4,539 research outputs found
System parameters of X-ray binaries
No full textEThOS - Electronic Theses Online ServiceGBUnited Kingdo
Dispersal traits determine passive restoration trajectory of a Nigerian montane forest
No full textPassive restoration methods offer great promise for tropical regions where resources are limited but the success of such efforts can be variable. Using trait-based theory, we investigated the likely trajectories of passive restoration efforts in a degraded Nigerian montane forest system recently protected from burning and cattle grazing. We quantified the density, species richness, and functional trait dispersion of dispersed seeds and seedling communities at increasing distances from the forest edge. We then determined which plant traits are responsible for colonisation by quantifying changes in functional-trait dispersion and relative frequencies of dispersal-linked traits with increasing distance from the forest. We found a rapid decrease in density and species richness, and significant species turnover in both seeds and seedlings just beyond the forest edge. This was mirrored by a significant decline in functional-trait dispersion and a shift in the relative frequencies of dispersal-linked traits. These findings suggest that the reassembly of plant communities adjacent to remnant forest is dependent on functional traits present in these remnant source populations, providing support for the incorporation of trait-based theory in restoration management. (C) 2014 Elsevier Masson SAS. All rights reserved
Repositioning the graphic designer as researcher
No full textIn academic terms, the discipline of graphic design is relatively young. Consequently the position of the discipline within academic territory, and the role of the designer, continue to be debated. In part, these debates have been a product of attempts to define and defend the discipline’s borders from within, in order to establish a sense of the role of graphic design and the graphic designer as commensurate with other disciplines both within and beyond art and design. In recent years graphic designers have variously been defined as ‘authors’, ‘producers’ and ‘readers’, yet none of these definitions seem to have provided any kind of productive or lasting impact within the academy. This paper suggests that rather than continue to seek territorial definitions and positions from within, it could be more productive to look beyond the confines of the discipline. Gaining a broader, interdisciplinary perspective on, and understanding of, qualitative research methods from other disciplines may enable the graphic designer to more fully position his or her practice within the wider academy. Such a perspective could help facilitate the repositioning and redefinition of the graphic designer as ‘researcher’ - a move that would be productive in relation to the future development of postgraduate research within the discipline
Decreasing Stoichiometric Resource Quality Drives Compensatory Feeding across Trophic Levels in Tropical Litter Invertebrate Communities
No full textLiving organisms are constrained by both resource quantity and quality. Ecological stoichiometry offers important insights into how the elemental composition of resources affects their consumers. If resource quality decreases, consumers can respond by shifting their body stoichiometry, avoiding low-quality resources, or up-regulating feeding rates to maintain the supply of required elements while excreting excess carbon (i.e., compensatory feeding). We analyzed multitrophic consumer body stoichiometry, biomass, and feeding rates along a resource-quality gradient in the litter of tropical forest and rubber and oil-palm plantations. Specifically, we calculated macroinvertebrate feeding rates based on consumer metabolic demand and assimilation efficiency. Using linear mixed effects models, we assessed resource-quality effects on macroinvertebrate detritivore and predator communities. We did not detect shifts in consumer body stoichiometry or decreases in consumer biomass in response to declining resource quality, as indicated by increasing carbon-to-nitrogen ratios. However, across trophic levels, we found a strong indication of decreasing resource quality leading to increased consumer feeding rates through altered assimilation efficiency and community body size structure. Our study reveals the influence of resource quality on multitrophic consumer feeding rates and suggests compensatory feeding to be more common across consumer trophic levels than was formerly known
Resource stoichiometry and availability modulate species richness and biomass of tropical litter macro-invertebrates
No full text1. The high biodiversity and biomass of soil communities is crucial for litter decomposition in terrestrial ecosystems such as tropical forests. However, the leaf litter that these communities consume is of particularly poor quality as indicated by elemental stoichiometry. The impact of resource quantity, quality, and other habitat parameters on species richness and biomass of consumer communities is often studied in isolation, although much can be learned from simultaneously studying both community characteristics.
