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Spatial Context (spatial + context)
Selected AbstractsSouth Africa's Current Transition in Temporal and Spatial ContextANTIPODE, Issue 2 2000Alan Leater This article analyses South Africa's current postapartheid transition in the light of earlier transformations of its social and economic order. The first of these prior transformations is the abolition of slavery and the shift to liberal capitalism, which took place in the early nineteenth century. The second is the rapid industrialization of the late nineteenth and early twentieth centuries. Each of these transformations, as well as the current transition, is explained as being partly the outcome of a broad shift in capitalist practice, innovated in the metropoles of the global economy. Due to South Africa's situation within global economic networks, each of these shifts, at different times, raised the threat of a dislocation in South Africa's prevailing social order. However, each prior transformation and, it will be argued, the current transition, has been ,managed' by established elites so as to ensure minimal change to the overall distribution of privilege. This conservative ,management' of shifts in capitalist practice, it is suggested, has been facilitated through South African elites' historic engagement with cultural discourses circulating across a global terrain. In this article then, contemporary South Africa is located within both material and discursive networks which have historically influenced the country's distribution of privilege. [source] Resettlement, Rights to Development and the Ilisu Dam, TurkeyDEVELOPMENT AND CHANGE, Issue 4 2004Behrooz Morvaridi A cursory attempt to measure the extent of displacement over the past two decades indicates significant increases in conflict-induced displacement and displacement resulting from development projects. At the same time a growing opposition to the latter form of displacement has raised questions over its legitimacy through a variety of media, including public campaigns and protests. This article focuses on some of the challenges that this presents to the displacement and resettlement discourse. In particular it considers the influences of the rights to development agenda on the spatial context of displacement and its associated economic and political changes. There appears to be a disjuncture between the practices of mainstream development, which tend to interpret development policy as it is defined and applied by a nation state and to assess inequalities within clear geographical definitions, and the universality of a rights based approach to development. This article examines these tensions in the context of displacement and resettlement management, drawing on evidence from a case study of the Ilisu dam in South East Anatolia, Turkey. [source] Representing genetic variation as continuous surfaces: an approach for identifying spatial dependency in landscape genetic studiesECOGRAPHY, Issue 6 2008Melanie A. Murphy Landscape genetics, an emerging field integrating landscape ecology and population genetics, has great potential to influence our understanding of habitat connectivity and distribution of organisms. Whereas typical population genetics studies summarize gene flow as pairwise measures between sampling localities, landscape characteristics that influence population genetic connectivity are often continuously distributed in space. Thus, there are currently gaps in both the ability to analyze genotypic data in a continuous spatial context and our knowledge of expected of landscape genetic structure under varying conditions. We present a framework for generating continuous "genetic surfaces", evaluate their statistical properties, and quantify statistical behavior of landscape genetic structure in a simple landscape. We simulated microsatellite genotypes under varying parameters (time since vicariance, migration, effective population size) and used ancestry (q) values from STRUCTURE to interpolate a genetic surface. Using a spatially adjusted Pearson's correlation coefficient to test the significance of landscape variable(s) on genetic structure we were able to detect landscape genetic structure on a contemporary time scale (,5 generations post vicariance, migration probability ,0.10) even when population differentiation was minimal (FST,0.00015). We show that genetic variation can be significantly correlated with geographic distance even when genetic structure is due to landscape variable(s), demonstrating the importance of testing landscape influence on genetic structure. Finally, we apply genetic surfacing to analyze an empirical dataset of black bears from northern Idaho USA. We find black bear genetic variation is a function of distance (autocorrelation) and habitat patch (spatial dependency), consistent with previous results indicating genetic variation was influenced by landscape by resistance. These results suggest genetic surfaces can be used to test competing hypotheses of the influence of landscape characteristics on genetic structure without delineation of categorical groups. [source] Functional biodiversity of macroinvertebrate assemblages along major ecological gradients of boreal headwater streamsFRESHWATER BIOLOGY, Issue 9 2005JANI HEINOArticle first published online: 3 AUG 200 Summary 1. Biodiversity,environment relationships are increasingly well-understood in the context of species richness and species composition, whereas other aspects of biodiversity, including variability in functional diversity (FD), have received rather little rigorous attention. For streams, most studies to date have examined either taxonomic assemblage patterns or have experimentally addressed the importance of species richness for ecosystem functioning. 