Search results for "Spatial Distribution"

Inverse problem for tripotential measures in the study of buried cavities

1996

This paper presents a solution to the inverse electrical problem for the interpretation of apparent resistivity anomalies due to empty buried cavities of quasi-spherical shape when tripotential measures are carried out. The anomalies of the apparent resistivities ra,rb andrg,and the composed resistivitiesrmand rt were previously calculated for a sufficient class of spherical models of resistivity anomalies. Then, for the whole class of models, some functionals of spatial distribution of the apparent and composed resistivity were identified and analyzed. They represent the average characteristics of the anomalies and, depending in a simple way on the fundamental parameters of the sources of …

Actividad y territorio : la localización de la población extranjera en Barcelona

2005

Este texto analiza el papel selectivo del territorio en el asentamiento de la población de nacionalidad extranjera y, en especial, de la función de la ciudad de Barcelona como lugar de atracción, filtro y selección de esta población en el contexto de Cataluña. Con este objetivo, en primer lugar se describen las pautas de distribución espacial de la población extranjera en Cataluña, para posteriormente comparar las características sociodemográficas de la población de nacionalidad extranjera censada en Barcelona y la censada en el resto de Cataluña en 2001, teniendo en cuenta como principales variables la estructura por sexo, edad y nacionalidad, el nivel de instrucción y la relación con la a…

Spatial distribution and aggregation ofXenobalanus globicipitison the flukes of striped dolphins,Stenella coeruleoalba: An indicator of host hydrodyn…

2020

Spatial Distribution of Ethylene Production by Individual Needles Along a Shoot ofPinus sylvestrisL.: Relationship with Peroxidase Activity

1998

Spatial distribution of ethylene production by individual current year needles and the relationship with peroxidase activity was studied along a shoot of Scots pine (Pinus sylvestrisL.). Much variation in ethylene production between and within individual seedlings was found. There was a significant difference in mean intensity of ethylene production between orthostichies within individual seedlings. The capacity of individual needles to convert 1-aminocyclopropane-1-carboxylic acid (ACC) to ethylene did not correlate with the basal rate of ethylene production. Mean ethylene production intensity by orthostichies correlated positively with mean peroxidase activity. A positive correlation betw…

Storage and release of fossil organic carbon related to weathering of sedimentary rocks

2007

International audience; The biogeochemical carbon cycle, which plays an undeniable role in global climate change, is defined both by the size of carbon reservoirs (such as the atmosphere, biomass, soil and bedrock) and the exchange between them of various mineral and organic carbon forms. Among these carbon forms, fossil organic carbon (FOC) (i.e., the ancient organic matter stored in sedimentary rocks) is widely observed in modern environments but is not included in the supergene carbon budget. Using a digitized map of the world and an existing model of CO2 consumption associated with rock weathering, we establish the global distribution of FOC stored in the first meter of sedimentary rock…

Spatial distribution of N-cycling microbial communities showed complex patterns in constructed wetland sediments.

2013

International audience; Constructed wetlands are used for biological treatment of wastewater from agricultural lands carrying pollutants such as nitrates. Nitrogen removal in wetlands occurs from direct assimilation by plants and through microbial nitrification and denitrification. We investigated the spatial distribution of N-cycling microbial communities and genes involved in nitrification and denitrification in constructed wetland sediments receiving irrigation water. We used quantitative real-time PCR (qPCR) to characterize microbial communities. Geostatistical variance analysis was used to relate them with vegetation cover and biogeochemical sediment properties. The spatial distributio…

Phytoplankton distribution along trophic gradients within and among reservoirs in Catalonia (Spain)

2008

SUMMARY 1. Longitudinal gradients in the epilimnetic waters of stratified reservoirs provide a useful database to study changing environmental conditions. The spatial distribution, assemblage structure and specific adaptations of phytoplankton assemblages can be analysed along these gradients over short time scales. 2. Four reservoirs with a similar typology, located along an altitudinal gradient in the same eco-region, were sampled along their longitudinal axes. In total, 19 sampling stations provided a trophic spectrum, ranging from oligo-mesotrophy to hypertrophy, which was quantified by calculating the trophic state index of each sampling station in the four reservoirs. 3. Several patte…

Spatial patterns of bacterial taxa in nature reflect ecological traits of deep branches of the 16S rRNA bacterial tree

2009

International audience; Whether bacteria display spatial patterns of distribution and at which level of taxonomic organization such patterns can be observed are central questions in microbial ecology. Here we investigated how the total and relative abundances of eight bacterial taxa at the phylum or class level were spatially distributed in a pasture by using quantitative PCR and geostatistical modelling. The distributions of the relative abundance of most taxa varied by a factor of 2.5–6.5 and displayed strong spatial patterns at the field scale. These spatial patterns were taxon-specific and correlated to soil properties, which indicates that members of a bacterial clade defined at high t…

Barrier effects on the spatial distribution of Xylella fastidiosa in Alicante, Spain

2021

AbstractSpatial models often assume isotropy and stationarity, implying that spatial dependence is direction invariant and uniform throughout the study area. However, these assumptions are violated when dispersal barriers are present in the form of geographical features or disease control interventions. Despite this, the issue of non-stationarity has been little explored in the context of plant health. The objective of this study was to evaluate the influence of different barriers in the distribution of the quarantine plant pathogenic bacterium Xylella fastidiosa in the demarcated area in Alicante, Spain. Occurrence data from the official surveys in 2018 were analyzed with four spatial Baye…

Spatial Gradients of Intensity and Persistence of Soil Water Repellency Under Different Forest Types in Central Mexico

2016

Organic residues release hydrophobic compounds to the soil that may induce soil water repellency (WR), which may inhibit infiltration and increase runoff and soil loss rates. Although there are many studies on soil WR through the world, very few investigations have been conducted in Mexican areas. This paper studies the natural background of soil WR in soils from central Mexico under representative forest types, analyzing the spatial distribution of soil WR in relation with tree canopy, vegetation cover and main soil chemical (pH, CaCO3, organic C content and exchangeable cations) and physical properties (texture). The water drop penetration time and the ethanol tests were used to assess pe…