Revues reçues

O recurso polínico coletado por operárias de Melipona seminigra merrillae Cockerell, Melipona fulva Lepeletier, Trigona fulviventris (Smith) e CephaloTrigona femorata Guérin, no Campus da UFAM, Manaus (AM) foi estudado no período de março a outubro de 2001. Noventa tipos polínicos foram coletados pelas abelhas, distribuídos em 31 famílias, 67 gêneros e 10 formas Tipo. Trigona fulviventris diversificou mais suas coletas, utilizando 58 fontes no período. O tamanho do nicho polínico utilizado pelas abelhas ficou assim distribuído: T. fulviventris (58), M.s. merrillae (41), C. femorata (34) e M. fulva (25). Dos tipos determinados, os que mais contribuíram para a dieta das abelhas, apresentando as maiores freqüências nas amostras de pólen, foram Miconia myriantha (12,91%), Leucaena leucocephala (9,52%), Tapirira guianensis (6,53%), Eugenia stipitata (6,22%), Protium heptaphyllum (6,17%) e Vismia guianensis (5,93%). As abelhas de modo geral concentraram suas coletas em um número reduzido de espécies vegetais e com um grau diferenciado de uso para cada uma das fontes. Tipos polínicos com freqüência acima de 10% ocorreram em pequena proporção na maioria dos meses, sendo responsáveis por mais de 50% do total do pólen coletado em cada mês. A utilização das fontes de pólen variou conforme a espécie. T. fulviventris teve uma dieta mais ampla e diversificada, enquanto M. fulva foi a que menos diversificou suas coletas. T. fulviventris apresentou maior uniformidade no uso das fontes polínicas e a sobreposição de nichos polínicos foi maior entre M.s. merrillae e M. fulva e menor entre T. fulviventris e C. femorata.The objective of this study was to characterize the resources used by Amazonian bees Melipona seminigra merrillae, Melipona fulva, Trigona fulviventris and CephaloTrigona femorata, in an urban Forest patch at Manaus city from March to October 2001. The pollen analysis determined 90 pollen types, distributed in 31 families, 67 genera and 10 palynologycal types unidentified. Trigona fulviventris was the bee species that presented the most diversified pollen types, using 58 sources in that period. The size of pollen types used were distributed as follows: T. fulviventris (58), M.s. merrilae (41), C. femorata (34) and M. fulva (25). Plant species contributing the most for the diet of the bees and presenting the highest frequencies on the pollen samples were Miconia myriantha (12,91%), Leucaena leucocephalla (9,52%), Tapirira guianensis (6,53%), Eugenia stipitata (6,22%), Protium heptaphyllum (6,17%) and Vismia guianensis (5,93%). Generally the bees concentrated their collections on a reduced number of plant species and with a differentiated degree of use for each source. Pollen types with frequency above 10% occurred in a small proportion for most months, being responsible for more than 50% of all the pollen collected every month. Pollen source used varied according to the species, T. fulviventris had a more broad and diversified diet, whereas M. fulva was the bees species that least diversified its diet. T. fulviventris presented higher uniformity on the use of pollen sources and the pollen niches overlap was higher between M.s. merrillae and M. fulva and lower between T. fulviventris and C. femorata

Southern oscillation signal in South American palaeoclimatic data of the last 7000 years

During strong El Niño events, rainfall anomalies and changes in wind patterns are observed in different regions of South America. Along the central Brazilian coast, during the 1983 El Niño year, the frontal systems were blocked to the south, provoking a reversal of the longshore sand transport. Long-duration reversals of longshore transport were also recorded in Holocene beach-ridge terraces from the Rio Doce coastal plain. This led to the formulation of a model relating these reversals of longshore transport to El Niño-like conditions. El Niño-like conditions are past average climate situations that generate the same perturbations as the strong El Niño events observed during the last decade. They are likely to correspond to the long-duration low phase of the Southern Oscillation. To confirm this hypothesis we compared the Holocene beach-ridge record with other palaeoenvironmental records from regions where strong El Niño events would have a substancial signal as well: (1) water-level fluctuations of Lake Titicaca, (2) a pollen and sediment record in an eastern Amazonian lake, (3) changes of the Rio Xingu discharge in eastern Amazonia, and (4) variations of sand supply at the Rio Piura and Rio Chira outlets in the Sechura Desert. The occurrences of El Niño-like conditions were numerous before 3900-3600 yr B.P., absent between 3900-3600 and 2800-2500 yr B.P., and infrequent after 2800-2500 yr B.P. © 1993 University of Washington