2. I examined the relationships of the functional biodiversity of stream macroinvertebrates to major environmental and spatial gradients across 111 boreal headwater streams in Finland. Functional biodiversity encompassed functional richness (FR , the number of functional groups derived from a combination of functional feeding groups and habit trait groups), FD , the number of functional groups and division of individuals among these groups, and functional evenness (FE , the division of individuals among functional groups). Furthermore, functional structure (FS) comprised the composition and abundance of functional groups at each site. 3. FR increased with increasing pH, with additional variation related to moss cover, total nitrogen, water colour and substratum particle size. FD similarly increased with increasing pH and decreased with increasing canopy cover. FE decreased with increasing canopy cover and water colour. Significant variation in FS was attributable to pH, stream width, moss cover, substratum particle size, nitrogen, water colour with the dominant pattern in FS being related to the increase of shredder-sprawlers and the decrease of scraper-swimmers in acidic conditions. 4. In regression analysis and redundancy analysis, variation in functional biodiversity was not only related to local environmental factors, but a considerable proportion of variability was also attributable to spatial patterning of environmental variables and pure spatial gradients. For FR, 23.4% was related to pure environmental effects, 15.0% to shared environmental and spatial effects and 8.0% to spatial trends. For FD, 13.8% was attributable to environmental effects, 15.2% to shared environmental and spatial effects and 5% to spatial trends. For FE, 9.0% was related to environmental variables, 12.7% to shared effects of environmental and spatial variables and 4.5% to spatial variables. For FS, 13.5% was related to environmental effects, 16.9% to shared environmental and spatial effects and 15.4% to spatial trends. 5. Given that functional biodiversity should portray variability in ecosystem functioning, one might expect to find functionally rather differing ecosystems at the opposite ends of major environmental gradients (e.g. acidity, stream size). However, the degree to which variation in the functional biodiversity of stream macroinvertebrates truly portrays variability in ecosystem functioning is difficult to judge because species traits, such as feeding roles and habit traits, are themselves strongly affected by the habitat template. 6. If functional characteristics show strong responses to natural environmental gradients, they also are likely to do so to anthropogenic environmental changes, including changes in habitat structure, organic inputs and acidifying elements. However, given the considerable degree of spatial structure in functional biodiversity, one should not expect that only the local environment and anthropogenic changes therein are responsible for this variability. Rather, the spatial context, as well as natural variability along environmental gradients, should also be explicitly considered in applied research. [source] Investigating Global and Local Categorical Map Configuration Comparisons Based on Coincidence MatricesGEOGRAPHICAL ANALYSIS, Issue 2 2009T. K. Remmel The simple and intuitive nature of the coincidence matrix has not only made it the current "gold standard" for accuracy assessment (based on a sample of map pixels), but also a common tool for describing difference between two categorical maps (when all pixels are enumerated). It is this latter case of map comparison that this article explores. Coincidence matrices, although providing significant information regarding thematic agreement between two categorical maps (composition), can lack significantly in terms of conveying information about differences or similarities in the spatial arrangement (configuration) of those map categories in geographic space. This article introduces means for distilling the available configuration information from a coincidence matrix while demonstrating some simple categorical map comparisons. Specifically, while the coincidence matrix summarizes per-pixel compositional persistence or change, the introduced technique further quantifies the global and local configurational uncertainty between compared maps. I demonstrate how this quantification of configurational uncertainty can be used to gauge which thematic mismatch types are most significant and how to measure/present local configurational uncertainty in a spatial context. Implementation is through a