Impact of climate variability on summer fires in a Mediterranean environment (northeastern Iberian Peninsula)     

Marco Turco  Maria Carmen Llasat  Jost von Hardenberg  Antonello Provenzale 《Climatic change》2013,116(3-4):665-678

We analyse the impact of climate interannual variability on summer forest fires in Catalonia (northeastern Iberian Peninsula). The study period covers 25 years, from 1983 to 2007. During this period more than 16000 fire events were recorded and the total burned area was more than 240 kha, i.e. around 7.5% of whole Catalonia. We show that the interannual variability of summer fires is significantly correlated with summer precipitation and summer maximum temperature. In addition, fires are significantly related to antecedent climate conditions, showing positive correlation with lagged precipitation and negative correlation with lagged temperatures, both with a time lag of two years, and negative correlation with the minimum temperature in the spring of the same year. The interaction between antecedent climate conditions and fire variability highlights the importance of climate not only in regulating fuel flammability, but also fuel structure. On the basis of these results, we discuss a simple regression model that explains up to 76% of the variance of the Burned Area and up to 91% of the variance of the number of fires. This simple regression model produces reliable out-of-sample predictions of the impact of climate variability on summer forest fires and it could be used to estimate fire response to different climate change scenarios, assuming that climate-vegetation-humans-fire interactions will not change significantly.  相似文献   

The Zoning of Semi-Enclosed Bodies of Water According to the Sediment Pollution: The Bay of Algeciras as a Case Example     

Elisa Rojo-Nieto  Carmen Garrido-Pérez  Giorgio Anfuso-Melfi  Francisco Lopez-Aguayo  Diego Sales-Marquez  Jose Antonio Perales-Vargas-Machuca 《Estuaries and Coasts》2011,34(6):1129-1139

This paper reports a study of the occurrence and levels of polycyclic aromatic hydrocarbons (PAHs) in a bay characterised by a chronic persistent impact. A total of 55 sediment samples were taken at different depths up to 111 m in two sampling campaigns. Chemical analyses were carried out by gas chromatography-mass spectroscopy. The results indicate that: (1) significant spatial variations exist, (2) levels of PAHs are related more strongly to the spatial distribution of sediments than to mineralogy/granulometry, (3) the sediments are slightly-to-moderately contaminated by PAHs, and (4) these PAHs derive from pyrolytic and petrogenic sources. Through use of an innovative data classification system (proposed according to depth and spatial location of sampling points), and using factorial and cluster techniques, five zones have been differentiated depending on the contamination level and source.  相似文献   

Hydrologic characteristics of Appalachian loose‐dumped spoil in the Cumberland Plateau of eastern Kentucky     

Timothy J. Taylor  Carmen T. Agouridis  Richard C. Warner  Christopher D. Barton  Patrick N. Angel 《水文研究》2009,23(23):3372-3381

Heavily compacted lands, typical of traditional surface mine reclamation techniques, have been shown to hinder tree growth, increase levels of flooding, and produce suboptimal water quality. Utilizing loose‐dumped spoil, in accordance with the Forestry Reclamation Approach (FRA), has demonstrated success with regards to promoting tree growth and survival; however, additional information is needed to assess the potential of FRA to ameliorate other environmental concerns related to water quantity. To better understand the hydrologic characteristics of loose‐dumped spoil, key hydrograph parameters (discharge volume, peak discharge, discharge duration, lag time, and response time) were monitored for three common spoil types: (1) predominately brown weathered sandstone, (2) predominately gray weathered sandstone, and (3) a mixture of both sandstones and shale. Although spoil types were found to differ hydrologically, these differences were relatively minor. Measured discharge volumes were low (averaging 12% of rainfall for all events and treatments), peak discharge rates were small (between 2·5 × 10^?5 and 3 × 10^?3 m³/s), and the duration of discharge was long (6 days on average). From a hydrologic perspective, the results of this study indicate that mine spoils need not be segregated for reclamation as long as the spoil is placed in accordance with the loose‐dumped techniques as outlined in the FRA. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

Black shales and massive sulfide deposits: causal or casual relationships? Insights from Rammelsberg, Tharsis, and Draa Sfar     