The evolution of the continental and coastal environments during the last climatic cycle in Brazil (120 KY. B.P. to present)

Studies done in Brazil, under the CNPq (Brazil) and ORSTOM (France) agreement, allowed us to envisage the general trend of climatic changes that occurred during the last 60,000 years. At first, examination of successive accumulation and erosion phases, recorded within Central Brazilian valley deposits, provided evidence of importam changes in slope vegetation cover and in the hydraulic regime of water courses, and hence characteristics of precipitation and climate regimes. Studies of Tamanduá river valley deposits in the town of São Simão (State of São Paulo) showed that between 32 and 21 ky. B.P. the climate was humid, whereas between 17 and 11 ky. B.P. it was dry with very scarce and strong rains. From 10 ky to 8.5 ky. B.P. the climate was humid too. Finally, after 7.5 ky. B.P. the deposits revealed the existence of several dry episodes within a globally humid climate. Palynological and sedimentological analyses of lacustrine deposits sampled by vibrocorers in the Eastern Amazon (Carajás, State of Pará) and in Central Brazil (Salitre, State of Minas Gerais) permitted us to outline the evolutionary history of the vegetation cover within these regions during the last 60,000 years for Carajás and 30,000 years for Salitre and thus to have a preliminary idea about their past climates. Then, it was possible to show that at Carajás regression of the evergreen rainforest occurred four times, at about 60, 40, between 23-11 and 7-4 ky. B.P. Moreover, apparently the last rainforest regression episode was quite different from the previous three episodes. At Salitre, the most characteristic is the indication of the existence of Araucária forest between 12 and 8.5 ky. B.P. This Araucária forest location is clearly much further north than at present, which suggests that during that time the climate was wetter and colder. Finally, studies developed along the central Brazilian coast allowed us to show evidence of wind-/driven change in littoral dynamics during the last 5 ky. A detailed examination of Doce river (State of Espírito Santo) mouth beach-ridge geometry has shown inversions in littoral drift direction as a consequence of change in wave and then in wind regimes, reflecting characteristics of atmospheric circulation during the last 5 ky.Estudos feitos no Brasil, segundo um acordo entre o CNPq (Brasil) e ORSTOM (França), permitiram-nos vislumbrar a tendência geral de mudanças climáticas que ocorreram durante os últimos 60.000 anos. Primeiramente, o estudo de sucessivas fases de erosão e sedimentação, registradas nos depósitos de vale do Brasil Central, forneceram evidências de importantes mudanças na cobertura vegetal de vertentes e no regime hidráulico de cursos fluviais e então chegando-se às características dos regimes pluviométricos e climáticos. Estudos de depósitos do vale do rio Tamanduá na cidade de São Simão (SP) mostraram que entre 32 e 21 ka. A.P. o clima foi úmido, enquanto entre 17 e 11 ka. A.P. ele foi seco com chuvas esparsas e fortes. De 10 ka. a 8,5 ka. A.P. o clima foi também úmido. Finalmente, após 7,5 ka. A.P. os depósitos revelaram a existência de vários episódios secos através do clima globalmente úmido. Análises palinológicas e sedimentológicas de depósitos lacustres amostrados por vibrotestemunhador na Amazônia Oriental (Carajás, PA) e no Brasil Central (Salitre, MG) permitiram delinear a história evolutiva da cobertura vegetal nessas regiões, durante os últimos 60.000 anos para Carajás e 30.000 anos para Salitre, e então ter uma idéia preliminar sobre seus paleoclimas. Então foi possível mostrar que em Carajás por quatro vezes, há cerca de 60, 40, entre 23-11 e 7-4 Ka. A.P., ocorreu a regressão da floresta pluvial perene. Além disso, aparentemente o último episódio de regressão da floresta pluvial foi bem diferente dos três episódios anteriores. Em Salitre, mais característica é a indicação da existência de floresta de Araucária entre 12 e 8,5 Ka. A.P. A localização desta floresta de Araucária está claramente mais ao norte que atualmente, sugerindo que durante aquela época o clima era mais úmido e mais frio. Finalmente, estudos desenvolvidos na costa do Brasil Central mostraram evidências de mudanças na dinâmica costeira comandadas pelo vento durante os últimos 5 Ka. Um estudo detalhado da geometria das cristas praiais de desembocadura do rio Doce (ES) mostrou inversões no sentido da deriva litorânea como conseqüência de mudanças nos regimes da onda e do vento, permitindo conhecer as características da circulação atmosférica durante os últimos 5 Ka