straightforward mathematical algorithm in R that is illustrated by several examples. La sencillez y características las matrices de confusión (tablas de contingencia o de error) no sólo la ha convertido en (1) el estándar por excelencia para la evaluación de confiabilidad (veracidad o validez) de mapas temáticos en escala nominal (en base de una muestra de pixeles en un mapa), sino también en (2) una herramienta común para describir la diferencia entre dichos mapas (cuando todos los pixeles son tomados en cuenta). Este segundo uso de las matrices de confusión es el tema explorado por el presente artículo. A pesar de proporcionar información importante acerca de la confiabilidad temática entre dos mapas de categorías nominales (composición), las matrices de confusión sufren de limitaciones importantes cuando el objetivo es extraer información acerca del patrón o arreglo espacial (configuración) de las categorías del mapa. El presente artículo presenta herramientas para destilar la información de configuración espacial disponible a partir de una matriz de confusión, y al mismo tiempo, ilustra algunas comparaciones entre mapas de categorías nominales. En términos más concretos, la matriz de confusión resume la persistencia o cambio en la composición a nivel de cada pixel. La nueva técnica presentada en este estudio incluye además la cuantificación de la incertidumbre en la configuración de los mapas comparados. El autor demuestra cómo esta cuantificación puede ser utilizada para darse una idea de cuáles tipos de errores temáticos son más importantes, y cómo se puede medir e ilustrar la incertidumbre de la configuración local en el contexto espacial. La implementación del método se realiza a través de un algoritmo matemático sencillo en lenguaje R, el mismo que es ilustrado con varios ejemplos. [source] The Place of Islam in the Geography of Religion: Trends and IntersectionsGEOGRAPHY COMPASS (ELECTRONIC), Issue 5 2007Richard Gale This article reviews recent geographical research on Islam and Muslim identities. In the wake of the events of 11 September 2001, the forms taken by public debate surrounding Muslim communities and societies have been manifold and not always edifying. In the present political climate, where public attitudes to a particular suite of issues are often as misinformed as they are deeply held, the need for academics to furnish insights born out of robust research is acute. While the responses of academics to debates coalescing around Muslim communities and identities have emanated predominantly from religious studies, sociology and anthropology, geographers, with their attention to the spatial components inherent to the articulation of social identities, are making an increasingly significant contribution to our knowledge in this field. This article reviews this contribution, focusing on four areas in which geographical research on Islam has been most pronounced: Muslim residential segregation and ,community cohesion'; the relationship between Islamic dress codes and spatial context in the articulation of Muslim gender identities; the contestation of space that has attended the architectural expression of Muslim identity in urban landscapes and the spatial politics embedded in the construction of Muslim identities at simultaneously national and transnational scales. While the predominant focus is therefore geographical, the article also establishes linkages to other writings on the spatiality of Islam where relevant to the specific themes under discussion. [source] Automobile Reliance Among the Elderly: Race and Spatial Context EffectsGROWTH AND CHANGE, Issue 2 2003Brigitte Waldorf To meet their mobility needs, the elderly assign pivotal importance to the automobile despite the potential challenge of driving cessation and searching for alternatives to automobile transportation. Older persons' generally strong reliance on the automobile varies, however, by land use patterns (density) as well as by demographic and socioeconomic characteristics. This paper analyzes the effects of spatial context and personal attributes on automobile reliance among the elderly. Using the 1995 Nationwide Personal Transportation Survey (NPTS) trip data, two models of automobile reliance among elderly (65+) trip makers are estimated. The results show that spatial context effects of automobile reliance vary by demographic characteristics; in particular, they are more pronounced for black than for white elderly. Moreover, race variation in automobile reliance is strongest in urban locations rather than less dense spatial contexts. Finally, the differentiation between being a passenger rather than a driver is salient in order to understand locational and racial variations in automobile reliance among the elderly. [source] Does the cingulate cortex contribute to spatial conditional associative learning in the rat?HIPPOCAMPUS, Issue 7 2009Marie St-Laurent Abstract Rats with lesions to the anterior or posterior (retrosplenial) region of the cingulate cortex and rats with lesions that included both the anterior and posterior cingulate cortex were tested on a visual,spatial conditional task in which they had to learn to approach one of the two objects