Development of a drought vulnerability index using MCDM and GIS: study case in São Paulo and Ceará, Brazil     

de Azevedo Reis  Gabriela  de Souza Filho  Francisco Assis  Nelson  Donald Robert  Rocha  Renan Vieira  da Silva  Samiria Maria Oliveira 《Natural Hazards》2020,104(2):1781-1799

Natural Hazards - Although climate change vulnerability research in general has increased over the last decade, Latin American countries have more directed more limited efforts toward vulnerability...  相似文献   

Vegetation evolution by ecological succession as a potential bioindicator of landslides relative age in Southwestern Mediterranean region     

Lopes  Luís Filipe  Oliveira  Sérgio Cruz  Neto  Carlos  Zêzere  José Luís 《Natural Hazards》2020,103(1):599-622

Natural Hazards - Landslides have a direct impact in the ecosystems dynamics being considered one of the main vegetation perturbation processes. Our objective is to determine the relation between...  相似文献   

El Niño and La Niña influence on mean river flows of southern South America in the 20th century     

Guillermo J. Berri  Emilio Bianchi  Gabriela V. Müller 《水文科学杂志》2019,64(8):900-909

The influence of the El Niño Southern Oscillation (ENSO) phenomenon on monthly mean river flows of 12 rivers in the extreme south of South America in the 20th century is analysed. The original dataset of each river is divided into two subsets, i.e. warm ENSO events or El Niño, and cold ENSO events or La Niña. The elements of the subsets are composites of 24 consecutive months, from January of the year when the ENSO event begins to December of the following year. The ENSO signal is analysed by comparing the monthly mean value of each subset to the long-term monthly mean. The results reveal that, in general, monthly mean El Niño (La Niña) river flows are predominantly larger (smaller) than the long-term monthly mean in the rivers studied. The anomalies are more evident during the second half of the year in which the event starts and the first months of the following year.  相似文献   

Competition Between Littoral Cladocerans Macrothrix triserialis and Alona rectangula (Cladocera) in Relation to Algal Food Level and Inoculation Density     

S. Nandini  Gloria Muro‐Cruz  S. S. S. Sarma 《洁净——土壤、空气、水》2002,30(1):16-23

We studied the relative competitive abilities of littoral cladocerans M.triserialis and A. rectangula using green algal food at two levels (0.5 · 10⁶ and 2 · 10⁶ cells mL⁻¹ of Chlorella) under five different inoculation ratios. Both the cladoceran species were influenced by food availability and mutual competitive pressure. Macrothrix could withstand competition better under conditions of lower food availability while Alona grew better, despite competition, when more Chlorella was available. Population growth rates (r) ranged from 0.022…0.070 for Alona and from 0.024…0.075 for Macrothrix. There was a significant impact of the inoculation ratio on the maximal population density reached by either test species. Food concentration had a significant influence on the peak population density reached only for Alona rectangula. Data on the body sizes of M. triserialis and A. rectangula showed that there was a higher somatic growth with increasing food availability and decreased competitive pressure in both the test species. In Macrothrix, food concentration and the competition from Alona through different initial inoculation densities had a significant impact on the body size. At the lower food concentration, the body size was significantly smaller when the inoculation density was lowest (highest competitive pressure). The body size of Alona, on the other hand, was not affected by the competition but was significantly higher under conditions of greater food availability. These results have been discussed in light of different theories of competition.  相似文献   

Evolutionary convergence of the highly adapted desert rodent Tympanoctomys barrerae (Octodontidae)     

Ricardo A. Ojeda  Carlos E. Borghi  Gabriela B. Diaz  Stella M. Giannoni  Michael A. Mares  Janet K. Braun 《Journal of Arid Environments》1999,41(4):443

Octodontid rodents have a long evolutionary history in arid landscapes of South America. The red vizcacha rat, Tympanoctomys barrerae , is a monotypic, micro-endemic species that inhabits salt pan-sand dune habitats in west-central Argentina. Its natural history is almost unknown. We present an analysis of the ecology, morphology, behavior, and physiology of the red vizcacha rat and assess the overall degree of convergence of this species with rodents that inhabit similar habitats in different deserts. Our results show that Tympanoctomys barrerae is highly adapted to salt flat basin habitats. Its diet of halophytic vegetation with a high salt content, and physiological and anatomical traits related to salt consumption, are similar to those found in some members of the families Heteromyidae (Dipodomys microps) of North America, and Muridae (Psammomys obesus and Rhombomys opimus) of Africa and Asia. Similarities include feeding behavior, diet composition, kidney morphology, and urine concentration, among other traits. Tympanoctomys barrerae is more similar to these desert rodents than it is to confamilials that do not feed on halophytes.  相似文献   

Kidney structure and allometry of Argentine desert rodents     

Gabriela B. Diaz  Ricardo A. Ojeda 《Journal of Arid Environments》1999,41(4):453

Two large groups of rodents inhabit South America: the hystricognaths and the murids. It has been postulated that while the former show a high degree of specialization to desert habitats, the murids are not well adapted to xeric conditions. We studied the renal structure and function of selected desert-dwelling murid and octodontid (hystricognath) rodents from Argentina to evaluate levels of adaptation to aridity. Our results show that the murids Salinomys, Andalgalomys, Calomys and Eligmodontia have the highest renal indices and urine concentration among Argentine desert rodents. The octodontid Tympanoctomys barrerae shows higher renal indices and urine osmolarity than those of its close relativesOctomys mimax and Octodontomys gliroides . We compare the renal traits of the Argentine desert murids with those of other world-desert rodents such as North American heteromyid rodents. The results show that these Argentine murid rodents posses renal adaptations to conditions which are as impressive as those of both octodontids and the classic desert-adapted heteromyids.  相似文献   

