Tropical Savanna Vegetation of the Llanos of Colombia

Abstract

The Llanos Orientales of Colombia are between 3° and 7° lat N, extending as a level plain between 600 and 200 m above sea level, east of the Andes Mountains. The hot tropical climate shows a seasonal pattern of rainfall, divided between one rainy season and one dry season. In the survey of a 45,000—square—mile study area within this llanos region, 10 savanna types were recognized and classified on a floristic basis. Three of these types were floristically distinct, but with the homologous factor of all having relict forests. The other seven savanna types intergraded along a gradient of increasing humidity, and for convenience were divided into dry, humid, and inundable savannas. A great number of species were shared by these last seven types, their distinction being based on the relative dominance of species in the different types. The various theories on the origins of tropical savanna are discussed in the light of this new information on vegetation and that found in a concurrent soil survey. No single factor is believed responsible for savanna formation, but deflection from forest development is considered the result of several adverse factors, with savanna formation accelerated once the process has started.

Application of GIS and logistic regression to fossil pollen data in modelling present and past spatial distribution of the Colombian savanna

“…To consider the possibility that these interpolations overestimated the precipitation values, the precipitation maps of the Geographic Institute Agustin Codazzi (IGAC) were consulted. Focusing on high precipitation areas in the Colombian savanna, similar high rates were found in the corresponding region with values ranging from 4,000 to 5,000 mm per year (IGAC 2002) and as early as 1967, Blydenstein observed that in the Llanos Orientales ''total annual rainfall ranged between 1,700 and 2,000 mm, increasing sharply near the base of the mountains to over 4,000 mm at Villavicencio'' (Blydenstein 1967). It is therefore possible that in this region with steep precipitation gradients and few meteorological stations, the high precipitation rates at Villavicencio have been extrapolated over a region that is too large in area.…”

“…At the same time, the length of the dry season increases from 2 to 5 months (San José et al 1998). The small annual temperature amplitude of <3°C contrasts with the daily variation of 10-15°C (Blydenstein 1967).…”

“…They lie in the Orinoco Basin and cover approximately 500,000 km 2 (Sarmiento 1983). This area of low lying savannas forms a level plain between 200 and 600 m altitude (Blydenstein 1967). Most of this area is covered with grass, with ribbons of gallery forests along the creeks and rivers, and patches of forest scattered on the plains.…”

Efecto de la estructura del cultivo de palma de aceite Elaeis guineensis (Arecaceae) sobre la diversidad de aves en un paisaje de la Orinoquía colombiana

“…(Correa, Ruiz & Arévalo, 2005). Las formaciones vegetales más representativas son bosques de estrato arbóreo con elementos de 18 y 30 m de altura, herbazales con elementos leñosos, pastizales con resto de bosque, pastizales con elementos de 20 cm de altura donde domina Paspalum carinatum y palmares con predominio de Socratea exorrhiza e Iriartea deltoidea (Blydenstein, 1967;. Este tipo de vegetación se ha modificado desde el siglo XX por la actividad ganadera y por el establecimiento y consolidación de la agricultura comercial basada en cultivos de palma de aceite, arroz, maíz, sorgo, soya, frutales, entre otros (Rippstein, Escobar & Motta, 2001;Mora Fernández, Castellanos, Cardona, Pinzón & Vargas, 2011).…”

“…La siembra de palma de aceite a escala industrial, ha generado impactos negativos en diversos componentes de la biodiversidad (Aratrakorn, Thunhikorn & Donald, 2006;Fitzherbert et al, 2008;Edwards et. al., 2010;García-Ulloa, Sloan, Pacheco, Ghazoul & Pin Koh, 2012), a través de la degradación de hábitat, destrucción y reemplazamiento de la vegetación nativa, que en el caso de la Orinoquía afecta a bosques húmedos, bosques secos, bosques de galería, pastizales y humedales (Blydenstein, 1967;Bolwing, Pomeroy, Tushabe & Mushabe, 2006;Pinzón, Pardi, Trejos & Midori, 2009), lo que genera cambios en la composición y estructura de la vegetación (Correa & Stevenson, 2010).…”