depending on the spatial context within which they were embedded. Lesions restricted to either the anterior or the retrosplenial cingulate region did not impair learning of this task which is known to be very sensitive to the effects of hippocampal lesions. Complete lesions of the cingulate cortex gave rise to only a minor retardation in learning. In contrast, lesions to the retrosplenial cortex impaired performance on a spatial navigation task and the classic radial maze. These results suggest that the retrosplenial portion of the cingulate region forms part of a hippocampal circuit underlying learning about spatial responses. The dissociation between the effects of lesions of the cingulate region on different classes of behavior known to be associated with hippocampal function suggests that, although this neural structure does play a role in an extended hippocampal circuit underlying spatial learning, its role in such learning may be a selective one. © 2009 Wiley-Liss, Inc. [source] Institutional Diversity and Capitalist Transition: The Political Economy of Agrarian Change in Arunachal Pradesh, IndiaJOURNAL OF AGRARIAN CHANGE, Issue 4 2009BARBARA HARRISS-WHITE This paper contributes a preliminary analysis of the process of agrarian capitalist transition in Arunachal Pradesh, one of the least studied regions of India. Primarily based on information collected through a field survey in eleven villages, the paper seeks to explain the nature and implications of institutional unevenness in the development of capitalism. Institutional diversity is not simply mapped across space, it is also manifested in the simultaneous existence of market and non-market institutions across the means of production within the same village or spatial context. In addition, there is a continuous and complex interaction among these institutions which both shapes and is shaped by this capitalist transition. Primitive accumulation emerges as a continuing characteristic of the on-going agrarian and non-agrarian capitalist transition. Institutional adaptation, continuity and hybridity are as integral to the emergence of the market economy as are the processes of creation of new institutions and demise of others. There is no necessary correspondence between the emerging commercialization of the different productive dimensions of the agrarian economy. These uneven processes are deeply influenced by existing and emerging power relations and by the state. Framed by the Bernstein,Byres debate about the contemporary (ir)relevance of the agrarian question, evidence is presented to justify the conclusion that although the processes at work are far from the classical models of the transition to capitalism, all aspects of the agrarian question remain relevant. [source] Making better biogeographical predictions of species' distributionsJOURNAL OF APPLIED ECOLOGY, Issue 3 2006ANTOINE GUISAN Summary 1Biogeographical models of species' distributions are essential tools for assessing impacts of changing environmental conditions on natural communities and ecosystems. Practitioners need more reliable predictions to integrate into conservation planning (e.g. reserve design and management). 2Most models still largely ignore or inappropriately take into account important features of species' distributions, such as spatial autocorrelation, dispersal and migration, biotic and environmental interactions. Whether distributions of natural communities or ecosystems are better modelled by assembling individual species' predictions in a bottom-up approach or modelled as collective entities is another important issue. An international workshop was organized to address these issues. 3We discuss more specifically six issues in a methodological framework for generalized regression: (i) links with ecological theory; (ii) optimal use of existing data and artificially generated data; (iii) incorporating spatial context; (iv) integrating ecological and environmental interactions; (v) assessing prediction errors and uncertainties; and (vi) predicting distributions of communities or collective properties of biodiversity. 4Synthesis and applications. Better predictions of the effects of impacts on biological communities and ecosystems can emerge only from more robust species' distribution models and better documentation of the uncertainty associated with these models. An improved understanding of causes of species' distributions, especially at their range limits, as well as of ecological assembly rules and ecosystem functioning, is necessary if further progress is to be made. A better collaborative effort between theoretical and functional ecologists, ecological modellers and statisticians is required to reach these goals. [source] Error modeling and calibration of exteroceptive sensors for accurate mapping applicationsJOURNAL OF FIELD ROBOTICS (FORMERLY JOURNAL OF ROBOTIC SYSTEMS), Issue 1 2010James P. Underwood Reliable robotic perception and planning are critical to performing autonomous actions in uncertain, unstructured environments. In field robotic systems, automation is achieved by interpreting exteroceptive sensor information to infer something about the world. This is then mapped to provide a