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21.
An ecological classification of rocky shores at a regional scale: a predictive tool for management of conservation values 
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下载免费PDF全文 The ecological classification of coastal waters has become an important issue in ecosystem water quality assessment. Previous studies have suggested that abiotic variables seem to be a suitable alternative to biological data for classifying coastal areas at different scales. The study presented here proposes a downscaling methodology for the classification of coastal waters at a regional scale within the NE Atlantic based on standardized data and objective decision rules. Physical variables (temperature, wave exposure, tidal range and radiation) were selected because of their ecological role, availability and statistical decision rules. This information was based on satellite data and mathematical modelling of natural coastal processes. The N and NW Spanish coastline was subdivided into 41 20‐km segments that were classified according to physical variables using the self‐organizing map and k‐means algorithms. To validate the classification with biological data, 21 sites representing the entire range of physical typologies in the study area were simultaneously and consistently sampled. Intertidal macroalgae were identified in each of 10 quadrats of 50 × 50 cm for two to three transects per site, according to a stratified sampling procedure. The coverage of macroalgae was obtained by photographic analysis. The physical classification shows four typologies: Lower Rias, Upper Rias, West Cantabric and East Cantabric. Statistical analyses confirmed the ecological significance of these typologies at the tidal levels where seaweeds were the major structural element (lower and middle intertidal). According to the biological data, the greatest differences were found between the Upper Rias and the rest of the N and NW Iberian Peninsula coast. Thus, the classification methodology has potential application as a management tool. 相似文献
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Disjunctive kriging, universal kriging, or no kriging: Small sample results with simulated fields 总被引：3，自引：0，他引：3
This paper provides a comparison between linear (universal) and nonlinear (disjunctive) kriging estimators when they are computed from small samples chosen randomly on simulated stationary and nonstationary fields. Point estimation results are reported. In all cases considered, kriging estimators were found better than a local mean estimator, with universal kriging either better than or as good as disjunctive kriging. The latter, which is suited to handle stationary fields, did not provide more accurate estimates because the use of small samples led to inconsistencies in the assumed bivariate model. Universal kriging was particularly better with nonstationary fields. 相似文献
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Andrea Cortis Carlos E. Puente Bellie Sivakumar 《Stochastic Environmental Research and Risk Assessment (SERRA)》2009,23(7):897-906
We present the extension of a deterministic fractal geometric procedure aimed at representing the complexity of patterns encountered
in environmental applications. The procedure, which is based on transformations of multifractal distributions via fractal
functions, is extended through the introduction of nonlinear perturbations in the generating iterated linear maps. We demonstrate,
by means of various simulations based on changes in parameters, that the nonlinear perturbations generate yet a richer collection
of interesting patterns, as reflected by their overall shapes and their statistical and multifractal properties. It is shown
that the nonlinear extensions yield structures that closely resemble complex hydrologic spatio-temporal datasets, such as
rainfall and runoff time series, and width-functions of river networks. The implications of this nonlinear approach for environmental
modeling and prediction are discussed. 相似文献
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Escudero Christian R. Ramirez Gaytan Alejandro Zamora Camacho Araceli Preciado Adolfo Flores Karen L. Gomez Hernandez Adan 《Natural Hazards》2022,110(1):247-267
Natural Hazards - We performed a seismic vulnerability assessment that involves geotechnical and building structure analysis for Puerto Vallarta, Mexico, a city located along the pacific coast.... 相似文献
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Jean Kormann Juan E. Rodríguez Miguel Ferrer Albert Farrés Natalia Gutiérrez Josep de la Puente Mauricio Hanzich José M. Cela 《Computational Geosciences》2017,21(1):31-45
Full waveform inversion (FWI) is one of the most challenging procedures to obtain quantitative information of the subsurface. For elastic inversions, when both compressional and shear velocities have to be inverted, the algorithmic issue becomes also a computational challenge due to the high cost related to modelling elastic rather than acoustic waves. This shortcoming has been moderately mitigated by using high-performance computing to accelerate 3D elastic FWI kernels. Nevertheless, there is room in the FWI workflows for obtaining large speedups at the cost of proper grid pre-processing and data decimation techniques. In the present work, we show how by making full use of frequency-adapted grids, composite shot lists and a novel dynamic offset control strategy, we can reduce by several orders of magnitude the compute time while improving the convergence of the method in the studied cases, regardless of the forward and adjoint compute kernels used. 相似文献
