-relevant traits were measured (plant height, leaf area to sapwood area ratio, and modulus of elasticity).
Despite the limited range in wood density, substantial anatomical variation was observed. Total parenchyma fraction varied from 0.12 to 0.66 and fibre fraction from 0.20 to 0.74, and these two traits were strongly inversely correlated (r = -0.86, P < 0.001). Parenchyma was weakly (0.24 ≤|r|≤ 0.35, P < 0.05) or not associated with vessel properties nor with height, leaf area to sapwood area ratio, and modulus of elasticity (0.24 ≤|r|≤ 0.41, P < 0.05). However, vessel traits were fairly well correlated with height and leaf area to sapwood area ratio (0.47 ≤|r|≤ 0.65, all P < 0.001). Modulus of elasticity was mainly driven by fibre wall plus vessel wall fraction rather than by the parenchyma component.
Overall, there seem to be at least three axes of variation in xylem, substantially independent of each other: a wood density spectrum, a fibre-parenchyma spectrum, and a vessel area spectrum. The fibre-parenchyma spectrum does not yet have any clear or convincing ecological interpretation.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
In a multicenter randomized trial comparing nasal high-flow therapy with continuous positive airway pressure (CPAP) as initial respiratory support for newborns in nontertiary special care nurseries, ...high-flow therapy was not noninferior to CPAP and resulted in a significantly higher incidence of treatment failure.
Canine babesiosis is a parasitic disease caused by apicomplexan protozoa of the genus Babesia, with Babesia canis being a pathogenic and widespread species in mainland Europe. The United Kingdom has ...thought to have been free of endemic B. canis infection, despite its vector, Dermacentor reticulatus being present in endemic foci. The winter of 2015/2016 saw the establishment of the first recording of a known endemic foci of B. canis in the UK. Since this outbreak in Harlow and subsequent cases in Romford later in 2016, information has been gathered regarding the population of Dermacentor ticks in Harlow and awareness of the disease promoted among Veterinary professionals and pet owners. This letter describes what is known about the two clusters of cases seen in 2016 and the distribution of D. reticulatus in the UK. A further untraveled case in the UK in 2017 close proximity to the 2016 cases is also described, as well as the lessons this outbreak brings in terms of managing other vector-borne disease.
The leaf economics spectrum (LES) represents a suite of intercorrelated leaf traits concerning construction costs per unit leaf area, nutrient concentrations, and rates of carbon fixation and tissue ...turnover. Although broad trade-offs among leaf structural and physiological traits have been demonstrated, we still do not have a comprehensive view of the fundamental constraints underlying the LES trade-offs.
Here, we investigated physiological and structural mechanisms underpinning the LES by analysing a novel data compilation incorporating rarely considered traits such as the dry mass fraction in cell walls, nitrogen allocation, mesophyll CO2 diffusion and associated anatomical traits for hundreds of species covering major growth forms.
The analysis demonstrates that cell wall constituents are major components of leaf dry mass (18–70%), especially in leaves with high leaf mass per unit area (LMA) and long lifespan. A greater fraction of leaf mass in cell walls is typically associated with a lower fraction of leaf nitrogen (N) invested in photosynthetic proteins; and lower within-leaf CO2 diffusion rates, as a result of thicker mesophyll cell walls.
The costs associated with greater investments in cell walls underpin the LES: long leaf lifespans are achieved via higher LMA and in turn by higher cell wall mass fraction, but this inevitably reduces the efficiency of photosynthesis.
To determine whether male gender has an effect on survival, early neonatal morbidity, and long-term outcome in neonates born extremely prematurely.
Retrospective review of the New South Wales and ...Australian Capital Territory Neonatal Intensive Care Unit Data Collection of all infants admitted to New South Wales and Australian Capital Territory neonatal intensive care units between January 1998 and December 2004. The primary outcome was hospital mortality and functional impairment at 2 to 3 years follow-up.
Included in the study were 2549 neonates; 54.7% were male. Risks of grade III/IV intraventricular hemorrhage, sepsis, and major surgery were found to be increased in male neonates. Hospital mortality (odds ratio 1.285, 95% confidence interval 1.035-1.595) and moderate to severe functional disability at 2 to 3 years of age (odds ratio 1.877, 95% confidence interval 1.398-2.521) were more likely in male infants. Gender differences for mortality and long-term neurologic outcome loses significance at 27 weeks gestation.
In the modern era of neonatal management, male infants still have higher mortality and poorer long-term neurologic outcome. Gender differences for mortality and long-term neurologic outcome appear to lose significance at 27 weeks gestation.
A roadmap to plant functional island biogeography Schrader, Julian; Wright, Ian J.; Kreft, Holger ...
