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Ecología de la altiplanicie de la Gran Sabana (Guayana Venezolana) : Estructura, diversidad, crecimiento y adaptación en bosques de las subcuencas de los ríos Yuruaní y Alto Kukenán / editado por Lionel Hernández

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    ABSTRACT: This paper shows a Holocene paleoecological reconstruction based on a peat bog sequence (El Paují, 4°28′N–61°35′W, 865 m elevation) located in the transition zone between the Gran Sabana (SE Venezuela) savannas and the Amazon rainforests. Paleoecological trends are based on the analysis of pollen and pteridophyte spores, algal and animal remains, fungal spores, and charcoal particles. The whole record embraces the last ca. 8000 cal yr BP, and was subdivided into five pollen zones, representing the following vegetation succession: savanna/rainforest mosaic (8250–7715 yr BP), dense rainforests (7715–5040 yr BP), savanna/rainforest mosaic (5040–2690 yr BP), secondary dry forests (2690–1440 yr BP), and peat bog in an open savanna landscape (1440 yr BP–present). These vegetation changes have been attributed to the action of climate and/or land use changes, as well as the corresponding synergies between them. Fire has been determinant in the landscape evolution. Based on the reconstructed fire and vegetation shifts, a changing land use pattern could have been recognized. Between the early and the mid Holocene (ca. 8.3–5.0 kyr BP), land use practices seem to have been more linked to shifting agriculture in a rainforest landscape – as is usual in Amazon cultures – with medium fire incidence affecting only local forest spots or surrounding savannas. More extensive forest burning was recorded between ca. 5.0 and 2.7 kyr BP, followed by land abandonment and the dominance of drier climates between 2.7 and 1.4 yr BP. The modern indigenous culture, which prefers open environments and makes extensive use of fire thus preventing forest re-expansion, seem to have established during the last 1500 yr. Therefore, a significant cultural replacement has been proposed for the region, leading to the present-day situation. Changing human activities have been instrumental for ecological evolution in this savanna–rainforest transitional region, as well as for the shaping of modern landscapes.Highlights►We reconstruct Holocene vegetation changes in a neotropical forest–savanna ecotone. ►Shifts in climate, human land-use and fires have been the main drivers of change. ►Amazon-style rainforest shifting agriculture prevailed between 8000 and 5000 yr ago. ►The site was abandoned and occupied by secondary forests from 2700 until 1400 yr ago. ►Modern savanna indigenous cultures established during the last millennia.
    Palaeogeography Palaeoclimatology Palaeoecology 10/2011; 310(3-4):413-426. DOI:10.1016/j.palaeo.2011.08.002 · 2.75 Impact Factor
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    ABSTRACT: Re-significando el fuego: gobernabilidad reflexiva y transformación de conflictos en territorios indígenas culturalmente frágiles A pesar de que hoy día existe una mayor aceptación del uso del fuego en ecosistemas de bosques y sabanas por parte de pueblos indígena que la que había hace dos décadas, esta sigue siendo una práctica local altamente controversial y cuestionada, al punto de que la reducción de las emisiones del efecto invernadero proveniente de las quemas en bosques y sabanas es un tema central de la agenda del Cambio Global. El tema del uso del fuego está dominado por valores, intereses y puntos de vista conflictivos que no facilitan para nada la tarea de lograr acuerdos sobre su uso sustentable. De acuerdo con la teoría de la gobernabilidad reflexiva, para avanzar en esta dirección se hace necesario desarrollar enfoques más plurales respecto al manejo del fuego mediante la creación de oportunidades de deliberaciones públicas sobre el fuego y su impacto, conjuntamente con el cambio de prácticas institucionales profundamente arraigadas que excluyen los sistemas de conocimiento local. Sin embargo, ¿estamos claros sobre los desafíos que supone esto en la práctica, particularmente en el contexto de un intenso cambio cultural a nivel comunitario, cada vez más común en lugares como Latinoamérica? En este contexto, ¿cómo llegamos al punto de crear 'redes de conocimiento' que puedan hacer frente a las narrativas dominantes sobre el fuego y a las relaciones de poder que dan origen a estos conflictos? Al fusionar el marco conceptual de STEPS sobre la gobernabilidad reflexiva con la teoría de la transformación del conflicto desarrollada por los estudios para la paz, demostramos que la cultura, y particularmente, el compromiso para con la diferencia cultural a nivel comunitario, juega un papel importante para la apertura de arenas rígidas de gobernabilidad ambiental, a fin de permitir la reflexión sobre temas ambientales altamente polémicos. Hacemos esto analizando tres proyectos de investigación participativa ejecutados en el Parque Nacional Canaima en Venezuela, que han contribuido a que el pueblo indígena Pemón haya comenzado a aclarar sus puntos de vista conflictivos sobre el fuego a través de reflexiones críticas comunitarias sobre procesos de cambio cultural y formación de identidad. Sobre los autores:
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    ABSTRACT: The southern Gran Sabana (SE Venezuela) holds a particular type of neotropical savanna characterized by the local occurrence of morichales (Mauritia palm swamps), in a climate apparently more suitable for rain forests. We present a paleoecological analysis of the last millennia of Lake Chonita (4°39′N–61°0′W, 884 m elevation), based on biological and physico-chemical proxies. Savannas dominated the region during the last millennia, but a significant vegetation replacement occurred in recent times. The site was covered by a treeless savanna with nearby rainforests from 3640 to 2180 cal yr BP. Water levels were higher than today until about 2800 cal yr BP. Forests retreated since about 2180 cal yr BP onwards, likely influenced by a higher fire incidence that facilitated a dramatic expansion of morichales. The simultaneous appearance of charcoal particles and Mauritia pollen around 2000 cal yr BP supports the potential pyrophilous nature of this palm and the importance of fire for its recent expansion. The whole picture suggests human settlements similar to today – in which fire is an essential element – since around 2000 yr ago. Therefore, present-day southern Gran Sabana landscapes seem to have been the result of the synergy between biogeographical, climatic and anthropogenic factors, mostly fire.
    Quaternary Research 11/2011; 76(3):335-344. DOI:10.1016/j.yqres.2011.06.014 · 2.58 Impact Factor