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Spatial Attributes (spatial + attribute)

Distribution by Scientific Domains

Humanities and Social Sciences	33%

Selected Abstracts

Geostatistical Prediction and Simulation of Point Values from Areal Data

GEOGRAPHICAL ANALYSIS, Issue 2 2005
Phaedon C. Kyriakidis
The spatial prediction and simulation of point values from areal data are addressed within the general geostatistical framework of change of support (the term support referring to the domain informed by each measurement or unknown value). It is shown that the geostatistical framework (i) can explicitly and consistently account for the support differences between the available areal data and the sought-after point predictions, (ii) yields coherent (mass-preserving or pycnophylactic) predictions, and (iii) provides a measure of reliability (standard error) associated with each prediction. In the case of stochastic simulation, alternative point-support simulated realizations of a spatial attribute reproduce (i) a point-support histogram (Gaussian in this work), (ii) a point-support semivariogram model (possibly including anisotropic nested structures), and (iii) when upscaled, the available areal data. Such point-support-simulated realizations can be used in a Monte Carlo framework to assess the uncertainty in spatially distributed model outputs operating at a fine spatial resolution because of uncertain input parameters inferred from coarser spatial resolution data. Alternatively, such simulated realizations can be used in a model-based hypothesis-testing context to approximate the sampling distribution of, say, the correlation coefficient between two spatial data sets, when one is available at a point support and the other at an areal support. A case study using synthetic data illustrates the application of the proposed methodology in a remote sensing context, whereby areal data are available on a regular pixel support. It is demonstrated that point-support (sub-pixel scale) predictions and simulated realizations can be readily obtained, and that such predictions and realizations are consistent with the available information at the coarser (pixel-level) spatial resolution. [source]

Modelling plumes of overland flow from logging tracks

HYDROLOGICAL PROCESSES, Issue 12 2002
P. B. Hairsine
Abstract Most land-based forestry systems use extensive networks of unsealed tracks to access the timber resource. These tracks are normally drained by constructing cross-banks, or water bars, across the tracks immediately following logging. Cross-banks serve three functions in controlling sediment movement within forestry compartments: 1.they define the specific catchment area of the snig track (also known as skid trails) so that the overland flow does not develop sufficient energy to cause gullies, and sheet and rill erosion is reduced; 2.they induce some sediment deposition as flow velocity reduces at the cross-bank; 3.they redirect overland flow into the adjacent general harvesting area (GHA) so that further sediment deposition may take place. This paper describes a simple model that predicts the third of these functions in which the rate of runoff from the track is combined with spatial attributes of the track and stream network. Predictions of the extent of the overland flow plumes and the volume of water delivered to streams is probabilistically presented for a range of rainfall-event scenarios with rainfall intensity, time since logging and compartment layout as model inputs. Generic equations guiding the trade-off between intercross-bank length and flow path distance from cross-bank outlet to the stream network needed for infiltration of track runoff are derived. Copyright © 2002 John Wiley & Sons, Ltd. Copyright © 2002 John Wiley & Sons, Ltd. [source]

Suicide and Alcohol: Do Outlets Play a Role?

ALCOHOLISM, Issue 12 2009
Fred W. Johnson
Background:, The purpose of this study was to determine whether the number of alcohol outlets in local and adjacent areas, in particular bars, was related over time to completed suicide and suicide attempts. There is evidence both from studies of individuals and time series aggregate studies, mostly at the national level, of substantial alcohol involvement in suicide, but no small-area, longitudinal studies have been carried out. The present study is the first that is both longitudinal and based on a large number of small spatial units, California zip codes, a level of resolution permitting analysis of the relationship between local alcohol access and suicide rates over time. Method:, Longitudinal data were obtained from 581 consistently defined zip code areas over 6 years (1995,2000) using data from the California Index Locations Database, a geographic information system that contains both population and place information with spatial attributes for the entire state. Measures obtained from each zip code included population characteristics (e.g., median age) and place characteristics (e.g., numbers of retail and alcohol outlets) which were related in separate analyses to (i) suicide mortality and (ii) the number of hospitalizations for injuries caused by suicide attempts. The effect of place characteristics in zip code areas adjacent to each of the 581 local zip codes (spatial lags) was also assessed. Analysis methods were random effects models corrected for spatial autocorrelation. Results:, Completed suicide rates were higher in zip code areas with greater local and lagged bar densities; and higher in areas with greater local but not lagged off-premise outlet densities. Whereas completed suicide rates were lower among blacks and Hispanics, completed suicide rates were higher among low income, older whites living in less densely populated areas, that is, rural areas. Rates of suicide attempts were higher in zip code areas with greater local but not lagged bar densities, and higher among low income younger whites living in smaller households and in rural areas. Rates of attempted suicide were also higher among blacks. Completed suicide and suicide attempt rates were lower in zip code areas with greater local restaurant densities; there were no lagged effects for restaurants. Conclusions:, Bar densities in particular appear related to suicide, meaning, because this is an aggregate-level spatial analysis, that suicides, both attempted and completed, occur at greater rates in rural community areas with greater bar densities. Because the suicide rate is highest in rural areas, this study suggests that although the number of completed and attempted suicides is no doubt greater in absolute numbers in urban areas, the suicide rate, both completed and attempted, is greater in rural areas, which draws attention, perhaps much needed, to the problems of rural America. [source]