The Agenda-Building Effects of US Presidents: A Close Look at US Presidents and Media Coverage of Palestine

The purpose of this study was to determine if U.S. news media coverage of Palestine, an international news issue, reflects agenda-building. All presidential discourse on Palestine in the Weekly Compilation of Presidential Documents and all articles in The New York Times, The Wall Street Journal and Detroit Free Press that reference the same were counted and documented on a weekly basis for the years of 1993, 1994, 2001 and 2002. Once the amount of coverage was plotted, a closer look at five week spans during each year using qualitative content analysis determined if similar specific issues were discussed in presidential discourse (William Jefferson Clinton and George Walker Bush) and news coverage. Results of the descriptive content analysis study indicated that there is a relationship in the amount of coverage and the type of issues emphasized by the media and the President on Palestine; however, there is not a consistent pattern to indicate media coverage increases prior to presidential discourse, or vice versa. Presidents and the media do have similar amounts of coverage, do focus on similar issues and often carry similar themes. There are also similar amounts of coverage and types of issues covered by the three media sources and the two presidents in the study. This study brought a new type of methodology to Agenda-Setting/Agenda-Building Research by taking a closer look at issues and themes using Qualitative Content Analysis

Long-Term Vegetation Dynamics in a Megadiverse Hotspot: The Ice-Age Record of a Pre-montane Forest of Central Ecuador.

Tropical ecosystems play a key role in many aspects of Earth system dynamics currently of global concern, including carbon sequestration and biodiversity. To accurately understand complex tropical systems it is necessary to parameterise key ecological aspects, such as rates of change (RoC), species turnover, dynamism, resilience, or stability. To obtain a long-term (>50 years) perspective on these ecological aspects we must turn to the fossil record. However, compared to temperate zones, collecting continuous sedimentary archives in the lowland tropics is often difficult due to the active landscape processes, with potentially frequent volcanic, tectonic, and/or fluvial events confounding sediment deposition, preservation, and recovery. Consequently, the nature, and drivers, of vegetation dynamics during the last glacial are barely known from many non-montane tropical landscapes. One of the first lowland Amazonian locations from which palaeoecological data were obtained was an outcrop near Mera (Ecuador). Mera was discovered, and analysed, by Paul Colinvaux in the 1980s, but his interpretation of the data as indicative of a forested glacial period were criticised based on the ecology and age control. Here we present new palaeoecological data from a lake located less than 10 km away from Mera. Sediment cores raised from Laguna Pindo (1250 masl; 1°27'S, 78°05'W) have been shown to span the late last glacial period [50-13 cal kyr BP (calibrated kiloyears before present)]. The palaeoecological information obtained from Laguna Pindo indicate that the region was characterised by a relatively stable plant community, formed by taxa nowadays common at both mid and high elevations. was the dominant taxon until around 30 cal kyr BP, when it was replaced by , Asteraceae and among other taxa. Heat intolerant taxa including , , and peaked around the onset of the Last Glacial Maximum (c. 21 cal kyr BP). The results obtained from Laguna Pindo support Colinvaux's hypothesis that glacial cooling resulted in a reshuffling of taxa in the region but did not lead to a loss of the forest structure. Wide tolerances of the plant species occurring to glacial temperature range and cloud formation have been suggested to explain Pindo forest stability. This scenario is radically different than the present situation, so vulnerability of the tropical pre-montane forest is highlighted to be increased in the next decades

