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Paleoecology of the southern Gran Sabana (SE Venezuela) since the last glacial to the presentMontoya Romo, Encarnación 14 June 2011 (has links)
This thesis is aimed to study the paleoecology of the southern Gran Sabana region (GS; SE Venezuela) since the Late Glacial to the present. This region is characterized nowadays by the occurrence of large extent of savannas in a climate suitable for rainforests. For this purpose, three sequences (two from peat bogs and one from lake sediments) have been analyzed for pollen and spores, non‐pollen palynomorphs (NPP), and microscopic charcoal particles. Among the sequences analyzed, two of them are located currently within treeless savannas (Lakes Chonita and Encantada); whereas the third one is placed in the boundary between GS savannas and Amazon forests (El Paují). The Late Glacial interval of Lake Chonita was characterized by a shrubland that was replaced by a treeless savanna at the end of Younger Dryas (YD) and the onset of the Holocene, linked to the occurrence of regional fires since ca. 12.4 cal kyr BP. The beginning of local fires was dated synchronous with the vegetation replacement, ca. 11.7 cal kyr BP. A similar shrubland, though not identical, is located nowadays around 200 m elevation above the lake, so the replacement by surrounding savannas was interpreted as a probably upward displacement of the former vegetation and an increase in average temperatures of approximately 0.7 ‐ 1.5ºC. This section represents the oldest interval analyzed for GS so far, and the presence of fires during the Late Pleistocene is among the oldest fire records documented for northern South America. The peat bog records of Lake Encantada and El Paují showed the main vegetation trends of the last 8 cal kyr BP, which were characterized by the continuous occurrence of regional fires. In Lake Encantada, the presence of treeless savannas was reported during the whole interval analyzed as the dominant vegetation type, despite variations in forest abundance and composition taxa of the community also occurred. The vegetation changes in this record were interpreted as mainly due to climatic shifts until the Late Holocene. At El Paují, the occurrence of forests and savanna/forest mosaics was reported during the same interval, and fire was postulated to have been the major driver of the vegetation shifts. In this sequence, a treeless savanna was not recorded as the dominant vegetation of the landscape until the last millennia, and the presence of two different indigenous cultures was postulated as responsible of the shifts in fire regime registered, with an interval of human land abandonment between them. This interval was characterized by the cessation of fires, and the establishment of a secondary dry forest. The Late Holocene was characterized, in the three sequences studied, by a sudden increase of fires, which likely favored the expansion of savannas and the establishment of the present GS landscape. The join interpretation of the records presented in this thesis, together with previous analyses in the region, highlighted some key aspects for understanding the main trends of GS landscape and vegetation, e.g., the appearance and establishment of morichales (Mauritia palm stands typical of current southern GS landscapes) has been restricted to the last two millennia, synchronous with the increase in fire incidence. Moreover, it has been possible to gather empirical evidence for testing some previous hypothesis regarding GS. For example, the proposal of an extended aridity prior the Holocene has been rejected, whereas the hypothesis about the post‐glacial expansion of morichales has been supported. In this sense, with all the available information to date, some suggestions have been proposed: (i) Climate and fire have been the major forcing factors operating in the GS; (ii) During the Late Glacial and the beginning of the Early Holocene, the landscape of southern GS was likely formed by a mosaic of forests, shrubs, and savannas, without the current supremacy of the last vegetation type, which only established during the last 2 cal kyr BP onwards; (iii) Some general climatic trends have been inferred for the study area, as for example an increase in average temperatures around the Late Glacial/Early Holocene transition, a dry interval from 8 to 5 cal kyr BP, and a wetter phase during the Mid‐Holocene centered around 4 cal kyr BP; (iv) The establishment of Mauritia in the region has been likely driven by a synergism between biogeographical, climatic and anthropogenic factors, as well as the likely pyrophilous nature of this palm given its synchronous appearance with the increase of fires; (v) The settlement of the modern indigenous culture (Pemón) occurred at least since around ca. 2000 cal yr BP onwards, 1500 yr earlier than previously thought, but previous human presence in the region has been also documented; and (vi) The fire activity observed