Spatial variation in mink and muskrat interactions in Canada

OIKOS, Issue 3 2001
John Erb
We investigated the spatial attributes of mink (Mustela vison) and muskrat (Ondatra zibethicus) interactions in Canada using 160 geographically paired historic time series of mink (n=80) and muskrat (n=80) harvest data obtained from Hudson's Bay Co. Archives. All series were 25 years in length (1925,1949) and were distributed primarily throughout five ecozones. We used autoregressive models and cross-correlation analysis to characterize the interactions between mink and muskrat. Model selection results did not differ among ecozones, and indicated that a predator-prey autoregressive model incorporating a delayed density-dependent term best described both the mink and muskrat harvest time series. Subsequent analysis of autoregressive coefficients and estimated lags indicated that mink and muskrat interactions vary throughout Canada. In western Canada, the trophic interactions appear to be strong, and mink population cycles lag behind muskrats 2,3 years. In central Canada, mink harvests lagged behind muskrats 1 year, and mink and muskrat interactions in central Canada, with the exception of the Hudson Plains ecozone, were intermediate. In eastern Canada, the trophic interactions appeared weakest, and there were no distinct time lags between mink and muskrat. Stronger interactions in western Canada may be a result of decreased prey diversity, forcing mink to specialize more on muskrats, whereas comparatively stronger perturbations stemming from other trophic interactions may alter the estimated interaction between mink and muskrat in eastern Canada. [source]

Impact of landscape spatial pattern on liana communities in tropical rainforests at Los Tuxtlas, Mexico

APPLIED VEGETATION SCIENCE, Issue 3 2009
Víctor Arroyo-Rodríguez
Abstract Questions: What are the species composition and species and stem densities of liana communities in tropical landscapes of different deforestation levels? Which spatial attributes (forest cover, patch area, shape and isolation) have the strongest influence on liana communities in these landscapes? Location: Forty-five rainforest patches in Los Tuxtlas Biosphere Reserve, Mexico. Methods: In three landscapes with different deforestation levels (HDL=4%; IDL=11%; and LDL=24% of remaining forest cover) liana communities (DBH ,2.5 cm) were characterized in 15 randomly selected patches per landscape (10 50 m × 2 m transects per patch=0.1 ha), and evaluated the effects of patch area, shape and isolation on liana species and stem density (number of species and stems per 0.1 ha). Results: A total of 64 taxa and 24 families were sampled. Species composition differed highly among landscapes, with HDL being the most dissimilar landscape. The response of lianas to landscape spatial pattern differed significantly among landscapes. Proximity to villages had a strong positive effect on species and stem densities in LDL and IDL. There was a sharp decrease in liana stem density in HDL, with four patches (27%) found to be unoccupied by lianas. Conclusions: Fragmentation may have a positive effect on lianas, partly because of edge effects. This positive effect seems to be limited by the proportion of remaining forest cover in the landscape, as the liana communities had collapsed in the most deforested landscape. [source]

Using Space: Agency and Identity in a Public,Housing Development

CITY & COMMUNITY, Issue 3 2002
Kevin Fox Gotham
Recent critiques of conventional poverty research have highlighted the need to move beyond the conceptual limitations of "neighborhood effects" models and the use of the tropes of "adaptation" or "resistance" to explain the behaviors and actions of the urban poor. We use ethnographic field observations and interviews with public,housing residents to address these limitations in the poverty literature, assess competing explanations of poor people's agency, and provide insight into the importance of space as a mediating link between macrostructural constraints and locally situated behaviors. We theorize agency and identity as spatial phenomena,with spatial attributes and spatial influences,and examine how different spatial meanings and locations enable or constrain particular forms of social action and behavior. Our ethnographic and interview data depict several strategies by which residents "use space" to provide a measure of security and protection, to designate and avoid areas of criminality and drug activity, and to challenge or support the redevelopment of public housing. From these data we show that urban space is not a residual phenomenon in which social action occurs, but a constitutive dimension of social life that shapes life experiences, social conflict, and action. [source]