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"Llanos"
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Territorial Rule in Colombia and the Transformation of the Llanos Orientales
Until the 1980s, Colombia's Llanos Orientales was a frontier, a vast tropical grassland plain east of the Andes. Populated mainly by indigenous people, it was considered \"primitive\" by much of the rest of Colombia. All of that changed when exploitable petroleum deposits were discovered, and the Llanos was transformed into the fastest growing region in the country.
Rausch surveys sixty years of the area's history, from La Violencia-the civil war that rocked the country from 1948 to 1958-and the presidency of Rojas Pinilla, who helped pacify the Llanos in the late 1950s, to the National Front agreement between the Conservative and Liberal parties during the 1960s, its aftermath, and the rapid changes during the last half of the twentieth century. Using archival research and her own first-hand experiences, Jane Rausch examines the Colombian government's Llanos policies and the political, economic, and social changes they have brought about. This book brings to a strong conclusion Rausch's large-scale historical survey of a region: one sharing much in common with other South American frontiers and critical to Colombia's present and future.
eBook
Local environmental factors influence beta-diversity patterns of tropical fish assemblages more than spatial factors
A major goal in ecology is to understand mechanisms that influence patterns of biodiversity and community assembly at various spatial and temporal scales. Understanding how community composition is created and maintained also is critical for natural resource management and biological conservation. In this study, we investigated environmental and spatial factors influencing beta diversity of local fish assemblages along the longitudinal gradient of a nearly pristine Neotropical river in the Colombian Llanos. Standardized surveys were conducted during the low-water season at 34 sites within the Bita River Basin. Physical, chemical, and landscape parameters were recorded at each site, and asymmetric eigenvector maps were used as spatial variables. To examine the relative influence of dispersal and environmental variables on beta diversity and its components, distance-based redundancy analysis (db-RDA) and variation partitioning analysis were conducted. We proposed that spatial scale of analysis and position within the river network would constrain patterns of beta diversity in different ways. However, results indicated that in this system, high beta diversity was consistent among species assemblages no matter the scale of analysis or position within the river network. Species replacement (turnover) dominated beta diversity, an indication of the importance of species sorting. These findings suggested that conservation of fish diversity in tropical rivers requires maintenance of both habitat heterogeneity (spatial variation in habitat conditions) and connectivity at the scale of entire river basins.
Journal Article
Parque Astronómico de Atacama: An Ideal Site for Millimeter, Submillimeter, and Mid-Infrared Astronomy
The area of Chajnantor, at more than 5000 m altitude in northern Chile, offers unique atmospheric and operational conditions which arguably make it the best site in the world for millimeter, submillimeter, and mid-infrared observatories. Long-term monitoring of the precipitable water vapor (PWV) column on the Chajnantor plateau has shown its extreme dryness with annual median values of 1.1 mm. Simultaneous measurements of PWV on the Chajnantor plateau (5050 m) and on Cerro Chajnantor (5612 m) show that the latter is around 36% lower under normal atmospheric conditions and up to 80% lower than the plateau in the presence of temperature inversion layers. Recently, the Government of Chile has consolidated the creation of the Parque Astronómico de Atacama (Atacama Astronomical Park), an initiative of the Chilean Commission for Science and Technology (CONICYT). This new park offers an opportunity for national and international projects to settle within its boundaries, gain access to an extremely dry site that is suitable for observations over a broad spectral range, especially in the millimeter to mid-infrared wavelengths, and benefit from operational and logistical support within a secure legal framework.
Journal Article
Notes on the Genus Bacopa (Plantaginaceae, Gratioleae) in the Orinoquia Region of Colombia and Venezuela
Bacopa llanorum, a new species from the seasonally flooded savannas of the “Llanos” region of Colombia (Arauca department) is described and illustrated, and its morphological relationships are discussed. On the basis of its dimorphic leaves (the innermost blade filiform, uppermost lanceolate-ovate), the new species does not appear to be allied to any other Bacopa species. However, it shares several other features with B. reptans. A new combination, Bacopa debilis, is proposed to replace Caconapea debilis. In addition, ecological information of the genus in “Los Llanos” of Colombia and Venezuela, and ecological and floristic notes about the eolic-limose plains, are included. A key for identifying species of Bacopa in this region is also provided. Bacopa llanorum is remarkable for its foliar dimorphism, in an otherwise predominantly homomorphic-leaved genus, and it increases to 20 the number of species of the genus in the “Llanos del Orinoco” bioregion.