Reinaldo S��ez  Carmen Moreno  Felipe Gonz��lez  Gabriel R. Almod��var 《Mineralium Deposita》2011,46(5-6):585-614

Black shales and massive sulfides represent reduced lithofacies that require isolation from oxic environments to be preserved. This, together with the sedimentary affinity of both lithofacies, can explain their common concurrence in the geologic record. The present study is based on the comparison of Rammelsberg in Germany, Tharsis in Spain, and Draa Sfar in Morocco, three massive sulfide deposits closely associated with black shales that are distributed along the European and North African Variscan orogen. The study entails geochemical, biostratigraphic, and stratigraphic analyses of the black shale sequences hosting the three deposits and mineralogical and textural analyses of the sulfides. All three deposits were formed in immature, tectonically unstable basins within an active continental margin or continental magmatic arc. Their stratigraphic records consist of a sequence of black shales enclosing massive sulfides and variable proportions of bimodal volcanic and subvolcanic rocks. The major differences among the three deposits concern the size, composition, and mineralogy. Regarding age, they are diachronous and younger southward: Rammelsberg is middle Eifelian, Tharsis latest Famennian, and Draa Sfar late Viséan. The study of redox conditions of the paleoenvironment using organic and inorganic proxies highlights similarities and significant differences among the three ore-hosting basins during massive sulfide and black shale deposition. The black shales generally display low C_org and high S_tot contents. At Rammelsberg, the S_tot/C_tot ratios provide values typical for normal Middle Devonian marine environments, which suggests that the original reactive organic C is now fixed in carbonates. At Tharsis, most of the samples have C_org >1 and S_tot/C_org values equivalent to those of Devonian?CCarboniferous normal marine sediments. However, some pyritic hanging-wall samples have C_org <1 and S_tot up to 5?wt.%, suggesting the epigenetic addition of HS^?. The S_tot/C_org ratio for the Draa Sfar samples resembles that of Middle Carboniferous normal marine environments. Geochemical inorganic proxies used to define the environmental conditions include the enrichment factors of U (U_EF) and Mo (Mo_EF) together with V/Cr and V/(V?+?Ni) ratios. Footwall shales at Filón Norte (Tharsis) show positive and eventually elevated U_EF and Mo_EF values, which suggests anoxic conditions, whereas at Rammelsberg and Draa Sfar oxic bottom water is indicated. The relations V/Cr and V/(V + Ni) in all three cases point to a redox boundary near the sediment?Cwater interface, although at Tharsis some samples indicate anoxic/euxinic conditions (i.e., V/(V + Ni) >0.9). Regarding the environmental conditions of the source areas, feldspar illitization and selective depletion in Na and Ca occurred at the three studies sites. Available sulfur isotopic data from the Rammelsberg and Tharsis sulfide ore indicate that biogenic reduction of marine sulfate was a major sulfur source during massive sulfide generation. Nevertheless, a hydrothermal sulfur source has also been detected. At Rammelsberg, this is indicated from the polymetallic sulfides that replace sedimentary and diagenetic pyrite. At Tharsis, the bacteriogenic sulfur signature is also restricted to sulfide with less evolved textures, whereas a hydrothermal source is more evident in sulfides showing evidence of recrystallization. Both geochemical and isotopic data suggest that the bacteriogenic reduction process was inhibited by rapid burial. The sedimentation rates calculated for Rammelsberg, Tharsis, and Draa Sfar were in the range 7?C13, 8?C14, and 19?C27?cm/ka, respectively. Continuous sedimentation of black shale favored the isolation of the massive sulfides and organic material from bottom waters and hence favored their preservation. Accordingly, the relationships between black shales and massive sulfides are considered to be casual. Nevertheless, the tectono-sedimentary evolution of each basin controlled the deposition of both black shales and massive sulfides and the parameters that favored their coeval deposition.  相似文献   

A deep, stratigraphically and structurally controlled landslide: the case of Mount La Civita (Molise, Italy)   总被引：2，自引：0，他引：2  

Pietro P. C. Aucelli  Emilio Casciello  Massimo Cesarano  Sebastiano Perriello Zampelli  Carmen M. Rosskopf 《Landslides》2013,10(5):645-656