consistent spatial context, so that actions can be planned around the predicted future interaction of the robot and the world. The whole system is as reliable as the weakest link in this chain. In this paper, the term mapping is used broadly to describe the transformation of range-based exteroceptive sensor data (such as LIDAR or stereo vision) to a fixed navigation frame, so that it can be used to form an internal representation of the environment. The coordinate transformation from the sensor frame to the navigation frame is analyzed to produce a spatial error model that captures the dominant geometric and temporal sources of mapping error. This allows the mapping accuracy to be calculated at run time. A generic extrinsic calibration method for exteroceptive range-based sensors is then presented to determine the sensor location and orientation. This allows systematic errors in individual sensors to be minimized, and when multiple sensors are used, it minimizes the systematic contradiction between them to enable reliable multisensor data fusion. The mathematical derivations at the core of this model are not particularly novel or complicated, but the rigorous analysis and application to field robotics seems to be largely absent from the literature to date. The techniques in this paper are simple to implement, and they offer a significant improvement to the accuracy, precision, and integrity of mapped information. Consequently, they should be employed whenever maps are formed from range-based exteroceptive sensor data. © 2009 Wiley Periodicals, Inc. [source] Post-fire tree establishment patterns at the alpine treeline ecotone: Mount Rainier National Park, Washington, USAJOURNAL OF VEGETATION SCIENCE, Issue 1 2009Kirk M. Stueve Abstract Questions: Does tree establishment: (1) occur at a treeline depressed by fire, (2) cause the forest line to ascend upslope, and/or (3) alter landscape heterogeneity? (4) What abiotic and biotic local site conditions are most important in structuring establishment patterns? (5) Does the abiotic setting become more important with increasing upslope distance from the forest line? Location: Western slopes of Mount Rainier, USA. Methods: We performed classification analysis of 1970 satellite imagery and 2003 aerial photography to delineate establishment. Local site conditions were calculated from a LIDAR-based DEM, ancillary climate data, and 1970 tree locations in a GIS. We used logistic regression on a spatially weighted landscape matrix to rank variables. Results: Considerable establishment after 1970 caused forest line elevation to increase over 150 m in specific locations. Landscape heterogeneity increased with distance from the 1970 forest line. At a broad spatial context, we found establishment was most common near existing trees (0-50 m) and at low elevations (1250-1350 m). Slope aspect (W, NW, N, NE, and E), slope angle (40-60°), and other abiotic factors emerged as important predictors of establishment with increasing upslope distance from the forest line to restricted spatial extents. Conclusions: Favorable climatic conditions likely triggered widespread tree establishment. Readily available seed probably enhanced establishment rates near sexually mature trees, particularly in the less stressful environment at low elevations. The mass effect of nearly ubiquitous establishment in these areas may have obscured the importance of the abiotic setting to restricted spatial extents. Topographic variability apparently produced favorable sites that facilitated opportunistic establishment with increasing upslope distance from the forest line, thereby enabling additional trees to invade the alpine tundra. [source] Landscape context and microenvironment influences on liana communities within treefall gapsJOURNAL OF VEGETATION SCIENCE, Issue 5 2008Agustina Malizia Abstract Questions: How do gap aspect, openness, age and gap density in the surroundings affect diversity and composition of lianas within treefall gaps? Are the variation patterns in liana communities within treefall gaps associated with their climbing mechanisms? Location: Subtropical montane forests in northwestern Argentina. Methods: We used ordination analyses (NMDS) and multiple regressions to describe liana communities (species and climbing groups, stems , 1 cm) in 35 gaps located in a 6-ha plot and to assess relationships with aspect, canopy and subcanopy openness, age and density of recent (three to eight years old) and old (> 8 years old) gaps. Results: Treefall gaps segregated in the ordination diagrams based on their liana species and climbing mechanisms composition: gaps surrounded by a higher density of recent gaps showed higher densities of lianas species using tendrils, spines/hooks and voluble stems. Liana density and richness (independent of stem density) were also positively associated with the density of recent gaps in the surroundings, and negatively associated to gap age. The number of liana species corrected per area was negatively associated to gap aspect and subcanopy openness, and absolute number of liana species was positively associated to gap canopy openness. Conclusions: This study integrates the analysis of different factors