in the long‐term has caused a huge impact on GS landscape. / El presente trabajo está centrado en la paleoecología de la región sur de la Gran Sabana (GS; SE Venezuela) desde el Tardiglacial hasta el presente. Esta región se caracteriza hoy en día por la presencia de sabanas en un clima propicio para el desarrollo de bosques. Para ello, se llevó a cabo el análisis de 3 secuencias (dos de turberas y una de sedimentos lacustres), basado principalmente en la identificación de polen y palinomorfos no polínicos (NPP), y en el análisis de microcarbones. Dos de las secuencias analizadas (Chonita y Encantada) se encuentran actualmente emplazadas en sabanas, mientras que la tercera (El Paují) pertenece a una localidad fronteriza entre sabanas de GS y bosques amazónicos. El intervalo Tardiglacial de la secuencia del Lago Chonita se caracterizó por la presencia de una comunidad arbustiva, que fue reemplazada por una sabana de manera sincrónica con el final del Younger Dryas (YD) y el comienzo del Holoceno. Se documentó la presencia de fuegos regionales desde ca. 12.4 cal kyr BP, mientras que el comienzo de los fuegos locales ocurrió sincrónico con el reemplazamiento de la vegetación, ca. 11.7 cal kyr BP. En la actualidad, un arbustal similar está presente a unos 200 m del lago, por lo que el cambio de vegetación se interpretó como resultado de un desplazamiento altitudinal, proponiéndose un aumento de las temperaturas medias alrededor de 0.7 ‐ 1.5ºC. Esta secuencia es la más antigua hasta la fecha para GS, y la presencia de fuegos supone uno de los registros de incendios más antiguos para el norte de Sudamérica. Las secuencias de la Laguna Encantada y El Paují mostraron las principales variaciones de la vegetación desde los últimos 8 cal kyr BP hasta el presente, que estuvieron caracterizadas por la presencia de fuegos regionales desde el principio. En la Laguna Encantada se observó la presencia continua de sabanas como vegetación dominante, a pesar de que también se registraran variaciones en la abundancia de taxones forestales. Las variaciones de la vegetación parecieron responder principalmente a las condiciones climáticas hasta el Holoceno Tardío. En El Paují, se observó la presencia de bosques y mosaicos bosque/sabana, siendo el fuego el agente que ejerció una mayor influencia en los cambios de vegetación registrados. En esta secuencia la presencia de sabana como vegetación dominante no se observó hasta los últimos milenios, y se propuso la existencia de dos culturas indígenas diferentes con un lapso de abandono intermedio, como responsables del régimen de incendios. Este intervalo de abandono se caracterizó por un cese de incendios y la aparición de un bosque seco secundario. El Holoceno Tardío estuvo caracterizado en las tres secuencias por un aumento drástico del régimen de fuegos, lo que favoreció la expansión de sabanas y el establecimiento del paisaje actual. La interpretación conjunta de estas secuencias y otras analizadas previamente ha puesto de manifiesto varios aspectos claves para el entendimiento de las tendencias de la vegetación de la región, como por ejemplo, que la aparición y establecimiento de los morichales (comunidades casi monoespecíficas de Mauritia) se haya producido durante los últimos dos milenios, y de manera sincrónica con el aumento de fuegos. A su vez, ha servido para evaluar algunas hipótesis existentes sobre el origen y evolución del paisaje de GS. Por ejemplo, la existencia de climas áridos antes del Holoceno ha sido cuestionada, mientras que la hipótesis acerca de una expansión post‐glacial de los morichales parece reforzarse. De este modo, con la información obtenida hasta el momento se han sugerido varias hipótesis: (i) Los principales agentes causantes de las variaciones de la vegetación en GS han sido el clima y el fuego; (ii) El paisaje del sur de GS estuvo probablemente formado durante el Tardiglaciar y el principio del Holoceno por un mosaico entre bosques, arbustales y sabanas, sin la predominancia actual de este último tipo de vegetación, estableciéndose el paisaje actual hace alrededor de 2000 años; (iii) Se han inferido algunas tendencias climáticas regionales, como un posible aumento de las temperaturas medias al comienzo del Holoceno, un intervalo seco entre 8 y 5 cal kyr BP, y una fase más húmeda durante el Holoceno Medio centrada ca. 4 cal kyr BP; (iv) El establecimiento de Mauritia en la región es posiblemente el resultado de la interacción entre factores biogeográficos, climáticos y antrópicos, y se ha propuesto la probable naturaleza pirófila de esta palmera debido a su aparición sincrónica con el aumento del régimen de incendios; (v) El asentamiento del actual grupo indígena que puebla la zona (los Pemón) se debió producir, como mínimo, hace unos 2000 años, unos 1500 años antes de lo propuesto hasta ahora, aunque han sido documentadas presencias antrópicas anteriores; y (vi) La incidencia de fuegos a largo plazo observada ha provocado un gran impacto en el paisaje de GS.
