Quantifying deforestation and secondary forest determinants for different spatial extents in an Amazonian colonization frontier (Rondonia)     

Luciana de Souza Soler  Maria Isabel S. Escada  Peter H. Verburg 《Applied geography (Sevenoaks, England)》2009,29(2):182-193

Spatial patterns of deforested areas and secondary forest are analyzed in terms of the spatial variation in location factors at different spatial extents. The spatial extents considered are old and new agrarian colonization projects and the administrative units of two different municipalities in Rondonia: Vale do Anari and Machadinho d'Oeste. A grid database was constructed including land cover and potential location factors based on biophysical, accessibility, socioeconomic and policy data. Results of the spatial analyses confirmed the hypothesis that different extents yield different relationships between land use/cover patterns and their location factors, particularly between old and new agrarian colonization projects. It emphasizes that current patterns of forest, secondary forest and pasture/agriculture can only be understood with a combination of policy, accessibility, biophysical and socioeconomic factors while accounting for the historical pathways of change. Because we are dealing with different trajectories of land use/cover change, static analysis of the spatial pattern without acknowledging these trajectories will lead to erroneous interpretations of the current and future land use/cover dynamics.  相似文献   

Internal structure of the aeolian sand dunes of El Fangar spit, Ebro Delta (Tarragona, Spain)     

Inmaculada Rodríguez Santalla  María Jos Snchez García  Isabel Montoya Montes  David Gmez Ortiz  Tomas Martín Crespo  Jordi Serra Raventos 《Geomorphology》2009,104(3-4):238-252

This paper presents an analysis of the dune field dynamics of El Fangar Spit in the Ebro Delta (Spain), associating it with the internal structure of dunes carried out with ground-penetrating radar and supported by data from topographic DGPS. These analyses are of great importance to ascertain the state of the internal structure of dunes as an important element in their stability and, therefore in their evolution. The internal structure shows accretion and progradation sequences of dunes over beach deposits, which depend on dune morphology (height, crest orientation) and location, as well as the processes acting on them.  相似文献   

Effects of mariculture on macrobenthic assemblages in a western mediterranean site   总被引：2，自引：0，他引：2  

Paolo Tomassetti  Emma Persia  Isabel Mercatali  Danilo Vani  Veronica Marussso  Salvatore Porrello 《Marine pollution bulletin》2009,58(4):533-541

The effects of solid organic wastes from a marine fish farm on sediment was tested using macrobenthic fauna as biological indicators. Impact on benthic fauna was evaluated in the vicinity of a fish farm in the Tyrrhenian Sea (Western Mediterranean) between July 2001 and October 2002. Changes in benthic community structure were investigated using multivariate, distributional and univariate analyses (diversity indices, AMBI and M-AMBI). The results showed sharp disturbance of assemblages under the cages and no effects in the area more than 25 m from the cages. Sediment alterations were related to an increase in farmed biomass and its wastes, as well as to low current speed that allowed accumulation of organic matter on the sea floor. It was possible to follow the ecological succession from slightly altered assemblages to heavily polluted ones in the very short period of a single fish fattening cycle (15 months).  相似文献   

Using Qualitative Methods in Medical Geography: Deconstructive Moments in a Subdiscipline?     

Isabel Dyck 《The Professional geographer》1999,51(2):243-253

As medical geography reinvents itself as health geography, the linkages between social theory and the deconstruction of central categories organizing its medical orientation are being explored. This paper discusses the contribution of qualitative research to this process. In providing access to alternative ways of understanding health concerns, and emphasizing issues of power in the production of knowledge, qualitative methodology carries the potential for reconceptualizing key issues framing investigation of the relationships between place, people, and their health. In pursuing current issues in social theory, qualitative research also contributes to the blurring of the subdiscipline's boundaries and revitalizes its agenda.  相似文献   

Evidence of an atmospheric forcing on bacterioplankton and phytoplankton dynamics in a high mountain lake     

Elvira Pulido-Villena  Isabel Reche  Rafael Morales-Baquero 《Aquatic Sciences - Research Across Boundaries》2008,70(1):1-9

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Performance of methods for estimating the time of concentration in a watershed of a tropical region   总被引：1，自引：1，他引：0  

Isabel Kaufmann de Almeida  Aleska Kaufmann Almeida  Sandra Garcia Gabas  Teodorico Alves Sobrinho 《水文科学杂志》2017,62(14):2406-2414

The time of concentration (T_c) is a fundamental parameter in the design of hydrological projects for watersheds. In this study a graphical methodology is described for estimating T_c in a watershed, and this is applied to 17 rainfall–runoff events from a rural watershed located near the capital city of Mato Grosso do Sul State, in the Brazilian Cerrado. The T_c values obtained through the graphical method were compared to T_c values estimated using 20 equations from various references. The equations were selected by considering those that were not developed using data for urban watersheds, and the results of the graphical method were compared to those derived by applying the equations to sub-basin data. The graphical method was reliable in determining T_c, and Ventura’s equation was found to present the best performance for a rural watershed in a tropical climate region.  相似文献   

L-moments for automatic threshold selection in extreme value analysis     

Jessica Silva Lomba  Maria Isabel Fraga Alves 《Stochastic Environmental Research and Risk Assessment (SERRA)》2020,34(3):465-491