influencing liana communities within treefall gaps, and shows that spatial context of gap density (a variable largely neglected in previous studies) is particularly important on lianas composition and diversity, probably by increasing propagule input and the availability of small trellises for support. [source] Spatially contingent interactions between an exotic and native plant mediated through flower visitorsOIKOS, Issue 1 2009Daniel P. Cariveau Exotic plants can negatively impact the fitness of native plants by changing the behavior of flower visitors and thus affecting pollen transfer. The presence of an exotic plant may decrease the visitation rate to native plants and thus increase pollen limitation. Flower visitors may also switch between exotic and native plants and if pollen from an exotic plant is transferred to native plant stigmas this may impede siring by conspecific pollen. As flower visitors forage within a spatial context, the distribution of plants may affect the type and magnitude of pollinator-mediated competition. In this study we examined two questions: 1) does the exotic plant, Carduus nutans (Asteraceae) interact with the native Monarda fistulosa (Lamiaceae) through flower visitors by changing visitation rate and/or through heterospecific pollen transfer, and does this affect seed set of the native plant? 2) Does spatial context affect how the native and exotic plants interact through flower visitors? We created plots containing potted M. fistulosa with and without the presence of potted C. nutans. In the presence of C. nutans, M. fistulosa stigmas had significantly fewer conspecific and more C. nutans pollen grains. Visitation rate and seed set tended to be lower in these invaded plots, however they were not significant. In a second experiment, we examined whether changes in visitation rate to M. fistulosa due to the presence of C. nutans was a function of M. fistulosa distance from C. nutans. We found that visitation rate did not decrease in the presence of C. nutans when M. fistulosa were adjacent to C. nutans or 15 meters from C. nutans. However, floral visitation rate to M. fistulosa decreased at 1 and 5 meters from C. nutans. Our results suggest interactions between plant species through flower visitors may depend on spatial scale. [source] Knowledge, networks of cities and growth in regional urban systems*PAPERS IN REGIONAL SCIENCE, Issue 4 2007Rafael Boix Knowledge city; networks of cities; urban growth; external economies; spatial econometrics Abstract., Recent theories of regional growth and local development emphasise the roles of agglomeration and knowledge as the main determinants of growth, whereas the theories of the networks of cities remark that growth is a process not only within cities but also between cities. The objective of this paper is to measure the factors that affect the evolution of different intensities of knowledge in a region's cities. An adaptation of the OECD knowledge classification is used to divide the industries by knowledge intensity and to model the determinants of these intensities in a spatial context. Results suggest that higher growth rates are associated with higher levels of technology and knowledge. The growth of the different kinds of knowledge is related to local and spatial factors (agglomeration and network externalities) and each knowledge intensity show a particular response to these factors. [source] A method to assess longitudinal riverine connectivity in tropical streams dominated by migratory biota,AQUATIC CONSERVATION: MARINE AND FRESHWATER ECOSYSTEMS, Issue 6 2009Kelly E. Crook Abstract 1.One way in which dams affect ecosystem function is by altering the distribution and abundance of aquatic species. 2.Previous studies indicate that migratory shrimps have significant effects on ecosystem processes in Puerto Rican streams, but are vulnerable to impediments to upstream or downstream passage, such as dams and associated water intakes where stream water is withdrawn for human water supplies. Ecological effects of dams and water withdrawals from streams depend on spatial context and temporal variability of flow in relation to the amount of water withdrawn. 3.This paper presents a conceptual model for estimating the probability that an individual shrimp is able to migrate from a stream's headwaters to the estuary as a larva, and then return to the headwaters as a juvenile, given a set of dams and water withdrawals in the stream network. The model is applied to flow and withdrawal data for a set of dams and water withdrawals in the Caribbean National Forest (CNF) in Puerto Rico. 4.The index of longitudinal riverine connectivity (ILRC), is used to classify 17 water intakes in streams draining the CNF as having low, moderate, or high connectivity in terms of shrimp migration in both directions. An in-depth comparison of two streams showed that the stream characterized by higher water withdrawal had low connectivity, even during wet periods. Severity of effects is illustrated by a drought year, where the most downstream intake caused 100% larval shrimp mortality 78% of the year. 5.The ranking system provided by the index can be used as a tool for conservation ecologists