2. Using a data set of 780 macro-invertebrate consumer species across 32 sites in tropical lowland rainforest and agricultural systems on Sumatra, Indonesia, we investigated the effects of basal resource stoichiometry (C:X ratios of N, P, K, Ca, Mg, Na, S in local leaf litter), litter mass (basal resource quantity and habitat space), plant species richness (surrogate for litter habitat heterogeneity), and soil pH (acidity) on consumer species richness and biomass across different consumer groups (i.e., three feeding guilds and ten selected taxonomic groups).
3. In order to distinguish the most important predictors of consumer species richness and biomass, we applied a standardised model averaging approach investigating the effects of basal resource stoichiometry, litter mass, plant species richness, and soil pH on both consumer community characteristics. This standardised approach enabled us to identify differences and similarities in the magnitude and importance of such effects on consumer species richness and biomass.
4. Across consumer groups, we found litter mass to be the most important predictor of both species richness and biomass. Resource stoichiometry had a more pronounced impact on consumer species richness than on their biomass. As expected, taxonomic groups differed in which resource and habitat parameters (basal resource stoichiometry, litter mass, plant species richness, and pH) were most important for modulating their community characteristics.
5. The importance of litter mass for both species richness and biomass indicates that these tropical consumers strongly depend on habitat space and resource availability. Our study supports previous theoretical work indicating that consumer species richness is jointly influenced by resource availability and the balanced supply of multiple chemical elements in their resources
Species richness and biomass explain spatial turnover in ecosystem functioning across tropical and temperate ecosystems
No full textPredicting ecosystem functioning at large spatial scales rests on our ability to scale up from local plots to landscapes, but this is highly contingent on our understanding of how functioning varies through space. Such an understanding has been hampered by a strong experimental focus of biodiversity–ecosystem functioning research restricted to small spatial scales. To address this limitation, we investigate the drivers of spatial variation in multitrophic energy flux—a measure of ecosystem functioning in complex communities—at the landscape scale. We use a structural equation modelling framework based on distance matrices to test how spatial and environmental distances drive variation in community energy flux via four mechanisms: species composition, species richness, niche complementarity and biomass. We found that in both a tropical and a temperate study region, geographical and environmental distance indirectly influence species richness and biomass, with clear evidence that these are the dominant mechanisms explaining variability in community energy flux over spatial and environmental gradients. Our results reveal that species composition and trait variability may become redundant in predicting ecosystem functioning at the landscape scale. Instead, we demonstrate that species richness and total biomass may best predict rates of ecosystem functioning at larger spatial scales.</jats:p
Unheralded Historian: Mary Sheldon Barnes and Primary Source Material in History Books
No full textABSTRACT
UNHERALDED HISTORIAN: MARY SHELDON BARNES AND PRIMARY SOURCE MATERIAL IN HISTORY BOOKS
by
James A. Chisholm, Jr.
In the latter part of the nineteenth century, Mary Sheldon Barnes emerged as a leading historical methods professor and history textbook author. Although men dominated the field, she wrote several articles and books alone or with her husband Earl Barnes about primary source materials and teaching. She lived during an era in United States history when education was evolving. Students studied traditional subjects such as grammar, mathematics, and Latin using rote memorization. Students who failed to learn classroom material faced varying degrees of punishment from teachers. Classroom pedagogy in the nineteenth century was teacher-focused and teachers often employed a considerable amount of physical fear.
Mary Sheldon Barnes developed her pedagogy and writing style using scientific history and German seminary style classrooms. As a teacher, she taught in a normal school, gender specific college, and a co-educational institution of higher learning and these experiences impacted her pedagogy. Barnes rejected the regimented, teacher-centered, memorization/recitation pedagogy of the nineteenth century. She preferred a teaching style that provided more student-centered, discussion-oriented history pedagogy.
