Abstract
The Gran Sabana region (SE Venezuela) is characterized by extensive neotropical savannas, in a warm and wet climate, apparently more suitable for the existence of rain forests. Two main types of hypotheses have been proposed to explain this situation: natural factors, such as climate changes or soil poverty, and burning by humans. This study analyzes the pollen and charcoal content of a 7,500 years old peat bog, at the shore of Laguna Encantada. The savanna landscape has dominated the area during the whole interval, but local fi res did not appear until around 1,200 years ago, when the present communities began to establish. An expansion of gallery forests, likely due to a climatic shift, has been recorded around 4,000 years ago, followed by a deforestation triggered by fire, leading to present-day situation. These results, together with former similar studies, suggest that the present Gran Sabana landscape resulted from the interaction of diverse factors, being climate changes more related to its origin and human induced fires more linked to the recent expansion.
Highlights
El estudio de restos biológicos, como indicadores de situaciones pasadas en sedimentos lacustres, turberas, etc., ha despertado un creciente interés desde la segunda mitad del siglo pasado (Birks & Birks, 1980)
Muchos de estos estudios paleoecológicos están basados en análisis palinológicos
Otro de los indicadores frecuentemente utilizados en paleoecología son los microcarbones
Summary
La Gran Sabana es una extensa región de unos 18.000 km situada al SE de Venezuela (4,6089– 6,6331 N y 61,0679–74,0478 W, Fig. 1), aunque las sabanas continúan más allá de estas fronteras, penetrando en Guyana y Brasil, con una extensión total de aproximadamente 30.000 km. Esta región se extiende entre los 750 y 1.450 m de altitud, con un gradiente descendente de N a S. Desde el punto de vista fisiográfico, forma parte de las llamadas “tierras medias” o uplands que, en la región de Guayana, se sitúan entre 500 y 1.500 m de altitud (Huber, 1995a). Desde el punto de vista geológico, la GS se encuentra enteramente sobre el sector nororiental del Escudo de Guayana, uno de los núcleos terrestres más antiguos del continente americano. 2) Sabanas con morichales, estacionalmente inundadas, donde se forma un denso estrato herbáceo de hasta 2 m de alto con parches más o menos dispersos de morichales. El estrato herbáceo aparece disperso e irregular, y dominan taxones de la familia Cyperaceae
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