Sporormiella as a tool for detecting the presence of large herbivores in the Neotropics

The reliability of using the abundance of Sporormiella spores as a proxy for the presence and abundance of megaherbivores was tested in southern Brazil. Mud-water interface samples from nine lakes, in which cattle-use was categorized as high, medium, or low, were assayed for Sporormiella representation. The sampling design allowed an analysis of both the influence of the number of animals using the shoreline and the distance of the sampling site from the nearest shoreline. Sporormiella was found to be a reliable proxy for the presence of large livestock. The concentration and abundance of spores declined from the edge of the lake toward the center, with the strongest response being in sites with high livestock use. Consistent with prior studies in temperate regions, we find that Sporormiella spores are a useful proxy to study the extinction of Pleistocene megafauna or the arrival of European livestock in Neotropical landscapes

Impact of mid-to-late Holocene precipitation changes on vegetation across lowland tropical South America: a palaeo-data synthesis

A multi-proxy paleo-data synthesis of 110 sites is presented, exploring the impact of mid-to-late Holocene precipitation changes upon vegetation across Southern Hemisphere tropical South America. We show that the most significant vegetation changes occurred in south-west Amazonia and south-east Brazil, regions reliant on precipitation derived from the South American summer monsoon (SASM). A drier mid Holocene in these regions, linked to a weaker SASM, favoured more open vegetation (savannah/grasslands) than present, while increased late-Holocene precipitation drove expansion of humid forests (e.g. evergreen tropical forest in south-west Amazonia, Araucaria forests in south-east Brazil). The tropical forests of central, western and eastern Amazonia remained largely intact throughout this 6000-year period. North-eastern Brazil's climate is 'antiphased' with the rest of tropical South America, but a lack of paleo data limits our understanding of how vegetation responded to a wetter(drier) mid(late) Holocene. From this paleo-data perspective, we conclude that ecotonal forests already close to their climatic thresholds are most vulnerable to predicted future drought, but the forest biome in the core of Amazonia is likely to be more resilient. Of greater concern is widespread deforestation and uncontrolled anthropogenic burning, which will decrease ecosystem resilience, making them more vulnerable than they might be without current anthropogenic pressures

Accountant's perception on the factors affecting the adoption of international financial reporting standards in Yemen

The purpose of this study is to examine the accountants’ perception of International Financial Reporting Standards (IFRSs) adoption and the requirement and expected period for the adoption of IFRSs in Yemeni companies. In addition, this study examines the accountants’ opinion whether or not the following factors government policy, capital market, economic growth, external environment/international exposure, professional bodies, education level of accountants, company size, initial cost of IFRSs adoption and culture affect the adoption of IFRSs in Yemen. This study also examines the differences in opinion between academicians and practitioners regarding IFRSs and factors which affect its adoption. Yemen has still not adopted the IFRSs. In this regard, this study carried out a survey using 48 Yemeni accounting postgraduate students in Malaysia’s public Universities to collected data, which was then analysed using SPSS. The results of this study show that the majority of respondents perceive the benefits of adopting IFRSs in Yemeni companies. Moreover, majority of respondents (82.9%) agree that Yemeni companies should adopt IFRSs. About 58.6% of respondents expect the period of IFRSs adoption in Yemen to be within three to 10 years, while 41.5% expect it to be more than 10 years. The respondents believe that the lack of government policy, absence of capital market, lack of economic growth, lack of professional bodies, weakness in the education level of accountants, the small size of the companies and initial cost of IFRSs adoption affect the adoption of IFRSs in Yemen. The study also shows that the international environment has a weak effect on IFRSs adoption while the Yemeni culture does not affect IFRS adoption. The results of this study may help policy-makers and the Yemeni Association of Certified Public Accountants (YACPA) to make more precise decisions regarding IFRSs adoption in Yeme