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The agricultural land use and settlement patterns of the Sabana de Bogotá, ColombiaRau, Herbert Lawrence, January 1958 (has links)
Thesis--Northwestern University. / eContent provider-neutral record in process. Description based on print version record. Includes bibliographies.
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Del vástago al ecosistema: un enfoque progresivo a la modelización de las sabanas neotropicalesSegarra Berenguer, José Gabriel 14 December 2012 (has links)
No description available.
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Água e paisagem agrícola entre os grupos pré-hispânicos da Sabana de Bogotá - Colômbia / Water and agricultural landscape among pre-Hispanic groups in Sabana de Bogotá, ColombiaGallo, Diana Lorena Rodriguez 02 June 2015 (has links)
O Sistema Hidráulico de Campos Elevados de Cultivo, Camellones, construído ao longo de 2500 anos pelos grupos pré-hispânicos da Sabana de Bogotá, Colômbia, é o tema central da presente tese. O nosso trabalho focou na relação estabelecida entre estes grupos e a água, para determinar de que maneira a interação entre ambos levou a uma forma particular de exploração dos recursos e de ocupação do território. O objetivo geral da pesquisa foi entender como foi organizada a espacialidade e as atividades cotidianas, especificamente durante o período Muisca Tardio (1000 - 1550 DC), em torno do sistema hidráulico, isto é, como se construiu uma paisagem agrícola em um ecossistema de águas abertas, e como mudou essa paisagem com a colonização espanhola durante a segunda metade do século XVI. Apoiados nos conceitos e elementos teóricos da Arqueologia da Paisagem e da Ecologia Histórica, e nos dados arqueológicos, paleo-ambientais, documentais e na fotointerpretação, desenvolvemos uma análise que permitiu estabelecer que o sistema de camellones foi o resultado da inter-relação homem-meio em que os homens criaram uma forma de viver em um meio alagadiço e com grandes áreas de pântano permanente, construindo longos canais para controlar a água, criando áreas de mitigação das enchentes, obstruindo a confluência de alguns rios e elevando os campos para cultivo. A água, longe de ser um problema, se transformou no eixo de um sistema que não só provia alimentos mas também recursos derivados da pesca e da caça. Esta paisagem mudou drasticamente com a colonização espanhola, já que ela transformou o sistema social e produtivo dos Muiscas, o qual sustentava o sistema hidráulico. A mudança na forma de posse da terra, no tipo de plantas cultivadas, na introdução de elementos completamente alheios como o gado, somado à queda populacional, ao rompimento dos laços comunitários tradicionais, enfim, o desabamento do mundo que até então tinham conhecido, dificultou a reprodução social das estruturas necessárias para que o sistema hidráulico sobrevivesse. / The Hydraulic System of Raised Fields Cultivation, Camellones, built throughout 2500 years by pre-Hispanic groups from the Sabana de Bogotá, Colombia, is the central theme of this thesis. Our work focused the relationship between these groups and the water, to determine how the interaction between them led to a particular form of exploitation of resources and occupation of the territory. The overall objective of the research was to understand how it was organized the spatiality and quotidian activities, specifically during the Late Muisca period (1000 - 1550 AD), around the hydraulic system, that is, how it was built an agricultural landscape in an ecosystem of open water, and how this landscape changed with the Spanish colonization during the second half of the sixteenth century. Building on the concepts and theoretical elements of Landscape Archaeology and Historical Ecology, as well as archaeological, paleo-environmental, documentary data and photointerpretation, we developed an analysis that determined that the system of camellones was the result of the inter-relationship man-environment in which men have created a way to live in a wetland environment and with large areas of permanent swamp, building long channels to control the water, creating areas of mitigation of floods, blocking the confluence of some rivers and raising the fields for cultivation. The water, far from being a problem, has become the axis of a system that not only provided food but also the proceeds of fishing and hunting. This landscape has changed dramatically with the Spanish colonization, as it transformed the social and productive system of Muiscas, which supported the hydraulic system. The change in the form of land tenure, the type of crops, the introduction of completely unrelated elements such as cattle, added to the population decline, the breakdown of traditional community ties, ultimately, the collapse of the world that they had hitherto known, difficult the social reproduction of the structures necessary for the hydraulic system to survive.