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Spatial variation of biological and pedological properties in an area affected by a metallurgical mercury plant: Almadenejos (Spain) 总被引：1，自引：0，他引：1
Rocio Millan Thomas SchmidMaria José Sierra Sandra Carrasco-GilMaite Villadóniga Celia RicoDolores María Sánchez Ledesma Francisco Javier Díaz Puente 《Applied Geochemistry》2011,26(2):174-181
Almadén, Spain, has the most important known cinnabar deposits, which have provided a third of the entire world production of Hg, and has been the scene for numerous studies on Hg. This mining district includes several mines where cinnabar has been extracted in the past two millennia as well as facilities related to the production of primary Hg. The aim of the work is to evaluate the spatial distribution of Hg in the soil-plant system within an area where intense activity occurred over a long period. An abandoned metallurgical plant from the 17th-18th centuries was chosen as the study area, situated in Almadenejos a distance of 12 km from Almadén. Nowadays, this plot is covered with cinnabar mine tailings and it is used by village inhabitants for livestock grazing. The area has elevated Hg concentrations of natural origin and from human activities. Soil parameters are similar within the study area; however, data reveal high variability in total and available Hg concentrations in soils, making it difficult to establish a trend. Marrubium vulgare L. has been studied due to its abundance in the plot, and there is no evidence of phenological toxicity. In spite of elevated Hg concentrations, high biological activity is found in the sampled soils. All these characteristics, spatial variation, high Hg concentration, good biological activity, make this a particularly good area for studies involving Hg. 相似文献
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María Recio Bárbara Ondiviela Araceli Puente Cristina Galván Aina G. Gómez Jose A. Juanes 《Estuaries and Coasts》2013,36(5):997-1005
Estuaries are one of the most threatened ecosystems, with a great number of stressors related to pollution, hydromorphological changes, and invasive species. However, the response of the biological indicators proposed for their ecological status assessment is not always well established. When using estuarine vegetation (saltmarshes and seagrasses) as an indicator, there are several theoretical concepts regarding the relationships between the variations of this indicator and hydromorphological stressors. It is precisely these relationships which are presented in this work. To carry out this objective, based on the first intercalibration process, a set of metrics for saltmarsh and seagrass taxonomic compositions (e.g., loss of number of taxa and richness) and abundance (e.g., relative coverage and relative extent) have been selected and applied to different estuaries located in Northern Spain. Additionally, a methodology for the hydromorphological status assessment, based on the analysis of the anthropogenic changes in the hydrodynamic and morphological estuarine characteristics (e.g., the extension of land claim areas or changes in the estuarine perimeter), has been developed and applied to these transitional water bodies in order to find a gradient of pressured sites in which we seek correlations between the vegetation metrics and hydromorphological stressors. As a result, the response of the different vegetation indicators is variable. In some cases, a negative correlation of the indicator with the pressure degree exists, whereas in other cases, the relationship is not as clear. Nonetheless, according to the results, it can be suggested that the placing of anthropogenic structures diminishes the quality of the estuarine vegetation. Therefore, to maintain a suitable environment for the estuarine vegetation seems necessary in order to reduce the number of the hydrodynamic structures which are no longer in use. 相似文献
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The possibility and effectiveness of microencapsulation of okadaic acid (OA) in gelatin-acacia microcapsules has been studied. The encapsulation efficiency was higher than 33%. The microcapsules were shown to be very stable, not leaching more than 9% of the encapsulated OA in a 20-h period. OA from the microcapsules was absorbed by the mussels very efficiently, accumulating--after 3 days of feeding and one of depuration--65% of the OA in microcapsules and 22% of the total OA used at the beginning of the microencapsulation process. These efficiencies and the possibility of encapsulating single DSP toxins and derivatives constitute a valuable tool for the study of the accumulation and biotransformation of DSP toxins in bivalves. 相似文献