The present paper illustrates the results of an integrated study of a large landslide located on the southern slope of Mount la Civita (Molise, Southern Apennine), an E–W elongated, SSE dipping and 890-m-high monocline carbonate ridge. The upper part of the slope affected by the landslide is largely controlled by strata attitude while its basal part is marked by a strike–slip fault causing the tectonic juxtaposition of the carbonate successions against predominantly clayey flysch units. An integrated study, including geological, geomorphological and geotechnical investigations, was carried out to determine the features of the landslide and to plan further investigation and monitoring. In particular, from 2002 to 2004, Differential Global Positioning System monitoring and core drillings, coupled with inclinometer measurements, were carried out to determine the landslide’s kinematics, extent, depth to the surface of rupture and rates of movement. Inclinometer data revealed the presence of the rupture surface at a depth of about 20 m. DGPS monitoring allowed rates of movement up to several tens of centimetres per year to be recorded. The nearby village of Civitanova del Sannio can still be considered at risk due to the landslide, as recent remedial works, consisting mainly of very shallow re-shaping of the slope by blasting and partial filling of trenches, did not succeed in stopping its movement.  相似文献   

Land-use and vegetation-cover mapping of an indigenous land area in the state of Mato Grosso (Brazil) based on spectral linear mixing model,segmentation and region classification     

Fernando Shinji Kawakubo  Rubia Gomes Morato  Carmen Lucia Midaglia  Maria Lucia Cereda Gomide  Ailton Luchiari 《国际地球制图》2013,28(2):165-175

A spectral linear-mixing model using Landsat ETM+ imagery was undertaken to estimate fraction images of green vegetation, soil and shade in an indigenous land area in the state of Mato Grosso in the central-western region of Brazil. The fraction images were used to classify different types of land use and vegetation cover. The fraction images were classified by the following two methods: (a) application of a segmentation based on the region-growing technique; and (b) grouping of the regions segmented using the per-region unsupervised classifier named ISOSEG. Adopting a 75% threshold, ISOSEG generated 44 clusters that were grouped into eight land-use and vegetation-cover classes. The mapping achieved an average accuracy of 83%, showing that the methodology is efficient in mapping areas of great land-use and vegetation-cover diversity, such as that found in the Brazilian cerrado (savanna).  相似文献   

Artificial neural networks and geostatistical models for housing valuations in urban residential areas     

M. Carmen Morillo Balsera  Sandra Martínez-Cuevas  Iñigo Molina Sánchez  César García-Aranda  M. Estibaliz Martinez Izquierdo 《Geografisk tidskrift / udgivet af Bestyrelsen for Det Kongelige danske geografiske selskab》2013,113(2):184-193

Property valuation studies often use classical statistics techniques. Among these techniques, the Artificial Neural Networks are the most applied, overcoming the inflexibility and the linearity of the hedonic models. Other researchers have used Geostatistics techniques, specifically the Kriging Method, for interpreting spatial-temporal variability and to predict housing unit prices. The innovation of this study is to highlight how the Kriging Method can help to better understand the urban environment, improving the results obtained by classical statistics. This study presents two different methods that share the general objective of extracting information regarding a city’s housing from datasets. The procedures applied are Ordinary Kriging (Geostatistics) and Multi-Layer Perceptron algorithm (Artificial Neural Networks). These methods were used to predict housing unit prices in the municipality of Pozuelo de Alarcon (Madrid). The implementation of both methods provides us with the urban characteristics of the study area and the most significant variables related to price. The main conclusion is that the Ordinary Kriging models and the Neural Networks models, applied to predicting housing unit prices are necessary methodologies to improve the information obtained in classical statistical techniques.