Sensitivity of near-surface Tropical Instability Waves to submonthly wind forcing in the tropical Atlantic     

Gabriela Athi  Frdric Marin  Anne-Marie Treguier  Bernard Bourls  Catherine Guiavarc&#x;h 《Ocean Modelling》2009,30(4):241-255

This study demonstrates the sensitivity of the near-surface properties in the tropical Atlantic Ocean to the high-frequency of the winds in numerical simulations. At intra-seasonal timescales (2–50 days), two distinct period ranges dominate the variability in the upper ocean: periods between 2 and 20 days, which are essentially wind-forced and periods between 20 and 50 days, due mostly to Tropical Instability Waves (TIWs). Using a numerical model forced by different wind fields, it is shown that the characteristics of the intra-seasonal variability in the ocean surface mixed-layer are strongly dependent on the wind forcing. Submonthly winds are shown to force large variability in the upper ocean that can strikingly decrease the amplitude of the TIWs in the mixed-layer and their imprint on the horizontal distribution of sea surface temperatures. Wind products containing too much energy at submonthly periods thus prevent wind-forced simulations from reproducing a realistic surface signature of TIWs, when compared to satellite observations of sea surface temperature. In addition, submonthly wind variability may be responsible for part of the observed interannual variability of the TIW signature in the temperature. The impact of submonthly winds is strongest in the mixed-layer: beneath the mixed-layer, all simulations show similar characteristics of the TIWs.  相似文献   

Parametric model identification of high-speed craft dynamics     

Rocío Muñoz-Mansilla  Joaquín Aranda  José Manuel Díaz  J de la Cruz 《Ocean Engineering》2009,36(12-13):1025-1038

Parametric models of heave, pitch and roll dynamics of a high-speed craft have been estimated for different wave incidence angles in the frequency domain. Several issues that make the identification problem interesting are the following: type of parameterization, starting values, non-quadratic functions, excitation signals and short data record. The method employed guarantees a fine linear approximation of the nonlinear dynamics of a fast ship for the ultimate goal of stabilization control to reduce motion sickness associated with heave, pitch and roll accelerations. In addition, the approach achieves high-quality starting values and avoids non-quadratic terms in the cost function, which results in less computational load and significantly more accurate models when compared with a previous method employed for the same problem.  相似文献   

Analyses of bottom simulating reflections offshore Arauco and Coyhaique (Chile)   总被引：1，自引：1，他引：0  

Ivan de la Cruz Vargas Cordero  Umberta Tinivella  Flavio Accaino  Maria Filomena Loreto  Francesco Fanucci  Christian Reichert 《Geo-Marine Letters》2010,30(3-4):271-281

Two seismic sections offshore Arauco and Coyhaique, Chile, have been analysed to better define the seismic character of hydrate-bearing sediments. The velocity analysis was used to estimate the gas-phase concentration, which can serve to correlate hydrate presence to the geological features. The velocity model allowed us to recognise the hydrate layer above the bottom simulating reflector (BSR), and the free gas layer below it. The velocity field is affected by strong lateral variation, showing maximum (above the BSR) and minimum (below the BSR) values in the southern sector. Here, highest gas hydrate and free gas concentrations were calculated (15% and 2.7% of total volume respectively). The estimated geothermal gradient ranges from 35 to 95°C/km. In the northern sector, the highest gas hydrate and free gas concentrations are 15% and 0.2% of total volume respectively, and the geothermal gradient is uniform and equal to about 30°C/km.  相似文献   

Changes in ostracod assemblages and morphologies during lake‐level variations of Lago Cardiel (49°S), Patagonia,Argentina, over the last 15.6 ka     

Lorena Ramos  Marta Alperin  Antje Schwalb  Vera Markgraf  Daniel Ariztegui  Gabriela Cusminsky 《Boreas: An International Journal of Quaternary Research》2019,48(3):746-760

Changes in the ostracod assemblages from two sediment cores collected from Lago Cardiel in southeastern Patagonia (49°S) reflect the main regional abrupt climatic changes over the last 15.6 cal. ka BP. Shifts in species abundance and switches in dominances suggest that these were mainly driven by variable salinity. During the Late Pleistocene, Limnocythere rionegroensis was abundant and dominant, indicating waters with high salinity and prevalence of evaporative processes. Between 12.6 and 10.8 cal. ka BP, Lago Cardiel expanded markedly and reached an Early Holocene highstand of +55 m above present lake level. A major change in ostracod assemblage in which Limnocythere patagonica appears as the dominant species in parallel with the disappearance of L. rionegroensis and Eucypris aff. cecryphalium mirrored this transitional period between the cold and dry Late Pleistocene and the humid and warm Early Holocene. Over the last 4 cal. ka BP, L. rionegroensis returned to the species assemblage and Riocypris whatleyi increased its abundance pointing towards increasing salinities. The variations in size, shape and ornamentation of L. rionegroensis and R. whatleyi fossil valves were examined using geometric morphometric techniques and further compared to those of modern Patagonian sites. Limnocythere rionegroensis specimens displayed high morphological variability during the evolution of Lago Cardiel. More specifically, the switch in reproductive mode – from sexual to parthenogenetic– and the increase in valve ornamentation around 12.7 cal. ka BP suggest that these changes were promoted by the hydrological alteration that occurred in the Late Pleistocene. This exercise provides a robust range of morphological variation for these proxies, which will be useful in further taxonomic and palaeoenvironmental studies adding more information about different factors influencing the observed morphological trends.  相似文献