Journal Article
Mercury, Cadmium, and Lead Levels in Human Placenta: A Systematic Review
Background: Placental tissue may furnish information on the exposure of both mother and fetus. Mercury (Hg), cadmium (Cd), and lead (Pb) are toxicants of interest in pregnancy because they are associated with alterations in child development. Objectives: The aim of this study was to summarize the available information regarding total Hg, Cd, and Pb levels in human placenta and possible related factors. Methods: We performed a systematic search of PubMed/MEDLINE, EMBASE, Lilacs, OSH, and Web of Science for original papers on total Hg, Cd, or Pb levels in human placenta that were published in English or Spanish (1976—2011). Data on study design, population characteristics, collection and analysis of placenta specimens, and main results were extracted using a standardized form. Results: We found a total of 79 papers (73 different studies). Hg, Cd, and Pb levels were reported in 24, 46, and 46 studies, respectively. Most studies included small convenience samples of healthy pregnant women. Studies were heterogeneous regarding populations selected, processing of specimens, and presentation of results. Hg concentrations > 50 ng/g were found in China (Shanghai), Japan, and the Faroe Islands. Cd levels ranged from 1.2 ng/g to 53 ng/g and were highest in the United States, Japan, and Eastern Europe. Pb showed the greatest variability, with levels ranging from 1.18 ng/g in China (Shanghai) to 500 ng/g in a polluted area of Poland. Conclusion: The use of the placenta as a biomarker to assess heavy metals exposure is not properly developed because of heterogeneity among the studies. International standardized protocols are needed to enhance comparability and increase the usefulness of this promising tissue in biomonitoring studies.
Journal Article
Current Forest–Savanna Transition in Northern South America Departs from Typical Climatic Thresholds
The forest–savanna transition is the most widespread ecotone in the tropics, with important ecological, climatic, and biogeochemical implications at local to global scales. However, the factors and mechanisms that control this transition vary among continents and regions. Here, we analyzed which factors best explain the transition in northern South America (Llanos ecoregion and northwestern Amazon), where common thresholds on typical environmental factors (for example, mean annual precipitation (MAP), wet season precipitation) fail to predict it. For instance, savannas in the Llanos occur at MAP levels (> 1500 mm) which are typical of forests in other tropical regions. We examined the transition’s climate features, soils, and disturbance (fire frequency) spaces using remotely sensed data. We used logistic generalized linear models to assess the effect of seasonal (season length) and intra-seasonal (daily precipitation frequency and intensity) precipitation metrics during the dry season, soil silt content, and fire frequency, on the transition using canopy cover, tree cover, and the maximum Plant Area Volume Density as vegetation structure descriptor variables. Fire frequency and precipitation frequency were the most important variables explaining the transition. Although most fires occur in savannas, we found that a significant percentage of savanna pixels (46%) had no fires. This study indicates that the transition should be characterized regionally in response to biogeographic differences (for example, climatic space) among regions and continents. Our results highlight the importance of fire frequency and intra-seasonal precipitation in determining the transition in northern South America. Furthermore, future studies should consider regional differences in the climatic space of forest and savanna to improve projections of global change impacts on these highly diverse ecosystems.
Journal Article
The Escribano of Babel: Power, Exile, and Enslavement in the Venezuelan Llanos During the War of Independence (1806–1833)
This article traces the professional life of Rafael Almarza, the last royal escribano (notary) of Mérida in the captaincy of Venezuela, and his role in undermining monarchical authority among the enslaved community displaced in the plains region (Los Llanos) during the war of independence in 1814-18. Despite their status as minor officials within the Spanish imperial bureaucracy, notaries, through the records they made, helped to establish legally binding truths underlying everyday actions, making them influential agents of colonial rule in the community they served, particularly among those seeking notarial documents to obtain freedom. During the battles for independence, escribanos like Almarza facilitated the transition of sovereignty and created documents that fomented the independence cause among enslaved individuals during the years of total war. By examining the manumission documents found in the notarial book Almarza kept during exile, the author of this article shows the importance of enslaved people in granting legitimacy to the emerging leadership of José Antonio Páez and the Republican project. At the same time, this study aims to provide a new look at manumission during the early stages of nation-building and the involvement of underrepresented groups in this process.
Journal Article
A Palynological Zonation for the Cenozoic of the Llanos and Llanos Foothills of Colombia
Hydrocarbon exploration in the Llanos Foothills of Colombia has intensified during the past several decades. Exploration in this region is problematic owing to structural complexities, rapid lateral facies changes, and the difficulties of acquiring good seismic imaging. These elements increase the uncertainties about the prognosis and subsequent drilling of exploratory wells. Under these conditions, biostratigraphy can play a significant role in the exploratory process. In the Llanos Foothills, palynology is the most useful biostratigraphic tool because pollen is the most abundant fossil group. In this study we analyze pollen information from 70 sections (624,744 palynomorph grains from 6707 samples) to construct a biostratigraphic zonation for the Llanos Foothills and Llanos basins. Using both graphic correlation and constrained optimization in our analysis, we propose 18 palynological zones for the Cenozoic of the Llanos and Llanos Foothills. These zones are tied to the geological timescale using 18 calibration points that include carbon isotopes, foraminifera, and magnetostratigraphy.
Journal Article