902 resultados para TEMPORAL DYNAMICS
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Pós-graduação em Geociências e Meio Ambiente - IGCE
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As variações sazonal e nictemeral do fitoplâncton e dos parâmetros hidrológicos foram estudadas em uma estação fixa (00º46'37.2"S-046º43'24.5"W) localizada na Ilha Canela (Bragança-Pará) em setembro e dezembro de 2004 e março e junho de 2005. Amostras subsuperficiais de água foram coletadas para os estudos qualitativos, quantitativos e para a determinação das concentrações de clorofila a. Simultaneamente, foram medidos os parâmetros físico-químicos da água: salinidade, temperatura, pH, oxigênio dissolvido e percentual de saturação. Foram identificados 64 táxons entre Cyanophyta (um táxon), Bacillariophyta (54 táxons) e Dinophyta (nove táxons). A concentração de clorofila a variou de 4,67 mg m-3 (período seco) a 5,44 mg m-3 (período chuvoso) e acompanhou a densidade fitoplanctônica, que foi mais elevada durante o período chuvoso (média=1.870 x 103 cél L-1). Os fitoflagelados dominaram quantitativamente o fitoplâncton local, seguidos pelas diatomáceas. Dimeregramma minor e Skeletonema sp. constituíram espécies muito freqüentes e muito abundantes. A ressuspensão de sedimentos provocadas pelos intensos ventos e a arrebentação das ondas favoreceram a dominância de D. minor durante o período seco. No período chuvoso, a elevada pluviometria, os moderados ventos, bem como a influência das águas estuarinas do Taperaçu e Caeté, propiciaram a redução da salinidade e o desenvolvimento de outras espécies fitoplanctônicas.
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A região amazônica tem sido submetida a contínuo desflorestamento e expansão do uso da terra, para a implantação de atividades como pecuária, exploração madeireira, agricultura, mineração e urbanização. A queima e a decomposição da biomassa da floresta liberam gases que contribuem para o efeito estufa, como o dióxido de carbono (CO2). Nesse contexto, surge o interesse em avaliar a dinâmica do efluxo de CO2 do solo na Amazônia, em especial em sistemas agroflorestais de palma de óleo (Elaeis guineensis), visto o destaque da produção dessa cultura no estado do Pará, que teve uma razoável expansão, transformando o estado do Pará em um dos maiores plantadores e produtores do país. Este trabalho teve como objetivo investigar a dinâmica do efluxo de CO2 do solo em sistemas agroflorestais onde a palma de óleo é a cultura principal, na escala temporal e os fatores bióticos e abióticos que influenciam diretamente neste processo. Foram quantificados os carbono da biomassa microbiana do solo, carbono total do solo, respiração microbiana do solo, raízes finas do solo e zona de influência das espécies; e os fatores abióticos: umidade e temperatura do solo, em dois sistemas agroflorestais de cultivo de palma de óleo, o sistema adubadeiras e o sistema biodiverso. As medições foram feitas nos períodos seco e no chuvoso. Os resultados mostraram que o maior efluxo de CO2 do solo ocorreu no período chuvoso, provavelmente devido à maior atividade microbiana nesse período influenciada por fatores climáticos aliados a fatores bióticos. O sistema biodiverso apresentou maior efluxo de CO2 do solo do que o sistema adubadeiras, provavelmente devido à maior atividade biológica no solo nesse sistema. O efluxo de CO2 do solo não mostrou correlação forte com as variáveis testadas. Pôde-se concluir que o efluxo de CO2 do solo sofreu influencia apenas da sazonalidade climática. O fato da área de plantio ser muito jovem pode ser um fator determinante para que não tenha sido encontrada relação mais forte da respiração do solo com as variáveis analisadas.
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The object of this work was to study the dynamics of evaporation in the Itumbiara reservoir, located in Central Brazil, using MODIS-derived water surface temperature (product MOD11A1) and meteorological data acquired over the water surface. The evaporation rates were derived from latent heat flux, estimated through a mass transfer model. The estimates were carried out for the period between 1/1/2010 and 31/12/2010. The results showed that evaporation rate tends to increase from January to September and then decrease from September to December. The evaporation rate reached values near 20 mm day-1 in Itumbiara reservoir during the dry season in 2010. The mean evaporation rate for the wet season was 3.66 mm day-1 and 8.25 mm day-1 for the dry season. The total water volume evaporated from Itumbiara reservoir during 2010 was estimated at about 1.7 billion m³ (2,300 mm) which represents 10% of total reservoir volume. The results suggest that advection is the main transport mechanism which drives the evaporation in Itumbiara. The convective processes contribute secondarily to evaporation in Itumbiara reservoir.