This study utilizes biography as a format to explore Mary Sheldon Barnes as a pioneer teacher and author. Following her death, history textbook authors turned away from source material textbooks back to traditional chronological design and ignored her contributions to social education history. This dissertation provides an examination of her life and explores its influence on contemporary textbooks and pedagogy
Data from: Individual behaviour mediates effects of warming on movement across a fragmented landscape
No full textGlobal warming and habitat fragmentation impose dramatic and potentially interactive impacts on ecosystems. Warming induces shifts in species' distributions as they track temperature changes, but this can be hindered in fragmented landscapes. Corridors connecting habitat patches might ameliorate the combined effects of fragmentation and global warming. Using novel automated tracking methods, the movement of woodlice (Oniscus asellus) ranging in body size from 15·3 to 108·6 mg was quantified across a temperature range from 15 to 25 °C as they moved around an experimental fragmented landscape. We used confirmatory path analysis to test causal effects of temperature and body size on individual movement and corridor crossing rates between two habitat patches. Results showed that woodlice behaved differently in corridors than patches by moving, on average, faster and more often. This is congruent with natural systems where corridors generally provide lower quality habitat than patches. Although metabolic theory suggests positive scaling of movement with body temperature (up to a peak) and body size, we found that corridor crossing rate was (i) not directly affected by body size and (ii) negatively influenced by temperature, possibly due to its indirect effects via humidity. Our path model revealed that metabolic scaling could only explain temperature effects on maximum body velocity, but decision-based behaviour explained most variation in corridor crossing rates. This led to direct and indirect effects of temperature and size on individual movement between habitat patches. Our findings suggest that increasing mean global temperatures, coupled with increasing habitat fragmentation, could have synergistic negative impacts on populations through a combination of physiological and behavioural factors that mediate individual responses to temperature and fragmentation
The role of species traits in mediating functional recovery during matrix restoration.
No full textReversing anthropogenic impacts on habitat structure is frequently successful through restoration, but the mechanisms linking habitat change, community reassembly and recovery of ecosystem functioning remain unknown. We test for the influence of edge effects and matrix habitat restoration on the reassembly of dung beetle communities and consequent recovery of dung removal rates across tropical forest edges. Using path modelling, we disentangle the relative importance of community-weighted trait means and functional trait dispersion from total biomass effects on rates of dung removal. Community trait composition and biomass of dung beetle communities responded divergently to edge effects and matrix habitat restoration, yielding opposing effects on dung removal. However, functional dispersion--used in this study as a measure of niche complementarity--did not explain a significant amount of variation in dung removal rates across habitat edges. Instead, we demonstrate that the path to functional recovery of these altered ecosystems depends on the trait-mean composition of reassembling communities, over and above purely biomass-dependent processes that would be expected under neutral theory. These results suggest that any ability to manage functional recovery of ecosystems during habitat restoration will demand knowledge of species' roles in ecosystem processes
Molecular fluorescence above metallic gratings
No full textP. Andrew and William L. Barnes, Physical Review B, Vol. 64, article 125405 (2001). Copyright © 2001 by the American Physical Society.We present measurements of the fluorescence of emitters located in close proximity (d<λ) to metallic grating surfaces. By measuring both the spontaneous emission lifetime and angle-dependent radiation pattern of a monolayer of dye molecules as a function of their separation from planar and periodically corrugated mirrors of increasing modulation depth, we are able to examine the effect of varying the surface profile on the emission process. Both the distance dependence of the lifetime and the spatial distribution of the emitted light are significantly changed upon the introduction of a corrugation, quite apart from the appearance of the familiar Bragg-scattered bound-mode features. It is postulated that these perturbations arise from the interference of the grating scattered dipole fields with the usual upward propagating and reflected fields. In addition, the measurement of nonexponential decay transients for the deepest gratings examined provide evidence for the existence of optically dissimilar dipole positions above the grating surface
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