and water resource managers to evaluate the relative vulnerability of migratory biota in streams, across different scales (reach-network), to seasonally low flows and extended drought. This information can be used to help evaluate the environmental tradeoffs of future water withdrawals. Copyright © 2009 John Wiley & Sons, Ltd. [source] New Polynesian Triangle: Rethinking Polynesian migration and development in the PacificASIA PACIFIC VIEWPOINT, Issue 3 2009Manuhuia Barcham Abstract For many Polynesians migration is still framed within a particular spatial context, although on an enlarged scale , one that we have termed the New Polynesian Triangle. With its apexes in the North American continent to the east, Australia in the west and New Zealand in the south, this New Polynesian Triangle encompasses a particular field through which ongoing Polynesian migration and movement continues to occur. Movement within this New Polynesian Triangle is both multidimensional and multidirectional. While it is the movement of economic resources, particularly remittances, that has captured the interest of many agencies operating in the region, we argue that such economic flows are integrally linked with other flows , of goods, ideas, skills and culture , to form a single dynamic system of movement. Importantly, such flows are not uni-directional (from ,rich' to ,poor' countries) as was assumed in times past. In developing ideas on the New Polynesian Triangle, we wish to move away from the dominant Western discourse of the Pacific Ocean as a barrier to development and movement and towards the reclamation of the ocean as a conduit and source of connection and movement for Pacific peoples. [source] Automobile Reliance Among the Elderly: Race and Spatial Context EffectsGROWTH AND CHANGE, Issue 2 2003Brigitte Waldorf To meet their mobility needs, the elderly assign pivotal importance to the automobile despite the potential challenge of driving cessation and searching for alternatives to automobile transportation. Older persons' generally strong reliance on the automobile varies, however, by land use patterns (density) as well as by demographic and socioeconomic characteristics. This paper analyzes the effects of spatial context and personal attributes on automobile reliance among the elderly. Using the 1995 Nationwide Personal Transportation Survey (NPTS) trip data, two models of automobile reliance among elderly (65+) trip makers are estimated. The results show that spatial context effects of automobile reliance vary by demographic characteristics; in particular, they are more pronounced for black than for white elderly. Moreover, race variation in automobile reliance is strongest in urban locations rather than less dense spatial contexts. Finally, the differentiation between being a passenger rather than a driver is salient in order to understand locational and racial variations in automobile reliance among the elderly. [source] Context-dependency of a complex fruit,frugivore mutualism: temporal variation in crop size and neighborhood effectsOIKOS, Issue 3 2010Soumya Prasad The quantity of fruit consumed by dispersers is highly variable among individuals within plant populations. The outcome of such selection operated by frugivores has been examined mostly with respect to changing spatial contexts. The influence of varying temporal contexts on frugivore choice, and their possible demographic and evolutionary consequences is poorly understood. We examined if temporal variation in fruit availability across a hierarchy of nested temporal levels (interannual, intraseasonal, 120 h, 24 h) altered frugivore choice for a complex seed dispersal system in dry tropical forests of southern India. The interactions between Phyllanthus emblica and its primary disperser (ruminants) was mediated by another frugivore (a primate), which made large quantities of fruit available on the ground to ruminants. The direction and strength of crop size and neighborhood effects on this interaction varied with changing temporal contexts. Fruit availability was higher in the first of the two study years, and at the start of the season in both years. Fruit persistence on trees, determined by primate foraging, was influenced by crop size and conspecific neighborhood densities only in the high fruit availability year. Fruit removal by ruminants was influenced by crop size in both years and neighborhood densities only in the high availability year. In both years, these effects were stronger at the start of the season. Intraseasonal reduction in fruit availability diminished inequalities in fruit removal by ruminants and the influence of crop size and fruiting neighborhoods. All trees were not equally attractive to frugivores in a P. emblica population at all points of time. Temporal asymmetry in frugivore-mediated selection could reduce potential for co-evolution between frugivores and plants by diluting selective pressures. Inter-dependencies formed between disparate animal consumers can add additional levels of complexity to plant,frugivore mutualistic networks and have potential reproductive consequences for specific individuals within populations. [source] | |||||||||||||||||||||||||