Biological reviews of the Cambridge Philosophical Society,
December 2021, 2021-12-00, 20211201, Letnik:
96, Številka:
6
Journal Article
Recenzirano
Odprti dostop
ABSTRACT
Island biogeography is the study of the spatio‐temporal distribution of species, communities, assemblages or ecosystems on islands and other isolated habitats. Island diversity is structured ...by five classes of process: dispersal, establishment, biotic interactions, extinction and evolution. Classical approaches in island biogeography focused on species richness as the deterministic outcome of these processes. This has proved fruitful, but species traits can potentially offer new biological insights into the processes by which island life assembles and why some species perform better at colonising and persisting on islands.
Functional traits refer to morphological and phenological characteristics of an organism or species that can be linked to its ecological strategy and that scale up from individual plants to properties of communities and ecosystems. A baseline hypothesis is for traits and ecological strategies of island species to show similar patterns as a matched mainland environment. However, strong dispersal, environmental and biotic‐interaction filters as well as stochasticity associated with insularity modify this baseline. Clades that do colonise often embark on distinct ecological and evolutionary pathways, some because of distinctive evolutionary forces on islands, and some because of the opportunities offered by freedom from competitors or herbivores or the absence of mutualists. Functional traits are expected to be shaped by these processes.
Here, we review and discuss the potential for integrating functional traits into island biogeography. While we focus on plants, the general considerations and concepts may be extended to other groups of organisms. We evaluate how functional traits on islands relate to core principles of species dispersal, establishment, extinction, reproduction, biotic interactions, evolution and conservation. We formulate existing knowledge as 33 working hypotheses. Some of these are grounded on firm empirical evidence, others provide opportunities for future research.
We organise our hypotheses under five overarching sections. Section A focuses on plant functional traits enabling species dispersal to islands. Section B discusses how traits help to predict species establishment, successional trajectories and natural extinctions on islands. Section C reviews how traits indicate species biotic interactions and reproduction strategies and which traits promote intra‐island dispersal. Section D discusses how evolution on islands leads to predictable changes in trait values and which traits are most susceptible to change. Section E debates how functional ecology can be used to study multiple drivers of global change on islands and to formulate effective conservation measures.
Islands have a justified reputation as research models. They illuminate the forces operating within mainland communities by showing what happens when those forces are released or changed. We believe that the lens of functional ecology can shed more light on these forces than research approaches that do not consider functional differences among species.
A novel framework is presented for the analysis of ecophysiological field measurements and modelling. The hypothesis ‘leaves minimise the summed unit costs of transpiration and carboxylation’ ...predicts leaf‐internal/ambient CO2 ratios (ci/ca) and slopes of maximum carboxylation rate (Vcmax) or leaf nitrogen (Narea) vs. stomatal conductance. Analysis of data on woody species from contrasting climates (cold‐hot, dry‐wet) yielded steeper slopes and lower mean ci/ca ratios at the dry or cold sites than at the wet or hot sites. High atmospheric vapour pressure deficit implies low ci/ca in dry climates. High water viscosity (more costly transport) and low photorespiration (less costly photosynthesis) imply low ci/ca in cold climates. Observed site‐mean ci/ca shifts are predicted quantitatively for temperature contrasts (by photorespiration plus viscosity effects) and approximately for aridity contrasts. The theory explains the dependency of ci/ca ratios on temperature and vapour pressure deficit, and observed relationships of leaf δ13C and Narea to aridity.
Global climatic drivers of leaf size Wright, Ian J.; Dong, Ning; Maire, Vincent ...
Science (American Association for the Advancement of Science),
09/2017, Letnik:
357, Številka:
6354
Journal Article
Recenzirano
Odprti dostop
Leaf size varies by over a 100,000-fold among species worldwide. Although 19th-century plant geographers noted that the wet tropics harbor plants with exceptionally large leaves, the latitudinal ...gradient of leaf size has not been well quantified nor the key climatic drivers convincingly identified. Here, we characterize worldwide patterns in leaf size. Large-leaved species predominate in wet, hot, sunny environments; small-leaved species typify hot, sunny environments only in arid conditions; small leaves are also found in high latitudes and elevations. By modeling the balance of leaf energy inputs and outputs, we show that daytime and nighttime leaf-to-air temperature differences are key to geographic gradients in leaf size. This knowledge can enrich “next-generation” vegetation models in which leaf temperature and water use during photosynthesis play key roles.
Summary 565 I. LMA in perspective 566 II. LMA in the field 567 III. Inherent differences 568 IV. Relation with anatomy and chemical composition 570 V. Environmental effects 572 VI. Differences in ...space and time 577 VII. Molecular regulation and physiology 579 VIII. Ecological consequences 580 IX. Conclusions and perspectives 582 Acknowledgements 582 References 582 Appendices 587
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