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Água e paisagem agrícola entre os grupos pré-hispânicos da Sabana de Bogotá - Colômbia / Water and agricultural landscape among pre-Hispanic groups in Sabana de Bogotá, ColombiaDiana Lorena Rodriguez Gallo 02 June 2015 (has links)
O Sistema Hidráulico de Campos Elevados de Cultivo, Camellones, construído ao longo de 2500 anos pelos grupos pré-hispânicos da Sabana de Bogotá, Colômbia, é o tema central da presente tese. O nosso trabalho focou na relação estabelecida entre estes grupos e a água, para determinar de que maneira a interação entre ambos levou a uma forma particular de exploração dos recursos e de ocupação do território. O objetivo geral da pesquisa foi entender como foi organizada a espacialidade e as atividades cotidianas, especificamente durante o período Muisca Tardio (1000 - 1550 DC), em torno do sistema hidráulico, isto é, como se construiu uma paisagem agrícola em um ecossistema de águas abertas, e como mudou essa paisagem com a colonização espanhola durante a segunda metade do século XVI. Apoiados nos conceitos e elementos teóricos da Arqueologia da Paisagem e da Ecologia Histórica, e nos dados arqueológicos, paleo-ambientais, documentais e na fotointerpretação, desenvolvemos uma análise que permitiu estabelecer que o sistema de camellones foi o resultado da inter-relação homem-meio em que os homens criaram uma forma de viver em um meio alagadiço e com grandes áreas de pântano permanente, construindo longos canais para controlar a água, criando áreas de mitigação das enchentes, obstruindo a confluência de alguns rios e elevando os campos para cultivo. A água, longe de ser um problema, se transformou no eixo de um sistema que não só provia alimentos mas também recursos derivados da pesca e da caça. Esta paisagem mudou drasticamente com a colonização espanhola, já que ela transformou o sistema social e produtivo dos Muiscas, o qual sustentava o sistema hidráulico. A mudança na forma de posse da terra, no tipo de plantas cultivadas, na introdução de elementos completamente alheios como o gado, somado à queda populacional, ao rompimento dos laços comunitários tradicionais, enfim, o desabamento do mundo que até então tinham conhecido, dificultou a reprodução social das estruturas necessárias para que o sistema hidráulico sobrevivesse. / The Hydraulic System of Raised Fields Cultivation, Camellones, built throughout 2500 years by pre-Hispanic groups from the Sabana de Bogotá, Colombia, is the central theme of this thesis. Our work focused the relationship between these groups and the water, to determine how the interaction between them led to a particular form of exploitation of resources and occupation of the territory. The overall objective of the research was to understand how it was organized the spatiality and quotidian activities, specifically during the Late Muisca period (1000 - 1550 AD), around the hydraulic system, that is, how it was built an agricultural landscape in an ecosystem of open water, and how this landscape changed with the Spanish colonization during the second half of the sixteenth century. Building on the concepts and theoretical elements of Landscape Archaeology and Historical Ecology, as well as archaeological, paleo-environmental, documentary data and photointerpretation, we developed an analysis that determined that the system of camellones was the result of the inter-relationship man-environment in which men have created a way to live in a wetland environment and with large areas of permanent swamp, building long channels to control the water, creating areas of mitigation of floods, blocking the confluence of some rivers and raising the fields for cultivation. The water, far from being a problem, has become the axis of a system that not only provided food but also the proceeds of fishing and hunting. This landscape has changed dramatically with the Spanish colonization, as it transformed the social and productive system of Muiscas, which supported the hydraulic system. The change in the form of land tenure, the type of crops, the introduction of completely unrelated elements such as cattle, added to the population decline, the breakdown of traditional community ties, ultimately, the collapse of the world that they had hitherto known, difficult the social reproduction of the structures necessary for the hydraulic system to survive.
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