Abbreviations: ANN: Artificial Neural Networks; OK: ordinary Kriging; MLP: multi-layer perceptron  相似文献   

Epibiotic traits of the invasive red seaweed Acanthophora spicifera in La Paz Bay,South Baja California (Eastern Pacific)     

Enrique Ávila  María del Carmen Méndez‐Trejo  Rafael Riosmena‐Rodríguez  Juan M. López‐Vivas  Abel Sentíes 《Marine Ecology》2012,33(4):470-480

The aim of this study was to analyze the interaction of a non‐native macroalga (Acanthophora spicifera) with native macroalgae (Sargassum spp.) and sponge assemblages in a subtropical embayment of the Mexican Pacific. The intensity of A. spicifera epiphytism on the native seaweed Sargassum varied significantly over time and was inversely related to the Sargassum density and size. The higher intensity (up to 28 individuals per host plant) occurred when Sargassum was smaller and was lower in density (senescence period). The lower intensity was recorded during the growth period of Sargassum and the subsequent increase in intensity was attributed to a high fragmentation period of A. spicifera, which was evidenced by a decrease in its average size and biomass and by the presence of larger free‐floating accumulations on the subtidal zone. The facultative interaction between A. spicifera and Sargassum appears to be neutral, as no negative or positive effects were found for epiphytic or basibiont seaweeds. However, this invasive seaweed characteristically monopolizes almost all types of hard substrate, and its effects on other algae and benthic organisms should be investigated. Moreover, A. spicifera was often epizoic on epilithic sponges. This invasive seaweed was found anchored on the sponge tissue by rhizome‐like structures. In addition, free‐floating fronds of A. spicifera were frequently found carrying small pieces of the basibiont sponge in its basis (60% of them with eggs and embryos), which suggests a novel facilitation mechanism for some sponge species, as the A. spicifera epizoism could favor fragmentation, dispersal and recruitment of these invertebrates. This study shows that A. spicifera is not only a species that adapts rapidly to the new conditions of the receiving environment but, due to its epibiotic traits, it can directly interact with and influence the life histories of some native species.  相似文献   

Study of the Contributions of Non‐Specific and Specific Interactions during Fluoxetine Adsorption onto Activated Carbons     

Silvia Román  João Manuel Valente Nabais  Juan Félix González  Carmen María González‐García  Angel Luis Ortiz 《洁净——土壤、空气、水》2012,40(7):698-705

The adsorption of fluoxetine onto activated carbons (ACs) prepared from almond tree pruning by steam and CO₂ activation under different temperature conditions (650–950°C), was studied. In both series increasing the temperature caused an increase in the BET apparent surface area, yielding ACs with S_BET up to 870 and 710 m² g^?1 after steam and CO₂ activation, respectively. Also, a slight widening of the porosity was found in both cases. In order to modify the functionality of the ACs, two of them were impregnated with triethylenediamine (TEDA) prior to the adsorption process, which caused a decrease in the AC apparent surface mainly due to micropore blockage. The fluoxetine adsorption isotherms at 25°C showed maximum adsorption capacities between 110 and 224 mg g^?1. The adsorption isotherms were analyzed using Langmuir and Freundlich models. Although the impregnation reduced the pore volume, it did not cause a decrease in the fluoxetine maximum adsorption capacity, but a modification in the adsorption mechanism was observed.  相似文献   

4D Arctic: A Glimpse into the Structure and Evolution of the Arctic in the Light of New Geophysical Maps,Plate Tectonics and Tomographic Models     

Carmen Gaina  Sergei Medvedev  Trond H. Torsvik  Ivan Koulakov  Stephanie C. Werner 《Surveys in Geophysics》2014,35(5):1095-1122

Knowledge about the Arctic tectonic structure has changed in the last decade as a large number of new datasets have been collected and systematized. Here, we review the most updated, publicly available Circum-Arctic digital compilations of magnetic and gravity data together with new models of the Arctic’s crust. Available tomographic models have also been scrutinized and evaluated for their potential to reveal the deeper structure of the Arctic region. Although the age and opening mechanisms of the Amerasia Basin are still difficult to establish in detail, interpreted subducted slabs that reside in the High Arctic’s lower mantle point to one or two episodes of subduction that consumed crust of possibly Late Cretaceous–Jurassic age. The origin of major igneous activity during the Cretaceous in the central Arctic (the Alpha–Mendeleev Ridge) and in the proximity of rifted margins (the so-called High Arctic Large Igneous Province—HALIP) is still debated. Models of global plate circuits and the connection with the deep mantle are used here to re-evaluate a possible link between Arctic volcanism and mantle plumes.  相似文献