In extreme value analysis, sensitivity of inference to the definition of extreme event is a paramount issue. Under the peaks-over-threshold approach, this translates directly into the need of fitting a Generalized Pareto distribution to observations above a suitable level that balances bias versus variance of estimates. Selection methodologies established in the literature face recurrent challenges such as an inherent subjectivity or high computational intensity. We suggest a truly automated method for threshold detection, aiming at time efficiency and elimination of subjective judgment. Based on the well-established theory of L-moments, this versatile data-driven technique can handle batch processing of large collections of extremes data, while also presenting good performance on small samples. The technique’s performance is evaluated in a large simulation study and illustrated with significant wave height data sets from the literature. We find that it compares favorably to other state-of-the-art methods regarding the choice of threshold, associated parameter estimation and the ultimate goal of computationally efficient return level estimation.  相似文献   

Metagenomic Analysis of Bacterial Communities from a Nitrification–Denitrification Treatment of Landfill Leachates     

Ana Isabel Díaz  Paula Oulego  Adriana Laca  Jos Manuel Gonzlez  Mario Díaz 《洁净——土壤、空气、水》2019,47(11)

The efficiency of the biological removal of carbon and nitrogen from leachates is determined by the activity of microbial populations present in biological reactors. In this work, a complete characterization of bacterial communities revealed by personal genome machine sequencing (PGM) has been carried out from different points of a nitrification–denitrification process operated in an urban landfill. The leachate fed to the treatment is a mixture of young leachate, old leachate, and effluent from an anaerobic digestion process, in a volume ratio of 1:0.9:0.12, respectively. The anoxic and oxic reactors are followed by an ultrafiltration step. Samples are taken from different points of the process. Results reveal the microbial diversity of the samples, which include detection of minority populations that are difficult to explore by other methods. Bacteria belonging to Bacteroidetes and Proteobacteria are dominant in all the samples analyzed. Proteobacteria represents more than 50% of the total population in all cases. Samples taken after the biological treatment show a significant reduction in the relative abundance of Firmicutes, Tenericutes, and Lentisphaerae phyla in comparation with the initial leachate. The relative abundance of the classes is also studied and the most abundant in the samples are β‐Proteobacteria and Flavobacteria.  相似文献   

Geophysical investigation of the Colônia structure,Brazil     

Renato L. Prado  Isabel C. Espin Fenoll  Irfan Ullah  Gianna C. Maciel Miura  Alvaro P. Crsta  Roberto P. Zanon dos Santos  Wolf Uwe Reimold  Vagner R. Elis  Erico Imbernon  Claudio Riccomini  Liliana Alcazar Diogo 《Meteoritics & planetary science》2019,54(10):2357-2372

The origin of the nearly circular Colônia structure, located at the southwestern edge of the city of São Paulo, Brazil, has been the subject of a long‐standing debate, ever since the 1960s when the structure was first investigated by geophysical methods. The structure still raises interest for geological research, as its sedimentary infill holds important paleoclimatic information about the evolution of the tropical rainforest, as well as the interplay between the South American summer monsoon, the Intertropical Convergence Zone, and the southern Westerly wind belt—for possibly as long as several million years. In addition, the search for evidence to conclusively establish the origin of this structure continues, and the answer most likely lies in the lower portions of the basin's sedimentary infill, which also holds a significant potential for underground water resources. Here, we present the results from recent seismic (reflection and HVSR), gravimetric, and geoelectrical surveys. They have provided a reliable image of the sedimentary infill, and the maximum depth to basement within the structure has been constrained consistently by the different methods to approximately ?400 m. The geophysical data have also allowed to map the lateral contact between the crystalline basement rocks and the sedimentary infill, which indicates a diameter of approximately 2.8 km for the sedimentary basin, with 3.6 km being the diameter of the outermost limit of the structure. A total of six seismic stratigraphic boundaries were identified within the sedimentary infill, providing a framework for the planning of a deep drilling campaign and subsequent sampling program aimed at geological and paleoclimatology studies.  相似文献   

Effects of Paracentrotus lividus (Lamark, 1816) harvesting on benthic assemblages. An experimental approach     

Ana Catarina Torres  Marcos Rubal  Isabel Sousa‐Pinto  Puri Veiga 《Marine Ecology》2019,40(6)

The effect of harvesting on the diversity and structure of benthic assemblages is nowadays a relevant component of fishery management. Invertebrate harvesting is increasing worldwide and sea urchins are one of the main invertebrate target species. However, current knowledge about the effects of sea urchin harvesting on benthic assemblages is still poor. The aim of this study is to evaluate the influence of Paracentrotus lividus (Lamark, 1816) harvesting on tide pool assemblages from intertidal rocky shores. To achieve this objective, a field removal experiment was done for 10 months. Results of univariate and multivariate analyses showed that P. lividus harvesting had a significant effect on the number of taxa and structure of the benthic assemblage. Assemblages from pools where P. lividus were removed showed significant differences against controls; namely, where P. lividus were eliminated, pools showed higher number of taxa than control pools. This result contrasts with previous studies assessing effects of invertebrate harvesting that generally have found a biodiversity reduction in the exploited habitat. Despite this apparently positive effect of P. lividus harvesting, we should be cautious because effects of P. lividus harvesting on higher trophic levels or during long periods of time remain unexplored.  相似文献