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Pós-graduação em Agronomia (Irrigação e Drenagem) - FCA
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Dengue virus is a major public health problem worldwide. Aedes (Stegomyia) aegypti is the main dengue vector. Since there is no specific treatment or effective vaccine, control measure is focused on vector control. It is believed that population density is higher in the warmer/rainy season than in cold/dry. The study aimed to genetically characterize population dynamics of Ae. aegypti during climatic variations. Collections were performed at least once in both periods over five years by oviposition traps at Botucatu city. The technique of TaqMan allelic discrimination was used for genetic analysis, in which SNPs from nine genes distributed on three chromosomes of the mosquito were genotyped. Bayesian analysis did not show variance on population structure over the five year period. The percentage of variation among samples in statistical analysis was low (Fst = 0.0028, p = 0.7634), furthermore the allele frequencies were constant. The results show that despite wide variation in the density of adults, population size does not vary. Therefore, there is variation in the prevalence of the species life stages: adults in warmer/rainy, and possibly eggs in cold/dry, resulting in different control strategies for each period. Moreover, estimation of population size should not consider only winged adults, but all other found life stages forms
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This work seeks to explain the historical perspective of the building temporal western, showing the concepts of morphogenesis and morphodynamics as contemporary representations of geographical science for the synthesis forged about time. In this sense, it is the perspective of time in the Middle Ages, its implications and social substantiality, as interposed to time erected by the rise of a merchant class in Europe, we seek to present the social conception of this category in the West, stating that this not constituted as a supra-social element, but built by the organization itself and internal contradiction of European society. Finally, we saw the delineations drawn by geography, set in propositions about the dynamics of nature and society, such being the latest concepts in terms of the logic of assimilation weather prevailing. For this, we use literature review and comparison of temporal models at different times for the delineation of the contours of the research... (Complete abstract click electronic access below)
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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
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Pós-graduação em Biociências - FCLAS
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The wetlands of south-central Nebraska’s Rainwater Basin region are considered of international importance as a habitat for millions of migratory birds, but are being endangered by agricultural practices. The Rainwater Basin extends across 17 counties and covers 4,000 square miles. The purpose of this study was to assemble baseline chemical data for several representative wetlands across the Rainwater Basin region, and determine the use of these chemical data for investigating groundwater recharge. Eight representative wetlands were chosen across the Rainwater Basin to monitor surface and groundwater chemistry. At each site, a shallow well and deep well were installed and sampled once in the summer of 2009 and again in the spring of 2010. Wetland surface water was sampled monthly from April, 2009 to May, 2010. Waters were analyzed for major ions, nutrients, pesticides and oxygen-18 and deuterium isotopes at the University of Nebraska Water Sciences Laboratory. Geochemical analysis of surface waters presents a range of temporal and spatial variations. Wetlands had variable water volumes, isotopic compositions, ion chemistries and agricultural contaminant levels throughout the year and, except for a few trends, theses variations cannot be predicted with certainty year-to-year or wetland-to-wetland. Isotopic compositions showed evaporation was a contributor to water loss, and thus, did impact water chemistry. Surface water nitrate concentrations ranged from <0.10 to 4.04 mg/L. The nitrate levels are much higher in the groundwater, ranging from <0.10 to 18.4 mg/L, and are of concern because they are found above the maximum contaminant level (MCL) of 10 mg/L. Atrazine concentrations in surface waters ranged from <0.05 to 10.3 ppb. Groundwater atrazine concentrations ranged from <0.05 to 0.28 ppb. The high atrazine concentrations in surface waters are of concern as they are above the MCL of 3 ppb, and the highest levels occur during the spring bird migration. Most sampled groundwaters had detectable tritium indicating a mix of modern (<5 to 10 years old) and submodern (older than 1950s) recharge. The groundwater also had differences in chemical and isotope composition, and in some cases, increased nitrate concentrations, between the two sampling periods. Modern groundwater tritium ages and changes in groundwater chemical and isotopic compositions may indicate connections with surface waters in the Rainwater Basin.
