Inluded here is the Llanos lowland region extending through northern Colombia and western Venezuela. It also extends along the coastal zone of Venezuela from the Paraguana Peninsula west to the start of the Amacuro Delta and incorporates the middle reaches of the Orinoco River.

The most extensive forests on the Llanos extend along the eastern piedmont of the Andean Cordillera, which in places is up to 80 km wide. A feature here is the continuous input of groundwater and nutrients from the adjacent slopes and a number of areas are subject to seasonal flooding. These forests can be subdivided into several different types. The most prevalent type, found on the drier alluvial plains, is a medium tall (25-30 m), semi deciduous forest dominated by Banara guianensis, Brosimum alicastrum, Brownea macrophylla, Chrysophyllum argenteum subsp. auratum, Croton gossypiifolius, Lonchocarpus hedyosmus and Pachira quinata. But possibly one of the most interesting is the largely evergreen forest of the San Camilo Reserve in western Apure State. This forms part of the so-called San Camillo forest refuge centre (of Steyermark) for endemic and/or relict species. Endemic species including Aegiphila scandens (Verbenaceae), Forsteronia apurensis (Apocynaceae), Inga thibaudiana (Fabaceae), Machaerium paraense (Fabaceae), Miconia matthaei (Melastomataceae), Odontocarpa steyermarkii (family?), Ormosia nobilis (Fabaceae), Ouratea apurensis, O. pseudomarahuacensis (Ochnaceae), Pterocarpus santalinoides (Fabaceae) and Simaba paraensis (Simarubaceae). Also present are various Amazonian and Guayanan floristic elements reflecting the former close link with these biomes in the recent past. These include Caraipa punctata, Guatteria cardoniana, Licania latifolia, Pouteria bangii and Roucheria columbiana.  Another interesting, disjunct element found here is Myrocarpus venezuelanum (Fabaceae). Other members of this genus are found in Argentina, Paraguay and southern Brazil. This is thought to be evidence of a former connection between the Brazilian and Guayanan shields which was disrupted during an arid phases of the Pleistocene.

 

References

Anon. 1996. Habitats of South America. Institute of Terrestrial Ecology and Intitut Royal Des Sciences Naturelles De Belgique.

Berroterán, J. L. 1998. Spatial representation, biodiversity, and fragmentation of vegetation communities of the central high llanos of Venuzuela. In: Forest Biodiversity Research, Monitoring and Modeling. Eds. F. Dallmeier and J. A. Comiskey. Man and the Biosphere Series, Volume 40. The Parthenon Publishing Group.

Berroterán, J. L., Ramos, S., Oropeza, E., Rosales, A. & Piccoli, V. 1998. Relationships between floristic composition, physiognomy, biodiversity and soils of the ecological systems of the central high Llanos of Venezuela. In: Forest biodiversity in North, Central and South America and the Caribbean. Eds. F. Dallmeier and J. A. Comiskey. Man and the Biosphere Series, Vol. 21. The Parthenon Publishing Group.

Daly, D. C. & Mitchell, J. D. 2000. Lowland vegetation of tropical South America – an overview. In: Imperfect Balance: Landscape Transformations in the pre-Columbian Americas. Ed. D. Lentz. Columbia University Press, New York.

Leith, H. & Werger, M. J. A. 1989. Ecosystems of the World 14B - Tropical Rain Forests. Elsevier Scientific Publishing Company.

Myers, J. G. 1933. Notes on the vegetation of the Venezuelan Llanos. Journal of Ecology, 21: 335-349.

Prance, G. T. 1982. Forest Refuges: Evidence from Woody Angiosperms. In: Biological Diversity in the Tropic. Ed. G. T. Prance. Columbia University Press.

Stergios, B., Comiskey, J. A., Dallmeier, F. Licata, A. & Nino, M. 1998. Species diversity, spatial distribution and structural aspects of semi-deciduous lowland gallery forests in the western Llanos of Venezuela. In: Forest biodiversity in North, Central and South America and the Caribbean. Eds. F. Dallmeier and J. A. Comiskey. Man and the Biosphere Series, Vol. 21. The Parthenon Publishing Group.

Steyermark, J. A. 1979. Plant refuge and dispersal centres in Venezuela: their relict and endemic elements. In: Tropical Botany. Eds. K. Larsen and L. B. Holm-Nielsen. Academic Press.