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Patterns of population dynamics of Loligo plei and Loligo sanpaidensis in Southeastern Brazil were investigated with samples obtained from commercial catches and research cruises from 1999 to 2000 and from 2002 to 2003. Size and maturity Structure of the two species varied according to depth and season. Body size decreased with depth for L plei, whereas for L. sanpaidensis size increased with depth LIP to 100 m and decreased again in deeper areas. GSI and incidence of mature animals decreased with depth in both species. L. plei females matured at a larger size in summer, while size at maturity in L. sanpaulensis was greater in autumn. For L. plei, reproductive events Occurred in the late winter and spring, in depths up to 40 m, and during summer in inshore waters. L. sanpaidensis increased reproductive activity ill Summer, winter and spring between depths of 30 and 80 Ill. The presence of high proportions of immature Squid offshore Suggests that juveniles might develop in these areas and, upon maturation, migrate back to inshore waters to spawn, particularly in spring and Summer. However, differences found in aggregation patterns in different depth strata, as well as the seasonal differences found in the size structure of L. plei and L. sanpaidensis, Could ultimately be due to Changes in the water Column related to food availability. Considering that L. plei and L. sanpaidensis are both caught as by-catch by shrimp trawlers throughout file year, we also discuss hypotheses on the life cycle of the species and its implications for fishery management. We recommend measures to protect squid spawning grounds by creating spring and summer protected areas where trawling would be prohibited until 60 m depth, i.e. in the area and time of year when mature individuals concentrate.
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The temporal and spatial variation of Paralonchurus brasiliensis density (fish per m(2)) in relation to environmental factors was studied on the coasts of Ubatuba and Caraguatatuba, south-eastern Brazil. The fish were collected by shrimp fishery trawl on a monthly basis from January to December, 2002. Seven depths were previously established and for each one the temperature, salinity, organic matter content and grain size of the sediment (phi) was measured. The seasonal analysis of temperature and salinity indicated the presence of the water masses South Atlantic Central Water (SACW) and Coastal Waters (CW) acting in the study area. A total of 29,808 fish were collected during the study period. The highest densities were registered during the summer and autumn indicating an association with CW. The fish population moved to shallow depths during the intrusion of the cold water mass, SACW. The highest densities were registered in depths where the sediment composition ranged from fine sand to silt-clay. Thus, the temperature and type of the sediment are the main environmental factors which affect the spatial-temporal variation of P. brasiliensis density in south-eastern Brazil.
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Objective. To identify the existence of spatial and temporal patterns in the occurrence of intentional homicides in the municipality of Sao Paulo (MSP), Brazil, and to discuss the analytical value of taking such patterns into account when designing studies that address the dynamics and factors associated with the incidence of homicides. Methods. A longitudinal ecological study was conducted, having as units of analysis 13 205 census tracts and the 96 census districts that congregate these sectors in Sao Paulo. All intentional homicides reported in the city between 2000 and 2008 were analyzed. The gross homicide rates per 100 000 population was calculated as well as the global and local Bayesian estimates for each census tract during the study period. To verify the possibility of identifying different patterns of the spatial distribution of homicides, we used BoxMap and Moran's I index. Results. The homicide trends in the city of Sao Paulo in the last decade were not homogeneous and systematic. Instead, seven patterns of spatial distribution were identified; that is, seven spatial regimes for the occurrence of intentional homicides, considering the homicide rates within each census tract as well as the rates in adjacent tracts. These spatial distribution regimes were not contained within the limits of the census tracts and districts. Conclusions. The results show the importance of analyzing the spatial distribution of social phenomena without restriction of political and administrative boundaries.
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Background: The temporal and geographical diversification of Neotropical insects remains poorly understood because of the complex changes in geological and climatic conditions that occurred during the Cenozoic. To better understand extant patterns in Neotropical biodiversity, we investigated the evolutionary history of three Neotropical swallowtail Troidini genera (Papilionidae). First, DNA-based species delimitation analyses were conducted to assess species boundaries within Neotropical Troidini using an enlarged fragment of the standard barcode gene. Molecularly delineated species were then used to infer a time-calibrated species-level phylogeny based on a three-gene dataset and Bayesian dating analyses. The corresponding chronogram was used to explore their temporal and geographical diversification through distinct likelihood-based methods. Results: The phylogeny for Neotropical Troidini was well resolved and strongly supported. Molecular dating and biogeographic analyses indicate that the extant lineages of Neotropical Troidini have a late Eocene (33-42 Ma) origin in North America. Two independent lineages (Battus and Euryades + Parides) reached South America via the GAARlandia temporary connection, and later became extinct in North America. They only began substantive diversification during the early Miocene in Amazonia. Macroevolutionary analysis supports the "museum model" of diversification, rather than Pleistocene refugia, as the best explanation for the diversification of these lineages. Conclusions: This study demonstrates that: (i) current Neotropical biodiversity may have originated ex situ; (ii) the GAARlandia bridge was important in facilitating invasions of South America; (iii) colonization of Amazonia initiated the crown diversification of these swallowtails; and (iv) Amazonia is not only a species-rich region but also acted as a sanctuary for the dynamics of this diversity. In particular, Amazonia probably allowed the persistence of old lineages and contributed to the steady accumulation of diversity over time with constant net diversification rates, a result that contrasts with previous studies on other South American butterflies.
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Polythermal glaciers, i.e. glaciers with a combination of ice at and below the freezing point, are widespread in arctic and subarctic environments. The polythermal structure has major implications for glacier hydrology, ice flow and glacial erosion. However, the interplay of factors governing its spatial and temporal variations such as net mass balance, ice advection and water content in the ice is poorly investigated and as yet not fully understood. This study deals with a thorough investigation of the polythermal regime on Storglaciären, northern Sweden, a small valley glacier with a cold surface layer in the ablation area. Extensive field work was performed including mapping of the cold surface layer using ground-penetrating radar, ice temperature measurements, mass balance and ice velocity measurements. Analyses of these data combined with numerical modelling were used specifically to investigate the spatial and temporal variability of the cold surface layer, the spatial distribution of the water content just below the cold surface layer transition, the effect of radar frequency on the detection of the surface layer, and the sensitivity of the cold surface layer to changes in forcing. A comparison between direct temperature measurements in boreholes and ground-penetrating surveys shows that the radar-inferred cold-temperate transition depth is within ±1 m from the melting point of ice at frequencies above ~300 MHz. At frequencies below ~155 MHz, the accuracy degrades because of reduced scattering efficiency that occurs when the scatterers become much smaller compared to the wavelength. The mapped spatial pattern of the englacial cold-temperate transition boundary is complex. This pattern reflects the observed spatial variation in net loss of ice at the surface by ablation and vertical advection of ice, which is suggested to provide the predominant forcing of the cold surface layer thickness pattern. This is further supported by thermomechanical modeling of the cold surface layer, which indicates high sensitivity of the cold surface layer thickness to changes in vertical advection rates. The water content is the least investigated quantity that is relevant for the thermal regime of glaciers, but also the most difficult to assess. Spatial variability of absolute water content in the temperate ice immediately below the cold surface layer on Storglaciären was determined by combining relative estimates of water content from ground-penetrating radar data with absolute determination from temperature measurements and the thermal boundary condition at the freezing front. These measurements indicate large-scale spatial variability in the water content, which seems to arise from variations in entrapment of water at the firn-ice transition. However, this variability cannot alone explain the spatial pattern in the thermal regime on Storglaciären. Repeated surveys of the cold surface layer show a 22% average thinning of the cold surface layer on Storglaciären between 1989 and 2001. Transient thermomechanical modeling results suggest that the cold surface layer adapts to new equilibrium conditions in only a few decades after a perturbation in the forcing is introduced. An increased winter air temperature since mid-1980s seems to be the cause of the observed thinning of the cold surface layer. Over the last decades, mass balance measurements indicate that the glacier has been close to a steady state. The quasi-steady state situation is also reflected in the vertical advection, which shows no significant changes during the last decades. Increased winter temperatures at the ice surface would result in a slow-down of the formation of cold ice at the base of the cold surface layer and lead to a larger imbalance between net loss of ice at the surface and freezing of temperate ice at the cold-temperate transition.